Chromatographic Purification of Neutron Capture Molybdenum-99 from Cross-Contaminant Radionuclides

Chromatographic Purification of Neutron Capture Molybdenum-99 from Cross-contaminant Radionuclides

PRESENTED BY

MAHMOUD AMIN MAHMOUD MOSTAFA (M.Sc. Environmental Science, 2003) Radioactive Isotopes and Generators Dept. Hot Labs. Center, Atomic Energy Authority

A thesis Submitted In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Science Inorganic, Physical and Analytical Chemistry

2011

Chromatographic Purification of Neutron Capture Molybdenum-99 from Cross-contaminant Radionuclides

PRESENTED BY

MAHMOUD AMIN MAHMOUD MOSTAFA

Under Supervision of

Prof. Dr. Abd El-Fattah Bastawy Farag Prof. Dr. Mohamed Abd El-Salam El-Absy Prof. of Inorganic and Analytical Chemistry, Prof. of Inorganic and Radiochemistry, Radioactive Faculty of Science Helwan Univeristy. Isotopes and Generators Dept., Hot Labs Center, Atomic Energy Authority.

Prof. Assist. Dr. Mahmoud Abu El-Enein El-Amir Dr. Omnia Ibrahim Mohamed Prof. Assist. of Radiochemical Engineering, Head Lecturer of Analytical Chemistry, Chemistry Dept, of Radioactive Isotopes and Generators Dept. Hot Faculty of Science, Helwan University. Labs Center, Atomic Energy Authority

Department of Chemistry Faculty of Science Helwan University

2011

ACKNOWLEDGEMRNT

Before all and above, I thank and pray to ALLAH for unlimited help and uncounted reasons. I greatly indebted to Prof. Dr. Abd El Fattah Bastawy Farag, Prof of Inorganic and Analytical Chemistry, Faculty of Science, Helwan University, for his fruitful discussion, effective participation and deep concern of this work. My deep appreciation and sincere thanks to Prof. Dr. Mohamed Abd El- Salam El-Absy, Prof of Inorganic and Radiochemistry, Radioactive Isotopes and Generators Dept., Hot Labs Center, Atomic Energy Authority, for suggesting the topic of this Thesis, planning of experimental work, continuous following and enormous time spent in careful revision. I would like to thank Prof. Assist. Dr. Mahmoud Abu El-Enein El- Amir, Head of Radioactive Isotopes and Generators Dept. for his continuous scientific advice. I am thankful to Dr. Omnia Ibrahim Mohamed, Lecturer of Analytical Chemistry, Faculty of Science, Helwan University. I would greatly thank Prof. Assist. Dr. Mohamed Mostafa Abd El- Hamid, Radioactive Isotopes and Generators Dept., Prof. Dr. Ahmed Abd El-Moaty, the former Head of Radioactive Isotopes and Generators Dept. and Prof. Assist. Dr. Mohamed Abd El-Motaleb, Labeled Compounds Dept. for their advices and help. My profoundly thanks and deep appreciation to Prof. Dr. Tharwat Siam, Head of Radioactive Isotopes and Sealed Sources Division for his careful support. My thanks to all stuff members and colleagues of Radioactive Isotopes and Generators Dept. for their help in different directions. Finally, I cannot forget complete assistance and encouragement of my family during the preparation of this work.

CONTENTS

List of Tables i List of figures iii Abstract x Aim of work xii

CHAPTER I INTRODUCTION

Page 1.1. Preface ………………………………………………………………………… 1

1.2. Molybdenum ….. . . . ………………………………………………………….. 3 1.2.1. Chemistry and radiochemistry of molybdenum………………………… 3 1.2.2. Production of molybdenum-99……………………………………………… 6 1.2.3. Activation molybdenum-99 cross-contaminant radionuclides…………… 7 1.2.3.1. Fast neutrons……………………………………………………… 7 1.2.3.2. Thermal neutrons…………………………………………………… 8 1.2.4. 99Mo / 99mTc radioisotope generators………………………………… 9 1.2.4.1. Chromatographic column generators based on 99Mo molybdate (VI) gels.. 11

1.3. Iron……………………………………………………………………………… 13 1.3.1. Chemistry and radiochemistry of iron……………………………… 13 1.3.2. Transformations of iron oxyhydroxides and oxides…………………… 17 1.3.2.1. Transformations by catalytic action of Fe(II) 17 1.3.2.2. Transformation of Lepidocrocite to magnetite Fe3O4……………………. 19 1.3.2.3. Transformation of Fe(OH)2 to Goethite…………………………… 19 1.3.2.4. Transformation of lepidocrocite to goethite………………………… 20 1.3.2.5. Transformation of magnetite to goethite under alkaline pH……… 20

1.4. Chemistry of aluminum…………………………………………………… 21

1.5. Ferrocyanides as fixed column bed……………………………………… 22

1.6. Separation and purification of activation molybdenum-99…………………. 24 1.6.1. Precipitation methods………………………………………………… 25 1.6.2. Ion exchange methods………………………………………………… 27 1.6.3. Literature survey on separation and purification methods of molybdenum.. 28 1.6.3.1. Oxides and oxyhydroxides of iron (III)…………………………… 29 1.6.3.2. Al(OH)3………………………………………………………………. 33 1.6.3.3. Ferrocyanides…………………………………………………… 34

i CHAPTER II EXPERIMENTAL

2.1. Chemicals and solutions……………………………………………… 37 2.1.1. Chemicals………………………………………………… 37 2.1.2. Solutions…………………………………………………………… 37

2.2. Equipments……………………………………………………………… 38

2.3. Identification of the contaminants……………………………………… 39 2.3.1. Chemical analysis…………………………………………………… 39 2.3.2. Radiometeric analysis…………………………………………… 39 2.3.2.1. Molybdenum trioxide...... 39 2.3.2.2. Aluminum metal…………………………………………………… 40

2.4. Preparation of the MoO3 / Al radiotracer solutions…………………… 40 2.4.1. MoO3 / Al targets dissolution……………………………………… 41 2.4.2. Nitric acid titration………………………………………………… 41

2.5. Purification via in-situ precipitation of Fe(III) minerals…………… 41 2.5.1. In-situ precipitation of Fe (III) iron from the Al wrapper……………… 41 2.5.2. Factors affecting the purification process……………………………… 42 2.5.2.1. Total amount of fed iron ……………………………………….... …. 42 2.5.2.2. Effect of filtration……………………………………………… 43 2.5.2.3. Concentration of NaOH in solution………………………………… 43 2.5.2.4. Concentration of H2O2………………………………………………………………… 44 2.5.3. Assessment of the purification process……………………………… 44 2.5.4. Recovery of the retained 99Mo-molybdate anions……………………… 45 2.5.4.1. Effect of total iron dose…………………………………………… 46 2.5.4.2. Effect of eluent………………………………………………… 47 2.5.5. Identification of Fe (III) minerals by Raman spectroscopy…………… 47 2.5.5.1. Effect of total iron dose…………………………………………… 48 2.5.5.2. Effect of NaOH concentration…………………………………… 48 2.5.5.3. Effect of H2O2 concentration…………………………………… 49

2.6. Purification via in-situ precipitation of Al(OH)3 matrices………………….. 49 2.6.1. Precipitation at pH value of 9.5……………………………………… 49 2.6.1.1. Recovery of the sorbed molybdate (VI)…………………………… 50 2.6.1.2. Assessment of the purification process………………………… 50 2.6.2. Precipitation at pH value of 5…………………………………………. 51 2.6.2.1. Recovery of the sorbed molybdate (VI)……………………………. 52 2.6.2.1.1. Washing with 3.5 M NaNO3 solution of pH value 5………… 52 2.6.2.1.2. Washing with 3.5 M NaNO3 solution of pH value 9.5………… 52 2.6.2.2. Assessment of the purification process………………………… 52

ii 2.7. Purification onto potassium nickel hexacyanoferrate……………………. 53 2.7.1. 99Mo-molybdate feeding solutions…………………….…………… 53 2.7.2. Preparation and characterization of the KNHCF (II) matrix………….. 53 2.7.2.1. Preparation of the KNHCF (II) matrix 53 2.7.2.2. Characterization of the KNHCF (II) matrix 54 2.7.2.2.1. Thermal analysis…………………….……………………. 54 2.7.2.2.2. X-ray diffraction pattern…………………….……………… 54 2.7.2.2.3. X-ray florescence…………………….……………………. 54 2.7.2.2.4. Infrared spectra…………………….……………………. 54 2.7.2.2.5. Solubility…………………….……………………. 55 2.7.3. Chromatographic column operations…………………….……………… 55 2.7.4. Recovery of the sorbed molybdate…………………….……………… 55 2.7.5. Radiometric analysis…………………….………………………… 56

2.8. Preparation of 99Mo / 99mTc generator…………………….……………… 56 2.8.1. Preparation of zirconium 99Mo-molybdate gel matrix……………………. 56 2.8.2. Characterization of zirconium 99Mo-molybdate gel matrix…………… 57 2.8.2.1. Thermal analysis…………………….……………………. 57 2.8.2.2. X-ray diffraction pattern…………………….……………………. 57 2.8.3. Preparation of 99Mo / 99mTc generator….…………………….….……… 57 2.8.3.1 Preparation of highly pure 99Mo-molybdate (VI) solute….………… 57 2.8.3.2. Operation of chromatographic column….……………………. 58 2.8.4. Quality control of 99Mo / 99mTc generator….……………………. 58 2.8.4.1. 99mTc Elution curve and yield….…………………….….……… 58 2.8.4.2. Radionuclidic purity….…………………….….………….. 59 2.8.4.3. Radiochemical purity….…………………….….…………… 59 2.8.4.4. Chemical purity: ….…………………….….……………………. 60 2.8.4.4.1. Determination of molybdenum….…………………….….… 60 2.8.4.4.2. Determination of zirconium….………………………….. 60 2.8.4.4.3. Determination of pH value….…………………………. 60 2.8.5. Reproducibility of the 99mTc elution performance….……………… 60

CHAPRET III RESULTS AND DISCUSSION

3.1. Activation molybdenum-99 cross-contaminant radionuclides……………. 61

3.2. Targets preparation and irradiation…………………………………… 64 3.2.1. Choice of Al as a wrapper for the MoO3 targets:……………………… 64 3.2.2. Identification of cross-contaminant radionuclides…………………… 66 3.2.2.1. Molybdenum trioxide…………………………………………… 66 3.2.2.2. Aluminum wrapper………………………………… 72 3.2.3. Sources of contaminant radionuclides………………………… 74

iii 3.3. Preparation of the 99Mo-molybdate radiotracer solutions (targets dissolution) … ……………………………………………… 78

3.4. Purification of the 99Mo-molybdate (VI) solute via in-situ precipitation of 59Fe-Fe (III) minerals…………………………………………… 82 3.4.1. Factors affecting 59Fe elimination………………………………… 88 3.4.1.1. Total amount of fed iron…………………………………………….. 92 3.4.1.2. Filtration process…………………………………………………….. 96 3.4.1.3. Concentration of H2O2…………………………………………… 98 3.4.1.4. Concentration of NaOH………………………………………… 102 3.4.2. Elimination assessment of 59Fe radionuclide………………………… 105 3.4.2.1. Contribution of 59Fe in the formed Fe(III) minerals and 99Mo- molybdate solutes ……………………………………….. 105 3.4.2.2. Raman spectroscopy of Fe (III) minerals…………………… 115 3.4 .2.2.1. Effect of total Fe dose…………………………………… 116 3.4.2.2.2. Effect of NaOH concentration…………………………… 121 3.4.2.2.3 Effect of H2O2 concentration……………………… 122 3.4.3. Adsorption behavior of 99Mo-molybdate (VI) anions……………… 124 3.4.3.1. Retention of 99Mo-molybdate (VI) anions……………………… 124 3.4.3.1.1. Effect of total iron dose 125 3.4.3.1.2. Effect of NaOH concentration………………………… 128 3.4.3.1.3 Effect of H2O2 concentration……………………………. 131 3.4.3.2. Desorption of 99Mo-molybdate (VI) anions…………………… 134 3.4.3.2.1. Factors affecting desorption of 99Mo-molybdate (VI) anions 137 3.4.3.2.1.1. Effect of the initial amount of iron…………………… 137 3.4.3.2.1.2. Effect of eluent…………………………………… 140 3.4.3.2.2. Adsorption reactions mechanism………………… 140 3.4.4. Purification assessment from cross-contaminant radionuclides…… 144 3.4.4.1. The lanthanides and 92mNb radionuclides……………………… 146 3.4.4.2. 95Zr / 95Nb and 175&181Hf radionuclides………………………… 149 3.4.4.3. 54Mn, 51Cr and 124Sb radionuclides…………………………… 154 3.4.4.4. 59Fe, 60Co, 65Zn and 46Sc radionuclides………………………… 162 3.4.4.5. Radionuclides of the alkali metals 134Cs, 86Rb and 24Na ……… 169

3.5. Successive purification of the 99Mo-molybdat (VI) supernatant via in-situ precipitation of aluminum hydroxide at pH values of 9.5 and 5……… 172 3.5.1. In situ precipitation of Al (OH)3 matrix at pH 9.5……………………… 172 3.5.1.1. Sorption / desorption of 99Mo-molybdate (VI) anions…………… 174 3.5.1.1.1. Sorption behavior…………………………………… 174 3.5.1.1.2. Desorption behavior…………………………………… 174 3.5.1.1.3. 99Mo-molybdate (VI) uptake and mechanism………………… 177 3.5.1.2. Purification assessment………………………………………….. 182 3.5.1.2.1 Iron-59…………………………………………… 186 3.5.1.2.2. Zinc-65………………………………………………….. 186 3.5.1.2.3. Antimony-124……………………………………………. 187 3.5.1.2.4. Chromium-51………………………………………… 187

iv 3.5.1.2.5. Cobalt- 60……………………………………………… 188 3.5.1.2.6. Scandium-46……………………………………….. 188 3.5.1.2.7. Zirconium-95 and hafmium-181 and 175……………………… 189 3.5.1.2.8. Niobium-95……………………… 189 3.5.2. In-situ precipitation of Al(OH)3 matrix at pH 5 190 3.5.2.1. Adsorption / desorption of 99Mo-molybdate (VI) anions……… 191 3.5.2.1.1. Adsorption behavior……………………………………… 191 3.5.2.1.2. Desorption behavior……………………………………… 193 3.5.2.1.3. 99Mo-molybdate uptake and mechanism……………………… 194 3.5.2.2. Purification assessment………………………………………… 201

3.6. Chromatographic purification of the final 99Mo-molybdate (VI) supernatant onto KNHCF (II) matrix………………………………… 205 3.6.1. Preparation and characterization of potassium nickel hexacyanoferrate: 205 3.6.1.1. Solubility of KNHCF (II) matrix…………………………………… 206 3.6.1.2. Thermogravimetric analysis of KNHCF(II) matrix……………… 206 3.6.1.3. Infrared analysis of KNHCF (II) matrix ……………………… 207 3.6.2. 99Mo-molybdate(VI) feeding solutions……………………… 209 3.6.3. Chromatographic column operations……………………… 211 3.6.3.1. Effect of Mo(VI) concentration……………………………… 211 3.6.3.2. Assessment of the purification potential of KNHCF(II) matrix…… 219 3.6.3.3. Effect of flow rate of the 99Mo-molybdate (VI) solute……… 223 3.7. 99Mo / 99mTc generator------225 3.7.1. Preparation and characterization of inactive zirconium molybdate gel-- 225 3.7.1.1. Preparation of zirconium molybdate gel------225 3.7. 1.2. Characterization of the zirconium molybdate gel ------227 3.7. 1.2. 1. Thermal analysis of ZrMo matrix------227 3.7. 1.2.2. XRD analysis of ZrMo matrix------229 3.7.2. Preparation of 99Mo/ 99mTc generator based on zirconium 99Mo- molybdate gel matrix…………………………………………………… 229 3.7.3. Elution performance and Quality control indices 232 3.7.3.1. Elution profile and elution yield of 99mTc 232 3.7.3.2. Radionuclidic purity of the 99mTc eluates 235 3.7.3.3. Radiochemical purity 239 3.7.3.4. Chemical purity 239 3.7.3.5. pH determination 241

Summary 243

References 250

LIST OF TABLES

Page Table (1.1): Radionuclides of molybdenum and their nuclear characteristics………… 5

Table (3.1): Calculated specific activity in mCi / g Mo irradiated in the Egyptian Second Research Reactor (ETRR-2) at a neutron flux of ~ 1 x 1014 n /cm2 s for different time intervals………………………………………. 61

Table (3.2): Variation of the specific activity of 99Mo with the neutron fluxes and irradiation time…………………………………………………………… 63

Table (3.3): Radionuclides detected and identified in the MoO3 target and its Al wrapper together with some of their nuclear data characteristics………… 67

Table (3.4): Temperature gradient during dissolution of 1.0 g MoO3 wrapped in 0.6 g Al foil targets containing variable Fe amounts with 34 ml 5M NaOH solution at ambient laboratory conditions (~ 25 oC)……………………... 92

Table (3.5): Elimination % of 59Fe, 92mNb, 95Nb, 60Co and 51Cr radionuclides from 99Mo-molybdate (VI) supernatant with and without 45 µm Millipore filter at room temperature (~ 25 oC)……………………………………………. 96

Table (3.6): Volumes and behavior of nano-sized particles in solutions…………… 98

Table (3.7): Stability of 30 mg FeCl3.6H2O and color changes of the formed Fe (III) mineral precipitates with the concentrations of H2O2 in the system……… 99

Table (3.8): Amounts of 59Fe-iron contribution (mg) in the formed Fe(III) mineral precipitates and 34 ml aqueous phase and the corresponding elimination % of 59Fe radionuclide as a function of the initial total concentrations of Fe, NaOH and H2O2 in the system………………………………………... 107

Table (3.9): Specific surface area and particle size of Fe(III) minerals……………….. 109

Table (3.10): Ferric (III) iron transformations from 34 ml 4 M NaOH solutions containing variable total iron doses oxidized with a constant volume of 0.5 ml H2O2(10 % w/v) with (W) and without (W. O) 1.0 g MoO3…. 117

Table (3.11). Ferric (III) iron transformations from 34 ml 4 and 0.5 M NaOH solution adjusted with HNO3 acid containing constant concentrations of 7.58 mg Fe and 0.5 ml H2O2 (10 % w/v) with (W) and without (W. O) 1.0 g MoO3. 118

Table (3.12). Ferric (III) iron transformations from 34 ml 4 M NaOH solutions containing total iron doses of 7.58 mg Fe and variable volumes of 0.25, 0.5 and 1.0 ml H2O2 solution (10 % w/ v) with (W) and without (W. O) 1.0 g MoO3………………………………………………………………. 118 i

Table (3.14): Purification of 99Mo-molybdate (VI) anions via in-situ precipitation of 1.37 mg Fe dissolved in 30 ml 4 M NaOH oxidized with 0.5 ml H2O2 solution (10 % w/v), thereafter…………………………………………. 146

Table (3.15): 99Mo-molybdate (VI) purification via successive in-situ precipitations of 1.37 mg Fe from 0.6 g Al dissolved in 30 ml 4 M NaOH by oxidation with 0.5 ml H2O2 and HNO3 acid neutralization to pH 9.5, respectively……………………………………………………………... 191

99 Table (3.16). Retention % of Mo-molybdate (VI) anions onto Al(OH)3 in-situ precipitated at pH 5 before and after washing with 4x8 ml 3.5 M NaNO3 solutions of pH values 5 and 9.5……………………………….. 195

Table (3.17): Recovery % of 99Mo-molybdate (VI) anions after successive washing of the Al(OH)3 precipitates formed at pH values of 5 and 9.5 with 4×8 ml 3.5 M NaNO3 solutions of pH values 5 and /or 9.5…………………….. 196

Table (3.18). Effect of Mo(VI) concentration in NaNO3 solution on the uptake of 99Mo-molybdate(VI) anions and elimination of cross-contaminant radionuclides onto KNHCF(II) chromatographic columns………………... 214

Table (3.19): Radiocontaminants elimination from 99Mo-molybdate solute onto

successively in-situ precipitated Fe (III) minerals and Al (OH)3 precipitate and KNFCN (II) chromatographic column matrix………….. 223

Table (3.20) Elution yield and quality control data of 99mTc eluates from1g high dionuclidic pure Zr99Mo gel generator…………………………………... 241

ii LIST OF FIGURES page Figure 3.1. Gamma-ray spectrum of 0.1 g MoO3 irradiated powder at the ETRR-2 reactor and measured after three months cooling period, from the end of irradiation, for 2000 s…………………………………………………… 62

Figure 3.2. Gamma-ray spectra of 0.0144 g irradiated MoO3 powder measured after (a) 3, (b) 4 and (c) 6 days cooling periods for 100 s………………………. 68

Figure 3.3. Gamma-ray spectra of the 0.0144 g irradiated MoO3 powder measured after (a)7, (b) 13 and (c) 75 days cooling periods for 100, 1000 and 2000 s, respectively. ……………………….……………………………….. 70

Figure 3.4. Gamma-ray spectra of 0.1 g irradiated MoO3 powder measured after (a) one, (b) two and (c) three months cooling periods for 100, 300 and 2000 s, respectively. ……………………….………………………………… 71

Figure 3.5. Gamma-ray spectra of sodium molybdate solute of different volumes, cooling periods and detection time: (a) 0.2 ml, 8 days and 200 s (b)1.0 ml, one month and 200 s (c)1.0 ml, two months 300s and (d) 1.2 ml, three months and 500 s, respectively……………………….………… 73

Figure 3.6. Gamma-ray spectra of (a)1.0 ml of radioactive aluminum solute measured after a cooling period of one month for 500 s and (b) 0.6 g Irradiated aluminum foil measured after a cooling period of 20 days for 1000 s….. 75

Figure 3.7. Gamma-ray spectra of (a) 0.2 (b) 1.0 (c) 1.0 and (d) 1.2 ml of 99Mo molybdate (VI) solute measured after cooling periods of 8 days and one, two and three months for 100, 200, 300 and 2000 s, respectively……….. 85

Figure 3.8. Gamma-ray spectra of (a) 0.2 ml of the 99Mo-moloybdate (VI) solute (b) the formed Fe(III) minerals and (c) 0.2 ml of the supernatant solution measured after a cooling time of 8 days for 100 s. ………………………. 87

Figure 3.9. Gamma-ray spectra of (a)1.0 ml of the 99Mo-molybdate (VI) solute (b) the Fe(III) precipitate after washing and (c)1.0 ml of the supernatant solution measured after a cooling period of one month for100s………… 89

Figure 3.10. Gamma-ray spectra of (a) 1.0 ml of the 99Mo-molybdate(VI) solute, (b) the Fe(III) precipitate after washing, (c)1.0 ml of the supernatant solute measured after a cooling period of two months for 200s………………… 90

Figure 3.11. Gamma-ray spectra of (a ) 1.2 ml of the 99Mo-molybdate (VI) solute, (b) the Fe(III) precipitate after washing and ( c ) 1.2 ml of the supernatant solution measured after a cooling period of three months for 2000 s……. 91

Figure 3.12. Effect of total concentration of fed Fe on the elimination % of 59Fe iii radionuclide from the molybdate (VI) solute containing 0.5 ml H2O2 as oxidant. ……………………….……………………….………………… 94

Figure 3.13. Gamma-ray spectra of the supernatants of 99Mo (VI) solute at total Fe concentrations of ( a) 0.721, (b) 3.99, (c) 6.71 and (d) 7.25 x 10 -3 M Fe measured after a cooling period of 45 days for 3000 s. ……………… 95

Figure 3.14. Gamma-ray spectra of the (a) 99Mo-molybdate(VI) solute before precipitation of The Fe(III) mineral and the supernatants withdrown (b) without and (c) with 45 µm Millipore filter measured after a cooling period of 45 days for 3000 s. ……………………….………………………. 97

Figure 3.15.Gamma-ray spectra of the supernatants of 99Mo-molybdate (VI) solutes containing (a) 0.25, (b) 0.5 and (c) 1.0 ml of H2O2 solution measure after a cooling time of 45 days for 3000 s. ………………………. 100

59 Figure 3.16. Effect of H2O2 concentration on the elimination % of Fe radionuclide from the 99Mo-molybdate (VI) solutes. ………………………. 101

Figure 3.17. Gamma-ray spectra of the supernatants of 99Mo-molybdate (VI) solutes in about (a) 4, (b) 2, (c) 1 and (d) 0.5 M NaOH solution measured after 45 days from the end of irradiation for 3000 s………………………. 103

Figure 3.18. Effect of NaOH concentration on the elimination % of 59F radionuclide from the molybdate (VI) solute. 104

Figure 3.19. Contribution, mg of iron in 34 ml 4 M NaOH solution after 2 hours from addition of 0.5 ml H2O2 solution to variable Fe (II) iron concentrations (in mg) in the system at ambient atmospheric conditions. 108

Figure 3.20. Effect of H2O2 concentration on the contribution of Fe in the aqueous phase. 111

Figure 3.21: Effect of NaOH concentration on the contribution of Fe in the aqueous phase……………………….……………………….………………… 114

Figure 3.22: Gamma-ray spectra of 99Mo-molybdate (VI) supernatants in presence of (a) 0.72, (b) 3.99 and (c) 5.08, (d) 6.71, (e)7.26 and (f) 7.80 x 10-3 M Fe in solution measured after cooling time of 8 days from the end of irradiation for 200 s. ……………………….………………………. 126

Figure 3.23: Effect of total concentrations of Fe on the retention % of 99Mo-molybdate (VI) anions onto the formed Fe(III) minerals precipitates. …………… 127

Figure 3.24.Gamma-ray spectra of the 99Mo-molybdate (VI) supernatant at concentrations of (a) 4.0 (b) 2.0 (c) 1.0 and (d) 0.5 M NaOH solutions measured after 8 day from the end of irradiation for 200 s……………… 129

iv Figure 3.25. Effect of NaOH concentration on the retention of 99Mo-molybdate (VI) anions onto the formed Fe(III) minerals………………………...... 130

Figure 3.26. Gamma-ray spectra of the supernatant of 99Mo-molybdate (VI0 solute oxidized with volumes of (a) 0.25 (b) 0.5 and (c) 1.0 ml of (10 % w/v) H2O2 solution measured after cooling time of 8 days from the end of irradiation for 200 s. ……………………….………………………. 132

99 Figure 3.27. Effect of H2O2 concentration on the retention of Mo-molybdate (VI) anions onto the formed Fe (III) minerals via oxidation of 3.99 x 10-3 M Fe(II) in 34 ml 4 M NaOH solution. ……………………….…………… 133

Figure 3.28. Gamma-ray spectra of the Fe (III) mineral precipitates (a) before and after first washing (c) second washing each with 5 ml 0.5 M NaOH solution measured after a cooling period of 8 day for 100 s………….. 135

Figure 3.29. Gamma-ray spectra of 1.0 ml of the (a) first and (b) the second washing filtrate of Fe(III) precipitate measured after a cooling period of 8 days for 100 s, and (c and d) of the same filtrates measured after a cooling period of two months for 200 s. ……………………….………………………. 136

Figure 3.30 Gamma-ray spectra of the 1st and 2nd washing filtrates of the formed Fe (III) minerals of (a and b) 4.47, (c and d) 7.8 and (e and f) 11.71 mg Fe each with 5 ml 0.5 M NaOH measured after a cooling period of 8 days for 100 s. ……………………….……………………….……………… 138

Figure 3.31. Gamma-ray spectra of the 1st and 2nd washing filtrates of the formed Fe (III) minerals of 7.58 mg Fe with 2 x 5 ml distilled water measured after a cooling period of 8 days for 100 s. ……………………….……… 141

Figure 3.32. Effect of total initial concentration of iron dose on the elimination % of ■ 92mNb, ● 95Nb, ▲95Zr and▼175&181Hf from the molybdate (VI) solutes in 34 ml 4 M NaOH containing 0.5 ml H2O2. …………………………… 151

Figure 3.33. Effect of NaOH concentration on the elimination % of ■ 92mNb, ● 95Nb, ▲95Zr and▼175&181Hf from molybdate (VI) solutes containing 7.58 mg Fe and 0.5 ml H2O2 153

92m 95 Figure 3.34. Effect of H2O2 concentration on the elimination % of ■ Nb, ● Nb, ▲95Zr and ▼ 175&181Hf from molybdate (VI) solute in 34 ml 4 M NaOH solution containing 7.58 mg Fe. ……………………….……………… 155

Figure 3.35. Effect of initial total iron concentration on the elimination % of ■ 54Mn, ●51Cr and ▲124Sb from the molybdate (VI) solutes in 34 ml 4 M NaOH solutions containing 0.5 ml H2O2 (10 % w/v) ………………………. 159

Figure 3.36. Effect of NaOH concentration on the elimination % of ■ 54Mn,● 51Cr and v ▲124Sb from 34 ml molybdate (VI) solute containing 7.58 mg Fe and 0.5 ml H2O2 (10 % w/v) ……………………….……………………….. 161

54 51 Figure 3.37. Effect of H2O2 concentration on the elimination % of ■ Mn ● Cr and ▲ 124Sb from molybdate (VI) solute in 34 ml 4 M NaOH solution containing 7.58 mg Fe. ……………………….………………………. 163

Figure 3.38. Effect of total initial concentration of iron on the elimination % of ▼59Fe, O 46Sc, □ 60Co and ▲ 65Zn from the molybdate (VI) solutes in 34 ml 4 M NaOH containing 0.5 ml H2O2 (10 % w/v) …………………… 167

Figure 3.39. Effect of NaOH concentration on the elimination % of ▼59Fe, O 46Sc, □ 60Co and ▲ 65Zn from the molybdate (VI) solute containing 7.58 mg Fe and 0.5 ml H2O2 (10 % w/v) ……………………….……… 168

59 46 Figure 3.40. Effect of H2O2 concentration on the elimination % of ▼ Fe, O Sc, □ 60Co and ▲ 65Zn from the molybdate (VI) solutes in 34 ml 4M NaOH containing 7.58 mg Fe. ……………………….………………………. 170

Figure 3.41. Gamma-ray spectra of (a) 0.2 ml of the initial 99Mo-molybdate(VI) solute before precipitation of Al (OH)3, (b) the Al (OH)3 precipitate formed at pH 9.5 and (c) 0.2 ml of the final supernatant measured after cooling period of 8 days for 100 s. ……………………….………………… 175

Figure 3.42.Gamma-ray spectra of the Al(OH)3 matrix precipitated at pH 9.5 measured after the (a) 1st, (b) 2nd (c) 3rd and (d) 4th washing process each with 8 ml 3.5 M NaNO3 solution of pH 9.5 for 100 s. ………………………. 176

Figure 3.43.Gamma-ray spectra of 0.2 ml of the (a)1st, (b) 2nd,(c) 3rd and (d) 4th washing filtrates of the Al (OH)3 matrix precipitated at pH 9.5 measured for100 s. 178

Figure 3.44. Gamma- ray spectra of 1.0 ml of the ( a) 1st, ( b ) 2nd, (c) 3rd and (d) 4th washing filtrates of the Al (OH)3 matrix precipitated at pH 9.5 measured after a cooling period of three months for 200 s. ………………………………….. 179

Figure 3.45. Gamma-ray spectra of (a) 1.0 ml of the initial 99Mo-molybdate (VI) supernatant, (b) the formed Al(OH)3 matrix washed with 32 ml 3.5 M NaNO3 of pH 9.5 and (c ) 1.0 ml of the supernatant solution measured after a cooling period of one month for100 s. ………………………. 183

Figure 3.46. Gamma-ray spectra of (a) 1.0 ml of the initial 99Mo-molybdate (VI) supernatants, (b) the formed Al(OH)3 matrix washed with 32 ml 3.5 M NaNO3 of pH 9.5 and (c) 1.0 ml of the supernatant solution measured after a cooling period of two months for 200 s. ………………………. 184

Figure 3.47. Gamma-ray spectra of (a)1.2 ml of the initial 99Mo-molybdate (VI) supernatant, (b) the formed Al(OH)3 matrix washed with 32 ml 3.5 M vi NaNO3 of pH 9.5 and (c) 1.2 ml of the supernatant solution measured after a cooling period of three months for 2000 s. ………………………. 185

Figure 3.48. Gamma-ray spectra of (a) 0.2 ml of the initial 99Mo-molybdate(VI)

supernatant, (b) the formed Al (OH)3 matrix at pH 5 and (c) 0.2 ml of the remaining supernatant measured after a cooling period of 8 days for 100 s. 192

Figure 3.49. Gamma-ray spectra of 1.0 ml of the 1st, 2nd, 3rd and 4th 8 ml washing filtrates of Al(OH)3 precipitated at pH 5 with 3.5 M NaNO3 solution of pH 5 measured after cooling period of 8 days for 100 s. …………… 197

Figure 3.50. Gamma-ray spectra of 1.0 ml of the 1st , 2nd, 3rd and 4th 8 ml washing filtrates of Al(OH)3 precipitated at pH 5 with 3.5 M NaNO3 solution of pH 9.5 measured after cooling period of 8 days for 100 s…………. 198

Figure 3.51. Gamma-ray spectra of 1.0 ml of the 1st , 2nd, 3rd and 4th 8 ml washing filtrates of Al(OH)3 precipitated at pH 5 with 3.5 M NaNO3 solution of pH 5 measured after cooling period of 2 months for 300 s. ………… 199

Figure 3.52. Gamma-ray spectra of 1.0 ml of the 1st, 2nd, 3rd and 4th 8 ml washing filtrates of Al(OH)3 precipitated at pH 5 with 3.5 M NaNO3 solution of pH 9.5 measured after cooling period of 2 months for 300 s………... 200

Figure 3.53. Gamma-ray spectra of (a) typical Al(OH)3 matrices precipitated at pH 5 before washing, and after washing with 32 ml 3.5M NaNO3 solution of (b) pH 5 and (c) pH 9.5 for 300 s. ……………………………….. 202

Figure 3.54. Gamma-ray spectra of typical (a) 1.0 ml of the initial 99Mo-molybdate (VI) supernatant, the formed Al(OH)3 precipitates after washing with 32 ml 3.5 M NaNO3 solutions of (b) pH 5 (c) pH 9.5 and (d) 1.0 ml of the final supernatant of pH 5 measured after acooling period of three months for 300 s. ……………………….……………………………… 203

Figure 3.55. TGA and DTA curves of the prepared KNHCF(II matrix. ………… 207

Figure 3.56. IR spectrum of the prepared KNHCF(II) matrix. ………………………. 208

Figure 3.57. XRD pattern of the prepared KNHCF(II) matrix. ………………………. 208

Figure 3.58. Gamma-ray spectra of 99Mo-molybdate(VI) feeding solutions: (a and b) of high- and (c and d) of low- Mo(VI) content measured after cooling periods of 8 days (a and c) and 3 months (b and d). ………………… 210

Figure 3.59. Gamma-ray spectra of 99Mo-molybdate(VI) (a) feeding solution, (b) column effluent, and (c) column bed measured after a cooling period of 8 days. 212

Figure 3.60. Gamma-ray spectra of the column bed fed with 99Mo-molybdate (VI) vii solute (a) before and (b) after elution with 20 ml 3.5 M NaNO3 solution of pH9.5 and (c) the 99Mo molybdate(VI) eluate measured after a cooling period of 8 days. ……………………….………………………. 213

Figure 3.61. Gamma-ray spectra of high Mo (VI) content column after (a) 1st ,(b) 2nd, (c) rd th 3 and (d) 4 washing each with 5 ml 3.3 M NaNO3 solution measured after cooling time of 8days for 100 s. …………………………….. 215

Figure 3.62. Gamma-ray spectra of 0.2 ml of (a) 1st ,(b) 2nd ,(c) 3rd and (d ) 4th washing filtrates of the high Mo(VI) content column measured after cooling time of 8 days for 100 s. ……………………….………………………. 216

Figure 3.63. Gamma-ray spectra of low Mo(VI) content column after (a) 1st ,(b) 2nd, (c) 3rd and (d ) 4th washing process measured after cooling time of 8 days for 100 s. ……………………….……………………….…………… 217

Figure 3.64. Gamma-ray spectra of 0.2 ml of (a) 1st ,(b) 2nd ,(c) 3rd and (d ) 4th washing filtrates of the low Mo(VI) content column measured after cooling time of 8 days fo 100 s. ……………………….………………………….. 218

Figure 3.65. Gamma-ray spectra of 99Mo-molybdate(VI) (a) feeding solution, (b) column effluent, (c) 1st 5 ml eluate and (d) KNiHCF(II) matrix after elution with 20 ml 3.5 M NaNO3 solution of pH 9.5 measured after a cooling period of 3 months. ……………………….…………………………. 220

Figure 3.66. Gamma-ray spectra of: (a) 2.0 ml of the first 99Mo-molybdate (VI) feeding solution of KNHCF column (3) , ( b) KNHCF column after final washing process and (c)2.0 ml of the 99Mo-molybdate (VI) effluent at a flow rate of 5 ml / min measured after cooling periods of three months for 2000 s. 224

Figure 3.67: DTG and TGA curves of ZrMo gel matrix. ………………………. 228

Figure 3.68: X-ray diffraction pattern of ZrMo gel matrix………………………. 228

Figure 3.69 Gamma-ray spectra of (a) 1.0 ml of molybdate (VI) solute (b) 10 ml of the filtrate after precipitation of zirconium molybdate gel (c) 10 ml of the washing solution of the gel with distilled water (d) 10 ml of the washing solution of the gel with saline solution measured for 500 s….. 231

Figure 3.70. Gamma-ray spectra of (a) 0.05 g of the ZrMo gel matrix (b) ZrMo chromatographic column before 1st elution (c) ZrMo gel chromatographi column after 1st elution measured after cooling period of 12 day and (d) residual ZrMo gel detected after 3 months from the end of irradiation for 500, 200, 200 and 3000 respectively. ……………………………… 233

Figure 3.71. Typical elution profile of 99mTc from ZrMo column with 10 ml 0.9 % NaCl solution at a flow rate of 0.5 ml / mi. ………………………. 234 viii

Figure 3.72: Gamma-ray spectra of the 99mTc eluted( a ) 1st ( b) 2nd ( c ) 3rd (d) 4th (e) 5th and (f) 6th elution process measured directly for 200 s…… 236

Figure 3.73: Gamma-ray spectra of 99mTc eluted residual activity of (a) 1s (b) 2nd (c) 3rd (d) 4th (e) 5th and (f) 6th elution process measured after 72 h from each elution for 1000 s. ………………………. 237

Figure 3.74: Decay curve of 99mTc eluted from ZrMo colum. ………………………. 238

Figure 3.75: Typical Radiochromatogram of the obtained 99mTc eluates………….. 240

ABSTRACT

Technetium-99m is called the work horse, for many reasons, in nuclear medicine diagnostic purposes. It is produced as the β- decay of 99Mo radionuclide. Molybdenum-99 gel type generators are considered as a suitable alternative of the conventional chromatographic alumina columns loaded with fission molybdenum-99. 99Mo neutron-capture is cross-contaminated with radionuclides originated from activation of chemical impurities in the Mo target such 60C0, 65Zn, 95Zr, 175&181Hf, 86Rb, 134Cs, 141Ce, 152Eu, 140La,51Cr, 124Sb,46Sc, 54Mn, 59Fe and / or fast neutrons interactions with the stable isotopes of molybdenum such as 92mNb, 95Nb and 95Zr. To prevent contamination of the eluted 99mTc, successive purification methods were made. After complete dissolution of the irradiated target wrapped with thin Al foil in 5M NaOH solution, hydrogen peroxide was added to start precipitation of Fe(OH)3. The formed Fe (III) minerals allow complete elimination of some radiocontaminants from the molybdate solute such as 152Eu, 140La,141Ce, 45Mn and 92mNb in addition to partial elimination of 46Sc, 60Co and 59Fe radionuclides. The remaining supernatant was acidified by concentrated nitric acid to pH 9.5 for precipitation of Al(OH)3 with complete elimination of radiocontaminants such as 95Zr175&181H, 65Zn, 124Sb, 51Cr, 46Sc, 60Co and 59Fe. 134 86 Cs and Rb radionuclides were not affected by precipitation of Fe(OH)3 or

Al(OH)3. Chromatographic column of potassium nickel hexacyanoferrate (II) (KNHCF) has high affinity towards elimination of 134Cs and 86Rb radionuclides. Highly pure molybdate-99Mo solution was processed for preparation of zirconium molybdate gel generator with 99mTc eluate of high radionuclidic, radiochemical and chemical purity suitable for use in medical purposes.

Key words: 99Mo-molybdat, Crosscontaminant, Purification, Iron Oxides and 99 99m Oxyhydroxides, Al(OH)3, Potassium Nickel Hexa Cyanoferrate (II), Mo / Tc gel generator.

Aim of the work

99 Radioactive Mo ( T1/2 ≈ 67h ) has its importance as the parent of the 99m Tc radionuclide ( T1/2 ≈ 6h ) which is the most important radioisotope for nuclear medicine use. In reactors, interactions of thermal and epi-thermal neutrons with molybdenum containing targets are of considerable importance in the production of 99Mo radioactivity. The practical difficulties associated with the production of fission-99Mo are reflected in the required capital investment and routine running costs; the cost of production of 1 Ci fission 99Mo may be up wards of 4 times the cost of 1 Ci (n,γ) 99Mo. Processing of highly radioactive materials of irradiated uranium targets in a manner which compromises the safety of the environment, a complex infra- structure is required to deal with special problems of quality control and waste disposal. For commercial reasons developed countries, including Egypt, started the introduction of 99Mo/99mTc gel generators instead of the highly expensive chromatographic column generators based on alumina loaded with fission 99Mo. The molybdate gel matrices are usually synthesized by precipitation of neutron activation molybdenum-99 from its solutions with a variety of transition metal cations. The use of epithermal neutrons might lead to the production of 99Mo with high specific activity because of the high epithermal neutron cross-section for the 98Mo (n,γ) 99Mo reaction, it is as high as 11.6 barn. Production of 99Mo with the neutron-capture method is accompanied with some cross-contaminant radionuclides originated from neutron activation of chemical impurities in the Mo target materials such as: 186W(2n, γ) 188W (β) 188Re, 59Co (n,γ) 60C0, 64Zn (n,γ) 65Zn, 85Rb (n,γ) 86Rb, 133Cs (n,γ) 134Cs, 140Ce (n,γ) 141Ce, 50Cr(n,γ) 51Cr, etc and / or fast neutrons interactions with the stable isotopes of molybdenum such as 92Mo (n,p) 92Nb, 95Mo (n,p) 95Nb, 96Mo (n,p) 96Nb. To prevent contamination of the eluted 99mTc and / or decrease the problem of waste disposal, continuous efforts are made to purify the activation 99Mo solutes, as far as possible, from the interferring radiocontaminants xi before its precipitation in the form of a gel matrix. It is worth mentioned that the prepared molybdate gel matrices have markedly cation exchange properties. A simple and inexpensive method for purification of activation-99Mo product solution without adding strange chemical materials to the activation- 99 - Mo solute containing AlO2 species is investigated in the present work. This method may achieve reduced cost of purification, fast manipulation of 99Mo radioactivity and maintaining the chemical properties of 99Mo-molybdate (VI) for preparation of zirconium molybdate gel as the base matrix of chromatographic column for 99mTc elution. The scheme of work may be included the following topics:

1- Preparation and irradiation of MoO3 targets wrapped with thin aluminum foils, 2- Dissolution of the irradiated targets with their Al foil in NaOH solutions, 3- Identification of the product 99Mo cross-contaminant radionuclides, 4- In-situ precipitation of the Fe content of the Al wrapper with or without externally added Fe, 5- Physicochemical identification of the formed minerals, 6- Radiochemical assessment of the uptake of 99Mo-molybdate (VI) anions and elimination of cross-contaminant radionuclide,

7- Consequent precipitation of Al in the form of Al(OH)3 at pH values of 9.5 and 5 and carrying out the corresponding radiometric assessment as in the previous item, 8- Purification from 134Cs-cesium and other residual radionuclides by chromatographic column method, and 9- Quality control of the purified 99Mo-molybdate (VI) product may be manifested in preparation of 99Mo / 99mTc gel generator of the chromatographic column elution mode.

xii CHAPTER I INTRODUCTION

1.1. Preface: Technetium-99m is the most important radionuclide in nuclear medicine. It is called the work horse and is preferred, for many reasons, in diagnostic purposes (Srivistava et al., 1977; Deutsch and Libson, 1984; Sing et al., 1991; Hafelli et al., 1991; Griffith et al., 1991 and 1992; Jackson et al., 1992; Saha, 1992; Galy, 1994; Vanessa Moraes, 2005). As a result of its short 6 h half-life, higher amounts of radioactivity (multiple mCi doses) can be safely administered to the patients. Its monoenergetic gamma emission of 140 keV and no ß- radiation give better quality image of the organ and low radiation dose to the patient. 99mTc allows rapid build up activity after injection or administration and gives sufficient retention time in the organ. 99mTc is easily biodegraded and well extracted from the body. Carrier-free 99mTc is easily available in a sterile and pyrogen free state from 99Mo/99mTc generators. It can be easily eluted with high specific activity from its parent 99 radionuclide Mo (T1/2 = 67 h) with reasonable shelf-life which allows for shipment from manufacturers to hospitals. For some reasonable reasons, molybdenum gel type generators are considered as a suitable alternative of the conventional chromatographic alumina columns loaded with fission molybdenum-99. The molybdate gel matrices were usually synthesized by precipitation from solution of neutron activation molybdenum-99 with a variety of transition elements cations (Evans et al.,1982, 1984; Narasimhan et al., 1984 (a and b) ; Ramamoorthy et al., 1985; Evans et al.,1987; Moore et al., 1987; So, 1990; Sanchez-Ocampo and Bulbulian, 1991; Iyer et al., 1992; Saraswathy et al., 1992; So and Lambrecht, 1994; Patel et al., 1995; Sarkar et al., 1995; IAEA, 1995; Sarkar et al.,1997; Boyd,1997; El-Absy et al., 1990, 1993, 1994 and 1997; Abou El-Enein, 1997; Saraswathy et al., 1998 (a, b and c);

1 Mushtaq, 2004; Mushtaq et al., 2009; Davarpanah, et al., 2009). Insoluble molybdate salts of tetravalent cations such as Ce (IV), Ti (IV), Sn (IV) and Zr (IV) were studied as 99Mo / 99mTc gel generators. It was found that the elution yield of 99mTc depends on several factors, such as the nature of the cation which is connected with the molybdate (VI) anions, temperature and dilution of the precipitation solutions, pH value of the precipitating medium and drying temperature of the solid gel. The effect of cations is due to their oxidation potential, while the other effects were attributed to the degree of crystallization of the molybdate salts. The less crystalline compound is the highest precipitation and elution yields (Yassin, 1992; Boyd, 1997). The urgent demand of high technetium-99m volume specific activity, to meet with the recent applications of 99mTc radionuclide and to compete with the fission-molybdenum-99 generators, is the subject of current challenge. Most of the present research and development programs are directed towards the use of high molybdenum-99 specific activities in the precipitation process. However the isotopic abundance of 98Mo stable isotope of natural molybdenum is relatively high (24%), it is difficult to obtain 99Mo of high specific activity because the cross-section of the 98Mo (n,γ) 99Mo nuclear reaction is as law as 0.13 barn (Lavi and Fishlisun, 1973; Rayudu, 1993). The use of epithermal neutrons produces 99Mo of high specific activity, because the epithermal neutrons cross-section for the 98Mo (n,γ) 99Mo nuclear reaction is as high as 11.6 barns. Production of 99Mo with the neutron- capture method is accompanied with some cross-contaminant radionuclides originated from neutron activation of chemical impurities from the Mo containing target materials and / or fast neutrons nuclear reactions with the stable isotopes of molybdenum (Näsman et al., 1983; Moore et al., 1987). As most of the prepared molybdate (VI) gel matrices have cation exchange properties (El- Absy et al., 1990, 1993, 1994 and 1997; Abou El-Enein, 1997), it is important to eliminate and / or reduce the amount of these radiocontaminants from the molybdate solutions before synthesizing the molybdate gel materials.

2 Their passage to the 99mTc elutes may create serious chemical and radiation problems. Iron and aluminum oxides and oxyhydroxides are conventionally used as inorganic amphoteric ion exchange matrices for radionuclidic separation and purification from aqueous solutions of high level radioactivity. This is due to their low cost, ease of preparation and thermal, chemical and radiation stabilities. Usually, static and dynamic mobile aqueous phase methods are used for the chromatographic treatment process (Etherington, 1958; Simon et al., 1972 and 1973; Nesmeyanove, 1974; Gadde and Laitnen, 1974; Shigematsu et al., 1975; Arino and Kramer 1975; Music et al., 1979; Agasyan,1980; Nakayama et al., 1981; Benjamin, 1982; Steigman, 1982; Nesmeyanove, 1984; Krause, 1984; Munze, et al., 1984; Farley et al., 1985; Musić, 1986; Musić and Ristic, 1988;. Srivastava and Jain, 1989; Motojma 1990; Zaidi et al., 1990; Qureshi and Vaeshney, 1991; Manzione et al., 1994; Esmadi and Simm 1995; Clifford, 1999; Vogel, 2001; Gerory and Duan 2001; Johnstone and Heijnen, 2001; Damm et al., 2002; El-Absy, et al., 2002; Rozan et al., 2002; Dey et al., 2004; Van der Walls and Coetzee, 2004; Appelo and Postima, 2005; El-Absy, et al., 2005). Zirconium molybdate gels are mainly cation exchangers with open lattice structure through which pertechnetate anions diffuse. The chemical composition of zirconium molybdate gel plays an important role in the preparation of 99Mo/99mTc generator (Vesely and Pekaves, 1972).

1.2. Molybdenum: 1.2.1. Chemistry and radiochemistry of molybdenum: The radiochemistry of molybdenum and technetium are reviewed in the articles (Boyd and Hetherington, 1980; Joseph, 1982) and such text books deal with their general chemistry (Cotton and Wilknson 1979 and 1980; Lee, 1991; Greenwood and Earnshaw 1998).

3 Molybdenum has atomic number 42 and atomic mass 95.94 and lies in the VIB group of the Periodic Table. Molybdenum has eight oxidation states -2, 0, 1, 2, 3, 4, 5, 6 (Jhone Emsely, 1991). Whereas the oxidation states -2, 0, 1 are rare, the most stable oxidation state is + 6. It is commonly found in aqueous solutions. The aqueous chemistry of Mo (VI) is complicated and it has been studied by (Sylva and Davidson, 1979; Brown et al., 1986). Molybdenum metal is rapidly attacked by alkaline solutions producing 2- [MoO4] anions as monomer molecules. The metal doesn’t react with O2 at normal temperature. However, on strong heating it reacts with O2 forming

MoO3.

Different molybdenum oxides are known, such as MoO2, Mo2O5, MoO3. o MoO2 can be obtained by reducing MoO3 with H2 or NH3 below 47 C or o when Mo is heated at 800 C. MoO2 is insoluble in non-oxidizing mineral acids. It dissolves in concentrated HNO3 where Mo(IV) is oxidized to

Mo(VI). The oxide Mo2O5 is formed when finely divided molybdenum is o heated at 700 C, it is soluble in warm acids, MoO(OH)3 is precipitated if ammonia solution is added to the Mo(V) solution. Molybdenum trioxide

MoO3 is sparingly soluble in water but soluble in acids e.g. HCl to give oxy- 2- chloride and in alkali to give the normal molybdate anions MoO4 . Molybdenum is generally considered to exist in solutions as oxygenated anions in the + 6 oxidation state. It is easily reduced by the usual reducing agents such as Zn, SnCl2, SO2, and hydrazine (NH2NH2). In neutral or slightly acid solutions, molybdenum (VI) reduction produces molybdenum blue. Mo III is the usual end product of reduction process of Mo(VI). It is generally believed that the principal molybdenum species existing in alkaline solution is 2- the simple molybdate MoO4 anion. On acidifying such a solution, in absence of reducing agents and / or foreign cations, different isopolyanionic species of 6- Mo(VI) are formed, depending on the pH value, such as [Mo7O24] and 4- [Mo8O26] . At pH 0.9, a yellow hydrated molybdenum trioxide, MoO3.2H2O, precipitates. At pH < 0.9 molybdyl cation will be formed (Greenwood and

4 Earnshaw1984 and 1998; Lee, 1991; Mitchel, 1990 and 1999). In acidic solutions, molybdates are much less powerful oxidizing agents than vanadates and chromates. With increasing pH value, the oxidation potential decreases (Drew et al., 1976; Holm, 1987). Alkaline solutions of radiomolybdates are, however, somewhat unstable and undergo radiation induced reduction in which a dark colored substance is often precipitated (Boyd, 1982; Narasimhan et al., 1984a; Vanaja et al., 1987; Zaidi et al., 1990; El-Absy et al., 1994, 1997 and 2002; Abou El-Enein, 1997). This effect is overcome by addition of H2O2 solution to complete the dissolution of thermal neutrons irradiated MoO3 target (Boyd, 1982). 99 Molybdenum has nine radioisotopes among which Mo (T1/2 = 67 h) appears to be the most known isotope for medical applications and is used as the precursor of its daughter 99mTc. It is a neutron rich radionuclide and decays by β--particle emission to excited or isomeric states of the metastable 99mTc and 99Tc daughters. Approximately, 87.5 % of the total 99Mo radioactivity decays to 99mTc and the remaining 12.5 % decays to the long- 99 5 lived Tc (T1/2 = 2.14 × 10 y). Table (1.1) compiles the radioisotopes of molybdenum and their nuclear characteristics (Lide, 1993).

Table (1.1): Radionuclides of molybdenum and their nuclear characteristics

Nuclide T1/2 Main radiations emitted and energy (MeV). Mode of preparation 90Mo 5.7 h β+ = 1.4, γ = 0.1 to 1.1 93Nb(p, α) 91mMo 66.0 s β+ = 2.6, γ = 0.3 92Mo (γ,n) 91Mo 15.5 min. β+ = 3.3, No γ 92Mo (γ,n) 92Mo (n,2n) 93mMo 6.95 h IT, γ = 0.685, 1.479 93Nb (d,2n) 93Nb (p,n) 93Mo > 2 y EC 93Nb (d,2n) 93Nb (p,n) 99Mo 66.0 h β- =1.23, 0.45, Fission product γ = 0.14, 0.181, 0.74 and 0.78 98Mo ( n,γ) 101Mo 14.6 min β- Fission product 102Mo 11.6 min β- Fission product 1o5Mo 2.0 min β- Fission product

5 1.2.2. Production of molybdenum-99: Two nuclear reactions are considered for the production of 99Mo using either nuclear fission of the 235U nucleus (Shikata and Iguchi, 1986) or neutron activation of molybdenum containing targets. Irradiation of uranium in nuclear reactor leads to the fission of 235U nucleus yielding many fission chain products including 99Mo (Katcoff, 1960).

β - β - 235U (n,f) 99Zr 99Nb 99Mo 33 s 2.4 min

The nuclei absorb thermal neutrons and undergo fission reactions producing about 200 radionuclides including 99Mo. However, there are many other short-lived and stable Mo isotopes, it is usually called carrier- free 99Mo product. Therefore, 99Mo isotope of high specific activities is available from fission reactions. The separation and purification of the desired radionuclide, 99Mo, calls for sophisticated, tedious technological and special practical methods of high infra structures capital (Ali et al., 1982; Boyd, 1982; Ali and Ache, 1986 and 1987; Munze and Buger, 1987; IAEA, 1989; El-Absy, 1991). The required capital investment and routine running coasts of producing 1Ci fission 99Mo may be upward of four times the cost of 1Ci (n,γ) 99Mo. Also, the final product may be contaminated with some radioactive fission products which were not effectively separated by the applied chemical processing method (Boyd, 1982; Narasimhan et al., 1984a; Vanaja et al., 1987; Zaidi et al., 1990) To overcome the above-mentioned difficulties, 99Mo with carrier (i.e, activation 99Mo) was suggested to replace carrier free 99Mo in preparation of 99Mo / 99mTc generators especially in developing countries. 99Mo can be produced by irradiating Mo metal or different molybdenum containing targets such as molybdenum trioxide (Klofutar, et al., 1967) and ammonium molybdate (Loos, 1963) with thermal neutrons. The specific 6 activity of 99Mo (S) formed at time of irradiation (t) with a thermal neutron flux (φ) can be calculated from the following equation:

0.6 . σ . φ . a S = (1 - e -0.693t/T1/2) mCi / g Mo 3.7 × 107 A

Where σ is the activation cross-section in barns (0.14 barns), a is the natural % abundance of molybdenum-98 isotope (24.1 %). A is the atomic 99 mass of Mo (95.94), T1/2 is the half-life of Mo (67 h) in the same units as (t) (The Radiochemical Manual, 1966). The produced radioactivity of 99Mo is diluted with the inactive mass of Mo target, it is not a carrier-free, and has specific activity much lower than fission 99Mo. Specific activities of the order of 1Ci 99Mo/g molybdenum are achievable in a high neutron flux reactor. Using Mo target enriched in 98Mo isotope increases proportionally the produced 99Mo specific activity as a measure of the enrichment factor and the change in the effective cross-section due to different target geometry. Therefore, the specific activity of the (n,γ) 99Mo can be increased by 4 times if enriched 100 % 98Mo target material was used. However the thermal neutrons activation cross-section is ~ 0.14 barns, it acquires a significantly higher values in epi-thermal neutron fluxes of ~ 11.6 barns (Lavi and Fishlisun, 1973; Rayudu, 1993). The use of 98Mo enriched targets will not only increases the product 99Mo specific activity but also, decreases the production of cross-contaminant radionuclides.

1.2.3. Activation molybdenum-99 cross-contaminant radionuclides: 1.2.3.1. Fast neutrons: Fast neutrons of high flux reactors may induce (n,p), ( n, α), (n,2n) and (n, n/ p) nuclear reactions with the stable molybdenum isotopes and leads to

7 the production of several radionuclidic impurities of niobium and 92 92m 95 95m zirconium such as Mo (n,p) Nb (T1/2 = 10.14 d), Mo (n,p) Nb (T1/2 95 95 96 96 = 86.6 h), Mo(n,p) Nb (T1/2 = 35 d), Mo (n,p) Nb (T1/2 = 23.3 h), 97 97 98 98m 92 Mo (n,p) Nb (T1/2 = 72.1 min), Mo (n,p) Nb (T1/2 = 51.3 min), Mo 89 98 95 100 97 (n,α) Zr(T1/2 = 78.4 h), Mo(n,α) Zr (T1/2 = 64 d), Mo(n,α) Zr(T1/2 = 92 91 92 / 91m 16.9 h), Mo(n,2n) Mo(T1/2 = 15.5 min) and Mo (n,n p) Nb(T1/2 = 62 d) (Qaim and Stocklin, 1973; Qaim, 1974; Wolfle and Qaim, 1980; Cohen et al., 1983; Qaim et al., 1989; Zaidi et al., 1985 and 1990).

1.2.3.2. Thermal neutrons: Besides to the fast neutrons reactions products, and although high pure (186,188) (122,124) MoO3 targets were employed, significant quantities of Re, Sb, 134Cs, 60Co, 65Zn, 95Nb, 95Zr, 110Ag and 192Ir could be detected in samples of ( n,γ) produced 99Mo product. These impurities arise from the thermal neutrons activated traces of W, Re, Sb, Cs, Co, Zn, Nb, Zr, Ag and Ir which are present in the MoO3 targets (Boyd, 1982; IAEA, 1995). Moore, et al., (1987) and Näsman et al., (1983), found that activation 99Mo usually contains cross-contaminant radionuclides such as 51Cr, 92mNb, 95Zr/95Nb, 56Mn, 59Fe, 60Co, 65Zn, 134Cs, 124Sb and 140La. They stated that radiochemical impurities were present in extremely low concentrations. Apart from 99Mo, these impurities can occur as a result of (i) side nuclear reactions involving stable molybdenum isotopes, (ii) activation of chemical impurities present in the molybdenum oxide and (iii) decay of produced radioactive parent / daughters. Together with 25 radionuclides detected at longer cooling times, short-lived nuclides were detected only during the first one or two days after activation. The filtrates and washings of the zirconium molybdate matrix, contained soluble impurities such as 24Na, 42K, 134Cs, 140La and 188Re together with metals which form soluble molybdates in dilute acid solution. Activity levels were in the range 1-10-2

8 % of the 99Mo activity in the filtrate or washing. A dark residue, was left 59 99 95 behind after dissolution of irradiated MoO3, contained Fe Mo, Zr and 51Cr (in decreasing amounts) with traces of 56Mn, 58, 60Co, 92mNb, 187W, 110mAg, 113Sn, 65Zn, 124Sb and 182Ta. The activity levels of each of these impurities were in the range of 10-2 - 10-4 of the 99Mo activity in the residue after 24 h from activation. Impurities in the zirconium molybdate gels included 187W and 92mNb at about 10-2 % of the 99Mo activity with traces of 51Cr, 59Fe, 60Co, 65Zn, 113Sn, 124Sb and 140La at about 10-4 - 10-6 % of the 99Mo activity. Although 92mNb via 92Mo (n, p) 92mNb was expected in the eluate, its concentration was below the statistical limit of detection (10-5 % of 99mTc for a 1000 second count). Its production was enhanced by long irradiation in reactor positions having a high epithermal and fast neutron fluxes, but reduced in targets enriched in 98Mo.

1.2.4. 99Mo / 99mTc radioisotope generators: Radioisotope generator is a radiochemical separation arrangement based on strong fixing and storing of the parent radionuclide which decays and generates the corresponding radioactive daughter. When a state of radioactive equilibrium is reached, the short-lived daughter decays with the half-life of its parent and can be transported and readily eluted in situ (Subramanian and McAfee, 1971; McAfee and Subramanian 1991 and 1994; Wang et al., 1992; Knapp and Mirzadeh, 1994). In radioactive 99Mo / 99mTc generator, short-lived 99mTc radionuclide can be reliably separated in a high purity and yield and in a simple and safe way from its long-lived parent 99Mo. Kinetics of the parent-daughter radioactivities provides for the re-growth of the daughter nuclide after each separation cycle (IAEA, 1971; Spitsyn and Mikheev, 1971; Molinski, 1982; Graimella and Colombetti, 1983; Boyd, 1993; Rayudu, 1993; Egan et al., 1994; Knapp and Mirzadeh, 1994; IAEA, 1995; Maoliang, 1996).

9 Three types of generator systems have been established for production of 99Mo /99mTc generators: - Solvent extraction, this type of generators is based on different 2- - partition of molybdenum and technetium in the MoO4 and TcO4 forms, between immiscible aqueous NaOH and organic phases such as methyl ethyl ketone (Gerlit, 1956; Yang et al., 1972; Mani and Narasimhan, 1973; Sorby and Boyd, 1977; El-Asrag, 1978; Sanad 1979; Melichar 1990). - Sublimation is based on the different volatilities of molybdenum and technetium oxides. The readily volatile technetium-99m oxide sublimes first, while MoO3 of less volatility remains in the solid phase (Robson and Boyd, 1969; Robson, 1974; Tachimori et al., 1971; El-Asrag 1978). - Column chromatography, due to the disadvantages of the sublimation and solvent extraction generators systems, including complication of the systems, fire hazards and contamination via evaporation of methyl ethyl ketone (MEK), possible interference by polymeric organic residues in the 99mTc product with subsequent tagging reactions to produce undesirable changes in biological properties and highly trained personnel, a chromatographic generator was performed (Tucker et al., 1958 and 1962; Richards, 1965). This type of generators is based on 99 2- the strong retention of Mo-MoO4 on a solid matrix and ease elution of 99mTc using a suitable eluate. Many types of solid materials or sorbents were used in packing the chromatographic columns (Pinajian, 1966; El- Garhy et al., 1966; Meloni and Brandone 1968; Takahashi et al., 1970; Subramanian and McAfee, 1971; Maki and Murakami, 1971; El-Bayoumy, 1972; Arino and Kramer 1975; Abraskin et al., 1978; Kraloveet al., 1980; Joseph, 1982; Boyd, 1982; Mark et al., 1986;

10 Reich and Boegl, 1989; Wang et al., 1992; Knapp and Mirzadeh, 1994; Mirzadeh and Knopp 1996; Mushtaq et al., 1991).

1.2.4.1. Chromatographic column generators based on 99Mo molybdate (VI) gels: The 99Mo gel generator system for 99mTc supply combines the advantages of chromatographic column generators and the use of inexpensive ( n, γ ) produced 99Mo. This generator is based on eluting the 99mTc from a column form of 99Mo-metallic molybdate obtained either from converting 99Mo to an insoluble molybdate (post-irradiation) or irradiation of the inactive insoluble molybdate gel with thermal neutrons (pre-irradiation) and the isotopic exchange reaction between the loading radioactive 99Mo and inactive Mo gel as the column bed matrix. The basic requirements for use of the gel matrix in construction of a 99Mo / 99mTc generator are that, chemical and mechanical stability under the conditions of the generator operations ( i.e, preparation and separation processes), and the generated 99mTc radionuclide can be readily - separated in a pharmaceutically acceptable form ( e,g TcO4 ). Many research and development efforts have been expended for the preparation of 99mTc radioisotope generators using neutron activated 98Mo (n,γ) 99Mo targets of natural isotopic abundance and its incorporation into insoluble precipitates, such as zirconium molybdate, (Evans et al., 1982; Evans and Shying, 1984; Narasimhan et al., 1984a; Ramamoorthy et al., 1985; Moore et al., 1987; So, 1990; Sanchez-Ocampo and Bulbulian, 1991; Iyer et al., 1992; Saraswathy et al., 1992; So and Lambrecht, 1994; Patel et al., 1995; Sarkar et al., 1995; IAEA, 1995; Sarkar et al., 1997; Boyd, 1997; El- Kholy 1998; Saraswathy et al., 1998 (a, b and c); Mushtaq, 2004; Mushtaq et al 2009; Davarpanah, et al., 2009), titanium molybdate (Narasimhan et al., 1984b; Vanaja et al., 1987; Shafiq and yousif, 1995; IAEA, 1995), Sn(IV) molybdate (El-Absy

11 and El-Bayomy, 1990) and heteropoly molybdate complexes such that Ce (IV) molybdate (El-Absy et al., 1993, 1994 and 1997; Abou El-Enein, 1997). El-Absy et al., (1993), produced a 99mTc generator using post irradiation formed 12-molybdocerrate (IV) gel. Narasimhan et al., (1984 a) introduced a 99Mo / 99mTc radioisotope generator based on using a post-irradiation formed Zirconium molybdate- 99Mo gel matrix. El-Absy and El-Bayoumy, (1990), prepared a 99mTc radioisotope generator based on stannic molybdate-99Mo. Sanchez- Ocampo and Bulbulian, (1991) prepared both pre-and post-irradiated zirconium molybdate gel generator. Boyd, (1997), mixed zirconium molybdate / cerium molybdate gel matrix. El-Kholy, (1998), used zirconium molybdate, The generator was eluted with saline 0.9 % NaCl solution. 99mTc yield, radionuclide and radiochemical purity were 64, 99.99 and 99 %. Mo and zirconium content was 1.9 and 1.5 µ g / ml respectively. Narasimhan et al., (1984 b), prepared a 99mTc radioisotope generator based on the use of pre-irradiation formed zirconium molybdate gel matrix, hydrous zirconium oxide and 1 g inactive zirconium molybdate. Svoboda et al, (1985), used zirconium molybdate gel matrix. Vanaja et al., (1987), prepared 99mTc generator based on titanium molybdate gel matrix. El-Absy et al., (1994) used 12-molybdocerrate (IV). The generator eluted with saline give 87, 86 and 80 % 99mTc elution yield for the gel matrices dried at 50, 150 and 200 oC respectively. Shafiq and Yousif, (1995), used titanium molybdate gel matrix packed in glass column containing hydrous zirconium oxide / alumina prepared at different molar ratio. The low elution yield of 99mTc from the generators is probably due to the presence of reduced 99mTc radionuclides formed by β-particles decay of 99Mo. Radiation induced reduction, radiolysis and hydrated electrons may be the

12 major causes of this reduction in the elution yield. Introduction of Ce and - Fe in the formed gel may help in oxidation to TcO4 (Srivastova te al., et al., 1977; Evans, 1981; Ganzerli, 1987 Sanchez and Ocampo, 1991; Boyd 1997).

1.3. Iron: 1.3.1. Chemistry and radiochemistry of iron: Iron is the second most abundant metal, after aluminum, and the fourth most abundant element in the earth, s crust. The major naturally occurring iron ores are hematite, α-Fe2O3, magnetite, Fe3O4, limonite, FeOOH, and siderite, FeCO3. Iron lies in the first transition series of elements in the Periodic Table with atomic number 26 and mass number of 55.847. The highest oxidation state known is VI. Generally, iron has the oxidation states of -2, 0, 2, 3, 4 and 6. Chemically pure iron can be prepared by the reduction of pure iron oxide (which is obtained by thermal decomposition of ferrous oxalate, carbonate or nitrate) with hydrogen (Cotton and Hart, 1975; Cotton and Wilknson 1979 and 1980; Agarwal, 1987; Lee, 1991; Greenwood and Earnshaw 1998). Iron (II) and (III) are the most oxidation states of iron. FeO is obtained by decomposition of iron (II) oxalate, carbonate or nitrate. Solutions of ferrous salts Fe2+ are pale-green in color, while dilute solutions are colorless. Dilute alkali solutions 2+ precipitate Fe as Fe(OH)2as a white precipitate, in the absence of air.

2+ - Fe + 2OH Fe(OH)2 ↓

The formed Fe(OH)2 is soluble in acids but insoluble in dilute bases (Cotton and Hart, 1975; Cotton and Wilknson 1979 and 1980; Agasyan,1980; Agarwal, 1987; Lee, 1991; Greenwood and Earnshaw, 1984 and 1998). Under ordinary conditions, the precipitate is partially

13 oxidized, acquiring a dingy-green color. The end oxidation product is 2+ Fe(OH)3. Fe ion is a fairly reducing agent and is capable of being oxidized by the action of a number of oxidizing agents such as H2O2, 2+ KMnO4, K2Cr2O7 in acid solution, HNO3, etc. The oxidation of Fe by nitric acid proceeds according to the equation:

2+ + - 3+ 3Fe + 4 H + NO3 3Fe + 2 H2O + NO ↑

The oxidation of Fe2+ in alkali solution can be accomplished, for example, by hydrogen peroxide:

2+ - 2Fe + 4OH + H2O2 2Fe (OH)3 ↓

Iron (III) oxidation state exists in several oxide and oxyhydroxide forms, depending on the method of preparation. The brown hydrous ferric oxide, α-FeOOH is prepared by hydrolysis of iron (III) chloride solution or by oxidation of iron (II) hydroxide. When heated to 200 oC the final product is the red-brown hematite form α-Fe2O3. This oxide occurs in

Nature as the mineral hematite. However careful oxidation of Fe3O4 or heating one of the modifications of γ-FeOOH (e.g, lepidocrocite), another type of Fe2O3 called maghemite γ- Fe2O3 is obtained. The oxide Fe3O4 is a mixed FeII-FeIII oxide. In strong alkali, iron (III) ions precipitate as a red- brown Fe (OH)3 precipitate with no amphoteric properties such Al (OH)3 and Cr (OH)3. The precipitate is soluble in acids but insoluble in excess alkali solutions. Complete precipitation of Fe(OH)3 occur at pH 3.5 (Cotton and Hart 1975; Cotton and Wilkinson, 1979 and 1980; Charles et al., 1976; Agasyane 1980; Agarwal, 1987; Lee, 1991; Greenwood and Earnshaw, 1984 and 1998).

14 3+ - Fe + 3OH Fe (OH)3 ↓

The Fe3+ ion possesses the properties of a week oxidizing agent. If hydrogen sulphide is passed into an acid solution of Fe (III) salt, free sulpher precipitates:

3+ 2+ + 2Fe + H2S 2Fe + 2H + S ↓

One of the features of ferric iron in aqueous solutions is its tendency to hydrolyze and / or to form complexes. It has been established that hydrolysis is governed in its initial stages (as in the first stage to acid dissociation of the aqueous ion) by the following equilibrium constants (Cotton and Wilkinson, 1979; Charles et al., 1976; Flynn, 1984; Richens, 1997; Wesolowski and Palmar, 1994):

3+ 2+ + -3.05 [Fe(H2O)6] = [Fe(H2O)5(HO)] + H k = 10 2+ + + -3.26 [Fe(H2O)5(HO)] = [Fe(H2O)4(HO)2] + H k=10 3+ 4+ + -2.91 2[Fe(H2O)6] = [Fe(H2O)4(HO)2 Fe(H2O)4] + 2H k = 10 hexaquo ion (binuclear species)

In weakly acidic solutions, of pH = 3.5, the particles of the precipitate 2+ are in the form of positively charged species, such as [Fe(H2O)5(OH)] , + [Fe(H2O)4(OH)2] , binuclear and highly condensed species. The positively charged particles of the precipitate possess anionic-exchange properties. The attainment of equilibrium becomes sluggish and some colloidal gels are formed. Finally, hydrous ferric oxide Fe2O3.nH2O, which commonly called ferric hydroxide Fe(OH)3, is precipitated as a reddish-brown gelatinous mass. At least a part of the formed precipitate seems to be α- FeOOH (Agasyane 1980; Cotton and Wilkinson, 1979 and 1980;

15 Charles et al., 1976; Flynn, 1984; Richens, 1997; Wesolowski and Palmar, 1994). Conversely in alkali solutions, after adsorption of OH- ions, it accepts negative charges and converts to cation-exchanger, from solutions of pH value ≥ IEP, i.e at pH ≥ 8.4 (Music et al., 1979).

3+ - Fe + 3OH Fe (OH)3

3+ - - Fe + 4OH Fe (OH)4

4- Iron (IV) and (VI) oxidation states form the ferrite ions FeO4 as in the 4- 4- mixed oxides Ba2FeO4 and Sr2FeO4 and the red-purple ferrate (VI) ion 2- FeO4 . Ferrite (IV) is prepared by the reaction:

II II II M3 [Fe(OH)6]2 + M (OH)2 + 1/2 O2 2M2 FeO4 + 7H2O

4- These compounds don’t contain discret FeO4 ions but are mixed metal oxides. Ferrate (VI) ions can be prepared by oxidizing the suspension of

Fe2O3.xH2O in concentrated alkali by chlorine, anodic oxidation of iron in concentrated alkali, or by oxidation of iron filling with fused KNO3. The sodium and potassium ferrate are very soluble (Cotton and Hart, 1975; Cotton and Wilknson 1980; Agarwal, 1987; Lee, 1991; Greenwood and Earnshaw 1998). In general, iron has six radionuclides 52Fe, 53Fe, 55Fe, 59Fe, 60Fe and 61Fe and four stable isotopes 54Fe , 56Fe, 57Feand 58Fe. Two radionuclides were produced by irradiation of iron targets with thermal neutrons via the 58 59 nuclear reactions Fe(n,γ) Fe (T1/2 = 45 days) detected at 142, 192, 1099 and 1292 keV gamma-ray energy peaks and 54Fe(n,γ) 55Fe with very long

T1/2 = 2.7 y and detected at very low gamma-ray energy peak of 59 keV ( in the X-ray range). Also, 54Mn radionuclide is produced in a carrier free state

16 54 54 by the fast neutrons nuclear reaction Fe (n,p) Mn which decay with T1/ 2 = 290 day at E γ = 834 keV (Strominger 1958; Nilson, 1960; Liskien et al., 1990).

1.3.2. Transformations of iron oxyhydroxides and oxides: Iron oxyhydroxides and oxides are present in the environment forming a wide range of minerals, most commonly ferrihydrites (Fe4(OxOHyH2O)12 and Fe4.6(OxOHyH2O)12) (Richard et al., 1988), lepidocrocite γ-FeOOH, goethite α-FeOOH, magnetite Fe3O4, maghemite γ-Fe2O3 and hematite α-

Fe2O3 with different characters including stability, specific surface area and reactivity (Cornel and Schwertmann 1996; Larzen and Postmam 2001).

1.3.2.1. Transformations by catalytic action of Fe(II): Traditionally, iron oxides are considered as phases of constant composition. However, in the presence of Fe2+ the iron oxides become dynamic phases. The catalytic action of Fe2+ leads to transformation of the least stable iron oxides into more stable phases (Hanne et al., 2005). By 2+ the addition of Fe as FeCl2 to the least stable iron oxyhydroxides, the ferrihydrites (Fe4(OxOHyH2O)12 and Fe4.6(OxOHyH2O)12) are transformed either into more stable phase, such as hematite and goethite (Jang et al., 2003; Hansel et al., 2003; Jeon et al., 2003) or to mixed valance compounds such as green rust or magnetite (Tamaura et al., 1983; Tronc et al., 1992; Jolivr et al., 1992; Ona-Nguema et al., 2002).The reaction between solid-phase Fe(III) and aqueous Fe2+ is explained as electron transfer from adsorbed Fe2+ to structural Fe(III) (Tonc et al., 1992; Jolivr et al., 1992; Belleville et al., 1992; Jeon et al., 2001; Jeon et al., 2003; Williams and Scherer, 2004). The reactivity, the measure of reductive rate decrease from ferrihydrites to hematite in the order of (Richard et al., 1988; Postima, 1993; Larsen and Postima 2001):

17 Ferrihydrite > lepidocrocite > goethite > magnetite > maghemite > hematite the specific surface area also decrease with decreasing reactivity, particle size and reductive rate. Ferrihydryte transforms completely in 2 days into stable phase in the presence of Fe2+ even at the lowest concentrations. The transformation of the most reactive (unstable) iron oxides into more stable phase in the presence of Fe2+ has been observed by (Tamaura et al., 1983; White and Yee, 1985; Tronc et al., 1992; Joliver et al., 1992; Belleville et al., 1992; Bourrie et al.,1999; Jeon et al., 2001; Ona- Nguema et al., 2002; Jeon et al., 2003; Hansel et al., 2003). Tronc et al (1992) and Jolivr et al (1992) found that at low Fe (II) / Fe (III) concentrations, ferrihydrite was transformed into goethite. Whereas, at higher Fe (II) / Fe (III) concentrations magnetite was formed. Also, lepidocrocite was found to transform into magnetite in the presence of Fe2+. It was argued that hematite, presumably, transformed into magnetite in the presence of ferrihydrite (Tamaura et al., 1983; Jeon et al., 2001 and 2003). Earlier descriptions of interactions between Fe2+ and iron oxides have focused on electron exchange at the solid-phase surface, mediating the reductive dissolution of the oxide through a bridging legend such as oxalate, malonate, or citrate (Wehrli et al., 1989; Hering and Stumm, 1990; Suter et al., 1991; Kostka and Luther, 1994). Wehrli et al., (1989) and Suter et al., (1991) argued the OH- is not a suitable legend because of the insolubility of the Fe (III) hydroxo complex. The same must apply to O2- on the surface. In good agreement Manceau and Drits (1993) considered the conversion of ferrihydrite to goethite to be a dissolution / precipitation reaction. Tronc et al (1992) and Jolivr et al (1992) attributed the catalytic action of Fe2+ on the ferrihydrite-goethite conversion to the formation of a mixed valance, short rang ordered intermediate, which at

18 low Fe(II) / Fe(III) ratios re-crystallize to goethite and at higher ratios led to the formation of magnetite. This mechanism involves electron exchange between the Fe3+ in the solid-phase and an inner sphere bound Fe2+ ion across the edge of the outermost octahedron of the ferrihydrite surface through metal-metal bonding by overlapping d-orbitals as in magnetite (Sherman, 1987).

1.3.2.2. Transformation of Lepidocrocite to magnetite Fe3O4: 2+ The reaction of transformation of γ-FeOOH to Fe3O4 in presence of Fe can be written as (Kiyama, 1974; Kaneko and Katsura 1979; Tamura et al., 1981):

2+ + Fe + 2 γ-FeOOH Fe3O4 + 2H

The transformation reaction is triggered by the adsorption of the iron (II) ion on γ-FeOOH at a pH above 7.3. The adsorbed FeII-γ-FeOOH is subsequently transformed to F3O4. Under the same conditions, goethite α- FeOOH of less solubility 104-5 times than lepidocrocite γ-FeOOH was not transformed to Fe3O4.

1.3.2.3. Transformation of Fe(OH)2 to Goethite: Amorphous ferric oxyhydroxide precipitates by aerial oxidation of Fe(II) hydroxide from strong alkaline solution and from weakly acidic - solution by addition of OH (Misawa et al., 1969 and 1971).

dissol. ax amorphous Fe(III) - Fe(OH)2 Fe(OH)3 Fe(OH)3 aq oxyhydroxide α-FeOOH FeOx(OH)3-2x

, Some OH s in the amorphous ferric oxyhydroxide FeOx(OH)3-2x were substituted by the anions coexisting in the solution. Therefore, the transformation of the amorphous ferric oxyhydroxide to α-FeOOH must be achieved by removal of anions together with the dehydration and deprotonation. The deprotonation occur by the reaction with the OH,s in the solution (Van Der Kraan. et al., 1969). Presumably, the transformation is accompanied by the removal of coordinated anions for holding the electro- neutrality. Therefore, the transformation proceeds relatively rapidly in strongly alkaline solution but very slowly in acidic solution.

1.3.2.4. Transformation of lepidocrocite to goethite: γ-FeOOH tends to transfer to α-FeOOH in aqueous solution at 25oC. Goethite seems to be more stable in configuration than lepidocrocite which has about 104-5 times large solubility (Misawa, 1973). The transformation would proceed by dissolution of γ-FeOOH, followed by precipitation of α- FeOOH from Fe(III) solution as follows:

dissol. amorphous Fe(III) γ-FeOOH Fe(III) ions oxyhydroxide α-FeOOH FeOx(OH)3-2x

1.3.2.5. Transformation of magnetite to goethite under alkaline pH: He and Traina, (2007) investigated magnetite transformations to maghemite and goethite under extreme alkaline conditions. Goethite formation increased with NaOH concentration. Goethite was presumably formed through reconstructive dissolution / crystallization reactions that can be written as:

– – Fe3O4 + OH + H2O = -Fe2O3 + Fe(OH)3

– + 2Fe(OH)3 + 1/ 2 O2 + 2H = 2 -FeOOH + 2H2O

20 1.4. Chemistry of Aluminum: Aluminum is a metallic element lies in group III-A in the Periodic Table with atomic number 13 and mass number of 26.96. In aqueous solutions the Al3+ ion is colorless. When NaOH or KOH are added to Al3+, a white precipitate of Al(OH)3 will separate. Al(OH)3 is a typical amphoteric hydroxide dissolves with acids forming Al3+ ions and with alkali forming aluminates:

+ 3+ Al(OH)3 ↓ + 3H Al + 3H2O

- - Al(OH)3 ↓ + OH AlO2 + 2H2O

Complete precipitation of Al(OH)3 is achieved at pH ~ 5, further addition of alkali to pH ~ 10 results in the dissolution of Al(OH)3 with the formation - of AlO2 (Lee, 1977; Cotton, 1979; Agassyan, 1980; Greenwood, 1984) . Hydrolysis of Al ions is often represented as a sequential replacement of the water molecules by hydroxyl ions, and can also be thought of as a progressive deprotonation of water molecules in the primary hydration shell (Richens, 1997). The simplest representation omitting the hydration shell for convenience, is:

OH- OH- OH- OH- 3+ 2+ + - Al Al(OH) Al(OH)2 Al(OH)3 Al(OH)4 H+ H+ H+ H+

3+ - The dominant species in solution changes from Al to Al (OH) 4 over little more than 1 pH unit. In contrast, the corresponding changes for Fe occur + over more than 8 pH units and intermediate species, such as Fe(OH)2 and 2+ Fe(OH) , represent more than 90 % of soluble forms . Thus Al (OH)3 is a less stable colloid than Fe(OH)3, where its particles remain in a dispersed state for very short period of time and converts to a precipitate via fast

21 neutralization by cations from solution with consequent rapid coagulations (Gerory and Duan, 2001). Freshly prepared aluminum hydroxide precipitate is a heavily hydrated gel material. On aging or heating, a well crystallized compound having the structure of AlOOH or Al2O3.H2O is formed (Steigman, 1982; Motojma

1990). The surface electrical charges of Al(OH)3 precipitate are positive, neutral, or negative in the regions of acidic, neutral or basic solutions respectively, with an IEP at pH value 8.6, as shown in the following scheme (Arino and Kramer, 1975; Carvatho and Abrao, 1997; El- Absy, 2002 and 2005; Damm, 2002):

OH- OH- + - [ Al(OH)2] Al(OH)3 [AlO (OH)2] H+ H+ (acidic) (neutral) (basic)

HO OH HO OH HO OH OH- OH- Al Al Al + + H H O OH + (acidic) (neutral) (basic)

1.5. Ferrocyanides as fixed column bed: Highly insoluble ferrocyanides matrices show extreme selectivity for radioactive cesium, 134Cs and 137Cs, even in the presence of high sodium concentrations. In addition, they have high chemical, thermal and radiation stability (Valentini et al., 1972; Lehto et al., 1987 and 1989; Loos et al., 1989; Haas 1993; Tusa, et al., 1994; Mimura et al 1999; Loos et al., 2004; Kulyukin et al., 2005). Quite a large number of insoluble

22 ferrocyanides of various metals e.g, Ag, Zn, Cd, Cu, Co, Ni, Sn, Pb, Ce, Bi, Ti, Zr, V, Mo, W and U etc, have been studied for their ion exchange property. These exchangers are prepared by mixing metal salt solutions with H4[Fe(CN)6], Na4[Fe(CN)6] or K4[Fe(CN)6] solutions. Matrices of 1 1 M2[Fe(CN)6], M2M [Fe(CN)6] and M2M 3[Fe(CN)6]2 with various amounts of water of crystallization are reported for ferrocyanides of bivalent metals. Copper hexacyanoferrate was prepared by Kourim et al, (1964). The product was a mixture of Cu[CuFe(CN)6], K2[CuFe(CN)6] and

H2[CuFe(CN)6]. It was believed that the cation outside the complex is bounded by relatively weaker forces, and may be exchanged more or less readily for another one. Potassium copper hexacyanoferrate

K2Cu3[Fe(CN)6] with cesium uptake from simulated solutions equals to 2.25 ± 0.06 m mol /g was prepared by (Edward et al, 1983). Sodium- copper hexacyanoferrate (Bennett et al., 1982;), Potassium copper cobalt hexacyanoferrate and potassium copper hexacyanocobaltate (Ali et al., 1991). Potassium cobalt hexacyanoferrate with cesium capacity of 0.8 ± 0.06 m mol g-1 (Prout et al., 1965; Lehto et al., 1987 and 1990) and sodium zinc hexacyanoferrate (Kawamura et al., 1970 ), were found to improve higher affinity to cesium ion. Molybdenum hexacyanoferrate was developed and found to possess particularly attractive properties (Hays et al., 1964). Baetsle (1965) concluded two structural models which could explain the experimental X- ray diffraction patterns as well as other data of chemical composition. The 5- first called FeMo-II with formula [H4Fe(CN)6] [MoO3(H2O)x]12 and the 4- second FeMo-IV identified as [H4Fe(CN)6] [MoO3(H2O)x]16 . The unit cell of FeMo-II was found to be as a body of centered tetragonal structure, whilst it was found to be cubic structure in FeMo-IV. Hydrogen ion was the exchangeable ion responsible for the ion exchange process.

23 Potassium zinc hexacyanoferrate (II) was prepared by (Kowamura et al., 1970), The product was either Zn2[Fe(CN)6] or K2Zn3[Fe(CN)6]2 according to ratio of K4[Fe(CN)6] to the zinc salt. Botros, (1996 a) studied the effect of γ-irradiation doses on the exchange properties of potassium zinc hexacyanoferrate (II). Neutron activation analysis of the original and irradiated materials showed that K : Zn : Fe(CN) : H2O were in the ratio of 8.6 : 21.4 : 50.2 : 19.72 weight %, respectively. This study suggested that the counter ions are K+ and Zn2+ due to absence of change on pH value. Potassium nickel hexacyanoferrate K2Ni[Fe(CN)6]2.3H2O was prepared and its properties were studied using the column technique (Volkhin, et al., 1967). They recorded that nickel hexacyanoferrate was the most suitable compound for the decontamination of cesium from aqueous waste solutions with high content of surfactants.

1.6. Separation and purification of activation molybdenum-99: The methods of radiochemical separation and purification, available for treatment of radioactive solutions, fall generally into three main categories; chemical precipitation, distillation and ion-exchange. Other processes are being used, but not extensively (Carely-Macauly et al., 1981). When a suitable separation method is to be selected, the following criteria are considered, (i) chemical selectivity, (ii) radiation and chemical stability, (iii) low-corrosion characteristics, (iv) short reaction time, (v) minimum volume of the solution product effluents and safe operation. Generally, the effectiveness of any separation method can be expressed in terms of separation or removal change in concentration of a specific material (Nicholls, 1955; Carely-Macauly et al., 1981; Nesmeyanov, 1974 and 1984; El-Absy, et al., 2002 and 2005).

24 1.6.1. Precipitation methods: Most soluble radionuclides can be precipitated, co-precipitated or adsorbed by insoluble compounds, e.g. hydroxides, carbonates, phosphates, ferrocyanides and antimonates and removed from solutions. The formed precipitates carry suspended particles from the solution by physical entrapment (IAEA 1968). Chemical precipitation occurs by addition of chemical reactants and / or adjustment of the solution pH value. In case of radioactive precipitation, some factors have to be controlled for purity and completeness of precipitation such as (1) type and amount of the precipitating reagent, (2) temperature, (3) concentration of the trace contaminants, (4) order of addition of the reagents and (5) rate of precipitation and agitation. The obtained precipitate is separated by centrifugation rather than by filtration to avoid the very fine colloidal particulates yield loss (Glasstone, 1955; Etherington, 1958; Nesmeyanov; 1974 and 1984 Srivastava and Jain, 1989). The presence of a carrier substance, which is added in substantial amounts, helps a trace element to be precipitated more or less quantitatively. There are two main types of carrying out a micro- by the macro-component from solutions: 1- Isotopic carrying. When a salt of a radioactive micro-element is to be carried out an isotope carrier is added to the solution, the latter is then precipitated. For example, 140Ba can be carried out from a solution by

adding BaCl2 and precipitated as BaSO4. Homogeneous mixing occurs 2+ to the isotopic Ba ions onto the crystal of BaSO4. In this type of carrying out, it is necessary that the isotopic carrier is chemically similar to the radioactive substance with the same oxidation state and species (Glasstone, 1955; Srivastava and Jain 1989).

25 2- Non-isotopic carrying. A salt of another element helps in carrying down the precipitating traces. This type of carrying is necessary when the high specific activity of the desired micro-substance is to be maintained. For 54 60 example, Fe(OH)3 precipitates, with traces of Mn(OH)3, Co(OH)3 etc, 59 51 and Al(OH)3 with traces of Fe(OH)3 and Cr(OH)3. There are four types of non-isotopic carrying, (i) isomorphous replacement, (ii) formation of anomalous mixed crystals, (iii) surface adsorption and (iv) internal adsorption (Nesmeyanove, 1974 and 1984; Srivastava and Jain, 1989; Vogel, 1995; El-Absy, et al., 2002 and 2005). Generally, there are 4 types of co-precipitation mechanisms: 1- Inclusion. It is a mechanical entrapment via the solution surrounding the growing particles. Typically, this only is significant for large crystals. 2- External surface adsorption is the attachment of an impurity onto the surface of a particle or precipitate. This type of co-precipitation is generally not important as a mean of contaminant removal if the particle size is large, because large particles have very small surface area in proportion to the amount of precipitate they contain. Adsorption may be a major mean of contaminant removal if the particles are very fine. 3- Occlusion or internal adsorption takes place when a contaminant is trapped in the interior of a particle of precipitate. This type of co- precipitation occur by adsorption of the contaminant onto the surface of the growing particle, followed by further growth of the particles to entrap the adsorbed contaminant inside the growing particles. 4- Solid-solution formation: is another type of occlusion where a particle of the precipitate becomes contaminated with a different type of particle (s) that precipitate under similar conditions and whose size are nearly equal to those of the original precipitate, but its concentration is very low (Agasyan, 1980; Clifford, et al., 1999; Johnstone, et al., 2001).

26 1.6.2. Ion exchange methods: Ion exchange is a process in which reversible stoichiometric interaction of ions of the same sign takes place between an electrolyte solution or molten salt and ion-exchange sites of a solid / or liquid material called "ion exchanger". These sites are ionic groupings capable of forming an electrostatic bond with an ion of opposite charge. Total ion exchange capacity of an exchanger may be defined as the total number of ion-active groups / unit weight of exchanger; it is usually expressed in units of milli- equavelant per gram of exchanger (Qureshi and Vershney, 1991). The limited radiation stability of organic ion exchangers can be considered as a disadvantage when treating radionuclides of intermediate level and for the removal of high energy beta and gamma emitters, such as cobalt and cesium, and for the same reasons the presence of alpha emitters may be a problem (IAEA, 1984). Synthetic inorganic ion exchangers have been developed in recent years (Abe, 1983; Qureshi and Vershney, 1991). This mainly because of their higher stability towards higher radiation doses and temperatures than the commonly used organic resins. In addition to this, they sometimes exhibit highly specific properties which might permit improved separation under ordinary conditions. On the basis of the chemical characteristics; classification of the inorganic ion exchangers includes ( Krause, 1984; Qureshi, 1991): - Insoluble salts of heteropolyacids, e.g. ammonium molybdophosphate, - Hydrated metal oxides, e.g hydrous ferric oxides, hydrous aluminum oxides, hydrous titanium oxide, polyantimonic acid, and - Insoluble salts of cyano-complexes e.g ferrocyanides of copper and cobalt.

27 1.6.3. Literature survey on separation and purification methods of molybdenum: Activation 99Mo usually contains cross-contaminant radionuclides such as 51Cr, 92mNb, 95Zr/95Nb, 56&54Mn, 59Fe, 60Co, 65Zn, 134Cs, 86Rb, 124Sb, 1 52Eu and 140La (Näsman et al., 1983; Moor et al., 1987). Radiocontaminants of 134Cs, 86Rb, 60Co, 95Zr and 124Sb were detected in 99mTc eluates of alumina- based generators loaded with activation 99Mo (Wood et al., 1971; Podolak, 1972). To prevent contamination of 99mTc eluates and / or decrease the problem of waste disposal, efforts were made to purify the irradiated (n,γ) 99Mo target solutes, as much as possible, from the interferring radionuclides with different chemical treatment methods.

Thermally resistant inorganic adsorbents such as Al2O3, SnO2, MnO2 and 99 Sb2O5 were investigated for purification of fission Mo from inorganic and organic impurities (Burk et al., 1988). Silica-gel was used for adsorption of 95Zr and 95Nb from fission 99Mo dissolved in 6 M HCl acid solution (El-Garhy et al., 1972). Hydrolyzing metal salts, based on aluminum and iron, are very widely used as coagulants in water treatment and cation / anion removal from aqueous solutions. These materials have been applied routinely since early in the 20th century and play a vital role in the removal of many impurities from polluted solutions. These impurities include inorganic particles, dissolved inorganic and organic materials (Gregory and Duan 2001). Highly insoluble ferrocyanide matrices show extreme selectivity for cesium, 134Cs and 137Cs, even in the presence of high sodium concentration. El-Absy, et al., (2005) separated 137Cs, 129I and 106Ru from thermal neutron irradiated UO3 targets, aged for ~ 2.5 years, by distillation and solid / aqueous surface interactions in nitrate media of controlled chemical composition. The aged targets were digested with their Al wrapper in 2 M NaOH solution. Then, acidification by nitric acid to complete dissolution of

28 the formed residue. The 129I and 106Ru were separated by sequential distillation from 20 and 40 % HNO3 solutions containing H2O2 and KMnO4 as oxidants, resppictively. Thereafter, the fission product solution was brought to pH 9.5 by addition of NaOH solution to precipitate Al (OH)3, 137 MnO2 and Na2U2O7 leaving, mainly Cs in the supernatant solution.

1.6.3.1. Oxides and oxyhydroxides of iron (III): Freshly precipitated iron (III) hydroxides can be used for the decontamination of radionuclides from low-level radioactive solutions. The efficiency of decontamination depends on the oxidation state and the chemical properties of radionuclides (Shigematsu et al., 1975; Yoon et al., 1979; Agasyan, 1980; Benjamin, 1982; Ishikawa, et al., 1986; Kandori, 1992; Cornell and Schwermann, 1996; Clifford, et al., 1999; Johnstone, et al., 2001). Addition of iron (III) carrier to an acidic solution of 99Mo- molybdate followed by NH3 solution to precipitate Fe (OH)3, led to elimination of 96-98 % Zr and Nb (Zaidi et al., 1990). El-Absy et al. (2002) purified 99Mo-molybdate (VI) solutes from 95Zr, 92mNb, 95Nb and 124 Sb via entrapment onto in-situ precipitated Fe(OH)3 from weakly acidic and neutral pH value solutions. Due to its amphoteric ion-excahnge properties, around pH 8.4, the ability of the ferric hydroxide precipitate to sorb ions of heavy metals is characterized in single and multi-sorbate systems. Heavy metals could be sorbed both as cations (Cr3+, Co2+, Pb+, Cu2+, Zn2+, Ni2+, Cd2+) in neutral to 2- 2- 2- 2- high pH, and as anions (SeO , CrO , VO(OH) , AsOֿ³,MoO4 ) in neutral to mildly acidic pH. A summary of the effect of pH value on the sorption efficiency for a number of ions can be found in a paper by Manzione et al. (1994). For heavy metals present in cationic form, the sorption efficiency increases with pH, while concentration of both sorbate and ferric hydroxide play a secondary role (Farley et al., 1985). A surface complexation

29 mechanism by coordination bonds, similar to the formation of soluble complexes between solutes and functional groups, has been proposed (Benjamin, 1982; Farley et al., 1985; Gadde and Laitnen, 1974). A unifying model, apparently capable of describing data from a wide range of experimental conditions of pH and concentration, has been proposed by (Farley et al., 1985). Iron oxyhydroxides act as important sorbents for dissolved species, particularly heavy metals, phosphates and arsenate (Rozan et al., 2002; Appelo and Postima, 2005). Amphoteric sorption behavior by physical participation of fine particles and / or colloids facilitates incorporation of heavy metal cations directly into the precipitate matrix; a mechanism known as co-precipitation. This would account for only partial reversibility of the metal adsorption reaction upon reversal of pH.. Adsorption of monovalent cations (Cs+, Rb+) on hydrous iron oxides is not strongly pH-dependent and it can be regarded as nonspecific. On the other hand, adsorption of Ag+, divalent cations (Zn2+, Cd2+, Mn2+ and Sr2+) and trivalent cations (Cr3+, Ce3+, La3+, Eu3+ , Gd3+, Er3+, Yb3+ and Ga3+) are strongly pH-dependent (Music and Ristic, 1988). Simon et al. (1972 and 1973) studied the sorption of Mn2+ and Cd2+ on freshly precipitated

Al(OH)3 and Fe(OH)3. Esmadi and Simm (1995) studied the effect of pH, temperature, the composition of solution and presence of foreign anions on the sorption of cobalt ions in the course of formation and after the formation of the ferric hydroxide precipitate. It was found that sorption increases with increasing pH. The sorption of Co2+ ions is considered as a counter ion exchange. The sorption or co-precipitation increases in the presence of foreign cations such as 2 M KCl, NaCl and LiCl. In both cases, co-precipitation and sorption, the presence of excess anions enhances the removal of Co2+ over the whole pH range indicating physical nature of the bonding of Co2+ ions to the surface of the ferric hydroxide which is a

30 counter ion exchange (Simon et al., 1972). A plausible explanation for the effects produced by foreign anions could be that the specific adsorption of these anions produces additional negatively charges which make the surface more able to adsorb cations. Cations in the solution will compete for interaction with the surface of the precipitate but cobalt ions which are smaller in size and higher in charge have higher affinity to the surface than the alkaline metals. As a support for this competition principle, the order of increase in Co2+ uptake was found to be highest for potassium and lowest for lithium , which is the order of their radii of hydration: K+ = 2.32, Na+ = 2.62 and Li+ = 3.4 A (Cotton, 1980). The increase of Co2+ ions uptake in - - - - the presence of anions was found to be in the order: NO3 > Br > Cl . NO3 anions enhance the sorption of Co2+ more than halides due to their large size and lower tendency for complexation with iron compared to halides. At higher pH, anions has no effect on the uptake of Co2+ due to the high concentration of OH- that replace the foreign anions from the ferric hydroxide surface. Music et al. (1979) studied the sorption of gallium (III) on iron (III) oxide. With hydrolysis depending on pH (D,Mov and Savostin 1968), sorption of trace amounts of gallium (III) on iron (III) oxide can be illustrated as electrostatic and chemical processes. At low pH, there is electrostatic repulsion between the positively charged Ga3+ and the positively charged surface of iron (III) oxide. The enhanced sorption of gallium (III) with increasing pH may be explained either by mechanism involving direct exchange of the un-hydrolyzed gallium (III) ion with the H+ ion on the sorbent surface, or by a mechanism involving prior hydrolysis of the metal ions to give hydrolysis products which are hydrolytically adsorbed (Lieser et al., 1975). The sorbents showing hydrolytic adsorption all have OH- groups on the surface.

31 Dey et al., (2004) studied the sorption of Fluoride from aqueous solutions on hydrous ferric oxide, HFO. The fluoride adsorption density varies as a function of pH, particle size and presence of other functional anions in solution. Highest adsorption density for fluoride was found to be at pH 6. Fluoride adsorption thought to take place, in the given pH range, mainly by anion exchange via liberation of hydroxyl ions from HFO particles up to pH 5.0. Thereafter, adsorption of fluoride at an initial pH > 6.0 takes place by Van der Walls forces and not by anion-exchange. HFO functions as a cation-exchanger and adsorbs sodium ions presenting in solution and releasing protons. The most probable mechanisms operating for fluoride adsorption by HFO can be depicted as follows (Amphlett, 1964):

- + - - Fe2O3. xH2O (S) + F (aq) Fe2O3. (x-1) H2O. H F (S) + OH (aq) (at pH 2.0-5.0)

+ - . - + - + Fe2O3. xH2O (S) + Na (aq) + F (aq) Fe2O3 (x-1) H2O.OH Na F (S) + H (aq) (at pH > 6.0)

Modeling of the sorption of trace metals and oxyanions such as arsenate, and phosphate, on iron oxides in transition oxidized- reduced environments is affected by the reduction rate (i.e conversion from unstable to stable form of oxides). For example, the widely applied surface complexation model (Dzombak and Morel 1990, Appelo et al., 2002) becomes invalid when the solid phase changes in the course of the sorption process. Furthermore, one may question the significance of Fe2+ adsorption experiments on the various iron oxides (Liger et al., 1999; Hanne et al., 2005) and also the sequestration of heavy metals by iron oxides (Criscenti and Sverjensky, 2002) needs reconsideration.

32 1.6.3.2. Al(OH)3: The amphoteric properties of Al allows separation of Al3+ cations from other cations of group III. When a solution containing Al3+, Zn2+, Fe3+, Cr3+, Mn2+, Co 3+, Ni2+ and Ti4+ were dissolved in excess of alkali 3+ 2+ in presence of H2O2 or sodium peroxide, the cations Al and Zn are - 2- transformed into AlO2 and ZnO2 and remain in solution together with 2- CrO4 ions resulting from oxidation of Cr(III) by hydrogen peroxide in alkaline solution. The other cations are precipitated as Ti(OH)4, Fe(OH)3,

Co(OH)3, MnO(OH)2, and Ni(OH)2 (Lee, 1977; Cotton, 1979 and 1980; Agassyan, 1980; Greenwood, 1984; Agarwal, 1987). These phenomena facilitate the purification / desorption of chemical contaminants onto Al

(OH)3 surface (Agassyan, 1980; Lee, 1977, Cotton, 1979; Greenwood, 1984; Vogel, 2001). Sorption of Cr(VI) and Cr(III) on aluminum hydroxide were investigated by (Musić, 1986). Nakayama (1981) found that the sorption of chromate anions decreases as the pH of the suspension increase. 2- The mechanism of CrO4 was interpreted in terms of reaction between - chromates and OH and / or H2O groups at the hydroxide / liquid interface. It has been shown that chromates are more tightly sorbed on aluminum hydroxide compared to other anions, e.g. chlorides. On the other hand, specifically absorbed anions, such as molybdates, competes strongly with chromates for the sorption sites. The sorption of chromium (III) increases with increase of pH to ~ 100 %. Chromium (VI) can be reduced to Cr(III) with sodium bisulfite, ferrous sulfate, hydrazine and by the action of Fe2+ dissolved in solution. Munze, et al., (1984) separated highly purified fission 99Mo from uranium and the bulk of other fission products by dissolution of the aluminum cladded uranium fuel element in 6 N HNO3 by adsorption / desorption on alumina, then purification of the molybdenum-99 fraction by means of high temperature volatilization (distillation).

33 Van der Walls, (2004) irradiated uranium-aluminum alloy, cladded in aluminum target in the reactor for several days. The target material was dissolved in NaOH solution after cooling in order to let the short-lived radionuclides decay. The radioactive krypton and xenon were collected by activated carbon. Al, 99Mo, 131I and the radionuclide alkaline soluble elements (in sodium hydroxide solution) were separated from uranium and the radionuclide of alkaline insoluble elements by filtration. The 99Mo and 131I were separated by anion exchange chromatographic columns in alkaline medium from the bulk aluminum and radionuclides of other elements such as barium strontium and tellurium. 99Mo was selectively eluted using slightly alkaline lithium sulphate solution leaving the iodine radionuclide on the resin. The 99Mo eluate were acidified with oxalic acid and nitric acid then separated from the remaining aluminum and other radionuclides by anionic chromatographic column in acid media. Purification of activation molybdenum from Zr and Nb radioimpurities has been achieved by loading 99Mo-molybdophosphate in chloride media onto alumina columns, washing with a mixture of 0.01 M HCl-0.05 Br solutions and eluting Mo with 10 % NaOH solution (El-Garhy et al 1971). Arino and Kramer, (1975) reported that the adsorption capacity of molybdenum on alumina was ~ 20 mg Mo/g alumina at the pH-range of 1- 4.8 while it was ~ 2 mg Mo/g alumina at the pH-range of 5- 6.2. At higher pH- values the capacity decreased to much smaller values due to formation of normal molybdate (VI) anions of higher charge values per molybdenum atoms and / or change of the surface electric charge of Al (OH)3 precipitate.

1.6.3.3. Ferrocyanides: Potassium nickel and potassium zinc ferrocyanides and generally, the transition metal ferrocyanide complexes have high selectivity towards decontamination of different waste solutions from Cs+, Eu3+, Co2+, In3+, Cd2+,

34 Cu2+ , Sr2+ and Zn2+. Hexacyanoferrate ion exchangers are characterized by extreme selectivity for cesium cations, reproducibility of different preparations and use of low-cost materials (Loewenchuss, 1982; Lehto, and Hajula, 1987; Tusa et al., 1994; Nene and Turel, 1994; Milyutin, 1995). The exchangers act as cation exchangers with high affinity for alkaline metal ions especially Cs+ (Prout et al., 1965; Kawamora et al., 1970; Shahbendeh, 1980 and 1982; Abou-Mesalam 1993; Ismail 1994). The dynamic chromatographic column method is advantageous for cesium removal, however the static batch method is used too (Haas, 1993; Mimura, et al., 1999; Kulyukhin, et al., 2005).

The sorption of monovalent cations onto zinc ferrocyanide from NH4NO3 media and of Sr(II), Co(II), Ni(II), La(III) and Zr(IV) on potassium zinc ferrocyanide were investigated (Valentini et al., 1972; Nilchi et al., 2009). Separation of the couples Cs-Ba, As-Sb and Mn(II)-Ni in HCl acid solution onto nickel ferrocyanide columns was conducted (Loos et al., 1976). Removal of 134Cs and 60Co by in-situ precipitation of nickel ferrocyanide at ~pH 10 was studied (Moliah et al., 1998). The uptake mechanism of 137Cs by cobalt hexacyanoferrate is an ion exchange reaction. The thermodynamics and equilibrium ion exchange isotherms of this material were studied by (Ceranic et al, 1978). The fixed-bed technique for separation of 137Cs from burned up fuel samples onto cobalt hexacyanoferrate as commercially available ion exchanger was described (Ellenburg and MacCow 1968). The composition and ion exchange behavior of zinc hexacyanoferrate have been studied (Kawamura et al., 1970). Investigation of the cyanoferrates of zinc compounds, by various workers, were confined to the forward sorption reaction. The adsorption behavior from solutions containing Cs+, Rb+, Na+, Ag+ and mercury on zinc hexacyanoferrate has been studied. The complex preparation and characterization were discussed thoroughly. The mechanism of the separation of the alkali metals by the complex appears to be ion exchange reaction. The uptake capacity of cesium by the complex

35 Zn2[Fe(CN)6] is reported to be 5 m mole /g. The monovalent alkali metals are generally bound with increasing strength in the series( Valentini et al., 1973):

Na < K < NH4 < Rb < Cs

The rate of Cs+ uptake was found to be different for each compound. It was found that K2Zn3[Fe(CN)6]2 takes up cesium faster than Zn2[Fe(CN)6] . Vlasselar, et al., (1976) studied the ion exchange equilibrium of cesium ions on potassium zinc hexacyanoferrate K2Zn3[Fe(CN)6]2. The mean capacity was found to be 2.22 meq/g and the exchange of cesium with potassium was not limited to the surface layers of the solid phase. They also concluded the following selectivity orders for monovalent and divalent ions (Vlasselar et al, 1976):

+ + + + + + 2+ 2+ 2+ 2+ 2+ 2+ Cs > NH4 > K > Na > H > Li > Pb > Ba > Zn > Ca > Mn > Mg

The separation of Cs and Eu were also suggested by (Botros, 1996 b). Nickel ferrocyanides have capacities from 0.35 to 1.9 mol Cs/mol Fe (Loos et al., 1989). Ismail, (1994) studied the separation of cesium and cobalt from contaminating water using potassium nickel hexacyanoferrate complex and found that the matrix has high capacity for 137Cs than 60Co which achieved the possibility of their separation from each other. El-Absy et al., (2002) removed 134Cs+ ion from alkaline pH value solutions by in-situ precipitation of sodium nickel hexacyanoferrate (II) followed by feeding the molybdate (VI) supernatant through 12-molybdocerrate chromatographic column. El-Absy, et al. (2005) used more or less similar method for the separation of 137Cs from hot and aged FP solutions.

36 CHAPTER II EXPERIMENTAL

2.1. Chemicals and solutions: 2.1.1. Chemicals: All chemicals used in the present work were of AR grade.

- Acetone (CH3)2CO (d = 0.79 g/ml), M Wt = 58.08, Merck, Germany.

- Hydrogen peroxide, H2O2 (10 % w / v), M Wt = 34.01 Merck, Germany.

- Nickel chloride NiCl2, M Wt = 129.6, Arabic Laboratory Equipment Company (ALEC), Egypt.

- Nitric acid, HNO3 (69 %), M Wt = 63.01, BDH, England. - Sodium chloride, NaCl, M Wt = 58.44, Merck, Germany. - Sodium hydroxide, NaOH, M Wt = 40, Merck, Germany.

- Molybdenum trioxide, MoO3, M Wt = 143.95, Merck, Germany.

- Potassium ferrocyanide, K4[Fe(CN)6].3H2O, M Wt = 422, Merck, Germany.

- Ferric Chloride.Hexahydrate, FeCl3.6H2O, M Wt = 270.02 Ridel-de Haenag, Germany.

- Sodium nitrate, NaNO3, M Wt = 85, Merck, Germany.

- Zirconium-oxychloride, ZrOCl2.8H2O M Wt = 322.5 Merck, Germany.

2.1.2. Solutions: - Sodium hydroxide, 5.0, 2.0, 0.5, 0.3, 0.1 M NaOH solutions.

- Sodium nitrate, 3.5 and 0.3 M NaNO3 solutions were acidified with

HNO3 acid to pH value of 5 and with NaOH to pH value of 9.5.

- Potassium ferrocyanide, 0.5 M K4[Fe(CN)6] solution.

- Nickel chloride, 1.0 M NiCl2 solution. - Sodium chloride 0.9 % NaCl solution (saline).

37 2.2. Equipments: - Analytical balance: Precisision Electronic Balance, Model: HA 120 M, A&D Company, limited Japan.

- pH meter of the bench type HI-8418 with microprocessor, made in Italy. - A centrifuge with Max. Speed of 8000 rpm of "Vary-Hi-Speed Centrifuge" model, GCA/Precision Scientific, made in USA. - Shimadzu X-ray diffractionmeter, Model XD-490, with a nickel filter and Cu-Kα radiation, Japan. - X-ray florescence spectrometer, model PW 2400 Philips, Germany. - FT-IR spectrometer, Model-157, Bomem, Canada. - Shimadzu DT-60-thermal analyzer. Fitted with a balance type DTC 60, weighing platinum pan and heating device (Shimadzu). Temperature up to 650 oC with a heating rate of 10 oC / min. - Plasma emission spectrometer. Sequential plasma emission spectrometer of "ICPS-7500" type. Shimadzu, made in Japan, was used for detection of Fe, Co, Mn, Cr, Sc and Ce in the dissolved inactive Al solutes. - UV-VIS spectrophotometer of "UV-160 A" model, Shimadzu, made in Japan, was used for detection of Mo and Zr in ZrMo column eluates and Ni in KNHCF dissolved matrix. - NaI (TI) gamma-ray scintillation counter, Model "Scaler Ratmeter SR7", England, was used for routine measurements of gross gamma-ray radioactivities. - Multichannel analyzer coupled with a high purity germanium coaxial detector, Model GX 2518, Canberra Series, USA, was used for radiochemical assay and identification of gamma-ray emitters. It was calibrated using a mixed sealed source of the radioisotopes; 155Eu (86.5 and 105.3 keV), 57Co (122.1 and 136.5 keV), 137Cs ( 661.6 keV), 54Mn ( 834.8 keV) and 65Zn (1115.5 keV). - Ionization chamber, Model CRC-15R, Capintec, USA. 38 - Raman Attachment FT/IR, Model 6300-RFT - Jasco, Japan.

2.3. Identification of the contaminants: Chemical and radiochemical analysis was conducted out, to detect and identify the contribution of chemical impurities and / or radionuclides in each of the MoO3 powder and the Al foil, as a wrapper of MoO3 target.

2.3.1. Chemical analysis: A sample of 0.1 g aluminum foil was dissolved in 5 ml of concentrated hydrochloric acid. The chloride anions were removed by distillation and water dilution twice. The remained residue was re-dissolved to obtain 100 ml solution of pH value 1. To measure and identify the impurities found in the Al foil, one ml of the aluminum solution (pH 1) was analyzed by sequential plasma emission spectrometery for determination of the chemical contents of Fe, Co, Mn, Cr, Sc and Ce.

2.3.2. Radiometeric analysis:

The irradiated MoO3 powder, Al foil and / or the corresponding solutions were radiometericaly analyzed by gamma-ray spectrometery using a multi channel analyzer after different cooling time intervals, from the end of target irradiation, and counting rates.

2.3.2.1. Molybdenum trioxide:

Samples consisting of 0.0144 and 0.1 g MoO3 powder wrapped with small pieces of Al foil were irradiated in the ETRR-2 research reactor for four hours with a neutron flux of ~ 1014 n / cm2 s. The irradiated sample of

0.1 g MoO3 powder was dispatched and dissolved in 2 ml 2 M NaOH solution. The solute and powdered samples were radiometerically analyzed by gamma-ray spectrometry, after different cooling time intervals (3, 4, 6,

39 7, 13 and 75 days) from the end of irradiation for different counting rates (100, 100, 100, 100, 300 and 2000, s) to detect and identify short- medium- and long-lived activation induced cross-contaminating radionuclides together with the 99Mo from the obtained gamma-ray spectra. Under the corresponding characteristics energy peaks measured after cooling periods of ≤ 8 days and, usually, one and / or three months 99Mo and most of the other contaminants were measured for 100, 200 and / or 500, s, respectively.

2.3.2.2. Aluminum metal: Samples each of o.6 g aluminum foil were cleaned with acetone and air dried, to avoid chemical contamination, and irradiated in the ETRR-2 research reactor for ~ four hours with a neutron flux of ~ 1014 n / cm2. s. An irradiated aluminum foil was dissolved in 30 ml 5 M NaOH solution. To detect and identify the neutron activation induced radionuclides in the Al wrapper, samples of the irradiated Al foil and solute were radiometerically analyzed by gamma-ray spectrometry after different cooling time intervals of one month and 20 days, from the end of irradiation, for 500 and 1000, s.

2.4. Preparation of the MoO3 / Al radiotracer solutions:

Irradiation targets consisting each of 1.0 g MoO3 wrapped with 0.6 g of thin aluminum foil, previously cleaned with acetone and air dried, were irradiated in the Egyptian Research Reactor ETRR-2 with a neutron flux of ~ 1014 n /cm2.s for a period of ~ 4 hours or according to the working schedule of the reactor and dissolved after a cooling period of 8 days, thereafter. In preliminary dissolution experiments, inactive targets consisting of 1.0 g MoO3 wrapped with 0.6 g metallic Al foil were dissolved in NaOH solutions of different volumes (15, 20, 25 and 30 ml) and concentrations (1.0, 2.0, 3.0 and 5.0 M NaOH).

40 2.4.1. MoO3 / Al targets dissolution: Based on the above obtained results, routine dissolution of the irradiated targets was conducted out with 30 ml 5 M NaOH solution. After 8 days cooling periods the irradiated targets were transferred into a 100 ml conical glass beaker (dissolver). To the irradiated sample, 30 ml 5M NaOH solution was added at ambient laboratory conditions. The dissolution reaction was exothermic with evolution of molecular hydrogen and accomplished in ~ 15 min. The dissolution products solution was coloured black. The maximum dissolution temperature and the temperature gradient from the end of dissolution were recorded.

2.4.2. Nitric acid titration. Concentration of NaOH in the product Mo /Al solute (of inactive 1.0 g

MoO3 powder wrapped with 0.6 g Al foil) was determined and adjusted by acid / base titration method using 12 M nitric acid as the titrating agent. Sodium hydroxide concentration and alkali concentration adjustment of radioactive solutes were carried out on the light of the corresponding inactive acid / base titration results.

2.5. Purification via in-situ precipitation of Fe(III) minerals: 2.5.1. In-situ precipitation of Fe (III) iron from the Al wrapper: The product black-coloured solution obtained after complete dissolution of the MoO3 / Al target was treated by dropwise adding of

0.5 ml H2O2 (10 % w/v) solution with continuous shaking over a time interval of one minute and left to stand at room temperature, thereafter.

The solution became clear, with the addition of H2O2. Then, it began to be very faint red-coloured solution after ~ 15 min from the end of H2O2 addition. Gradually, hardly visual, very fine rosey-colloidal suspension was formed in the course of the next 180 min. The mixture solution was 41 centrifuged at the speed of 6000 rpm for 15 min, to collect the formed colloidal suspension. The supernatant was filtered with a 0.45 µm Millipore filter. Samples of 0.2 ml of the clear initial solution (just after complete addition of H2O2), the separated supernatant and the collected faint rose (or pale pink) gelatinous Fe(III) precipitate were radiometerically analyzed under comparable conditions. From the obtained gamma-ray spectra, the retention of 99Mo-molybdenum (VI) and the corresponding contaminant radionuclides were assessed.

2.5.2. Factors affecting the purification process: 2.5.2.1. Total amount of fed iron:

Twelve targets each consists of 1.0 g MoO3 powder wrapped with 0.6 g Al foil (containing 1.37 mg Fe from the Al wrapper) were irradiated under identical conditions, as described previously. After a cooling period of 8 days, from the end of irradiation, the targets were transferred into separate dissolution flasks. Equal volumes each of 8 ml 0.1 M HCl acid solutions containing 00.0, 10.0, 15.0, 20.0, 30.0, 35.0, 40.0, 45.0, 50.0, 55.0, 60.0 and 65.0 mg FeCl3. 6H2O were distributed among the separate flasks followed by 25.5 ml 6.67 M NaOH solution, respectively. No preservations were taken to avoid atmospheric air effects on the dissolution process of the irradiated targets and the products. As mentioned above, the dissolution reactions were exothermic with evolution of molecular hydrogen and accomplished in about 15 min with final dark black-coloured product solutions. However initially pale-pink and red coloured solutions of increasing intensities were obtained, with increasing the amount of fed

FeCl3.6H2O in the reaction mixture solutions, the colour disappeared with the progress of dissolution. Thereafter, 0.5 ml H2O2 solution (10 % w/v) was added dropwisly to the product solution (at ~ 60 oC) with strong mixing. The contributions of Fe in the individual product solutions are

42 1.37, 3.58, 4.47, 5.51, 5.57, 7.58, 8.6, 9.64, 10.67, 11.71, 12.73, 13.77 and 14.8 mg dissolved in ~ 34 ml 4 M NaOH solution and oxidized with 0.5 ml

H2O2 (i.e, 34 ml 0.721, 1.88, 2.35, 2.90, 3.99, 4.53, 5.07, 5.62, 6.16, 6.71, 7.25 and 7.80 x 10-3 M Fe dissolved in ~ 4 M NaOH containing 0.5 ml

H2O2). The dispersion time (i.e, the time necessary for starting coagulation) and the time of apparent complete precipitation of the formed Fe(III) iron minerals were recorded and listed. After 2-3 h, the supernatants and the formed gelatinous precipitates were separated by centrifugation for 15 min at a speed of 6000 rpm. The supernatants were withdrawn with a 0.45 µm Millipore filter. The initial 99Mo (VI) solutes and the supernatants were radiometerically analyzed to assess the effect of Fe concentration on the transformations of Fe(OH)3 into Fe(III) iron minerals and the elimination % of radionuclide contaminants from the 99Mo-molybdate (VI) solutes.

2.5.2.2. Effect of filtration:

Samples of 1.0 g MoO3 wrapped with 0.6 g Al foil were irradiated under identical conditions and transferred to the dissolution vessel after 45 days of cooling. Thereafter, amounts of 30 mg FeCl3.6H2O were added and dissolved by 30 ml 5M NaOH solution. Then, 0.5 ml 10 % H2O2 solution was added. After ~ 2 hours, the formed precipitates were separated by centrifugation. Equal volumes, each of 10 ml, of the supernatant were withdrawn with and without filtration with 0.45 and 0.20 µm Millipore filters, for radiometeric analysis by gamma-ray multichannel analyzer at the counting rate of 3000 s.

2.5.2.3. Concentration of NaOH in solution:

Four targets (each one consists of 1.0 MoO3 powder wrapped with 0.6 g Al foil) were identically irradiated in the ETRR-2 Research Reactor. After a cooling period of 8 days, from the end of irradiation, they were transferred

43 to separate dissolution reaction vessels, 30 mg FeCl3.6H2O dissolved in 3 ml 0.1 M HCl acid solution was added to each vessel followed by 25 ml 6.8 M NaOH solution (total volume = 28 ml). After complete dissolution, concentrated HNO3 acid was added, dropwisely with shaking to destroy the formed polymolybdate species, until neutralization to about 4.0 2.0 1.0 and 0.5 M NaOH solutions. The total volume was completed to 33.5 ml with addition of the corresponding alkali solution. Finally, 0.5 ml H2O2 solution (10 % w/v) was added to the reaction mixture solutions dropwisely with strong shaking. After ~ 2 hours of standing , the formed precipitates were separated by centrifugation and filtration of the supernatants with 0.45 µm Millipore filter. The molybdate (VI) solutions before and after precipitation of Fe(III) iron minerals were radiometerically analyzed, as described before.

2.5.2.4. Concentration of H2O2:

Three targets (each one consists of 1.0 g MoO3 and 0.6 g Al foil) were irradiated under identical conditions. After cooling periods of 8 days they were transferred to the dissolution flasks and 30 mg FeCl3.6H2O dissolved in 8.25, 8.0 and 7.5 ml 0.1 M HCl acid solutions were added separately to the dissolvers followed by 25.5 ml 6.67 M NaOH solution. After ~ 15 min, complete dissolution was accomplished and volumes of 0.25, 0.5 and 1.0 ml

10 % H2O2 solution were added to the product solutes dropwisly with strong mixing, respectively, to obtain a total volume of 34 ml. After ~ 2 hours of standing at room temperature, the formed precipitates and supernatants were separated by centrifugation and filtration with 0.45µm Millipore filter. The molybdate (VI) solutions before and after precipitation of Fe (III) minerals were radiometerically analyzed, as described before.

2.5.3. Assessment of the purification process: To identify the radiocontaminants and assess the elimination % of the corresponding contaminant radionuclides and 99Mo-molybdate (VI) retention

44 % via in-situ precipitation of Fe(III) minerals, samples of the initial 99Mo- molybdate (VI) solutions, the supernatants and the washed precipitates of the formed Fe (III) minerals were radiometerically analyzed after cooling periods of one, two and three months for different counting rates of 100, 200 and 2000 s, respectively. Long cooling time and counting rates were selected to avoid overlapping of 99Mo gamma-ray energy peaks with the gamma-ray energy peaks of low level radioactive contaminants and to improve their identification precision. The corresponding radionuclide elimination % was calculated from the formula:

Ai - Af Elimination % = ------x 100 Ai

Where, Ai and Af are the area under the characteristic gamma-ray energy peak of the respective radionuclide in the initial solution and the supernatant, respectively. The specific activity (S) of 59Fe radionuclide in the aqueous (l) phase is equal to its specific activity onto the formed Fe (III) minerals solid (s). It can be represented by the formula:

A l A s S = ------= ------X (Y – X)

59 Where; Al and As are the measured Fe activities of the liquid and solid phases, respectively, Y is the total amount of fed iron in the system (mg), X is the amount of Fe in the liquid phase (mg) and (Y-X) its amount in the formed Fe (III) mineral precipitate (mg).

2.5.4. Recovery of the retained 99Mo-molybdate anions:

Samples of 1.0 g MoO3 wrapped in 0.6 g Al foil were irradiated, cooled, dissolved in 30 ml 5 M NaOH solution, 0.5 ml H2O2 (10 % w/v) solution 45 was added, centrifuged to separate the formed Fe (III) precipitate and filtrated by 0.45 µm Millipore filter, as mentioned previously. The precipitate was radiometrically analyzed before and after twice washing, each with 5 ml 0.5 M NaOH solution. The recovery yield of molybdate (VI) anions and release of the sorbed radiocontaminants from the surface of the Fe (III) precipitate into the washing filtrates were calculated from the radioactivities of the washing filtrates. The ferric precipitate before and after the 1st and the 2nd washing processes and 1 ml of the 1st and the 2nd washing filtrate were analyzed by gamma-ray spectroscopy after a cooling time of 8 days for a counting rate of 100 s.

2.5.4.1. Effect of total iron dose:

Four irradiated targets each consists of 1.0 g MoO3 powder wrapped with 0.6 g Al foil, containing 1.37 mg Fe, were transferred into separate dissolution flasks. Volumes of 8 ml 0.1 M HCl acid solutions containing

00.0, 15.0, 30.0, 50.0, mg FeCl3. 6H2O were added and followed by adding

25.5 ml 6.67 M NaOH solution. After complete dissolution, 0.5 ml H2O2 (10 % w/v) was added to each flask. The formed precipitates were centrifuged and the supernatants filtrated. The separated precipitates were washed twice each with 5 ml 0.5 M NaOH solution. The precipitates were radiometrically analyzed before and after each washing process and were compared with the washing filtrates, to calculate the recovery yield of the molybdate (VI) anions and the consequent release of radiocontaminants sorbed onto the surface of the Fe (III) precipitates into the eluate. The ferric precipitates before and after the 1st and the 2nd washing processes and 1 ml of the 1st and the 2nd washing filtrate were analyzed by gamma-ray multichannel analyzer after a cooling time of 8 days at a counting rate of 100 s.

46 2.5.4.2. Effect of eluent:

Two targets each consists of 1.0 g MoO3 powder wrapped with 0.6 g Al foil, containing 1.37 mg Fe, were irradiated and transferred into separate dissolution flasks. Equal volumes each of 8 ml 0.1 M HCl acid solutions containing 30 mg FeCl3.6H2O were added to the flasks at room temperature followed by the addition of 25.5 ml 6.67 M NaOH solution and 0.5 ml

H2O2 (10 % w/v), thereafter. The precipitates were centrifuged and filtrated as mentioned above. The first precipitate was washed twice with 5 ml 0.5 M NaOH solution. The second precipitate was washed twice each with 5 ml distilled water. The precipitates were radiometrically analyzed before and after each washing process and compared with the washing filtrates, to calculate the recovery yield of the molybdate (VI) anions and the consequent release of the sorbed radiocontaminants from the surface of the

Fe (III) precipitates into the eluate. The ferric precipitates before and after the 1st and the 2nd washing processes and the 1st and the 2nd 1.0 ml of the washing filtrates were analyzed by gamma-ray multichannel analyzer after a cooling time of 8 days at a counting rate of 100 s.

2.5.5. Identification of Fe (III) minerals by Raman spectroscopy: Inactive Fe(III) precipitates were prepared and applied for Raman spectroscopic analysis to investigate the effects of iron dose, NaOH concentration and H2O2 on the transformation modes of Fe(III) precipitates in the presence and absence of molybdate (VI) anions under similar experimental conditions. The prepared sample was placed on a polished metal surface on the stage of an Olympus BHSM microscope, which is equipped with 50 x and 100x objectives. The microscope is a part of a FT/IR Model 6300-RFT &Raman Attachment-Jasco, Japan, Raman microscope system, which also contain a monochromator, a filter system (3000 Hz). Raman spectra were excited by Ex- Laser of 1064 nm at a

47 resolution of 16 cm-1 in the range between 50-4000 cm-1. Spectra were calibrated using 520.5 cm-1 line of a silicon wafer. Excitation Laser were filtered at least below 0.1 mW to avoid thermal effect for the sensitive iron oxides, hydroxides and oxyhydroxides. Repeated acquisition using the highest magnification was accumulated to improve the signal to noise ratio in the spectra with accumulation of 128.

2.5.5.1. Effect of total iron dose: Six targets each consists of 0.6 g Al foil (containing 1.37 mg Fe) with and without 1.0 g MoO3 were transferred to separate dissolvers, equal volumes each of 8 ml 0.1 M HCl acid solutions containing 10.0, 30.0,

35.0, 40.0, 50.0, and 65.0 mg FeCl3. 6H2O, were distributed among the dissolvers followed by 25.5 ml 6.67 M NaOH solution to achieve the dissolution process. After complete dissolution, 0.5 ml H2O2 solution (10 % w/v) was added dropwisly to the product solution (at ~ 60 oC) with continuous strong mixing. After 2-3 hours, the formed precipitates were separated by centrifugation for 15 min at a speed of 6000 rpm, air dried at 50 oC for 2 days in an electric furnace.

2.5.5.2. Effect of NaOH concentration:

Targets each consists of 0.6 g Al foil with and without 1.0 g MoO3 were transferred to separate reaction vessels, to each vessel 30 mg

FeCl3.6H2O dissolved in 3 ml 0.1 M HCl acid solution was added, followed by 25 ml 6.8 M NaOH solution (total solution volume = 28 ml). After complete dissolution, concentrated HNO3 acid was added dropwisely, with strong shaking to destroy the formed polymolybdate species, until neutralization to about 4.0 and 0.5 M NaOH solutions. The total volumes were completed to 33.5 ml with the addition of the corresponding alkali solution. Thereafter, 0.5 ml H2O2 (10 % w/v) was added dropwisely to the

48 reaction mixture solutions with continuous strong shaking and left to stand at room temperature. After ~ 2 hours, the formed precipitates were separated by centrifugation for 15 min at a rate of 6000 rpm and air dried at 50 oC for 2 days in an electric furnace.

2.5.5.3. Effect of H2O2 concentration:

Three targets each consists of 0.6 g Al foil with and without 1.0 g MoO3 were transferred to a dissolution flask, 30 mg FeCl3.6H2O dissolved in 8.25, 8.0 and 7.5 ml 0.1 M HCl acid were added to the dissolvers, followed by 25.5 ml 6.67 M NaOH solutions, thereafter. Complete dissolution was accomplished after ~ 15 min, and volumes of 0.25, 0.5 and 1.0 ml 10 %

H2O2 solution were added dropwisly with strong mixing to oxidize the product Fe (II) to Fe (III) and to complete 34 ml total volume. After ~ 2 hours, the formed precipitates were separated by centrifugation and air dried for 2 days at 50 oC in an electric furnace.

2.6. Purification via in-situ precipitation of Al(OH)3 matrices: 2.6.1. Precipitation at pH value of 9.5: After precipitation of Fe (III) minerals from 30.5 ml ~ 4 M NaOH solutions containing 0.5 ml H2O2 solution, the formed ferric precipitate was separated, as described above. Thereafter, the supernatant was acidified by adding concentrated nitric acid dropwisely with strong mixing (to avoid fast condensation of the polymolybdate (VI) anions) until pH value of 9.5.

A white gelatinous precipitate of Al(OH)3 was formed. The formed

Al(OH)3 precipitate was collected by centrifugation for 15 min at the speed of 6000 rpm. The supernatant solution was filtrated by 0.45 µm Millipore filter, to avoid the presence of fine gelatinous Al(OH)3 particles in the filtrate. Comparable samples of the initial supernatant solution, the separated supernatant and the formed Al(OH)3 precipitate were

49 radiometerically analyzed by gamma-ray spectrometery. The 99Mo loss and elimination of the contaminating radionuclides due to retention onto the formed Al(OH)3 precipitate were assessed and evaluated by comparing the obtained gamma-ray spectra.

2.6.1.1. Recovery of the sorbed molybdate (VI): To determine the loss of 99Mo-molybdate (VI) samples of 0.2 ml of the 99 initial Mo-molybdate (VI) supernatant remained after Fe(OH)3 99 precipitation, the formed Al(OH)3 precipitate and 0.2 ml of the Mo- molybdate supernatant of Al (OH)3 were analyzed after a cooling period of 8 days at a counting rate of 100 s.

Thereafter, the formed Al (OH)3 precipitate was washed 4 times each by

8 ml 3.5 M NaNO3 solution of pH value 9.5. The precipitate was analyzed before and after each washing process to determine the recovery yield of molybdate (VI) anions adsorbed onto the formed Al(OH)3 precipitate. The st nd rd th Al (OH)3 precipitate before and after the 1 , 2 , 3 and 4 washing and 0.2 ml of each washing filtrate were radiometerically analyzed after a cooling time of 8 days at the counting rate of 100 s. Different volumes of 0.2, 1.0, 1.2 ml of the washing filtrates were radiometrically analyzed after longer cooling periods and counting rates, to assess the released contaminant radionuclides.

2.6.1.2. Assessment of the purification process: Samples of 1.0, 1.0 and 1.2 ml of the initial 99Mo-molybdate (VI) supernatant (i.e, 99Mo-molybdate (VI) supernatant of the Fe (III) hydroxide precipitate), and the supernatant obtained after precipitation of the Al(OH)3 precipitate and the formed Al(OH)3 precipitate after final washing were analyzed by gamma-ray spectrometery after cooling time intervals of one, two and three months for 100, 200 and 2000 s, respectively. Long cooling

50 time intervals and counting rates were conducted to avoid the interference of gamma-ray energy peaks of 99Mo radionuclide with the energy peaks of low-level radioactive contaminants and to improve calculation of the respective elimination and retention percents:.

Ai - Af Vf Elimination % = ------x ------x 100 Ai Vi

Where, Ai is the area under gamma-ray energy peak of the respective radionuclide in the initial supernatant, before precipitation of Al (OH)3, and

Af is the area of the corresponding radionuclide in the supernatant after precipitation of Al (OH)3 measured under comparable conditions and Vi and Vf are the volumes of initial and final supernatants, (28.5 and 36 ml), respectively.

2.6.2. Precipitation at pH value of 5:

Precipitation of the corresponding Al(OH)3 precipitate was conducted out by acidification of the 99Mo-molybdate (VI) supernatant, remained after precipitation of Fe (III) minerals, with the addition of concentrated nitric acid to pH value 5. The formed precipitate was collected by centrifugation for 15 min at a speed of 6000 rpm for 15 min. The supernatant was filterated by 0.45 µm Millipore filter. Samples of 0.2 and 1.0 ml of the 99Mo-molybdate (VI) supernatants before and after precipitation of the Al (OH)3 precipitate and the formed precipitate were analyzed by gamma-ray spectrometery to investigate the chemical behavior of 99Mo-molybdate (VI) anions and the corresponding cross- contaminant radionuclides from the initial supernatant solution onto the formed Al(OH)3 precipitate.

51 2.6.2.1. Recovery of the sorbed molybdate (VI):

2.6.2.1.1. Washing with 3.5 M NaNO3 solution of pH value 5:

The separated Al(OH)3 precipitate was washed 4 times each by 8 ml

3.5 M NaNO3 solution of pH value 5. The precipitate was analyzed before and after each washing process to measure the recovered 99Mo- molybdate (VI) anions adsorbed onto the in-situ formed Al(OH)3 precipitate. At the same time, 0.2 , 1.0, 1.2 ml of each washing filtrate were radiometrically analyzed to determine the recovery yield of 99Mo- molybdate (VI) anions and the % release of radiocontaminants into the filtrates.

2.6.2.1.2. Washing with 3.5 M NaNO3 solution of pH value 9.5:

Alternatively, the separated Al(OH)3 precipitate was washed 4 times each by 8 ml NaNO3 solution of pH value 9.5. The precipitate before and after each washing process and 0,2 , 1.0, 1.2 ml of each corresponding washing filtrate were radiometrically analyzed by gamma-ray spectrometery to assess the recovery yield of molybdate (VI)anions and % release of radiocontaminants sorbed onto the formed precipitate into the filtrates.

2.6.2.2. Assessment of the purification process:

Samples of Al(OH)3 precipitated at pH value 5 before and after final washing by 32 ml 3.5 M NaNO3 solutions of pH value 5 and pH 9.5 were analyzed by gamma-ray spectrometery after a cooling time of 8 days at a counting rate of 300 s. Samples of 1.0 ml of the initial 99Mo-molybdate (VI) supernatant, the

Al(OH)3 precipitate after washing by NaNO3 solution of pH 5, and 1.0 ml of the supernatant solution were analyzed by gamma-ray spectrometery after cooling time of three months and counting time of 300 s. The elimination and

52 retention % were calculated by applying the above equation where, Vi and Vf equal 28.5 and 42 ml, respectively.

2.7. Purification onto potassium nickel hexacyanoferrate: 2.7.1. 99Mo-molybdate feeding solutions:

Target of 1.0 g MoO3 powder wrapped in 0.6 g aluminum foil of commercial grade was irradiated in the Second Egyptian Research Reactor for ~ 4 h at a thermal neutron flux of 1 x 1014 n cm-1 s-1. The irradiated target with its Al wrapper were dissolved in ~ 5 M NaOH solution with simultaneous addition of 3 ml 0.1 M HCl acid solution containing 30 mg FeCl3.6H2O. After an apparent complete dissolution, two successive in-situ purification processes were carried out via precipitation of Fe(OH)3 by addition of H2O2 and precipitation of Al(OH)3 at pH 9.5 via addition of concentrated HNO3 acid at 25 oC. After centrifugation, the supernatant was separated by passing through 45 µm Millipore filter to obtain 99Mo-molybdate (VI) solution of high concentration (4.3 mmole in 34 ml 3.5 M NaNO3 solution). Details of the irradiated target dissolution and precipitation of Fe(OH)3 and Al(OH)3 are mentioned above. The obtained Al(OH)3 precipitate was washed four times, each with 8 ml 3.5 M NaNO3 solution of pH 9.5, to recover the adsorbed 99Mo-molybdate (VI) anions. The total washing filtrate was completed to 34 99 ml with 3.5 M NaNO3 solution of pH 9.5 to obtain the second Mo- molybdate (VI) feeding solution of low concentration (0.7 mmole in 34 ml 3.5

M NaNO3 solution). The supernatant containing the bulk of Mo(VI) and washing filtrate constituted the 99Mo-molybdate(VI) feeding solutions of the prepared potassium nickel hexacyanoferrate (II), KNHCF (II), columns.

2.7.2. Preparation and characterization of the KNHCF (II) matrix: 2.7.2.1. Preparation of the KNHCF (II) matrix: The column matrix KNHCF was prepared by dropwise addition of 50 ml

0.5 M K4[Fe(CN)6].3H2O solution to 150 ml 1 M NiCl2 solution with stirring.

53 After standing for 4-5 h, the formed precipitate was separated by centrifugation for 15 min at a rate of 5000 rpm and air-dried at 100°C for 48 h. Thereafter, it was washed with 300 ml H2O, re-dried at 100 °C for 24 h, pulverized and sieved to 0.12- 0.24 mm particle size.

2.7.2.2. Characterization of the KNHCF (II) matrix 2.7.2.2.1. Thermal analysis: Thermal gravimetric analysis and differential gravimetric analysis measurements were performed using a simultaneous thermogravimetric and differential thermal analyzer Shimadzu DTG- 60- thermal analyzer. Temperature up to 650 oC with a heating rate of 10 oC min-1 were applied for 14.787 mg KNHCF (II) to determine the water content, thermal stability and matrix decomposition.

2.7.2.2.2. X-ray diffraction pattern: Sample of 1.0 g of the potassium nickel hexacyanoferrate (II) matrix was characterized by measurement of X-ray diffraction patterns using a Shimadzu X-ray diffractiometer, XRD 490, with a Nickel filter and Cu-K α radiation.

2.7.2.2.3. X-ray florescence: Sample of 1.0 g of potassium nickel hexacyanoferrate matrix was analyzed by using X-ray florescence spectrometer model PW 2400 Philips -Germany, for identification and determination of the elemental ratios K:Ni:Fe:C:N:H2O in the matrix .

2.7.2.2.4. Infrared spectra: IR spectrum was carried out in the infrared range from 4000 to 400 cm−1 using FT-IR spectrometer (Model-157, Bomem, Canada) for determination of the specific function groups of KNHCF(II) matrix.

54 2.7.2.2.5. Solubility: Solubility of the KNHCF (II) matrix was determined by overnight digestion with intermittent shaking in 25 ml 3.5 M NaNO3 solutions of pH1- 12 at 25±1°C. UV-VIS spectrophotometer (UV-160 A, Shimadzu, Japan) was 4- used for determination of [Fe(CN)4] anion in the filtrate by the Prussian blue method at 700 nm, in the concentration range from 0.013 to 50 ppm (Roberts et al., 1968).

2.7.3. Chromatographic column operations: Identical glass chromatographic columns (0.8 cm i.d.), supported with a small piece of glass wool at the bottom, were packed each with the slurry of 1.0 g KNHCF (II) in 5 ml distilled water and conditioned with passing 99 100 ml 3.5 M NaNO3 solution of pH 9.5. Then, 34 ml of the Mo- molybdate(VI) feeding solutions of pH 9.5 containing 4.3 and 0.7 mmol Mo were passed through individual columns at a flow rate of 0.2 ml/min and 25 °C. After complete feeding, the column was eluted with 3.5 M

NaNO3 solution of pH 9.5. Alternatively, column feeding was conducted with 4.3 mmol Mo at a higher flow rate of 5 ml/min.

2.7.4. Recovery of the sorbed molybdate:

The column bed was washed 4 times each by passing 5 ml 5 M NaNO3 solution of pH value 9.5 at a flow rate of 5 ml / min, to recover the retained 99Mo-molybdate (VI). The washing filtrates were filtrated by using a 0.45 µm Millipore filter to assay the recovered 99Mo-molybdate during washing and the released radiocontaminants, if they were found. The column bed after and before each washing step and samples of the filtrated washing effluents and the column bed after the 1st , 2nd, 3rd and 4th washing process were radiometerically analyzed by gamma-ray spectrometery.

55 2.7.5. Radiometric analysis: Radioactivities of the feeding solution and effluent, the fed column matrix before and after elution and the eluate were measured using a multichannel analyzer coupled with a high purity germanium coaxial detector (Model GX 2518, Canberra Series, USA). The respective gamma-ray spectra were measured, under comparable conditions, after cooling periods of 8 days and 3 months from the end of target irradiation. The long cooling period was chosen to follow, mainly, the long-lived radioimpurities after complete decay of 99Mo. The radionuclides were identified by their characteristic energy peaks in the obtained gamma-ray spectra as cited from the data reported by (Chu, et al 1999). Radionuclidic assessment was carried out by tracing the net area under the 181, 740, 605, 1173, 320, 1077 and 1692 keV gamma-ray peaks for 99Mo, 134Cs, 60Co, 51Cr, 86Rb and 124Sb, respectively.

2.8. Preparation of 99Mo / 99mTc generator: Molybdenum-99 / technisium-99m generator of high 99Mo radionuclidic purity was prepared and controlled according to the following:

2.8.1. Preparation of zirconium 99Mo-molybdate gel matrix: Freshly zirconium solution (0.0576 M) was prepared by dissolving 3.25 g zirconium-oxy-chloride ZrOCl2.8H2O in 140 ml distilled water and left standing for 24 h to stabilize the pH value. The sodium molybdate (VI) solution was prepared by dissolving 0.8 g MoO3 in 10 ml 2 M NaOH, few drops of 10 % w/v H2O2 solution were added then gentle heated to expel excess of H2O2. The obtained molybdate solution was acidified by nitric acid to pH value 9.5 with a final volume of 35 ml (0.00555 M). The

56 zirconium solution was added dropwisly to the molybdate solution and the pH of the mixture solution was raised by adding NaOH solution with strong mixing until precipitation at pH value of 4.7. The final concentrations of Zr and Mo in mixture solution were found to be 0.0576 and 0.0317 with Zr : Mo molar ratio of 1.817 : 1. The formed gel was filtrated, washed by distilled water and air dried for 24 hour at 50 oC.

2.8.2. Characterization of zirconium 99Mo-molybdate gel matrix: 2.8.2.1. Thermal analysis: Gravimetric thermal analysis and differential thermal analysis measurements were performed using a simultaneous thermogravimetric and differential thermal analyzer Shimadzu DTG- 60- thermal analyzer. Temperature up to 650 0C with a heating rate of 10 deg min-1 were applied for 22.019 mg ZrMo matrix to determine the water content, thermal stability and matrix decomposition.

2.8.2.2. X-ray diffraction pattern: Sample of 1.0 g of the prepared zirconium molybdate gel was characterized by measurement of X-ray diffraction patterns using a Shimadzu X-ray diffractiometer, XRD 490, with a Nickel filter and Cu- K α radiation.

2.8.3. Preparation of 99Mo / 99mTc generator: 2.8.3.1 Preparation of highly pure 99Mo-molybdate (VI) solute:

Sample of 1.0 g MoO3 wrapped in 0.6 g Al foil was irradiated, transferred to a dissolver, 30 mg FeCl3.6H2O dissolved in 3 ml 0.1 M HCl acid solution was added, then dissolved in NaOH solution. Sequential purification methods were operated via precipitation of Fe (OH)3 and Al(OH)3 precipitates and KNHCF chromatographic column preparation were conducted as shown 57 above. Except for, the zrconium solution was added to the final 99Mo- molybdate (VI) supernatant. Highly radionuclidic pure Zr99Mo matrix was filtrated, washed and dried as in the method of preparation of inactive zirconium molybdate.

2.8.3.2. Operation of chromatographic column: 1.0 g of the prepared zirconium molybdate matrix in 10 ml 0.9 % NaCl (saline) solution was packed in a glass column of 0.8 cm i.d × 30 cm length plugged with a small piece of quartz wool. The column was washed with 50 ml 0.9 % NaCl solution and conditioned for 99mTc elution by passing further 50 ml saline solution at a flow rate of 0.5 ml min-1. The column was kept for 24 hour to reach the radioactive equilibrium state of the 99Mo - 99mTc isobars. The generator was eluted by passing 10 ml 0.9 % NaCl solution at a flow rate of 0.5 ml / min and 25 0C.

2.8.4. Quality control of 99Mo / 99mTc generator: 2.8.4.1. 99mTc Elution curve and yield: The corresponding elution yield of 99mTc radionuclide in 10 ml generator eluate collected at 0.5 ml / min flow rate was calculated as follows:

Ab - Aa Elution yield, % = ------x 100 Ab

99m Where, Ab and Aa are the total activity of Tc on the chromatographic column bed before and after each elution process. The corresponding elution profile of 99mTc radionuclide was drawn by plotting the 99mTc activity of the 1st, 2nd, ------10th ml relative to the total eluted 99mTc radioactivity (i. e, %).

58 2.8.4.2. Radionuclidic purity: To identify the contribution of foreign radionuclidic contaminants present in the 99mTc eluate, it was radiometrically analyzed immediately and after 72 h from elution by gamma-ray spectroscopy using a multichannel analyzer. Alternatively, the radionuclidic purity of 99mTc eluate was studied by following its gross-radioactive decay with respect to time by NaI (TI) scintillation counter and plotting of the corresponding decay curve.

2.8.4.3. Radiochemical purity: Chemical identity of the 99mTc-radionuclide in the obtained eluates was examined by applying the ascending paper chromatography method. A strip of Whatmant No. 1 paper of 30 cm long and 5 cm wide was marked gently with a pencil at a distance of 5 cm from the lower end. 0.5 ml of 99mTc eluate was applied with a micropipette in the form of a small spot at the middle of the pencil line. The spot was dried under infrared lamp. The developing solvent (85 % methanol) was placed at the bottom of an air tight chromatographic jar. The paper was hanged in the jar from the other end and dipped into the solvent. After the movement of the front of the solvent to almost 12 cm (45-60 min), the paper was divided into strips each of 1 cm width and radiometrically analyzed. The counted radioactivity in each strip was plotted as a function of the travelled distance from the starting line. The Rf value was calculated according to:

Distance (cm) from the starting line to the radioactivity peak position

Rf = ------Distance (cm) from the starting line to the solvent front

59 2.8.4.4. Chemical purity: 2.8.4.4.1. Determination of molybdenum: One ml 99mTc eluate was added in a separatory funnel in addition to 2.0 ml of concentrated HCl acid, 1.0 ml of ferrous sulphate and 3.0 ml of potassium thiocyanate solutions, respectively. Thereafter, the mixture was shaked gently and 3.0 ml of stannous chloride solution was introduced. The volume was completed to 25.0 ml with distilled water. 10.0 ml of isoamyl alcohol was added to the funnel and shacked for 30 s. The phase was allowed to separate and the lower aqueous layer was run out. The organic phase was collected in 10 ml glass vial. The absorbance was measured at a wave length of 465 nm using 1 ml quartz cell against the blank (Sandell, 1959). From the previously obtained calibration curve, the molybdenum concentration was determined.

2.8.4.4.2. Determination of zirconium: Zirconium impurities in 99mTc eluates were specrtophotometerically determined by complex formation with Arsenazo-III, followed by measuring at wavelengths of 665 nm. The detection limit of this procedure is < 5 ppm (Savvin 1961; Suzuki 2009). To the acid sample solution in a 25 ml standard flask, containing 2 ml of the 99mTc eluate solution, add 2 ml of Arsenazo-(III) and 20 ml of conc HCl (9 M), dilute to the mark and mix well. Measure the absorbance at 665 nm, using a reagent blank as reference.

2.8.4.4.3. Determination of pH value: The pH of the 99mTc eluate was measured behind the Pb glass window of a fume hood, using an appropriate pH indicator paper.

2.8.5. Reproducibility of the 99mTc elution performance: The above mentioned Q. C. indices were conducted out at variable elution frequencies and generator age. The obtained results were tabulated.

60 CHAPRET III RESULTS AND DISCUSSION

3.1. Activation molybdenum-99 cross-contaminant radionuclides:

Figure 3.1 shows typical gamma-ray spectrum of 0.1 g MoO3 target irradiated in the Egyptian Second Research Reactor ETRR-2 for 4 hours with a thermal neutron flux of ~ 1014 n /cm2 s. The irradiated target was cooled for ~ 90 days, from the end of irradiation, before radiometeric spectroscopy analysis with a multichannel analyzer for a counting rate of 2000 s. It is observed that after cooling period of 90 days different medium-and long- lived radionuclides, such as 152Eu 141Ce, 51Cr, 134Cs, 124Sb, 95Zr, 95Nb, 92mNb,65Zn and 60Co produced as thermal neutrons cross-contaminant activation products, were detected at the characteristics gamma-ray energy peaks of 122, 145, 320, 343, 562, 569, 602, 604, 724, 756, 765, 778, 795, 934, 1115, 1173, 1332, 1368, 1407.5 and 1692 keV. Natural molybdenum containing targets contain the stable isotope of 98Mo with an abundance value of ~ 24.1 % and reaction activation cross section of 0.14 barns. Table (3.1) Compiles the calculated specific activity in mCi / g Mo irradiated in the Egyptian Second Research Reactor (ETRR-2) at a neutron flux of ~ 1 x 1014 n /cm2 s for different irradiation time intervals. The calculated 99Mo radioactivity was verified according to (Munze et al., 1980). The obtained specific activity of 99Mo produced at different irradiation time-

Table (3.1) Calculated specific activity in mCi / g Mo irradiated in the Egyptian Second Research Reactor (ETRR-2) at a neutron flux of ~ 1 x 1014 n /cm2 s for different time intervals.

Time of irradiation, h Specific activity, mCi / g Mo 4 80 20 367 40 900 100 1313 120 1420 150 1471 200 1750 Saturation 2000

Cs ( 801.8 keV ) Cs ( 801.8

134

) Cs ( 795.8 keV ) Cs ( Cs ( 568keV ) Cs ( Nb ( 765.8 keV ) Nb ( 765.8 134 134 ) 95

)

keV 1173.4 keV ( . Cs ( 1365 keV ) Eu ( 1407.5 keV) Co ( 1332,8 keV ) keV ( 1332,8 Co Zn (1115.1 keV ) Co 145 60 134 152 ( 65 60 Nb ( 934.6 keV ) keV 934.6 Nb ( Eu ( 778 keV ) 344.3 keV m Zr (724 keV ) Zr (756 keV ) Eu ( 121.6 keV ) Ce ( Cs ( 562 keV ) Cs ( 604 keV ) 95 95 153 92 152 141 134 134 Eu ( 244 keV ) Eu Cr (320 keV ) 152 51 152 Sb ( 1692.2 keV ) keV Sb ( 1692.2 124 Counts per channel, arbitrary units

Gamma-ray energy, keV

Fig. 3.1. Gamma-ray spectrum of 0.1 g MoO3 irradiated powder at the ETRR-2 reactor and measured after three months cooling period, from the end of irradiation, for 2000 s.

62 periods and thermal neutron fluxes are listed in Table (3.2). It is known that target materials irradiated in positions of epithermal neutron flux channels exhibit higher reactions cross-sections and specific activities of about ten times higher than thermal neutrons.

Table (3.2). Variation of the specific activity of 99Mo with the neutron fluxes and irradiation time (Munze et al., 1980) Neutron flux Irradiation time (h) (n/cm2.s) 24 48 96

1011 0.426 mCi/g 0.758 mCi/g 1.22 mCi/g 1012 4.26 mCi/g 7.58 mCi/g 12.2 mCi/g 1013 42.6 mCi/g 75.8 mCi/g 122 mCi/g 1014 426 mCi/g 758 mCi/g 1220 mCi/g

Tables (3.1) and (3.2) show that irradiating 1.0 g metallic molybdenum target in the reactor, only, an extremely small amount of the target is converted to radioactive 99Mo by (n,γ) nuclear reaction (Victor and Molinski, 1982). However the specific activity of 99Mo obtained from high flux reactors (e.g, the Egyptian Second Research Reactor ETRR-2) after 99 100 hours of irradiation period is high enough ( ~ 1313 mCi Mo / g Mo) for solving the problem of preparation of medium and high radioactivity 99Mo / 99mTc generators by using the gel generator technology (Evans et al.,1982; Narasimhan et al., 1984a; Evans and Shying; 1984; Ramamoorthy et al., 1985; Moore et al., 1987; So, 1990; Sanchez- Ocampo and Bulbulian, 1991; Iyer et al., 1992; Saraswathy et al., 1992; So and Lambrecht, 1994; Patel et al, 1995; Sarkar et al, 1995 and 1997; IAEA, 1995; Boyd, 1997; Saraswathy et al., 1998 (a, b and c); Narasimhan et al.,1984b; El-Absy et al.,1993, 1994 and 1997; Abou El- Enein, 1997). The product-impurities (Fig. 3.1) may be partially or completely retained onto the prepared gel matrices and eluted with the 99mTc eluates. Tracers of side-product radionuclidic impurities such as 63 134Cs, 95Zr, 124Sb, 95Nb and 60Co (Wood and Bowen, 1971; Finck and Mattason, 1976; IAEA, 1995; Boyd, 1997) and 92m, 95Nb and 95Zr (Qaim and Stocklin, 1973; Qaim 1974 and 1989; Wolfle and Qaim 1980; Cohen et al., 1983; Zaidi et al., 1985 and 1990; Liskien et al.,1990) were simultaneously produced with 99Mo. Rapid, simple and reproducible methods for purification of the 98Mo (n,γ) 99Mo solutions from the interferring radionuclides, as much as possible, is viable to prevent contamination of the 99mTc eluates with consequent smaller accumulated patient dose and / or problem of waste disposal at the nuclear medicine hospitals and clinics. Initially, identification of the short-, intermediate- and long-lived cross- contaminant radionuclides produced in the neutron-irradiated 98Mo containing targets and its Al wrapper is of great importance to define properly the selected purification and decontamination method(s).

3.2. Targets preparation and irradiation: Unless otherwise stated, for purification and assessment investigations of 99 each specified Mo-molybdate solute, targets of 1.0 g MoO3 powder wrapped with a small piece of 0.6 g aluminum foil, of commercial grade, were prepared and irradiated with thermal neutron fluxes under similar conditions. Usually the thin aluminum foils, as wrappers of the MoO3 powder, were previously cleaned with acetone and air dried to avoid chemical contamination of the molybdenum targets. Targets were irradiated in the Egyptian Second Research Reactor (ETRR-2) at a neutron flux of ~ 1014 n /cm2.s for ~ 4 hours or according to the working schedule of the reactor.

3.2.1. Choice of Al as a wrapper for the MoO3 targets: Usually, for routine production of activation 99Mo the target materials, including MoO3 powder, were packed in quartz ampoules or directly packed into special aluminum irradiation cans. Before canning, the MoO3 target was

64 wrapped with a small piece of thin aluminum foil (of commercial grade) because of the following reasons: 1- Amount of heat energy released via nuclear reactions with thermal and epithermal neutrons: 98Mo (n,γ) 99Mo is very high enough. High thermal conductivity of aluminum metal (2.37 W/cm K) (Mark et al., 1999) enhances dissipation of the released heat accompanying the irradiation process. In case of high neutron fluxes and weights of 98Mo targets, it is recommended to fill the inner space of the outer irradiation can with thin aluminum foils for further enhancement of heat dissipation and to avoid the problems of heat accumulation. 2- 28Al isotope produced during target irradiation via the nuclear reaction 27 28 Al (n,γ) Al is a short-lived isotope (T1/2= 2.25 min). No hazardous 28 radiation due to produced Al radionuclides (E γ = 1779 keV) could be measured after short cooling periods from the end of irradiation (Sandru and Topa 1968; Burrows, 1988; Lide, 1993; Chu et al., 1999; Mostafa, 2002; El-Absy, 2005). 3- Direct transfer of the irradiated molybdenum-99 target with its Al wrapper to the chemical dissolution vessel (i.e dissolver) without dispatching would be available.

4- The aluminum wrapper and the irradiated MoO3 target can be directly dissolved in the digesting medium ( i.e., 5M NaOH solution) conventionally used for processing of the 99Mo- 99mTc couple. 5- The latter offer may avoid possible losses of 99Mo radioactivity by radioactive decay and / or dispersion of the target material powder with consequent contamination of the surrounding atmosphere, radiation hazards, decanning and dispatching time. Cost save of the quartz ampoules and crushers are also additional gains of the use of Al foils as , MoO3 target s wrapper. 6- If it was necessary, aluminum foils of high chemical purity are available with reasonable price compared with the quartz ampoules.

65 3.2.2. Identification of cross-contaminant radionuclides: To detect and identify the contribution of the individual constituents of the target in neutron activation-induced radionuclides, targets of MoO3 powder and of Al foil were separately prepared and irradiated in the ETRR-2 Research Reactor for ~ 4 hours at a neutron flux of 1014 n / cm2.s and analyzed by gamma-ray spectroscopy after different cooling time intervals, starting from the end of irradiation, for different counting rates. Table (3.3) compiles the detected and identified radionuclides and their nuclear characteristics data. The half-lives and decay data of the radionuclides of interest were cited from (Burrows, 1988; Lisken et al., 1990; Arif et al., 1996; Chu et al., 1999).

3.2.2.1. Molybdenum trioxide: Fig. 3.2 (curves a, b and c) shows gamma-ray spectra of the irradiated

0.0144 g MoO3 powder measured after cooling periods of 3, 4 and 6 days for 100s, respectively. The obtained gamma-ray spectra indicate that the 99 high radioactivity of Mo radionuclide (T1/2 = 67 h) dominates over the accompanying cross-contaminants and were readily detected and identified at the main characteristic gamma-ray energy peaks of 140, 181, 366, 739 and 778 keV. The energy-peaks at 281, 823, 880, 920 and 960 keV are interpretting the possibility of pile-up and summation effects which may distort the measured spectra. For instance, the 920 keV peak is due to pile- up of 140.5 and 778 keV quanta and summation of 181, 739 keV pulses, the 880 keV peak arises from pile-up and summation of 140.5 and 739 keV quanta and also the 960 keV peak from summation of 181 and 778 keV quanta. The energy peak at 281 keV is a duplication of the 140.5 keV energy-peaks. These piled-up and summated gamma-ray spectra appear only at high 99Mo radionuclide activity in agreement with the previously published data. (Kessler et al., 1950; Medicus et al., 1951; Varma, and Mandeville, 1954; Bodenstedt et al., 1964; Storg, 1964; Geswemi et al., 1967; Van Eijk et al., 1968). 66 Table (3.3). Radionuclides detected and identified in the MoO3 target and its Al wrapper together with some of their nuclear data characteristics.

Radionuclide T1/2 E γ , keV ( branching %) Production nuclear Abundance cross Source reaction (a), % section (σ), barn 99 98 99 Mo 67 h 140(100), 180(6), 366(2), Mo( n, γ) Mo 24.13 2.7 MoO3 739 (15), 778(12), 822, 920, 960 134 133 134 Cs 2.07 y 563(8), 569(35), Cs ( n, γ) Cs 100 33 MoO3 604(100), 795(90), 134mCs 100 3 3.15 h 801(9), 1365(4) 133Cs ( n, γ) 134mCs 127.4 (100 %) (IT)134Cs 187 186 187 W 24 h 72.3(43), 685(100) W( n, γ) W 28.4 34 MoO3

92m 92 92m Nb 10 d 934 (100), 913, 1847 Mo (n,p) Nb 14.84 …… MoO3 95 94 - 95 Nb 35 d 765 (100 %) Zr ( n, γ, β ) Nb 17 0.185 MoO3 and Al 95Mo (n, p) 95Nb 15.92 ----- 141 140 141 Ce 32.5 d 145.5 (100 %) Ce ( n, γ) Ce 88.48 0.70 MoO3 and Al 51 50 51 Cr 27.8 d 320 (100 %) Cr( n, γ) Cr 4.31 15.9 MoO3 and Al 152 151 152 Eu 12.2 y 122 (60), 244(28), Eu( n, γ) Eu 47.77 7000 MoO3 and Al 344.2(100), 778(45),

1407.5(90) 1400 MoO and Al 152mEu 9.35 h 121.8 (70 %), 344.2 (20 151Eu ( n, γ) 152mEu 47.77 3 %) 963.5 (90 %), 271(0.6 (IT) 151Eu %), 841.6(100 %) 60 59 60 Co 5.2 y 1173 (100), 1332 (100) Co ( n, γ) Co 100 37 MoO3 and Al 60m 59 60m Co 10.5 58.5 (100), 1332.4 (1) Co ( n, γ) Co 100 19 MoO3 and Al min (IT) 60Co 124 123 124 Sb 60.9 d 602 (100 722.8 (10)), Sb ( n, γ) Sb 4275 5.5 MoO3 and Al 1325 (2), 1692 (51) 65 + 64 65 Zn 245 d β 1115.5 (100) Zn ( n, γ) Zn 49 0.47 MoO3 and Al 95 98 95 Zr 60 d 724 (100), 756 (80) Mo( n,α) Zr 24.13. ……. MoO3 94Zr( n, γ) 95Zr 17.40 0.017 Al 140 La 40 h 328(38), 487 (48), 815 139 La( n, γ) 140 La 99.91 8.9 Al (44), 1596 (100) 181Hf 44.6 d 133 (50), 482 (100) 180Hf ( n, γ) 181Hf 0.18 2.7 Al 175Hf 70 d 343.6 (100) 174Hf ( n, γ) 175Hf 35.4 3.5 54Mn 291 d 834 (100) 54 Fe ( n, p) 54Mn 5.84 ----- Al 59Fe 45.1 d 192 (4), 1099(100),1292 58 Fe ( n, γ) 59 Fe 0.31 0.0033 Al (80) 55Fe 2.7 y 5.9 (100) 54 Fe ( n, γ) 55 Fe 5.84 2.8 Al

46Sc 83.3 d 889(100), 1120(100) 45Sc (n, γ) 46Sc 100 22 Al

67 (a) Mo ( 778 keV) Mo ( 778 99 Tc ( 140.5 keV ) keV ( 140.5 Tc

m 99

Mo, ) keV Mo ( 181 99 99 Mo ( 739.2 keV ) Nb (765 keV) Mo ( 822.7 keV )

99 95 99 Tc ( 280.9keV ) ) ( 280.9keV Tc m ) Mo keV ( 366 1Cr (320 keV ) keV (320 1Cr 99 5 99 Nb ( 934.3 keV ) Mo ( 879 keV) Mo ( 920 keV ) Mo ( 960 keV ) Co ( 1173 keV ) Co ( 1332,2keV ) 99 99 92m 99 60 60 units y

Tc ( 140.ke) ( 140.ke) Tc

99 (b)

arbitrar Mo ( 778 keV) Mo ( 778 Mo, ) keV Mo ( 181 , 99 99 99 Tc ( 280.9keV ) ) ( 280.9keV Tc m Mo ( 366 keV ) keV ( 366 Mo Cr ( 320 keV Cr ) keV ( 320 Mo ( 739.2 keV ) Nb (765 keV) Mo ( 822.7 keV ) 99 51 99 99 95 99 er channel p Nb ( 934.3 keV ) Mo ( 879 keV) Mo ( 920 keV ) Mo ( 960 keV ) 99 99 92m 99 Co ( 1173 keV ) Co ( 1332,2keV )

60 60 Counts

Tc ( 140.ke) ( 140.ke) Tc m

99 (c)

Mo, ) keV Mo ( 181 Mo ( 778 keV) Mo ( 778 99 99

99 Tc ( 280.9keV ) ) ( 280.9keV Tc m Mo keV ( 366 ) Cr (320 keV ) keV Cr (320 99 51 99

Mo ( 739.2 keV ) Nb (765 keV) Mo ( 822.7 keV ) 99 95 99 Nb ( 934.3 keV ) Mo ( 920 keV ) keV ( 920 Mo Mo ( 879 keV) Mo ( 960 keV ) Co ( 1173 keV ) Co ( 1332,2keV ) 99 99 92m 99

60 60

Gamma-ray energy, keV

Fig. 3.2. Gamma-ray spectra of 0.0144 g irradiated MoO3 powder measured after (a) 3, (b) 4 and (c) 6 days cooling periods for 100 s.

68 Together with 99Mo radionuclides, the interferring radiocontaminants of 51 95 92m 60 Cr (T1/2 = 27.8 d), Nb (T1/2 = 35 d), Nb (T1/2 = 10.5 d), and Co ( T1/2 = 5.2 y) were detected and identified at the corresponding energy-peaks of 320, 765, 934 and 1173 and 1332 keV, respectively, after short cooling periods. Fig. 3.3 ( curves a, b and c) shows gamma-ray spectra of the same sample measured after long cooling periods of 7, 13 and 75 days for higher counting-rates of 100, 1000 and 2000 s, respectively. The above discussions hold valid for Fig. 3.3 ( curve a ) measured after a cooling time of 7 days for 100 s. Characteristic energy peaks of short-, intermediate - and long - lived radiocontaminants, such as 152Eu, 141Ce, 51Cr, 134Cs, 95Nb, 92mNb, 60Co, 124Sb, 65Zn and 95Zr, were detected and identified after longer cooling periods and counting rates as shown in Fig. 3.3 (curves b and c). The obtained data are in agreement with the previously published work. (Wood and Bowen, 1971; Finck and Mattason, 1976; IAEA, 1995; Boyd, 1997) and specially for 92m, 95Nb and 95Zr with (Qaim and Stocklin, 1973; Qaim 1974; Wolfle and Qaim 1980; Cohen et al., 1983; Zaidi et al., 1985; Qaim 1989; Zaidi et al., 1990; Liskien et al, 1990). The characteristic energy-peak of 124Sb at 602 keV was overlapped with the energy-peak at 604 keV of the relatively highly active 134Cs radionuclide as shown in Fig. 3.3 (curve c). Fig. 3.4 ( curves a, b, c) shows gamma-ray spectra of higher amounts of

0.1 g MoO3 powder measured after cooling periods of one, two and three months, to cover and pass the cooling time periods in Figs. 3.2 and 3.3, for detection time of 100, 300 and 2000 s, respectively. Fig. 3.4 (curve a) indicates that the energy-peaks of 99Mo radionuclide measured after ~ 10 half-lives (one month) decay period are still dominating and completely or partially overlap the energy-peaks of most of the interferring radiocontaminants. On the other hand, gamma-ray energy peaks of the-

(a) Tc ( 140.ke) ( 140.ke) Tc m Mo ( 778 keV) Mo ( 778 99

99 Mo, ) keV Mo ( 181 Nb ( 934.3 ke) Nb 99 99 92m

Tc ( 280.9keV ) ) ( 280.9keV Tc m Mo keV ( 366 ) Mo ( 739.2 keV ) Nb (765 keV) Mo ( 822.7 keV ) Cr 9320Cr keV ) 99 95 99 99 51 99 Mo ( 920 ke) Mo ( 879 keV) Mo ( 960 keV ) 99 99 99 Co ( 1173 keV ) Co ( 1332,2keV ) 65Zn ( 1115 keV ) 60 60

Ce (145.keV) 141 (b)

)

Tc ( 140.ke) Tc Mo ( 778 keV) Mo ( 778 181 keV keV 181 99m ( 99

Mo, Mo Nb ( 934.3 ke) Nb 99 99 92m

Mo ( 739.2 keV ) Nb (765 keV) Mo ( 822.7 keV ) 99 95 99 Cr 9320Cr keV ) ) keV ( 366 Mo 51 99 Co ( 1173 keV ) Co ( 1332,2keV ) 65Zn ( 1115 keV ) 60 60 Mo ( 920 ke) Mo ( 879 keV) Mo ( 960 keV ) 99 99 99 Eu ( 1407.5 keV ) K ( 1460.6 KEv ) 152 40 Counts per channel, arbitrary units

(c)

Cs ( 568.9.keV)

134 Cs (795.3.kevV) Cs (795.3.kevV)

134 Nb ( 765keV ) Nb ( 765keV 95

Co ( 1173 keV ) Co ( 1332,2keV )

65Zn ( 1115 keV ) 60 60 Hf ( 133.15 keV ) Ce ( 145.5 keV ) Cs ( 562.6.keV) Cs ( 604.27.keV) Eu ( 122 keV ) Nb ( 934.3 keV ) 152 181 141 134 134 Eu ( 344 keV ) Hf ( 482 keV ) Eu ( 778 keV ) Cr ( 320 keV ) 92m Zr (724keV) Zr (756 keV) 51 152 181 95 95 152 Sb ( 1692 keV ) Eu ( 1407.5 keV ) K ( 1460.6 KEv ) 152 40 124

Gamma-ray energy, keV

Fig. 3.3. Gamma-ray spectra of the 0.0144 g irradiated MoO3 powder measured after (a)7, (b) 13 and (c) 75 days cooling periods for 100, 1000 and 2000 s, respectively.

Mo ( 929keV ) Mo

(a) Cs ( 568keV ) Cs ( Cs ( 801.8 keV ) Cs 134 Nb ( 912.7 keV ) Nb ( 934.6 keV )

Mo (777.8 keV) 134 Tc (140.5 keV ) 95 95 99 99m .8 keV ) Tc(281 keV) sum. Peak Ce ( 145.5 keV ) Cr (320 keV ) keV Cr (320 keV) (366.2 Mo Mo, Mo ( 181.3 keV ) 99m 99 141 99 51 99

ز Cs ( 562 keV ) Cs ( 604 keV ) Co ( 1173.4 keV ) keV ( 1173.4 Co 134 134 Co 1332 Co Cs ( 795.8 keV ) 60 Mo (739.3 keV ) Nb (765.5 keV) Mo (880keV) 60 99 95 134 99

Nb ( 1847.8 keV ) ) keV Nb ( 1847.8 m 92 units y

arbitrar , ) Cs ( 801.8 keV ) Cs Cs ( 568keV ) Cs (

Nb ( 934.6 keV ) 134 95 134 krV Nb ( 765.8 keV ) Nb ( 765.8 .8 keV ) Co ( 1173.4 keV Co ( 1173.4 keV 95 (b) 1407 5 ز ( 60 Cs (1365 keV) Eu Co 1332 Co Cs ( 562 keV ) Cs ( 604 keV ) Eu ( 121.6 keV ) keV ) 121.6 ( Eu keV ) (145.5 Cr 60 134 152 Cs ( 795.8 keV ) Nb ( 912.7 keV ) Eu ( 344.3 keV ) er channel Zr (756 keV ) 134 134 Cr (320 keV ) 152 141 95 95 134 51 152 Cs ( 1365 keV ) Eu ( 1407.5 keV ) p 134 152 Zn (1115.1 keV ) 65 Sb ( 1692.2 keV ) keV Sb ( 1692.2 124 Counts

( 801.8 keV ) Cs 134 Nb ( 765.8 keV ) Nb ( 765.8

Cs ( 568keV ) Cs ( (c)

134 Co ( 1173.4 keV ) keV ( 1173.4 Co Cs ( 1365 keV ) Eu ( 1407.5 keV) Co ( 1332,8 keV ) keV ( 1332,8 Co 60 60 134 152 Cs ( 795.8 keV ) Eu ( 244 keV ) Nb ( 934.6 keV ) Zn (1115.1 keV ) Eu ( 121.6 keV ) Ce (145. keV ) Eu ( 344.3 keV ) Zr (724 keV ) Zr (756 keV ) Cr (320 keV ) 95 65 95 95 134 153Eu ( 778 keV ) 152 152 141 51 152 Cs ( 562 keV ) Cs ( 604 keV ) 134 134 Sb ( 1692.2 keV ) keV Sb ( 1692.2 124

Gamma-ray energy, keV

Fig. 3.4. Gamma-ray spectra of 0.1 g irradiated MoO3 powder measured after (a) one, (b) two and (c) three months cooling periods for 100, 300 and 2000 s, respectively.

71 radiocontaminants 152Eu, 141Ce, 51Cr, 134Cs, 95Nb, 92mNb, 60Co, 124Sb, 65Zn and 95Zr could be clearly detected and identified in the irradiated solid targets after longer cooling intervals of two and three months. Improved radiocontaminants detection, identification and precision may be achieved for higher counting rates after longer cooling intervals and higher target amount e.g, Fig. 3.4 compared to Figs. 3.2 and 3.3. To compare detection and identification of the irradiated solid targets with their solutions, 1.0 g irradiated MoO3 powder was dissolved in 30 ml 5M NaOH solution. Samples of 0.2, 1.0, 1.0 and 1.2 ml of the obtained solute were radiometerically analyzed. Fig. 3.5 (curves a, b, c and d) shows the corresponding gamma- ray spectra of the radiomolybdate solutes measured after cooling periods of 8 days, one, two and three months, from the end of irradiation, for 200, 200, 300 and 500 s, respectively. Fig. 3.5 (curve a) shows gamma-ray energy peaks of 99Mo radionuclides together with the energy peaks of the short-lived radioisotope 187W. Characteristic energy- peaks of the radiocontaminants of low radioactivity levels such as 95Nb, 152Eu and 134Cs were not completely detected and identified, due to the high radioactivity levels of 99Mo radionuclides. Fig. 3.5 (curves b, c and d) shows gamma-ray spectra of almost decayed (curve b) and of completely decayed 99Mo radionuclide (curves c and d). It is observed that under comparable irradiation and counting conditions, cross-contaminants of the irradiated

MoO3 targets can be more or less detected and identified both in solid and solution of considerable target amount.

3.2.2.2. Aluminum wrapper: Initially, chemical analysis was conducted out by dissolving 0.1 g aluminum foil in 5 ml of concentrated hydrochloric acid, pretreated to obtain 100 ml solution of pH value 1 and then, analyzed by Inductive Coupled Plasma Spectrophotometery for detecting Fe, Co, Mn, Cr, Sc and Ce. ICPS analysis indicated that the concentration of iron in the sample equals to 2.28 72

) ( a )

Tc(140keV)

Nb ( 934.7 keV) 181 keV ( ,99m 92m sum. peak sum. peak

Ce ( 145.5 keV ) Mo Mo 99 141 99

Mo ( 739.1 keV) Mo ( 822.1 keV) Nb ( 912 keV) Mo ( 777.3 keV ) W ( 685.1 keV )

Mo ( 880keV ) Mo (960 keV ) sum. peak Tc(281 keV) sum. peak Mo ( 366.3 keV ) keV ( 366.3 Mo 187 99 99 92m 99 99 99 99 99m

Co ( 1332.9 KEv ) KEv ( 1332.9 Co Co ( 1172.9 keV ) keV ( 1172.9 Co 60 134Cs ( 1365 keV ) keV ( 1365 134Cs 60

)

181.1keV (

Mo Mo ( 140.3 keV ) Ce ( 145.5 keV ) )

99 141 99 ( b )

960 keV ( Nb ( 934.7 ke Cs ( 604.4 keV) Eu ( 778 keV ) Cs ( 795.8 keV) Eu Mo (739.4 keV ) Nb ( 765.8 keV ) Mo (777.3 keV ) Mo ( 880keV ) Co ( 1172.9 keV) Co ( 1332.9 KEv) 60 134 99 95 99 152 134 99 92m 152 Mo ( 366.3 keV ) Cr ( 320 keV ) 60 51 99

Cs ( 569.5 keV ) keV ( 569.5 Cs 134 ( c )

Nb ( 765.8 keV ) ( keV Nb 765.8 95 Counts per channel, arbitrary units Eu ( 121.6 keV ) Ce ( 145.3 keV ) Cs ( 562.5 keV ) keV ( 562.5 Cs ) keV ( 604.5 Cs Nb ( 934.7 ke) 152 141 134 134 Co ( 1333.3 KEv) Co ( 1173.6 keV) Eu ( 344 keV ) 92m 60 Cr ( 320.3 keV ) 60 Eu ( 778 keV ) keV Eu ( 778 keV ( 795.8 Cs 51 152 Zr (756 keV ) keV Zr (756 95 152 134

) Cs ( 795.4 keV keV ( 795.4 Cs Nb ( 765.8 keV ) keV ( 765.8 Nb Cs ( 569keV ) 134 95 keV 134

344 ( d ) ( Nb ( 934.7 ke) Co ( 1173.6 keV) 92m Eu Cr ( 320.3 keV ) 60 Eu ( 121.6 keV ) Ce ( 145.3 keV ) 51 152 152 141 ) keV Eu ( 778.4 Co ( 1333.3 KEv) Zr (756 .4 KeV ) .4 Zr (756 Cs ( 562.5 keV ) keV ( 562.5 Cs ) keV ( 604.5 Cs 95 152 60 134 134

Gamma-ray energy, keV

Fig. 3.5. Gamma-ray spectra of sodium molybdate solute of different volumes, cooling

periods and detection time: (a)) 0.2 ml, 8 days and 200 s (b) 1.0 ml, one month

and 200 s (c)1.0 ml, two months 300s and (d) 1.2 ml, three months and 500 s,

respectevely

73 ppm, with unbootable concentrations of the other chemical contaminants. This means that iron only was the detectable chemical impurity in the aluminum foil at the rate of ~ 1.37 mg Fe in the pieces of 0.6 g aluminum wrapper. Two targets each of 0.6 g aluminum foil were irradiated in the ETRR-2 research reactor. An irradiated Al target was dissolved in 30 ml 5 M NaOH solution. Fig. 3.6 ( curves a and b) shows gamma-ray spectra of 1.0 ml of the obtained Al solute measured after a cooling time of one month for 500 s and of the o.6 g aluminum foil measured after a cooling time of 20 days for 1000 s, respectively. Fig. 3.6 (curve a) shows that except for the gamma-ray energy peaks of 134Cs, 92mNb and 99Mo radionuclides, the energy peaks of 141Ce, 51Cr, 152Eu, 95Nb, 95Zr, 65Zn, 124Sb, and 60Co radionuclides were detected and identified in the irradiated Al target as well as in the irradiated MoO3 targets even at shorter cooling period. The short-lived 140La radioisotope was detected and identified after short cooling time at a higher counting rate Fig. 3.6 (curve b). Stable chemical impurities of the aluminum foil introduce additional detectable contaminant radionuclides into the 99Mo-molybdate (VI) solute, such as 175,181Hf, 140La, 54Mn, 59Fe, 55Fe and 46Sc. Fig. 3.6 ( curves a and b) are more or less similar, taking into consideration Al concentration and other counting conditions. The detected radionuclides and their nuclear data are compiled in Table (3.3).

3.2.3. Sources of contaminant radionuclides: However target irradiation for ~ 100 h with high neutron fluxes would reasonably increase the total amount of 99Mo radioactivity, short half-life cross-contaminant impurities will increase proportionally, too. Irradiation of 98Mo isotopically enriched targets will increase the specific activity of 99Mo by a maximum factor of times four (natural isotopic abundance of 98Mo in the Mo targets is ~ 24 %) and decrease the expected level of radioactive niobium and zirconium impurities (Zaidi et al., 1990; Lisken et al., 1990), but on

( a ) Cr (145.6 KeV)

141

) units

192 KeV ( y Fe ( 141 KeV) Fe 59 59 Hf (482 KeV) KeV) Hf (482 L a(815 keV) Eu (344.5 KeV) Mn (834.6 KeV) (834.6 Mn KeV) Sc (889 Fe (1292 KeV) KeV) Fe (1292 Cr (320 KeV) Fe(1099 KeV) Sc(1120.8 KeV) 181 140 54 46 59 60Co (1332 KeV) KeV) (1332 60Co 51 152 59 65Zn (1115 KeV) 46 60Co (1173 KeV )

arbitrar ,

( b) er channel

Hf ( 133 keV ) 181 Ce ( 145.5 KeV)

41 La ( 328.8 KeV) La ( 328.8 )

) Zr (756KeV) Zr (756KeV) 140 Eu (778 KeV) Eu (778 Counts 95 KeV 152 Fe (1099 KeV) KeV) Fe (1099 1120Sc ( KeV) KeV) (1173.2 Co C Hf ( 482 KeV ) La 9 487 keV ) 59 46 60 Fe( 1292 KeV) KeV) (1333 Co 58 181 140 344.5 192 keV 59 60 ( ( Fe (142 keV ) Eu ( 121.8 KeV) 59 Fe Fe Sb (602 KeV) KeV) Sb (602 Eu 152 59 Cr ( 320 KeV) 124 51 152 L a(815 keV) a(815 L Mn (834.6 KeV) KeV) (834.6 Mn KeV) Sc (889 Zr ( 724.1 KeV) Nb (765 KeV) Kr ( 2011 KeV) KeV) Kr ( 2011 La (1596 KeV) KeV) (1596 La 95 95 140 54 46 87

Sb (1436 KeV) KeV) Sb (1436 140 124 Sb ( 1692Sb ( KeV) 124

Gamma-ray energy, keV

Fig. 3.6. Gamma-ray spectra of (a) 1.0 ml of radioactive aluminum solute measured after a cooling period of one month for 500 s and (b) 0.6 g Irradiated aluminum foil measured after a cooling period of 20 days for 1000 s.

75 the other hand it considerably increases the production cost of the gel type 99Mo / 99mTc generators. As long as the radioisotopes of hafnium-175 and

181 were not detected and identified in the irradiated MoO3 targets, it may be concluded that the MoO3 powder dose not contain stable chemical impurity of Zr and the detected 95Zr radionuclide is artificially produced from the 98Mo stable isotope via the nuclear reaction 98Mo (n,α) 95Zr. However Fe is present in the Al foil in a measurable amount (2.28 mg / g Al) and the other chemical contaminants were under the detection limit of the ICPS technique, the high specific activity contribution of 141Ce, 51Cr, 152Eu, 181,175Hf, and 46Sc are due to their highly effective total neutron- activation cross-sections (= a ×σ), and / or the presence of very short-lived precursors, such as 60mCo (IT) 60Co and 152mEu (IT) 152Eu etc. (Table 3.3). For example, the detectable radioactivity of 59Fe is due to the relatively high concentration of Fe in the Al foil compared to the other stable contaminants. Irrespective of the high concentration of elemental Fe in the target material (1.37 mg) compared to the unbootable other elements, it has very low activation cross section (σ = 0.0033) and low abundance (a = 0.31 %). Contrary to 59Fe, 60Co has unbootable elemental concentration but high abundance of stable isotope 100 % 59Co, high activation cross-section of 37 barn for the nuclear reaction: 59Co (n,γ) 60Co and an additional production route: 59Co( n, γ) 60mCo followed by isomeric transition decay with a half- life of 10 min. (97 % of 60mCo decays to 60Co) with consequent increase in the specific activity of the long-lived 60Co. Similar accounts are more or less valid for 152Eu and 134Cs radionuclides. Longer irradiation periods ( ≥ 100 h) results in exponential gross of the 99Mo radioactivity and more or less linear gross in the radioactivities of longer half-life cross-contaminant radionuclides. At comparable irradiation and counting conditions, detection of radioactive impurities in the irradiated targets depend on the amount and

76 the corresponding activation cross section (Wood and Bowen, 1971; Qaim et al., 1973, 1974 and 1989; Finck and Mottason, 1976; Wolfle and Qaim, 1980; Cohen, 1983; Zaidi et al., 1985 and 1990; Moore, 1987; Lisken et al., 1990; IAEA, 1995; Boyd, 1997). In other words, the area under the characteristic gamma-ray energy peak of a detected radiocontaminant depend on 3 factors (i) concentration as an elemental impurity in the target (ii) its isotopic abundance i.e, elemental ratio (iii) its activation cross section. Some factors may lead to absence or overlap of one or more of the characteristic energy-peaks of some contaminant radionuclides with consequent bad identification in the irradiated target of 98Mo and its Al wrapper such as: (i) low gamma-ray energy as in 55Fe and 187W and low- energy peak abundance as in the 192 keV of 59Fe (4 %) (ii) interference between energy peaks due to converging characteristic values of gamma- ray energies, e.g. the overlap of characteristic-gamma- ray energies of 99Mo and 141Ce at 145 keV, 95Zr at 724 and 756 and 95Nb at 765 keV and of 134Cs and 124Sb at 602 and 604 keV (iii) absence of gamma-ray emission (iv) very low concentration in the target material as of 65Zn, 175Hf and 95Zr (v) 24 28 short half-life of the radionuclide as in Na (T1/2 = 15 h) and Al (T1/2 = 23 24 27 24 2.25 min) via the nuclear reactions Na (n, γ) Na, and Al (n,α) Na and 27 28 60m 134m 152m Al (n, γ) Al and Co, Cs, Eu (Liskien et al., 1990). From the above data and discussions, cross-contaminant radionuclides induced in the neutron irradiated MoO3 powder wrapped by Al foil targets may be originated from (Table 3.3): 1- Thermal neutron activation of the chemical impurities present in the target materials via ( n, γ) nuclear reactions such as 140Ce ( n, γ) 141Ce, 50Cr ( n, γ) 51Cr, 133Cs ( n, γ)134m,134Cs, 59Co ( n, γ) 60m,60Co, 64Zn ( n, γ) 65Zn, 186W( n, γ) 187W, 123Sb ( n, γ) 124Sb, 151Eu ( n, γ) 152m,152Eu and 94Zr ( n, γ) 95Zr.

77 2- Fast neutrons reactions of the type (n,p), (n,α) and (n,2n) with stable isotopes of the targets. For example, *Nb and *Zr radionuclides are produced via the irradiation of stable Mo isotopes by fast neutrons according to the nuclear reactions: 92Mo (n, p) 92mNb, 95Mo (n, p) 95Nb and 98Mo (n, α) 95Zr (Zaidi et al., 1990). Fast neutrons reactions are of energy-threshold type, as well as those of a cyclotron charged-particles nuclear reactions. Another example of fast neutrons is the production of 54Mn via the nuclear reaction 54Fe(n,p)54Mn (Moore, 1987; Burrows 1988; Liskien et al., 1990; Lide, 1993; Arif 1996; Chu, 1999). 3- Decay of precursor radionuclides such as the β- radioactive decay of 95Zr (β-) 95Nb (Wood and Bowen, 1971; Finck and Mattason, 1976; Moore, 1987; IAEA, 1995; Boyd, 1997 and El-Absy 2002) and the isomeric transitions (IT) of 134mCs, 60mCo and 152mEu to 134Cs, 60Co and 152Eu respectively (Burrows, 1988; Lide, 1993; Chu, 1999;). The resulting contaminant radionuclides, their source, radiometreic methods of identification and nuclear characteristics are more or less convenient with the published data (Wood and Bowen, 1971; Qaim and Stocklin, 1973; Qaim, 1974; Finck and Mottason, 1976; Wolfle and Qaim, 1980; Cohen et al, 1983; Zaidi et al., 1985; Moore, 1987; Qaim, 1989; Zaidi et al., 1990; Liskien et al., 1990; IAEA, 1995; Boyd, 1997).

3.2. Preparation of the 99Mo-molybdate radiotracer solutions (targets dissolution): Usually, target dissolution for preparation of the 99Mo-molybdate (VI) radiotracer solution was carried out after a cooling period of 8 days, from the end of irradiation. The irradiated target, consisting of 1.0 g MoO3 powder wrapped with 0.6 g Al foil containing 1.37 mg Fe was directly

78 transferred into the dissolution vessel followed by the addition of 30 ml 5 M NaOH solution. In preliminary dissolution experiments, samples of inactive targets consisting of 1.0 g MoO3 wrapped with 0.6 g Al foil were digested in NaOH solutions of different volumes and concentrations (i.e, 15, 20, 25 and 30 ml of 1, 2, 3 and 5 M NaOH). It was found that: 1- While 30 ml 1 M NaOH solution didn’t affect the target dissolution, 30 ml 2 and 3 M NaOH solutions achieved complete but slow target dissolution in ~ 20 and 6 h, respectively. 2 - Target materials dissolved in volumes less than 30 ml 5M NaOH solution formed condensed clouds of Al(OH)3 gel matrix due to rapid coagulation encompassing all reactions and mechanisms resulted in the overall process of particles growth (flock formation) and particles aggregation during the alkali treatment. 3- It was found that 30 ml 5 M NaOH solution achieved complete and / or an apparent complete dissolution of the Mo / Al targets in ~ 15 min. The dissolution reaction was remarkably exothermic with evolution of molecular hydrogen. The final products were in the form of black coloured solutions. 4- Unless otherwise stated, for routine dissolution, the irradiated targets were digested for ~ 15 min in 30 ml 5M NaOH solution. Fast dissolution of 99 the irradiated MoO3 targets may ensure the least loss of Mo radioactivity 99 due to radioactive nuclear decay of the short-lived Mo radionuclides (T1/2 = 67 h) with time. 5- The final concentration of NaOH in the product solution (after dissolving inactive 1.0 g MoO3 powder wrapped with 0.6 g Al wrapper, containing 1.37 mg Fe was determined by acid / base titration method using 12 M nitric acid as the titrating agent. The final alkali concentration was found to be ~ 4 M NaOH.

79 Dissolution of the irradiated molybdenum trioxide target with the aluminum wrapper can be submitted either by acid or alkali methods. The choice of an acid (e.g, HNO3, HCl and H2SO4) or alkali (e.g. NH3, NaOH and KOH) dissolution method depends on factors such as: (i) chemical and / or elemental composition of the irradiated target, (ii) the applicable separation and purification methods (e.g., precipitation, co-precipitation, adsorption, ion-exchange, extraction with organic solvents, distillation, etc.), (iii) radionuclides to be separated and / or recovered and their chemical species, (iv) addition of catalyst, oxidant and / or other chemical reagents during the dissolution process, and (v) the required time of dissolution is an important factor to minimize the time of exposure and loss of 99Mo via radioactive decay. The following comments and discussions explore the feasibility of the acid / base process applicable to direct transfer and dissolution of the irradiated MoO3 powder with its aluminum wrapper:

1- The aluminum foil and the MoO3 powder are not easily dissolved in concentrated and diluted mineral acid solutions. However nitric acid is an acceptable dissolution medium for MoO3, the dissolution of aluminum is normally inhibited. This passivity can be avoided by addition of mercury as a catalyst which changes the chemical contents of the product molybdate solute and causes mercuric toxicity. (Boeglin et al., 1961; Roesmer, 1970; Otero et al., 1977; Munze et al., 1984; Mostafa 2002). 2- In the case of acid dissolution, evolution of high concentrations of atomic hydrogen will result in reduction of cations of higher oxidation state including Mo (VI) to lower oxidation states MoO2+. Molybdenum (VI) precipitates as hydrated molybdenum trioxide MoO3.2H2O at pH value ≤ 0.9 then, it is reduced to molybdyl cation [MoO]2+ at pH value lower than 0.9 (Seadden, and Ballou. 1960; Aveston, 1964; Mitchell, 1990 and 1990; Lee, 1991; Greenwood and Earnshaw,1998; Mostafa 2002).

80 3- Concentrated ammonia solutions, NH4OH, did not dissolve Al foil into aluminum hydroxide. As well as, ammonium molybdate is sparingly soluble in dilute acid solutions. 4- Concentrated NaOH solutions were examined for dissolution of aluminum metal and alloys (Lewis, 1971; Ali, 1987). It was found that dissolution occurs from solutions between 3-6 M NaOH. In these media most of the previously radiometeric detected and identified microcomponents of elemental Fe, Mn, Eu, Ce, La, Cr and Sc radioimpurities will be converted, under controlled chemical conditions, to hydroxides, such as Fe(OH)2,

Fe(OH)3, Mn(OH)3, Eu(OH)3, Ce(OH)3, Ce(OH)4, La(OH)3, Cr(OH)3 and

Sc(OH)3, readily precipitated and / or co-precipitated by addition of a macrocomponent scavenger, such as Fe3+ and Al3+ ions (Agasyan, 1980; Lee, 1991; Greenwood and Earnshaw, 1998). Simultaneously, the digested

MoO3 powder and its Al wrapper form soluble molybdate (VI) and aluminate anions according to the following equations (Foster et al, 1955; Etheringtone, 1958; Agasyan, 1980; Lee, 1991; Greenwood and Earnshaw, 1998; Pajunen, 1999):

+ 2- MoO3 + 2NaOH → 2Na + [MoO4] + H2O (soluble)

Al + Na OH + H2O → NaAlO2 + 3/2H2↑ (soluble)

Meanwhile, concentrated sodium hydroxide solution may dissolve the 1.37 mg elemental Fe impurity, from the aluminum foil, into a somewhat white amphoteric precipitate of Fe(OH)2, soluble in excess of concentrated sodium - hydroxide solution into hydroxy ferrous hydroxide anion Fe(OH)3 according to the following reaction:

2+ - Fe + 2OH Fe (OH)2 ↓

- - Fe (OH)2 + OH Fe(OH)3 (soluble) 81 - Fe(OH)3 becomes dark black on hot dissolution due to formation of FeO species in solution (Cotton and Hart, 1975; Cotton, 1979 and 1980). 5- At high neutron fluxes, some insoluble radiation-induced 99Mo reduced species may remain in the bottom of the dissolution flask. Addition of H2O2 solution will ensure complete dissolution and oxidation of the reduced molybdenum species to Mo(VI) anions (Boyd, 1982; Evans, et al 1986; Moor, et al., 1987; Lee, 1991; Greenwood and Earnshaw, 1998; Mostafa, - 2006) together with oxidation of soluble Fe (OH)3 species into insoluble Fe(III) minerals (Cotton, 1979 and 1980; Lee, 1991; Greenwood and Earnshaw, 1998). 6- Thereafter, alkali dissolution / acid treatment of the 99Mo-molybdate (VI) solutes with HNO3 acid up to pH values in the range from 10 to 5 facilitates precipitation of soluble sodium aluminate anions into aluminum hydroxides:

pH ≤ 10 to 5 - + 2AlO2 + 2H + 2 H2O 2 Al (OH)3 ↓

Normal molybdate (VI) anions will be transformed as predominant heptamolybdate (VI) anions, with decreasing the solution pH value to 5

(Greenwood and Earnshaw, 1998; Pajunen, 1999):

pH 5 - 3.5 2- 6- [MoO4] [Mo7O24] pH ≥ 10 n. molybdate (VI) anions heptamolybdate (VI) anions

3.4. Purification of the 99Mo-molybdate (VI) solute via in-situ precipitation of 59Fe-Fe (III) minerals: Neutron activation of elemental Fe produces 55Fe and 59Fe 59 radioisotopes. Fe radionuclide (T1/2 = 45 day and Eγ = 192 (4 %), 1099 (57 %) and 1292 keV (43 %)) is a favorable radiotracer to follow the chemical behavior of Fe (II) iron oxidation and precipitation in the form of Fe (III)

82 55 iron minerals from Na2MoO4 solution compared to Fe (T1/2 = 2.7 y and Eγ =

5.9 keV (100 %)). After a cooling period of 8 days, the irradiated 1.0 g MoO3 with its 0.6 g aluminum wrapper containing 1.37 mg Fe from the Al foil were digested in 30 ml 5M NaOH solution for ~ 15 min until complete and / or

apparent complete dissolution took place. Addition of 0.5 ml 10 % H2O2 solution ensured complete dissolution and oxidation of the reduced molybdenum species (if present) to Mo(VI) oxidation state (Boyd, 1982 and 1987; El-Absy, 1990; Mostafa, 2006) as well as oxidation of Fe(II) iron into Fe(III) iron according to the following equation (Cotton, 1979 and 1980; Lee, 1991; Greenwood and Earnshaw, 1998):

2Fe (OH)2 + H2O2 2Fe (OH)3 ↓

Addition of H2O2 to the reaction mixture solutiom produced local spots of pale pink colloidal aggregates (i.e, floks) which were readily disappeared with strong mixing of the mixture solution. It is a consequence of enhanced repulsion forces created between the negative charges of colloidal Fe(III) nuclei and the surrounding high concentrations of OH- anions from NaOH solution. In other words, strong mixing of the reaction mixture solution may results in breaking down (tearing) of the locally created suspension of oxidized Fe(II) species into very sparingly soluble Fe(III) species in solutions (solubility of Fe (II) = 10-15 and that of Fe (III) = 10 -38) (Agassyan, 1980). Peptization (the passage into solution of precipitates formed in coagulation) occurs at a definite rate, when there is a sufficient amount of peptizer. The process occurs at first very rapidly, and then gradually slows down. Stirring of the system promotes peptization where penetration of the peptizer into the aggregates is accelerated and helps particles to tear away from one another and pass into solution. After complete addition of H2O2 solution with continuous mixing, a clear colorless solution of soluble sodium aluminate and 99Mo-molybdate (VI) containing highly dispersed ferric (III) colloid in 4M

83 NaOH sustained stable for ~ 120 min. It may be due to the formation of highly - dispersed [Fe (OH)3].xOH fine particles in the mixture solution after adsorption of OH- ions (Charles et al., 1976; Cotton and Wilkinson, 1979; Agasyane 1980):

- - Fe (OH)3 + x OH [Fe (OH)3].xOH

Figs. 3.7 (curves a, b , c and d) shows gamma-ray spectra of 0.2, 1.0, 1.0 and 1.2 ml of the oxidized 99Mo-molybdate solute measured after decay periods of 8 days and, one, two and three months from the end of irradiation for 100, 200, 300 and 2000 s, respectively. It is observed that increasing the cooling time (e.g, ≥ 1 month), the counting rate and the sample volume (from 0.2 to 1.2 ml) improve the detection and identification of 59Fe radionuclide in the 99Mo-molybdate (VI) solute. On the other hand, short cooling periods (≤ 8 days) mostly favor 99Mo radionuclide detection and identification where its characteristic energy peaks overlap the characteristic energy-peaks of low level radioactive cross-contaminants. Later on, standing for ~ 2-3 hours at room temperature a pale-pink colloidal suspension of very fine particles (not easily visual by naked eyes) was produced. It may be of hydrated ferric oxides and / or oxyhydroxides, depending on the reaction conditions (Agasyane 1980; Cotton and Wilkinson 1979). During this time interval, the previously highly dispersed colloidal particles of Fe (III) iron may be neutralized by the attachment of positive cations from solution and coagulate with the growth in particles size (Agasyane 1980). The formed colloidal suspension was collected and separated from the supernatant solution by centrifugation for ~ 15 min at a speed of 6000 rpm and filtration with a 0.45 µm Millipore filter. Samples of the 99Mo-molybdate

(VI) solute, the supernatant and the separated Fe(OH)3 precipitate were radiometerically analyzed after different cooling time intervals.

Tc( 140 keV)

181 keV ( 99m

Mo, 99 99Mo

Nb(934keV) (a) Mo(960 keV) Mo (740 keV) Mo (778 keV) Mo (822 keV) Mo(880 keV) Mo(920 keV) 99 99 99 99 99 99 92m Tc( 281 keV)

Mo( 366 keV) 99m 99 Co (1173 keV) Co (1332 keV) 60 60 Tc( 140 keV)

99m

Mo, 99 99Mo (181 keV 366.3 keV keV 366.3

( (b) units Nb(934keV) y Mo(960 keV) Mo (740 keV) Mo (778 keV) Mo (822 keV) Mo(880 keV) Mo(920 keV) Cr ( 320 keV Cr ) keV ( 320 Mo Fe ( 1099 keV) Sc (1120 keV) Co (1173 keV) Fe ( 1292 keV) Co (1332 keV) 99 99 99 99 99 99 92m 60 51 99 59 46 60 59 Cs (604 keV ) keV Cs (604 Hf (487 keV) Fig 134 181 arbitrar ,

)

604. keV er channel ( p Cs Cs ( 562.42 keV ) Cs ( 569.42 keV ) 134 134 134 (c) Zn 91115 keV Fe ( 1099 keV) Sc (1120 keV) Co (1173 keV) Fe ( 1292 keV) Co (1332 keV) 60 59 65 46 60 59 Nb ( 934.3 keV ) Cs ( 795.6 keV ) Sc (889.2 keV ) Ce ( 145.1 keV ) keV Ce ( 145.1 Nb (765.6 keV ) 46 Counts 95 134 92m 141 Hf (487 keV) 51 Cr (320 keV ) 181

)

) 192.3 keV ( 934.3 keV (

Eu ( 121.7 keV ) Ce ( 145.5 keV ) (d) Zn 91115 keV Fe Fe Fe ( 1099 keV) Sc (1120 keV) Co (1173 keV) Fe ( 1292 keV) Co (1332 keV) 60 152 141 59 59 65 46 60 59 ) Nb Cs ( 604. keV ) Eu (343.8ke) Hf (344 keV) Hf (487 keV) Cs ( 562.42 keV ) Cs ( 569.42 keV ) Cs ( 795.6 keV ) Sc (889.2 keV ) Nb (765.6 keV ) Cr (320 keV ) 46

51 152 175 181 134 134 95 134 92m 134

Gamma-ray energy keV

Fig. 3.7. Gamma-ray spectra of (a) 0.2 (b) 1.0 (c) 1.0 and (d) 1.2 ml of 99Mo- molybdate (VI) solute measured after cooling periods of 8 days and one, two and three months for 100, 200, 300 and 2000 s, respectively.

85 Fig. 3.8 ( curves a, b and c ) shows gamma-ray spectra of 0.2 ml of the 99Mo-molybdate (VI) solute, the formed Fe(III) mineral precipitate and 0.2 ml of the supernatant solution after separation of the formed Fe(III) precipitate measured after a cooling period of 8 days for 100 s, respectively. Inspection of the corresponding gamma-ray spectra indicated absence of the three gamma-ray energy-peaks of 59Fe radionuclide from the two molybdate (VI) solutions, due to the high radioactivity level of 99Mo radionuclide in the solutions. On the other hand, concentration of the 59Fe radionuclide into the formed Fe(III) precipitate enabled its detection and Identification at the two more abundant gamma-ray energy peaks of 1099 and 1292 keV. Disappearance of the 192 keV energy peak in the formed Fe(III) precipitate is due to incorporation of relatively high level 99Mo radioactivity and its low abundance. Together with 59Fe, some characteristic gamma-ray energy peaks of 140La, 95Nb, 46Sc, 92mNb and 60Co radionuclides were detected and identified onto the formed precipitate. It is concluded that, clear detection and identification of the 59Fe radionuclide both in the 99Mo-molybdate (VI) solute and onto the formed Fe(III) precipitate (before and after washing) must be enhanced almost or completely at low levels of 99Mo radioactivity or after complete decay for high counting rates. For example, measuring after cooling periods of one, two or three months from the end of irradiation for 100, 200 or 2000 s, respectively. Qualitative and / or quantitative radiometeric assessment of 59Fe in solution as well as onto the formed Fe(III) precipitates must be conducted out after cooling periods ≥ one month.

(a) Tc ( 140.5 keV) 99m

Mo, Mo (181.2 keV) 99 99

) Mo (739 keV) Mo (778 keV) Mo (820 keV) Mo (880 keV) 99 99 99 99 Mo (366.5 keV ) keV (366.5 Mo 99 ((281. keV) 960 keV ( Nb (912 &934.4 keV) &934.4 (912 Nb 99mTc m Mo 92 99 Co (1332.2 keV) Co ( 1173.2 keV) keV) ( 1173.2 Co 60 60

units y 5.keV )

14 (b) ( Ce 141

arbitrar , La( 815 keV) La(

140 Tc ( 140.5 keV) 99m Nb (913 keV) Nb (934.3 keV) Sc( 889 KEV) Mo, Mo (181.2 keV) 46 92m 92m 99 99 er channel p Fe ( 1099 keV) Sc ( 1120 keV0 Co (1173 keV ) Mo ( 739.3 keV) Mo ( 777.6 keV) 59 46 60 La( 487 keV) La( 328 keV) 99 95Nb ( 765.6 keV ) 99

Mo (366.5 keV ) Fe ( 1292 keV) Co ( 1332 keV) 40 140 99 59 60 La ( 1597.3 keV) Nb (1847.6 keV)

140 92m Counts

Tc ( 140.5 keV) 99m (c) Mo (366.5 keV ) keV (366.5 Mo Mo, Mo (181.2 keV) 99

99 99

) Mo ( 739.3 keV) Mo ( 777.6 keV) Mo ( 822.8 keV) Tc((281. keV) 99 99 99 960 keV ( 99m Mo ( 920 keV) Mo Sc( 889 KEV) 46 99 99

Gamma-ray energy, keV

Fig. 3.8.Gamma-ray spectra of (a) 0.2 ml of the 99Mo-moloybdate (VI) solute (b) the formed Fe(III) minerals and (c) 0.2 ml of the supernatant solution measured after a cooling time of 8 days for 100 s.

87 Figs. 3.9, 3.10 and 3.11 indicate that 59Fe radionuclide was partially distributed between the 99Mo-molybdate (VI) solute and the washed precipitate of the formed Fe(III) iron minerals via in-situ precipitation of

Fe(III) iron from the solution by oxidation of Fe (II) iron with H2O2. Fe(III) iron precipitate acted as an isotopic carrier for 59Fe radionuclide and non isotopic scavenger for the other cross-contaminating radionuclides from the 99Mo-molybdate (VI) solution. Radiometeric analysis of the net area under the characteristic energy peaks of 59Fe in any of Figs. 3.9, 3.10 and 3.11 indicates that very fine colloidal particles together with sparingly soluble Fe (III) species may be penetrated the 0.45 µm Millipore filter into the 99Mo-molybdate (VI) supernatant. The corresponding counting rate net area indicate that ~ 32.05 % 59Fe radionuclide passed the Millipore filter (~ 0.4384 mg Fe), with ~ 68 % (~ 0.9316 mg Fe) elimination, into the 99Mo- molybdate (VI) solute. The high concentration of 4 M NaOH (i.e. OH- anions) may contribute for the observed high degree of dispersion of the - - formed Fe (III) minerals due to formation of soluble Fe(OH)4 , (FeO2) and 3- 99 / or [Fe(OH)6] anions (Cotton and Wilkinson, 1979 ) in the Mo- molybdate (VI) solute.

3.4.1. Factors affecting 59Fe elimination: The degree of dispersion and the time required for nucleation, neutralization, coagulation and precipitation of the formed colloidal particles of Fe(III) iron are affected by factors such as solution pH, concentration and chemical composition, temperature, concentration of hydrolysable ions, oxidation state and Fe(III) : Fe(II) molar ratio in solution (Agasyane, 1980; Ishikawa et al 1986 and 1993; Kandori et al, 1992; Gregory, and Duan, 2001).

Cs (795 keV ) Zr ( 724 keV ) Mo ( 739 keV) Zr ( 756 keV ) Mo (777.8 keV) Tc(140 keV) 95 99 95 99 134 95Nb ( 765 keV )

99m Mo, Mo (181 keV) Sc ( 1120 keV0 99 99 46 ( a ) 920 keV 0

(

Nb (913 keV) Co ( 1332 kKeV ) Tb (879 keV ) Fe ( 1292 keV) Mo Sc( 889 KEV) 60 160 46 92m 99 Zn(1115 keV) Fe ( 1099 keV) Co (1173 keV 0 Cs (604 keV ) keV Cs (604 9 59 65 60 Cr ( 320 keV Cr ) keV ( 320 keV (366.3 Mo 134 51 99 units y

arbitrar ( b ) ,

Nb (913 keV) keV) Nb (913 Nb (934.3 Sc( 889 KEV) 889 KEV) Sc(

keV) keV) 46 92m 92m Do (1173 keV 0 Fe ( 1099 keV) Sc ( 1120 keV0

Eu ( 121.7 keV ) Ce ( 145.6 keV ) Fe ( 192 keV 0 59 46 60 Fe ( 1292 keV) Co ( 1332 kKeV ) Co ( 1332 kKeV ) Nb ( 765.7 keV ) keV 765.7 Nb ( 152 141 59 60 95 Eu ( 344.3keV ) Cr (320 keV) keV) Cr (320 er channel 9 51 152 Eu ( 1407.5 keV ) p 152 Nb ( 1847.7 keV ) ) keV Nb ( 1847.7 m 92 Counts

Tc ( 140.5 keV)

Cs (795 keV ) Zr ( 724 keV ) Mo ( 739 keV) Zr ( 756 keV ) Mo (777.8 keV)

99m ( c ) 95Nb ( 765 keV ) 95 99 95 99 134 Mo, Mo (181.2 keV) 99 99 Sc ( 1120 keV0 46 Cs (604 keV ) keV Cs (604 Cr ( 320 keV Cr ) keV ( 320 keV (366.3 Mo Tb ( 880 keV ) 51 99 134 Mo ( 920 keV 0 Fe ( 1292 keV ) Co ( 1332.8 keV ) Zn(1115 keV) Fe ( 1099 keV) Co (1173 keV 0 160 99 50 60 59 65 60

Gamma-ray energy, keV

99 Fig. 3.9. Gamma-ray spectra of (a)1.0 ml of the Mo-molybdate (VI) solute (b) the Fe(III) precipitate after washing and (c) 1.0 ml of the supernatant solution measured after a cooling period of one month for100s

Sc (1120.3 keV )

46 ( a )

Fe (1291.7 keV ) Co (1332.6 keV ) Zn (1115keV ) Fe ( 1099.1 keV ) Co (1173.1 keV ) Nb ( 934.3 keV ) Cs ( 795.6 keV ) 59 60 59 65 60 Nb (765.6 keV ) Sc (889.2 keV ) Ce ( 145.1 keV ) keV Ce ( 145.1 Cs ( 604.42 keV ) 95 134 46 92m 141 134 51 Cr (320 keV ) Eu ( 1407.5 keV ) keV ( 1407.5 Eu 152

units y

( b )

arbitrar Fe (1291.7 keV ) Co (1332.6 keV ) ,

59 60 Fe ( 1099.1 keV ) Sc (1120.3 keV ) Co (1173.1 keV ) Nb ( 934.3 keV ) Ee ( 121,9KEv ) Ce (145.6 keV ) Fe ( 192 keV ) 59 46 60 Sc (889.2 keV ) 152 141 59 Nb (765.6 keV ) 46 92m

95 54Mn (834.4 keV ) Ee ( 344.3 KEv ) 51 Cr (320 keV ) 152 Eu ( 1407.5 keV ) keV ( 1407.5 Eu 152 er channel p

Counts

3 ( c )

S(1120.3keV ) S(1120.3keV

Hf ( 133.1 keV ) 133.1 ( Hf Hf ( 482 keV ) Cs ( 795.6 keV ) Cs ( 569 keV ) Cs ( 604.42 keV ) Cs ( 562k keV ) Fe (1291.7 keV ) Co (1332.6 keV ) 181 4 34 34 134 181 59 60 Fe ( 1099.1 keV ) Co (1173.1 keV ) Sc (889.2 keV ) 59 65 Zn ( 1115.1 k 60 46 51 Cr (320 keV )

Gamma-ray energy, keV

Fig. 3.10. Gamma-ray spectra of (a) 1.0 ml of the 99Mo-molybdate(VI) solute, (b) the Fe(III) precipitate after washing, (c)1.0 ml of the supernatant solute measured after a cooling period of two months for 200s

( a )

)

Eu ( 121.7 keV ) Ce ( 145.5 keV ) 604.2 keV Fe (192.3 keV ) ( units 152 141 59 Fe (1099 keV ) Sc (1120.3 keV ) Co (1173.1 keV ) Eu ( 1407.5 keV ) keV ( 1407.5 Eu Cs ( 1364 keV ) y Fe (1291.7 keV ) Co (1332.6 keV ) Cs ( 562.8 keV ) Cs ( 568.9 keV ) Cs 59 65 Zn ( 1115.1 keV ) 46 60 Cs ( 795 keV ) Cs ( 801 keV ) Cs ( 795 keV ) Cs ( 801 keV ) 59 60 134 152 Nb ( 765keV ) Mn (834 keV 0 Nb ( 934 keV ) Nb ( 765keV ) Mn (834 keV 0 134 134 134 Sc ( 889 ke V ) 134 95 134 54 134 95 134 54 Hf (487 keV ) Eu (343.8keV ) 46 92m Cr (320 keV ) keV Cr (320 181 51 152 arbitrar ,

)

keV er channel ( b ) p 934 ( Eu ( 121.7 keV ) Ce ( 145.5 keV ) Nb Fe (192.3 keV ) Eu (344.3keV ) Eu (778 keV ) Sc ( 889 ke V ) Fe (1099 keV ) Sc (1120.3 keV ) Co (1173.1 keV ) Cr (320 keV ) keV Cr (320 Nb ( 765keV ) Mn (834 keV 0 152 141 59 Fe (1291.7 keV ) Co (1332.6 keV ) 46 92m 59 46 60 51 152 95 151 54 59 60 Counts Eu ( 1407.5 keV ) keV ( 1407.5 Eu 152

)

) ( c ) ز 604.2 keV 9 keV ) ( 192.1 keV keV 192.1 Cs ( 562.7 keV ) Cs ( 562.7 .7keV ) Cs ( 568 Cs ( 134 134 134 Hf ( 133.1 keV ) keV 133.1 Hf ( Cs ( 795 keV ) Hf ( 482 keV ) keV ) ( Hf 482 Fe Cr (31 9 Zr ( 724 keV ) Zr ( 756.4 keV ) Nb ( 765keV ) Sc ( 889 ke V ) 46 181 59 51 95 95 95 134 181 Cs ( 1364 keV ) Fe (1099 keV ) Sc (1120.3 keV ) Co (1173.1 keV ) Fe (1291.7 keV ) Co (1332.6 keV ) 59 65 Zn ( 1115.1 keV ) 46 60 59 60 134 Sb ( 1692Sb ( keV ) 124

Gamma-ray energy, keV

Fig. 3.11. Gamma-ray spectra of (a ) 1.2 ml of the 99Mo-molybdate (VI) solute, ( b ) the Fe(III) precipitate after washing and ( c ) 1.2 ml of the supernatant solution measured after a cooling period of three months for 2000 s.

91 3.4.1.1. Total amount of fed iron:

Twelve samples of irradiated 1.0 g MoO3 powder wrapped with 0.6 g Al foil containing 00.0, 10.0, 15.0, 20.0, 30.0, 35.0, 40.0, 45.0, 50.0, 55.0, 60.0 and 65.0 mg FeCl3. 6H2O were dissolved in 34 ml 5 M NaOH and oxidized with addition of 0.5 ml H2O2, thereafter. The dissolution reactions were exothermic and accomplished in about ~ 15 min with the evolution of molecular hydrogen. However the final products were dark-black coloured solutions, initially pale-pink at 00.0 fed dose and red colours of increasing intensity were clearly observed with increasing the amount of fed

FeCl3.6H2O into the reaction mixture solution. During the dropwise addition of H2O2 solution with strong mixing to the product solutions, the temperature decreased from 70 to 60 oC in the course of ≤ 1 min, as shown in Table (3.4).

Table (3.4). Temperature gradient during dissolution of 1.0 g MoO3 wrapped in 0.6 g Al foil targets containing variable Fe amounts with 34 ml 5M NaOH solution at ambient laboratory conditions (~ 25 oC). Elapsed During Before After time, dissolution addition of addition of 20 25 30 35 40 50 60

min* ** H2O2 *** H2O2**** (~ 15 min) (~ 16 min) Temp, oC 80 70 60 57 55 45 40 35 30 ~25 oC Elapsed time from complete dissolution, 1 5 10 15 20 25 35 45 min*****

* Starting from the addition of NaOH to the target material in the dissolver. ** Maximum measured temperature during the dissolution processes.

*** Once the dissolution ends and before dropwise addition of H2O2 i.e, after ~ 15 min.

**** After addition of H2O2 i.e, the re-oxidation of Fe (II) to Fe (III) is an endothermic reaction ***** Digestion time of oxidized Fe (III) iron

The final concentration of NaOH in the reaction mixture solution was found to be ~ 4 M NaOH. The dispersion time, i.e, time elapsed before starting of colloidal species coagulation in the form of colour change and / or

92 formation of very fine particles, and the time of apparent complete precipitation of the formed Fe(III) iron minerals were gradually decreased from ~ 60 to ~ 10 min and from ~ 80 to ~ 30 min with increasing the total concentration of iron in the system from 0.721 to 7.8 x10-3 M Fe, respectively. Separation of the formed Fe (III) minerals and radiometric analysis were conducted as previously described. Fig. 3.12 depicts the relationship between the total concentration of fed iron in the system against the corresponding elimination % of 59Fe radionuclide from the 99Mo-molybdate (VI) solute in ~ 4 M NaOH containing

0.5 ml H2O2 solution. Under the specified conditions of Fe concentration, the elimination % of 59Fe has two distinct successively increasing plateaus. The first elimination stage is very sharp and starts from ~ 67.5 up to 91.7 % 59Fe with increasing the fed dose from 0.721 to 3.85 x 10 -3 M Fe. The second elimination stage is slow and dominates between 91.7 to 97.8 % 59Fe in the iron concentration range from 3.85 to 7.26 x 10 -3 M Fe. The elimination behavior of 59Fe radionuclide (Eγ = 192, 1099 and 1292 keV) can be demonstrated from the gamma-ray spectra of Fig. (3.13) (curves a, b, c and d) corresponding to 99Mo-molybdate (VI) supernatants containing initial total concentrations of 0.721, 3.99, 6.71 and 7.26 x 10-3 M Fe measured after a cooling time of 45 day for 3000 s. The gradual decrease in stability (i.e, dispersion) of the formed Fe(III) minerals is remarkably linked with fast settling of the formed Fe(III) minerals and the elimination % of 59Fe radionuclide with increasing the total amount of fed Fe in the reaction mixture solution. The formation of relatively high dispersed negatively charged fine colloidal particles of Fe (III) minerals and / or soluble Fe(III) and Fe(II) anions in ~ 4 M NaOH solution at higher

FeCl3.6H2O fed doses with consequent penetration of the Millipore filter into the 99Mo-molybdate (VI) supernatants resulted in non-linear elimination % 59Fe with increasing the total concentration of Fe in the system. 93

Fe Elimination % Fe Elimination 59

Total concentration of fed Fe, M

Fig. 3.12. Effect of total concentration of fed Fe on the elimination % of 59Fe radionuclide from the molybdate (VI) solute containing 0.5 ml H2O2 as oxidant.

Sc (1120 ke V)

)

(b) (a) 795keV ( Fe (142 keg) Fe (142 Cs ( 604. keV ) Hf (482 keV) Hf (482 Cs (1368 keV) Cs (1368 keV Cs (1401 Cs ( 562 & 569. keV )

59 Cs Zn (1115 keV)& Fe (1099 keV) Co(1173 keV) Fe (1292 keV) Co(1332 keV) Zr (724&756 keg) Nb(765 keg)

181 134 134 60 59 65 59 60 134 134 95 95 134

Sc (889 keg)

Hf ( 345 keV) Cr ( 320 keV)

46 51 75

Sb (1692 keV) Sb (1692 124

9 )

units (b) Sc (1120 ke V) y 46 Cs ( 604. keV ) Cs ( 562 & 569. keV ) 795keV 134 134 ( Hf (133 kegV) Fe (142 keV) Hf ( 345 keV) Cr ( 320 keV) 59 Cs 51 75 181 Zr (724&756 keg) Nb(765 keg)

units 1401 keV 95 95 134 Hf (482 keV) Hf (482 (

y 181 Cs (1368 keV) Cs (1368 Cs Sc (889 keg)

Zn (1115 keV)& Fe (1099 keV) Co(1173 keV) Fe (1292 keV) Co(1332 keV) arbitrar 46 60 59 65 59 60 134 134 ,

Sb (1692 keV) Sb (1692 124

arbitrar , er channel

)

Sc (1120 ke V) er channel 46 p 9

795keV Counts ( Cs ( 604 keV ) Cs ( 562 & 569. keV ) Cs

Zr (724&756 keg) Nb(765 keg) (c) 134 134 95 95 134 Hf (482 keV) Hf (482

Hf ( 345 keV) Cr ( 320 keV) Hf (133 kegV) Fe (142 keV) 51 75 181 59 181 Sc (889 keg)

Cs (1368 keV) Cs (1368 Cs (1401 keV Zn (1115 keV)& Fe (1099 keV) Co(1173 keV) Fe (1292 keV) Co(1332 keV) 46 Counts

Sb (1692 keV) Sb (1692 60 59 65 59 60 134 134

124

)

(d) Sc (1120 ke V) 9 46

Cs ( 604. keV ) 795keV Cs ( 562 & 569. keV ) ( 134 134 Hf (482 keV) Hf (482 Cs Zr (724&756 keg) Nb(765 keg) 181 95 95 134 Hf (133 kegV) Fe (142 keV)

59 181

Hf ( 345 keV) Cr ( 320 keV) 51 75 Cs (1368 keV) Cs (1368 keV Cs (1401 Sb (1692 keV) Sb (1692 Zn (1115 keV)& Fe (1099 keV) Co(1173 keV) Fe (1292 keV) Co(1332 keV) 60 59 65 59 60 134 134

124

Gamma-ray energy keV Fig. 3.13. Gamma-ray spectra of the supernatants of 99Mo (VI) solute at total Fe concentrations of ( a) 0.721, (b) 3.99, (c) 6.71 and (d) 7.25 x 10 -3 M Fe measured after a cooling period of 45 days for 3000 s.

95 3.4.1.2. Filtration process: Supernatants of 99Mo-molybdate (VI) solutes were radiometrically analyzed by gamma-ray spectroscopy before and after filtration with 20 and

45 µm Millipore filters. Irradiated targets of 1.0 g MoO3 wrapped with 0.6 g

Al foil containing 30 mg FeCl3.6H2O in 8 ml 0.1 M HCl were dissolved in

25.5 ml 6.67 M NaOH solution and oxidized with 0.5 ml of 10 % H2O2 solution, therefore. After ~ 2 hours the formed precipitate of Fe(III) minerals was collected by centrifugation as described above. Ten ml fractions of the supernatant were withdrawn with and without 0.45µm Millipore filter and analyzed by gamma-ray spectrometry. Fig. 3. 14 (curves a, b and c) shows gamma-ray spectra of the initial 99Mo-molybdate (VI) solute and the supernatants, before and after filtration with 45 µm Millipore filter measured after cooling periods of 45 day for 3000 s. It is observed that the elimination of some radionuclides, such as 59Fe, 92mNb, 95Nb, 60Co and 51Cr from the supernatant molybdate (VI) solutes were greatly influenced by the preassembling treatment, i.e centrifugation and filtration of the supernatant after separation of the formed Fe(III) minerals. Filtration with 45 µm Millipore filter greatly hindered the penetration of small sized colloidal particles of 59Fe, 92mNb, 95Nb, 60Co and 51Cr into the supernatants of the 99Mo- molybdate (VI) solutes. Table (3.5) shows the elimination % of 59Fe, 92mNb, 95Nb, 60Co and 51Cr radionuclides from the 99Mo-molybdate (VI) supernatant before and after filtration with 0.45 µm Millipore filter at room temperature (~ 25 oC).

59 92m 95 60 51 99 Table (3.5). Elimination % of Fe, Nb, Nb, Co and Cr radionuclides from Mo-molybdate (VI) supernatant with and without 0.45 µm Millipore filter at room temperature (~ 25 oC).

Radionuclide Elimination % Without filteration With 45 µm Millipore filter Iron-59 78.2 93.3 Niobium-92m 91.3 100 Niobium-95 86.4 95.7 Cobalt-60 81.43 94.2 Chromium-51 66.2 75.5

(a) ) Nb ( 912 keV) Sc (1120keV) Hf (133 keV) 92m 64 Ce ( 145 keV) Ce ( 145 181 801keV 141 Cs ( 569keV) ( Zn ( 511 keV) 65 134 ) Cs 134 Nb (765 keV) Nb (765 )

95 Nb ( 934 keV Sc ( 889 keV) 604keV Eu ( 122 keV) Cs ( 1368keV) Eu ( 1408 keV) 46 92m ( Fe (142 keV) Zn (1115 keV)& K (1460KEv) Fe (1099 keV) Co (1173 keV Fe (1292 keV) Co (1332 keV) 152 59

59 65 60 59 60 134 152 40 795keV Hf ( 482 keV) Cs ( 562keV) Cs ( 181 134 134 Cs Zr( 724 keV) Zr( 756keV) 95 134 95 Nb ( 1847keV) Sb (1692 keV)

124 92m keV

) gy 801keV

( Nb ( 934 keV) ener Cs y 134 Nb (765 keV) Nb (765 )92m )

95 Sc (1120keV)

795keV ) ( (b) Cs ( 569keV) Zn ( 511 keV) 65 Cs 134 Nb ( 912 keV Zr( 724 keV) Zr( 756keV)

Sc ( 889 keV) 95 134 95 46 92m 1460KEv ( Cs ( 1368keV) Zn (1115 keV)& K Fe (1099 keV) Co (1173 keV Fe (1292 keV) Co (1332 keV) Gamma ra

59 65 60 59 60 134 40 Hf (133 keV)

Fe (142 keV) Hf ( 482 keV) Cs ( 562keV) Cs ( 604keV)

181 59 181 134 134 Hf ( 345 keV) Cr ( 320 keV) 51 75 Sb (1692 keV) 124 Counts per channel, arbitrary units

Cs ( 801keV) 134 Nb (765 keV) Nb (765

95 Sc (1120keV) Cs ( 569keV) 64 Zn ( 511 keV) (c) 65 134

Cs ( 795keV) Zr( 724 keV) Zr( 756keV) 95 134 95 Hf ( 345 keV) Cr ( 320 keV) 51 75 Hf (133 keV) Hf ( 482 keV) Cs ( 562keV) Cs ( 604keV) Cs ( 1368keV) Zn (1115 keV)& K (1460KEv) Fe (142 keV) Fe (1099 keV) Co (1173 keV Fe (1292 keV) Co (1332 keV)

181 59 181 134 134 59 65 60 59 60 134 40 Sc ( 889 keV) Sb (1692 keV) 46 124

Gamma-ray energy keV

99 Fig. 3.14.Gamma-ray spectra of the (a) Mo-molybdate(VI) solute before precipitation of The Fe(III) mineral and the supernatants withdrown (b) without and (c) with 0.45 µm Millipore filter measured after a cooling period of 45 days for 3000 s.

97 It is observed that, under the identified experimental conditions, the formed Fe(III) minerals are in the form of highly dispersed colloidal particulates as well as the radionuclides of Nb, Co, and Cr. The differences in the elimination behaviors of 92mNb and 95Nb radionuclides are a matter of 95Zr / 95Nb isobaric radioactive decay / growth equilibrium (as it will be discussed latter on). When 0.20 µm Millipore filter was used to filtrate the supernatants of 99Mo- molybdate (VI) solutes, relatively finer colloidal particulates plugged the pores of the filter. Particles size of, probably formed, freshly precipitated ferrihydrites, amorphous Fe(III) oxyhydroxides and / or hydrous Fe(III) oxides vary between 10 and 100 nm (Kney and Sen Gupta, 2001; DeMorco et al, 2003). Table (3.6) compiles the volumes and behavior of nano-sized particles in solution (Agasyan, 1980).

Table (3.6). Volumes and behavior of nano-sized particles in solutions Particle size, Type Chemical state nm ≤ 1 Soluble anions, cations and / or True solutions molecules From 1 to 100 Colloidal solution or sols Fine dispersed precipitated particles Suspension If the substance is not soluble (clay) in water ≥ 100 Emulsion If the substance is soluble (milk) or (starch and protein molecules) in water. ≥ 100 Precipitates

So, filtration of the molybdate (VI) solutes after precipitation and centrifugation of the precipitated Fe(III) minerals is a very important factor to improve and enhance their purification from fine colloidal particulates of cross-contaminant radionuclides.

3.4.1.3. Concentration of H2O2:

The effect of H2O2 concentration onto the formation of Fe(III) iron minerals and the elimination % of 59Fe radionuclide was investigated using 34 ml 4 M NaOH solutions of the irradiated 1.0 g MoO3 wrapped with 0.6 g Al 98 foil and 30 mg FeCl3.6H2O oxidized with different volumes of 0.25, 0.5 and

1.0 ml H2O2 (10 % w/v). The dispersion time (i.e, before starting of coagulation) and the time of apparent complete settling of the formed Fe(III) minerals were increased with increasing the added volume of oxidant from

0.25 to 1.0 ml H2O2. At volumes of 1.25 and 1.5 ml H2O2 the two times were almost the same as for 1.0 ml H2O2. Table (3.7) compiles the dispersion stability of 30 mg FeCl3.6H2O and color of the formed Fe(III) mineral precipitates with increasing the volume of oxidant in the reaction mixture solution from 0.25 to 1.5 ml H2O2 (10 % w/v).

Table (3.7). Stability of 30 mg FeCl3.6H2O and color changes of the formed Fe (III)

mineral precipitates with the concentrations of H2O2 in the system.

Volume of H2O2 (10 % w/v), ml Time, min Color of the formed Dispersion Coagulation precipitate 0.25 15 30 Dark green- black 0.5 20 60 Faint reddish-brown 1.0 30 85 Deep reddish-brown 1.25 30 85 Bloody-red* 1.5 30 85 Bloody-red* * Inactive targets The corresponding elimination behavior of 59Fe radionuclide can be predicted from the gamma-ray spectra in Fig. 3.15 (curves a, b and c) for the supernatants of 99Mo-molybdate (VI) solutes containing 0.25, 0.5 and 1.0 ml

H2O2 measured after a cooling period of 45 day for 3000 s. Fig. 3.16 shows 59 the effect of H2O2 concentration on the elimination % of Fe radionuclide from the 99Mo-molybdate (VI) solutes. The elimination % of 59Fe radionuclide decreased with increasing the volume of added H2O2 solution from 0.25 to 1.0 ml. This may be due to complete oxidation of Fe (II) iron to Fe (III) iron in solution and transformation into more stable (i.e, highly dispersed) Fe (III) iron colloid such as the red hematite mineral predicted from the corresponding time of dispersion / coagulation and color changes, besides to Raman investigation of the formed Fe (III) minerals.

Nb (765 keV) Nb (765 Cs (569 keV) Cs (569 Fe (142 keV)

95 59

134 Sc (1115 &1120 keV)) Sc (1115 &1120 46 Zn & Fe ( 1099 keV) Co (1332 keV) 65 Nb (934 keV) 59 60 Cs (795keV) Zr (724 keV) Zr (756 keV) Hf (133 keV)

95 95 134 92m (a) Cs (562 keV)

Cs (604 keV) Co (1332 keV) keV) (1332 Co keV) (1368 Co Co (1401keV) Fe ( 1292 keV) 181 134 59 60 60 60 ) 134

Sb (1692 keV) Sb (1692 124

units y

keV) Cs (569 Fe (142 keV) 134 59 Nb (765 keV) Nb (765 95

arbitrar , Sc (1115 &1120 keV) Sc (1115 &1120 Cs (562 keV) Cs (604 keV) Hf (133 keV) 46

134 (b) ) 134 Nb (934 keV)

181 Cs (795keV)

Zr (724 keV) Zr (756 keV) 95 95 134 92m Co (1332 keV) keV) (1332 Co keV) (1368 Co (1401keV) Co Zn & Fe ( 1099 keV) Fe ( 1292 keV)

65 59 60Co (1332 keV) 59 60 60 60

Sb (1692 keV) Sb (1692 124 er channel p Counts Fe (142 keV)

Cs (569 keV) Cs (569 134

Nb (765 keV) Nb (765 95

Hf (133 keV) (c) Sc (1115 &1120 keV) Sc (1115 &1120 181 46 Cs (562 keV) Cs (604 keV) Co (1332 keV) keV) (1332 Co keV) (1368 Co Co (1401keV) Fe ( 1292 keV) 134 ) 134 Nb (934 keV) Zn & Fe ( 1099 keV) Cs (795keV)

59 60 60 60

Zr (724 keV) Zr (756 keV) 65 59 60Co (1332 keV) 95 95 134 92m

Sb (1692 keV) Sb (1692 124

Gamma-ray energy keV

99 Fig. 3.15.Gamma-ray spectra of the supernatants of Mo-molybdate (VI) solutes containing (a) 0.25, (b) 0.5 and (c) 1.0 ml of H2O2 solution measured after a cooling time of 45 days for 3000 s.

100

Fe Elimination % Fe Elimination 59

Volume of H2O2, ml

59 Fig. 3.16. Effect of H2O2 concentration on the elimination % of Fe radionuclide from the 99Mo-molybdate (VI) solutes.

101 3.4.1.4. Concentration of NaOH:

Four radioactive targets each of 1.0 g MoO3 wrapped with 0.6 g Al foil containing a fed dose of 30 mg FeCl3.6H2O were dissolved in concentrated NaOH solution. Thereafter, the mixture solutions were adjusted to final volume of 34 ml containing 0.5 ml H2O2 with addition of nitric acid to obtain solutions of ~ 4.0, 2.0, 1.0 and 0.5 M NaOH, as described previously. Fig. 3.17 (curves a, b, c and d) manifests the elimination behavior of 59Fe radionuclide from the corresponding gamma-ray spectra of the supernatants of 99Mo-molybdate(VI) solutes containing ~ 4.0, 2.0, 1.0 and 0.5 M NaOH solutions measured after a cooling period of 45 day for 3000, s. Fig. 3.18 shows the effect of NaOH concentration on the elimination % of 59Fe radionuclide from the 99Mo-molybdate (VI) solutes. Dispersion stability of the formed Fe(III) colloids due to the formation of negatively charged Fe(III) species in solution decreased with decreasing the alkali concentration from ~ 4.0 to 0.5 M NaOH with consequent increase in the elimination % of 59Fe radionuclide. The coagulation time ~ 120, 60, 20 and 20 min were decreased with decreasing the alkali concentration to ~ 4.0, 2.0, 1.0 and 0.5 M NaOH in solution, respectively. Firstly, the elimination % of 59Fe radionuclide from the 99Mo-molybdate (VI) solutes was sharply increased from ≤ 93.38 to ≥ 97.25 % 59Fe with decreasing the NaOH concentration from ~ 4.0 to 2.0 M and passing, thereafter, through a steady state of 97.25 to 97.4 elimination % 59Fe at the intermediate concentrations from ~ 2.0 to 1.0 M NaOH. Secondly, the elimination % of 59Fe radionuclide from the molybdate (VI) solutes increased to 97.91 at 0.5 M NaOH. Addition of concentrated nitric acid acted as a titrating coagulant leading to H+ / OH- neutralization with consequent consumption of OH- anions forming the negative charges of dispersed Fe(III) - colloid. Increasing the concentration of less complexing NO3 anions with further additions of concentrated nitric acid leads to form less stabilized 59Fe- Fe (III) iron minerals, such as ferrihydrite transformation into goethite, with a

102

Cs (569 keV) Cs (569 Fe (142 keV) 134 59 Nb (765 keV) Nb (765

Sc (1120 keV) Sc (1120 ) 95

46 , ? eV k

Cs (562 keV) (a) Hf (133 keV) Cs (604 keV) 1401 ( 134 Cs (795keV) Hf(482 keV) 181 ) 134 Hf(345keV) Zr (724 keV) Zr (756 keV)

Cr(320 keV)

95 95 134 46S c(889 keV) 181 Co (1332 keV) keV) (1332 Co keV) (1368 Co Co 51 175 Zn (111keV)

Fe (1099 keV) Co(1173 keV) Fe ( 1292 keV)

60 59 65 59 60 60 60

Sb (1692 keV) Sb (1692

124

Fe (142 keV) 59 Cs (569 keV) Cs (569 134 Nb (765 keV) Nb (765 Sc (1120 keV) Sc (1120

46 95 , ? Hf (133 keV) units 181 y Cs (562 keV) Hf(482 keV) Cs (604 keV) 134

181 ) 134 (b)

Hf(345keV) Cs (795keV) Zr (724 keV) Zr (756 keV) Co (1332 keV) keV) (1332 Co keV) (1368 Co Co (1401keV) 175 95 95 134 46S c(889 keV) Zn (111keV) Fe (1099 keV) Co(1173 keV) Fe ( 1292 keV)

60 59 65 59 60 60 60

Sb (1692 keV) Sb (1692

124

arbitrar

Fe (142 keV) Cs (569 keV) Cs (569 59 er channel Nb (765 keV) Nb (765 134 95 p Sc (1120 keV) Sc (1120

46 , ?

Hf (133 keV) (c) Cs (604 keV) Cs (562 keV) 181 Cs (795keV) Zr (724 keV) Zr (756 keV) 34 Hf(482 keV) ) 134 95 95 134 46S c(889 keV)

Hf(345keV) Counts 181 Co (1332 keV) keV) (1332 Co keV) (1368 Co (1401keV) Co Zn (111keV) Fe ( 1292 keV) Fe (1099 keV) Co(1173 keV)

175 59 60 60 60 60 59 65

Sb (1692 keV) Sb (1692

124

Nb (765 keV) Nb (765 Sc (1120 keV) Sc (1120 95

46 , ? (d) Cs (795keV) Zr (724 keV) Zr (756 keV) 95 95 134 46S c(889 keV)

Co (1332 keV) keV) (1332 Co keV) (1368 Co (1401keV) Co Zn (111keV) Fe (1099 keV) Co(1173 keV) Fe ( 1292 keV) Sb (1692 keV) Sb (1692 60 59 65 59 60 60 60

124

Gamma-ray energy keV

Fig. 3.17. Gamma-ray spectra of the supernatants of 99Mo-molybdate (VI) solutes in about (a) 4, (b) 2, (c) 1 and (d) 0.5 M NaOH solution measured after 45 days from the end of irradiation for 3000 s.

103

Fe Elimination % Fe Elimination 59

Concentration of NaOH, M

Fig. 3.18. Effect of NaOH concentration on the elimination % of 59F radionuclide from the molybdate (VI) solute.

104 - steady state up to ~ 1 M NaOH. At 0.5 M NaOH, concentration ≥ 3.5 M NO3 anions in the mixture solution must direct the transformation reactions of Fe (III) iron towards predominance of the goethite α- FeOOH form (He-Hun et al., 2003).

3.4.2. Elimination assessment of 59Fe radionuclide: 3.4.2.1. Contribution of 59Fe in the formed Fe(III) minerals and 99Mo-molybdate solutes:

During dissolution of the irradiated MoO3 target wrapped with 0.6 g Al foil containing 1.37 mg Fe together with the added FeCl3.6H2O in concentrated 5 M NaOH solution, 59Fe radionuclide is homogeneously distributed into 59 59 soluble Fe-Fe(OH)2 and Fe(II) iron tagged with Fe products. This is called isotopic dilution (I. D) where the specific 59Fe radioactivity is diluted by the stable isotopes of the element (Wolf et al., 1986). Addition of H2O2 to the dissolution reaction mixture solution, at ambient atmospheric conditions, accelerates oxidation of the soluble Fe (II) species into insoluble Fe(III) minerals. The rate of transformations into product Fe (III) iron mineral depend on chemical composition of the reaction mixture solution such as total dose of

Fe (II), the cations and anions present in solution, H2O2 and alkali concentrations, rate of oxidation and pretreatment of the Fe (II) and Fe (III) solutions i.e, time of aging and temperature (Missawa et al., 1974; Chukhrov et al., 1977; Carlson and Schwertmann, 1980; Posely-Dowty et al., 1986). In-situ formed Fe (III) minerals are characterized with different stabilities in the form of solubility and / or dispersion with consequent homogeneous distribution of 59Fe radionuclide between the formed solid minerals and the aqueous phase (define their contribution in the two phases). Fe (III) minerals are in states of dynamic transformations and the isotopic composition of Fe in solution and in the formed Fe(III) precipitates is similar with no fractionation. The distribution of 59Fe radiotracer between its isotopic-carriers in the solid and aqueous solution is controlled by the amount of Fe in the two phases

105 according to the isotopic dilution concept. Simply, the specific activities of 59Fe radionuclide in the formed Fe(III) precipitate and in the respective solution are equal and calculated from the formula:

A l A s S = ------= ------X (Y – X)

Where; S is the specific activity, Al and As are the measured activities in the liquid and onto the solid phases, respectively, Y is the wt of the total fed iron (mg), X is the wt of dissolved Fe in the liquid phase (mg) and (Y-X) is the wt of Fe onto the formed Fe (III) mineral precipitate (mg). Table (3.8) lists the calculated amounts of Fe contributions in the liquid and solid phases at the specified experimental conditions and the corresponding elimination percentage % of 59Fe radionuclide. The elimination percentage is the distribution ratio of 59Fe radioactivity in the precipitated Fe(III) minerals to its initial value in the aqueous phase at the given experimental conditions. Investigations conducted out at fixed concentrations of alkali and oxidant i.e, 34 ml 4 M NaOH containing 0.5 ml (10 % w/v) H2O2 solution and varying fed doses of iron in the range from 1.37 to 14.81 mg Fe by the addition of

FeCl3. 6H2O to the irradiated (MoO3 and Al) targets as compiled in Table (3.8) are illustrated by Fig. 3.19. It is observed that the contribution profile of Fe in the aqueous phase (in the form of soluble / dispersed Fe) as a function of the total amount of Fe in the system has three distinct stages giving plausible explanations for the nonlinear behavior of elimination % 59Fe vs. total Fe dose relationship in Fig. 3.12. It is a preliminary evidence for the presence of, at least three predominating groups of Fe(III) iron minerals. Where peptization greatly differs from ordinary dissolution, in the same medium at a given temperature, increasing the initial amount of Fe (II) from 1.37 to 7.58 mg Fe (i.e, from 0.721 up to 3.99 x 10-3 M Fe) followed by controlled oxidation with

0.5 ml H2O2 resulted in highly dispersed Fe(III) colloids. The corresponding

106 59 Table (3.8). Amounts of Fe-iron contribution (mg) in the formed Fe(III) mineral precipitates and 34 ml aqueous phase and the corresponding elimination % of 59Fe radionuclide as a function of the

initial total concentrations of Fe, NaOH and H2O2 in the system.

Experimental conditions Contribution of Fe in the two phases, Elimination % of mg 59Fe radionuclide NaOH, M H2O2, ml Total amount Solid phase Liqued phase of Fe, mg Effect of total amount of Fe, mg 4.0 0.5 1.37 0.925 0.445 67.5 4.0 0.5 3.4385 2.9685 0.47 86.34 4.0 0.5 4.4727 4.0027 0.47 89.5 4.0 0.5 5.5070 5.031 0.476 91.35 4.0 0.5 7.5755 7.0755 0.50 93.386 4.0 0.5 8.6098 8.2838 0.326 96.22 4.0 0.5 9.6440 9.314 0.33 96.57 4.0 0.5 10.6783 10.401 0.277 97.40 4.0 0.5 11.7125 11.426 0.287 97.54 4.0 0.5 12.7468 12.448 0.299 97.69 4.0 0.5 13.7811 13.481 0.300 97.82 4.0 0.5 14.8155 14.498 0.317 97.82 Effect of H2O2 volume, ml 4.0 0.25 7.5755 7.2285 0.34669 95.42 4.0 0.5 7.5755 7.0755 0.50 93.386 4.0 1.0 7.5755 6.9954 0.580 92.34 Effect of NaOH, M 4.0 0.5 7.5755 7.0755 0.50 93.386 2.0 0.5 7.5755 7.36769 0.2078 97.257 1.0 0.5 7.5755 7.3787 0.196766 97.4 0.5 0.5 7.5755 7.4173 0.1582 97.91 Effect of total volume, ml 4.0* 0.5 1.37 0.925 0.445 67.5 4.0** 0.5 1.37 0.931 0.439 67.95

* At a total volume of 34 ml reaction mixture solution. ** At a total volume of 30.5 ml reaction mixture solution.

contribution in the aqueous solution slightly increased from ~ 0.445 to 0.5 mg Fe at the given concentrations of Fe, respectively. In true dissolution the content of a solute no longer depends on the amount of the substance taken for dissolution after saturation is attained. The difference is due to the fact that a peptizer (i.e, NaOH) is needed for colloidal dissolution / dispersion whereas a third component is not needed for true dissolution. An increase in the dispersity, i.e, small particles sizes, of the solid phase increases its solubility in the surrounding aqueous medium or the ability to liberate from a given solid phase into the form of a colloidal state. The dependence of the corresponding solid phases composition and nature on the relative

concentrations of Fe (II) / H2O2 and the consequent decreases in solubility / disperesity is manifested by the second stage at the higher 8.6 and 9.65 mg Fe

107 g m , Amoun t of Fe in solution

Total amount of Fe in the system, mg

Fig. 3.19. Contribution , mg of iron in 34 ml 4 M NaOH solution after 2 hours from addition of 0.5 ml H2O2 solution to variable Fe (II) iron concentrations (in mg) in the system at ambient atmospheric conditions.

108 doses in solutions at high alkali concentration. At every degree of super- saturation, when it is statically more probable for comparatively large nuclei to originate, the nuclei of a new dispersed phase may apparently be formed. Thereafter, solution saturated relative to large crystals is unsaturated relative to small ones of the same group substances with consequence low and high solubility and / or dispersion, respectively. After complete dissolution and oxidation of the 99Mo-molybdate solutes,

H2O2 concentration was completely sufficient to re-oxidize the reduced Fe(II) species to Fe(III) oxides up to the inflection point at the total value of ~ 7.58 mg Fe and to Fe (III) oxyhydroxides at intermediate total doses of 8.6 and 9.6 mg Fe, respectively. Table (3.9) shows the specific surface area and particle size of Fe(III) minerals (Kalinskaya et al., 1979; Kieser et al., 1983; Hanne, 2005; Ligodi , 2008; Kahani and Jafari, 2009).

Table (3.9): Specific surface area and particle size of Fe(III) minerals. Fe( III) mineral Specific surface area, m2 Particle size, (nm) Ferrihydrite ≥ 214 ≤ 5 Lepidocrocite 195 5 – 20 Goethite 113 20 Magnetite 90 Variable < 100 > 40 Maghemite 87 Variable < 100 > 40 Hematite 19 40

The reactivity (the measure of reductive rate) decrease from ferrihydrite to hematite in the order of (Postima 1993; Larsen and Postima 2001):

Ferrihydrite > lepidocrocite > goethite > magnetite > maghemite > hematite

The contribution of Fe(II) species in the system may be gradually increased at further higher Fe fed doses. This suggestion was verified by Raman spectrometery (section 3.4.2.2) which indicates the presence of lepidocrocite at 9.6 mg Fe as one of the transformation products of Fe ( III)

109 colloids, which does not form in absence of residual Fe(II) species in the reaction medium. Taking into consideration the predominance of lepidocrocite at the higher total Fe concentration and that it is 104 – 105 more soluble than goethite, the less soluble goethite mineral is formed at the lower concentration of 8.6 mg Fe. The low solubility of goethite than lepidocrocite compensates the corresponding increase in amount of the formed Fe (III) minerals with consequence ~ two equal elimination % of 59Fe from the 99Mo-molybdate (VI) solutes at the total two concentrations of 8.6 and 9.64 mg Fe (viz. Figs. 3.12 and 3.19 and Table (3.8)). Thereafter, mixtures of Fe(III) and Fe(II) of varying molar ratios may be obtained at further higher total doses of Fe contributed in the third stage. The adsorption of Fe (II) iron by goethite may lead to the formation of destabilized magnetite, Fe3O4, as the third predominating new solid phase. At room temperature, the mechanism of formation of a new Fe(III) mineral from mixtures of Fe(III) and Fe(II) hydroxides in solution can be described by the following equations (Misawa et al., 1969 and 1971):

2 Fe(OH)2 + 1/2 O2 2 α- FeOOH + H2O

Fe(OH)2 + 2 α- FeOOH Fe3O4 + 2H2O

The observed steady slightly increased solubility / dispersion tailing in Fig. 3.19 may be of soluble Fe (II) iron not incorporated (adsorbed) into the Fe(III) iron intermediate transformed to magnetite with elimination values persisting around 97.4 to 97.82 % 59Fe with increasing the total amount of fed Fe from 10.68 to 14.8 mg in the system (Table 3.8 and Fig. 3.12). The investigations were also conducted out at a fixed alkali concentration of 34 ml 4M NaOH containing 7.58 mg Fe and variable concentrations of H2O2 as an oxidant. The obtained data are listed in Table (3.9) and demonstrated in Fig. 3.20. It is of interest to consider the data given in Table (3.7, too). Due to partial oxidation of Fe (II) hydroxides to 110

Amount of Fe in solution, mg

Volume of H2O2, ml

Fig. 3. 20. Effect of H2O2 concentration on the contribution of Fe in the aqueous phase.

111 Fe(III) hydroxides, at the low concentration of 0.25 ml H2O2, the above reactions between Fe(II) hydroxide and goethite may be considered. On the other hand, at the higher concentration of ≥ 1.0 ml H2O2 in the system, oxidation of the Fe3O4 phase into the metastable maghemite phase γ-Fe2O3 may be considered according to the equation (Jang, 2003):

2 Fe3O4 + 1/2 O2 3 γ-Fe2O3

Which transforms by ageing and / or further oxidation to bloody red coloured hematite α-Fe2O3. It was verified by the addition of greater volumes of 1.25 and 1.5 ml H2O2 to ~ 7.58 mg Fe in solution where red- bloody coloured precipitates were coagulated after longer time intervals - (Table 3.7). Formation of the red-purple Ferrate (IV) ion, FeO4 , obtained by oxidizing suspensions of Fe2O3.nH2O in concentrated alkali with chlorine from the added FeCl3.6H2O was excluded, because of the unfavorable reaction conditions in addition to the very high solubility and strong oxidizing properties of the ferrates (VI). It is noted that adsorption of Fe(II) onto the preformed (i.e, readily formed) Fe(III) minerals tend to form relatively destabilized (i.e, low dispersed particle aggregates) with consequent higher elimination % of 59Fe from the 99Mo-molybdate (VI) solute. In other words, an increase in the dispersity of the solid phase increases its solubility in the surrounding medium or the ability to liberate from the solid phase to the aqueous solution. It must be recognized that elimination of 59Fe radionuclide from the 99Mo-molybdate (VI) solute is also affected by the total dose of fed Fe in the system, however it does not have the linear relationship of the mass dilution law due to the different solubility contributions of the same and different kinds of formed Fe(III) minerals. The particle shape of amorphous iron oxyhydroxides and oxides depends on the initial Fe(II) : Fe(III) molar-

112 ratios and the precipitation procedure. The γ-Fe2O3 phase, when present in the precipitate in amounts of 70 wt % or more, favors the formation of nano dispersed needle particles. At lower γ-Fe2O3 content the particles are plate like (Belous et al., 2000). The third investigated parameter included the concentration of NaOH /

NaNO3 in the reaction mixture solution while keeping the other parameters fixed. Fig. 3.21 demonstrates the effect of NaOH concentration on the contribution of the formed ferric minerals in 34 ml NaOH / HNO3 solutions containing a total dose of ~ 7.58 mg Fe and 0.5 ml H2O2. It is observed that stability of the dispersed ferric colloid decreased with decreasing the alkali - + concentration (via neutralization of OH with H of concentrated HNO3 acid), from ~ 4 to 0.5 M NaOH. Table (3.8) shows that the lower the contribution of ferric minerals in the liquid phase the higher is the elimination % of 59Fe radionuclide from the 99Mo-molybdate (VI) solutes. If the same amount of a precipitated Fe(III) mineral was taken for distribution by increasing the amount of peptizer (i.e NaOH), peptization will rapidly develop until the precipitate will be completely peptized. Such dependence can also be explained by the fact that a definite amount of a peptizer is needed for the colloidal dissolution of a precipitate. However, a precipitate can not always be completely / or partially peptized. Peptization is hindered by re-crystallization and ageing, which causes the particles to stick together. Moreover, it is difficult to peptize a precipitate obtained by coagulating a sol with polyvalent ions which are firmly bound to the surface of the particles that have adsorbed them. In peptization, as in coagulation, stoichiometric ratios are not observed between the amount of peptizing ions and that of a peptized precipitate as shown in Fig 3.21.

113

Amount of Fe in solution, mg

Concentration of NaOH, M

Fig.3. 21: Effect of NaOH concentration on the contribution of Fe in the aqueous phase

114 To peptize a precipitate and obtain a lysol, it is not necessary for the surface of particles to be covered with a layer of adsorbed peptizing ions. However, the dispersion of particles in the sol depends on the amount of peptizing ions. When the content of peptizing ions is low, particles of higher orders that consist of several primary particles are formed, and when it is large, primary particles are formed. Table (3.8) compiles the amounts of iron contribution (mg) between the formed Fe(III) minerals and 34 ml aqueous phases as a function of total dose of Fe, concentration of NaOH 59 and H2O2 in the system and the corresponding elimination % of Fe radionuclide. Increasing the total volume of the reaction mixture solution from 30.5 to 34 ml 4 M NaOH solution at a total amount of 1.37 mg Fe, the concentration of dissolved Fe (III) minerals in the aqueous phases increase from 0.439 to 0.445 mg Fe with consequent decrease of the elimination % of 59Fe radionuclide from the 99Mo-molybdate (VI) solutes.

3.4.2.2. Raman spectroscopy of Fe (III) minerals: The transformations of ferrous (II) iron under controlled oxidation with

0.25, 0.5 and 1.0 ml H2O2 solution, variable concentrations of total iron (3.44, 7.58, 8.61, 9.64, 11.71 and 14.82 mg Fe) in the reaction mixture solutions of ~

4M NaOH, and / or neutralized with the addition of concentrated HNO3 acid - to 0.5 M NaOH in presence and absence of the MoO4 anions were investigated by Raman spectroscopic analysis. The Fe (III) iron samples were prepared and separated from the corresponding reaction mixture solutions, as previously mentioned. Thereafter, they were air dried for ~ 3 days in an electric furnace at 50 oC. Raman spectra were excited by Ex- Laser of 1064 nm at a resolution of 16 cm-1 in the frequency range from 50 to 4000 cm-1. The results were identified according to (Thibeauet al., 1978; Kalinskaya et al., 1979; Kieser et al., 1983; Nauer et al., 1985; Dűnnwald and Otto 1989; Boucherit et al., 1991; De Faria et al., 1997; Ouyang et al., 1997; Kozlova

115 et al., 1998; Oh et al., 1999; Bonin et al., 2000; Wang et al., 2002; Shebanovea and Lazer 2003; Witke et al., 2004; Monika, 2009).

3.4 .2.2.1. Effect of total Fe dose: Table (3.10) shows Raman spectra of six selected samples each contains 0.6 g Al and different amounts of 10.0, 30.0, 35.0, 40.0, 50.0 and 65.0 mg

FeCl3.6H2O i.e, corresponding to total a mount of 3.44, 7.58, 8.61, 9.64, 11.71 and 14.82 mg Fe dissolved in 34 ml 4 M NaOH solution and then, oxidized with 0.5 ml (10 % w/v) H2O2. After separation and drying, as previously described, the resulting Fe (III) iron minerals were identified by Raman spectroscopy, to identify the transformation product of Fe (III) iron as a function of total iron concentration at fixed oxidant concentration in absence of MoO3. In the sample precipitated from 3.44 mg Fe the frequencies of Raman spectra indicated highly hydrated Fe (III) oxide, (e.g, hematite α-Fe2O3 and ferrihydrite), siderite FeCO3 and H2O in high intensity forming highly dispersed Fe(III) minerals at low Fe and relatively high H2O2 concentrations. Insoluble siderite was randomly composed from atmospheric CO2 and / or Na2CO3 from solution before oxidation of Fe (II).

It is highly stable and persists oxidation to Fe2(CO3)3 (Monika 2009). At the amount of 7.58 mg Fe (i.e, partial decrease of H2O2 / Fe(II) ratio), the ferrihydrites disappeared on the expense of maghemite γ-Fe2O3 and goethite α-FeOOH. The oxide of maghemite may be introduced via conversion, mainly, of ferrihydrite and / or to a less extent of hematite by adsorption of Fe (II) from solution. Formation of the oxyhydroxide α- FeOOH started, however, of ill identified bands. Fe(III) minerals precipitated from solution containing 8.61 and 9.64 mg Fe (II) oxidized with 0.5 ml

H2O2 indicated complete disappearance of the Fe (III) oxide minerals (i.e. hematite and maghemite) on the expense of the oxyhydroxides goethite and the residual ferrous hydroxide in strong alkali medium.

116 (III) iron transformations from 34 ml 4 M NaOH solutions containing variable total iron

doses oxidized with a constant volume of 0.5 ml H2O2(10 % w/v) with (W) and without

(W. O) 1.0 g MoO3. 3.44 7.58 8.61 9.64 11.71 14.82 mg Fe Fe, mg Freq. W. O W W. O W W. O W W. O W W. O W W. O W cm- 1 Hematite 236 (0.8) 236 (4) (225-245)- 235 239(0.6) 239(1.9) 290-300 286 (5.7) 287 (8.7) 412 286(5) 287 (4.4) 498,500 412 (18) 413(0.8) 613 413(16) 486(6) 475(4) 490 (2.6) 475(2.7) 617(5.2) 617(5.1) 621(4) Maghemite 351(5.6) 344—350 374(2)) 351(5.6) 380 529(6.9), 513(6) 512 660(2.6) 648(4.7) 665 729(4.9) 725(7.6) 730 Lepidocrocite 250 251(5.3) 251(1.4) 247(19 247(3.8) 255(3.3) 251(43) 259(5.3) 340,348 328(5) 251(65) 351(2.3) 656(1.8) 351(5.6) 344(41) 374(6.6) 374(5.4) 340(5.4) 382(1.1) 660(2) 379 386(8.8) 351(5.6) 652(4.4) 528 533(7.2) 382(3.6 641(2.7) 513(6) 1323(1.2), 650 656(6.3) 517(2.7) 656(10) 534(3) 1327(9.9) 656(1.1) 1307 652(2.9) 1323(1.7) 648(4.7) 1308(3.8) 1331(5.7) 1315(4.2) Goethite 232(1.7) 247(1.5) 236(5.2) 244 236(4) 251(1.4) 247(27) 232(1.9) 247(3.8) 239(1.6 255(3.3) 251(43) 259(5.3) 299 251(5.3) 251(65) 297(4.1) 247(19) 297(24) 378(3) 401(3.5) 270(5.2) 374(6.6) 486(2.8) 287(8.7) 340(5.4) 274(2.8) 382(1.1) 687(3.3) 475(2.3) 385, 400 301(28) 401(32) 490(4.9) 529(1.6) 480 374(2), 382(3.6) 367(5.9) 386(8.8) 471(2) 687(5.6) 534(3) 475(21) 552(4) 540, 550 486(6) 517(2.7) 525(4.6) 471(3.6) 490(11) 1011(2.1) 999(6.9) 479(2.2) 698(4.9) 668(2.8) 681 490(2.6) 556(2.5) 552(12) 548(1.1) 552(6.) 995(5) 533(5.3) 1007(5.7) 363(5, 8) 1003 683(2) 679(2.3) 494(17) 984(1.1) 691(10) 552(14) 1003 (7) 1003((1.4) 995(5.3), 679(5) 1019(1.2) 995(6.6) 660(2) 992(43) 1003(5.9) Magnetite 534(3) 298, 310, 319 320(5.3) 301(2.9) 533(5.3) 313(2.7) 324(2.3) 532,540 324(16) 552(6.) 313(0.6) 552(14) 328(5.5) 324(3.7) 548(1.1) 691(10) 660(2) 552 529(2.6) 544(1.2) 529(1.6) 668-670 687(3.3), 552(4.) 687(5.6) 652(4.4) 668(2.8) 656(1.1)

Fe(OH)2 556(2.5) 552(12) 548(1.1) 552(6.) 534 (3) 544(1.2) 552(4.) 544 533(7.2) 529(2.6) 533(5.3) 529(1.6) 552 552(0.4) 552(14) Ferrihydrite 363(6.7) 363(5.8) 370 363 (5) 374(5. 529(1.6) 510 513(2.2) 502(2) 702(4.1) 710 729(12) 710(2.7) 702(4.4) Siderite 193(2.2) 710(2.7) 182(1.1) 185 (4) 193(3.2) 185(0.9) 185(4.6) 184 286(5.7) 1096(4.4) 287(8.7) 185 (10) 197(37) 733(5) 1080(1.7) 287 286(4.9) 729(4.9) 725(7.6) 710(1.7) 1073(3.6) 729(12) 1084(2.6) 1088 (3) 1069(0.5) 731 1069(5.5) 1090 1088 (9) Wurecite 594 (6) 594(13) 595 H2O 1616(10) 1632 (6) 1616(2.7) 1628(2.6) 1624(4) 1632 (2.5) 1620(1.5) 1620(1.6) 1609(3.8) 1616(1) 1620 (1) 1620 1616((9) 1632(1.4) 1605(3.1) MoO4 996 977 234(1.9 232(1.7) 232(1.9) 236(5.2) 863(4.3) 212(7.9) 897 320(3.1) 806(2.4) 324(16) 313(0.6) 837(7.3) 224(5.7) 882 494(5.6) 822(56) 706(13) 810(5.7) 895(11) 848(3.3) 820 806(1.7) 857(1.7) 799(2.5) 818(3.9) 961(2.1) 857(3.5) 692 810(16.6 887(53) 656(10 968(2.2) 976(12) 941(2.2) 664 899(28)) 992(43) 833(11) 988(2.7) 999(5) 289 995(16) 995(5.3) 984(1.1) 225 317 339 492

117 Table 3.11. Ferric (III) iron transformations from 34 ml 4 and 0.5 Table (3.12). Ferric (III) iron transformations from 34 ml 4 M NaOH M NaOH solution adjusted with HNO3 acid containing constant solutions containing total iron doses of 7.58 mg Fe and variable volumes concentrations of 7.58 mg Fe and 0.5 ml H2O2 (10 % w/v) with (W) of 0.25, 0.5 and 1.0 ml H2O2 solution (10 % w/ v) with (W) and without and without (W. O) 1.0 g MoO3. (W. O) 1.0 g MoO3.

H2O2, ml 0.25 0.5 1.0

NaOH, M 4 M NaOH 0.5 M NaOH Freq. W. O W W. O W - 1 W. O W cm W. O W Freq. cm- 1 W. O W Hematite 236 (4) 228(5.2) (225-245)- 235 239(1.9) 232(4.8) Hematite 236 (4) 228(6.4) 290-300 287 (8.7) 413(1.8) (225-245)- 235 239(1.9) 297 (2.7) 412 287 (4.4) 413(2.2) 290-300 287 (8.7) 413 (2.6) 498 413(0.8) 606(6.2) 412 287 (4.4) 483 (5.3) 613 486(6) 606(6.8) 498 413(0.8) 490 (2.6) 613 486(6) 617(5.2)

490 (2.6) Maghemite 355(9.1) 617(5.2) 344—350 374(2)) 355(11) Maghemite 374(2)) 355(4) 380 529(6.9), 509(7.3) 344—350 529(6.9), 525 (1.6) 512 660(2.6) 506(8) 380 660(2.6) 714 (4) 665 729(4.9) 664(5.8) 512 729(4.9) 730 725(11) 665 725(12) 730 Lepidocrocite 259(2.2) 371(4.3) Lepidocrocite 251(1.4) 250 359(31) 374(2.5) 250 251(65) 340,348 371(4.5) 475(3) 340,348 340(5.4) 379 637(5.2) 479(4) 379 517(2.7) 528 664(17), 521(3.3) 528 650 1327(3.9) 683(3) 650 1307 1308(3.7) 1307 Goethite 236(4) 251(1.4) 278(4.8) Goethite 236(4) 232(1.7) 263 (2) 297 (2.7) 244 251(5.3) 251(65) 270(9.5) 244 251(5.3) 251(1.4) 362 (2.9) 355(4) 299 287(8.7) 232(1.7) 378(5.2) 299 287(8.7) 251(65) 478 (5.5) 483 (5.3) 385, 400 374(2), 340(5.4) 479(1.8) 385, 400 374(2) 340(5.4) 555(3.6) 480 486(6) 382(3.6) 486(1.8) 480 486(6) 382(3.6) 686 (1.7) 540, 550 490(2.6) 517(2.7) 548(4.5) 540, 550 490(2.6) 517(2.7) 992 (6) 681 683(2) 556(2.5) 548(4) 681 683(2) 556(2.5) 1003 1003((1.4) 679(2.3) 664(3.6) 1003 1003((1.4) 679(2.3) 995(5.3) 675(4.3) 992(43) 992(43) 995(5.6) 995(5.3) 1015(4.2) Magnetite Magnetite 298, 310, 319 313(4.9) 328(2.6) 298, 310, 319 532,540 313(48) 521(3.3) 556(2.5) 532,540 552 544(2.7) 683(3) 679(2.3) 552 668-670 664(17)

668-670 Fe(OH)2 556(2.5) 548(4.5) Fe(OH)2 556(2.5) 555(3.6) 544 544(2.7) 521(3.3) 548(4) 544 552 552 Feroxyhyte 413(17) Ferrihydrite 362 (2.9) 525 (1.6) 400 664(17) 370 710 (2) 714 (4) 663 1327(3.9) 510 1322 1327(3) 710 Ferrihydrite 355(9.1) Siderite 182(1.1) 182 (5.5) 370 371(4.5 371(4.3) 355(11) 184 287(8.7) 1095(4.8) 510 702(18) 374(2.5) 506(8) 287 729(4.9) 710 710(4.9) 513(1.3) 509(7.3 731 1084(2.6) 729(4.3) 725(1) 1090 725(12) Wurcite 598 (4.7) Siderite 182(1.1) 595 184 274(47) 282(2.4 287(8.7) H2O 1616(2.7) 1627 (2.1) 1631(5.3) 287 1096(2.3) 729(4.3) 729(4.9) 1620 731 1096(3.5) 1084(2.6) MoO4 1090 996 Wurcite 583(10) 594(3.3) 977 232(1.7) 228(6.4) 595 897 340(5.4) 810 (0.6) H2O 1616(7.2) 1616(2.7) 1620 (9) 882 806(2.4) 883 (3.6) 1620 1601(7.9) 820 822(56) MoO4 692 857(1.7) 996 220(7) 664 887(53) 977 232(1.7) 228(2.9) 492 992(43) 897 340(5.4) 328(6.2) 339 995(5.3) 882 282(2.4) 806(2.4) 486(1.8) 317 820 328(2.6) 822(56) 664(3.6) 289 692 810(5.8) 857(1.7) 799(2.4) 225 664 818(4.4) 887(53) 814(2) NaNO3 112 (1.1) 108 (0.4) 492 891(3.7) 992(43) 879(2.6) 1391 182 (5.5) 714 (4) 339 995(5.3) 995(5.6) 1368 1095 (4.8) 1038 (4.2) 317 1068 1362 (4.7 1389(3.2) 289 725 1668 (1.8) 225 193 103 1678

Fe (NO3)3 1038 (4.2) 1038

118 Goethite may be produced via two mechanisms (Van Der Kraan and Medema 1969; Tronc et al., 1992; Jolivr et al., 1992): (i) transformation of ferrihydrite via Fe(II) sorption (ii) dissolution of Fe(OH)2 in strong alkali - solution forming Fe(OH)3 , oxidized with strong oxidant such as H2O2 to

Fe(OH)3, and converted into amorphous ferric oxyhydroxide FeOx(OH)3-2x with precipitation of goethite α- FeOOH. The sample of 9.64 mg Fe, shows the goethite α-FeOOH together with the lepidocrocite γ-FeOOH in the presence of the two Fe(II) minerals: wuestite Fe(1-x)O and Fe(OH)2 (Mackay, 1961; Missawa et al., 1974). The goethite bands become not well identified at higher Fe (II) concentrations in solution (11.71 and 14.82 mg Fe). Also, the concentrations of Fe (II) in solution control the path way of the reaction and the final transformation reaction products; lepidocrocite and maghemite or lepidocrocite and the mixed oxide magnetite Fe3O4 at higher Fe(II) / Fe(III) molar ratios. The transformation reaction is triggered by adsorption of the iron (II) on γ-FeOOH at pH above 7.3 (Kiyama and Takada 1974; Kaneko and Katsura 1979; Tamura et al., 1981). Tamura et al. (1983) suggested that the transformation of γ-FeOOH to

Fe3O4 takes place via a dissolution-precipitation process, while, under the same conditions, goethite α-FeOOH was not transformed to Fe3O4. Misawa (1973) supported this information, since, he suggested that γ-FeOOH has about 104-5 times large solubility with comparison of goethite α-FeOOH. The reaction of transformation can be written as:

+ Fe (II) + 2 γ-FeOOH Fe3O4 + 2H

The Raman spectra of Fe (III) minerals obtained from the mixture solution containing 11.71 mg Fe indicates the presence of the oxide maghemite γ- Fe2O3. The transformation reaction was followed by magnetite (not identified in this sample) transformation to maghemite γ-

Fe2O3. Magnetite is a redox active Fe oxide, at fast aerial oxidation (if it 119 was formed), lepidocrocite is preferentially formed and transforms into maghemite and goethite, thereafter. Goethite formation increases with the NaOH concentration in solution. Goethite was presumably formed through reconstructive dissolution / crystallization reactions that can be written as (He and Traina, 2007):

- - Fe3O4 + OH + H2O = γ- Fe2 O3 + Fe (OH)3

- + Fe(OH)3 + 1/2 O2 + 2H = α- FeOOH + 2H2O

In strong alkali solutions amorphous ferric oxyhydroxide precipitates by aerial oxidation of Fe(II) iron (Misawa et al., 1969 and 1971):

Dissol. ax amorphous ferric - Fe(OH)2 Fe(OH)3 Fe(OH)3 aq oxyhydroxide α- FeOOH FeOx(OH)3-2x

Also due to dissolution of γ-FeOOH in strong alkali, the amorphous ferric oxyhydroxide precipitate with an increase in the concentration of Fe(III) iron in solution. The transformation would proceed as follows:

Disso. amorphous ferric γ-FeOOH Fe(III) oxyhydroxide α- FeOOH FeOx(OH)3-2x

Table (3.10) shows Raman bands of identical samples each containing

0.6 g Al and 1.0 g MoO3 dissolved in 34 ml 4 M NaOH solution containing different amounts of 3.44, 7.58, 8.61, 9.64, 11.71 and 14.81 mg

Fe and 0.5 ml 10 % H2O2 as an oxidant. Raman spectra of Fe(III) minerals precipitated from 1.0 g MoO3 show no frequency bands of the Fe (III) oxides hematite and / or maghemite at the low concentrations of 3.44 and 7.58 mg Fe in the reaction mixture solutions, respectively. It was supposed 99 2- that Mo-MoO4 anions may be retained onto the formed Fe (III) oxides

120 minerals in the crystal external hydration sphere. Where, the retained molybdate (VI) anions were readily eluted with 3.5 M NaNO3 solution of pH 9.5. Detection of the oxyhydroxides: lepidocrocites and goethites supported the mechanism of Mo (VI) anions adsorption on the Fe (III) oxides forming outer sphere surface complexes through, at least, one water molecules between the adsorbed molybdate molecule (Na2MoO4) and the oxide surface. It is observed that the intensity of H2O bands was decreased with the adsorption of 99Mo-molybdate anions from solution, under the specified experimental conditions (viz. 3.4.3 .2.2). Increasing the total Fe dose from 8.61 to 14.82 mg, Raman spectra indicated the presence of goethite and / or lepidocrocite with soluble

Fe(OH)2 and H2O in solution with and without 1.0 g MoO3. At the 11.71 and 14.81 mg Fe in presence of MoO3, Raman spectra indicated the presence of magnetite combined with siderite (high percent of Fe(OH)2).

3.4.2.2.2. Effect of NaOH concentration: Table (3.11) shows Raman spectra frequency bands of ferric (III) transformations from 34 ml 4 M NaOH solution containing constant concentration of 7.58 mg Fe oxidized with 0.5 ml H2O2 in presence and absence of 1.0 g MoO3 and adjusted with concentrated HNO3 acid to 0.5 M NaOH. In the absence of molybdate (VI) anions, the ferric iron oxides: hematite and maghemite disappeared from the Fe (III) iron transformations products as a function of HNO3 acid treatment. The progressive transformation products by the action of nitrate anions, were gradual increases in goethite, magnetite, ferrihydrite and Fe(II) iron in the form of

Fe (OH)2 and wurcite. Generally, goethite and magnetite formation increase in presence of nitrate anions in agreement with (He-Hun et al.,

2003). High concentration of nitrate anions (i.e, 3.5 M NaNO3 / 0.5 M NaOH solution) enhanced reversible coagulation effects of Fe (III) iron

121 transformations. The re-charging of large coagulated Fe (III) mineral particles resulted in highly dispersed fine colloids penetrating the 45 µm Millipore filter. Transformation of ferrihydrite to goethite from 0.5 M NaOH appears to be re-hydration by water introduced from NaOH neutralization with nitric acid. Re-transformation of ferrihydrite at 0.5 M NaOH increased the elimination % of 59Fe via increasing the sorption rate of 59Fe onto the fine particles of the highly developed surface area ferrihydrites. Also, this inflection point had an important effect on the elimination profile of 99Mo radionuclide. Contrary to the previously obtained and the above results and discussions of Raman spectra, the presence of molybdate (VI) anions in the reaction mixture solution (0.5 M NaOH / 3.5 M NaNO3) enhanced the formation of well identified Fe (III) oxide minerals (i.e, hematite and maghemite) and hardly identified ferrihydrites bands. Frequencies of the corresponding Fe (II) bands were not identified and instead higher H2O,

Fe(NO3)3 and nitrate bands were enhanced in agreement with (He-Hun et al., 2003). The retention of molybdate (VI) was ~ 0.933 to 5.76 % with increase of goethite contribution in the formed precipitates. At 0.5 M NaOH, the concentration of nitrate anions highly increased that of molybdate anions in solution. Competition reactions between nitrate and normal molybdate anions favoured the release of molybdate attached onto the hematite external surface of hydration and hindered its transformation to goethite and ferrihydrite. The retention % of 99Mo decreased from 5.76 to 1.53 %.

3.4.2.2.3 Effect of H2O2 concentration: Table (3.12) shows Raman spectra frequency bands of the corresponding Fe(III) minerals from solutions containing 0.6 g Al, 30

122 mg FeCl3.6H2O and 34 ml 4 M NaOH containing different volumes of

0.25, 0.5 and 1.0 ml 10 % H2O2 solution. In absence of 1.0 g MoO3, the obtained Raman spectra showed that both the oxidant concentration and the rate of Fe (II) oxidation to Fe (III) iron control the final transformation reaction products. At low oxidant concentration, 0.25 ml H2O2, the well identified mixed oxide of Fe3O4 (magnetite) and the Fe (II) species of

Fe(OH)2, wurcite and siderite were detected. However ferrihydrite frequency bands and Fe (II) iron species were detected, ill identified frequency bands of lepidocrocite were detected. On the other hand, new Fe ( III) iron mineral at the frequency bands corresponding to feroxyhytes δ- FeOOH was detected. Its formation is favored from strong alkali solution at high rates of oxidation (Missawa et al 1974; Carlson and Schwertmann, 1980). Transformations of Fe (III) iron to hematite is prevented in presence 2+ 2+ 2+ of M cations such as Zn and Fe at high Fe (II) and / or low H2O2 concentrations (He-Hun Jang 2003). At high oxidant concentration of ≥

1.0 ml H2O2, hematite and maghemite together with high intensity of the highly hydrated ferrihydrite minerals were identified. Transformation reactions of ferrihydrites, maghemite and goethite at high H2O2 concentration into hematite α- Fe2O3 may be enhanced by the pre-thermal treatment of the dissolution reaction mixture solutions just before Fe (II) oxidation to Fe (III) iron (Table 3.4). The detection of hematite due to Fe (III) minerals transformation at ambient room temperature was only verified after several months of aging. Table (3.12) proves that oxidation of Fe (II) iron (i.e, 1.37 mg Fe from

Al foil in addition to 30 mg FeCl3.6H2O) in 34 ml 4 M NaOH solution containing 1.0 g MoO3 with different volumes of 0.5 and 1.0 ml 10 %

H2O2 solution results in disappearance of Raman frequencies characteristic of Fe (III) oxide minerals. It is a supporting evidence that adsorption of 2- MoO4 anions onto the formed Fe (III) oxide minerals (hematite and / or

123 maghemite) may be achieved via outer sphere complexation through H2O molecules. As much as chemical composition of the reaction mixture solution favors the adsorption of molybdate (VI) anions, the preformed ferric oxides minerals are apparently or truly transformed into ferric oxyhydroxides (i.e, goethite). For example, compare the results with and without molybdate anions and specially the results of NaOH titrated with concentrated HNO3 acid (Tables. 3.10, 3.11 and 3.12). It must be noted that equal total volumes of the reaction mixture solutions (say, 34 ml) containing variable volumes of H2O2 solutions does not mean only different concentrations of the oxidant but also different rates of oxidation of the Fe(II) species to Fe (III) species which may affect the kinds and properties of the transformation products.

3.4.3. Adsorption behavior of 99Mo-molybdate (VI) anions: 3.4.3.1. Retention of 99Mo-molybdate (VI) anions: Fig. 3.8 (curve b) proves that there is a loss in the initial 99Mo 99 - radioactivity due to MoO4 retention onto the precipitated Fe(III) minerals via oxidation of the 1.37 mg Fe from 0.6 g Al wrapper. The amount of retained 99Mo-molybdate (VI) onto the formed precipitate was calculated from the areas under the 739 keV gamma-ray energy peak of 99Mo in solutions before and after precipitation of Fe(III) minerals. However the 99Mo-99mTc (parent-daughter) couple was, almost, in radioactive equilibrium, the well identified gamma-ray energy peak of 99mTc was not considered in the calculations of 99Mo-molybdate (VI) retention (and / or recovery) because of the time required to attain the radioactive equilibrium (~ 23 h) and the interference between the 140 keV of 99mTc and the 145 keV of 141Ce radionuclides. The remaining 99Mo-molybdate (VI) in the supernatant was found to be ~ 99.03 % of its initial concentration in the 99Mo-molybdate (VI) solution with a loss of ~ 0.97 % due to retention onto

124 the formed Fe(III) precipitate. Variation of 99Mo-molybdate (VI) loss as a function of chemical composition of the reaction medium is investigated in the following subsections.

3.4.3.1.1. Effect of total iron dose: Fig. 3.22 (curves a, b, c, d, e and f) shows gamma-ray spectra of 99Mo- molybdate (VI) supernatants at initial concentrations of 0.721, 3.99, 5.08, 6.17, 6.71, 7.80 x 10-3 M Fe measured after cooling time of 8 day from the end of irradiation for 200 s, respectively. Fig. 3.23. shows the effect of initial Fe concentration in the reaction mixture solution on the retention of 99Mo-molybdate (VI) anions onto the formed Fe(III) iron minerals. Retention ratios of ~ 1.0 % 99Mo were obtained in the range from 0.721 to 3.99 × 10-3 M Fe (i.e, 1.37 to 7.58 mg Fe). This indicates that the adsorption of molybdate (VI) anions from the solution is more or less independent of the amount of formed Fe (III) minerals. Thereafter, the retention % of 99Mo was sharply increased with increasing the total concentration of Fe to reach a maximum value of ~ 7.8 % 99Mo-molybdate (VI) at ≥ 6.71 × 10-3 M Fe. Except for, increasing the total fed dose of iron further than 3.99 × 10-3 M Fe, the consequently predominating highly dispersed colloidal particles of hematite and ferrihydrites respectively, may be transformed abruptly to new states of lower dispersion, such as maghemite, goethite, lepidocrocite and magnetite, according to the chemical composition of the medium and thermal pretreatment (Tables 3.9 and 3.12 and Fig 3.19). At concentrations ≥ 4.53 × 10-3 M Fe, instability with consequent fast coagulation occur due to preferential formation of goethite minerals and goethite plus lepidocrocite mixtures at the higher concentrations of Fe. Remarkable sharp retention value of ~ 7.86 % 99Mo- molybdate (VI) was manifested at concentration ≤ 7.80 × 10-3 M Fe.

125

Tc (140 keV) m Mo( 181 keV) keV) 181 Mo( 99 9 Tc(280 keV) keV) Tc(280 m Mo (366 keV) Mo (740 keV) Mo (778 keV) Mo (822 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) 99 99 99 99 99 99 99 99 (a)

Tc (140 keV) m Mo(181 keV) 99 99

Cs (795 keV) Mo (740 keV) Mo (778 keV) Mo (822 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV)

99 99 134 99 99 99 99 Tc(280 keV) keV) Tc(280 m Mo (366 keV) Cs( 604 keV) keV) 604 Cs( Zn (1115 keV) keV) (1115 Zn keV) (1120 Sc

99 99 Co( 1173 keV) Co( 1332 keV) (b) 134

65 46 60 60

Tc (140 keV) m keV) 181 Mo(

99 99 (c) Tc(280 keV) keV) Tc(280 Cs( 604 keV) keV) 604 Cs( m Mo (366 keV) Cs (795 keV) 99 99 134

Mo (740 keV) Mo (778 keV) Mo (822 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) 99 99 134 99 99 99 99 Fe ( 1099 keV) keV) (1115 Zn keV) (1120 Sc Co( 1173 keV) Co( 1332 keV0

59 65 46 60 60

units y

Zn (1115 keV) keV) (1115 Zn Tc (140 keV) 65

m keV) 181 Mo( 99 99 Tc(280 keV) keV) Tc(280 arbitrar m Mo (366 keV) , 99 99 (d) Cs( 604 keV) keV) 604 Cs( Cs (795 keV) Mo (740 keV) Mo (778 keV) Mo (822 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) 134 99 99 134 99 99 99 99 Fe ( 1099 & keV) (1120 Sc Co( 1173 keV) Co( 1332 keV0 59 46 60 60 er channel

Tc (140 keV) m keV) 181 Mo( p 99 99 Tc(280 keV) keV) Tc(280 (e) Cs (795 keV) m Mo (366 keV) Mo (740 keV) Mo (778 keV) Mo (822 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) Cs( 604 keV) keV) 604 Cs( 99 99 99 99 134 99 99 99 99

134

Fe ( 1099 keV) keV) (1115 Zn keV) (1120 Sc Co( 1173 keV) Co( 1332 keV0 59 65 60 60 46

Counts

)

) 181 keV 181

( Tc (140 keV)

m Mo 960 keV 960 ( 99 99 (f) Cs (795 keV) Mo (740 keV) Mo (778 keV) Mo (822 keV) Mo (880 keV) Mo (920 keV) Mo Tc(280 keV) keV) Tc(280 99 99 134 99 99 99 99 m Mo (366 keV) 99 99 Cs( 604 keV) keV) 604 Cs( 134 Fe ( 1099 keV) keV) (1115 Zn keV) (1120 Sc Co( 1173 keV) Co( 1332 keV0 59 65 60 60 46

Gamma-ray energy keV

Fig. (3.22) Gamma-ray spectra of 99Mo-molybdate (VI) supernatants in presenc of (a) 0.72, (b) 3.99 and (c) 5.08, (d) 6.71, (e)7.26 and (f) 7.80 x 10-3 M Fe in solution measured after cooling time of 8 days from the end of irradiation for 200 s.

126

Mo retention % 99

Concentration of Fe, M

Fig. 3.23. Effect of total concentrations of Fe on the retention % of 99Mo- molybdate (VI) anions onto the formed Fe(III) minerals precipitates.

127 3.4.3.1.2. Effect of NaOH concentration: The elimination behavior of 99Mo radionuclide was calculated from the gamma-ray spectra in Fig. 3.24. (curves a, b, c and d) of the 99Mo- molybdate (VI) supernatants of 4.0, 2.0, 1.0 and 0.5 M NaOH solution titrated with the addition of concentrated nitric acid measured after a cooling time of 8 days from the end of irradiation for 200 s, respectively.

Fig. 3.25 shows the effect of NaOH / NaNO3 concentrations on the retention % of 99Mo-molybdate (VI) anions onto in-situ precipitated Fe(III) minerals from 34 ml molybdate (VI) solutions containing total dose of 7.58 mg Fe oxidized with 0.5 ml H2O2 solution (10 % w/v) in initial solutions of ~

4 M NaOH titrated with concentrated HNO3 acid to different alkali molarities. Decreasing the concentration of NaOH in solution from ~ 4.0 M to around 1.0

M NaOH, by addition of concentrated HNO3 acid, was accompanied with a sharp increase in the retention % of molybdate (VI) anions from ~ 1 to ~ 6 % in the presence of 3.99 x 10-3 M Fe, respectively. The concentration of ~ 4 M NaOH solution enhanced both of the solubility and dispersion stability of the formed colloidal fine particulates of hydrous ferric oxide. This exerts strong repulsion forces between the OH-,s on the highly charged colloidal Fe(III) minerals and the molybdate (VI) anions in solution leading to only external attachment of the molybdate (VI) anions in the electric double layer by Van der Wall, s forces with ~ 0.933 % 99Mo retention. Addition of nitric acid to the molybdate (VI) solutes passing through 2 M and virtually to ~ 1.25 M NaOH, the amounts of Fe soluble / dispersed colloidal particles decrease with consequent increase in the retention % of 99Mo onto the formed Fe(III) minerals. This is due to transformation from predominated ferrihydrite minerals at ~ 4 M NaOH solution into more favorable chemically stable goethite minerals from alkali / nitrate solutions. However addition of more coagulating reagent (nitric acid) decreased the concentration of OH- anions and stability of the colloidal goethite particulates in solution, the amount of

128

(140 keV) Tc 99m Mo & 99 99Mo(181 keV) 99Mo(181

Tc (281 keV) Zn (1115 keg) 65 99m

Cs (795 keV) (a) Mo(739 keV) Mo(778 keV) Mo(7820 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) 99 99 134 99 99 99 99

Mo& Mo(366 keV)

99 99

Fe (1099keV) (1332keg) Co Fe (1099) Sc (1120 keg) Co (1173 keg) Cs (604 keV)

59 46 60 59 60

134

Tc (140 keV) Tc 99m Mo & 99 99Mo(181 keV) 99Mo(181

Tc (281 keV) (b) 99m

Cs (795 keV) Mo(739 keV) Mo(778 keV) Mo(7820 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) Mo& Mo(366 keV) Zn (1115 keg) 99 99 134 99 99 99 99 99 99 65

Cs (604 keV) 134

Fe (1292keV) (1332keg) Co Fe (1099) Sc (1120 keg) Co (1173 keg) 59 46 60 59 60

units y Tc (140 keV) Tc

99m arbitrar , ) Tc (281 keV) Mo & 99 99Mo(181 keV) 99Mo(181 99m

Cs (795 keV) 604 keV Zn (1115 keg) Mo(739 keV) Mo(778 keV) Mo(7820 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) ( Mo& Mo(366 keV) 65 99 99 134 99 99 99 99 99 99

Cs (c) 134

er channel p Fe (1292keV) (1332keg) Co Fe (1099) Sc (1120 keg) Co (1173 keg) 59 46 60 59 60

Counts

Tc (140 keV) Tc

99m

Mo & 99 99Mo(181 keV) 99Mo(181

Tc (281 keV) Cs (795 keV) Mo(739 keV) Mo(778 keV) Mo(7820 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) 99 99 134 99 99 99 99 Cs (604 keV) Zn (1115 keg) 99m

65 134

Mo& Mo(366 keV) 99 99

(d) Fe (1292keV) (1332keg) Co Fe (1099) Sc (1120 keg) Co (1173 keg) 59 46 60 59 60

Gamma-ray energy keV

99 Fig. 3.24. Gamma-ray spectra of the Mo-molybdate (VI) supernatant at concentrations of (a) 4.0 (b) 2.0 (c) 1.0 and (d) 0.5 M NaOH solutions measured after 8 day from the end of irradiation for 200 s.

129

Mo retention % 99

Concentration of NaOH, M Fig. 3.25. Effect of NaOH concentration on the retention of 99Mo-molybdate (VI) anions onto the formed Fe(III) minerals

130 retained molybdate (VI) anions was drastically decreased from 5.76 to 1.53 % with decreasing the alkali concentration from ≤ 1.0 to 0.5 M NaOH / 99 NaNO3. While the adsorption of Mo radionuclide onto the formed Fe(III) minerals is expected to increase, a state of competition reaction between - the increasing concentrations of NO3 anions and the low concentration of molybdate (VI) anions in the reaction mixture solutions may be created in - favor of the NO3 anions. The behavior of colloidal Fe(III) mineral precipitates in solutions of different NaOH concentrations (Fig. 3.21) offers a considerable base for interpretation of Fig. 3.25. From Fig. 3.25 it can be concluded that ~ 4 and 0.5 M NaOH solutions of ~ 3.5 M NaNO3 may be considered as proper eluents of the molybdate (VI) anions retained onto the formed Fe(III) minerals.

3.4.3.1.3 Effect of H2O2 concentration: Depending on the 99Mo radioactivity and the solution pH value, addition of 99 H2O2 as an oxidizing agent ensures oxidation of the radiation-induced Mo reduced species, if they are present, together with oxidation of Fe(II) iron to Fe(III) iron. The corresponding retention behavior was calculated from the gamma-ray spectra of Fig. 3.26 (curves a, b and c) corresponding to the supernatants of 99Mo-molybdate (VI) solutes containing 0.25, 0.5 and 1.0 ml

H2O2 measured after cooling time of 8 days from the end of irradiation for 200 s, respectively. Fig. 3.27 shows the effect of H2O2 concentration in the reaction mixture solution on the retention of 99Mo-molybdate (VI) anions onto the formed Fe(III) minerals. The retention of 99Mo-molybdate (VI) anions was decreased with increasing the oxidant volumes from 0.25 to 0.5 ml H2O2 (10

% w/v) solution which, virtually may be extended up to ~ 0.65 ml H2O2 corresponding to retention values of 2.95, 0.933, and ~ 0.6 % 99Mo- molybdate (VI), respectively. As predicted from Fig. 3.16 and the corresponding discussions, volumes ≤ 0.25 ml H2O2 may be insufficient for complete oxidation of Fe (OH)2 to Fe(III) with the consequent predominance 131

Tc (140 keV) Tc 99m Mo & 99 99Mo(181 keV) 99Mo(181

Tc (281 keV) Zn (1115 keg) 65 99m Cs (795 keV) Mo(739 keV) Mo(778 keV) Mo(7820 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) 99 99 134 99 99 99 99

Mo& Mo(366 keV)

99 99 (a) Cs (604 keV)

Fe (1292 keV) keV) Fe (1292 (1332keg) Co Fe (1099) Sc (1120 keg) Co (1173 keg) 134 59 46 60 59 60

(140 keV) Tc 99m

units (b)

y Mo & 99 99Mo(181 keV) 99Mo(181

Tc (281 keV) Zn (1115 keg) 99m 65 Cs (795 keV) Mo(739 keV) Mo(778 keV) Mo(7820 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) 99 99 134 99 99 99 99

arbitrar Mo& Mo(366 keV) , 99 99

Cs (604 keV) Fe (1292 keV) keV) Fe (1292 (1332keg) Co Fe (1099) Sc (1120 keg) Co (1173 keg) 59 46 60 59 60 134

er channel p

Tc (140 keV) Tc

99m Counts

Mo & 99 99Mo(181 keV) 99Mo(181

Tc (281 keV)

99m (c) Cs (795 keV) Zn (1115 keg) Mo(739 keV) Mo(778 keV) Mo(7820 keV) Mo (880 keV) Mo (920 keV) Mo (960 keV) 65 99 99 134 99 99 99 99

Mo& Mo(366 keV) 99 99

Cs (604 keV) Fe (1292 keV) keV) Fe (1292 (1332keg) Co Fe (1099) Sc (1120 keg) Co (1173 keg) 134 59 46 60 59 60

Gamma-ray energy keV

Fig. 3.26. Gamma-ray spectra of the supernatant of 99Mo-molybdate (VI) solute oxidized with volumes of (a) 0.25 (b) 0.5 and (c) 1.0 ml of (10 % w/v) H2O2 solution measured after cooling time of 8 days from the end of irradiation for 200 s.

132

Mo retention % 99

Volume of H2O2, ml 99 Fig. 3.27. Effect of H2O2 concentration on the retention of Mo-molybdate (VI) anions onto the formed Fe (III) minerals via oxidation of 3.99 x 10-3 M Fe(II) in 34 ml 4 M NaOH solution.

133 of low dispersed magnetite minerals. It was found that, the loss of Mo (VI) increased from ~ 0.97 % to 7.857 % of the initial 99Mo radioactivity with increasing the total amount of Fe (II) in solution at constant 0.5 ml H2O2

(Fig 3. 23). Increasing the volume of added H2O2 solution to ≥ 0.65 ml is accompanied with Fe(III) transformation into highly dispersed ferrihydrite minerals and loss of the molybdate (VI) anions was confined between ~ 2.95 and 0.6 % of its initial value with increasing the volume of added

H2O2 from 0.25 to 0.65 ml. On the other hand, further increases up to 1.0 99 ml H2O2 re-raised the loss of Mo-molybdate (VI) to 1.79 % of the initial 99 Mo radioactivity. Analytical reagent Fe2O3 of particle size > 10 µm packed in the form of chromatographic column was found to be a good 99 sorbent for activation Mo-molybdate (VI) solute acidified with HNO3 acid to pH 3. The dynamic method exchange capacity was found to be 0.1 g Mo per 100 g Fe2O3 (Bulbulian and Sarantin, 1966).

3.4.3.2. Desorption of 99Mo-molybdate (VI) anions: Fig. 3.28 (curves a, b and c) shows gamma-ray spectra of the Fe(III) minerals formed in presence of 1.37 mg Fe (from the Al wrapper) before washing, after first and second washing with 5 ml 0.5 M NaOH solution measured after a cooling period of 8 days for 100 s, respectively. Analysis of the spectra indicated that washing twice of the formed Fe(III) mineral each with 5 ml 0.5 M NaOH solution was almost sufficient for complete recovery of the retained 99Mo-molybdate (VI) anions. Fig. 3.29 (curves a and b) shows gamma-ray spectra of 1.0 ml of the corresponding first and second washing filtrates measured after a cooling period of 8 days for 100 s. Analysis of the spectra support complete recovery of the 99Mo-molybdate (VI) anions retained onto the formed Fe(III) precipitate in the first 5 ml washing filtrate. Fig. 3.29 (curves c and d) shows gamma-ray spectra of the filtrates measured after a cooling period of two months for 200 s. It is observed that-

134

(a) )

Tc ( 140.5 keV) Mo (778 keV) Mo (778 934 keV 99 99m ( Nb ( 912 keV) Nb Mo, Mo (181 keV) ) Sc (880 keV)

99 99 92m 46 92m

keV La( 328 keV ) Mo (366 keV) 99 140

La( 487 keV ) Mo (740 keV) Nb(765 keV) 1847 99 95 ( 140 Fe(1292 keV) Co (1332 keV Fe(1099 keV) Sc (1120 keV) Co ( 1173 keV

59 60 59 46 60 Nb La (1597 keV) 140 92m

units

Tc ( 140.5 keV) Mo (778 keV) Mo (778 99 99m arbitrar

, (b) Nb ( 934 keV) Mo, Mo (181 keV) Nb ( 912 keV) Sc (880 keV) 99 99 46 92m 92m Fe(1099 keV) Sc (1120 keV) Co ( 1173 keV Fe(1292 keV) Co (1332 keV La( 487 keV ) 59 46 60 La( 328 keV ) 59 60 Mo (740 keV) Nb(765 keV) 140 99 95 140 Nb (1847 keV) La (1597 keV) 140 92m

er channel p

Counts Tc ( 140.5 keV)

9 ) 99m (c Nb ( 934 keV) Nb ( 912 keV) keV Sc (880 keV) Mo, Mo (181 keV) 46 92m 92m 99 99 Fe(1099 keV) Sc (1120 keV) Co ( 1173 keV La( 328 keV ) Fe(1292 keV) Co (1332 keV 59 46 60 1847 La( 487 keV ) ( 140 59 60 Nb(765 keV) 140 95 Nb La (1597 keV) 140 92m

Gamma-ray energy, keV

Fig. 3.28. Gamma-ray spectra of the Fe (III) mineral precipitates (a) before and after (b) first washing (c) second washing each with 5 ml 0.5 M NaOH solution measured after a cooling period of 8 day for 100 s.

135

Tc (140.5 keV) 99m

Mo, Mo (181 keV) 99 99 (a) Mo(740 keV) Mo(777 keV) 99 99 Co ( 1332 keV) Co ( 1173 keV) 60 60 Mo(366 keV)

(b) Tc (140 keV) 99m , Co ( 1332 keV) Co ( 1173 keV) Nb (934 keV) 60 60

92m units y arbitrar ,

92m Counts

(d) Co ( 1332 keV) Nb (934 keV) Co ( 1173 keV) 60 60

92m

Gamma-ray energy, keV

Fig. 3.29. Gamma-ray spectra of 1.0 ml of the (a) first and (b) the second washing filtrate of

Fe(III) precipitate measured after a cooling period of 8 days for 100 s, and (c and d)

of the same filtrates measured after a cooling period of two months for 200 s.

136 the recovered 99Mo-molybdate (VI) radioactivity will be mainly contaminated with the released 92mNb and 60Co radionuclides of the second washing filtrate. Thus, washing of the formed Fe(III) precipitate only with 5 ml 0.5 M NaOH solution is recommended to achieve recovery yield of ~ 100 % of the initial 99Mo-molybdate (VI) solute compared with ≥ 99 % recovery yield without washing.

3.4.3.2.1. Factors affecting desorption of 99Mo-molybdate (VI) anions: Desorption, as well as adsorption reactions at a constant temperature are functions of the adsorbent kind, sorbate and chemical composition of the eluating medium (eluent). Recovery of the retained 99Mo-molybdate (VI) anions from the formed Fe(III) minerals was investigated as a function of the initial total amount of Fe in the system, e. g, 1.37, 4.47, 7.58and 11.71 mg Fe using 0.5 M NaOH and / or distilled water as eluents.

3.4.3.2.1.1. Effect of the initial amount of iron: Elution performance of the 99Mo-molybdate (VI) anions with 5 ml 0.5 M NaOH solution was investigated as a function of kind of the formed Fe (III) minerals precipitated from 1.37, 4.47, 7.58 and 11.71 mg Fe, oxidized with

0.5 ml H2O2. Figs. 3.29 (curves a, b, c and d) and 3. 30 (curves a, b, c, d, e and f) light the corresponding 99Mo elution behavior and radionuclidic purity. The calculated data are listed in Table (3.13). Fig 3.30 (curves a and b) shows gamma-ray spectra of the first and second washing filtrates of the formed Fe (III) mineral of 4.47 mg Fe precipitated from 34 ml ~ 4 M NaOH solution containing 0.5 ml H2O2 and curves (c and d) depicts the corresponding spectra of the formed precipitate of 7.58 mg Fe measured after a cooling time of 8 days for 100 s. Recovery yields of 99Mo-molybdate (VI) anions were found to be ~ 0.683 and ~ 0.2604 % in the first and second washing filtrates of 4.47 mg Fe with release of 60Co (0. 0271 and 0.100) and 92mNb (0.019 and 0.047) radionuclides into the molybdate (VI) eluates. No 99Mo radioactivity 137

Tc (140Tc keV)

99m (a)

Mo & (181keV) Mo 99 99

Nb (934 keV) Nb Mo (366keV) Mo (739 keV) Mo (778 keV) Mo ) (920keV Mo (960keV) Mo 92m 99 99 99 99 99

Co (1173 keV) Co (1332 keg)Co

60 60

(b) Tc (140Tc keV) 99m

Mo & (181 keV) Mo 99 99 Mo (739 keV) Mo (778 keV) Mo Nb (934 keV) Nb 99 99 92m

Co (1173 keV) Co (1332 keg)Co 60 60

(c)

(934 keV) Nb Tc (140Tc keV) Mo ( 739 keV) Mo ( 778 keV) ) (920keV Mo (960keV) Mo Mo ( 181 keV) 99 99 99 92m 99 99m 99 (1332 keg)Co Co (1173Co keV) 0 60

Countsper channel, arbitrary units

(d) Co (1332 keg)Co Tc (140Tc keV) Co (1173keV) Co Mo (181 keV) Mo 0 60 99m 99 Nb (934 keV)

Mo (739 keV) Mo (778 keV) Mo 92m 99 99

(e) Tc (140Tc keV) Mo (181 keV) Mo 99m 99

Mo (366keV) Mo Nb (934 keV) Nb 99 Co (1332 keg)Co Mo (739 keV) Mo (778 keV) Mo ) (920keV Mo (960keV) Mo Co (1173 keV) Co

0 60 99 99 99 99 92m

(f) Tc (140Tc keV) Mo (181 keV) Mo 99m 99 Mo ( 739 keV) Mo ( 778 keV)

99 99

Nb (934 keV) Nb Co (1332 keg)Co Co (1173 keV) Co 92m 0 60

Gamma-ray energy, keV

st nd Fig .3.30 Gamma-ray spectra of the 1 and 2 washing filtrates of the formed Fe (III) minerals of (a and b) 4.47, (c and d) 7.8 and (e and f) 11.71 mg Fe each with 5 ml 0.5 M NaOH measured after a cooling period of 8 days for 100 s.

138

Table (3.13). The contribution % of 99Mo, 60Co and 92mNb radionuclides into the washing filtrates of Fe(III) minerals formed at different iron total fed doses and eluted using 2 x 5 ml 0.5 M NaOH solution and / or distilled water. Experimental conditions Elimination % Remained Total iron Radionuclide Retention, Eluent First Second Total % dose, mg identified % 5 ml 5 ml (10 ml) 1.37 mg Fe 99Mo 0. 97 0.5 M 0.97 00.00 0.97 00.00 60Co 79.71 NaOH 0.0544 0.1374 0.1918 75.5182 92mNb 100 0.155 0.163 0.318 99.682 4.47 mg Fe 99Mo 0. 9434 0.5 M 0.683 0.2604 0.9434 00.00 60Co 85.21 NaOH 0. 0271 0.100 0.1271 85.0829 92mNb 100 0.019 0.047 0.066 99.934 99Mo 0. 933 0.5 M 0.703 0.193 0.896 0.037 60Co 94.20 NaOH 0.263 0.00454 0.2675 93.9325 7.58 mg Fe 92mNb 100 0.0138 0 0.0138 99.9862 99Mo 0. 933 Distilled 0.07094 0.00298 0.07392 0.859 60Co 94.20 water 0.0122 0.208 0.2202 93.98 92mNb 100 0 0.126 0.126 99.874 11.71mg 99Mo 4.67 0.5 M 3.298 1.1498 4.4478 0.2222 Fe 60Co 97.72 NaOH 0 0.0934 0.0934 97.6266 92mNb 100 0.0187 0.039 0.0577 99.9423

remained onto the surface of the washed precipitate after the second washing. Recovery of 99Mo-molybdate (VI) anions was found to be ~ 0.703 and ~ 0.193 % in the first and second washing filtrates of 7.58 mg Fe with release of 60Co (0.263 and 0.00454) and 92mNb (0.0138 and 0.00) radionuclides into the molybdate (VI) eluate, respectively. The amount of 0.037 % 99Mo was strongly retained onto the interior surface of the precipitate and did not release into the eluate of the second washing. Fig. 3.30 (curves e and f) shows the corrsponding spectra formed of 11.71 mg Fe. Lower recovery yields of ~ 3.298 and ~ 1.1498 % 99Mo-molybdate (VI) anions were obtained in the first and second washing filtrates with corresponding release of 60Co (0.00 and 0.0934) and 92mNb (0.0187 and 0.039) radionuclides. Higher amount of 0.2222 % 99Mo was strongly retained onto the surface of the formed precipitate and could not be released by washing with 10 ml 0.5 M NaOH solution.

139 3.4.3.2.1.2. Effect of eluent: Fig. 3.31 (curves a and b) shows gamma-ray spectra of the washing filtrates of the precipitate formed of 7.58 mg Fe and eluted with 2 x 5 ml distilled water measured after a cooling time of 8 days for 100 s. Fig. 3.31 (curve a) indicates that negligible recovery of ~ 0.07094 % 99Mo- molybdate (VI) initially present in solution and 0.00 and 0.0122 % 92mNb and 60Co were obtained in the first 5 ml washing filtrate. Only ~ 0.00298 % 99Mo-molybdate (VI) anions were recovered with marked release of 0.126 and 0.208 92mNb and 60Co radionuclides in the second 5 ml washing filtrate as shown in Fig. 3.31 (curve b). The highest amount of 0.859 % 99Mo-molybdate (VI) anions was strongly retained onto the surface of the formed precipitate and does not elute with 2 x 5 ml distilled water. The measured pH values of the first and second filtrates were 9.5 and 6.6, respectively. While the first washing filtrate was colorless, the second washing filtrate was colored faint-yellow.

3.4.3.2.2. Adsorption reactions mechanism: At initial total doses of 1.37 up to 7.58 mg Fe, the loss of 99Mo- molybdate (VI) anions from solution by retention onto the formed Fe (III) minerals may be mainly via inclusion in the hydration water surrounding the precipitated Fe (III) minerals. The 99Mo-molybdate (VI) loss has decreasing values from ~ 0.97 to 0.933 % of its initial concentration with increasing the total amount of Fe in solution. Increasing the total amount of fed Fe to ≤ 7.58 mg and washing the formed Fe (III) mineral precipitates with 2 x 5 ml 0.5 M NaOH solution, the distribution and the total amount of recovered Mo(VI) in the different eluate fractions depend on the total concentration of Fe in the reaction mixture (Table 3.13). The degree of dispersion and stability of the condensed Fe (III) precipitates decreased with low, but appreciable, distribution of the recovered 99Mo radionuclide

140

Tc( 14keV)

99m (a) Mo, keV0 (181 Mo 99 99 units y arbitrar ,

(b) er channel

p Tc( 14keV) 14keV) Tc( 99m Nb ( 934 keV) keV) 934 ( Nb Mo, keV0 (181 Mo 92m 99 99 Co ( 1173 keV) keV) 1173 ( Co keV) 1332 ( Co 60 60

Counts

Gamma-ray energy, keV

Fig 3.31. Gamma-ray spectra of the 1st and 2nd washing filtrates of the formed Fe (III) minerals of 7.58 mg Fe with 2 x 5 ml distilled water measured after a cooling period of 8 days for 100 s.

141 between the two fractions of the washing filtrate compared with the highly dispersed precipitate of the lowest total Fe dose and highest recovery yield of 99Mo radionuclide. While the first fraction of the water filtrate was colorless solution of pH 9.5, the IEP of Fe (III) precipitates is ≤ pH 8.4. The second fraction was colored pale-yellow (i.e, hydrous ferric oxide) solution with a slightly acidic pH value of 6.6. At the high pH value, the precipitate acted as a cation-exchanger releasing the negatively charged molybdate (VI) anions into the washing filtrate and strong fixation of Co2+ and Nb5+ cations onto its negatively charged surface. At the lower pH value, the surface of the Fe (III) mineral was positively charged and acted as an anion-exchanger with consequent strong fixation of Mo(VI) anions and repulsion of Co2+ and Nb5+ cations from the minerals surface into the solution. Higher piptization of the Fe (III) minerals in distilled water than in 0.5 M NaOH solution may be responsible for formation of very fine colloidal Fe (III) oxides particles capable of penetrating into the filtrate, with the consequence changes in color to pale-yellow and high recovery yields of Nb and Co. The sorption behavior of molybdate (VI) anions onto the formed Fe(III) minerals precipitates can be predicted from the sorption capacity (calculated as: amount of retained molybdate / mg of total Fe dose) and the corresponding desorption behavior. Fig. 3.23 explores three distinct retention behavior regions, namely, gradual decrease, in the region from 1.37 to 7.58 mg Fe corresponding to retention values of ~ 0.71 to 0.123 % Mo / mg Fe followed by gradual increases in the sorption capacity in the region from 8.61 to 14.82 mg Fe with retention values of 0.23 up to 0.53 % Mo / mg Fe. Finally, a semi-plateau of 99Mo retention % was obtained irrespective of increasing the amount of fed Fe dose into the system, at the fixed oxidant concentration, with consequent decreasing sorption capacity. Identification data of the formed Fe (III) minerals (Tables 3.10, 3.11 and

142 3.12) and the desorption data (Table 3.13) show that in the first region from 1.37 up to the inflection point at 7.58 mg Fe the sorption of 99Mo- molybdate (VI) anions may take place via inclusion in the surrounding water of crystallization of the α-Fe2O3, which is influenced by increasing the amount of amorphous ferrihydrites on the expense of hematite and maghemite minerals, as represented by:

Fe2O3.x H2O + y Na2MoO4 Fe2O3.(x- 2y)H2O.2y(OHNa).(H2MoO4)y

Where Fe2O3 is the corresponding formed Fe (III) oxide mineral α-and γ-Fe2O3, xH2O water of crystallization and yH2O water of inclusion.. In the region of ≥ 7.58 mg Fe concentrations, sorption occurs as a function of cation-exchange mechanism between Na+ cations of the + Na2MoO4 molecule and H ions of water of hydration or of active sites on the surface of the formed Fe (III) oxyhydroxide minerals followed by - neutralization of the residual positive charges with MoO4 anions via Van der Walls forces according to (Amphlett, 1964; Dey et al., 2004):

- + + Fe2O3.x H2O + Na2MoO4 Fe2O3.(x-2) H2O.2(OH Na ) (MoO4) + 2H or: + 2 FeOOH + Na2MoO4 (FeOO)2Na2MoO4 + 2H

Neutralization of the negatively charged colloidal particles lead to a definite accumulation of the dispersed nucleons to larger particles size by Van der Walls forces. Occlusion adsorption occurs by entrapment of the molybdate anions surrounding the early formed fine particles into the interior of the growing particle of precipitate with further growth of the particle size. It is noticed that adsorption process took place by internal and external occlusion verified by washing and recovery of the sorbed molybdate. Table (3. 13), shows that, the remained molybdate (VI) anions 143 on the formed Fe (III) precipitates of 1,37, 4.47, 7.58 and 11.71 mg Fe increased after the second washing with 5 ml 0.5 M NaOH solution in the order 00.00, 00.00, 0.037 and 0.2222 %, respectively. It is observed that the transformation into mixed Fe (II) and Fe (III) oxide minerals (i.e, magnetite) dose not participate in the adsorption of Mo (VI) anions from solution.

3.4.4.Purification assessment from cross-contaminant radionuclides: Concentrations of the cross-contaminants in neutron activation-99Mo solutions are very small that their precipitation is prevented, even if this concentration exceeds the solubility of the formed insoluble material. The presence of a carrier substance which is added in substantial amounts may helps the trace elements to be co-precipitated more or less quantitatively, if necessary. For example, the elimination of 59Fe radionuclide from activation 99Mo-molybdate (VI) solution with the addition of ferric chloride as an isotopic carrier and non-isotopic carrier for co-precipitation of traces of Mn(OH)3, Co(OH)3 etc, and Al(OH)3 for traces of Fe(OH)3 and

Cr(OH)3 where isotopic dilution mechanism dose not participate in the separation reaction. In the present study, Fe(OH)3 represents an isotopic- and non isotopic-carrier for elimination of trace contaminant radionuclides including 59Fe and 60Co, 51Cr, 54Mn, 65Zn, 95Zr, 95& 92mNb, 175&181Hf, 124Sb and *Ln as cross-contaminant radionuclides present in activation 99Mo- molybdate (VI) solute dissolved in concentrated NaOH solutions, respectively. As mentioned above, due to the high radioactive levels of 99Mo radionuclide, gamma-ray spectra measured after a short cooling time, from the end of irradiation, can not enable carrying out quantitative and even qualitative assessment of the decontamination feasibility of the 99Mo- molybdate (VI) solutes via in-situ precipitation of Fe(III) minerals. More or

144 less satisfactory qualitative separation descriptions could be deduced from the gamma-ray spectra of Fig.3. 8 (curve b), as a result of pre-concentration of the detected cross-contaminant radionuclides onto the formed Fe (III) minerals together with low level 99Mo radioactivity. Figs. 3.9, 3.10 and 3.11 (curves a, b and c) are the basic data for quantitative assessment of the 99Mo-molybdate (VI) solute purification via in-situ precipitation of

Fe(III) iron in the form of Fe(III) minerals from 30.5 ml 4 M NaOH solution containing 1.37 mg Fe (from the Al wrapper) oxidized with 0.5 ml

H2O2 solution (10 % w/v). Generally, the corresponding purification data can be qualitatively and quantitavely classified into three categories: 1. Complete purification, i.e, ~ 100 % elimination of 140La, 141Ce, 152, Eu (i.e, lanthanide group elements), 92m Nb and 54Mn radioactivities from the 99Mo-molybdate (VI) solute. 2. Partial purification with the elimination of 35 % 51Cr, 68 % 59Fe, 50 % 46Sc, 80 % 60Co and 95Nb radionuclides initially present in the 99Mo- molybdate (VI) solute. 3. Nil detected purification from the radionuclides of 65Zn, 95Zr, 181,175Hf, 124Sb and 134Cs. Except for Cs+, the remaining radionuclides may form soluble colloidal anions of zincate, zirconate, hafinate and antimonite in concentrated ~ 4 M NaOH solution. Table (3.14) compiles the 99 purification data of Mo-molybdate (VI) solute (1.0 g MoO3 + 0.6 g Al dissolved in 30 ml 4M NaOH solution) from the corresponding cross- contaminant radionuclides via in-situe precipitation of the dissolved 1.37 mg Fe chemical impurity of the Al wrapper with the addition of 0.5 ml

H2O2 solution (10 % w/v). The elimination of contaminant radionuclides from the 99Mo-molybdate (VI) solute in 4 M NaOH solution is governed by their distribution ratios between the aqueous and the formed solid of Fe (III) minerals which permit their co-precipitation and / or post separation. The distribution ratio of an element in trace amount between the two phases

145 depends on its chemical state in solution and the physico-chemical properties of the sorbent at constant temperature. Changing these parameters can influence the separation (elimination) efficiency of elements from each other, help to predict the state of microelements in solution and undergo a comparison of their properties with analogous elements. The parameters of initial total Fe dose and concentrations of

NaOH in the reaction mixture solution adjusted with HNO3 acid and H2O2 as an oxidant were investigated in the following topics.

Table (3.14): Purification of 99Mo-molybdate (VI) anions via in-situ precipitation of 1.37 mg Fe

dissolved in 30 ml 4 M NaOH solution oxidized with 0.5 ml H2O2 (10 % w/v), thereafter.

Radionuclide Elimination, % Remaining, %

140La 100 00.00 ١٤١Ce 100 00.00 152Eu 100 00.00 54Mn 100 00.00 92mNb 100 00.00 95Nb ≥ 97 Variable tracer ≤ 3 60Co 80 20 59Fe 67.5 32.5 46Sc 50 50 51Cr 35 65 99Mo ≤ 0.97 ≥ 99.03 65Zn 00.0 100 95Zr 00.00 100 181Hf 00.00 100 124Sb 00.00 100 134Cs 00.00 100 86Rb 00.00 100

3.4.4.1. The lanthanides and 92mNb radionuclides: Lanthanides (III) are the most predominating oxidation state in aqueous

solution. The insoluble hydroxides La(OH)3, Ce(OH)3 and Eu(OH)3 have definite insoluble hexagonal structure and are not merely hydrous oxides as Fe (III). When a precipitating agent is added to a mineral solution of the

146 following lanthanides (III) cations, they start precipitation as follows (Lee, 1991):

Eu (OH)3 > Ce (OH)3 > La (OH)3

The hydrolysis and precipitation from alkali solutions starts at pH values of

6.82 , 8.1 and 8.35 as insoluble Eu(OH)3, La(OH)3 and Ce(OH)3. In the presence of H2O2 solution, Ce (III) may be oxidized to the tetra valent Ce

(IV) state which hydrolyses and precipitates as CeO2 and / or Ce2O4.nH2O at pH value of 2.65 (Vickery, 1953; Stevenson and Nervik 1961; Cotton and Wilkinson, 1979; Vogel,s, 2001). In agreement with the above discussions, Figs. 3.9, 3.10 and 3.11 show that traces of insoluble 140La

141 141 141 152 (OH)3, Ce(OH)3 and Ce2O4.nH2O or CeO2 and Eu(OH)3 were almost completely co-precipitated with the 1.37 mg Fe from 4M NaOH solution as insoluble colloids carried down with the predominated hematite and ferrihydrites Fe(III) minerals. The elimination % of 140La, 141Ce and 152Eu radionuclides may be enhanced by the large surface area of the in-situ precipitated Fe (III) minerals. Since the ionic radius of Fe3+ is much smaller than that of La3+, Ce3+ and Eu3+, formation of anomalous mixed crystals / or solid solutions of similar oxidation states and initial molecular structures, Fe(OH)3 and Ln(OH)3 may be expected. Formation of insoluble mixed oxide of lanthanum niobate LaNbO4 (Glasstone, 1955; Cotton, 1979; Lee, 1991; Greenwood, 1997; NEA, 1997) may also be considered as a dual co-precipitation / purification of the molybdate (VI) solute from lanthanum and niobium radionuclides. The most stable oxidation state of niobium i.e, Nb (V) starts hydrolysis at pH 5 and completes precipitation at pH value ≥ 7 in the form of hydrous oxide Nb2O5. n H2O (Agarawel, 1987; Lee, 1991). Fused oxides in strong alkali hydroxide or carbonate form soluble niobates Na3[NbO4] (Cotton,

147 1979; Agarawel, 1987; Lee, 1991). The release of ~ 0.318 % 92mNb into the washing filtrates of 1.37 mg Fe with 2 × 5 ml 0.5 M NaOH solution (Table 3.13) indicates that more than one mechanism is included in the retention of Nb (V) radionuclides from the 4 M NaOH solution onto the formed Fe

(III) minerals. Readily elutable niobate anions, Na3NbO4, may be retained by mechanical incorporation onto the formed Fe (III) precipitates more or 2- st nd less similar to the MoO4 anions. Gamma-ray spectra of the 1 and 2 washing filtrates of the formed Fe (III) minerals Fig. 3.29 support week retention of easily released molybdate (VI) anions and strong retention / with partial releasing of niobate and cobaltate anions from the exterior hydration water sphere of the slowly precipitated particulates of hematite and ferrihydrites minerals. A partition distrebution mechanism dominates between the hydration water sphere of Fe (III) minerals and the surrounding aqueous phase of 0.5 M NaOH as an eluent compared to complete desorption of the retained 99Mo-molybdate (VI) anions. Van der 3- Walls electrostatic adsorption forces of NbO4 anions may persist competition reactions exerted by the bulk concentration of molybdate anions as a result of the higher formal charge:

+ 3- . - + 3- + Fe(III)ox.xH2O(S) + 3Na (aq) + NbO4 (aq) Fe(III)ox (x-3)H2O.3(OH .Na )NbO4 (S)+ 3H (aq)

Elimination co-precipitation of Nb (V) from the molybdate solution in the form of insoluble hydrous oxide Nb2O5.nH2O is more predominating. - 92m Compared to soluble MoO4 anions, ≥ 99.682 % of the retained Nb radionuclide was strongly fixed onto the formed Fe(III) minerals in the form of insoluble oxide. Inclusion with a less contribution and occlusion to a great extent onto the growing particles of Fe (III) precipitate, followed by further particles growth may be the main elimination mechanisms of 92mNb radionuclides from the 99Mo-molybdate (VI) solute. The niobates form insoluble mixed metal oxides, LnNbO4, which may be formed in 148 presence of the Ln elements (Cotton, 1979; Greenwood, 1997). Mostafa (2002) separated 92m&95Nb from fission product solutions of uranium by adding 20 mg FeCl3 to the solution and adjusted the pH value to ~ 7 to entrap *Nb radionuclides in the form of hydrous oxide, Nb2O5. n H2O onto the formed precipitate of Fe (III).

The elimination % of the individual lanthanide (i.e, 140La, 141Ce and 152Eu) and 92mNb radionuclides via in-situ precipitation of the formed Fe(III) minerals from ~ 4M NaOH solution was not influenced by increasing the amount of total fed Fe dose, the alkali concentration adjusted with the addition of concentrated HNO3 and H2O2 concentration. It was independent of the kind and degree of dispersion of the formed Fe(III) minerals in solution. If Ce (III) was oxidized to Ce (IV), it may be scavenged as insoluble particulates of Ce2O4.nH2O by the formed Fe(III) minerals in a manner similar to occlusion of Nb2O5.nH2O.

3.4.4.2. 95Zr / 95Nb and 175&181Hf radionuclides: In aqueous solutions, niobium and zirconium radionuclides tend to form colloidal species which adsorb onto the surfaces of containers walls, dust particles, etc. and contribute to erratic behavior of zirconium and niobium in their separation processes (Etherington, 1958). Excluding any isotopic effect, niobium-95 radionuclide may obey distribution ratios and chemical behaviors similar to the above mentioned mechanisms and elimination % of 92mNb from the Mo (VI) solutes at similar experimental conditions. It was found that the elimination % of 95Nb is smaller than that of 92mNb and decreases with the elapsed time intervals between filtration and radiometric analysis of the 95Zr containing supernatants. For example, no measurable elimination of 95Zr was found at a total dose of 1.37 mg Fe. Re-growth of the 95Nb radionuclide in solution, as a radioactive decay

149 product of the 95Zr parent, may be responsible of the lower elimination % of 95Nb than 92mNb from the molybdate (VI) solute. Zirconium (IV) reacts with sodium hydroxide forming a white gelatinous precipitate of Zr(OH)4. Zirconium and hafnium have very similar chemical properties and their mutual separation from solution is difficult. The solubility of ZrO2 and HfO2 increases proportionally with the concentration of NaOH in the range from 1 - 9 M NaOH forming soluble zirconate and hafinate anions according to (Sheka and Pevzner, 1960).

- - ZrO2 +2H2O + OH → Zr (OH)5

- - HfO2 +2H2O + OH → Hf (OH)5

From ~ 4 M NaOH solution, 95Zr and 181,175Hf remained in the 99Mo- molybdate (VI) supernatants as negatively charged zirconate and hafinate colloids without noticeable elimination onto the 1.37 mg Fe formed Fe (III) minerals. Trace concentrations of zirconate and hafinate anions with small formal charges can not compete with the bulk concentration of Mo (VI) in solution and / or the other high formal charge anions to adsorb onto the surface of formed Fe (III) minerals from solution. Fig. 3.32 shows the effect of total initial iron concentration in 34 ml 4M

NaOH solution containing constant 0.5 ml H2O2 (10 % w/v) on the elimination % of 95Zr / 95Nb , 92mNb and 175&181Hf from the molybdate (VI) solute. As above mentioned, complete elimination of 92mNb was achieved from 4 M NaOH solutions irrespective of the total iron fed dose in the reaction mixture solution. On the other hand, a higher concentration of 3.44 mg Fe was necessary to enhance abruptly increased elimination % of 95Zr with consequent improved elimination of the generated 95Nb radionuclide from the 99Mo-molybdate (VI) solutions. Elimination % of 95Nb radionuclide increased from 87.25 % at 0.721 × 10-3 M Fe to 98.1 % at 7.8 × 10-3 M Fe. At low Fe concentrations, the soluble zirconate and hafinate anions may be

150

Elimination %

Concentration of total fed dose of Fe, M

92m Fig. 3.32. Effect of total initial concentration of iron dose on the elimination % of ■ Nb, ● 95Nb, ▲95Zr and▼175&181Hf from the molybdate (VI) solutes in 34 ml 4 M NaOH solution oxidized with 0.5 ml H2O2.

151 inferred unsuccessful competition with the molybdate, niobate and cobaltate anions to neutralize the partially charged Naδ+ available adsorption sites on the external electric double layer of the formed Fe(III) oxide particles. On the other hand, dispersion time of the formed Fe(III) mineral colloids is decreased with increasing the amount of added Fe to meet with nucleation of neutrally formed Zr and Hf hydroxides in solution leading to hydrolytic (i.e, condensation) adsorption mechanism onto the surface of the formed Fe (III) oxyhydroxide precipitates. Due to kinetic reasons predicted from their adsorption behavior sequences from solutions of different alkali concentrations (Fig. 3.33):

95Zr-Zirconate ≥ 175&181Hf-hafinate

The adsorption mechanism of Zr and Hf depend on the sorbent amount and kind according to the equation:

FeOOH + M (OH)n FeOO.M (OH) n-1 + H2O

Fig. 3.33 shows the effect of NaOH concentration on elimination % of 95Zr / 95Nb, 92mNb and 175,181Hf from the molybdate (VI) solute. It is observed that the elimination % of 92mNb was not influenced by NaOH concentration. 95Nb exhibited gradual elimination increases as a result of remarkable increases in the elimination % of 95Zr from solutions of decreasing NaOH concentrations. While zirconium shows low elimination rates, fast rates were manifested by 175,181Hf radionuclides with decreasing the alkali concentration. The observed increase in the elimination rates may be due to kinetics of conversion of the soluble zirconate and hafinate anions to molecular Zr(OH)4 and Hf(OH)4 hydroxides at lower - concentrations of NaOH from NO3 solutions by adding concentrated nitric 152

Elimination %

Concentration of NaOH, M

Fig. 3.33. Effect of NaOH concentration on the elimination % of ■ 92mNb, ● 95Nb, 95 175&181 ▲ Zr and▼ Hf from molybdate (VI) solutes containing 7.58 mg Fe and 0.5 ml H2O2

153 acid, and predominance of the Fe (III) oxyhydroxide minerals, such as goethite.

Fig. 3.34 shows the effect of H2O2 concentration in solution on the elimination % of 95Zr / 95Nb, 92mNb and 175,181Hf from the molybdate (VI) solute. The eliminations values of 99Mo were slightly decreased in the order of 97.6, 97 and 96.8 % 95Nb with the corresponding elimination decreases 87, 82 95 and 80 % Zr at 0.25, 0.5 and 1.0 ml H2O2, respectively. Sharp decreases 175,181 from 47 to 12.5 and 11 % Hf were obtained with increasing the H2O2 concentration from 0.25 ml to 0.5 and 1.0 ml, respectively. It was found that concentration of H2O2 in solution strongly affect the stability and dispersion time of the formed Fe (III) minerals as well as the elimination % of 59Fe radionuclide. The formation of highly dispersed Fe (III) colloids such as of hematite may be increased with increasing the oxidant concentration.

3.4.4.3. 54Mn, 51Cr and 124Sb radionuclides: Figs 3.9, 3.10 and 3.11 show that complete elimination values of ~ 100 % 54Mn, 34.85 % 51Cr and nil of 124Sb were achieved from the molybdate (VI) solute at the previously specified experimental conditions. The elimination behavior of Mn, Cr and Sb may be controlled by the oxidation state, solubility and / or amphoteric properties of the elements in solution besides to kind and properties of the formed Fe (III) minerals. In sodium hydroxide solution Mn forms a white precipitate of manganese (II) hydroxide insoluble in excess of alkali:

2+ - 2Mn + 2OH → Mn(OH)2↓

It is rapidly oxidized on exposure to air or with H2O2 to form brown hydrous manganese oxide, MnO(OH)2 insoluble in excess of NaOH solution (Agasyan, 1980; Aggarwal, 1987; Lee, 1991; Greenwood, 1997; Vogel,s, 2001).

154

Elimination %

Volume of H2O2, ml 92m 95 95 Fig. 3.34. Effect of H2O2 concentration on the elimination % of ■ Nb, ● Nb, ▲ Zr and ▼ 175&181Hf from molybdate (VI) solute in 34 ml 4 M NaOH solution containing

7.58 mg Fe.

155 2Mn (OH)2↓ + O2 → 2 MnO(OH)2↓

2Mn (OH)2↓ + H2O2 → 2 MnO(OH)2↓ + H2O

As well as, manganese (III) is an unstable oxidation state rapidly reduced to manganese (II). Insolubility of the hydrous oxides of manganese (II) and (IV) in excess of NaOH solutions demonstrates complete purification of the 99Mo-molybdate (VI) solutes from 54Mn radionuclide via co-precipitation. Complete elimination of 54Mn from the 99Mo-molybdate (VI) solute may be - a prove of absence of soluble permanganate MnO4 anions from the reaction mixture solutions containing 0.5 ml H2O2. The formed precipitates 54 54 of Mn (OH)2 and MnO(OH)2 may be co-precipitated with the formed Fe(III) minerals to form mixed crystals or solid solutions of the type analogous isodimorphism ( of similar ionic radii and chemical formula). The ionic radius of Mn3+ and Mn2+ are nearly close to that of Fe3+ and Fe2+ . The isomorphism may also be predicted from chemical composition and similarity of the average charge on the formed precipitates (Nesmeyanov,1974 and 1984; Agasyan, 1980; Aggarwal, 1987; Lee, 1991; Greenwood, 1997; Clifford et al., 1999; Johnstone et al., 2001; Vogel,s 2001). Sodium hydroxide solution precipitates chromium (III) hydroxide as the following:

3+ - Cr + 3OH → Cr(OH)3 ↓

The formed precipitate is amphoteric, and dissolves in excess of the alkali to tetrahydroxochromate (III) anion (i.e, chromite ion) (Agasyan, 1980):

- - Cr(OH)3 ↓ + OH ↔ [ Cr(OH)4]

156 which is rapidly oxidized with H2O2 to form yellow soluble chromate (VI) anions according to (Schwarzembach, 1962; Tsuchiya and Umayahara, 1963; Agasyan, 1980; Aggarwal, 1987; Vogel,s 2001).

- - 2- 2 [Cr(OH)4] + 3H2O2 + OH → 2CrO4 + 8H2O

Complete oxidation of tetrahydroxochromate (III) to chromate (VI) anions with 0.5 ml H2O2 (10 % w/v) may be excluded, because of the need to excess concentration of hydrogen peroxide (Agasyna, 1980). Figs 3.9, 3.10 and 3.11 ( curves a, b and c) indicate partial eliminations of chromium from the Mo(VI) solute in 4 M NaOH solutions. Oxidation of Cr(II) to Cr(III) results in co- precipitation of ~ 35 % of 51Cr in the form of chromium (III) hydroxide with the formed Fe (III) minerals in a mixed solid-solution (via analogous isomorphism) due to similarity in the ionic radii and chemical composition. Compared to Mn and Ln hydroxides, Cr3+ size is nearly equal to the original size of Fe3+ ion in the precipitated particles (Agasyan, 1980; Clifford, et al., 1999; Johnstone, et al., 2001). The remaining 65 % of 51Cr radionuclide may be present as soluble tetrahydroxochromate (III) and / or chromate (VI) anions soluble in 4 M NaOH solutions. Two series of antimony salt solutions are known, Sb(III) and Sb(V). In sodium hydroxide solutions, Sb(III) forms white precipitates of hydrated antimony oxide, Sb2O3.xH2O, soluble in concentrated NaOH solutions forming antimonite (III) anions:

3+ - 2 Sb + 6 OH → Sb2O3 ↓ + 3H2O - - Sb2O3 ↓ + 2OH → 2SbO2 + 2H2O

3- and antimony (V) forms the antimonite (V) anions SbO4 in the form of hexahydroxoantimonate:

157 - - Sb2O5 + 2OH + 5H2O ↔ 2[Sb(OH)6]

- - The SbO2 and / or Sb(OH)6 anionic species may be essentially present in concentrated 4 M NaOH solution. Irrespective of its oxidation state, 124Sb anions were not able to compete with the bulk concentration of sodium molybdate (VI) anions of the higher formal charge to adsorb from the reaction mixture solution on the hydration layer on the surface of the formed Fe (III) minerals. Fig. 3.35 shows the effect of initial total Fe dose on elimination % of 54Mn, 51Cr and 124Sb from the 99Mo-molybdate (VI) solutes in 34 ml 4M 54 NaOH solution containing 0.5 ml H2O2. Complete elimination of Mn radionuclide, as Mn(OH)2, Mn(OH)3 and / or MnO(OH)2 with the formed Fe(III) minerals was achieved irrespective of the concentration of Fe in the system. The elimination % of 51Cr and 124Sb radionuclides were found to be concentration dependent and gradually increased with increasing the total amount of fed iron dose in the system. The corresponding elimination % were found to be ~ 34.85 and 0.0, respectively, at the initial amount of 1.37 mg Fe (i.e 0.721 × 10-3 M Fe) in solution. Increasing the amount of fed Fe decreases the time of coagulation and apparent complete precipitation and increases the amount of formed Fe (III) minerals in the form of oxyhyroxides. The maximum elimination % of 51Cr and 124Sb hydroxides were found to be ~ 92.41 and 57 % at 5.08 and 7.26 × 10-3 M Fe, respectively. In homogeneous systems, Cr(VI) reduction by aqueous Fe(II) at high pH value proceeds very quickly. Elimination of 51Cr may be increased with increasing Fe (II) / Cr (VI) molar ratio in the reaction mixture solution, where Cr (III) precipitates from the solute with the Fe (III) minerals and Cr (VI) remains as anionic species

(Yongtlanhe, 2003). In concentrated NaOH solution Sb2O3 and Sb2O5 may - - form the anionic species SbO2 and Sb (OH)6 . As the amount of added Fe increases at controlled oxidation conditions (i.e, 0.5 ml H2O2), competing

158

100

Elimination % 40

0 -3 012345678 x 10 Concentration of Fe, M

Fig. 3.35. Effect of initial total iron concentration on the elimination % of ■ 54Mn, ●51Cr and ▲124Sb from the molybdate (VI) solutes in 34 ml 4 M NaOH solutions containing 0.5 ml H2O2 (10 % w/v).

159 accelerated reactions occur with consequent increased elimination % of 124Sb radionuclide. More or less similar to the adsorption of 51Cr radionuclide, the time of coagulation and precipitation decreases, the amount of formed Fe (III) precipitate increases with preferential transformations towards Fe (III) oxyhydroxides and mixed Fe (III) / Fe (II) minerals, respectively, and - kinetic equilibria between the couples Sb2O3 / Sb2O5, Sb2O3 / SbO2 , - - Sb2O5 / Sb(OH)6 and Sb2O5 / SbO4 may be established. The gradual increase in 124Sb elimination agrees with an adsorption reaction mechanism. The presence of a maximum adsorption plateau may indicate the absence of [Sb (III) Sb (V)] redox reactions and the presence of equilibria between the oxides and soluble anions in solution. Fig. 3.36 shows the effect of NaOH concentration in solution on the elimination % of 54Mn, 51Cr and 124Sb radionuclides from the 99Mo- molybdate (VI) solutes. The elimination % of 54Mn keep the value of ~ 100 % irrespective of NaOH concentration in solution. Insoluble hydroxides of 54 54 54 Mn may be co-precipitated in the form of Mn(OH)2, Mn(OH)3 and 54 MnO(OH)2 with the formation of mixed crystals with the Fe(OH)3 transformation minerals. There are sharp increases in the elimination % of 51Cr and 124Sb radionuclides with decreasing the concentration of NaOH in solution from 4 to 2 M, followed by slower increases in the range from 2 to 0.5 M NaOH. This is due to decreased dispersion and progressive coagulation of the colloidal Fe(OH)3 minerals with decreasing the concentration of NaOH in solution. In addition to, amphoteric solubility of chromium and antimony anionic species, decreases with decreasing the concentration from ~ 4.0 to 0.5 M NaOH with consequent increases of the corresponding elimination. These results support our previous discussion concerning the elimination behavior of 51Cr and 124Sb radionuclides at variable concentrations of Fe. 160

100

40 Elimination %

0 0.00.51.01.52.02.53.03.54.04.5 Concentration od NaOH solution, M

Fig. 3.36. Effect of NaOH concentration on the elimination % of ■ 54Mn,● 51Cr and ▲124Sb from 34 ml molybdate (VI) solute containing 7.58 mg Fe and 0.5 ml H2O2 (10 % w/v).

161 Fig. 3.37 shows the effect of H2O2 concentration in solution on the elimination % of 54Mn, 51Cr and 124Sb radionuclides from the 99Mo- molybdate (VI) solutes. It is observed that Mn (II) or Mn (III) were not completely or partially oxidized, by increasing the concentration of H2O2 to - form soluble MnO4 anions, with complete elimination from the molybdate

(VI) solute as Mn (OH)2, Mn (OH)3 and / or MnO(OH)2 species onto the formed Fe (III) minerals. On the other hand, a sharp decrease in the elimination % of 51Cr was obtained due to oxidation of the tetrahydroxochromate anion from solution to chromate and / or dichromate anions and predominance of repulsion forces due to formation of Fe (III) oxides at high H2O2 concentrations rather than oxyhydroxides at low H2O2 concentrations in solution. The elimination % of 124Sb radionuclide was gradually decreased with increasing the concentration of H2O2 in the - Mo(VI) solute. The predomination of SbO2 species at low H2O2 concentration enhanced the elimination % of 124Sb from the Mo (VI) - - solution more than the SbO2 and Sb(OH)6 species predominating at high - H2O2 concentration, due to lower competition with OH anions surrounding - - the Fe (III) minerals The hydrated radius of [Sb(OH)6] >> (SbO2 ) anions (Ana G. Leyvajulieta et al. 2001; Ann-Kathrin Leuz et al 2006).

3.4.4.4. 59Fe, 60Co, 65Zn and 46Sc radionuclides: Cobalt (II) ions present in acidic aqueous nitrate solutions are precipitated by sodium hydroxide solution forming a blue basic salt:

2+ - - Co + OH + NO 3 → Co(OH) NO3 ↓

In excess of sodium hydroxide, the basic salt converts to a pink precipitate of cobalt (II) hydroxide with solubility product of 5.92×10-15 (Lee, 1991; Vogel,s 2001; Greenwood, 1997):

162

120

100

60 Elimination % Elimination 40

0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 Volume of H O , ml 2 2

54 51 Fig. 3.37. Effect of H2O2 concentration on the elimination % of ■ Mn ● Cr and 124 ▲ Sb from molybdate (VI) solute in 34 ml 4 M NaOH solution containing 7.58 mg Fe.

163 - - Co(OH) NO3 ↓ + OH → Co(OH)2 ↓ + NO3

Cobalt (II) hydroxide slowly transfers at pH value of 6.8 to a brown-black cobalt (III) hydroxide after exposure to air (Bate and Leddicotte, 1961; Vogel,s, 2001):

4 Co(OH)2 ↓ + O2 + H2O → 4Co(OH)3 ↓

Rapid oxidation of Co(II) to Co(III), with H2O2 results in penetration of more cobalt (III) hydroxide to the solution (Vogel,s, 2001). It was found that about 20 % of the formed 60Co (III) precipitate penetrated the 45 µm Millipore filter into the 99Mo-molybdate (VI) solution with partial elimination of ~ 80 % 60Co (Table 3.5). Elimination of 60Co from the Mo (VI) solute may occur by co-precipitation of cobalt (III) hydroxide

Co(OH)3 from 4 M NaOH solution in the form of mixed crystal during growth of the formed fine particles of Fe (III) minerals and / or by - - mechanical incorporation (inclusion) of the soluble Co(OH)3 and Co(OH)4 anions as well as the niobate and molybdate anions in the crystallization water sphere surrounding the particles of formed Fe (III) oxide minerals. (Gayer and Garrett, 1950; Gordon and Schreyer, 1951 and 1955; Agasyan, 1980). The latter suggestion is supported with the results of ~ 0.1918 % 60Co release on washing the formed Fe (III) minerals with 2 x 5 ml 0.5 M NaOH solution (Figs. 3.29 and 3.30 and Table. 3.13).

Scandium dissolves in NaOH solutions librating H2 gas:

Sc + 3NaOH + 3H2O → Na3[Sc(OH)6] + 3/2H2 ↑

The scandate salt Na3[Sc(OH)6].2H2O crystallizes from concentrated ≥ 8 M NaOH solutions (Cotton, 1979; Agarawel, 1987; Lee, 1991;

164 Greenwood, 1997). Scandium Sc(OH)3 as well as Fe (III) hydroxides, don't appear to exist as definite compounds, but as the basic oxide ScO.OH. It is amphoteric like Cr and aluminum. Thus, scandium may be eliminated from the 99Mo-molybdate (VI) solutes in 4 M NaOH solution by one or more of the following mechanisms:

1- Partial or nil crystallization as Na3[Sc(OH)6] . 2H2O salt, since the OH- ion concentration is much lower than 8 M NaOH.

2- Co-precipitation of the amphoteric Sc(OH)3, and / or the basic oxide ScO.OH, with the corresponding particles of Fe(III) oxyhydroxide minerals forming solid solution via isodimorphism (chemical composition and nearly similar ionic radii). 3- Inclusion of the dissociated basic oxide ScO.O- into the formed hydration layer sphere of Fe(III) oxides colloidal minerals. Inspite of the possible three elimination mechanisms, the elimination % of scandium from Mo (VI) solute via in-situ precipitation of Fe(III) minerals from 4 M NaOH solution containing 1.37 mg Fe (from the Al foil) oxidized by 0.5 ml H 2O2 (10 % w/v) was found to be only ~ 50 %. The crystallization of Na3[Sc (OH)6].2H2O and the basic oxides of Sc and Fe mechanisms are not favorable at the given experimental conditions. Zn forms in diluted NaOH solution a white amphoteric precipitate of zinc hydroxide soluble in excess of NaOH (Charles, 1976; Cotton, 1979; Agasyan, 1980; Agarawel, 1987; Lee, 1991; Greenwood, 1997):

2+ - Zn + 2OH Zn(OH)2↓ - 2- Zn(OH)2↓ + 2OH [Zn(OH)4]

It was found that soluble 65Zn-zincate anions were completely detected in the supernatant of the 99Mo-molybdate (VI) solute in the presence of highly dispersed Fe(III) oxides minerals.

165 Fig. 3.38 shows the effect of initial total amount of Fe in the reaction mixture solution on the elimination % of 60Co, 46Sc, 65Zn and 59Fe radionuclides from the 99Mo-molybdate (VI) solute. It observed that the elimination % of 59Fe, 46Sc and 60Co were gradually increased from ~ 67.5, 50 and 80 % to maximum eliminations of comparable values ~ 97.82, 96 and 98.15 with increasing the total amount of Fe in the system from 0.721 × 10-3 M Fe to 7.26 × 10-3 M Fe, respectively. At 0.721 x 10 -3 M Fe, 65Zn-zincate anions may be in competition with the molybdate, niobate and cobaltate anions to retain onto the formed Fe(III) oxides minerals. As the amount of added Fe increases, the dispersion of colloidal Fe(III) oxyhydroxides and the contribution of ferrihydrites which depend on the relative concentration of Fe 65 (II) / H2O2 will decrease leading to progressive adsorption sequences of Zn- zincate anions. Transformation of Fe (III) minerals into oxyhydroxide results in higher elimination % of Fe with increasing Fe in the system as previously discussed. Fig. 3.39 shows the effect of NaOH concentration in solution on the elimination % of 60Co, 46Sc, 65Zn and 59Fe radionuclides from the 99Mo- molybdate (VI) solute. There are more or less similar gradual increase in the elimination % of 59Fe and 60Co radionuclides with decreasing the concentration of NaOH in solution from 4 to 0.5 M NaOH. This is due to decrease of dispersion and rapid coagulation of the formed Fe(III) minerals with decreasing the concentration of NaOH in solution. Because of the amphoteric properties of scandium, their solubility decreases with decreasing the concentration of NaOH in solution with consequent increase in the corresponding elimination % from 4 to 0.5 M NaOH solution. At first, sharp increases in the elimination % were achieved with decreasing the concentration from 4 to 2 M NaOH then, it was slightly increased with decreasing the concentration from 2 to 0.5 M NaOH solution. Fig. 3.39 demonstrates, also, slow increases in the elimination % of 65Zn radionuclides with decreasing the alkali concentration in solution. The

166

100

40 Elimination %

012345678x 10 - 3 Total concentration of fed Fe, M

Fig. 3.38. Effect of total initial concentration of iron on the elimination % of ▼59Fe, O 46Sc, □60Co and ▲ 65Zn from the molybdate (VI) solutes in 34 ml 4 M NaOH containing 0.5 ml H2O2 (10 % w/v) .

167

100

40 Elimination %

0 0.00.51.01.52.02.53.03.54.04.5 Concentration of NaOH, M

59 46 Fig. 3.39. Effect of NaOH concentration on the elimination % of ▼ Fe, O Sc, 60 65 □ Co and ▲ Zn from the molybdate (VI) solute containing 7.58 mg Fe

and 0.5 ml H2O2 (10 % w/v)

168 observed increase in the elimination % is due to gradual and partial conversion of the soluble zincate to the corresponding insoluble hydroxide

Zn(OH)2 with decreasing the concentration of NaOH in solution to 0.5 M, by adding concentrated nitric acid to the 4 M NaOH solution.

Fig. 3.40 shows the effect of concentration of H2O2 in solution on the elimination of 60Co, 46Sc, 65Zn and 59Fe radionuclides from the molybdate

(VI) solute at different concentrations of H2O2 in 34 ml 4 M NaOH solution and constant total dose of Fe. A slight decrease in the elimination % of scandium in a pattern more or less similar to the decrease in precipitation of Fe(III) minerals was obtained. The formation of highly dispersed Co(III) hydroxides as well as of Fe(III) minerals were accompanied with slight decreases in the corresponding elimination % of 60Co and 59Fe radionuclides. The elimination % of 65Zn-zincate gradually decreased from 55 to 47 % due to formation of highly dispersed Fe(III) minerals of the oxide forms with increasing the volume of H2O2, i.e, with gradual decrease of the -OH sites of adsorption onto the formed Fe(III) minerals.

3.4.4.5. Radionuclides of the alkali metals 134Cs, 86Rb and 24Na : 134Cs, 86Rb and 24Na radionuclides may be present as the Cs+OH-, Na+OH- and Rb+OH- hydoxides in the molybdate (VI) solute. 134Cs, 86Rb were found to have no measurable adsorption affinity via cation-exchange reactions onto the formed Fe(III) minerals irrespective of their large ionic radii and positive charges. This was accounted for by the trace concentrations of Cs and Rb in solution compared to the macro-concentration of Na, of the smaller ionic radius, in the reaction medium. The expected elimination of 134Cs+ and 86Rb+ via cation-exchange mechanism was not detected under all the experimental parameters including total concentrations of Fe, H2O2 and NaOH in the reaction mixture solution adjusted with concentrated HNO3 acid titration.

169

100

40 Elimination %

0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 Volume of H O , ml 2 2

59 46 60 Fig. 3.40. Effect of H2O2 concentration on the elimination % of ▼ Fe, O Sc, □ Co and ▲ 65Zn from the molybdate (VI) solutes in 34 ml 4M NaOH solution containing 7.58 mg Fe.

170 It is attributed to unfavorable (i.e, irreversible) competition reactions between the micro-concentration of Cs+ and Rb+ cations and the macro- concentrations of Na+ cation from solution to exchange with the available exchangeable sites onto the formed Fe (III) minerals. 24Na radionuclide (T1/2 = 14 h) may be adsorbed, as the macro-concentration of Na+ cations. Its detection and identification was negligible due to its short half-life ≈ 14 hours and low radioactive contribution (specific activity) in the mixture solution.

171 3.4.Successive purification of the 99Mo-molybdat (VI) supernatant via in-situ precipitation of aluminum hydroxide at pH values of 9.5 and 5: After precipitation and separation of the formed Fe (III) minerals of the

1.37 mg Fe from 30.5 ml 4 M NaOH solution oxidized with 0.5 ml H2O2, the remaining supernatant contained 99.03 % of soluble molybdate (VI) anions in bulk concentration with sodium aluminates together with the cross-contaminant radionuclides of ~ 100 % 95Zr, (181, 175)Hf, 65Zn, 124Sb and 134Cs, variable contrebutions of the regenerated 95Nb, ~ 65 % 51Cr, ~ 20 % 60Co, ~ 32.05 % 59Fe, ~ 50 % 46Sc (Table. 3.14). Acidification of the supernatant by adding HNO3 acid, with mixing, until pH values of ~ 9.5 and 5 resulted in the formation of white gelatinous precipitates of Al(OH)3 matrices according to the following equation (Agasyan, 1980):

pH 10-5 - + AlO2 + H + H2O Al (OH)3 ↓

The purification potentials via in-situ precipitation of Al(OH)3 gel matrices of 99Mo-molybdate (VI) supernatants from the above mentioned residual cross-contaminant radionuclides, are investigated and discussed in the following sections.

3.5.1. In situ precipitation of Al (OH)3 matrix at pH 9.5: About 28.1 ml of the 99Mo-molybdate supernatant, remained after separation of the formed Fe (III) minerals and radiometric analysis of the initial and final solutions, was acidified by dropwise adding of concentrated

HNO3 acid with contentious mixing, to dissolve the formed white isopolymolybdates, until pH value of 9.5. A white heavy gelatinous precipitate of Al(OH)3 matrix was formed. Hydrolysis of Al ions is often represented as a sequential replacement of the water molecules by hydroxyl ions. It can also be thought of as a progressive deprotonation of water 172 molecules in the primary hydration shell. The simplest representation, omitting the hydration shell, for convenience, is written as (Agasyan, 1980; Richens, 1997; Gregory, 2001):

OH- OH- OH- OH- 3+ 2+ + - Al Al(OH) Al(OH)2 Al(OH)3 Al(OH)4 H+ H+ H+ H+

- 3+ The dominant species in solution changes from Al (OH)4 to Al over less than 1 pH unit. In contrast, the corresponding changes for Fe3+ which occurs over a range of > 8 pH units. Thus, Al (OH)3 is less stable than

Fe(OH)3, where its particles remain in a dispersed state for very short period of time and converts to a precipitate via fast neutralization by cations from solution with consequent rapid coagulations. In addition to, the concentration of Al3+ ions in the initial solution is high enough (30.5 ml containing 0.6 g Al) compared to Fe3+ contaminants (i.e, ~ 1.37 mg Fe) to help in coagulation and precipitation of measurable amount of the Al (OH)3 precipitate (Derygin, 1941; Verwey, 1948; Agasyan, 1980; Richens, 1997; Gregory, 2001). Freshly prepared aluminum hydroxide is a heavily hydrated gel material. On aging for long time intervals or by heating, it gives a well crystallized compound having the structure of AlOOH or

Al2O3.H2O (Steigman, 1982).

The formed Al (OH)3 precipitate was collected by centrifugation at the speed of 6000 rpm for 15 min and filtration of the supernatant solution ( ~ 36 ml) with a 0. 45 µm Millipore filter, to avoid and decrease contamination of the molybdate (VI) solutes with fine particles of the formed gelatinous Al(OH)3 precipitate together with cross- contaminant particulates. The 99Mo-molybdate (VI) supernatants before and after precipitation of Al (OH)3 and the formed Al (OH)3 precipitate were radiometerically analyzed by gamma-ray spectrometery and compared with the initial 99Mo-molybdate (VI) solute. The 99Mo- 173 molybdate (VI) loss, recovery yield and purification via retention onto the formed Al(OH)3 precipitate were assessed from the net area under the corresponding radionuclide characteristic energy peak in the initial and final supernatants under identical counting conditions.

3.5.1.1. Sorption / desorption of 99Mo-molybdate (VI) anions: 3.5.1.1.1. Sorption behavior: Fig. 3.41 ( curves a, b and c) shows typical gamma-ray spectra of 0.2 ml 99 of the initial Mo-molybdate (VI) solute before precipitation of Al (OH)3, the formed Al (OH)3 precipitate and 0.2 ml of the supernatant solution after precipitation and separation of the formed Al(OH)3 precipitate, respectively. Radiometeric analysis of the gamma-ray spectra of the supernatants before 99 and after precipitation of Al (OH)3 and comparing with the initial Mo- molybdate (VI) solute indicated that ~ 85 % of the initial 99Mo- molybdate (VI) anions remained in the supernatant. The total loss of 99Mo-molybdate (VI) anions from solution due to retention onto the surface of in-situ precipitated Al (OH)3 precipitate was found to be ~ 13.8 %.

3.5.1.1.2. Desorption behavior:

The separated Al (OH)3 precipitate was washed four times each with 8 ml

3.5 M NaNO3 solution of pH value 9.5, to investigate the recovery of retained 99Mo-molybdate (VI) anions. After centrifugation, the washings were filtrated by a 0.45 µm Millipore filter. Fig. 3.42 (curves a, b, c and d) shows gamma- ray spectra of the Al (OH)3 precipitate measured after the first, second, third and fourth washing processes for 100 s, respectively. It was found that even after washing of the formed precipitate with 32 ml 3.5 M NaNO3 solution of pH 9.5, the 99Mo-molybdate (VI) radioactivity level onto the surface of the matrix was still high and overlapping all the gamma-ray energy peaks of the radiocontaminants except for 1115 (65Zn), 1120 (46Sc), 1173, 1332 (60Co) and 1292 keV (59Fe), respectively. 174

(a)

) Tc ( 140.9 keV ) 99m

Mo, Mo ( 181.4keV ) ) 822.7 keV 99 99 ( Mo ( 739.3 keV ) Mo ( 777.7 keV ) Mo 99 99 99 Mo ( 366.5 keV ) keV ( 366.5 Mo 99 960 keV ( Mo ( 880keV ) Mo ( 920keV ) Mo 99 99 99

)

keV )

Tc ( 140.9 keV ) (b) 181.4 99m ( Mo, Mo 822.7 keV ( 99 99 ) Mo ( 739.3 keV ) Mo ( 777.7 keV ) Mo 99 99 99 keV Mo ( 366.5 keV ) keV ( 366.5 Mo 99 281 ( Tc 99m Mo ( 880keV ) Mo ( 920keV ) Mo ( 960 keV ) Co ( 1173 keV) Co ( 1332 keV) 99 99 99

60 60 Counts per channel, arbitrary units units arbitrary channel, per Counts

Tc ( 140.9 keV ) 99m (c) Mo, Mo ( 181.4keV ) 99 99 822.7 keV (

) Mo ( 366.5 keV ) keV ( 366.5 Mo Mo ( 739.3 keV ) Mo ( 777.7 keV ) Mo 99 99 99 99 960 keV ( Mo ( 880keV ) Mo ( 920keV ) Mo 99 99 99

Gamma-ray energy, keV 99 Fig. 3.41. Gamma-ray spectra of (a) 0.2 ml of the initial Mo-molybdate(VI) solute before precipitation of Al (OH)3, (b) the Al (OH)3 precipitate formed at pH 9.5 and (c) 0.2 ml of the final supernatant measured after cooling period of 8 days for 100 s.

175

(a) Tc ( 140.9 keV ) 99m

Mo, Mo ( 181.4keV ) 99 99 Mo ( 739.3 keV ) Mo ( 777.7 keV ) Sc ( 1120 keV ) 99 99 46 Mo ( 366.5 keV ) keV ( 366.5 Mo 99 Tc ( 281 keV ) 99m Co ( 1172,9 keV ) keV ( 1172,9 Co Fe ( 1292 keV ) Co ( 1332,2keV ) Mo ( 822.7 keV ) Mo ( 880keV ) Mo ( 920 keV ) Mo ( 960 keV ) 60 59 60

99 99 99 99 Zn ( 1115.5 keV ) Co ( 1172,9 keV )

65 60

(b)

Tc ( 140.9 keV ) Sc ( 1120 keV ) 99m 46 Mo, Mo ( 181.4keV ) Mo ( 739.3 keV ) Mo ( 777.7 keV ) 99 99 Mo ( 366.5 keV ) keV ( 366.5 Mo 99 99 99 units y Fe ( 1292 keV ) Co ( 1332,2keV ) Mo ( 822.7 keV ) Mo ( 880keV ) Mo ( 920keV ) Mo ( 960 keV ) Zn ( 1115.5 keV ) Co ( 1172,9 keV ) 59 60 99 99 99 99

65 60 arbitrar

(c) Tc ( 140.9 keV ) 99m Sc ( 1120 keV ) er channel 46 p Mo, Mo ( 181.4keV ) 99 99 Mo ( 739.3 keV ) Mo ( 777.7 keV ) 99 99 Mo ( 366.5 keV ) keV ( 366.5 Mo 99 Counts Mo ( 822.7 keV ) Mo ( 880keV ) Mo ( 920keV ) Mo ( 960 keV ) Zn ( 1115.5 keV ) Co ( 1172,9 keV ) Fe ( 1292 keV ) Co ( 1332,2keV ) 99 99 99 99

65 60 59 60

(d) Tc ( 140.9 keV ) Sc ( 1120 keV ) 46 99m Mo, Mo ( 181.4keV ) 99 99 Mo ( 366.5 keV ) keV ( 366.5 Mo 99 Fe ( 1292 keV ) Co ( 1332,2keV ) 59 60 Mo ( 739.3 keV ) Mo ( 777.7 keV ) Mo ( 880keV ) Mo ( 920keV ) Zn ( 1115.5 keV ) Co ( 1172,9 keV ) 99 99 99 99 65 60

Gamma-ray energy, keV

Fig. 3.42 .Gamma-ray spectra of the Al(OH)3 matrix precipitated at pH 9.5 measured st nd rd th after the (a) 1 , (b) 2 (c) 3 and (d) 4 washing process each with 8 ml 3.5 M NaNO3 solution of pH 9.5 for 100 s.

176 Fig. 3.43 (curves a, b, c and d) shows the corresponding gamma-ray spectra of 0.2 ml of the first, second, third and fourth washing filtrates, respectively. Radiometeric analysis of Figs. 3.41 ( curve b), 3.42 and 3.43 indicated that ~ 6.6, 3.2, 2.6 and 1.4 % 99Mo-molybdate (VI) anions were recovered from the Al (OH)3 precipitate into the first, second, third and fourth washing filtrates, respectively, with total recovery yield of ~ 13.8 % 99 99 Mo-molybdate from the Al (OH)3 precipitate. The total recovery of Mo- molybdate (VI) anions after washing of the formed precipitate of Fe(III) minerals and Al (OH)3 is ~ 98.8 % of its initial value with a loss of 1.2 % . By subtraction the 99Mo loss onto the formed Fe (III) mineral (0.97 %) from the total loss of 1.2 % 99Mo-molybdate (VI), the strongly retained 99 Mo-molybdate (VI) anions onto the Al(OH)3 precipitate was found to be ~ 0.23 %. Fig. 3.44 ( curves a, b, c and d ) shows gamma-ray spectra of 1.0 ml of the first, second, third and fourth washing filtrates measured after a cooling period of three months for 200 s. It is observed that only the radionuclides of 134Cs and 60Co were released from the formed precipitate into the first, second, and third washing filtrates.

3.5.1.1.3. 99Mo-molybdate (VI) uptake and mechanism:

After precipitation of the Al (OH)3 matrix at pH value of 9.5, ~ 85 % of the initial 99Mo-molybdate (VI) anions remained in the supernatant and ~ 13.8 % was recovered by washing the Al (OH)3 matrix 4 times each with 8 ml 3.5 M

NaNO3 solution of pH value 9.5. The remaining 0.23 % was strongly retained onto the surface of the formed Al (OH)3 precipitate. The uptake of 99Mo-molybdate (VI) anions onto surface of the formed

Al(OH)3 matrix are strongly affected by the pH value of solution (El- Absy et al, 1997 and 2011-a). This is due to changes in the chemical structure and surface electrical charge of the formed Al(OH)3 precipitate as well as the degree of condensation and charge of the predominating 99Mo-molybdate (VI) anions in solution (Scadden and Ballon, 1960; Aveston et al, 1964; Arino 177

(a)

Tc ( 140.9 keV )

99m Mo, Mo ( 181.4keV ) 99 99 Mo ( 739.3 keV ) Mo ( 777.7 keV ) Mo ( 366.5 keV ) keV ( 366.5 Mo 99 99 99 Mo ( 880 keV ) Mo ( 920 keV ) 99 99

(b)

Tc ( 140.9 keV ) 99m units Mo, Mo ( 181.4keV ) 99 99 y Mo ( 739.3 keV ) Mo ( 777.7 keV ) 99 99 Mo ( 366.5 keV ) keV ( 366.5 Mo Mo ( 880 keV ) Mo ( 920 keV ) arbitrar 99 , 99 99

er channel p (c)

Tc ( 140.9 keV ) 99m Counts Mo, Mo ( 181.4keV ) 99 99 Mo ( 739.3 keV ) Mo ( 777.7 keV ) 99 99

(d)

Tc ( 140.9 keV ) 99m Mo, Mo ( 181.4keV ) 99 99 Mo ( 739.3 keV ) Mo ( 777.7 keV ) 99 99

Gamma-ray energy, keV

Fig . 3.43.Gamma-ray spectra of 0.2 ml of the (a)1st, (b) 2nd,(c) 3rd and (d) 4th washing filtrates of the Al (OH)3 matrix precipitated at pH 9.5 measured for100 s.

178 (a)

Cs ( 604 keV ) 604 keV ) Cs ( Cs ( 795.5 keV ) keV 795.5 Cs ( 134 Co ( 1173 keV) Co ( 1332 keV) 134

60 60

(b)

)

eV k 795.5

(

Cs ( 604 keV ) Cs keV ( 604 Cs Co ( 1173 keV) Co ( 1332 keV)

134 134 60 60

(c)

Co ( 1173 keV) Co ( 1332 keV) 60 60 Counts per channel, arbitrary units units arbitrary channel, Counts per

(d)

Gamma-ray energy, keV Fig 3.44. Gamma- ray spectra of 1.0 ml of the ( a) 1st, ( b ) 2nd, (c) 3rd and (d) 4th washing filtrates of the Al (OH)3 matrix precipitated at pH 9.5 measured after a cooling period of three months for 200 s.

179 and Kramer, 1975; Mitchell, 1990; Carvatho and Abrao, 1997 Greenwood and Earnshw, 1998; Mitchell, 1999; Mostafa, 2006; El- Absy et al., 2011-b). In solutions of excess OH- ions (i.e, at pH value 9.5), in-situ precipitated particles of Al (OH)3 have an IEP of pH 8.6 (Arino and

Kramer, 1975; El-Absy 2005). Negatively charged Al(OH)3 particles possess cation-exchange reactions and attract cations from solution. This attraction will be followed by fast Van der Walls electrostatic neutralization with negatively charged anions and coagulation via physical attachment in the constant or monoelectric layer as the positive counter ions. Fast coagulation and precipitation process of the Al(OH)3 matrix is satisfied by the sequential mechanisms: (i) Cationic adsorption of e.g, Na+ cations from solution onto the negative surface of the particles and /or crystals of Al (OH)3 precipitates, 2- (ii) Attachment of the negative molybdate (VI) MoO4 anions by Van der Walls forces with no serious changes in the sorbent surface structure as verified by IR spectra [El-Absy, et al., (2011-b)]. Growth of the particles enhances hiding of the adsorbed molybdate (VI) anions onto the inter particles of the formed precipitate. This explains the unrecovery of ~ 0.23 % 99Mo-molybdate (VI) anions, appearing as strongly retained Mo (VI) anions onto the formed Al (OH)3 precipitate (Agasyan, 1980; Clifford, et al 1999; Johnstone, et al 2001; Nesmeyanov, 1974 and 1984; Srivastava and Jain, 1989; Mostafa 2002; Vogel, 1995). Molecular adsorption is generally not important if the precipitated particles size is large, because large particles have very small surface area. (iii) Inclusion or mechanical entrapment of the sodium molybdate (VI) solute surrounding the growing Al(OH)3 particles. Typically, this is only significant for highly hydrated well ordered crystals. Mechanical entrapment mechanism gives reasons for the successive recovery of ~ 6.6,

180 3.2, 2.6 and 1.4 % molybdate (VI) anions into the washing filtrates of 4 x 8 ml 3.5 M NaNO3 solution of pH value 9.5. Arino and Kramer (1975) reported that the adsorption capacity of molybdenum (VI) onto alumina columns was ~ 20 mg Mo/g of dry alumina in the range of pH values from 1 to 4.8 and ~ 2 mg Mo/g of dry alumina at pH values of 5- 6.2. At higher pH values the capacity was decreased to much smaller values due to formation of normal molybdate (VI) anions of higher charge value per molybdenum atoms and expected changes of the 99 surface electric charge of the Al (OH)3 matrix. The loss of ~ 0.23 % Mo by incorporation of the molybdate (VI) anions onto the inner surface of the growing particulates of in-situ precipitated Al(OH)3 at pH 9.5 is equivalent to ~ 1.35 mg Mo / g Al2O3. This value is approximately equal to that in the pH rang from 5 to 6.2 of Arino and Kramer (1975). On the other hand, in- situ precipitation of Al (OH)3 at pH value of 9.5 resulted in highly 2 developed surface area of colloidal Al (OH)3 particles (~ 288 m /g) responsible for further elutable 13.8 % 99Mo-molybdate (VI) anions. The obtained adsorption capacity of Mo (VI) anions is equal to ~ 80.9 mg

Mo/g Al2O3. The total adsorption capacity of Mo ( VI) onto the formed Al

(OH)3 precipitate is in the order of ~ 82.25 mg Mo / g Al2O3 which is 41 times higher than that of Arino and Kramer (1975). The relative loss of 99Mo (VI) will be much small on purification of high amounts of activation molybdenum-99 via in-situ precipitation of Al(OH)3 at pH 9.5 for large scale production of 99Mo / 99mTc gel generators of the chromatographic column elution mode. Increasing the Mo : Al ratios (w/w) will not affect seriously neither the amount of Mo (VI) loss nor the 99 purification efficiency of in-situ precipitated Al(OH)3 from the Mo- molybdate solutes. This is because the radiocontaminants are present in trace concentrations, except for Fe.

181 3.5.1.2. Purification assessment: Figs. 3.45, 3.46 and 3.47 ( curves a, b and c ) show gamma-ray spectra of the initial 99Mo-molybdate (VI) supernatant before precipitation of the Al(OH)3 matrix at pH 9.5, the in-situ precipitated

Al(OH)3 precipitate after washing with 4 × 8 ml 3.5 M NaNO3 solution of pH 9.5 and the supernatant solution after separation of the Al(OH)3 matrix measured after different cooling time periods ( and for different detection rates) namely: one month (100 s), two months (200 s) and three months (2000 s), respectively. Fig. 3.45 (curves a, b and c) shows that 10 half- life decay periods were not sufficient for complete decay of the 99Mo-molybdate radioactivity and clear identification of the corresponding contaminant radionuclides. As 134Cs radioinuclide was completely washed from the Al (OH)3 precipitate (Fig. 3.44 a and b), antimony-124 radionuclide was then detected and identified at the gamma-ray energy peak of 602 keV. Complete purification of the 99Mo- molybdate (VI) solute from the radiocontaminants of 95Zr, 95Nb, 46Sc, 59Fe, 65Zn, 181Hf and 124Sb was achieved together with 98 % 60Co and 95 % 51Cr eliminations. The predate elimination data are not sufficient for qualitative and / or quantitative analysis, due to the presence of 99Mo gamma-ray energy peaks (Fig. 3.45). On the other hand, Figs. 3.46 and 3.47 (curves a, b and c) verify that complete purification from the radionuclides of 95Zr, 95Nb, (181, 175) Hf, 59Fe, 65Zn, 46Sc and 124Sb was achieved. Purification values of about ~ 18 % 60Co and 60 % 51Cr from the previously remained 20 % 60Co and 65 % 51Cr due to precipitation of 60 Fe(III) minerals were achieved. After Al (OH)3 precipitation, ~ 2 % Co and 5 % 51Cr radionuclides were left in the 99Mo-molybdate (VI) supernatant.

182

( a )

Tc ( 140.6 keV)

99m Cs ( 795.7 keV ) Mo ( 739.4 keV) Mo ( 777.9 keV) 99 99 134 Mo, Mo ( 181.1 keV) Sc ( 1120 keV ) 99 99 46 Mo ( 366.3 keV) Cr (320 keV )

51 99 )

( )

keV ) 2 48 ( 281 keV Hf ( Cs ( 604. keV keV 604. Cs ( 920 keV ( Co (1333 keV ) Fe ( 1282 keV ) 181 Tc Zn (1115.3 keV ) Fe ( 1099 keV ) Co (117.4 keV ) 134 60 59 59 65 60 99m Mo ( 880 keV) Mo Sc ( 889.3 keV ) 99 46 99 units y

)

arbitrar ( (b) ,

) ) 181.2 keV ( keV ) Hf ( 133.2 keV ) Mo ( 140.6 keV) Mo 3.1 . 181 99 99 920 keV ( 366 keV 117 ( ( Hf (482 keV ) Mo ( 880 keV) Mo Sc ( 889.3 keV ) Hf ( 343.5 keV ) Co (1333.3 keV ) Zn (1115.6 keV ) Fe ( 1099 keV ) Co Fe ( 1282.1 keV ) Mo Cr (320 keV ) Sb ( 602.5 keV ) 181 99 46 99 60 59 65 46Sc ( 1120.3 keV ) 60 59

Zr (724 keV ) Mo ( 739.7 keV) Zr (756 keV ) Mo ( 777.9 keV) 51 175 99 124 95 99 95 99 er channel p

Counts (c)

)

Mo ( 140.6 keV) Mo ( 181.1 keV) keV 99 99 . 795 ( Cs Mo ( 739.4 keV) Mo ( 777.9 keV) Mo ( 366.4 keV ) 99 99 134 Cr ( 320.2 keV ) 51 99 Mo ( 920.2 keV) Mo (880 keV) Cs ( 604.66 keV keV Cs ( 604.66 99 99 134 Co (117.3.1 keV ) Co (1333.3 keV ) 60 60

Gamma-ray energy, keV 99 Fig. 3.45. Gamma-ray spectra of (a) 1.0 ml of the initial Mo-molybdate (VI) supernatant, (b) the formed Al(OH)3 matrix washed with 32 ml 3.5 M NaNO3 of pH 9.5 and (c ) 1.0 ml of the supernatant solution measured after a cooling period of one month for100 s.

183 ( a )

) 604keV ( Hf ( 133.2 keV ) keV 133.2 Hf ( Zn (1115.6 keV ) Fe ( 1099 keV ) Co (117.3.2 keV ) Co (1333.3 keV ) Cs ( 795.62 keV ) ) keV 795.62 Cs ( Cs ( 562 keV ) Cs ( 568keV ) Cs 59 65 46Sc ( 1120.3 keV ) 60 60 Hf ( 481.9 keV ) keV 481.9 Hf ( 181 Hf3442 ( keV ) Sc ( 889.1 keV ) keV 889.1 Sc ( 134 134 134 134 Cr ( 319.9 keV ) 181 46 51 178

units ( b ) ) keV ) y

3.1 . 117 ( Hf ( 133.1 keV ) keV 133.1 Hf ( 765.4 keV keV 765.4 Zn (1115.4 keV ) Fe ( 1099.2 keV ) Co ( arbitrar Fe ( 1291.6 keV ) Co (1333.3 keV ) 181 ) keV 481.9 Hf ( 46Sc ( 1120.3 keV ) 59 65 60 , 59 60 Sb ( 602.2 keV ) keV 602.2 Sb ( Sc ( 889 keV Sc ) keV ( 889 181 Hf3442 ( keV ) Nb Zr (724 keV ) Zr (724 keV ) Cr ( 319.9 keV ) 124 46 51 178 95 95 95 Sb ( 1692Sb ( keV ) 124 er channel p

Counts ` ( c )

Cs ( 795.41 keV ) keV Cs ( 795.41 134 Co (117.3.15 keV ) Cs ( 562.4 keV ) Cs ( 568.9 keV ) Cs ( 604.4 keV ) Co (1333..54 keV ) 60 134 134 134 60

Gamma-ray energy, keV

99 Fig. 3.46. Gamma-ray spectra of (a) 1.0 ml of the initial Mo-molybdate (VI) supernatants, (b) the formed Al(OH)3 matrix washed with 32 ml 3.5 M NaNO3 of pH 9.5 and (c) 1.0 ml of the supernatant solution measured after a cooling period of two months for 200 s.

184

( a ) Cs ( 801. keV ) Cs ( 568. keV ) 134 Nb ( 765. keV ) Nb ( 765. 134

Cs ( 563.keV ) Cs ( 604. keV ) Sc ( 1120. keV ) Cs ( 795. keV ) Zn ( 1115. keV ) Fe ( 1099. keV ) Co ( 1173. keV ) Cs ( 1365. keV ) Zr ( 724, keV ) Zr ( 756.keV ) Sc ( 889 keV ) Co ( 1332. ke ) Fe ( 1291. keV ) 59 65 46 60 134 134 95 134 46 95 134 59 60 Hf ( 482 keV ) Hf keV ( 482 Hf ( 133.11 keV Hf ( 345keV ) 181 Cr ( 319.9 keV ) 181 51 178 Sb ( 1691 keV ) 124 units y

)

arbitrar , Hf( 345. KEv ) Hf( Nb ( 765. keV Nb ( 765. ( b)

95 181

Sc ( 1120. keV ) Zn ( 1115. keV ) Fe ( 1099. keV ) Co ( 1173. keV )

59 65 46 60 Hf( 482 keV ) Co ( 1332keV ) Fe ( 1291. keV ) 59 60 181 Hf ( 133. keV ) Fe ( 192. keV ) Sc ( 889 keV ) 181 59 46 Zr ( 724, keV ) Zr ( 756 keV ) 95 95 Hf ( 343. keV ) er channel Cr ( 320 keV) Sb ( 602. keV ) p 51 175 124 Sb ( 1691.4 keV ) 124 Counts

( c )

Cs ( 563. keV ) Cs ( 568. keV ) Cs ( 604. keV ) Cs ( 795. keV ) Cs ( 1365. keV ) Co ( 1173. keV ) 134 134 134 Co ( 1332. 6ke ) 134 60 134 60 Cr ( 320 keV) Cr keV) ( 320 51

Gamma-ray energy, keV Fig. 3.47. Gamma-ray spectra of (a)1.2 ml of the initial 99Mo-molybdate (VI) supernatant, (b) the formed

Al(OH)3 matrix washed with 32 ml 3.5 M NaNO3 of pH 9.5 and (c) 1.2 ml of the supernatant solution measured after a cooling period of three months for 2000 s.

185 3.5.1.2.1 Iron-59: Colloidal fine particles of 59Fe radionuclide (~ 32 % 59Fe) penetrated the 45 µm Millipore filter in the form of the Raman identified hematite, ferrihydrite and / or siderite minerals into the 99Mo-molybdate (VI) solute after precipitation of the dissolved 1.37 mg Fe in 30 ml 4 M NaOH solution with the addition of 0.5 ml H2O2. This is due to high dispersion of the formed fine colloidal particles of Fe(III) minerals from ~ 0.721 × 10-3 M Fe in 30.5 ml 4 M NaOH solution. The highly dispersed fine particles of 59Fe- iron (III) mineral may be co-precipitated and scavenged with the macro- 59 component of Al in the form of mixed crystals of Al(OH)3. Fe(OH)3; 59 59 AlOOH. FeOOH; Al2O3.nH2O. Fe2O3.nH2O (Nesmeyanov, 1974; Agasyan, 1980; Johnstone et al., 1984 and 2001; Srivastava and Jain, 1989; Vogel, 1995 and 2001; Clifford et al., 1999; Mostafa 2002) with complete removal of the 59Fe labelled radiocontaminants from the 99Mo- molybdate (VI) solute.

3.5.1.2.2. Zinc-65: Zinc dissolves in concentrated alkali solutions to form soluble zincate 2- anion [Zn(OH)4] . On acidification, a white gelatinous precipitate of zinc hydroxide Zn(OH)2 is formed (Agasyan, 1980; Srivastava and Jain, 1989; Mostafa 2002; Vogel, 1995).

2- + [Zn(OH)4] + 2H Zn(OH)2↓ + 2H2O

The formed zinc hydroxide may be co-precipitated with the formed 65 Al(OH)3 precipitate at pH 9.5 leading to complete elimination of Zn 2- radionuclide from the molybdate (VI) solution and / or by [Zn(OH)4] adsorption onto the inner sphere by Van der Walls forces such the molybdate (VI) anions. Purification from Zn onto Al (OH)3 is in agreement

186 with Trainor et al., (2000). They suggested that Zn(II) forms predominantly inner-sphere surface complexes with Al(OH)3 whereas at higher sorption densities the mixed-metal complex Zn(II)-Al(III) hydroxide co-precipitates.

3.5.1.2.3. Antimony-124: Acidification of the 4 M NaOH solution containing soluble antimonite anions by concentrated nitric acid to pH value of 9.5 leads to form the oxide Sb2O5:

- + 2[Sb(OH)6] + 2H → Sb2O5 ↓ + 7H2O which may be completely co-precipitated with the formed gelatinous

Al(OH)3 precipitate (Agasyan, 1980; Srivastava, 1987; Vogel, 1995; Vogel, 2001; Mostafa 2002).

3.5.1.2.4. Chromium-51:

The elimination % of Cr(OH)3 by the formed Fe(OH)3 minerals was found to be ~ 35 % chromium-51 from the initial 99Mo-molybdate (VI) solute. The remaining ~ 65 % 51Cr may be in the form of soluble tetrahydroxochromate (III) anions soluble in 4 M NaOH solution. On acidification and / or boiling, the reaction is reversible and re-precipitates chromium (III) hydroxide Cr(OH)3 (Agasyan, 1980; Srivastava and Jain, 1989; Mostafa 2002; Vogel, 1995):

H+ - [Cr(OH)4] Cr(OH)3 ↓ + H2O OH-

It was found that, acidification with HNO3 acid to pH 9.5 enhanced ~ 60

% of the initial chromium-51 radionuclide to co-precipitate as Cr(OH)3

187 with the freshly formed Al(OH)3 precipitate. The remaining 5 % of the initially present chromium-51 radionuclide may be persisting elimination due to oxidation with H2O2 in NaOH solution to chromate and / or dichromate anions. The total purification from 51Cr after sequential precipitation of Fe(III) minerals and Al(OH)3 is ~ 95 % leaving about 5 % 51Cr chromate and / or dichromate anions in solution.

3.5.1.2.5. Cobalt- 60: 60 Due to oxidation of Co (II) to Co (III) by H2O2, about 20 % Co radionuclide were not retained onto the formed Fe (III) minerals from 4 M NaOH solution and penetrated the 45 µm Millipore filter in the form of very fine Co(III) colloidal particles (Vogel, 2001). On acidification by nitric acid, removal of 60Co radionuclides may be due to co-precipitation of the formed Co(OH)3 precipitate with Al(OH)3 (Agasyan, 1980; Srivastava and Jain, 1989; Vogel, 1995; Vogel, 2001) and / or adsorption of Co3+ cations onto the negatively charged precipitate of

Al(OH)3 from weakly alkaline solutions (pH 9.5), leaving about 2 % of the total initial 60Co in the 99Mo-molybdate (VI) solute.

3.5.1.2.6. Scandium-46: Data analysis showed that complete elimination of the remaining 46Sc was achieved, i.e, ~ 100 % 46Sc elimination, via in-situ precipitation of 99 Al(OH)3 from the Mo-molybdate (VI) solute at pH value 9.5. About 50 46 % of Sc was previously co-precipitated with the formed Fe(III) 46 minerals as Sc(OH)3 or ScOOH and the remaining 50 % Sc was 3- dissolved in 4 M NaOH solution forming [Sc(OH)6] anions. Addition of nitric acid to the reaction mixture solution, the formation of soluble 3- [Sc(OH)6] may be reversed and Sc(OH)3 and ScOOH precipitate from

188 the molybdate (VI) solute at pH 9.5 to be eliminated via co-precipitation forming anomalous mixed oxides and / or hydrous oxide with the formed

Al(OH)3 precipitates (Agasyan, 1980; Srivastava and Jain, 1989; Vogel, 1995; Vogel, 2001; Greenwood and Earnshw, 1998).

3.5.1.2.7. Zirconium-95 and hafmium-181 and 175: Zirconium and hafnium are similar in most of their chemical properties. Addition of concentrated nitric acid to the 99Mo-molybdate anions in 4 M, NaOH solution up to pH value 9.5, the soluble sodium zirconate and hafinate may be precipitated as white gelatinous precipitates of zirconium and hafnium hydroxides. Zirconium compounds in aqueous solutions are characterized by high degree of hydrolysis. The following equilibria are expected from aqueous solutions:

4+ 3+ + Zr + H2O ↔ Zr (OH) + H 3+ 2+ + Zr (OH) + H2O ↔ Zr (OH)2 + H 2+ + + Zr (OH)2 + H2O ↔ Zr (OH)3 + H + + Zr (OH)3 + H2O ↔ Zr (OH)4 + H

Tracers of 95Zr (IV) and 181,175Hf (IV) may be completely precipitated and scavenged with the bulky mass of the formed gelatinous Al(OH)3 precipitate and / or by hydrolytic sorption reactions leading to ~ 100 % 95Zr and 181,175Hf radionuclides eliminations from the 99Mo-molybdate (VI) solute.

3.5.1.2.8. Niobium-95: Niobium-95 radionuclide, in contrary to 92mNb, was partially eliminated and detected in the supernatant solution after separation of the 189 formed Fe (III) minerals, as a decay product of 95Zr remained completely in the Mo(VI) solution. Niobium forms niobate anions in concentrated solution of NaOH. Addition of nitric acid to the solution niobate anions precipitate completely above pH 7 forming the hydrated oxide of

Nb2O5.nH2O. Table (3.15) compiles the elimination % of activation cross-contaminant radionuclides from the 99Mo-molybdate (VI) solute by sequential in-situ precipitation of 1.37 mg Fe as Fe(III) minerals with 0.5 ml H2O2 from 30 ml 4 M NaOH solution and of 0.6 g Al as Al(OH)3 precipitate with the addition of HNO3 acid up to pH 9.5. It shows that sequential purification of the 99Mo-molybdate (VI) supernatant via in-situ precipitation of Fe(III) iron from ~ 4 M NaOH solution, then addition of concentrated HNO3 acid up to pH value of 9.5 to precipitate the corresponding Al(OH)3 matrix was highly efficient for removal of the cross-contaminant radionuclides 60Co, 51Cr, 46Sc, 65Zn, 95Zr, 95Nb, 175,181Hf 59Fe and 124Sb. 134Cs radionuclide showed no retention affinity towards the in-situ precipitated Al(OH)3 matrix, due to reversible competition with the macro-component of Na+ cations. The repulsive forces created between the negative charges onto the formed Fe (III) minerals and the alumina surfaces and the normal molybdate (VI) anions resulted in a total of ~ 1.2 % 99Mo-molybdate (VI) loss from solution.

3.5.2. In-situ precipitation of Al(OH)3 matrix at pH 5: As above mentioned, the 99Mo-molybdate (VI) supernatant which remained after in-situ precipitation of Fe(III) minerals contained 0.6 g Al foil soluble in 30.5 ml 4 M NaOH solution in the form of NaAlO2.

Precipitation of the aluminate anion in the form of the Al (OH)3 matrix was conducted by acidification of the initial 99Mo-molybdate (VI) supernatant with addition of concentrated HNO3 acid up to pH value 5, centrifugation

190 and separation of the final 99Mo-molybdte (VI) supernatant by filtration with 45 µm Millipore filter. The separated solid and aqueous solutions were subjected to gamma-ray spectroscopic analysis.

99 Table (3.15): Mo-molybdate (VI) purification via successive in-situ precipitations of 1.37 mg Fe from 0.6 g Al dissolved in 30 ml 4 M NaOH by oxidation with 0.5 ml H2O2 and HNO3

acid neutralization to pH 9.5, respectively.

Radionuclide Elimination % Fe(III) minerals Al(OH)3, pH 9.5 Total % 141Ce 100 0.00 100 140La 100 0.00 100 152Eu 100 0.00 100 54Mn 100 0.00 100 92mNb 100 0.00 100 95Nb 97 3 100 60Co 80 18 98 59Fe 70 30 100 46Sc 50 50 100 51Cr 35 60 95 99Mo 0.97 0.23 1.2 124Sb 0.00 99.9 99.9 65Zn 0.00 100 100 95Zr 0.00 100 100 175,181Hf 0.00 100 100 134Cs 0.00 0.00 0.00

3.5.2.1. Adsorption / desorption of 99Mo-molybdate (VI) anions: 3.5.2.1.1. Adsorption behavior: Fig. 3.48 ( curves a, b and c) shows gamma- ray spectra of 0.2 ml of the 99 initial Mo-molybdate(VI) supernatant before precipitation of the Al (OH)3

matrix, the formed Al (OH)3 matrix and 0.2 ml of the final supernatant after

precipitation of Al (OH)3 at pH 5. Analysis of the energy peaks net area indicated that only ~ 20.3 % 99Mo-molybdate (VI) radionuclide remained in the final supernatant. The observed high retention value of ~ 79.7 % of the initial 99Mo-molybdate (VI) supernatant at pH 5 may be due to both anion- exchange reaction between the condensed heptamolybdate (VI) anions 6- - [Mo7O24] from the solution and OH anions onto the surface of the formed

Al (OH)3 matrix with an isoelectric point (IEP) of pH 8.6 and / or mechanical

191

Tc ( 140.9 keV ) (a) 99m

)

Mo, Mo ( 181. 2 keV ) 99 99 823 keV (

Mo ( 739.9 keV ) Mo ( 777.2 keV ) Mo 99 99 99

) Mo ( 366.7 keV ) keV ( 366.7 Mo 99 960 keV ( units Mo ( 880keV ) Mo ( 920 keV ) Mo 99 99 99 Co ( 1172,9 keV ) Co ( 1332keV ) y

60 60

arbitrar ,

) Tc ( 140.ke)

99m (b)

823 keV Mo, Mo ( 181. 2 keV ) (

) 99 99 Mo ( 739.9 keV ) Mo ( 777.2 keV ) Mo 99 99 99 er channel p 960 keV ( Tc( 281 keV ) Mo ( 366.7 keV ) keV ( 366.7 Mo 99m Mo ( 880keV ) Mo ( 920 keV ) Mo 99 99 99 99 Co ( 1332,2keV ) Co ( 1172,9 keV ) keV ( 1172,9 Co 60 60 Counts

Tc ( 140.ke) (c) 99m Mo, Mo ( 181. 2 keV ) 99 99 Mo ( 739.9 keV ) Mo ( 777.2 keV ) 99 99 Mo ( 366.7 keV ) keV ( 366.7 Mo 99

Gamma-ray energy, keV

Fig. 3.48.Gamma-ray spectra of ( a ) 0.2 ml of the initial 99Mo-molybdate (VI) supernatant, (b) the

formed Al (OH)3 matrix at pH 5 and (c) 0.2 ml of the remaining supernatant measured after a cooling period of 8 days for 100 s.

192 inclusion of molecular sodium 99Mo-molybdate (VI) via fast coagulation of the formed Al(OH)3 precipitate particles. Fig. 3.48 (curve a, b and c) shows 60 that Co (Eγ = 1172.9 and 1332 keV) radionuclide was retained and detected onto the surface of the formed Al (OH)3 matrix together with the ~ 79.7 % 99Mo radionuclide, while the final supernatant contained almost pure 99Mo (VI) radionuclide.

3.5.2.1.2. Desorption behavior: To investigate recovery of the retained 99Mo-molybdate (VI) anions, the separated precipitates of Al(OH)3 formed at pH 5 were individually washed with 32 ml 3.5 M NaNO3 solution of pH values 5 and 9.5. The washing filtrates were radiometericaly analyzed and compared with the initial 99Mo- molybdate (VI) supernatants.

The separated precipitate of Al(OH)3 was washed 4 times each with 8 ml

3.5 M NaNO3 solution of pH 5 and centrifuged. The washing solutions were filtrated using a 0.45 µm Millipore filter. Comparing the net area under the energy peak ~ 740 keV for the individual washing filtrates and the initial supernatant, the recovery yields were about 5.4 % 99Mo in the first washing filtrate, 2.9 % 99Mo in the second washing filtrate, 1.6 % 99Mo in the third washing filtrate and nearly nil 99Mo radionuclide recovery in the fourth washing filtrate. The total molybdenum-99 recovery yield is ~ 30.2 % 99Mo with a loss of ~ 69.8 % 99Mo-molybdate (VI) anions retained onto the formed

Al(OH)3 matrix via anion-exchange reactions between the heptamolybdate (VI) anions from solution and OH- anions onto the surface of the formed 99 Al(OH)3 matrix. The recovered value of ~ 9.9 % Mo-molybdate (VI) anions by washing with 32 ml 3.5M NaNO3 solution of pH 5 may be retained by surface inclusion (mechanical entrapment) between the large coagulated particles of the Al(OH)3 matrix with consequent partition recovery between the solid matrix and the washing nitrate solution. The strongly retained ~ 69.8 99 % Mo-molybdate (VI) anions may be adsorbed onto the formed Al (OH)3

193 matrix with an adsorption capacity of ~ 407 mg Mo / g Al2O3. This value is very much higher than the values obtained by Arino and Kramer (1975). This is due to sorption reaction onto in-situ precipitated highly developed 2 surface area (of ~ 288-300 m /g) colloidal Al (OH)3 particles of heptamolybdate (VI) anions compared to sorption reactions onto crystalline pre-prepared Al2O3 sorbents. The total sorption capacity is ~ 460 mg Mo / g dry Al2O3.

In an alternative investigation, the precipitated Al (OH)3 matrix was washed 4 times each by 8 ml 3.5 M NaNO3 solution of pH 9.5, centrifuged and filtrated using a 45 µm Millipore filter. Radiometeric analysis indicated 99 that ~ 15.49, 19.6 and 15.07 % Mo were recovered from the Al (OH)3 precipitate in the first, second and third washing filtrate, with only 1.03 % in the fourth washing filtrate. The total 99Mo recovery was found to be ~ 71.5 %. The remaining ~ 28.5 % 99Mo radionuclide may be strongly retained as 6- [Mo7O24] anions adsorbed onto internal surfaces of the positively charged coagulated Al(OH)3 particles formed at pH 5.

3.5.2.1.3. 99Mo-molybdate uptake and mechanism:

Assuming that the precipitation of Al(OH)3 matrices is reproducible, the 99 recovered ~ 51.2 % Mo-molybdate (VI) anions, by washing the Al(OH)3 matrix with 32 ml 3.5 M NaNO3 solution of pH 9.5, can be divided into ~ 9.9 % 99Mo retained via mechanical inclusion of heptamolybdate anions between the coagulated large Al(OH)3 particles with consequent steric elution 2- hinderance by washing with NaNO3 solution of pH 9.5 in the form of MoO4 anions and ~ 41.3 % 99Mo-paramolybdate (VI) anions retained by anion- exchange reactions onto the external surfaces surrounded by the aqueous eluent. Washing by 3.5 M NaNO3 solution of pH 9.5 converts the ion- exchange properties of the formed Al (OH)3 precipitate with IEP of pH 8.6 from anion-exchanger to cation-excghanger. The correspondingly retained molybdate (VI) anions dissociate from heptamolybdate (VI) anions of lower

194 6- 2- negative charge density [Mo7O24] to normal molybdate anions [MoO4] of higher negative charge density with consequent release of the additionally 2- produced negative charges as MoO4 anions from the surface of the Al(OH)3 matrix into the washing filtrates. Actually, the strongly retained ~ 28.5 % 99 Mo-molybdate onto the Al (OH)3 matrix after washing by 32 ml 3.5 M

NaNO3 of pH 5, equivalent to adsorption capacity of ~ 167 mg Mo / g Al2O3. Also, the obtained capacity is 8 times higher than the value obtained by

(Arino and Kramer 1975). It is due to in-situ formation of colloidal Al (OH)3

fine particles with rapid coagulation to Al (OH)3 precipitate. Table (3.16) compiles the retention % of 99Mo-molybdate (VI) anions onto the formed Al

(OH)3 precipitate at pH 5 before and after washing with 4x8 ml 3.5 M NaNO3 solutions of pH values 5 and 9.5.

99 Table (3.16). Retention % of Mo-molybdate (VI) anions onto Al(OH)3 in-situ precipitated at

pH 5 before and after washing with 4x8 ml 3.5 M NaNO3 solutions of pH values 5 and 9.5.

Washing Retained % of 99Mo-molybdate (VI) Retained / eluted Mo (VI) solution pH Before After washing species value washing First Second Third Fourth pH 5 79.7 74.3 71.4 69.8 69.8 Paramolybdate / paramolybdate pH 9.5 79.7 64.21 44.61 29.54 28.51 Paramolybdate / normal molybdate

The corresponding recovery yield of 99Mo-molybdate (VI) anions from the

Al(OH)3 precipitates formed at pH values of 5 and 9.5 after washing with 4x8

ml 3.5 M NaNO3 solutions of pH 5 and / or 9.5 are compiled in Table (3.17).

It is observed that highly dispersed Al(OH)3 precipitates (with IEP pH 8.6) in acidic solutions of pH 5 exhibited anion-exchange reactions with consequent very high adsorption capacity of the polymerized molybdate anions (i.e, heptamolybdate (VI) anions) forming gel matrix with the formed particles of

Al(OH)3 precipitate (El-Absy et al., 2011-b under publication).

195 Table (3.17): Recovery % of 99Mo-molybdate (VI) anions after successive washing of

the Al(OH)3 precipitates formed at pH values of 5 and 9.5 with 4×8 ml 3.5 M NaNO3 solutions of pH values 5 and /or 9.5.

Results 99Mo remained in the Total 99Mo recovery yield after successive washing , % supernatant, % First Second Third Fourth Experemental conditions Al (OH)3 precipitated at 85 91.6 94.8 97.4 98.8 pH 9.5, washed with 4x8

ml 3 .5 M NaNO3 solution of pH 9.5

Al(OH)3 precipitated at 20.3 25.7 28.6 30.2 30.2 pH 5, washed with4x8 ml

3 .5 M NaNO3 solution of pH 5

Al(OH)3 precipitated at 20.3 35.79 55.39 70.46 71.49 pH 5, washed with 4x8 ml

3 .5 M NaNO3 solution of pH 9.5

Recovery yields of the retained molybdate (VI) anions from the Al(OH)3 precipitates with 3.5 M NaNO3 solutions proceed in the following orders:

3.5 M NaNO3 solution of pH 9.5 >> 3.5 M NaNO3 solution of pH 5 and

Al (OH)3 precipitated at pH 9.5 >> Al (OH)3 precipitated at pH 5.

Figs. 3.49, 3.50, 3.51 and 3.52 show gamma-ray spectra of the first, second, third and fourth washing filtrates of Al(OH)3 precipitate at pH 5, measured after two cooling periods of 8 days and two months for 100 and 300 s, respectively. The obtained spectra are good illustration evidences of the 99 adsorption / desorption behaviors of Mo (VI) anions with 3.5 M NaNO3 solutions of pH values 5 and 9.5. The recovered 134Cs and 60Co radionuclides during the two washing processes indicates that they were enter- molecular retained with the molybdate (VI) solution between the large particles of the formed Al(OH)3 precipitates.

196

Tc(140 keV)

(a) Mo (140 keV), Mo (181 keV), 99m 99 99 Mo (366 keV) Mo (740 keV), Mo (787 keV), 99 99 99

Mo (880keV), Mo (920keV), 99 99

Tc(140 keV) (b) Mo (140 keV), Mo (181 keV), 99m 99 99 Mo (740 keV), Mo (787 keV), 99 99

) 181 keV ( Tc(140 keV) Mo (140 keV), Mo 99m 99 99 Counts per channel, arbitrary units

(d) Tc(140 keV) Mo (140 keV), Mo (181 keV), 99m

99 99

Gamma-ray energy, keV st nd rd th Fig. 3.49. Gamma-ray spectra of 1.0 ml of the 1 , 2 , 3 and 4 8 ml washing filtrates of Al(OH)3 precipitated at pH 5 with 3.5 M NaNO3 solution of pH 5 measured after cooling period of 8 days for 100 s.

197 (a) Tc(140 keV)

99m Mo (740 keV), Mo (787 keV), 99 99 Mo (140 keV), Mo (181 keV), 99 99

Tc(140 keV)

99m (b)

Mo (740 keV), Mo (787 keV), units Mo (366 keV) 99 99 99 y

Mo (140 keV), Mo (181 keV), 99 99 Mo (880keV), Mo (920keV), 99 99 arbitrar ,

Tc(140 keV) er channel 99m (c) p

Mo (140 keV), Mo (181 keV), Counts 99 99 Mo (366 keV) 99

Mo (740 keV), Mo (787 keV), Mo (880keV), Mo (920keV), 99 99 99 99

(d)

Tc(140 keV) 99m

Mo (140 keV), Mo (181 keV), 99 99 Mo (740 keV), 99

Gamma-ray energy, keV

Fig. 3.50. Gamma-ray spectra of 1.0 ml of the 1st , 2nd, 3rd and 4th 8 ml washing filtrates of Al(OH)3 precipitated at pH 5 with 3.5 M NaNO3 solution of pH 9.5 measured after cooling period of 8 days for 100 s.

198

(a) Cs (604 keV) Cs (7954 keV) 134

134

Co (1173 keV) Co (1332 keV) 60 60

(b)

Cs (604 keV) Cs (7954 keV 134 134

Co (1173 keV) Co (1332 keV)

60 60

(c)

Cs (604 keV) Cs (7954 keV 134 134

Co (1173 keV) Co (1332 keV) 60 60 Counts per channel, arbitrary units units arbitrary channel, Counts per

(d)

Gamma-ray energy, keV

st nd rd th Fig. 3.51. Gamma-ray spectra of 1.0 ml of the 1 , 2 , 3 and 4 8 ml washing filtrates of Al(OH)3 precipitated at pH 5 with 3.5 M NaNO3 solution of pH 5 measured after cooling period of 2 months for 300 s.

199

(a)

Cs (604 keV) Cs (7954 keV 134 134

Co (1173 keV) Co (1332 keV) 60 60 units y (b) Cs (604 keV) 134 Co (1173 keV)

arbitrar 60 , er channel p (c) Counts

(d)

Gamma-ray energy, keV

Fig. 3.52. Gamma-ray spectra of 1.0 ml of the 1st, 2nd, 3rd and 4th 8 ml washing filtrates of Al(OH)3 precipitated at pH 5 with 3.5 M NaNO3 solution of pH 9.5 measured after cooling period of 2 months for 300 s.

200 3.5.2.2. Purification assessment: Fig. 3.53 ( curves a, b and c) shows gamma-ray spectra of typical 99 Al(OH)3 matrices precipitated from the initial Mo-molybdate (VI) supernatant at pH 5 before and after washing with 32 ml 3.5 M NaNO3 solutions of pH values 5 and 9.5. The obtained spectra indicated high affinity of molybdenum (VI) anions to adsorb onto the formed positively charged Al(OH)3 particles via anion-exchange and / or molecular adsorption besides to incorporation of the molybdate (VI) solute between the layers of coagulated large particles of the Al(OH)3 precipitate from solution of pH 5. The higher recovery yield of molybdenum (VI) from the

Al(OH)3 precipitate washed with 3.5 M NaNO3 solution of pH 9.5 rather than with the solution of pH 5 can be predicted by charge neutralization of the positively charged alumina particles and its conversion into negatively charged particulates in 3.5 M NaNO3 solution of pH 9.5. The highly created repulsion forces between the negative charges of the total number of exchangeable sites fixed onto the surface of the Al (OH)3 sorbent and the retained molybdate (VI) anions dissociation products resulted in partial 2- releases of the dissociating normal molybdate anions MoO4 into the washing filtrates (Tables 3.16 and 3.17). Fig. 3.54 (curves a, b, c and d) shows gamma-ray spectra of 1.0 ml of the initial molybdate (VI) supernatant before precipitation of Al(OH)3, the

Al(OH)3 precipitates formed at pH 5 after washing with 32 ml 3.5 M 99 NaNO3 solutions of pH values 5 and pH 9.5 and 1.0 ml of the final Mo- molybdate (VI) supernatant measured after cooling period of three months for 300 s. It is observed that complete purification of the molybdate (VI) solute from 51Cr (as chromate and dichromate anions) and 60Co radiocontaminants was achieved either by precipitation and / or by anionic

201

Tc(140 keV)

99m

) Mo, Mo (181 keV)

99 99 ( a) k) 795 keV (

( Cs f Mo (739 keV) Mo (778 keV) Hf (344 keV) 134 99 99 Mo (366 keV) Cr ( 320 keV) Zn (1115 keV) Fe(1099 keV) Sc(1120 keV)

51 175 99 181 Fe(1292 keV) 59 65 46 60Co(1173keV) 59 60Co(1332keV) Mo (920 keV) Mo (960 keV) Sc( 889 keV) Cs ( 604 keV) Sb (602 keV) Hf (482keV) 46 99 99 124 134 181 Sb (1692 keV) 124

Tc(140 keV) Cs ( 795 keV) 99m Mo (739 keV) Mo (778 keV) 134 99 95Zr ( 756 keV) 99 Mo, Mo (181 keV) 99 99

) ( b) ) keV 960 keV ( Hf (344 keV) 734 Hf (482 keV) Fe(1292 keV) Mo (366 keV) Zn (1115 keV) Cr ( 320 keV) Fe(1099 keV) Sc(1120 keV) 75 ( 59 60Co(1332keV) 51 1 99 181 59 65 46 60Co(1173keV) Mo (920 keV) Mo Sc( 889 keV) Cs ( 604 keV) Sb (602 keV) Zr 46 99 99 124 134 95 Sb (1692 keV) 124

Counts per channel, arbitrary units Tc(140 keV) Cs ( 795 keV) Mo (739 keV) Mo (778 keV) 99m 134 99 95Zr ( 756 keV) 99

Mo, Mo (181 keV)

)

Hf (344 keV) Hf (482 keV) Mo (366 keV) Cr ( 320 keV) 75 51 99 181 1 960 keV ( Zr ( 734 keV 95 Zn (1115 keV) Fe(1099 keV) Sc(1120 keV) Mo (920 keV) Mo Sc( 889 keV) Cs ( 604 keV) Sb (602 keV)

59 65 46 60Co(1173keV) Fe(1292 keV) 46 99 99 124 134

59 60Co(1332keV) Sb (1692 keV) 124

Gamma-ray energy, keV

Fig. 3.53. Gamma-ray spectra of (a) typical Al(OH)3 matrices precipitated at pH 5 before washing, and after washing with 32 ml 3.5M NaNO3 solution of (b) pH 5 and (c) pH 9.5 for 300 s.

202

( a )

Cs ( 796 keV) Zr ( 7524keV) keV) ( 756 Zr Nb ( 765 keV) Nb keV) ( 765

95 95 95 134

) 604 keV ( Fe(1292 keV) Co (1332keV) 60 59 Hf9133 keV) (344 keV) Zn ( 1115keV) Fe(1099keV) Sc ( 1120keV) Co (1173keV) Cs ( 562 and 56keV) Sb ( 602 keV) Cs f Hf9133 keV) 59 65 46 60 181 H 134 124 134 Sc ( 889 keV) Sc keV) ( 889 Cr ( 320 keV) 181 51 175 46 Sb (1692 keV) 124

( b) units y Zn ( 1115keV) Fe(1099keV) Sc ( 1120keV) Co (1173keV) Hf9133 keV) 59 65 46 60 Sb ( 602 keV) Zr ( 7524keV) keV) ( 756 Zr Sc keV) ( 889 Nb ( 765 keV) Nb keV) ( 765 Fe(1292 keV) Co (1332keV) 181 Hf9133 keV) 60 124 95 95 95 46 59 Hf(344 keV) Cr ( 320 keV) 181 51 175 arbitrar , Sb (1692 keV) 124

er channel p (c)

Hf9133 keV) Zn ( 1115keV) Fe(1099keV) Sc ( 1120keV) Co (1173keV) 181 Sc ( 889 keV) Sc keV) ( 889 Counts Hf9133 keV) Sb ( 602 keV) 59 65 46 60 46 Hf(344 keV) Zr ( 7524keV) keV) ( 756 Zr Nb ( 765 keV) Nb keV) ( 765 Cr ( 320 keV) 181 124 Fe(1292 keV) Co (1332keV) 95 95 95 51 175 60 59 Sb (1692 keV) 124

( d )

Cs ( 795keV) 795keV) Cs ( Cs ( 562 and 56keV) Cs ( 604 keV) 134 134 134

Gamma-ray energy, keV 99 Fig.3.54. Gamma-ray spectra of typical (a) 1.0 ml of the initial Mo-molybdate (VI) supernatant, the formed Al(OH)3 precipitates after washing with 32 ml 3.5 M NaNO3 solutions of (b) pH 5 (c) pH 9.5 and (d) 1.0 ml of the final supernatant of pH 5 measured after acooling period of three months for 300s

203 adsorption on the positively charged alumina precipitate particles. These contaminant radionuclides usually escaped elimination from the molybdate

(VI) solutes via in-situ precipitation of Al(OH)3 at pH value of 9.5. The achieved radionuclide purification advantages is not advisable to promote 99Mo-molybdate (VI) solutes processing at pH value 5. This is due to the high retention % of 99Mo-molybate (VI) via anionic attachment (i.e, adsorption) with a loss in the order of ~ 69.8 % after washing with 32 ml 3.5 M NaNO3 solution of pH 5 and in the order of ~

28.51 % after washing with 32 ml 3.5 M NaNO3 solution of pH 9.5. 99 Thus processing of the Mo-molybdate (VI) solute via Al(OH)3 precipitation at pH 9.5 is preferred in the purification scheme of 99Mo- molybdate (VI) solute from thermal neutrons activation cross- contaminant radionuclides. 99 In both cases of Al(OH)3 precipitations from Mo-molybdate (VI) solutes, i.e, at pH values 9.5 and 5, no noticeable elimination of 134Cs- radionuclide from the solutions was achieved. This was contributed by competition between trace concentration of Cs+ and the bulk concentration of Na+ cations in the molybdate ( VI) solution to occupy the negatively charged active sites on the surface of the formed Al(OH)3 precipitate at pH ≥ 9.5 ( Mostafa, 2010). Conversely, from solutions of pH value 5 the surface of the formed precipitate is positively charged and acquires anion-exchange properties with adsorption of the 6- predominating hyptamolybdate (VI) [Mo7O24] anions.

204 3.6. Chromatographic purification of the final 99Mo-molybdate (VI) supernatant onto KNHCF (II) matrix: Precipitation of 99Mo-molybdate (VI) anions from solutions into the form of an insoluble gel matrix, for preparation of 99Mo / 99mTc gel generators, must be carried out from 99Mo-molybdate (VI) solutes of very high radionuclidic purity (El-Absy et al., 1993; 1994; 1997; Abou El-Enein, 1997). Generally, molybdenum (VI) gel matrices are known to have cation-exchange properties. After purification of the 99Mo-molybdate (VI) solutes via successive in-situ precipitations of Fe (III) minerals and Al (OH)3 from 4 M NaOH and 3.5 M

NaNO3 solutions of pH 9.5, respectively, the final supernatant was found to contain ~ 98.8 % of the initial 99Mo radionuclide together with ~ 100, 5 and 2 % of the initially detected 134Cs, 51Cr and 60Co radionuclides, respectively (Mostafa, et al., 2010). 134Cs radionuclide does not manifest any elimination onto the two solid phases due to facing high competition with the macro component Na+ cation in solution. From literature studies, Cs+ cations have high affinity towarde hexacyano ferrates (Prout et al., 1965; Volkhin, et al., 1967; Vlasselar et al., 1976; Lehto et al., 1987; Lehto, and Hajula, 1989; Lehto et al., 1990; Tanihara, 1993; Ismail, 1994; Tusa et al., 1994; Nene and Turel, 1994; Milyutin, 1995; El-Absy et al., 2002 and 2005). Thus, the 99Mo-molybdate (VI) supernatant was passed through potassium nickel hexacyanoferrate (II) KNHCF chromatographic column bed. In the following section the purification potentiality of hexacyanoferrate (II) ion-exchangers for purification of 99Mo-molybdate (VI) supernatants from the residual radiocontaminants of 134Cs, 60Co and 51Cr in presence of high concentration of sodium nitrate is investigated.

3.6.1. Preparation and characterization of potassium nickel hexacyanoferrate:

KNHCF matrix was prepared by adding 50 ml 0.5 M K4[Fe(CN)6] to 150 ml 1.0 M NiCl2 solution, as described previously (Volkhin, et al., 1967;

205 Ismail, 1994). The prepared KNHCF(II) matrix was in the form of dark blue granules pulverized and sieved to 0.12 - 0.24 mm particle size suitable for column operations.

3.6.1.1. Solubility of KNHCF (II) matrix: As well as other solid ferrocyanides, the matrix was chemically stable

(Haas, 1993). In 3.5 M NaNO3 solution, the concentration of dissolved ferrocyanide ion decreased from 20 to 5 ppm with increasing the solution pH value from 1 to 5. While very low solubility of 1-3 ppm was obtained from solutions of pH 11-12, no measurable solubility was detected in the pH range from 6 to10.

3.6.1.2. Thermogravimetric analysis of KNHCF(II) matrix: Fig. 3.55 shows the Thermogravimetric and differential thermal analysis TGA and DTA curves for 14.787 mg KNHCF(II) matrix. It indicates a weight loss of 2.118 mg (~ 14.3 %) in the temperature range from 25 to 250 °C, which may be assigned to release of 117.6 μmol H2O (lattice water content). In the temperature range from 250 to 436°C, a weight loss of 2.178 mg (~14.7 %) is obtained. It may be the resultant of matrix decomposition with partial release of carbon, as CO2, complete release of nitrogen, as NOχ and NH3, and metal oxidation to K2CO3, NiO and 1/2Fe2O3 associated with an exothermic peak at 337°C (Lehto et al., 1990). Thus, the net weight loss due to partial carbon and total nitrogen releases is 5.594 mg, which can be assigned to 232.9 μmol N and 194.1 μmol C. In the temperature range from 436 to 850 °C, a weight loss of 1.552 mg (~ 10.5 %) occurs. It is assigned to release of the remaining C from K2CO3, as CO2, leaving K2O in the residue ( Mimura et al., 1997 and 1998 ). Hence, the corresponding weight loss due to release of the remaining carbon is 0.424 mg ( i.e., 35.3 μmol C ) and the net total loss due to carbon release is 229.4 μmol C. The residual weight of 8.939

206

o Temp C

Fig. 3.55. TGA and DTA curves of the prepared KNHCF(II matrix.

mg ( ~ 60.4 % ) may be the oxidation products: K2O, NiO and 1/2Fe2O3 (Lehto et al., 1990). The corresponding metal net weight of 6.926 mg is assigned as 71.9 μmol K, 35.9 μmol Ni and 35.9 μmol Fe. Accordingly, the approximate molar ratios of K:Ni:Fe:C:N:H2O in the prepared KNHCF(II) matrix are 2:1:1:6:6:3, respectively.

3.6.1.3. Infrared analysis of KNHCF (II) matrix: Fig. 3.56 shows IR spectrum of the prepared KNHCF(II) matrix. The -1 bands at 595 and 2088 cm are ascribed to δFe-CN and νC≡N, respectively. The -1 bands at 1620 and 3397 cm are ascribed to δOH and νOH of uncoordinated water, respectively (Alam and Kamaluddin, 2000; Choudhury et al., 2002; Goubard et al 2002). From thermal and IR analyses data, the most probable molecular formula of the matrix is K2Ni[Fe(CN)6].3H2O (Gellings 1967; Ismail et al., 1998) with a typical face-centered cubic structure as shown by (Fig. 3.57) in agreement with the published data (Mimura et al., 1997).

207

Fig. 3.56. IR spectrum of the prepared KNHCF(II) matrix.

Fig. 3.57. XRD pattern of the prepared KNHCF(II) matrix.

208 3.6.2. 99Mo-molybdate(VI) feeding solutions: Gamma-ray spectrometric analysis indicated that ~ 85.0 % of 99Mo, of the irradiated 1.0 g MoO3 target, remained in the 3.5 M NaNO3 supernatant solution of pH 9.5 after successive precipitations of Fe(III) minerals and 99 Al(OH)3. Thereafter, a value of 13.8 % Mo was recovered in the washing filtrate of Al(OH)3. Table (3.15) shows that the supernatant was completely purified from the radiocontaminants of 59Fe, 65Zn, 95Zr, 92m,95Nb, 181Hf, 141Ce, 152Eu, 46Sc, 54Mn and 140La in addition to  99.9 % of 124 51 Sb. While 5.0 % of Cr (T1/2 = 27.70 d) remained in the supernatant 134 only, ~ 100 % as 85.8 and 14.2 % of Cs (T1/2 = 2.06 y) and 2.0 and 0.2 60 % of Co (T1/2 = 5.27 y) remained in the supernatant and washing filtrates, respectively. Fig. 3.58 shows typical gamma-ray spectra of the 99Mo- molybdate (VI) supernatant and the washing filtrate measured after cooling periods of 8 days and 3 months from the end of target irradiation. It is observed that 60Co could be detected in the supernatant of high Mo(VI) content before and after complete decay of 99Mo (Figure 58, a and b), while 51Cr and 134Cs were detected only after complete decay of 99Mo (Figure (3.58, b). On the other hand, 60Co and 134Cs were the detectable radiocontaminants found in the washing filtrate of Al(OH)3 measured after complete decay of 99Mo (Fig. 3.58, c and d). For 99Mo / 99mTc couple (Figure 3.58, a), the peak at 281 keV is attributed to the pile-up of 140.5 and 140.5 keV pulses, the peak at 880 keV is assigned to the summation of 140.5 and 739 keV quanta, whereas the peak at 921 keV is due to the summation of 140.5 and 778 keV quanta. For 134Cs (Figure 58, b), the peak at 1401 keV is the sum of 605 and 796 keV peaks in agreement with Van Eijk, et al. ( 1968) and Aycik (2009). Separate solutions of 4.3 and 0.7 m mol 99Mo-molybdate (VI) dissolved in 34 ml of the supernatant and the washing filtrate were used for feeding of the prepared identical KNHCF (II) columns at a flow rate of 0.2 ml / min and 25 oC, respectively.

209

)

(a)

) Tc (140.5 keV)

99m 159 keV ( 181 keV ( Mo / Mo 99 99 Mo 99 Mo (739 keV) (921 keV; 140.5 + 778 keV) (281 keV; 140.5 + 140.5 keV) k

99 k Mo (778 keV) Mo (367 keV) 99 99 Sum pea Sum pea Sum peak (880 keV; 140.5 + 739 keV)

Mo (581 keV) 99 Mo (823 keV) 99 Mo (961 keV) Co (1173 keV) Co (1333 keV) 99 60 60

(b)

Cs (605 keV) Cs (796 keV) Cs (802 keV) 134 134 134 Cs (570 keV) Co (1173 keV) Cs (563 keV) Co (1333 keV) 60 134 60 134

Cr (320 keV) Cs (475 keV) 51 Cs (1366 keV) 134 Sum peak (1401 keV; 605 + 796 keV) 134

Tc (140.5 keV) 99m

)

Mo / (c) 99 181 keV Counts per channel, arbitrary units (

Mo 99 (921 keV; 140.5 + 778 keV) Mo (739 keV) k 99 Mo (778 keV) Mo (367 keV)

99 99

Sum pea Sum peak (880 keV; 140.5 + 739 keV)

Cs (605 keV) (d) Cs (796 keV) 134 134 Co (1333 keV) Co (1173 keV) 60 60

Gamma-ray energy/ keV

Fig. 3.58. Gamma-ray spectra of 99Mo-molybdate(VI) feeding solutions: (a and b) of high- and (c and d) of low- Mo(VI) content measured after cooling periods of 8 days (a and c) and 3 months (b and d).

210 3.6.3. Chromatographic column operations: 3.6.3.1. Effect of Mo(VI) concentration: Identical 1.0 g KNHCF(II) columns were separately fed with 4.3 and 0.7 m mol 99Mo-molybdate (VI) dissolved in 34 ml of the supernatant and washing filtrate at a flow rate of 0.2 ml/min and 25 °C, respectively. Fig. 3.59 shows gamma-ray spectra of the feeding supernatant, the feeding effluent and the fed column matrix measured after a cooling period of 8 days. While no radiocontaminants were detected in the 99Mo-molybdate(VI) effluent, 60Co and 134Cs were detected on the column matrix together with some 99Mo- molybdate(VI). To recover the retained 99Mo-molybdate (VI) anions, the column was eluted four times, each with 5 ml 3.5 M NaNO3 solution of pH 9.5. Fig. 3.60, indicates that the retained 99Mo was not completely eluted from the column matrix and the obtained eluate appears to be free from 60Co and 134Cs. As gamma-ray spectra of both feeding solutions were more or less similar, except for the absence of 51Cr from the washing filtrate of

Al(OH)3 (Fig. 3.58), only gamma-ray spectra of the feeding solution of high Mo(VI) content were displayed. Radiometric analysis data of high and low 99Mo-molybdate(VI) feeding solutions are compiled in Table (3.18). Table (3.18) shows that for the feeding solution of high Mo(VI) content, 78.2 % of the fed 99Mo-molybdate (VI) was recovered in the effluent and further 16.3, 3.0, 0.4 and 0.3 % were recovered in the 1st, 2nd, 3rd and 4th 5 ml eluates, respectively, Figs. 3.61 and 3.62. The total recovery yield of Mo (VI), in this process, was found to be 98.2 % and 1.8 % 99Mo (i.e., 7.710-2 mmol Mo) remained onto the column bed. For the feeding solution of low Mo(VI) content, 49.2 % of the fed 99Mo- molybdate (VI) was recovered in the effluent and further 34.4, 3.1, 2.0 and 0.5 % were recovered in the 1st, 2nd, 3rd and 4th 5 ml eluates, respectively, Fig. 3.63 and 3.64. The total recovery yield of Mo(VI) was found to be 89.2 %, while 10.8 % 99Mo (i.e., 7.610-2 m mol Mo) remained

211

Tc (140.5 keV)

99m

)

Mo / 99 159 keV ( (a) Mo (181 keV) Mo 99 99 (281 keV; 140.5 + 140.5 keV)

(921 keV; 140.5 + 778 keV) Mo (739 keV) (880 keV; 140.5 + 739 keV) k

k 99 k Mo (367 keV) Mo (778 keV) 99

99 Sum pea Sum pea

Sum pea Mo (581 keV) 99 Mo (823 keV ) Mo (961 keV) 99 Co (1173 keV)

Co (1333 keV) 99 60 60

) Tc (140.5 keV)

99m 159 keV (

)

Mo /

Mo 99 ) 99 181 keV ( 739 keV (

Mo 99 Mo (921 keV; 140.5 + 778 keV) (b) (880 keV; 140.5 + 739 keV) k 99 (281 keV; 140.5 + 140.5 keV) k k Mo (778 keV) Mo (367 keV) 99 99 Sum pea Sum pea Sum pea Mo (961 keV)

Mo (823 keV) 99 99

Counts per channel, arbitrary units

Tc (140.5 keV) 99m

) Mo / 99

181 keV (

) Mo

Mo (739 keV) (c) 99 99 (281 keV; 140.5 + 140.5 keV) k Mo (778 keV)

99 Mo (367 keV) 795 keV (880 keV; 140.5 + 739 keV) ( 99 k (921 keV; 140.5 + 778 keV) Cs (605 keV) k Cs Mo (581 keV)

134 Sum pea 134 99 Mo (823 keV) Co (1333 keV) Co (1173 keV) 99 60 60 Sum pea Mo (961 keV) Sum pea 99

Gamma-ray energy/ keV

Fig. 3.59. Gamma-ray spectra of 99Mo-molybdate(VI): (a) feeding solution, (b) column effluent, and (c) column bed measured after a cooling period of 8 days.

212

Tc (140.5 keV) 99m

)

Mo / 99 181 keV

(

) Mo

Mo (739 keV) 99 (a) 99 (281 keV; 140.5 + 140.5 keV) k Mo (778 keV)

99 795 keV Mo (367 keV) (880 keV; 140.5 + 739 keV) ( k (921 keV; 140.5 + 778 keV) 99 Cs (605 keV) k Cs Mo (581 keV)

134 Sum pea 134 99 Mo (823 keV) Co (1333 keV) Co (1173 keV) 99 60 Sum pea 60

Mo (961 keV) Sum pea 99

Tc (140.5 keV) )

99m Mo / 181 keV

( 99 ) (b) Mo

99 ) Mo (739 keV) 795 keV 99 ( Mo (367 keV) Mo (778 keV) Cs (605 keV) Cs 99 99 134 802 keV Counts per channel, arbitrary units 134 ( Mo (581 keV)

Co (1333 keV) Co (1173 keV) 99 60 60 Cs

134

Tc (140.5 keV) 99m

)

Mo / (c) 99 181 keV ( Mo

99 Mo (739 keV) Mo (367 keV) Mo (778 keV) 99 99 99 Mo (921 keV) 99

Gamma-ray energy/ keV Fig. 3.60. Gamma-ray spectra of the column bed fed with 99Mo-molybdate(VI) solute (a) before and (b) after elution with 20 ml 3.5 M NaNO3 solution of pH9.5 and (c) the 99Mo molybdate(VI) eluate measured after a cooling period of 8 days.

213

99 Table (3.18). Effect of Mo(VI) concentration in NaNO3 solution on the uptake of Mo-molybdate(VI) anions and elimination of cross-contaminant radionuclides onto KNHCF(II) chromatographic columns. Experimental conditions: 34 ml 5 M NaNO3 solution of pH9.5 as feeding solution, 1.0 g KNHCF(II) matrix, flow rate of 0.2 ml/min, 4×5 ml 5 M NaNO3 solution of pH9.5 as column eluent, and room temperature (25° C).

99Mo-molybdate(VI) feeding solution % detected radionuclide and (uncertainty)

Mo content Detected Feeding Eluates KNiHCF(II) column matrix after radionuclide effluent elution 1st 2nd 3rd 4th

99Mo 78.2 (±1.3) 16.3 (±0.1) 3± (0.3) 0.4 (±0.2) 0.3 (±0.5) 1.8 (±1.4) i.e., 7.7×10-2±6.0×10-2 mmol Mo

51Cr ≥ 99.9 ND* ND* ND* ND* ND* 4.3 mmol 60Co 32.8 (±2.5) 19.4 (±2.3) ND* ND* ND* 47.8 (±3.4) (412.5 mg Mo) 134Cs ND* ND* ND* ND* ND* ≥ 99.9

Low-level ND* ND* ND* ND* ND* 86Rb (0.08 cps) and124Sb (0.04 cps) radioactivity**

99Mo 49.2 (±5.9) 34.4 (±0.6) 3.1 (±0.2) 2.0 (±0.1) 0.5 (±0.3) 10.8 (±5.9) i.e., 7.6×10-2 ±4.1×10-2 mmol Mo 0.7 mmol 51Cr ND* ND* ND* ND* ND* ND* (67.2 mg Mo) 60Co 30.9 (±3.7) 18.2 (±1.9) ND* ND* ND* 50.9 (±4.2)

134Cs ND* ND* ND* ND* ND* ≥ 99.9%

Low-level ND* ND* ND* ND* ND* ND* radioactivity**

*Not detected

** Detected only on the column bed fed with solution of high Mo content after complete decay of 99Mo.

214

)

T40.6 keV ) Cs ( 795 keV ) 181.1 keV 99m Mo ( 739 keV ) Mo ( 778.1 keV ) Mo ( 823.5 keV ) ( 99 99 134 99 Mo, Mo 99 99 Tc ( 280 keV ) Mo ( 366.5 keV ) Cs ( 604 keV) 99m 99

134 Mo ( 880.8keV ) Mo ( 920.8keV ) Mo ( 960.8keV ) Co ( 1173.6 keV ) keV ( 1173.6 Co ) keV ( 1332 Co 99 99 99 60 60

T40.6 keV ) 99m y Mo, Mo ( 181.1 keV ) 99 99 Cs ( 795 keV ) Mo ( 739 keV ) Mo ( 778.1 keV ) Mo ( 823.5 keV ) 99 99 134 99 Cs ( 604 keV ) Mo ( 366.5 keV ) 134 99 Co ( 1173.6 keV ) keV ( 1173.6 Co ) keV ( 1332 Co 60 60

arbitrar ,

er channel p

T40.6 keV ) 99m Mo, Mo ( 181.1 keV ) 99 99 Counts Cs ( 795 keV ) Mo ( 739keV ) Mo ( 778.1 keV ) 99 99 134 Cs ( 604 keV ) Mo ( 366.5 keV ) 134 99 Co ( 1173.6 keV ) keV ( 1173.6 Co ) keV ( 1332 Co 60 60

T40.6 keV ) 99m Mo, Mo ( 181.1 keV ) 99 99 Cs ( 795 keV ) Mo ( 739 keV ) Mo ( 778.1 keV ) 99 99 134 Cs ( 604 keV ) Mo ( 366.5 keV ) 99 134 Co ( 1173.6 keV ) keV ( 1173.6 Co ) keV ( 1332 Co 60 60

Gamma-ray energy, keV st nd rd Fig. 3.61. Gamma-ray spectra of high Mo(VI) content column after (a) 1 ,(b) 2 ,(c) 3 and (d) th 4 washing each with 5 ml 3.3 M NaNO solution measured after cooling time of 8 3 days for 100 s.

215

(a) T40.6 keV ) 99m Mo, Mo ( 181.1 keV )

) 99 99 Mo ( 739 keV ) Mo ( 778.1 keV ) 960.8keV ( Mo ( 366.5 keV ) 99 99 99 Mo ( 880.8keV ) Mo ( 920.8keV ) Mo 99 99 99

(b)

units y T40.6 keV ) 99m Mo, Mo ( 181.1 keV ) 99 99 arbitrar Mo ( 366.5 keV ) Mo ( 739 keV ) Mo ( 778.1 keV ) , 99 99 99

er channel p (c)

T40.6 keV ) 99m Counts Mo, Mo ( 181.1 keV ) 99 99 Mo ( 366.5 keV ) 99 Mo ( 739 keV ) 99

(d)

T40.6 keV ) 99m Mo, Mo ( 181.1 keV ) 99 99

Gamma-ray energy, keV

st nd rd th Fig. 3.62. Gamma-ray spectra of 0.2 ml of (a) 1 ,(b) 2 ,(c) 3 and (d ) 4 washing filtrates of the high Mo(VI) content column measured after cooling time of 8 days for 100 s.

216 T4(140.6 keV) 99m

Mo, Mo ( 181.2 keV ) 99 99 Cs ( 795keV) Mo ( 739.60 8keV ) Mo ( 778.94 keV ) 99 99 134 Mo ( 366.4 keV ) keV ( 366.4 Mo 99 Cs ( 604 keV) 134 Co ( 1173 keV) Co ( 1332 keV) Mo ( 880 8keV ) 60 60 99

)

T4(140.6 keV) 795keV 99m ( Cs Mo ( 739.60 8keV ) Mo ( 778.94 keV ) Mo, Mo ( 181.2 keV ) 99 99 134 99 99 units y Mo ( 366.4 keV ) keV ( 366.4 Mo 99 Cs ( 604 keV) 134 Mo ( 880 8keV ) Co ( 1173 keV) Co ( 1332 keV) 99 arbitrar 60 60 ,

er channel

) p T4(140.6 keV) 99m 795keV ( Mo, Mo ( 181.2 keV ) Cs Mo ( 739.60 8keV ) Mo ( 778.94 keV ) 99 99 99 99 134 Counts keV) 1332 Cs ( 604 keV) Mo ( 366.4 keV ) keV ( 366.4 Mo 99 134 Co ( 1173 keV) Co ( 60 60

) T4(140.6 keV) 99m 795keV ( Mo, Mo ( 181.2 keV ) 99 99 Cs Mo ( 739.60 8keV ) Mo ( 778.94 keV ) Mo ( 366.4 keV ) keV ( 366.4 Mo 99 99 134 99 Cs ( 604 keV) Co ( 1173 keV) Co ( 1332 keV) 134 60 60

Gamma-ray energy, keV

Fig. 3.63. Gamma-ray spectra of low Mo(VI) content column after (a) 1st ,(b) 2nd ,(c) 3rd and (d ) th 4 washing process measured after cooling time of 8 days for 100 s.

217

T4(140.6 keV) ) 99m keV Mo, Mo ( 181.2 keV ) 99 99 778 94 ( Mo ( 739.60 8keV ) Mo 99 99 Mo ( 366.4 keV ) keV ( 366.4 Mo

T4(140.6 keV) 99m y Mo, Mo ( 181.2 keV ) 99 99

Mo ( 739.60 8keV ) Mo ( 778.94 keV ) 99 99 Mo ( 366.4 keV ) keV ( 366.4 Mo 99 arbitrar ,

er channel p T4(140.6 keV) Counts 99m Mo, Mo ( 181.2 keV ) 99 99 Mo ( 366.4 keV ) keV ( 366.4 Mo 99

T4(140.6 keV) 99m Mo, Mo ( 181.2 keV ) 99 99 Mo ( 366.4 keV ) keV ( 366.4 Mo 99

Gamma-ray energy, keV Fig. 3.64. Gamma-ray spectra of 0.2 ml of (a) 1st ,(b) 2nd ,(c) 3rd and (d ) 4th washing filtrates of the low Mo(VI) content column measured after cooling time of 8 days fo 100 s.

218 onto the column bed. It is observed that the Mo (VI) loss (i.e., retention) onto the KNHCF(II) matrix was very small with a value not affected by Mo(VI) concentration in the feeding solutions. Since the KNHCF (II) 2- matrix acts as a cation exchanger (Sharygin, et al 2007) and MoO4 anions predominate in the solution of pH 9.5 (Greenwood 1998) they were easily traversed along the column matrix and eluted with the 3.5 M NaNO3 eluent. Mo(VI) loss may be attributed to chemical reactions with the KNHCF(II) matrix (Huys et al., 1964; Robbins, 2007). A precipitate of ferrocyanide molybdate was obtained on mixing sodium molybdate in HCl acid with

H4Fe(CN)6 at H/Mo and Mo/Fe ratios higher than 2. Below this ratio, the efficiency of precipitation was very poor (Huys et al., 1964). However the loss of molybdate(VI) anions onto the KNHCF(II) matrix was very small, it may be determinant when purification of carrier-free fission 99Mo is undertaken.

3.6.3.2. Assessment of the purification potential of KNHCF(II) matrix: To assess the purification potentiality of KNHCF(II) matrix, the aforementioned gamma-ray measurements were conducted again after a cooling period of 3 months. The corresponding data are compiled in Tables (3.18 and 3.19). Fig. 3.65 (curves a, b, c and d) shows gamma-ray spectra of the 99Mo- molybdate(VI) supernatant, feeding effluent, the 1st 5 ml eluate and the

KNHCF(II) matrix after column elution with 45 ml 3.5 M NaNO3 solution of pH 9.5. It was found that, 60Co partially- and 51Cr completely- passed off the column together with the 99Mo-molybdate(VI) effluent (Figure 3.65, b). Cobalt-60 was detected only in the 1st 5 ml eluate (Fig. 3.65, c). Cesium- 86 124 134, Rb (T1/2 = 18.6 d) and Sb (T1/2 = 60.2 d) were completely and strongly fixed onto the column bed with the remaining 60Co (Fig.3.65, d). Due to their low-level radioactivity, 86Rb and124Sb were only concentrated

219

(a)

Cs (605 keV) Cs (802 keV) Cs (796 keV) 134 134 134 Co (1173 keV) Cs (570 keV) Co (1333 keV) Cs (563 keV) 60 60 134 134 Cr (320 keV) Cs (1366 keV) Cs (475 keV) 51 134 Sum peak (1401 keV; 605 + 796 keV) 134

(b)

Co (1333 keV) Cr (320 keV) 60 Co (1173 keV) 51

(c)

)

Counts per channel, arbitrary units 1173 keV ( 1333 keV ( Co Co 60 60

)

) )

keV) ) ) 605 keV 603 keV ( (

796 keV ) 801 keV ( (

63, 569 Cs Sb )

) 1173 keV (d) Cs 1401 keV; 605 + 796 keV 1333 keV Cs ( 134 ( 124 (

134 k 134 ) Cs (5 Co Co ea 60 134 1365 keV p 60 ( Cs (475 keV) 1038 keV (

1077 keV 134 Cs ( Sum Cs 134 1691 keV ( Rb

134 86 Sb

124

Gamma-ray energy/ keV

Fig. 3.65. Gamma-ray spectra of 99Mo-molybdate(VI) (a) feeding solution, (b) column effluent, st (c) 1 5 ml eluate and (d) KNHCF(II) matrix after elution with 20 ml 3.5 M NaNO3 solution of pH 9.5 measured after a cooling period of 3 months.

220 onto the column matrix bed with solutions of high Mo(VI) content. The corresponding counting rates of 86Rb and 124Sb were 0.08 and 0.04 cps, 2- respectively. As CrO4 anions predominate in neutral and alkali solutions (Zhao, et al., 1998; Qafoku, et al., 2009), 51Cr radionuclide traversed the column bed with the 99Mo-molybdate(VI) effluent. Cobalt (II) has lower

Kd-values than Cs(I) on different ferrocyanides from aqueous solutions in the pH range from 1 to 8 (Ismail et a., 1998; Nilchi et al., 2009). The % uptake of Co(II) on KNHCF(II) increases with increasing the solution pH value from 2 to 5.5 (Ismail et al., 2002; Smiciklas, et al., 2006). In nitrate media of pH 9.5, ~ 60 % of Co(II) forms cationic species (~ 45 % as Co2+, + 4+ ~ 10 % as CoOH and ~ 5 % as Co4(OH)4 ) and the remaining ~ 40 % 60 Co forms neutral species of Co(OH)2 (Smiciklas et al., 2006). Table (3.19) shows that while 32.8 and 19.4 % of 60Co were detected in the feeding effluent of high Mo(VI) content and the 1st 5 ml eluate, respectively, the remaining 47.8 % 60Co was strongly fixed onto the column bed, even after passing further 15 ml of the eluent. For the feeding solution of low Mo(VI) content, 30.9 and 18.2 % of 60Co were detected in the feeding effluent and the 1st 5 ml eluate, respectively, and the remaining 50.9 % 60Co was strongly fixed onto the column bed even after passing further 15 ml of the eluent. Adsorption of 60Co radionuclide onto the column matrix may be occurred via precipitation reactions of Co(OH)2 and ion exchange/hydrolytic sorption reactions of Co(II) cations and 60 hydrolyzed Co(II) cations. Nevertheless ~ 90 % of Co exists as Co(OH)2 at pH 11 as Smiciklas, et al, (2006). The pH values  9.5 were not considered, to avoid any partial dissolution of the column matrix(Haas, 1993). Desorption of 60Co radionuclide in the 1st 5 ml eluate may be due to ion exchange reaction between Co2+ cations onto the surface of the column + matrix and Na cations from the 3.5 M NaNO3 eluent.

221 The affinity series of alkali metal cations towards ferrocyanides shows high selectivity for Cs+ and Rb+ compared to Na+ and Li+ in the following order: Cs+ > Rb+> K+ >> Na+ and Li+ (Valantiti, 1972; Caletka et al., 1976; Malik et al., 1977). Therefore, the prepared KNHCF(II) matrix was converted from K+-form to Na+-form by preconditioning with 3.5 M 134 86 NaNO3 solution of pH 9.5. Complete elimination of Cs and Rb may be due to ion-exchange reaction between Cs+ and Rb+ cations from the molybdate(VI) solute and Na+ cations onto the surface of the column matrix.

The oxide of Sb(OH)3 predominates in solution over the pH range from 1 to 11. Its formation becomes faster at lower pH values with the formation of insoluble Sb2O3, according to the following reaction (Inoue et al., 1980; Loureiro et al., 2006):

2Sb(OH)3 = Sb2O3 + 3H2O

Thus, purification of the molybdate (VI) solute from 124Sb may be due to precipitation of Sb(OH)3 and/or Sb2O3 onto the surface of the column matrix. Except for the small increase in the elimination percentage of 60Co from the feeding solution of low Mo(VI) content onto the KNHCF 2- (II) matrix at a flow rate of 0.2 ml/min, the sorption behavior of MoO4 anions and cross-contaminant radionuclides from 3.5 M NaNO3 solution of pH9.5 was not noticeably affected by Mo(VI) concentration in the feeding solution (Tables 3.18 and 3.19). Table (3.19): compiles elimination of cross-contaminant radionuclides from thermal neutron 99 activated 1.0 g MoO3 in the form of Mo- molybdate solute on successively precipitated Fe (OH)3 and Al (OH)3 and passing through KNHCF chromatographic column.

222 Table (3.19). Radiocontaminants elimination from 99Mo-molybdate solute onto successively in-situ precipitated Fe (III) minerals and Al (OH) precipitate and KNFCN (II) chromatographic column matrix. 3

Radionuclide Elimination % Remaining % in solution Fe(OH)3 Al(OH)3 KNHCF column 141Ce 100 ------140La 100 ------152Eu 100 ------54Mn 100 ------92mNb 100 ------95Nb 97 3* ------60Co 80 18 1 % 1 % 59Fe 70 30 ------46Sc 50 50 ------51Cr 35 60 3.63 1.37 99Mo 0.97 0.23 0.6 98.2 124Sb ------~ 99 ~ 1 --- 65Zn ------100 ------95Zr ------100 ------181&175Hf ------100 ------134Cs ------100 ----- 86Rb ND ND 100 ND * of the regenerated 95Nb radionuclide due to nuclear decay of its parent 95Zr radionuclide.

3.6.3.3. Effect of flow rate of the 99Mo-molybdate (VI) solute: Chromatographic columns packed with 1.0 g KNHCF(II) were fed with 34 ml of the 99Mo-molybdate(VI) solution of high Mo(VI) content at a flow rate of 5 ml/min and 25°C. Fig. 3. 66 (curves a, b, c and d) shows gamma-ray spectra of: (a) 2.0 ml of the first 99Mo-molybdate (VI) feeding solution onto chromatographic column of KNHCF, (b) KNHCF chromatographic column after final washing process and (c) 2.0 ml of the 99Mo-molybdate (VI) effluent at a flow rate of 5 ml / min measured after a cooling period of three months for 2000 s. Analysis of the obtained gamma-ray spectra of Fig. 3.66 showed that on increasing the flow rate of the feeding solution from 0.2 to 5 ml/min, the sorption behavior of the molybdate(VI) anions and the cross-contaminant

radionuclides onto the KNHCF(II) matrix from 3.5 M NaNO3 solution of pH 9.5 were more or less comparable with the data compiled in Tables (3.18 and 3.19) corresponding to flow rate 0.2 ml/min. Thus, purification of the 99Mo- molybdate (VI) solutes from cross-contaminant radionuclides at higher flow rates is preferred for saving both of the processing time and consequently loss of 99Mo radioactivity due to nuclear decay.

223

( a ) Cs 795,78 keV ) Cs ( 801.92 keV ) Co ( 1173.5 keV ) 134 134 Co ( 1333 keV ) Cs ( 1366.07 keV ) Eu ( 1407.5 keV ) Cs ( 563.05keV ) Cs ( 569.17keV ) Cs ( 604.57 keV ) 134

Cs ( 475 keV ) Cs keV ( 475 134 134 152 Cr ( 320 keV Cr ) keV ( 320 134 134 134 134 51 y

arbitrar

, ( b ) )

keV Cs ( 563.05keV ) Cs ( 569.17keV ) Cs ( 604.57 keV ) 475 134 134 134 ( Cs ( 795,78 keV ) Cs ( 801.92 keV ) Cs er channel 134 134 134 Co ( 1333 keV ) Cs ( 1366.07 keV ) Eu ( 1407.5 keV ) p 134 134 152 Cs ( 1168.7 keV ) Co ( 1173.9 keV ) 134 134 Cs ( 1038.96 keV ) 134 Counts

( c )

Co ( 1333 keV ) Co ( 1173.9 keV ) 134 134

Gamma-ray energy, keV

Fig. 3.66. Gamma-ray spectra of: (a) 2.0 ml of the first 99Mo-molybdate (VI) feeding solution of KNHCF column (3) , ( b) KNHCF column after final washing process and (c) 2.0 ml of the 99Mo-molybdate (VI) effluent at a flow rate of 5 ml / min measured after cooling periods of three months for 2000 s.

224 3.7. 99Mo / 99mTc generator: Zirconium 99Mo-molybdate gel matrix was prepared via in-situ precipitation of acidic zirconium-oxy-chloride solution with the highly radionuclidic pure sodium 99Mo-molybdate (VI) solute. The gel matrix was washed, air dried, packed in the form of chromatographic column and conditioned for 99mTc elution, therafter. The generated 99mTc radionuclide was eluted with 0.9 % saline solution and the obtained eluates were chemically and radiochemically analyzed.

3.7.1. Preparation and characterization of inactive zirconium molybdate gel: 3.7.1.1. Preparation of zirconium molybdate gel: Freshly zirconium solution (0.0576 M) was prepared by dissolving

3.25 g zirconium-oxy-chloride ZrOCl2.8H2O, in 140 ml distilled water and left standing for 24 h to stabilize the pH value. The sodium molybdate (VI) solution was prepared by dissolving 0.8 g MoO3 in 10 ml 2 M NaOH according to the following reaction:

MoO3 + 2NaOH Na2MoO4 + H2O

few drops of 10 % w/v H2O2 solution were added to convert the reduced molybdenum species to Mo (VI) species and then gentle heated to expel

excess of H2O2. The obtained molybdate solution was acidified by nitric acid to pH value 9.5 with a final volume of 35 ml (0.00555 M). The zirconium solution was added dropwisely to the molybdate solution and the pH of the mixture solution was raised by adding NaOH solution with strong mixing until precipitation at pH value of 4.7. The final concentrations of Zr and Mo in the mixture solution were found to be 0.0576

225 and 0.0317 M with Zr : Mo molar ratio of 1.817 : 1. The formed gel was filtrated, washed by distilled water and air dried for 24 hour at 50 oC. The modification of pH value of the 99Mo-molybdate solution used in preparation of the ZrMo gels changes the chemical structure of the gel matrix. The molybdate solutes form different species in solution at different pH values (Scadden and Ballon, 1960; Aveston, 1964; Greenwood and Earnshw, 1998; Mitchell, 1990; El- Absy, 1997; Mitchell, 1999):

2- 6- 4- 2+ [MoO4] ↔ [Mo7O24] ↔ [Mo8O26] ↔ MoO3.2H2O↓ ↔ [MoO2] pH > 6 pH 5 -3 pH 3-2 pH 0.9 pH < o.9 n.molybdate heptamolybdate octamolybdate hydrated molybdenum molybdyl trioxide ion

The normal molybdate ions condense into polymolybdate ions with increasing the H+-ion concentration in solution to pH < 6 (Monroy, et al 2003).

2- + (2x-y)- xMoO4 + yH MoxO2(OH) 8x-y-2z + (y-4x +z)H2O

Assuming that zirconyl oxy-chloride in aqueous solutions are hydrolyzed (Blumenthal, 1958; Monroy, et al 2003) according to the reaction:

+ + - ZrOCl2 + H2O ZrOOH + H + 2Cl

It is possible to suggest that during the addition of the zirconium solution to the polymolybdate aqueous solution Zr might suffer hydrolysis with the precipitation of hydrous zirconia:

+ - ZrOOH + OH ZrO2.xH2O + (1-x) H2O

226 An equilibrium may be reached between adsorbed water and adsorbed polymolybdate anions. The resulting reaction can be represented as follows:

(2x-y)- (2x-y) - ZrO2.xH2O + wMoxO2(OH) 8x-y-2z [ZrO2.(x-w) H2O.MoxOz(OH) 8x-y-2z ] + wH2O

The variation of zirconium to molybdate molar ratio determines the water content and the number of basic structural units of polymolybdate content in the gel. An increase in the molybdenum concentration decreases the water content due displacement of the water molecules by the polymolybdate anions and decreasing the porosity.

3.7.1.2. Characterization of the zirconium molybdate gel: The obtained zirconium molybdate gel matrix was in the form of a white-yellow glassy granules. The immersion of freshly prepared precipitate dried at 50 oC in water provided a method of reducing the gel agglomerates to particle size suitable for chromatographic column operations. Samples of the prepared gel was characterized by thermograviometeric analysis TGA, differential thermal analysis DTA (Fig. 67), XRD patterns (Fig. 3.68) and chromatographic column elution operations of the generated 99mTc radionuclide.

3.7. 1.2. 1. Thermal analysis of ZrMo matrix: Fig. 3.67 shows thermograviometeric analysis TGA and differential thermal analysis DTA curves for 22.019 mg ZrMo matrix. The TGA curve shows a continuous irreversible loss of water of hydration. There is about 12.85 % loss up to 200 °C which may be due to the loss of interstitial water and water of crystallization. The loss (5.4 %) over the range 200-600 °C may be due to the loss of coordinated water and condensation of hydroxyl groups.

227

Fig. 3.67: DTG and TGA curves of ZrMo gel matrix

Intensity. ksps

Angle. 2Ө

Fig. 3.68: X-ray diffraction pattern of ZrMo gel matrix

228 The total loss (18.25 %) up to 600 °C and the curve pattern suggests that the gel matrix is quite stable up to ≤ 600 °C. The DTA curve for zirconium molybdate gel material dried at 50 °C shows that there is an initial loss of water in the temperature range 50-200 °C corresponding to loss of free water in the form of endothermic peaks at 90.41 and 132.42 °C. The endothermic peaks at 90.41 and 132.4 °C. due to water release ~ 12.85 % intera-molecules in the temperature range from 25 to 200 °C and 1.189 mg

(~ 5.4 %) assigned to release of H2O (lattice water content (inter molecules) in the temperature range from 200 to 600 °C. The exothermic peak at 577 °C due to formation of metal oxides (Lehto et al., 1990; Minura et al., 1997 and 1998). The obtained data showed that Zr /Mo gel material is thermally stable up to 600 °C. Suppose that the chemical (2x-y)- - composition of ZrMo is such as [ZrO2.(x-w) H2O.MoxOz(OH) 8x-y-2z ] , the thermal decomposition can be described as follows:

50-150 oC (2x-y)- (2x-y)- ZrO2.(x-w) H2O.MoxOz(OH) 8x-y-2z Zr.MoxOz(OH) 8x-y-2z - H2O > 600 oC (2x-y)- Zr.MoxOz(OH) 8x-y-2z ZrO2 + ZrMo2O8

3.7. 1.2.2. XRD analysis of ZrMo matrix: Fig. 3.68 shows X-ray diffraction pattern of ZrMo matrix. It indicates that amorphous material was obtained due to rapid precipitation at pH 4.7 in agreement with (Evans, 1987).

3.7.2. Preparation of 99Mo/ 99mTc generator based on zirconium 99Mo- molybdate gel matrix:

Sample of 1 g MoO3 wrapped in 0.6 g Al foil was irradiated in the Egyptian Second Research Reactor for ~ 4 h in a thermal neutron flux of ~ 1014 n.cm-2.s-1. The irradiated sample was transferred to a dissolver,

229 dissolved by 34 ml 5 M NaOH solution in presence of 30 mg FeCl3,6H2O and 0.5 ml H2O2 solution as an oxidant. After sequential purification of the 99 Mo-molybdate (VI) solute via precipitation of Fe(OH)3 and Al(OH)3 and passing onto KNHCF chromatographic column, elimination of 140La, 152Eu, 141Ce, 54Mn, 51Cr, 92mNb, 95Nb, 46Sc, 59Fe, 60Co, 124Sb, 65Zn, 95Zr, 181&175Hf, 134Cs and 86Rb was achieved as shown in Table (3. 18 and 3.19). The 99Mo- molybdate (VI) solutes of pH 9.5 were further processed for preparation of ZrMo gel matrices as described above. 1.0 g of the prepared zirconium 99Mo-molybdate matrix in 10 ml 0.9 % NaCl solution (saline) was transferred to a glass column of 0.8 cm i.d × 30 cm length plugged with a small piece of quartz wool. The column was conditioned by passing furtherer 50 ml 0.9 % NaCl solution. The pH-value of the washing and conditioning filtrates and eluates were measured using pH paper. Washing filtrates were weakly acidic (pH 5 - 5.5). The column was left for the next day covered with few ml,s of 0.9 % NaCl solution to reach the maximum radioactive equilibrium state of the 99Mo - 99mTc isobars. Technetium-99m elution was carried out with passing 10 ml 0.9 % NaCl solution through the column bed at a flow rate of 0.5 ml / min and room temperature ~ 25 oC. Fig. 3.69 (curves a, b, c and d) shows Gamma-ray spectra of 1.0 ml of the radionuclidic pure 99Mo-molybdate (VI) solute, 1.0 ml of the filtrate after precipitation of the zirconium molybdate gel, 1.0 ml of the washing solution of the gel with distilled water and 1.0 ml of the washing solution of the gel with saline solution measured for 500 s. Although the counting rate is long enough, the gamma-ray energy peaks of 99Mo (181, 739 and 778 keg) were not detected in the gamma-ray spectra of filtrate and the washing filtrate by distilled water and / or 0.9 % NaCl solution, indicating complete precipitation of the 99Mo-molybdate (VI) anions into the formed ZrMo gel material and its chemical stability in water and saline solution.

230

Tc (140 keV), 99m (a) Mo, Mo (181 keV) 99 99 Tc (281 keV) Mo (366 keV) 99m 99 Mo (739 keV) Mo (778 keV) Mo (823keV) Mo (880 keV) Mo (920 keV) Mo (960keV) 99 99 99 99 99 99

Tc (140 keV) keV) (140 Tc m 99 (b)

y arbitrar ,

Tc (140 keV) keV) (140 Tc

m (c) 99 er channel p Counts

Tc (140keV)

m 99 (d)

Tc (281 keV) 99m

Gamma-ray energy, keV Fig. 3.69. Gamma-ray spectra of (a) 1.0 ml of molybdate (VI) solute (b) 10 ml of the filtrate after

precipitation of zirconium molybdate gel (c) 1.0 ml of the washing solution of the gel with

distilled water (d) 1.0 ml of the washing solution of the gel with saline solution measured

for 500 s

231 Fig. 3.70 (curves a, b, c and d) shows gamma-ray spectra of 0.05 g of the prepared ZrMo gel matrix, the packed ZrMo chromatographic column before elution and after 1st elution measured after cooling period of 12 day from the end of irradiation and the residual activity of the column measured after 3 months for the counting rates 500, 200 and 200 and 3000, s, respectively. 51Cr radionuclide was the only detected contaminant onto the formed gel matrix indicating complete purification of the 99Mo-molybdate (VI) solutes from the other radiocontaminants (Tables 3.18 and 3.19).

3.7.3. Elution performance and Quality control indices: Elution performance of the 99Mo / 99mTc chromatographic column type generator and quality control indices of the 99mTc eluates have been extensively investigated.

3.7.3.1. Elution profile and elution yield of 99mTc: The obtained generator eluates were of clear appearance. The elution yield in 10 ml saline was found to be ≥ 82.7 ± 0.4 % of the total 99mTc radioactivity present onto the ZrMo column. 99mTc elution yield from the prepared highly purified ZrMo gel matrix is higher than that commonly obtained from ZrMo (65-70 %) (El-Kholy, 1998; Liang, 1996) and titanium molybdate gel generator (65%) (Vanaja et al., 1987) due to direct oxidation of the reduced - TcO4 anions which increase the elution yield as a good advantage for this gel generator. Fig. 3.71 shows a typical elution profile of 99mTc from ZrMo column with 10 ml 0.9 % NaCl solution at a flow rate of 0.5 ml / min. The eluted 99mTc radioactivity was concentrated in the first 5 ml of eluate, and ~ 95.7 % of the eluted 99mTc was concentrated in ~ 7 ml of the obtained eluate. This is in agreement, to a great extent, with the results of (Liang Q 1996; Sakr, 2010), meaning that high 99mTc volume specific activity could be achieved from the prepared generator.

232

Tc (140 keV),

99m Mo, Mo (181 keV)

99 99 (a)

Mo (739 keV) Mo (778 keV) Mo (823keV) Mo (880 keV) Mo (920 keV) Mo (960keV) 99 99 99 99 99 99

Mo ( 366 keV) Cr ( 320 keV ) 51 99 units y Tc (140 keV), 99m ) Mo, Mo (181 keV) keV 99 99 960 arbitrar ( , Mo (739 keV) Mo (778 keV) Mo (823keV) Mo (880 keV) Mo (920 keV) Mo Tc ( 281 keV) 99 99 99 99 99 99 Mo ( 366 keV) Cr ( 320 keV ) (b) 99m 51 99

er channel p Counts

Tc (140 keV), 99m Mo, Mo (181 keV) 99 99

)

eV (c) k 960 (

o Mo (739 keV) Mo (778 keV) Mo (823keV) Mo (880 keV) Mo (920 keV) M Tc ( 281 keV) Mo ( 366 keV) Cr ( 320 keV ) 99 99 99 99 99 99 99m 51 99

(d)

Co (1173 keV) Co (1332 keV) 60 60

Gamma-ray energy, keV Fig. 3.70. Gamma-ray spectra of (a) 0.05 g of the ZrMo gel matrix (b) ZrMo chromatographic column before 1st elution (c) ZrMo gel chromatographi column after 1st elution measured after cooling period of 12 day and (d) residual ZrMo gel detected after 3 months from the end of irradiation for 500, 200, 200 and 3000 respectively.

233 Tc radioactivity % Tc radioactivity 99m

ml of eluate

Fig. 3.71: Typical elution profile of 99mTc from ZrMo column with 10 ml 0.9 % NaCl solution at a flow rate of 0.5 ml / mi.

234 3.7.3.2. Radionuclidic purity of the 99mTc eluates: Radionuclidic purity of the 99mTc eluates is the proportion of 99mTc radionuclide to the total eluate radioactivity. The radionuclidic purity of 99mTc eluates was determined by gamma-ray spectrometry using high purity germanium (HPGe) multichannel analyzer and half-life determination using NaI (Tl) scintillation counter. Fig. 3.72 (curves a, b, c, d, e and f) shows gamma-ray spectra of 1.0 ml of the 1st, 2nd, 3rd, 4th , 5th and 6th elution eluates measured for 200 s immediately after elution. Only the (140 keV) peak was found. Fig. 3.73 (curves a, b, c, d, e and f) shows gamma-ray spectra of the residual activity from the above 1st, 2nd, 3rd, 4th , 5th and 6th elution process measured after 72 h from elution for 1000 s. No gamma-ray energy peak of 99Mo (181, 366, 739 and 778 keV) were detected with the 140 keV of 99mTc on the spectra of the residual activity. Radionuclidic purity of 99mTc was verified from the corresponding decay curves. As shown in Fig. 3.74 a straight line with a slope of (- 0.5) is obtained. Since slope = - 0.43 λ (where λ = -

0.693/T1/2) (Ehmann, 1991), it can be illustrated by calculation that the slope of - 0.5 corresponds to 6 h (the half-life of 99mTc radionuclide), which verify high purity of the 99mTc eluate. If the total residual radioactivity after 72 h decay period was considered to represent 99Mo breakthrough, the radionuclidic purity of 99mTc eluates was found to be 99.99 %. This value is suitable according to USAEC standard requirements for 99mTc applications in nuclear medicine (IAEA, 1971 and 1989; Molinski, 1982; Boyd, 1982; Rayudu, 1983).

235

Tc (281 keV)

Tc (140 keV) 99m

99m (a)

Tc (281 keV) 99m

Tc (281 keV) 99m (b)

keV) (140 Tc m 99 (c)

Tc (281 keV) 99m

(d) Tc (140 keV) keV) (140 Tc

m 99

Tc (281 keV) 99m

Tc (140 keV) keV) (140 Tc

m 99 (e)

Tc (140 keV) keV) (140 Tc m Counts per channel, arbitrary units units arbitrary channel, per Counts 99

(f) Tc (281 keV) 99m

Tc (281 keV) 99m

Gamma-ray energy, keV Fig. 3.72: Gamma-ray spectra of the 99mTc eluted( a ) 1st ( b) 2nd ( c ) 3rd (d) 4th (e) 5th and (f) 6th elution process measured directly for 200 s. 236 (a)

(b)

(c)

Counts per channel, arbitrary units (d)

(e)

(f)

Gamma-ray energy, keV Fig. 3.73: Gamma-ray spectra of 99mTc eluted residual activity of (a) 1s (b) 2nd (c) 3rd (d) 4th (e) 5th and (f) 6th elution process measured after 72 h from each elution for 1000 s.

237

1000000

100000

10000

1000 Counting rate cpm rate Counting

100

10 0 1020304050607080 Decay time, h

Fig. 3.74: Decay curve of 99mTc eluted from ZrMo colum.

238 3.7.3.3. Radiochemical purity: Radiochemical purity is defined as the percentage of the 99mTc 99m - radioactivity that is present in the desired chemical form e.g, TcO4 , to the total radioactivity. The radiochemical purity of 99mTc was determined by the ascending paper chromatography using 85 % methanol as a developing solvent. Fig. 3.75. shows typical radiochromatogram for the 99m Tc eluate from 1.0 g ZrMo gel. It indicates one Rf value at 0.67 99m - corresponding to TcO4 anion (El-Absy and El-Bayoumy, 1990; El- Absy, 1991) with radiochemical purity ≥ 97.7 %.

3.7.3.4. Chemical purity: Zirconium concentration in the eluates was ≤ 0.3 ppm within the accepted limit ≤ 5 ppm (Savvin, 1961;.Suzuki, 2009). The molybdenum concentration in the eluate was found to be in the range of 3-4 µg / ml. Such molybdenum content in the 99mTc eluate is below the permitted limit for medical applications ( Narasimhan, 1980a; Vanaja et al 1987; El- Absy, 1993, 1994, 1997; Maoliang, 1996; Boyd, 1997). The elution yield and breakthrough of 99Mo in 99mTc eluates were affected by Zr:Mo molar ratio. At high Zr concentration, the efficiency and the elution yield were decreased whereas, at low Zr concentration, breakthrough of 99Mo 99m - is increased. The low elution yield of TcO4 anions has been treated by the addition of a strong oxidizing agent to the eluent, such as chlorine, chromate, nitrate or nitrite ions (El-Absy et al., 1993; 1994; 1997; Abou El-Enein, 1997). One major improvement was to incorporate into the bed matrix of the generator a solid oxidant, such as cerric and ferric oxides, to serve as an in- situ oxidizing agent (Ramamoothy, 1980; Evans, 1981). Obviously the 99Mo-molybdate (VI) solutes contain traces of chemically stable Fe soluble impurity which may be improved the elution yield of 99mTc from the generators based on highly purified 99Mo-molybdate solutes.

239

R f = 0.67 80000

60000

40000

Radioactivity, cpm Radioactivity, Solvent front

20000

0 024681012 Travelled distance, cm

Fig. 3.75: Typical Radiochromatogram of the obtained 99mTc eluates.

240 3.7.3.5. pH determination: pH-value of the eluates was 5.8 higher than Evans, et al (1987). El- Kholy, (1998) precipitated ZrMo from acidic media of pH-values 1.0, 1.5 and 1.75 with eluates pH-values of 2.3-3.5. Table (3.20) compiles the elution yield and quality control data of 99mTc eluates from 1.0 g high radionuclidic pure Zr99Mo gel generator. Reproducible elution yield, high radionuclidic, radiochemical and chemical purity and suitable pH value according to both of the European and US Pharmacopeias (Zool I., 2007; El-Absy and Abou El Enien, 1997; Susuki, 2009) were obtained with repeated elution frequencies.

Table (3.20) Elution yield and quality control data of 99mTc eluates from1g high radionuclidic pure Zr99Mo gel generator.

Elution no Elution yield Mo concentration, Zr concentration, R. C*% R. N**% pH value % µg/ml µg/ml 1 82.9 3 0.3 97.7 99.99 5.8 2 82.8 3 0.3 97.7 99.99 5.8 3 82.7 4 0.2 97.7 99.99 5.8 4 82.8 3 0.3 97.7 99.99 5.8 5 82 .7 3 0.2 97.7 99.99 5.8 6 82.2 2 0.2 97.7 99.99 5.8 *R. C. is radiochemical purity. **R. N. is radionuclidic purity

Zirconium molybdate gel is a cation exchanger with an open pore structure - that allows the free distribution of the anionic TcO4 resulting in easy elution and high elution yield of 99mTc radionuclide by saline solution leaving the parent 99Mo radionuclide in the gel matrix ZrMo. It is concluded that 99Mo / 99mTc generator in the form of chromatographic column packed with high purity 1.0 g Zr99Mo, precipitated from highly purified 99Mo-molybdate (VI) solute via sequental co-precipitation on Fe (III) minerals and Al (OH)3 precipitates at pH value 9.5 and / or adsorption via 99m feeding on KNHCF chromatographic column provided Tc eluates with saline solution in good agreement with the ideal European and US

241 Pharmacopeias ( Zool et al., 2007; El-Absy and Abou El Enien, 1997; Susuki, 2009).

When, MoO3 target is irradiated in the Second Egyptian Research Reactor ETRR-2 for a period of 100 hours with a maximum neutron flux of ~ 1 x 1014 n /cm2 s, 99Mo specific activity of 1313 mCi will be obtained. The prepared Zr99Mo gel matrix can overcome the high specific activity of alumina-loaded fission 99Mo generators. Other advantages for gel generators from neutron irradiated MoO3, are inexpensive, simple and single-step procedure. Besides to, chromatographic generators containing fission-product 99Mo need for high capital cost of the processing planet. This prepared ZrMo with pre-purified 99Mo-molybdate (VI) resolves the disadvantages of post irradiated ZrMo gel and prevents decontamination of the 99mTc eluates with additional radionuclides besides to radiation hazard and matrix destruction products of radioactive molybdenum.

242 SUMMARY

The thesis entitled "Chromatographic Purification of Neutron Capture Molybdenum-99 from Cross-contaminant Radionuclides" comprises three chapters; introduction, experimental, and results and discussion.

Chapter 1; is the introduction, It includes brief accounts on the applications of 99Mo / 99mTc gel generators, chemistry and radiochemistry of molybdenum, methods of production of molybdenum-99 radionuclide, activation molybdenum-99 cross-contaminant radionuclides (type and sources), 99Mo / 99mTc radioisotope generators, molybdate (VI) gel matrices, , chemistry and radiochemistry of iron, transformations of iron oxides and oxyhydroxides, colloidal and sorption behavior properties of iron (III) minerals, chemistry of aluminum, ferrocyanides as fixed column bed, methods of separation and purification of activation molybdenum-99 and literature survey on related separations and purifications.

Chapter 2; includes the chemicals, equipments and experimental procedures. Techniques used for preparation, irradiation and dissolution of the molybdenum targets. Radiometeric identification of the product radionuclides. Methods of separation and purification of neutron activation 99Mo-molybdate solution. Chemical analysis and identification of modes of transformation of Fe (III) iron to Fe (III) minerals by Raman spectroscopy. Preparation and characterization of KNHCF matrix and zirconium molybdate gel. Preparation of 99Mo / 99mTc generators and elution performance of 99mTc. It includes, also, assessment of 99Mo uptake, elimination % of cross-contaminants onto successively precipitated Fe (III) and Al (III) hydroxides and KNHCF column.

243

Chapter 3; This chapter includes in a systematic mode the results and discussion of the purification process of neutron activated molybdenum- 99from cross-contaminant radionuclides. The individual target materials

(MoO3 and Al foil) were irradiated in the Egyptian Second Research Reactor ETRR-2 for ~ 4 hours with a thermal neutron flux of ~ 1014 n /cm2 s. Thereafter, the targets were cooled for different time intervals from the end of irradiation (3 to 75 days). Detection and identification of 99Mo and the cross-contaminant radionuclides introduced via thermal neutrons activation, fast neutrons side nuclear reactions and / or parent-daughter nuclear decay by gamma-ray spectroscopy. Radiometeric analysis of

MoO3, Al and (MoO3 + Al) targets indicated the presence of different contaminating radionuclides in the irradiated (MoO3 and Al) target 134 141 51 152 92m 95 95 65 124 materials such as Cs Ce, Cr, Eu, Nb, Zr / Nb, Zn, Sb and 60 141 141 152 ,, 60 124 Co from the irradiated MoO3 powder and Ce, Ce, Eu Co, Sb, 65Zn, 140 La, 95Zr, 181Hf, 175Hf, 59Fe, 46Sc and 54Mn from the irradiated Al foil. The dissolution of the MoO3 target wrapped with Al foil (containing 1.37 mg Fe) in alkali solution were examined as a function of volume and concentration of NaOH. The dissolution of irradiated targets in 30 ml 5 M NaOH solution is accomplished via an exothermic reaction in ~ 15 min with the evolution of molecular hydrogen. Oxidation with 0.5 ml H2O2 (10 % w/ v) of the soluble reaction black products was carried out, thereafter. The 99Mo-molybdate solutes were centrifuged and filtrated from the formed Fe (III) minerals precipitate, as chemical impurity of the 1.37 mg Fe introduced from the 0.6 g Al foil. Gamma-ray spectrometery shows that in- situ formed Fe (III) precipitate achieved complete elimination of ~ 100 % *Ln (140La, 141Ce and 152Eu), 92mNb and 54Mn radionuclides, partial elimination of ~ 35, 68, 50 and 80 % 51Cr, 59Fe, 46Sc and 60Co radionuclides 99 from the MoO3 (VI) solute, respectively. On the other hand,

244 radiocontaminants of 95Zr, 65Zn, 181&175Hf and 124Sb radionuclides showed nil elimination onto the surface of the formed Fe (III) precipitate, due to high amphoteric solubility in strong alkaline media. Competetion of 134Cs and 86Rb cations with macro-concentration of Na+ cation in the bulk solution favored Na+ adsorption via cation-exchange reaction onto the formed Fe (III) oxide minerals such as hematite, maghemite. The formed 99 2- Fe (III) minerals slightly retain ~ 0.97 % of the MoO4 anions via an inclusion mechanism within the aqueous phase surrounding the formed Fe (III) minerals fine particles. Recovery yield of 100 % of the retained 99 2- MoO4 anions was achieved by washing the formed Fe (III) precipitate twice with 5 ml 0.5 M NaOH solution together with the release of ≤ 0.1918 and 0.318 % of the retained 60Co and 92mNb radionuclides. Assessment of the elimination of 59Fe radionuclide together with the 99 2- 99 other cross-contaminants and retention of the MoO4 anions from Mo- molybdate (VI) solutes was conducted as a function of Fe, NaOH and H2O2 concentrations in the reaction mixture solution. Adding different mg amounts of FeCl3.6H2O to the irradiated targets before dissolution with 34 ml 5 M NaOH solution followed by adding 0.5 ml H2O2 (10 % w/ v) as an oxidant. The obtained data showed that the elimination % of 59Fe, 51Cr, 46Sc and 60Co were increased with increasing the total Fe concentration in solution from 0.721 to 7.8 x 10-3 M Fe. The radionuclides of 95Zr, 65Zn, 181&175Hf and 124Sb start to show increasing elimination behavior with increasing the total initial Fe concentration in solutions. 95Nb (decay product of 95Zr) showed complete elimination with increasing the total Fe 99 2- fed dose. The retention of MoO4 anions, also, increased with increasing the amount of fed Fe doses up to ~ 3.99 x 10-3 M Fe where a plateau was obtained, thereafter. Effect of NaOH concentration on elimination of the contaminants and retention % of 99Mo radionuclide from the 99Mo-molybdate solutes

245 containing constant total fed dose of Fe (7.58 mg Fe as 3.99 x 10-3 M Fe) oxidized with constant volume of 0.5 ml H2O2 (10 w/ v) was conducted by concentrated HNO3 acid treatment of the solutes to 4.0, 2.0, 1.0 and 0.5 M NaOH. The data indicated that elimination % of 59Fe, 51Cr, 46Sc and 60Co 95Zr, 65Zn, 181&175Hf and 124Sb increased with decreasing the NaOH 99 2- concentration in solution from 4 to 0.5 M. Retention of MoO4 anions 99 2- sharply increased from ~ 0.933 to ~ % 5.76 % MoO4 with decreasing the NaOH concentration from 4.0 to 1.0 M NaOH followed with a reversible decrease to 1.53 % 99Mo at the lower concentration of 0.5 M NaOH. The irradiated targets solutes in a total volume of 34 ml 4 M NaOH containing 7.58 mg Fe oxidized with different volumes of 0.25, 0.5 and 1.0 59 ml H2O2 (10 % w/v) solution showed decreasing elimination % of Fe radionuclide with increasing the volume of H2O2 in solution from 0.25 to 1.0 ml. The elimination behavior of 59Fe radionuclide was more or less similar to the decreasing elimination behavior of 46Sc, 60Co 95Zr/95Nb, 65Zn and 181&175Hf radionuclides with increasing the oxidant concentration. 51Cr and 124Sb radionuclides were affected by redox behavior in poor and 2- rich oxidant media. Retention of MoO4 was increased from higher than from lower H2O2 concentration media. Complete purification from *Ln (140La, 141Ce and 152Eu), 92mNb and 54Mn radionuclides was not affected by variation of Fe, NaOH or H2O2 concentrations in solutions. Due to competition between the bulk concentration of Na+ cations, 134Cs and 86Rb didn’t show any elimination behavior from the 99Mo-molybdate (VI) solutes by variation of Fe, NaOH and H2O2 concentrations in solutions.

The effect of Fe, NaOH and H2O2 concentrations on the contribution profile of Fe in the aqueous phase (as soluble / dispersed Fe species) were systematically investigated to assess the role of each factor on the transformation reactions of the formed F(III) minerals and their purification

246 behavior. The homogeneous distribution and isotopic dilution of 59Fe radionuclide between the liquid and solid phases helped to a great extent in assessment of the formed precipitates and discussion of the sorption / desorption behavior onto Fe (III) minerals. Raman spectroscopy transformation investigations of the formed Fe (III) iron precipitates from concentrated 4 M NaOH media in presence and absence of 1.0 g MoO3 as a function of Fe, H2O2 and alkali / NaNO3 concentrations in the reaction 2- mixture explored that in absence of MoO4 anions: (i) at higher oxidant concentrations Fe (III) oxide minerals such as hematites and maghemites together with ferrihydrites predominate (ii) at oxidant concentrations just sufficient for oxidation of Fe (II) to Fe (III) the oxyhydroxides: goethite mineral together with lepidocrocite in the presence of Fe (II) species in solution are the predominating transformation products, and (iii) at small

H2O2 / Fe (II) molar ratios (i.e, Fe (III) / Fe (II)) the mixed oxide magnetite

(Fe3O4) becomes one of the main final products. Generally, in the presence 2- of MoO4 anions, the oxyhydroxide character predominates as the final transformations products with preferential transformations into goethite together with lepidocrocite and / or ferrihydrite. 99 2- Desorption of the retained MoO4 was investigated as a function of 99 2 total Fe dose in solution and type of eluent. The desorption of MoO4 anions from the formed Fe (III) minerals decreased with increasing the total Fe fed dose in the range from 1.37 to 11.71 mg Fe in the reaction mixture solution (34 ml ~ 4 M NaOH + 0.5 ml H2O2) via conversion of the sorption behavior from mainly external inclusion to inclusion and occlusion adsorptions. The release of 92mNb and 60Co decreased, also, with increasing 99 2- the total Fe fed dose. Recovery of the MoO4 from the surface of Fe (III) minerals was achieved with 0.5 M NaOH solution by partition distribution between the mobile phase and solute surrounding the sorbent particles. Use of 2 x 5 ml fractions of distilled water, as an eluent, the pH value of the

247 reactive eluates were 9.5 and 6 in the first and second fractions with the release of more 92mNb and 60Co radionuclides, respectively. The 99Mo-molybdate supernatant after Fe (III) precipitation was further purified by sequential precipitation of Al (OH)3 matrices at pH values of 9.5 and 5. The supernatant, after separation of Fe (III) minerals was acidified by addition of nitric acid to pH 9.5. Complete elimination % of 59Fe, 60Co, 46Sc, 95Zr/95Nb, 65Zn, 124Sb and 181&175Hf radionuclides from the 99Mo-molybdate (VI) supernatant was achieved via co-precipitation and / 134 or adsorption onto the formed Al(OH)3 precipitate. Nil elimination of Cs and 86Rb together with 5 and 2 % 51Cr and 60Co radionuclides remained in the supernatant after precipitation of Al (OH)3. About 85 % of the initial 99 2- MoO4 anions were passed to the supernatant solution after separation of 99 2- the formed Al (OH)3 precipitate. 13.8 % of the initial MoO4 anions were recovered by washing the formed Al (OH)3 precipitate 4 times each with 8 99 ml NaNO3 solution of pH 9.5. About 0.23 % of the initial Mo-molybdate

(VI) was retained onto the surface of the formed Al (OH)3 precipitate with 99 uptake capacity of ~ 1.35 mg Mo / g Al2O3. Alternatively, Mo-molybdate

(VI) supernatants were acidified with concentrated HNO3 to pH 5. The 99 2- recovery of retained MoO4 was investigated by washing individual Al

(OH)3 precipitates with NaNO3 solutions of pH 9.5 and 5, respectively. The

Al (OH)3 precipitates formed at pH 5 verified high retention value of 99 2- MoO4 anions. Uptake capacities were found to be ~ 167 and 407 mg Mo

/ g Al2O3 precipitates washed with (4x 8 ml 3.5 M NaNO3) solutions of pH 9.5 and 5, respectively. The remaining cross-contaminating radionuclides: 5 and 2 % 51Cr and 60Co, traces of 124Sb and 100 % 86Rb and 134 C s were mainly eliminated by passing the final supernatant of the formed Al (OH)3 precipitate at p H 9.5 onto a small KNHCF chromatographic column.

248 The purified 99Mo-molybdate (VI) column eluates were precipitated in the form of a zirconium molybdate gel matrix at pH 4.7, the precipitate was washed, conditioned and packed as a chromatographic column of 99Mo / 99mTc generator. The elution yield of the generated 99mTc radionuclide with 10 ml 0.9 % NaCl solution was found to be ≥ 82.7 ± 0.4 with high and reproducible radionuclidic, chemical and radiochemical purity suitable for use in the nuclear medicine.

249

References

Abe M. and Hayash K. (1983), Solvent Extr. Ion Exch. 1, 97.

Abou El-Enein M. M. Sc., Thesis (1997) Faculty of Engineering, Cairo University, Cairo, Egypt.

Abou-Mesalam M. M. M. Sc. Thesis (1993) Faculty of Science, Ain Shams University, Egypt.

Abraskine S., Heller G., Grossman V., Shafferman, V. and Davis, M. (1978) Int. J. Appl. Radiat. Isot. 29, 359.

Adamson A. W. (1960), J. Physical Chemistry of Surface, 461 Inter sciences, New York.

Agasyan P. K. (1980) Qualitative Semi Micro Analysis, English Translation, Mir Publisher, Moscow, 2nd ed.

Aggarwal R. C. (1987), Modern Inorganic Chemistry, Kitab Mahal, Allahabad, India.

Alam T., and Kamaluddin (2000), J. Colloids and Surf. 162, 89.

Ali H. F., Mechail F. M., Misak N. Z. and Ibrahim G. S (1991), Bull Soc. Chem. Fr. 128,

Ali S. A and Ache H.J. (1987), Radiochim. Acta. 45, 65.

Ali S. A., and Ache, H. J. (1986), Production Technology of Fission 99Mo, IAEA Ar-131/ 3.

Ali S. A., Konard J., and Ache H. J. (1982), Peoc. of the Int. Symp. Applied Technology of Ionizing Radiation, Riodah.

Amin M. M Sc. (2003) Thesis, Institute of Environmental Studies and Research, Ain Shams University, Cairo, Egypt.

Amphlete C. B. (1964) Inorganic Ion Exchangers, Elsiever, Amstrdame.

Appelo C. A. J., Van der Weiden M. J. J., Tournassat, C. and Charlet L., (2002), Environm. Sci. Techn.V. 36, p. 3096.

Appelo C. A. J. and Postma D. (2005), Geochemistry Groundwater and Pollution, 2nd ed Balkema Publ, p 649.

250 Arif M., Zaidi J. H. and Qureshi I. H., (1996), Radiochim. Acta 75, p 175.

Arino, H., and Kramer, H. H., Int, J. Appl. Radiat. and Isot, 26, 30 (1975).

Aveston J., Anacker E. W., and Johanson J. S., (1964), J. Inorg. Nucl. Chem. 3, 735.

Aycik GA., (2009) New techniques for the detection of nuclear and radioactive agents, Springer, Dordrecht.

Baetsle L. H. Van Deyck, D. and Huys, D., J. (1965), J. Inorg. Nucl. Chem.,27, 683.

Bate L. C., and Leddicotte G. W., (1960) The Radiochemistry of Cobalt, Nuclear Science Series, Subcommittee on Radiochemistry, Natural Academy of Science, Natural Research Council, NAS-NS 3041, USA.

Belleville P., Jolivr J. P., Tronc E, and Livage J., (1992), J. Colloid Interface Sci. 150, 453.

Belous A. G., Pashkava E.V., Elshanskii V.A. and Ivanitiskii V. P., (2000), Inorg. Mater. 36, 34

Benefield L. D., Judkins. J. F. and Weand B. L., (1982), Process chemistry for water and wastewater treatment (Prentice – Hall New jersey).

Benjamin M. M., (1982) Adsorption and Surface Precipitation of Metals on Amorphous Iron Oxyhydraoxide.

Bennett B. A., Shahbandeh M.R. and Streat M., (1982), J. Chem. Technol. Biotechnol. 32, 58886.

Blumenthal W. B., (1958) The Chemical Behavior of Zirconium, D. Van Nostrand Company, Int. Canada, 164.

Bodenstedt E., Matthias E. and Karner H. J. Z., (1964), Phys. 153, 423.

Boeglin A.F., Bockhan J.A, Choyson L., Lemon, D.M., Stoops C. E., ( 1961),The nitric acid dissolution of Al-U alloy in flooded continuous dissolver USAEC Report IDO 14321.

Bonin P. M. L., Odziemkawski M. S. and Gillham G. W., (2000), Corros. Sci., 42, 1921.

b Botros N ., (1996), Arab J. Nucl. Sci. Appl., 29, (4), 251.

Botros N a., (1996), Arab J. Nucl. Sci. Appl., 39,(4) , 255. 251 Boucherit N., Hugot-Le Goff, A. and Joiret S., (1991), Corros. Sci. 32, 497.

Bourrie G. T., Troland F. Genin J. M. R., Jarferzic A., Maitre V., and Abdelmoula M. (1999) Iron control by equilibria between hydroxide hydroxyl green rust and solutions in hydromorphic soils, Geochim. Cosmochim. Acta., 63, 3417.

Boyd R. E., Hetherington E. L. R., (1980), Int. J. Appl. Radiat. Isot. 31, 250.

Boyd R. E., (1997), Int. J. Appl. Radiat. Isot. 48 (8), 1027.

Boyd R. E., (1993), Newsleter-Australian and New-Zeland Society of Nuclear Medicine, 24 (2), 14.

Boyd, R. E., Radiochim. Acta, 30, 123 (1982).

Boyd R. E., (1987), Radiochim. Acta. 41, 56.

Brown P., Shying M. E. and Shylva, R.N., (1986), Australian Atomic Energy Commission Unpuplished Data.,.

Bulbulian S. and Sarantin H., (1966), Isotopentechnik und Chemie, 3, 118.

Burck J, Ache SA, Ache HJ., (1988), Solvent Extr. Ion Exch.. 6, 937.

Burrows T. W., February (1988), Nuclear Data in the MIRD format, Brookhaven National Laboratory, USA, Report BNL-NCS-512-142,.

Caletka R., Konecny C., (1976) J. Radioanal. Chem., 30,119.

Capaccio R. S. (1996), Metals Control Industrial Waste water, 21.

Carley-Macauly K. W., Gutman R. G., Hooper E. W., Jenkins J. A., Turner A. D., Wace P. F., Chauvent P. Chauchon J. P. and Dippel T., (1981) Harwood Academic Puplisher, Commission of the Europium communities Brussels and Luxembourg.

Carlson L. and Schwertmann U. (1980), Natural occurring of feroxyhite (δ- FeOOH). Clays Clay Miner. 28, 272.

Carvatho F. M. S. and Abrao A., (1997), J. Radioanal. and Nucl. Chem., 218, (2), 259.

Ceranic T.S., Trejuovic D. and Admaric R. Z. (1978), Naturforsch. 33 , 99.

Charles F., Baes Jr., Robert E., ( 1976), ""Hydrolysis of Cations". Mesmer and Oak Ridge National Laboratory. Oak Ridge, Tennessee 252 Chukhrov F. V., Zvtagin B. B., Gorshkov A. I., Yermilova L. P, Korovushkin V. V., Rudnitskava Ye. S. and Yakuvovskaya N. Yu., (1977) Feroxyhyte, a new modification of FeOOH. Int. Geol. Rev. 19, 873.

Choudhury S., Bagkar N., Dey GK., Subramanian H., Yakhmi JV., (2002) Langmuir 18,7409.

Chu S.Y. F., Ekstrom L. P., and Firestone R. B. (1999), The Lund/LBNL Nuclear Data Search, Version 2.0, , http:// nucleardata. nuclearr. lu. se/nuclear data / toi / index. asp.

Clifford D. (1999) "Ion exchange and Inorganic Adsorption. In: Letterman [ed]. Water Quality and Treatment. 5th ed. American Water Works Association, Mc Graw Hill. New York.

Cohen I. M., Magnavacca C., and Baro G. B., (1983), Radiochem. Acta 34, 157.

Cordfunk K. H. P., (1969), " The Chemistry of Uranium Including its Application in Nuclear Technology" Elsevier Publishing Company, Amsterdam.

Cornell R. M. and Schwertmann U. (1996), The Iron Oxides: Structure, Properties, Reactions, Occurrence and Uses. VCH Verlagsgesell-schaft mbh. Weinheim.

Cotton, F. A., and Wilkinson, G., (1980) Advanced Inorganic Chemistry, 4th ed., Wiley. New York.

Cotton, F. A., and Wilkinson, G., (1979). Advanced Inorganic Chemistry, Wiley Eastern Ltd., New Delhi, 3rd ed..

Cotton, S. A., and Hart, F. A., (1975) "The heavy Transition Elements" Macmillan, London.

Criscenti J. and Sverjensky D. A., (2002), J. Colloid Interface Sci 253, 329.

D,Mov A. M., and Savostin A. P.: (1968), Analytical Chemistry of Gallium (in Russiar.), Nauka. Moscow.

Damm J. H., Hardacreb C., Kalina R. M. and Walsha K. P., (2002), Water Res., 36, 3638.

Davarpanah M. R., Nosrati S. A., Fazlali M. Boudani M. K., Khoshhosn H. and Maragheh M. G, (2009), Appl. Radiat. Isot., 67, 1796.

De Faria D.L.A., Silva S.V. and De Oliviera M.T. (1997), J. Raman Spectrosc..28, 873.

253 De Marco M.J., Sen Gupta A.K., Greenleaf J.E,. (2003), Arsenic removal using a polymeric / inorganic hybrid sorbent. Water Res. 37, 164.

Deryagin I. B. V., and Landau.L. D., (1941), Acta Physicochem, URSS. 14, 733.

Deutsch E. and Libson K., (1984), Comments Inorg. Chem., 3, 83.

Deutsch E., Heineman W. R., Zoddo J. P., Gilbert T. W. and Williams C. C., (1982), Int. J. Appl. Radiat. Isot., 33, 843.

Dey S., Goswami S. and Ghosh U. C, (2004), Water, Air, and Soil Pollution 158, 311.

Drew M. G. B., Michell P. C.H., and Pygall C. F., (1976), Journal of Chemical Society , Dalton, 1071.

Dűnnwald J. and Otto A. (1989), Corros. Sci.. 29, 1167.

Dzombak D. A. and Morel F. M.M., (1990), Surface Complexation Modeling: Hydrous Ferric Oxides. John Wiley & Sons, New York, 9.

Edward F. T. L. and Mechael Streat (1983), J. Chem. Tech. Biotechnol. 33 A, 80.

Egan G. F., Oarkville V. I. C., Jamieson C. H., and Logumas Solar, M. C., (1994), Newsletter-Australian and New-Zeland Society of Nuclear Medicine, 25 (1), 25.

Ehmann W. D.,Vance D. E., (1991), "Radiochemistry and Nuclear Methods of Analysis" Jhon Wiley and Sons, Inc., New York.

a El-Absy M.A ., El-Garhy M. A., Faseih T. W, El-Amir M. A., Ramadan H. E and El-Shahat M. F., (2011), (under publication).

b El-Absy M. A ., Mostafa M., Amin M., El-Amir M. A., ( 2011), (under publication).

El-Absy M. A., Abou El- Enein M., Raieh M., and Ali H. F., (1997), J. Radioanal. Nucl. Chem.., 218 (2), p 157.

El-Absy M. A., and El-Bayoumy S., (1990), Isotopenpraxis, 2, 60..

El-Absy M. A., and El-Naggar I. M., and Audah A. I., (1993), J. Radioanal. Nucl. Chem.., 173 (1), 185.

El-Absy M. A., and El-Naggar I. M., and Audah A. I., (1994), J. Radioanal. Nucl. Chem.., 183 (2), 339. 254 El-Absy M. A., El-Amir M. A., Mostafa M., and Abdel Fattah A. A., Ali H., (2005), J. Radioanal. Nucl. Chem., 266 (2), 2 95.

El-Absy M. A., El-Said H. and Mahmoud W. H. Cairo,14-19 /12 (2002) Sixth Arab Conference on the Peaceful Uses of Atomic Energy

El-Absy M. A., (1991), Radiochim. Acta, 55, 33.

El-Asrag H., Ph.D. (1978), Thesis, Ph. D., Faculty of Pharmacy, Cairo University, Egypt .

El-Bayoumy S., (1972), M. Sc. Thesis, Faculty of Science. Cairo University Egypt.

El-Garhy M, El-Bayoumy S, Abdullah E., (1971), Starhlentherapie 142,376.

El-Garhy M, Shehata MKK, EL-Bayoumy S., (1972), J. Radioan. Chem. 11,175.

El-Garhy M., Moustafa, Z., and Mikheev, N. B., (1966), Atompraxis, 12, 93.

El-Kholy S. H. M., (1998), M Sc., Thesis Faculty of Science, Ain Shams University, Cairo, Egypt.

Ellenburg E.J., and MacCow, J., (1968), .J. Anal. Letters, 1, 697

Esmadi F. and Simon J., (1995), J. Colloidal Surfaces A: Phisicochem.. Eng. Aspects 104, 265.

Etherington H., (1958), "Nuclear Engineering Handbook", McGraw-Hill book Company, Inc., New York, 1st ed..

Evans J. V, Pilli L., Motthews R. W. and Hall G, Jul. 21, (1981), USA patent 4, 280. 053.

Evans J. V., and Shying M. E., (1984), Zirconium Molybdate Gel Generators for 99mTc, Rep. (AAEC/E-599, ISBN 0842 5980), Australian Atomic Energy Commission

Evans J. V., Moore P. M., Shying M. E., and Sodeau, (1987), Appl. Radiat. Isot., 38, 19.

Evans J. V., Moore P. M., Shying M. E., and Sodeau J. M., ( 1982), A New Generator for 99mTc, World Congress of Nuclear Medicine and biology, Press, 2, 1592.

Farely K. J.,Dzombak D. A., Morel, F. M. M., (1985), J. Colloidal Interface Sci. 106, 226. 255 Fettknecht W, Z. (1959), Electrochem. 63, 34.

Finck R., and Mattason S., (1976), Int. J. Nucl. Med. Biol. 3, 89.

Flynn. C. M. (1984), Chem. Rev. 84, 31.

Foster D. L., Savolainen J. E., and Wymer R. G., (1955), "Nuclear Fuel Dissolution", Proceeding of the International Conference on the Peaceful Uses of Attomic Energy, 9, 546, Geneva, August.

Gadde R. R. and H. A. Laitinen, (1974), “Studies of Heavy Metal Adsorption by Hydrous Iron and Manganese Oxides.” Anal. Chem., 46, (13), 2022.

Galy G., (1991), Journal Article 19 (1), 11.

Ganzerli Volentini. M. T, Stella R. and Genava N, (1987), J. Appl. Radiat. Isot., 38, 709.

Gayer K. H. and Garrett A. B., Amer J. (1950), J. Chem. Soc. 72. 3921.

Gellings P. J., Phys Z. (1967), J. Chem. 54,296.

Gerlit J. B., Proc. (1956), Int. Conf. Peaceful Uses of Atomic Energy 7, 145.

Glasstone S., (1955), "Principles of Nuclear Reactor Engene ering", D.Van Mostrand Company, Inc., Toronto.

Gordon S. and Schreyer J. M., ( 1951), J. Anal. Chem. 23, 831.

Gordon S. and Schreyer J. M., (1955), J. Anal. Chem, 44, 95.

Goubard F., Tabuteau A ., (2002), J. Solid State Chem. 167,34.

Greenwood N. N., Earnshaw A., (1998), Chemistry of the elements, 2nd ed. Butterworth Hienemann, Oxford.

GreenWood N, N., and Earanshow , A., (1984), Chemistry of Elements, Pergamon Press Itd., 1st ed.,.

Gregory J. and Düan. J. (2001),. " Hydrolyzing metal salts as coagulants" Pure Appl. Chem. 73, (12), 2017.

Griffith H. J., Knapp F. F., Callahan A. P., Chang C. H, Hansen H. J. and Goldengerg, D. M., (1991), J. Cancer Research., 15, 4594.

Griffith H. J., Goldengerg, D. M., Jones A. L., and Hansen H. J., (1992), J. Bioconjugate Chem., 391. 256 Haas PA., (1993), Sci Technol 28,2479.

Hafelli V., Tiefenauer L., X., Chubriger P. A., and Weder H. G., (1991), J. Nucl. Med. Biol., 18, 449.

Hanne D, Postma P. Rasmus and Larsen, (2005), J. Geochemica et Cosmochemica Acta, 69, (16), 3967.

Hansel C. M, Berner S. G, Neiss. J, Dohealkova. A, Kokkadapu R. and Fendof. (2003), Geochim. Cosmochim. Acta, 67, 2977.

He Y. T. and Traina S. J, (2007), J. Clay Minerals., 42, (1), 13.

He-Hun Jang, Brian, Dempsey A. Catchen, L., William, D and Burgos, (2003), J. Colloidal and Surfaces A: Phisicochem. Eng. Aspects 221, 55.

Hering J. G and Stumm W, (1990), Oxidation and reductive dissolution of minerals in mineral water interface geochemistry feds, J. Mineralogical Society of Amer.,p 427.

Holm H. R., (1987), Chem. Rev., 87, 1401.

Huys D, Baetsle L. H. J. (1964), Inorg. Nucl. Chem. 26:1329.

Inoue Y., Munemori M., (1980), Bull. Chem. Soc. Jpn., 53, 926.

International Atomic Energy Agency., (2003), " Manual for Reactor Produced Radioisotopes", IAEA-TECDOC-1340.

International Atomic Energy Agency, (1989), "Fission Molybdenum for Medical Use", IAEA,-TECDOC-515.

International Atomic Energy Agency, (1971), "Radioisotope Production and Quality Control", Technical Report Series No, 128, International Atomic Energy Agency, Vienna, IAEA.

International Atomic Energy Agency, (1995), Alternative Technologies for 99mTc Generators, Final Rep. of Coordinated Research Programme, IAEA- TECDOC-582.

International Atomic Energy Agency, (1984), Technical Report Series No, 236, IAEA, Vienna.

International Atomic Energy Agency, (1968), Technical Report Series No, 89, p, 80 IAEA, Vienna.

257 Ishikawa, T. Nitta, S. and Kondo, S. J. (1986), Chem. Soc. Farad. Trans. I82, 2401.

Ismail I M, (1994), MSc. Thesis Separation of Cesium and Cobalt from Contaminated Waste Waters Using Nickel Hexacyanoferrae Complexes., MSc. Thesis Faculty of Engineering Cairo University..

Ismail M, El-Sourougy, M. R., El-Moneim N., and, Ali H.F., (2002), Solvent Extr. Ion Exch. 20,589.

Ismail M, El-Sourougy M. R., Abdel Moneim N. and Ali H. F. (1998), J. Radioanal. Nucl. Chem. 237,97.

Iyer S. P., Narasimhan D. V. S., Singh L. N., and Patel R. R., (1992), Proc. of Nucl. Radiochem. Symp., Andhra Universty, Visbakapatnam, 325 .

Jackson T. W., Kojima M., and Lambrecht R. M., (1992), Aust. J. Chem., 46, 1093.

Jang J. H, Dempsy B. A, Calcen G. L and Burgos W . D, (2003), Effect of 2- Zn(II), Cu(II), Mn(II), Fe(II), NO3 or SO4 at pH 6.5 and 8.5 on transformation of hydrous ferric oxides (HFO) as ivedenced by Mossbauer spectroscopy, J. Colloidal. Surf. Acta. Phisicalchem. Eng. Aspect. 221, 55.

Jeon B. H, Dempsey B. A and Burgos. W. D, (2003), Kinetics and mechanism for reaction of Fe(II) with iron (III) oxides, Environ. Sci.Technol. 31, 3307.

Jeon B. H, Dempsey B. A, Burgos W. D and Richard R. A, (2001), Reactions of ferrous iron with Hematite. Colloidal. Surf. Acta. Phisicalchem. Eng. Aspect. 121, 41.

Johanston R. and Heijnen H. (2001), "Safe Water Technology for Arsenic Removal" In: Ahmed, M.F. et al. [Eds]. Technology for Arsenic Removal from Drinking Water, Bangladesh University of Engineering and Technology, Dhaka. Bangladesh.

Jhone Emsely The Elements, 2nd ed Oxford (1991).

Joliver J. P Belleville P, Tronc E, and Livage J. (1992), Infeluence of Fe(II) on the formation of spinal iron oxide in alkaline medium Clays. Clay. Menerals. 40, 531.

Joseph Steigman. (1982), Int. J. Appl. Radiat. Iso. 33, 829.

Kahani S. A and Jafari M., (2009), Journal of Magnetism and Magnetic Materials, 321, Issue 13, 1951.

258 Kalinskaya T.V., Krasotkin I.S. and Lobanova L.B., (1979), J. Appl Chem USSR 520.

Kandori K. Uchida, S. Kataoka, A and Ishikawa, T. Mater. (1992), J. Sci, 27. 719.

Kaneko. K and Katsura. T, (1979), J. Bull. Chem. Soc. Jpn., 52, 747.

Kassler K. G. and Meggers W .F., (1950), Phys. Rev. 80, 905.

Katcoff S., (1966), Nucleonic, 18, 11.

Kathrin Ann. L., Stephan J., Bemhard W., and Annette C. (2006), J. Environmental Science & Technology 40 (8) 2565.

Kawamora, S., Kuraku, H. and Kurotaki, K. (1970), J. Anal. Chem. Acta, 49, 317.

Keny A.D. and Sen Gupta, A.K. (2001), Synthesis and characterization of hybrid inorganic sorbents for heavy metals removal. In: Mannsky, J.A, Sen Gupta, A.K., Morcus, Y. (Eds), Ion Exchange and Solvent Extraction. Marcel Dekker, New York.

Kieser J.T. Brown C.W. and Heidersbach R.H. (1983), J. Corros Sci 23, 251

Kiyama M and Takada T, (1974), J. Bull. Chem. Soc. Japa. 45, 1923.

Kiyama M, (1969), ibid, 47, 607.

Klofutar C., Stular V. and Krasovee F., (1967), J. Anal. Chem., 214, 27.

Klyama. M, (1974), J. Bull. Chem. Soc. Jpn., 47, 1646.

Knapp F.F. Jr., and Mirzadeh S., (1994), Eur. J. Nucl. Med., 21 (10), 1151.

Kolthoff I. M., (1966), "Threatise on Analytical Chemistry" Interscience puplished, New York., 6,(2), 411.

Kostka J. E, and Luther III G. W, (1994), Partitioning and speciation of solid phase iron in saltimarsh sediments. Geochem. Cosmocheim. Acta. 58, 1701.

Kaurim V., Rais, J., and Million, B. (1964), J., Inorg. Nucl. Chem., 26, 1111.

Kozlova A. P., Sugiyama S. Kozlov A. I., Asakura K. and Iwasawa Y. (1998), J. Catalysis 176, 426.

Kralove H., Cifka J. and Kopecky, P., (1980), Interregional Training Cours on the Preparation and Control of Radiopharmaceuticals IAEA. 259 Krause H., (1984), "Management of Radioactive Wastes from Nuclear Plants", IAE-CAN-43, 180.

Kulyukhin S.A., Krasavina EP, Mizina LV, Rumer IA, Tanashchuk NV, Konovalova NA, Murachev AS and Sergeev VV., (2005), Radio-chem (Translated from Radiokhimiya) 47, 528.

Larsen O. and Postima D. (2001), Kinetics of reductive bulk dissolution of lepidocrocite, ferrihydrite and goethite. Geochem. Cosmocheim. Acta., 65, Issue 9, 1367.

Lavi N., and Fishion Z., (1973), Radiochem. Acta, 20, 39.

Lee, J. D., (1977), " Concise Inorganic Chemistry", ELBS, 3rd ed..

Lee, J. D., (1991), "Concise Inorganic Chemistry", ELBS, with Champan and Hall, Singapore, 4th ed..

Lehto J., Harjula R., (1987), J. Solvent Extr. Ion. Exch. 5,343.

Lehto J, Harjula R., and Wollace, (1989), J. Radioanal. Nucl. Chem. Articles, 2, 297.

Lehto J, Haukka S., (1990), J. Thermochim Acta 160,343.

Leyvajulieta Ana G. Patricia M., Smichwski and Cicerone D. (2001), Enviromental Science & Technology, 35, 3669.

Lewis, R.E, ( 1971), J. Appl., Radiat. Isot. 22, 603.

Liang Q., (1996), "Development and Optimization of W-88/Re-188 and Mo-99 / Tc-99 Gel Radioisotope generators", Ph.D. Thesis, Missouri University, Columbia, USA.

Lide, D. R., .(1993), Handbook of Chemistry and physics, CRC Press, Boca Raton, Araber London, Tokyo, 73rd ed.

Lieser, K. H., Bonnevie-Svendsen, M., (1975), Sorption and Filtration Methods for Gas and Water Purification. Nato. Advanced Study Institutes Series. Noordhoff.

Liger E., Charlet L. and Cappellen P.V. (1999), J. Geochimica et Cosmochimica Acta 63, 2939.

Ligodi M. A . and Waal D. (2008).J. of Dyes and Pigments. 78, Issue 2, 177.

260 Lisken H., Worlfle R., Widera. R and Qaim. S. M., (2001), Int. J. Appl. Radiat. 65, 1367.

Liskien H., Wolfle, R., Wiedera, R., and Qaim, S. M., (1990), Int. J. Appl. Radiat. Isot. Vol. 41, (1), p 83.

Loewenschuss H., (1982), j. Radioactive Waste Manage., 2, 227.

Loos R., Proc. (1963), Seminar Vienna (1962) IAEA, Vienna.

Loos-Neskovic C, Ayrault S, Badillo V, Jimenez B, Garnier E, Fedoroff, M, Jones DJ, Merinov B., (2004), J Solid State Chem 177,1817.

Loos-Neskovic C., Fedoroff M., Revel G. J., (1976), Radioanal Chem 30, 533.

Loos-Neskovic C, Fedoroff M., (1989), J. Solv Extr Ion Exch 7,131.

Loureiro J. M, Kartel M. T., (2006), Combined and Hybrid Adsorption. Springer, Dordrecht

Mackay A. L., (1960), Minerals Mag. 32, 545.

Mackay A. L, (1961), Reactivity of Solids (Eds. J. H. De Boer et al), 571. Elsevier, Amsterdam.

Maki Y. and Murakami Y., Nipppon N., (1971), Kagaku Zasshi, 92, 1211.

Malik WU, Srivastava SK, Singh R. P. and Kumar S., (1977), J Radio-anal Chem. 36,469.

Manceau A, and Drits Y. A, (1993), Local structure of ferrihydrite and feroxyhite by EXAFS spectroscopy. Clay. Minerals, 28, 165

Mani R. S., and Narasimhan D. V. S., (1973), IAEA, Vienna, 135.

Manzione M. M., D. T. Merrill M., Mclean W. Chow and D. Drummonds (1994), "Captivating Metals Removal" Industrial Wastewater, July/August, p. 19.

Maoliang L., (1994), "Production of Gel-Type Tc-99m Generator for Nuclear Medicine", Lecture of IAEA Expert Mission for Brazil, Sao Paolo, Brazil (1996).

Mark Occhionero Richard Adams, Kevin Fenct and Robert A Hay" (1999). Ceramics Process Systems, Crop. Chrtley MA 02712. "Aluminum Silicate Carbide (AlSiC) for Advanced Microelectronic Packages.

Mark E., Holand. Edward D., William, R., Heineman and E laine M artin., (1986), J. Appl. Radiat. Iso., 37,(2), 165. 261 McAfee J.G. and Subramanian, G. (1994). J. N ucl. Medi.; 25 (1), 25

McAfee J.G. and Subramanian G. (1991), J. Nucl. Medi.; 32, 2126.

Medicus H., Maeder D and Schneider H. (1951), Helv. Phys. Acta, 24, 72.

Melichar F., (1990), Isotopenpraxis, 26, (11), 540.

Meloni S., and Brandone, A., (1968), Int. J. Appl. Radiat. Isot. 19, 194.

Midecin", (1996), Lecture of IAEA Expert Mission for Brazil, Sao Paulo.

Miller D. A., Sun S. S., Yi J. H.., (1992), J. Radioanal Nucl Chem.160,467.

Milyutin V. V., Gelis V. M., and Dzekum. E. G., (1995), Radiochemistry, 37, 85.

Mimura H, Kimura M, Akiba K and Onodera Y., (1998), J Nucl. Sci Technol. 35,392.

Mimura H, Kimura M. and Akiba K., (1999), J. Nucl Sci Technol 34,17.

Mimura H, Lehto J and Harjula R., (1997), J Nucl Sci Technol 34,582

Mirzadeh S., Knopp F. F. Jr. (1996), J. Radio. Anal. Nucl. Chm, Art., 203, 47.

Misawa. T, (1973), Corrs. Sci. 13, 659.

Misawa T, Hashimoto K and Shimodaira. S, (1974), J. Corr. Sci., 14, 131.

Misawa. T, Kyuno. W, Suetaka and Shimodaira. S, .(1971), J. Corros. Sci. 11, 35.

Misawa.T, Kyuno, T, Suetaka, W and Shimodaira. S, , (1969), J. Japan. Inst. Metals, 33, 1149.

Mitchell P. C. H., (1999), "Data Base of Molybdenum in the Enviromen" International Molybdenum Association (IMOA), London, Update-1.

Mitchell P. C. H., (1990), "Ulmann, s Encyclopedia of Industrial Chemistry", A16, 668, Chap. 7, p/675, Verlagsgesellschaft, Weinheim, Germany, 5th ed.

Molinski V. I., (1982), Int. J. Appl. Radiat. Isot., 33, 811.

Mollah S, Begum A, Rahman M. M., (1998 ), J. Radioanal Nucl. Chem 229, 187.

Monika H., (2009). Geophys. J. Int. 177, 941.

262 Monroy Guzman F., Dias Archundia L. V., Hermades - Cortes S., J. Braz. (2008), Chem. Soc.; 19, 380.

Monroy Guzman F., Dias Archundia L. V., Ramirez A. C., (2003), J. Appl. Radiat. Isot.; 59, 27.

Monroy Guzman F., Romero O. C., Velazquez H. D., (2007), J. Nucl. Radiochem. Sci.; 8, 11.

Moore P. M., Shying, M. E., Evans, J. V., and Sodeau, J. M., (1987), Int. J. Appl. Radiat. Isot. 38(1), 25.

Mostafa M., (2002), M Sc., Thesis Faculty of Science, Banha University, Egypt.

Mostafa M., (2006), PhD, Thesis Faculty of Science, Banha University, Egypt.

Mostafa M, El-Absy M. A., Amin M, El-Amir MA, and Farag, A. B. (2010), J. Radioanal. Nucl. Chem. 285, 579.

Motojma K. U S. 3 July, (1990), Patent No. 4, 938,895.

Munze, R. and Buger, R., (1987), J. Radiochem.Acta, 41, 97.

Munze, R. Hladik, O., Bernhard, G., Boessert, W. and Schwarzbach, P., (1984) J. Appl. Radiat. Isot. 35 (8), 749.

Munze, R., Mosaad, K., El-Bayoumi, S., and Hallaba, H., (1980), A.R.E.A.E.E. / Rep. – 235.

Murphy P. J., A. M. Posner and J. P. Quirk (1976), J. Colloid Interface Sci., 56, 270 (after Benjamin, 1983).

Mushtaq A., (2004), J. Radioanalytical and Nuclear Chemistry. Vol 262, (3),

Mushtaq A., Masoor, M. S., Karim, H. M. A., and Khan, M. A., (2004) J. Radioanal. Nucl. Chem., 147 (2), 257.

Mushtaq A., Tanveer Hussain BokkRI, Islam Ullah Khan., (2009), J. Radioanalytical and Nuclear Chemistry. 279 (1), 281.

Musić S., and Ristić M., (1988), J. Radioanalatical and Nuclear Chemistry, 120, ( 2), 289.

Musić S., (1986), J. Radioanalatical and Nuclear Chemistry, Articles, 100, (1), 185.

263 Music S., Gessner M and Wolf, R. H. H. (1979), J. Mikrochim. Acta [Wien], 1, 105.

Nakayama, E., Tokoro, H., Kuwamoto, T., and Fujinaga, T, (1981) J. Nature, 290.

Narasimhan D. V. S a., Vanaja, P., and Mani, R. S. (1984), J. Radioanal. Nucl. Chem. 85, 345.

Narasimhan, D. V. S b., Vanaja, P., and Mani, R. S. (1984), J. Radioanal. Nucl. Chem. 85, 163.

Näsman P. and Väyrynen, T., (1983), Eur. J. Nucl. Med., 8, 26.

Nauer G., Strecha, P., Brinda-Konopik, N. and Liptay, G. J., (1985), Therm. Anal. 30, 813.

Navasivayam C. and Ranganathan K.,(1995), " Removal of Cd (II) from Wastewater by Adsorption on "Waste" Fe(III)/Cr(III) Hydroxide." Water. Res., 29 ( 7) 1737.

NEA (Nuclear Energy Agency), Nuclear Science Community, (1997), "Actinide Separation Chemistry in Nuclear Waste Streams and Materials", NEA/NSC/DOC (97)19, Paris, December

Nene R. B., and Turel Z, R., (1994), Indian J. Chem., 33 (4), 357.

Nesmeyanov, An. N., (1984), "A Guide to Practical Radiochemistry". Vol. 2 English Translation, Mir Publishers, Moscow, 1st ed.

Nesmeyanov, An. N., (1974), "Radiochemistry" English Translation, Mir Publishers, Moscow, 1st ed.

Nicholls C. M., (1955), "Criteria for the Selection of Separation Processes", Proceedings of the International Conference on the Paceful Uses of Atomic Energy, vol. 9, p 453, Geneva, 8-20 August

Nilchi A., Hadjmohammadi MR, Garmarodi SR, Saberi R., (2009), J. Hazard. Mater. 167, 531.

Nilchi A, Malek B, Maragheh MG, Khanchi A., (2003) J. Radioanal Nucl Chem 258, 457.

Oh, S. J., Cook, D. C. and Townserd, H. E. (1999), Corros. Sci. 41, 167.

Okamoto S. (1964), J. Soc. Cem. Ind. Japan, 67, 1850.

264 Ona Nguema G, Abdelmoula. M, Jorand F, Benali O, Gehin A., Block J. C and Genin J, M. R, (2002), Iron (II, III) hydroxycarbonate green rust formation and stabilization from lepidocrocite bioremediation. Enviro. Sci. Technol, 36, 16.

Otero A.R, Calvo G. M, Viloseco, F. R: (1977), " Dissolution de alumino por riego con acido nitrico". JEN. 371. Madrid

Ouyang M. and Hiraoka, H. (1997), J. Mater. Research Bull, 32, 1099.

Pajunen P., April (1999), "Chemical Recovery System for Aluminum Finishers", Technical paper 129, Workshop on Cleaner Production in Metal Finishing Industry, Taipei, Taiwan.

Patel R. R., Sarker, S. S., Saraswathly, P., Narasimhan, D. V. S., Singh, L. N., and Arora, S.S., (1995), J. Nucl. Med., 10, 205.

Pinajian J., (1966), Int. J. Appl. Radiat. Isot. 17, 664.

Podolak E. M., (1972), J. Nucl Med 13,388.

Porto P. S.and Krishnan, R. S. (1967) J. Chem. Phys. 47, 1009.

Posely-Dowty J., Moskowitz, B., Crerar, D., Hargraves, R., Tanenbaum, L. and Dow ty, E., (1986), ICARUS 66, 105.

Postima D., (1993), "The reactivity of iron oxides in sediments" , Geochem. Cosmochem. Acta, 57, 5027.

Prout W. E., Russel, K. R. and Groh, H. J., (1965) J. Inorg. Nucl. Chem., 27, 473.

Qafoku NP, Dresel PE, Mckinley JP, Liu C, Heald SM, Ainsworth C. C, Phillips JL, Fruchter JS., (2009), Environ. Sci. Technol. 43,1071.

Qaim S. M., and Stocklin, G., ( 1973) J. Inorg. Nucl. Chem, 35, 19

Qaim, S. M., (1974), Nucl. Phys., A 224, 319.

Qaim, S. M., Wolfle, R., and Strohmaier, B., (1989), Phys.. Rev., C40, 1993.

Qureshi M. and Vaeshney K. G., (1991), "Inorganic Ion Exchangers in Chemical Analysis" CRC. Press, Inc. Florida.

Ramamoorthy N., Vanaja P., Saraswathy P., Iyer S., and Mani R. S., (1985), Artificial Radioactivity, Int. Symp. Pune (India).

265 Rayudu G.V.S., (1993), Radiotracer for Medical Applications II, CRC Press, Boca Raton.

Reich E. and Boegh, K. W., Feb. (1989), Report, 149, INIS.

Richard A, Robert E. W. and Fitzpatrick, (1988), Clays and Clay Menerals, 36, No 2, p 111.

Richard P., (1965), Report-BNL 9032.

Richens D. T. (2007), The Chemistry of Aqua Ions. Wiley. Chichester (1997).

Robbins D., J Appl Chem 8, 777.

Roberts RF, Wilson RH., (1968), Analyst, 93, 237.

Robson J. and Boyd R.E., June (1968), Report of a study group, (1969), Meeting on Radioisotope Production Sposored by the IAEA LuCas Heights Australian, 110: 187 (IAEA Vienna).

Robson J., (1974), Process for the Production of Technetium-99m from Neutron Irradiated Molybdenum Trioxide, U. S. Pat., 3,833, 469.

Roesmer J. September (1970), Radiochemistry of Mercury. NAS-NS-3026, U.S.A,.

Rozan T. F, Taillefert M. Trouwborst R. E. and Glazer B. T. (2002), Limnol Oceanogr. 47, 1346.

Saha B., (1992), Fundamentals of Nuclear Pharmacy, Spring-Verlag, New York, Inc, 3rd ed.

Sanad W., Tadros N. and Haggag, A., (1971), J. Radiochem. Radioanal. Lett. 24 (3), 179.

Sakr T. M., (2010), Ph.D., Thesis Faculty of Pharmacy, Ain Shams University, Cairo, Egypt

Sanchez - Ocampo A., Bulbulian. S, (1991), Appl. Radiat. Isot., 42, 1073. Sandell E. B., (1959), Coloremeteric Determination of Traces of Metals, Interscience Publishers, New York.

Sandru P., and Topa A., (1968), "Radionuclizii", Academiei Republicii Socialiste Romania.

Saraswathly P Sarker, S. K., Arjun, G., Ramamoorthy, N and Nady, S. K. (2004), Radiochem. Acta. 92, 259. 266 c Saraswathy P ., and Narasimhan, D. V. S., (1998), Proc. Int. Atomic Energy Agency on Modern Trends in Radiopharmaceuticals in Diagnosis and Therapy, Vienna 764,385.

Saraswathy P., Narasimhan, D. V. S., Singh, L. N., and Patel, R. R., (1992), Proc. of Nucl. Radiochem. Symp., BRNS., BARC., 325.

a Saraswathy P ., Sarker, S. K., Patel, R. R., Arona, S. S., and Narasimhan, D. V. S., (1998), Radiochem. Acta, 83,97

Saraswathy P., Sarker, S. K., Patel, R. R., Arona, S. S., and Narasimhan, D. V. S., (1999), Appli. Radia. Isot.; 50, 277.

b Saraswathy P ., Sarker, S. K., Ramamoorthy, N., Arjum, G., and Patel, R. R., (1998), Radiochem. Acta, 83, 103.

Sarkar S. K., Saraswathly, P., and Patel, R. R., (1997), Nucl. Radiochem. Symp., BRNS., BARC., 270.

Sarkar S. K., Narasimhan, D. V. S., Saraswathly, P., Singh, L. N., and Patel, R. R., (1995), Nucl. Radiochem. Symp., IGCAR, Kalpakkan, 118.

Savvin S. B., (1961),Talanta, 86, 73.

Scadden E. and Ballou, N. E., January (1960), "The Radiochemistry of Molybdenum", Nuclear Scince Series, Subcommittee on Radiochemistry, National Academy of Scince, National Research Council, NAS-NS 3009, USA,

Schwarzenbach, G., (1962), Pure App. Chem. 5, 377.

Shafiq, Y. F. and Yousif, Z.M., (1995), J. Radioanal. and Nucl. Chem. 199 (3), 173.

Sharygin L, Muromskiy A, Kalyagina M, and Borovkov S., (2007), J Nucl. Sci. Technol. 44, 767.

Shebanovea O. N. and Lazer P. (2003), J. Solid State Chem. 174, 424.

Sheka L. A, and Pevzner Ts. V., Russ. J., (1960), J. Inorg. Chem. 5 (10), 1119

Sherman D. M., (1987), Phis. Chem. Meneral, 14, 355.

Shigematsu T., Omori, T., Aoki, T and Matsui, M., (1975), Bull. Inst. Chem. Res. 53, 435.

267 Shikata E. and Iguchi, A., J., Energy Soc. Japan 26, 662 (1984) and (1986), J. Radioanal. Nucl. Chem. Articles 102, 533.

Simon J., Schulze, W. and Freidmann, L. W., Z. (1974), J. Anal. Chem., 286, 185.

Simon J., Schulze, W and Reinke, R., Z. (1973), J. Anal. Chem., 264, 21.

Simon J., Schulze, W and Voeltz, M., Z. (1972), Inorg. J. Anal. Chem., 394, 233.

Sing J., Powel A. K., Clarke S. E., M and Blower P.J., (1991), J. Chem. Soc. Commun., 1115.

Smic¡iklas I, Dimovic´ S, Plec´as¡ I, Mitric´ M., (2006), J. Water Res. 40, 2267

So, L. V., and Lambrecht, R., J. (1994), J. Label. Comp. Radiopharm., Apr. 270.

So L. V., (1990), Proc. IAEA Research Coordination Meeting of CRP. BRIT., Bombay (India).

Sorby P.J. and Boyd, R. E., (1977), Radiopharmaceuticals Proc. National Universty.

Spitsyn V.I., and Mikheev, M.B., (1971), Atomic Energy Rev., 9, 787.

Srivastava A. K and Jain, P. C, (1989), Elements of nuclear chemistry. 2nd ed, S. Chand and Company Lid , New Delhi.

Srivastava S. C., Meinken, G., Smith. T. D and Richards. P., (1977), Int. J. Appl. Radia. Isot. 28, 83.

Steigman J., (1982), Int. J. Appl. Radiation Isotopes. 33, 829.

Stem H. S., Goodwin D. A., Scheffel U., Wagner H. N. JR., Kramer H. H., (1967), Nucleoniccs; 25, 62.

Stevenson P. C., and Nervik W. E., February (1961), " The Radiochemistry of the Rare Earths, Scandium, Yttrium, and Actinium", Nuclear Science Series, Subcommittee on Radiochemistry, Nuclear Academy of Science, National Research Council, NAS-NS 3020, USA.

Subramanian G., and McAfee J.G., (1971), J. Radiology; 98, 192.

Suter D., Banwart S., and Stumm W , ( 1991), Dissolution of hydrous iron (III) oxides by reductive mechanisms. Langmuir 7, 809.

Suzuki K. N., Osso Jr J. A., September (2009), "Comparative study of the elution efficiency and elution profile of 99mTc in gel and alumina-based 268 chromatographic 99Mo/ 99mTc generators" International Nuclear A tlantic Conference (INAC), Associacao Brasileira de Energia Nuclear, Rio de Janeiro, RJ, Brazil.

Svoboda K., Lezama, J., Melichar, F., Tendilla, J. and Tymple, M., (1985), J. Raioanal. Nucl. Chem. 96, 405.

Sylva R. N., and Davidson, M. R., J. (1979), Chem. Soc. Dalton Trans. 232.

Tachimori S., Nakamura,H. and Amoano, H., (1971) J. Nucl. Sci., Technol. 8, 295.

Takada T., (1969), Bull. Inst. Chem. Res. Kyoto Univ. 47, 298.

Takahashi S., Shikata, E. and Amoano, H., (1970), J. Nucl. Sci., Technol. 7, 130.

Tamaura. Y, Buduan, P. V and Katsura. T, (1981) J. Chem. Soc Dalton Trans., 1807.

Tamaura Y, Kazuo Ito, and Katsura T., (1983), J. Chem. Soc, Dalton Trans.

The Radiochemical Manual, 2nd ed Published by the Radiochemical Center, Amersham (1966).

Thibeau R. J. Brown, C. W. and Heidersbach, R. H., (1978), J. Appl. Spectrosc. 32, 523

Trainor T. P., Brown, G. E.,Parks. G. A, (2000), J. Colloid and Interface Science 231, 359.

Tronc E., Belleville, P., Jolivr, J. P., and Livage, J., (1992), Transformation of ferric hydroxide into spinal by Fe (II) Adsorption. Langmure 8, 313.

Tsuchiya A. and Umagohra, A. (1963), Bull. Chem. Soc. Japan 36, 554.

Tucker W. D., Greene, M. W. and Murrenhoff, A.P., (1962), Atompraxis 5, 163.

Tucker W. D., Greene M. W., Weiss A. J. and Murrenhoff A.P., (1958), Report No BNL 3746 Brookhaven National Laboratory.

Tusa E. H., Paavola A, Harjula R, Lehto J., (1994), J Nucl. Techno. 107:279.

Valentini MTG, Meloni S and Maxia V., (1972), J. Inorg. Nnucl. Chem. 34:1427.

Van Der Kraan. A. M, Medema. J, (1969), J. inorg. Nucl. Chem. 3 1, 2039.

Van der Walls, N. T., and Coetzee, P. P., (2004), Radiochem Acta, 92, Issue 4, Stoclin, Memorial, Issue, 251. 269 Van Eijk. C.W.E et, Vav Nooljen, B. and Schutte. F., (1968), J. Nuclear Physicsa.121, 440

Vanessa Moraes, Barbara Marczewski, Carla Roberta Dias and Joao Alberto Osso Junior, (2005), Brazilian Archives of Biology and Technology, An international journal, 48, 51.

Varma J. and Mandeville. C. E., (1954), Phys. Rev. 94, 91.

Verwey E. J. W., and Overbeek, J. Th. G., (1948), Theory of Stability of Lyophopic Colloids, Elsevier Amsterdam.

Vesely V., and Pekavek, V., (1972), Talanta, 19, 219.

Vickery R. C., (1953), Chemistry of the Lanthanides, Butter worth Scientific Publication, London.

Vlesselar, S., D, Olieslger, W and Hwut, M., (1976), J. Inorg. Nucl. Chem. 38, 227.

Vogel, N. I., (2001), Qualtitative Inorganic Analysis, Thomson Press, India 7th ed.

Vogel, N. I., (1995), Quantitative Inorganic Analysis, 5th ed .

Voges, L. E., and Benjamin M. M., (1996), “The Use of Iron Oxides to Enhance Metal Removal in Crossflow Microfiltration.” Paper presented at WEF 69th Annual Conference and Exposition, Dallas, Texas.

Volkin V. V and Shulgo, K. A. (1967), J. Appl. Chem. USSR, 40 (2), 325.

Wang, Y. M., Lee, C. S., and Cheng, W. L., (1992), J. Radioanal. Nucl. Chem 160 (2), 517.

Wang Z and Saxena, S. K. (2002), Solid State Commun. 123, 195.

Wehrli B., Sulzberger, B., and Summ W. (1989), Redox processes catalyzed by hydrous oxide surface. Chem. Geol. 78, 167.

Wesolowski D. J and Palmar, D, A. (1994), Geochim. Cosmochim. Acta, 58. 2947.

White A. F. and Yee A. (1985), Geochem. Cosmochem. Acta, 49, 1263. Williams A. G. B and Scherer, M. M. (2004), Spectroscopic evidence for Fe (II)- Fe (III) electron transfer at the Fe oxide-water inrerface. Environ. Sci. Technol. 38, 4782.

Witke K. Gotze J, Ròβler, . R., Dietrich D. and Marx, G. (2004), Spectrochim. Acta Part A 60. 2903. 270 Wolf A. M., Baker, B. E. and Pionk, H. B., (1986), J. Soil Scie. 141 (1), 60

Wolfle R., and Qaim, S. M., (1980), J. Radiochem. Acta., 27, 65

Wood D. E., and Bowen, B. M., (1971), J. Nucl. Med., 12(6), 307.

Yang T. Y., Tseng C. L. and Yang, M.H., (1972), Radiochem, Radiation Lett 29 (3), 111.

Yassin T. Report, (1992), J. Aalam Alzarra. Syria

Yoon K. H, Salman, T. and Donnay. G. (1970), J. Colloide Interface Sci. 70, 483.

Zaidi J. H., Karim, H. M. A., and Qaim, S. M., (1985), Radiochem. Acta, 38, 123.

Zaidi J. H., Karim, H. M. A., Arif, M., and Qureshi, M., (1990), Radiochem. Acta, 49, 107.

Zhao D., Sengupta AK, Stewart L., (1998), Ind. Eng. Chem. Res. 37,4383.

Zool I.., (2007), Technethium-99m Radiopharmaceutical: Preparation and Quality Control in Nuclear Medicine, Springer, Birlin.

271 ﺍﻟﻤﻠﺨﺹ ﺍﻟﻌﺭﺒﻰ اﻟﺮﺳﺎﻟﺔ ﺑﻌﻨﻮان " ﺘﻨﻘﻴﺔ ﺍﻟﻤﻭﻟﻴﺒﺩﻨﻴﻭﻡ-٩٩ ﻨﺎﺘﺞ ﺍﻟﺘﻨﺸﻴﻁ ﺍﻻﺸﻌﺎﻋﻰ ﺒﺎﻟﻨﻴﻭﺘﺭﻭﻨﺎﺕ ﻤﻥ ﺍﻟﻨﻭﻴﺩﺍﺕ ﺍﻟﻤﺘﺩﺍﺨﻠﺔ ﺒﺎﻟﻁﺭﻕ ﺍﻟﻜﺭﻭﻤﺎﺘﻭﺠﺭﺍﻓﻴﺔ " ﺗﺘﻀﻤﻦ ﺛﻼﺛﺔ ﻓﺼﻮل هﻰ اﻟﻤﻘﺪﻣﺔ و اﻟﻌﻤﻠﻲ واﻟﻨﺘﺎﺋﺞ واﻟﻤﻨﺎﻗﺸﺔ.

اﻟﻔﺼﻞ اﻷول : اﻟﻤﻘﺪﻣﺔ ، وﻳﺸﻤﻞ ﻧﺒﺬة ﻣﻮﺟﺰة ﻋ ﻦ ﺗﻄﺒﻴﻘﺎت ﻣﻮﻟﺪات ﺗﻜﻨﻴﺴﻴﻮم -٩٩م اﻟﻤﺒﻨﻴﺔ ﻋﻠﻰ ﻣﻮاد اﻟﺠﻞ واﻟﻜﻴﻤﻴﺎء واﻟﻜﻴﻤﻴﺎء اﻹﺷﻌﺎﻋﻴﺔ ﻟﻠﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم، وﻃﺮق إﻧﺘﺎج اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم -٩٩ ، واﻟﻤﻠﻮﺛﺎت اﻟﻤﺸﻌﺔ اﻟﻤﺘﺪ اﺧﻠﺔ ﻣﻊ اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم -٩٩ اﻟﻨﺎﺗﺞ ﻣﻦ اﻟﺘﻨﺸﻴﻂ اﻟﻨﻴﻮﺗﺮوﻧﻲ و ﻣﻮﻟﺪات اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩/اﻟﺘﻜﻨﻴﺴﻴﻮم-٩٩م اﻟﻤﺆﺳﺴﺔ ﻋﻠﻰ ﻣﻮاد ﺟﻞ اﻟﻤﻮﻟﻴﺒﺪات. واﻟﻜﻴﻤﻴﺎء واﻟﻜﻴﻤﻴﺎء اﻹﺷﻌﺎﻋﻴﺔ ﻟﻠﺤﺪﻳﺪ، وﺗﺤﻮﻻت هﻴﺪروآﺴﻴﺪات وأآﺎﺳﻴﺪ هﻴﺪروآﺴﻴﺪات اﻟﺤﺪﻳﺪ (III) وﺳﻠﻮك اﻻدﻣﺼﺎص ﻟﻤﺮآﺒﺎت اﻟﺤﺪﻳﺪ (III) وآﻴﻤﻴﺎء اﻷﻟﻮﻣﻨﻴﻮم واﻟﺤﺪﻳﺪوﺳﻴﺎﻧﺎت آﻤﻮاد ﻟﻸﻋﻤﺪة اﻟﻜﺮوﻣﺎﺗﻮﺟﺮاﻓﻴﺔ ﻣﻊ اﺳﺘﺮﺟﺎع ﻟﻄﺮق ﻓﺼﻞ وﺗﻨﻘﻴﺔ اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ ﻧﺎﺗﺞ اﻟﺘﻨﺸﻴﻂ اﻟﻨﻴﻮﺗﺮوﻧﻲ ﻣﻦ ﻋﻨﺎﺻﺮ اﻟﻤﻠﻮﺛﺎت ﻏﻴﺮ اﻟﻌﻀﻮﻳﺔ اﻟﻤﺨﺘﻠﻔﺔ.

اﻟﻔﺼﻞ اﻟﺜﺎﻧﻲ : وﻳﺘﻀﻤﻦ هﺬا اﻟﻔﺼﻞ اﻟﻤﻮاد اﻟﻜﻴﻤﻴﺎﺋﻴﺔ و اﻻﺟﻬﺰة و اﻟﻄﺮق اﻟﻌﻤﻠﻴﺔ ﻟﻠﺘﻘﻨﻴﺎت اﻟﻤﺨﺘﻠﻔﺔ اﻟﻤﺴﺘﺨﺪﻣﺔ ﻟﺘﺤﻀﻴﺮ وﺗﺸﻌﻴﻊ وإ ذاﺑﺔ وﻓﺼﻞ وﺗﻨﻘﻴﺔ أهﺪاف اﻟﻤﻮﻟﻴﺒﺪﻳﻨ ﻴﻮم اﻟﻤﻐﻠﻔﺔ ﺑﺮﻗﺎﺋﻖ اﻻﻟﻮﻣﻨﻴﻮم. وﻳﺸﻤﻞ أﻳﻀﺎ ﻃﺮق ﺗﺤﻀﻴﺮ وﺗﻮﺻﻴﻒ ﻣﺎدة ﺣﺪﻳﺪوﺳﻴﺎﻧﺎت اﻟﺒﻮﺗﺎﺳﻴﻮم -اﻟﻨﻴﻜﻞ و ﻣﻮﻟﺪ اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم -٩٩/اﻟﺘﻜﻨﻴﺴﻴﻮم-٩٩م اﻟﻤﺒﻨﻲ ﻋﻠﻰ ﻣﺎدة ﺟﻞ ﻣﻮﻟﻴﺒﺪات اﻟﺰرآﻮﻧﻴﻮم وﻳﺘﻀﻤﻦ اﻳﻀﺎ ﺗﺘﺒﻊ ادﻣﺼﺎص اﻟﻤﻮﻟﻴﺒﺪﻧﻴﻮم -٩٩ وﺗﻨﻘﻴﺔ اﻟﻤﺤﺎﻟﻴﻞ ﻣﻦ اﻟﺸﻮاﺋﺐ اﻟﻤﺘﺪاﺧﻠﺔ ﻋﻦ ﻃﺮﻳﻖ ﺗﺮﺳﻴﺐ هﻴﺪروآﺴﻴﺪات اﻟﺤﺪﻳﺪ (III) و اﻻﻟﻮﻣﻮﻧﻴﻮم اﻟﻰ ﺟﺎﻧﺐ اﺳﺘﺨﺪام ﻋﻤﻮد آﺮوﻣ ﺎﺗﻮﺟﺮاﻓﻰ ﻣﻦ اﻟﺒﻮﺗﺎﺳﻴﻮم ﻧﻴﻜﻞ هﻜﺴﺎﺳﻴﺎﻧﻮ ﻓﻴﺮات(II). ودراﺳﺔ ﻣﺘﻐﻴﺮات إدﻣﺼﺎص اﻟﻤﻮﻟﻴﺒﺪﻧﻴﻮم -٩٩و اﻟﺸﻮاﺋﺐ اﻟﻤﺮاﻓﻘﺔ ﻋﻠﻰ اآﺎ ﺳﻴﺪ و اآﺎﺳﻴﺪ هﻴﺪروآﺴﻴﺪات اﻟﺤﺪﻳﺪ (III) و اﻻﻟﻮﻣﻨﻴﻮم . و اﻟﺘﻌﺮف ﻋﻠﻰ ﻧﻮع اﻟﻤﺪﻣﺺ اﻟﻨﺎﺗﺞ ﻋﻨﺪ آﻞ ﻣﻦ اﻟﻤﺘﻐﻴﺮات اﻟﻤﺪروﺳﺔ.

اﻟﻔﺼﻞ اﻟﺜﺎﻟﺚ: وﻳﺘﻀﻤﻦ هﺬا اﻟﻔﺼﻞ اﻟﻨﺘﺎﺋﺞ واﻟﻤﻨﺎﻗﺸﺔ ﻟﻌﻤﻠﻴﺔ ﺗﻨﻘﻴﺔ أهﺪاف اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم اﻟﻤﺸﻌﻌﺔ وﻋﻤﻠﻴﺔ ﺗﺤﻀﻴﺮ وأداء ﻣﻮﻟﺪ اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩/اﻟﺘﻜﻨﻴﺴﻴﻮم-٩٩م ﺑﻄﺮﻳﻘﺔ ﻣﻨﻬﺠﻴﺔ.

أوﻻ، ﺗﻢ ﺗﺸﻌﻴﻊ اﻷهﺪاف (اﻟﻤﻜﻮﻧﺔ ﻣﻦ ﻣﺴﺤﻮق ﺛﺎﻟﺚ أآﺴﻴﺪ اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم اﻟﻤﻐﻠﻒ ﺑﺮﻗﺎﺋﻖ اﻷﻟﻮﻣﻴﻨﻴﻮم) ﻓﻲ اﻟﻤﻔﺎﻋﻞ اﻟﻤﺼﺮي اﻟﺒﺤﺜﻲ اﻟﺜﺎﻧﻲ (ETRR-II) ﻟﻤﺪة ~٤ ﺳﺎﻋﺎت ﻓﻲ ﻓﻴﺾ ﻧﻴﻮﺗﺮوﻧﻲ ﺣﺮاري ﻣﻘﺪارﻩ ~ ١×١٤١٠ ن ﺳﻢ -٢ ث -١ ﺛﻢ ﺗﺒﺮﻳﺪهﺎ ﻟﻔﺘﺮات ﻣﺨﺘﻠﻔﺔ (ﻣﻦ ٣ إﻟﻰ ٧٥ ﻳﻮﻣﺎ) وذﻟﻚ ﻟﻠﺘﻌﺮف ﻋﻠﻰ آﻞ ﻣﻦ اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم -٩٩ وﻧﻮﻳﺪات اﻟﻤﻠﻮﺛﺎت اﻟﻤﺸﻌﺔ اﻟﻤﺘﺪاﺧﻠﺔ اﻟﻨﺎﺗﺠﺔ ﻣﻦ اﻟﺘﻔﺎﻋﻼت اﻟﻨﻮوﻳﺔ ﻟﻠﻨﻴﻮﺗﺮوﻧﺎت اﻟﺤﺮارﻳﺔ و /أو اﻟﻨﻴﻮﺗﺮوﻧﺎت ﻓﻮق اﻟﺤﺮارﻳﺔ . وأﺷﺎر ت ﻗﻴﺎﺳﺎت اﻟﺘﺤﻠﻴﻞ اﻹﺷﻌﺎﻋﻲ ﻷهﺪاف اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم اﻟﻤﺸﻌﻌﺔ إﻟﻰ وﺟﻮد ﻣﻠﻮﺛﺎت ﻣﺸﻌﺔ ﻣﺘﺪاﺧﻠﺔ ﻣﺜﻞ اﻟﺴﻴﺰﻳﻮم -١٣٤ واﻟﺴﻴﺮﻳﻮم -١٤١ واﻟﻜﺮوم -٥١ واﻹﻳﻮروﺑﻴﻮم -١٥٢ واﻟﻨﻴﻮﺑﻴﻮم-١٩٢م واﻟﺰرآﻮﻧﻴﻮم-٩٥/اﻟﻨﻴﻮﺑﻴﻮم-٩٥ واﻟﺰﻧﻚ-٦٥ واﻷﻧﺘﻴﻤﻮن-١٢٤ واﻟﻜﻮﺑﺎﻟﺖ-٦٠. ﺑﻴﻨﻤﺎ أﺷﺎرت ﺗﻠﻚ اﻟﺘﺤﺎﻟﻴﻞ اﻟﻰ ان رﻗﺎﺋﻖ اﻷﻟﻮﻣﻴﻨﻴﻮم (اﻟﻤﺴﺘﺨﺪﻣﺔ ﻓﻲ ﺗﻐﻠﻴﻒ اﻷهﺪاف ) ﺗﺘﺴﺒﺐ ﻓﻰ وﺟﻮد ﻣﻠﻮﺛﺎت ﻣﺜﻞ اﻟﺴﻴﺮﻳﻮم -١٤١ واﻹﻳﻮروﺑﻴﻮم-١٥٢ واﻟﻜﻮﺑﺎﻟﺖ-٦٠ واﻷﻧﺘﻴﻤﻮن-١٢٤ واﻟﺰﻧﻚ-٦٥ واﻟﻼﻧﺜﺎﻧﻴﻮم-١٤٠ واﻟﺰرآﻮﻧﻴﻮم-٩٥/اﻟﻨﻴﻮﺑﻴﻮم-٩٥ واﻟﻬﺎﻓﻨﻴﻮم-١٧٥و١٨١ واﻟﺤﺪﻳﺪ-٥٩ واﻻﺳﻜﺎﻧﺪﻳﻮم-٤٦ واﻟﻤﻨﺠﻨﻴﺰ-٥٤. و ﻗﺪ ﺗﻢ ﺗﻮﺻﻴﻒ هﺬﻩ اﻟﻤﻠﻮﺛﺎت و ﻣﻨﺎﻗﺸﺔ اﻟﺼﻔﺎت اﻟﻨﻮوﻳﺔ اﻟﻤﻤﻴﺰة و ﺗﻔﺎﻋﻼت ﺗﻮﻟﻴﺪهﺎ ﻓﻰ ﻣﺎدة اﻟﻬﺪف.

ﺛﺎﻧﻴﺎ، ﺑﻌﺪ إذاﺑﺔ أهﺪاف اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم اﻟﻤﺸﻌﻌﺔ (ﻣﻊ رﻗﺎﺋﻖ اﻷﻟﻮﻣﻴﻨﻴﻮم اﻟﻤﺴﺘﺨﺪﻣﺔ ﻓﻲ ﺗﻐﻠﻴﻔﻬﺎ ) ﻓﻲ ٣٠ ﻣﻞ ﻣﻦ ﻣﺤﻠﻮل ٥ ﻣ ﻮﻻر هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم ﻓﻲ زﻣﻦ ﻗﺪرﻩ ~ ١٥ دﻗﻴﻘﺔ ﺗﻢ إﺿﺎﻓﺔ ٠٫٥ ﻣﻞ ﻣﻦ ﻣﺤﻠﻮل ١٠% (وزن/ ﺣﺠﻢ) ﻓﻮق أآﺴﻴﺪ اﻟﻬﻴﺪروﺟﻴﻦ آﻌﺎﻣﻞ ﻣﺆآﺴﺪ . ﺗﻢ ﻓﺼﻞ ﻣﺤﻠﻮل اﻟﻤﻮﻟﻴﺒﺪات-اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ ﻣﻦ راﺳﺐ اآﺎﺳﻴﺪ وأآﺎﺳﻴﺪ هﻴﺪروآﺴﻴﺪات اﻟﺤﺪﻳﺪ (III) اﻟﻨﺎﺗﺞ ﻣﻦ اآﺴﺪة اﻟﺤﺪﻳﺪ اﻟﻤﻮﺟﻮد آﺸﻮاﺋﺐ آﻴﻤﻴﺎﺋﻴﺔ ﻓﻲ رﻗﺎﻗﺔ اﻷﻟﻮﻣﻴﻨﻴﻮم (١٫٣٧ ﻣﺠﻢ ﺣﺪﻳﺪ ﻓﻲ ٠٫٦ ﺟﻢ أﻟﻮﻣﻴﻨﻴﻮم) ﺑﻄﺮﻳﻘﺔ اﻟﻄﺮد اﻟﻤﺮآﺰى و اﻟﻔﻠﺘﺮة . وأﺷﺎرت اﻟﻘﻴﺎﺳﺎت اﻹﺷﻌﺎﻋﻴﺔ إﻟﻰ أن ﺗﺮﺳﻴﺐ اآﺎﺳﻴﺪ وأآﺎﺳﻴﺪ هﻴﺪروآﺴﻴﺪات اﻟﺤﺪﻳﺪ(III) ﻗﺪ أدى ﻋﻨﺪ هﺬﻩ اﻟﻈﺮوف اﻟﻤﻌﻤﻠﻴﺔ إﻟﻰ اﻟﺘﺨﻠﺺ اﻟﻜﻤﻲ ﻣﻦ اﻟﻼﻧﺜﻨﻴﺪات (اﻟﻼﻧﺜﺎﻧﻴﻮم-١٤٠ واﻟﺴﻴﺮﻳﻮم-١٤١ واﻹﻳﻮروﺑﻴﻮم-١٥٢) ﺑﺎﻹﺿﺎﻓﺔ إﻟﻰ اﻟﻤﻨﺠﻨﻴﺰ -٥٤ واﻟﻨﻴﻮﺑﻴﻮم-٩٢م و اﻟﺘﻨﻘﻴﺔ اﻟﺠﺰﺋﻴﺔ ﻟﻤﺤﻠﻮل اﻟﻤﻮﻟﻴﺒﺪات- اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ ﻣﻦ ~ ٣٥ و٦٨ و٥٠ و٨٠ ٪ ﻣﻦ اﻟﻜﺮوم-٥١ واﻻﺳﻜﺎﻧﺪﻳﻮم-٤٦ واﻟﺤﺪﻳﺪ-٥٩ و اﻟﻜﻮﺑﺎﻟﺖ-٦٠، ﻋﻠﻰ اﻟﺘﻮاﻟﻲ . ﺑﻴﻨﻤﺎ وﺟﺪ أن اﻟﻨﻮﻳﺪات اﻟﻤﺸﻌﺔ ﻟﻜﻞ ﻣﻦ اﻟﺴﻴﺰﻳﻮم -

١٣٤ واﻟﺮوﺑﻴﺪﻳﻮم-٨٦ واﻟﺰرآﻮﻧﻴﻮم-٩٥ واﻟﻬﺎﻓﻨﻴﻮم- ١٧٥و١٨١ واﻷﻧﺘﻴﻤﻮن-١٢٤ ﻟﻢ ﺗﺘﺎﺛﺮ ﺑﻌﻤﻠﻴﺔ اﻣﺘﺰاز او ادﻣﺼﺎص ﻋﻠﻰ ﺳﻄﺢ رواﺳﺐ ﻣﻌﺎدن اﻟﺤﺪﻳﺪ(III) اﻟﻤﺘﻜﻮﻧﺔ.

ﺛﺎﻟﺜﺎ، وﺟﺪ أن راﺳﺐ اآﺎﺳﻴﺪ وأآﺎﺳﻴﺪ هﻴﺪروآﺴﻴﺪات اﻟﺤﺪﻳﺪ(III) اﻟﻤﺘﻜﻮن ﻗﺪ اﺣﺘﺠﺰ ٠٫٩٧ ٪ ﻣﻦ أﻧﻴﻮﻧﺎت اﻟﻤﻮﻟﻴﺒﺪات-اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻮم-٩٩ ﻋﺒﺮ ﺁﻟﻴﺔ إﺣﺘﻮاﺋﻬﺎ ﻓﻰ اﻟﻄﺒﻘﺔ اﻟﻤﺎﺋﻴﺔ اﻟﻤﺤﻴﻄﺔ ﺑﺎﻟﺠﺴﻴﻤﺎت اﻟﺪﻗﻴﻘﺔ ﻟﻠﺮاﺳﺐ اﻟﻤﺘﻜﻮن . وﻗﺪ ﺗﺤﻘﻖ إﺳﺘﺮﺟﺎع أﻧﻴﻮﻧﺎت اﻟﻤﻮﻟﻴﺒﺪات -اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻮم -٩٩ اﻟﻤﺤﺘﺠﺰة آﻤﻴﺎ ﺑﻐﺴﻞ اﻟﺮاﺳﺐ ﻣﺮﺗﻴﻦ ﺑﺎﺳﺘﺨﺪام ٥ ﻣﻞ ﻣﻦ ﻣﺤﻠﻮل ٠٫٥ ﻣﻮﻻر هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم و ﻟﻜﻦ ﻣﺼﺤﻮﺑﺎ ﺑﺎﺳﺘﺮﺟﺎع ≤ ٠٫١٩١٨ و ٠٫٣١٨ ٪ ﻣﻦ اﻟﻨﻮﻳﺪات اﻟﻤﺸﻌﺔ ﻟﻜﻞ ﻣﻦ ﻣﻠﻮﺛﺎت اﻟﻜﻮﺑﺎﻟﺖ-٦٠ واﻟﻨﻴﻮﺑﻴﻮم-٩٢م ﻋﻠﻰ اﻟﺘﻮاﻟﻲ. آﻤﺎ ﺗﻢ ﺗﻘﻴﻴﻢ ﺗﺄﺛﻴﺮ ﺟﺮﻋﺔ اﻟﺤﺪﻳﺪ اﻹﺟﻤﺎﻟﻴﺔ ﻋﻠﻰ إ زاﻟﺔ اﻟﺤﺪﻳﺪ-٥٩ و ﻏﻴﺮﻩ ﻣﻦ اﻟﻤﻠﻮﺛﺎت اﻟﻤﺸﻌﺔ واﻟﻘﺪرة ﻋﻠﻰ اﺣﺘﺠﺎز أﻧﻴﻮﻧﺎت اﻟﻤﻮﻟﻴﺒﺪات-اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ وذﻟﻚ ﺑﺈﺿﺎﻓﺔ آﻤﻴﺎت ﻣﺨﺘﻠﻔﺔ ﻣﻦ آﻠﻮرﻳﺪ اﻟﺤﺪﻳﺪﻳﻚ ﺳﺪاﺳﻲ اﻟﺘﻤﻴﺆ إﻟﻰ اﻷهﺪاف اﻟﻤﺸﻌﻌﺔ ﻗﺒﻞ اﻹذاﺑﺔ ﻣﻊ ٣٤ ﻣﻞ ﻣﻦ ﻣﺤﻠﻮل ٥ ﻣﻮﻻر هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم ﺛﻢ إﺿﺎﻓﺔ ٠٫٥ ﻣﻞ ﻣﻦ ﻣﺤﻠﻮل١٠% ﻓﻮق أآﺴﻴﺪ اﻟﻬﻴﺪروﺟﻴﻦ آﻌﺎﻣﻞ ﻣﺆآﺴﺪ . وأﻇﻬﺮت اﻟﻨﺘﺎﺋﺞ اﻟﺘﻲ ﺗﻢ اﻟﺤﺼﻮل ﻋﻠﻴﻬﺎ أن ﻧﺴﺐ إزاﻟﺔ اﻟﺤﺪﻳﺪ -٥٩ واﻟﻜﺮوم -٥١ واﻻﺳﻜﺎﻧﺪﻳﻮم-٤٦ واﻟﻜﻮﺑﺎﻟﺖ-٦٠ واﻟﺰرآﻮﻧﻴﻮم-٩٥ واﻟﺰﻧﻚ-٦٥ واﻟﻬﺎﻓﻨﻴﻮم-١٧٥و١٨١ واﻷﻧﺘﻴﻤﻮن-١٢٤ ﻗﺪ زادت ﺑ ﺰﻳﺎدة ﺗﺮآﻴﺰ اﻟﺤﺪﻳﺪ اﻟﻤﻀﺎف ﻣﻦ ٠٫٧٢١ إﻟﻰ ٧٫٨×١٠-٣ ﻣﻮﻻر . آﻤﺎ وﺟﺪ أن ﻧﺴﺒﺔ اﺣﺘﺠﺎز أﻧﻴﻮﻧﺎت اﻟﻤﻮﻟﻴﺒﺪات -اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم -٩٩ ﺗﺰداد ﻣﻊ زﻳﺎدة ﺟﺮﻋ ﺔ اﻟﺤﺪﻳﺪ اﻟﻤﻀﺎف اآﺜﺮ ﻣﻦ ٣٫٩٩× ١٠-٣ ﻣﻮﻻر ﻟﺘﺼﻞ اﻟﻰ ٥،٨ % ﻋﻨﺪ ﺗﺮآﻴﺰﻟﻠﺤﺪﻳﺪ ﻗﺪرﻩ ٧٫٢٦ ×١٠-٣ ﻣﻮﻻر.

ﺗﻤﺖ دراﺳﺔ ﺗﺄﺛﻴﺮ ﺗﺮآﻴﺰ هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم ﻋﻠﻰ إزاﻟﺔ اﻟﻤﻠﻮﺛﺎت اﻟﻤﺸﻌﺔ واﺣﺘﺠﺎزاﻟﻤﻮﻟﻴﺒﺪات-اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ ﻋﻨﺪ اﻟﺘﺮآﻴﺰات ٤٫٠ و٢٫٠ و١٫٠ و٠٫٥ ﻣﻮﻻر هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم ﻓﻰ وﺟﻮد ﺟﺮﻋﺔ ﺛﺎﺑﺘﺔ ﻣﻦ اﻟﺤﺪﻳﺪ اﻟﻤﻀﺎف [٧٫٥٨ ﻣﺠﻢ ﻣﻦ اﻟﺤﺪﻳﺪ: ٣٫٩٩×١٠-٣ ﻣﻮﻻرﺣﺪﻳﺪ و ﺣﺠﻢ ﺛﺎﺑﺖ ٠٫٥ ﻣﻞ ﻣﻦ ﻣﺤﻠﻮل ١٠% ﻓﻮق أآﺴﻴﺪ اﻟﻬﻴﺪروﺟﻴﻦ . أﺷﺎرت اﻟﻨﺘﺎﺋﺞ إﻟﻰ أن ﻧﺴﺐ إزاﻟﺔ آﻞ ﻣﻦ اﻟﺤﺪﻳﺪ-٥٩ واﻟﻜﺮوم-٥١ واﻻﺳﻜﺎﻧﺪﻳﻮم -٤٦ واﻟﻜﻮﺑﺎﻟﺖ - ٦٠ واﻟﺰرآﻮﻧﻴﻮم-٩٥ واﻟﺰﻧﻚ-٦٥ واﻟﻬﺎﻓﻨﻴﻮم-١٧٥و١٨١ واﻷﻧﺘﻴﻤﻮن-١٢٤ ﻗﺪ ازدادت ﻣﻊ ٣

اﻧﺨﻔﺎض ﺗﺮآﻴﺰ هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم ﻓﻲ اﻟﻤﺤﻠﻮل ﻓﻲ اﻟﻤﺪى ﻣﻦ ٤ إﻟﻰ ٠٫٥ ﻣﻮﻻر. ﺑﻴﻨﻤﺎ ازدادت ﻧﺴﺒﺔ اﺣﺘﺠﺎز أﻧﻴﻮﻧﺎت اﻟﻤﻮﻟﻴﺒﺪات-اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم -٩٩ زﻳﺎدة ﺣﺎدة ﻣﻦ ~ ٠٫٩٣٣ ٪ إﻟﻰ ~ ٥٫٧٦٪ ﻣﻊ ﺗﻨﺎﻗﺺ ﺗﺮآﻴﺰ هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم ﻓﻲ اﻟﻤﺤﻠﻮل ﻣﻦ ٤٫٠ إﻟﻰ ١٫٠ ﻣﻮﻻر ﻣﻊ اﻧﺨﻔﺎض هﺬﻩ اﻟﻨﺴﺒﺔ ﻋﻜﺴﻴﺎ إﻟﻰ ١٫٥٣ ٪ ﻣﻊ ﺧﻔﺾ ﺗﺮآﻴﺰ هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم إﻟﻰ ٠٫٥ ﻣﻮﻻر.

آﻤﺎ ﺗﻢ أﻳﻀﺎ اﺳﺘﻘﺼﺎء ﺗﺒﺎﻳﻦ ﺗﺄﺛﻴﺮ ﺗﺮآﻴﺰ ﻣﺤﻠﻮل ﻓﻮق أآﺴﻴﺪ اﻟﻬﻴﺪروﺟﻴﻦ ﻋﻠﻰ إزاﻟﺔ اﻟﻤﻠﻮﺛﺎت اﻟﻤﺸﻌﺔ ﻋﻠﻰ اﺳﻄﺢ ر واﺳﺐ اآﺎﺳﻴﺪ وأآﺎﺳﻴﺪ هﻴﺪروآﺴﻴﺪات اﻟﺤﺪﻳﺪ اﻟﻤﺘﻜﻮﻧ ﻪ وذﻟﻚ ﺑﺈذاﺑﺔ أهﺪاف اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم اﻟﻤﺸﻌﻌﺔ ﻓﻲ ٣٤ ﻣﻞ ﻣﻦ ﻣﺤﻠﻮل ٥ ﻣﻮﻻر هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم اﻟﺬي ﻳﺤﺘﻮي ﻋﻠﻰ ٧٫٥٨ ﻣﺠﻢ ﻣﻦ اﻟﺤﺪﻳﺪ و اﻷآﺴﺪة ﺑﺈﺿﺎﻓﺔ أﺣﺠﺎم ﻣﺨﺘﻠﻔﺔ (٠٫٢٥ و٠٫٥ و١٫٠ ﻣﻞ ) ﻣﻦ ﻣﺤﻠﻮل ﻓﻮق أآﺴﻴﺪ اﻟﻬﻴﺪروﺟﻴﻦ . أﺷﺎرت اﻟﻨﺘﺎﺋﺞ إﻟﻰ إﻧﺨﻔﺎض ﻧﺴﺒﺔ إزاﻟﺔ اﻟﺤﺪﻳﺪ -٥٩ ﻣﻊ زﻳﺎدة ﺣﺠﻢ ﻓﻮق أآﺴﻴﺪ اﻟﻬﻴﺪروﺟﻴﻦ ﻓﻲ اﻟﻤﺤﻠﻮل ﻣﻦ ٠٫٢٥ ﻣﻞ إﻟﻰ ١٫٠ ﻣ ﻞ، وﻳ ﺼﺤﺐ هﺬا أﻳﻀﺎ اﻧﺨﻔﺎض ﻓﻲ ﻧﺴﺐ إزاﻟﺔ اﻟﻨﻮﻳﺪات اﻟﻤﺸﻌﺔ ﻟﻜﻞ ﻣﻦ اﻻﺳﻜﺎﻧﺪﻳﻮم- ٤٦ واﻟﻜﻮﺑﺎﻟﺖ-٦٠ واﻟﺰرآﻮﻧﻴﻮم- ٩٥/اﻟﻨﻴﻮﺑﻴﻮم-٩٥ واﻟﺰﻧﻚ-٦٠ واﻟﻬﺎﻓﻨﻴﻮم-١٧٥و١٨١. آﻤﺎ ازدادت ﻧﺴﺒﺔ إزاﻟﺔ اﻟﻜﺮوم-٥١ ﺑﺸﺪة ﻣﻊ ازدﻳﺎد ﺣﺠﻢ ﻓﻮق أآﺴﻴﺪ اﻟﻬﻴﺪروﺟﻴﻦ اﻟﻤﻀﺎف ﻓﻲ اﻟﻤﺪى ﻣﻦ ٠٫٢٥ إﻟﻰ ٠٫٥ ﻣﻞ، ﺑﻴﻨﻤﺎ وﺟﺪ أن هﺬﻩ اﻟﻨﺴﺒﺔ ﻓﻲ ﺣﺎﻟﺔ اﻷﻧﺘﻴﻤﻮن -١٢٤ ﻗﺪ ازدادت ﺑﻄﺮﻳﻘﺔ ﻣﻠﺤﻮﻇﺔ ﻓﻲ اﻟﻤﺪى ﻣﻦ ٠٫٢٥ إﻟﻰ ٠٫٥ ﻣﻞ. ووﺟﺪ أن ﻧﺴﺒﺔ اﺣﺘﺠﺎز اﻟﻤﻮﻟﻴﺒﺪات-اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ ﻗﺪ ﺗﻨﺎﻗﺼﺖ ﺑﺎدىء اﻷﻣﺮ ﻣﻊ زﻳﺎدة ﺣﺠﻢ ﻓﻮق أآﺴﻴﺪ اﻟﻬﻴﺪروﺟﻴﻦ ﺛﻢ أﺧﺬت ﻓﻲ اﻟﺰﻳﺎدة ﻣﻜﻮﻧﺔ ﻣﻨﺤﻨﻴﺎ ﻣﻘﻌﺮا ذو ﺣﺪ أدﻧﻲ ﻋﻨﺪ ٠٫٦٥ ﻣﻞ. ﻟﻢ ﺗﺘﺄﺛﺮ ﻧﺴﺐ اﻹزاﻟﺔ اﻟﻜﻤﻴﺔ ﻟﻼﻧﺜ ﺎﻧﻴﺪات (اﻟﻼﻧﺜﺎﻧﻴﻮم-١٤٠ واﻟﺴﻴﺮﻳﻮم-١٤١ واﻹﻳﻮروﺑﻴﻮم-١٥٢) واﻟﻨﻴﻮﺑﻴﻮم-٩٢م واﻟﻤﻨﺠﻨﻴﺰ-٥٤ ﺑﺎﺧﺘﻼف ﺗﺮآﻴﺰات اﻟﺤﺪﻳﺪ أو هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم أو ﺗﺮآﻴﺰ ﻣﺤﻠﻮل ﻓﻮق أآﺴﻴﺪ اﻟﻬﻴﺪوﺟﻴﻦ ﻓﻲ اﻟ ﻤﺤﻠﻮل . وﺑﺴﺒﺐ ﻣﻨﺎﻓﺴﺔ اﻟﺘﺮآﻴﺰ اﻟﻌﺎﻟﻰ ﻷﻳﻮﻧﺎت اﻟﺼﻮدﻳﻮم (١+)، ﻓﺈن اﻟﻨﻮﻳﺪات اﻟﻤﺸﻌﺔ ﻟﻠﺴﻴﺰﻳﻮم -١٣٤ واﻟﺮوﺑﻴﺪﻳﻮم -٨٦ ﻗﺪ ﺑﻘﻴﺖ آﻤﻴﺎ ﻓﻲ ﻣﺤﻠﻮل اﻟﻤﻮﻟﻴﺒﺪات-اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ وﻟﻢ ﺗﺘﺎﺛﺮ ﺑﺘﻐﻴﺮ اﻟﺘﺮآﻴﺰات اﻟﻤﺨﺘﻠﻔﺔ ﻣﻦ اﻟﺤﺪﻳﺪ أوهﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم أوﻓﻮق أآﺴﻴﺪ اﻟﻬﻴﺪروﺟﻴﻦ ﻓﻰ وﺳﻂ اﻟﺘﻔﺎﻋﻞ .

وأﺷﺎرت اﻟﺪراﺳﺎت اﻹﺳﺘﻘﺼﺎﺋﻴﺔ ﻷﻃﻴﺎف راﻣﺎن ﻟﺮواﺳﺐ اﻟﺤﺪﻳﺪ اﻟﻤﺘﻜﻮﻧﺔ (ﺳﻮاء ﻣﻦ اﻟﺤﺪﻳﺪ اﻟﻤﻮﺟﻮد ﻓﻲ رﻗﺎﺋﻖ اﻷﻟﻮﻣﻴﻨﻴﻮم و/ أو اﻟﺤﺪﻳﺪ اﻟﻤﻀﺎف إﻟﻰ ﺧﻠﻴﻂ اﻟﺘﻔﺎﻋﻞ ) إﻟﻰ أ ن اﻟﺴﻠﻮك اﻟﻤﺨﺘﻠﻒ ﻟﻠﺮواﺳﺐ اﻟﻤﺘﻜﻮﻧﺔ ﻣﻦ ﻣﻌﺎدن اﻟﺤﺪﻳﺪ ﻳﺮﺟﻊ إﻟﻰ ﺗﻔﺎﻋﻼت اﻟﺘﺤﻮل ﻣﻦ هﻴﺪروآﺴﻴﺪات وأآﺎﺳﻴﺪ هﻴﺪروآﺴﻴﺪات اﻟﺤﺪﻳﺪ(III) اﻷﻗﻞ اﺳﺘﻘﺮارا إﻟﻰ ﺗﻠﻚ اﻷآﺜﺮ اﺳﺘﻘﺮارا ﻣﻦ ﻧﻮع اآﺎﺳﻴﺪ اﻟﺤﺪﻳﺪ(III) ﻣﺜﻞ اﻟﻬﻴﻤﺎﺗﻴﺖ > ﻣﺎﻏﻴﻤﻴﺖ-اآﺎﺳﻴﺪ اﻟﻬﻴﺪروآﺴﻴﺪات ﻣﺜﻞ اﻟﺠﻮﺗﻴﺖ > اﻟﻠﻴﺒﻴﺪوآﺮوﺳﻴﺖ>اﻟﻔﻴﺮﻳﻬﻴﺪرﻳﺖ-اآﺴﻴﺪ اﻟﻤﺎﺟﻨﻴﺘﻴﺖ.

ﺗﻢ ﺗﺤﻤﻴﺾ اﻟﻤﺤﻠﻮل اﻟﺮاﺋﻖ اﻟﻨﺎﺗﺞ ﺑﻌﺪ ﻋﻤﻠﻴﺔ ﺗﺮﺳﻴﺐ اﻟﺤﺪﻳﺪ ﺑﺤﻤﺾ اﻟﻨﻴﺘﺮﻳﻚ ﻟﺘﺮﺳﻴﺐ هﻴﺪروآﺴﻴﺪ اﻷﻟﻮﻣﻴﻨﻴﻮم ﻋﻨﺪ اﻷس اﻟﻬﻴﺪروﺟﻴﻨﻲ ٩٫٥. ﺗﻤﺖ اﻹزاﻟﺔ اﻟﻜﻤﻴﺔ ﻟﻤﺎ ﺗﺒﻘﻰ ﻣﻦ اﻟﻨﻮﻳﺪات اﻟﻤﺸﻌﺔ ﻟﻜﻞ ﻣﻦ اﻟﻜﻮﺑﺎﻟﺖ-٦٠ واﻟﺤﺪﻳﺪ-٥٩ واﻻﺳﻜﺎﻧﺪﻳﻮم-٤٦ واﻟﺰرآﻮﻧﻴﻮم-٩٥/اﻟﻨﻴﻮﺑﻴﻮم-٩٥ واﻟﺰﻧﻚ-٦٥ واﻷﻧﺘﻴﻤﻮن-١٢٤ اﻟﻬﺎﻓﻨﻴﻮم-١٧٥و١٨١ ﻣﻦ اﻟﻤﺤﻠﻮل اﻟﺮاﺋﻖ ﻟﻠﻤﻮﻟﻴﺒﺪات - اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ ﺧﻼل اﻟﺘﺮﺳﻴﺐ اﻟﻤﺸﺘﺮك و/أو اﻻﻣﺘﺰاز ﻋﻠﻰ ﺳﻄﺢ راﺳﺐ هﻴﺪروآﺴﻴﺪ اﻷﻟﻮﻣﻴﻨﻴﻮم. وﻓﻲ اﻟﻮﻗﺖ ﻧﻔﺴﻪ، ﻓﻘﺪ ﺗﺒﻘﻲ آﻞ ﻣﻦ اﻟﺴﻴﺰﻳﻮم -١٣٤ و اﻟﺮوﺑﻴﺪﻳﻮم -٨٦ ﻣﻊ ٥% و٢% ﻣﻦ آﻞ ﻣﻦ اﻟﻜﺮوم -٥١ واﻟﻜﻮﺑﺎﻟﺖ -٦٠ اﻟﻤﺘﺒﻘﻴﻴﻦ، ﻋﻠﻰ اﻟﺘﻮاﻟﻲ، ﺑﺎﻹﺿﺎﻓﺔ إﻟﻰ ﻧﺤﻮ ٨٥ ٪ ﻣﻦ اﻟﻜﻤﻴﺔ اﻷﺻﻠﻴﺔ ﻷﻧﻴﻮﻧﺎت اﻟﻤﻮﻟﻴﺒﺪات -اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ ﻓﻲ اﻟﻤﺤﻠﻮل اﻟﺮاﺋﻖ ﺑﻌﺪ ﺗﺮﺳﻴﺐ هﻴﺪوآﺴﻴﺪ اﻷﻟﻮﻣﻴﻨﻴﻮم. وﻗﺪ أﻣﻜﻦ اﺳﺘﺮﺟﺎع ١٣٫٨ ٪ ﻣﻦ اﻟﻜﻤﻴﺔ اﻷﺻﻠﻴﺔ ﻷﻧﻴﻮﻧﺎت اﻟﻤﻮﻟﻴﺒﺪات -اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴ ﻮم- ٩٩ ﻋﻦ ﻃﺮﻳﻖ ﻏﺴﻞ راﺳﺐ هﻴﺪروآﺴﻴﺪ اﻷﻟﻮﻣﻴﻨﻴﻮم ٤ ﻣﺮات، آﻞ ﻣﺮة ﺑﺤﺠﻢ ٨ ﻣﻞ ﻣﻦ ﻣﺤﻠﻮل ٣٫٥ ﻣﻮﻻر ﻧﻴﺘﺮات اﻟﺼﻮدﻳﻮم ذي أس هﻴﺪروﺟﻴﻨﻲ ٩٫٥. وﺑﻌﺪ ﻋﻤﻠﻴﺔ اﻟﻐﺴﻴﻞ وﺟﺪ أن ﺣﻮاﻟﻲ ٠٫٢٣ ٪ ﻣﻦ اﻟﻜﻤﻴﺔ اﻷﺻﻠﻴﺔ ﻷﻧﻴﻮﻧﺎت اﻟﻤﻮﻟﻴﺒﺪات-اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ ﻗﺪ ﺑﻘﻴﺖ ﻣﺤﺘﺠﺰة ﻋﻠﻰ راﺳﺐ هﻴﺪروآﺴﻴﺪ اﻷﻟﻮﻣﻴﻨﻴﻮم ﺑﺴﻌﺔ ﻗﺪرهﺎ ﺣﻮاﻟﻲ ١٫٣٥ ﻣﺠﻢ ﻣﻮﻟﻴﺒﺪﻳﻨﻴﻮم /ﺟﻢ أآﺴﻴﺪ أﻟﻮﻣﻴﻨﻴﻮم.

وﻓﻲ ﺗﺠﺮﺑﺔ ﺑﺪﻳﻠﺔ ، ﺗﻢ ﺗﺤﻤﻴﺾ اﻟﻤﺤﻠﻮل اﻟﺮاﺋﻖ اﻟﻨﺎﺗﺞ ﺑﻌﺪ ﻋﻤﻠﻴﺔ ﺗﺮﺳﻴﺐ اﻟﺤﺪﻳﺪ ﺑﺤﻤﺾ اﻟﻨﻴﺘﺮﻳﻚ ﻟﺘﺮﺳﻴﺐ هﻴﺪروآﺴﻴﺪ اﻷﻟﻮﻣﻴﻨﻴﻮم ﻋﻨﺪ اﻷس اﻟﻬﻴﺪروﺟﻴﻨﻲ ٥. وﻗﺪ درﺳﺖ ﻣﺤﺎوﻻت اﺳﺘﺮﺟﺎع اﻟﻤﻮﻟﻴﺒﺪات -اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ اﻟﻤﺤﺘﺠﺰ ﺑﻐﺴﻞ رواﺳﺐ ﻣﻦ هﻴﺪروآﺴﻴﺪ اﻷﻟﻮﻣﻴﻨﻴﻮم اﻟﻤﺘﻜﻮﻧﺔ آﻞ ﻋﻠﻰ ﺣﺪة ﺑﻤﺤﺎﻟﻴﻞ ﻧﻴﺘﺮات اﻟﺼﻮدﻳﻮم ذات أس هﻴﺪروﺟﻴﻨﻲ ٥ و ٩٫٥ﺣﻴﺚ وﺟﺪ أن ﻧﺴﺒﺔ اﺣﺘﺠﺎز اﻟﺮاﺳﺐ اﻟﻤﺘﻜﻮن ﻟﻠﻤﻮﻟﻴﺒﺪات-اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ ﻓﻲ ﺣﺎﻟﺔ اﻷس اﻟﻬﻴﺪروﺟﻴﻨﻲ ٥

آﺎﻧﺖ ﻋﺎﻟﻴﺔ و ﺗﻘﺪرﺑﺤﻮاﻟﻰ ٤٠٧ و١٦٧ ﻣﺠﻢ ﻣﻮﻟﻴﺒﺪﻳ ﻨﻴﻮم/ ﺟﻢ أآﺴﻴﺪ اﻷﻟﻮﻣﻴﻨﻴﻮم ﻓﻲ ﺣﺎﻟﺘﻲ اﻟﺮاﺳﺒﻴﻦ اﻟﻤﻐﺴﻮﻟﻴﻦ ﺑﻤﺤﻠﻮﻟﻲ ﻧﻴﺘﺮات اﻟﺼﻮدﻳﻮم ذو اﻷس اﻟﻬﻴﺪوﺟﻴﻨﻲ ٥ و٩٫٥ ﻋﻠﻰ اﻟﺘﻮاﻟﻲ.

ﺗﻢ إﺟﺮاء ﺧﻄﻮة ﺗﻨﻘﻴﺔ ﺗﺎﻟﻴﺔ و اﺧﻴﺮﻩ ﻟﻤﺤﻠﻮل اﻟﻤﻮﻟﻴﺒﺪات -اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم -٩٩ (٣٫٥ ﻣﻮﻻر ﻧﻴﺘﺮات اﻟﺼﻮدﻳﻮم ذي أس هﻴﺪروﺟﻴﻨﻲ ٩٫٥) ﺑﺎﺳﺘﺨﺪام ﻋﻤﻮد آﺮوﻣﺎﺗﻮﺟﺮاﻓﻲ ﺻﻐﻴﺮﻣﻦ ﻣﺎدة ﺑﻮﺗﺎﺳﻴﻮم-ﻧﻴﻜﻞ هﻜﺴﺎﺳﻴﺎﻧﻮﻓﻴﺮات ﻋﻨﺪ درﺟﺔ ﺣﺮارة اﻟﻐﺮﻓﺔ ﺣﻴﺚ ﺗﺤﻘﻘﺖ اﻹزاﻟﺔ اﻟﻜﻤﻴﺔ ﻟﻠﻨﻮﻳﺪات اﻟﻤﺸﻌﺔ ﻟﻜﻞ ﻣﻦ اﻟﺴﻴﺰﻳﻮم -١٣٤ واﻷﻧﺘﻴﻤﻮن -١٢٤ واﻟﺮوﺑﻴﺪﻳﻮم -٨٦ ﺑﺎﻹﺿﺎﻓﺔ إﻟﻰ إزاﻟﺔ ﺣﻮاﻟﻲ ٥٠ % ﻣﻦ اﻟﻜﻮﺑﺎﻟﺖ -٦٠ اﻟﻤﺘﺒﻘﻲ ﺑﻐﺾ اﻟﻨﻈﺮ ﻋﻦ ﺗﺮآﻴﺰ اﻟﻤﻮﻟﻴﺒﺪات-اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم-٩٩ ﻓﻲ ﻣﺤﻠﻮل اﻟﺘﻐﺬﻳﺔ وﻣﻌﺪل ﺗﺪﻓﻘﻪ . وآﺎن ﻓﺎﻗﺪ اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم ﺳﺪاﺳﻰ اﻟﺘﻜﺎﻓﺆ ﻋﻠﻰ ١٫٠ ﺟ ﺮام ﻣﻦ ﻣﺎدة اﻟﻌﻤﻮد ﺻﻐﻴﺮ ﺟﺪا.

و ﻻﺧﺘﺒﺎر ﺟﻮدة اﻟﻤﻨﺘﺞ ﺑﻌﺪ ﺗﻨﻘﻴﺘﻪ ﺗﻢ ﺗﺮﺳﻴﺐ ﻣﺬاب اﻟﻤﻮﻟﻴﺒﺪات -اﻟﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم -٩٩ (اﻟﻨﺎﺗﺞ ﻓﻲ اﻟﻨﻬﺎﻳﺔ ﺑﻌﺪ ﻋﻤﻠﻴﺎت اﻟﺘﻨﻘﻴﺔ ) ﻋﻠﻰ هﻴﺌﺔ ﻣﺎدة ﺟﻞ ﻣﻮﻟﻴﺒﺪات اﻟﺰرآﻮﻧﻴﻮم ﻋﻨﺪ اﻷس اﻟﻬﻴﺪروﺟﻴﻨﻲ ٤٫٧. وﺗﻢ ﻏﺴﻴﻞ وﺗﺠﻔﻴﻒ وﺗﻬﻴﺌﺔ راﺳﺐ ﺟﻞ ﻣﻮﻟﻴﺒﺪات ا ﻟﺰرآﻮﻧﻴﻮم اﻟﺬي ﺗﻢ ﺗﺤﻀﻴﺮة و ﺗﻌﺒﺌﺘﻪ ﻋﻠﻰ هﻴﺌﺔ ﻋﻤﻮد آﺮﻣﺎﺗﻮﺟﺮاﻓﻲ ﻟﻴﺴﺘﺨﺪم آﻤﻮﻟﺪ ﻟﻠﻤﻮﻟﻴﺒﺪﻳﻨﻴﻮم -٩٩/اﻟﺘﻜﻨﻴﺴﻴﻮم-٩٩م . و اآﺪت ﻧﺘﺎﺋﺞ دراﺳﺎت رﻗﺎﺑﺔ اﻟﺠﻮدة ﻋﺎﺋﺪ ﻣﺮﺗﻔﻊ ﻻﺳﺘﺤﻼب اﻟﺘﻜﻨﻴﺴﻴﻮم-٩٩م ﺑﺎﻹﺿﺎﻓﺔ إﻟﻰ ﻧﻘﺎوة ﻧﻮوﻳﺔ إﺷﻌﺎﻋﻴﺔ وإﺷﻌﺎﻋﻴﺔ وآﻴﻤﻴﺎﺋﻴﺔ ﻋﺎﻟﻴﺔ ﻟﻤﺴﺘﺤﻠﺐ اﻟﺘﻜﻨﻴﺴﻴﻮم -٩٩م ﻣﻨﺎﺳﺒﺔ ﻻﺳﺘﺨﺪاﻣ ﻪ ﻓﻲ ﻣﺠﺎﻻت اﻟﻄﺐ اﻟﻨﻮوي.

اﻟﻤﺴﺘﺨﻠﺺ

ﻧﻈﻴﺮ اﻟﺘﻜﻨﺴﻴﻮم -٩٩م ﻣﻦ أهﻢ اﻟﻨﻈﺎﺋﺮ اﻟﻤﺸﻌﺔ اﻟﻤﺴﺘﺨﺪﻣﺔ ﻓﻰ اﻟﻄﺐ اﻟﻨﻮوى ﻓﻰ أﻏﺮاض اﻟﺘﺸﺨﻴﺺ. و ﻳﻌﺘﺒﺮ اﻟﻤﺼﺪر اﻟﻮﺣﻴﺪ ﻟﻠﺤﺼﻮل ﻋﻠﻴﻪ هﻮ ﻋﻤﻠﻴﺔ أﺿﻤﺤﻼل ﻧﻈﻴﺮ اﻟﻤﻮﻟﻴﺒﺪﻧﻴﻮم - ٩٩ ﻋﻦ ﻃﺮﻳﻖ أﻧﺒﻌﺎث ﺟﺴﻴﻤﺎت ﺑﻴﺘﺎ . أﻣﺎ اﻟﻤﻮﻟﻴﺒﺪﻧﻴﻮم -٩٩ ﻓﻨﺤﺼﻞ ﻋﻠﻴﻪ إﻣﺎ آﻨﺎﺗﺞ ﻣﻦ ﻧﻮاﺗﺞ اﻧﺸﻄﺎر اﻟﻴﻮراﻧﻴﻮم-٢٣٥ اﻟﻤﺸﻌﻊ أو ﻋﻦ ﻃﺮﻳﻖ ﺗﺸﻌﻴﻊ أهﺪاف اﻟﻤﻮﻟﻴﺒﺪﻧﻴﻮم اﻟﻤﺴﺘﻘﺮة ﺑﺎﻟﻨﻴﻮﺗﺮوﻧﺎت اﻟﺤﺮارﻳﺔ أو اﻟﻔﻮق ﺣﺮارﻳﺔ ﺑﺎﻟﻤﻔﺎﻋﻼت اﻟﻨﻮوﻳﺔ .و ﻧﻈﺮا ﻻﺳﺒﺎب ﻋﺪﻳﺪة أهﻤﻬﺎ اﻗﺘﺼﺎدﻳﺔ وﺗﻘﻨﻴﺔ ﻳﻌﺘﺒﺮ اﻟﻤﻮﻟﻴﺒﺪﻧﻴﻮم اﻟﻨﺎﺗﺞ ﻣﻦ اﻟﺘﻨﺸﻴﻂ اﻟﻨﻴﻮﺗﺮوﻧﻰ ﺑﺎﻟﻤﻔﺎﻋﻼت ﺑﺪﻳﻼ ﻋﻦ ﻧﻈﻴﺮﻩ ﻣﻦ ﻧﻮاﺗﺞ اﻧﺸﻄﺎراﻟﻴﻮراﻧﻴﻮم -٢٣٥. ﻳﺘﻢ ﺗﺤﻀﻴﺮ ﺟﻞ اﻟﻤﻮﻟﻴﺒﺪات ﻻﺳﺘﺨﺪاﻣﻪ ﻓﻰ ﻋﻤﻞ اﻟﻤﻮﻟﺪات ﺑﺘﺮﺳﻴﺐ ﻣﺤﻠﻮل اﻟﻤﻮﻟﻴﺒﺪات اﻟﻤﺸﻌﻊ ﻣﻊ آﺎﺗﻴﻮﻧﺎت اﻟﻌﻨﺎﺻﺮ اﻻ ﻧﺘﻘﺎﻟﻴﺔ ﻓﻰ وﺳﻂ ﺣﻤﻀﻰ. ﻟﻜﻦ اﻧﺘﺎج اﻟﻤﻮﻟﻴﺒﺪﻳﻮم -٩٩ ﺑﺎﻻﺳﺮ اﻟﻨﻴﻮﺗﺮوﻧﻰ ﻳﻜﻮن ﻣﺼﺤﻮﺑﺎ ﺑﺘﺸﻌﻴﻊ ﺑﻌﺾ اﻟﺸﻮاﺋﺐ اﻟﻤﺤﺘﻤﻞ وﺟﻮدهﺎ ﻓﻰ أهﺪاف اﻟﻤﻮﻟﻴﺒﻨﻴﻮ م ، و ﻏﻴﺮ اﻟﻤﺮﻏﻮب اﻧﺴﻴﺎﺑﻬﺎ ﻓﻰ اﻟﺘﻜﻨﺴﻴﻮم -٩٩م اﻟﻨﺎﺗﺞ ﻟﺨﻄﻮرﺗﻬﺎ ﻋﻨﺪ ﺣﻘﻨﻬﺎ ﻓﻰ اﻻﻧﺴﺎن ﻣﺜﻞ اﻟﺴﻴﺰﻳﻮم-١٣٤ واﻟﺴﻴﺮﻳﻮم-١٤١ واﻟﻜﺮوم-٥١ واﻹﻳﻮروﺑﻴﻮم-١٥٢ واﻟﻨﻴﻮﺑﻴﻮم-١٩٢م واﻟﺰرآﻮﻧﻴﻮم-٩٥/اﻟﻨﻴﻮﺑﻴﻮم-٩٥ واﻟﺰﻧﻚ-٦٥ واﻷﻧﺘﻴﻤﻮن-١٢٤ واﻟﻜﻮﺑﺎﻟﺖ -٦٠...اﻟﺦ. وﻟﺬﻟﻚ ﻳﺠﺐ اﺟﺮاء ﻋﻤﻠﻴﺎت ﺗﻨﻘﻴﺔ ﻣﺤﺎﻟﻴﻞ اﻟﻤﻮﻟﻴﺒﺪﻧﻴﻮم اﻟﻤﺸﻌﻌﺔ ﻗﺒﻞ اﺳﺘﺨﺪاﻣﻬﺎ ﻓﻰ اﻧﺘﺎج ﻣﻮﻟﺪات اﻟﻤﻮﻟﻴﺒﺪﻧﻴﻮم -٩٩ / ﺗﻜﻨﺴﻴﻮم-٩٩م آﺎﻟﺘﺎﻟﻰ: اوﻻ إ ذاﺑﺔ اﻟﻬﺪف اﻟﻤﺸﻌﻊ ﻣﻦ ﻣﺴﺤﻮق ﺛﺎﻟﺚ اآﺴﻴﺪ اﻟﻤﻮﻟﻴﺒﺪﻳﻮم اﻟﻤﻐﻠﻒ ﺑﻐﻼﻟﺔ ﻣﻦ اﻻﻟﻮﻣﻨﻴﻮم ﺑﺎﺿﺎﻓﺔ ﻣﺤﻠﻮل ٥ ﻣﻮﻻر ﻣﻦ هﻴﺪروآﺴﻴﺪ اﻟﺼﻮدﻳﻮم ﺛﻢ اﻻآﺴﺪ ﻩ ﺑﻌﺪ ﺗﻤﺎم اﻻذ اﺑﺔ ﺑﻤﺤﻠﻮل ﻓﻮق اآﺴﻴﺪ اﻟﻬﻴﺪروﺟﻴﻦ ﻷآﺴﺪة اﻟﺤﺪﻳﺪ اﻟﻤﻮﺟﻮد ﺑﻤﺎدة اﻻﻟﻮﻣﻨﻴﻮم اﻟﻰ هﻴﺪروآﺴﻴﺪ اﻟﺤﺪﻳﺪ (III) . و ﺣﻴﺚ ﺗﻌﻤﻞ ﺟﺰﻳﺌﺎت هﻴﺪروآﺴﻴﺪ اﻟﺤﺪﻳﺪ (III) آﺤﺎﻣﻞ ﻟﻠﺸﻮاﺋﺐ و اﻟﻨﻮﻳﺪات اﻟﻤﻮﺟﻮدة ﺑﺎﻟﻤﺤﻠﻮل. ﺗﺘﻢ ﻋﻤﻠﻴﺔ ﺗﻨﻘﻴﺔ آﺎﻣﻠﺔ ﻟﻨﻮﻳﺪات اﻟﺴﻴﺮﻳﻮم-١٤١ واﻹﻳﻮروﺑﻴﻮم-١٥٢و اﻟﻼﻧﺜﺎﻧﻴﻮم-١٤٠و واﻟﻨﻴﻮﺑﻴﻮم-١٩٢م و اﻟﻤﻨﺠﻨﻴﺰ-٥٤ اﻟﻰ ﺟﺎﻧﺐ اﻟﺘﻨﻘﻴﺔ اﻟﺠﺰﺋﻴﺔ ﻣﻦ ﺑﻌﺾ اﻟﺸﻮاﺋﺐ اﻻﺧﺮى آﺎﻟﻜﺮوم - ٥١ واﻟﻜﻮﺑﺎﻟﺖ -٦٠و اﻻﺳﻜﺎﻧﺪﻳﻮم -٤٦ و اﻟﺤﺪﻳﺪ -٥٩. ﺗﻢ ﺗﻌﺮﻳﻒ ﻧﻮاﺗﺞ ﺗﺤﻮﻻت اﻟﺤﺪﻳﺪ (III) اﻟﻰ ﻣﺪﻣﺼﺎت اﻻآﺎﺳﻴﺪ و هﻴﺪروآﺴﻴﺪات اﻻآﺎﺳﻴﺪ اﻟﻤﺨﺘﻠﻔﺔ ﻋﻨﺪ اﻟﻤﺘﻐﻴﺮات اﻟﻤﻌﻤﻠﻴﺔ اﻟﻤﺨﺘﻠﻔﺔ ودراﺳﺔ ﻣﻴﻜﺎﻧﻴﺰم اﻻدﻣﺼﺎص / و اﻻﺳﺘﺨﻼص ﻟﻜﻞ ﺣﺎﻟﺔ.

١ ﺛﺎﻧﻴﺎ اﺿﺎﻓﺔ ﺣﻤﺾ اﻟﻨﻴﺘﺮﻳﻚ اﻟﻤﺮآﺰ ﻟﺘﺮﺳﻴﺐ هﻴﺪروآﺴﻴﺪ اﻻﻟﻮﻣﻨﻴﻮم ﻋﻨﺪ رﻗﻤﻰ اﻻس اﻟﻬﻴﺪروﺟﻴﻨﻰ ٩،٥ و.،٥ ﻟﺘﻮاﻟﻰ ﻋﻤﻠﻴﺔ اﻟﺘﻨﻘﻴﺔ ﻣﻦ اﻟﺸﻮاﺋﺐ و اﻟﻨﻮﻳﺪات اﻟﻤﺘﺒﻘﻴﺔ ﺣﻴﺚ ﺗﻢ اﻟﺘﺨﻠﺺ ﻣﻦ اﻻﺳﻜﺎﻧﺪﻳﻮم-٤٦ و اﻟﺤﺪﻳﺪ -٥٩ و ﻣﻌﻈﻢ ﻧﻮﻳﺪات اﻟﻜﺮوم - ٥١ واﻟﻜﻮﺑﺎﻟﺖ -٦٠اﻟﻰ ﺟﺎﻧﺐ اﻟﺘﺨﻠﺺ ﻣﻦ آﻞ ﻧﻮﻳﺪات اﻟﺰرآﻮﻧﻴﻮم-٩٥/اﻟﻨﻴﻮﺑﻴﻮم -٩٥ﻣﻌﺎ واﻷﻧﺘﻴﻤﻮن -١٢٤و اﻟﺰﻧﻚ - ٦٥واﻟﻬﺎﻓﻨﻴﻮم ١٧٥و ١٨١. ﺗﻢ وﺿﻊ ﺗﺼﻮر ﺑﺴﻴﻂ ﻟﻤﻴﻜﺎﻧﻴﺰم اﻻدﻣﺼﺎص و اﻻﺳﺘﺨﻼص ﻣﻦ ﻋﻠﻰ ﺳﻄﺤﻰ اﻟﻤﺪﻣﺼﺎت اﻟﻤﻨﺎﻇﺮة. ﺛﺎﻟﺜﺎ ﻧﻮﻳﺪات اﻟﺴﻴﺰﻳﻮم -١٣٤ و اﻟﺮوﺑﻴﺪ ﻳﻮم-٨٦ ﺗﻢ اﻟﺘﺨﻠﺺ ﻣﻨﻬﺎ ﻋﻦ ﻃﺮﻳﻖ اﻣﺮار ﻣﺤﻠﻮل اﻟﻤﻮﻟﻴﺒﺪات ﻋﻠﻰ ﻋﻤﻮد آﺮوﻣﻠﺘﻮﺟﺮاﻓﻰ ﻣﻦ ﻣﺎدة اﻟﺒﻮﺗﺎﺳﻴﻮم ﻧﻴﻜﻞ هﻜﺴﺎﺳﻴﺎﻧﻮﻓﻴﺮات (II) اﻟﻤﺠﻬﺰ ﻣﻦ ﻗﺒﻞ ﻓﻰ ﻇﺮوف ﻣﻌﻤﻠﻴﺔ ﻣﻨﺎﺳﺒﺔ ﺑﻤﻴﻜﺎﻧﻴﺰم اﻟﺘﺒﺎدل اﻟﻜﺎﺗﻴﻮﻧﻰ . اﻟﻰ هﻨﺎ ﻧﻜﻮن ﻗﺪ ﻧﺠﺤﻨﺎ ﻓﻰ ﺗﻨﻘﻴﺔ ﻣﺤﻠﻮل اﻟﻤﻮﻟﻴﺒﺪات اﻟﻤﺸﻌﻊ ﻣﻦ آﻞ اﻟﺸﻮاﺋﺐ و اﻟﻨﻮﻳﺪات ﻏﻴﺮ اﻟﻤﺮﻏﻮﺑﺔ و اﻟﺨﻄﺮة ﻋﻨﺪ اﺳﺘﺨﺪاﻣﻬﺎ ﻓﻰ ﻋﻤﻞ ﻣﻮﻟﺪات ﺟﻞ اﻟﻤﻮﻟﻴﺒﺪﻧﻴﻮم-٩٩/ ﺗﻜﻨﺴﻴﻮم -٩٩م. ﺗﻢ ﺑﻌﺪ ذﻟﻚ ﺗﺮﺳﻴﺐ ﺟﻞ اﻟﺰرآﻮﻧﻴﻮم ﻣﻮﻟﻴﺒﺪات و ﻋﻤﻞ اﺧﺘﺒﺎرات اﻟﺠﻮدة ﻟﻤﺴﺘﺨﻠﺺ اﻟﺘﻜﻨﺴﻴﻮم-٩٩م اﻟﻨﺎﺗﺞ و اﺗﻀﺢ اﻧﻪ ﻋﺎﻟﻰ اﻟﻨﻘﺎوة اﻟﻨﻮوﻳﺔ و اﻟﻜﻴﻤﻴﺎﺋﻴﺔ واﻟﻜﻴﻤﻴﺎﺋﻴﺔ اﻻﺷﻌﺎﻋﻴﺔ و ﻣﻨﺎﺳﺐ ﻟﻼﺳﺘﺨﺪام ﻓﻰ اﻻﻏﺮاض اﻟﻄﺒﻴﺔ.

٢ ﺘﻨﻘﻴﺔ ﺍﻟﻤﻭﻟﻴﺒﺩﻨﻴﻭﻡ- ٩٩ ﻨﺎﺘﺞ ﺍﻟﺘﻨﺸﻴﻁ ﺍﻻﺸﻌﺎﻋﻰ ﺒﺎﻟﻨﻴﻭﺘﺭﻭﻨﺎﺕ ﻤﻥ ﺍﻟﻨﻭﻴﺩﺍﺕ ﺍﻟﻤﺘﺩﺍﺨﻠﺔ ﺒﺎﻟﻁﺭﻕ ﺍﻟﻜﺭﻭﻤﺎﺘﻭﺠﺭﺍﻓﻴﺔ

ﺭﺴﺎﻟﺔ ﻤﻘﺩﻤﺔ ﻤﻥ ﻤﺤﻤﻭﺩ ﺃﻤﻴﻥ ﻤﺤﻤﻭﺩ ﻤﺼﻁﻔﻰ (ﻤﺎﺠﺴﺘﻴﺭ ﻋﻠﻭﻡ ﺒﻴﺌﻴﺔ ٢٠٠٣ )

ﻗﺴﻡ ﺍﻟﻨﻅﺎﺌﺭ ﻭ ﺍﻟﻤﻭﻟﺩﺍﺕ ﺍﻟﻤﺸﻌﺔ. ﻤﺭﻜﺯ ﺍﻟﻤﻌﺎﻤل ﺍﻟﺤﺎﺭﺓ ﻫﻴﺌﺔ ﺍﻟﻁﺎﻗﺔ ﺍﻟﺫﺭﻴﺔ

ﻤﻘﺩﻤﺔ ﺍﻟﻰ ﻗﺴﻡ ﺍﻟﻜﻴﻤﻴﺎﺀ ﻜﻠﻴﺔ ﺍﻟﻌﻠﻭﻡ-ﺠﺎﻤﻌﺔ ﺤﻠﻭﺍﻥ

آﺠﺰء ﻣﺘﻄﻠﺐ ﻟﻠﺤﺼﻮل ﻋﻠﻰ درﺟﺔ دآﺘﻮراة اﻟﻔﻠﺴﻔﺔ ﻓﻰ اﻟﻌﻠﻮم ﺍﻟﻜﻴﻤﻴﺎﺀ ﻏﻴﺭ ﺍﻟﻌﻀﻭﻴﺔ ﻭﺍﻟﻔﻴﺯﻴﺎﺌﻴﺔ ﻭﺍﻟﺘﺤﻠﻴﻠﻴﺔ

٢٠١١

ﺘﻨﻘﻴﺔ ﺍﻟﻤﻭﻟﻴﺒﺩﻨﻴﻭﻡ- ٩٩ ﻨﺎﺘﺞ ﺍﻟﺘﻨﺸﻴﻁ ﺍﻹﺸﻌﺎﻋﻰ ﺒﺎﻟﻨﻴﻭﺘﺭﻭﻨﺎﺕ ﻤﻥ ﺍﻟﻨﻭﻴﺩﺍﺕ ﺍﻟﻤﺘﺩﺍﺨﻠﺔ ﺒﺎﻟﻁﺭﻕ ﺍﻟﻜﺭﻭﻤﺎﺘﻭﺠﺭﺍﻓﻴﺔ ﺭﺴﺎﻟﺔ ﻤﻘﺩﻤﺔ ﻤﻥ ﻤﺤﻤﻭﺩ ﺃﻤﻴﻥ ﻤﺤﻤﻭﺩ ﻤﺼﻁﻔﻰ ﻤﺎﺠﺴﺘﻴﺭ ﻋﻠﻭﻡ ﺒﻴﺌﻴﺔ ﺠﺎﻤﻌﺔ ﻋﻴﻥ ﺸﻤﺱ (٢٠٠٣) ﻗﺴﻡ ﺍﻟﻨﻅﺎﺌﺭ ﻭ ﺍﻟﻤﻭﻟﺩﺍﺕ ﺍﻟﻤﺸﻌﺔ. ﻤﺭﻜﺯ ﺍﻟﻤﻌﺎﻤل ﺍﻟﺤﺎﺭﺓ ﻫﻴﺌﺔ ﺍﻟﻁﺎﻗﺔ ﺍﻟﺫﺭﻴﺔ

٢٠١١

ﺘﺤﺕ ﺇﺸﺭﺍﻑ: ١- ﺃ.ﺩ/ ﻋﺒﺩ ﺍﻟﻔﺘﺎﺡ ﺒﺴﻁﺎﻭﻯ ﻓﺭﺝ-ﺃﺴﺘﺎﺫ ﺍﻟﻜﻴﻤﻴﺎﺀ ﻏﻴﺭﺍﻟﻌﻀﻭﻴﺔ ﻭ ﺍﻟﺘﺤﻠﻴﻠﻴﺔ ﻜﻠﻴﺔ ﺍﻟﻌﻠﻭﻡ- ﺠﺎﻤﻌﺔ ﺤﻠﻭﺍﻥ ٢- - ﺃ.ﺩ/ ﻤﺤﻤﺩ ﻋﺒﺩ ﺍﻟﺴﻼﻡ ﺍﻟﻌﺒﺴﻰ-ﺃﺴﺘﺎﺫ ﺍﻟﻜﻴﻤﻴﺎﺀ ﻏﻴﺭ ﺍﻟﻌﻀﻭﻴﺔ ﻭ ﺍﻹﺸﻌﺎﻋﻴﺔ ﻗﺴﻡ ﺍﻟﻨﻅﺎﺌﺭ ﻭ ﺍﻟﻤﻭﻟﺩﺍﺕ ﺍﻟﻤﺸﻌﺔ- ﻤﺭﻜﺯ ﺍﻟﻤﻌﺎﻤل ﺍﻟﺤﺎﺭﺓ- ﻫﻴﺌﺔ ﺍﻟﻁﺎﻗﺔ ﺍﻟﺫﺭﻴﺔ ٣- ﺃ.ﻡ.ﺩ/ ﻤﺤﻤﻭﺩ ﺍﺒﻭ ﺍﻟﻌﻴﻨﻴﻥ ﺍﻻﻤﻴﺭ- ﺃﺴﺘﺎﺫ ﻤﺴﺎﻋﺩ ﻓﻰ ﺍﻟﻬﻨﺩﺴﺔ ﺍﻟﻜﻴﻤﻴﺎﺌﻴﺔ ﺍﻹﺸﻌﺎﻋﻴﺔ ﺭﺌﻴﺱ ﻗﺴﻡ ﺍﻟﻨﻅﺎﺌﺭ ﻭ ﺍﻟﻤﻭﻟﺩﺍﺕ ﺍﻟﻤﺸﻌﺔ- ﻤﺭﻜﺯ ﺍﻟﻤﻌﺎﻤل ﺍﻟﺤﺎﺭﺓ- ﻫﻴﺌﺔ ﺍﻟﻁﺎﻗﺔ ﺍﻟﺫﺭﻴﺔ ٤- ﺩ/ ﺃﻤﻨﻴﺔ ﺍﺒﺭﺍﻫﻴﻡ ﻤﺤﻤﺩ- ﻤﺩﺭﺱ ﺍﻟﻜﻴﻤﻴﺎﺀ ﺍﻟﺘﺤﻠﻴﻠﻴﺔ ﻜﻠﻴﺔ ﺍﻟﻌﻠﻭﻡ- ﺠﺎﻤﻌﺔ ﺤﻠﻭﺍﻥ

AIM OF WORK

INTRODUCTION

EXPERIMENTAL METHODS

RESULTS AND DISCUSSION

LIST OF TABLES

LIST OF FIGURES

ABSTRACT

CONTENTS

اﻟﻤﺴﺘﺨﻠﺺ

اﻟﻤﻠﺨﺺ اﻟﻌﺮﺑﻰ

SUMMARY

REFERENCES