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.