The Potentiometric and Laser RAMAN Study of the Hydrolysis of Uranyl

AECL-9266

ATOMIC ENERGY [/ \ fl L'ENERGIEATOMIQUE OF CANADA LIMITED \ #^4 '/ DU CANADA LIMITEE

THE POTENTIOMETRIC AND LASER RAMAN STUDY OF THE HYDROLYSIS OF URANYL CHLORIDE UNDER PHYSIOLOGICAL CONDITIONS AND THE EFFECT OF SYSTEMATIC AND RANDOM ERRORS ON THE HYDROLYSIS CONSTANTS

Etude de raman au potentiometre et au laser de I'hydrolyse du chlorure d'uranyle dans des conditions physiologiques et de I'effet des erreurs systematiques et aleatoires de constantes d 'hydrolyse

L.L. DESCHENES, G.H. KRAMER, K.J. MONSERRAT and P.A. ROBINSON

Chalk River Nuclear Laboratories Laboratoires nucleates de Chalk River

Chalk River, Ontario

December 1986 decembre ATOMIC ENERGY OF CANADA LIMITED

THE POTENTIOMETRIC AND LASER RAMAN STUDY OF THE HYDROLYSIS OF URANYL CHLORIDE UNDER PHYSIOLOGICAL CONDITIONS AND THE EFFECT OF SYSTEMATIC AND RANDOM ERRORS ON THE HYDROLYSIS CONSTANTS

L.L. Deschenes*, G-H. Kramer, K.J. Monserrat* and P.A. Robinson

*Systems Materials Branch Dosimetric Research Branch Chalk River Nuclear Laboratories Chalk River, Ontario KOJ 1JO 1986 December

AECL-9266 L'ENERGIE ATOMIQUE DU CANADA, LIMITEE

ETUDE DE RAMAN AU POTENTIOMETRE ET AU LASER DE L'HYDROLYSE DU CHLORURE D'URANYLE DANS DES CONDITIONS PHYSIOLOGIQUES ET DE L'EFFET DES ERREURS SYSTÉMATIQUES ET ALEATOIRES DE CONSTANTES D'HYDROLYSE

par

L.L. Deschenes*, G.H. Kramer, K.J. Monserrat* et P.A. Robinson

RÉSUMÉ

On a étudié l'hydrolyse des ions d'uranyle dans une solution de 0,15 mol/L de (Na)C1 à 37°C par titrage potentiométrique. Les résultats ont correspondu à la formation de (U02)2(OH)2, U03(0H)„, (U02)3(0H)5 et

(U02)„(0H)7. On a constaté que les constantes de stabilité, évaluées à l'aide d'une version de MINIQUAD, étaient: log ß22 = -5,693 ± 0,007, log

Ê3.» = -11,^99 + 0,024, log ß35 = -16,001 ± 0,050, log ß„7= -21,027 ± 0,051. On s'est servi de la spectroscopie de Raman au laser pour identifier les produits dont les espèces (U02 ),, (0H)7. En outre, on a étudié les difficultés d'identification des espèces chimiques en solution ainsi que l'effet des petites erreurs sur cette sélection par simulation sur modèle de calcul. Les résultats indiquent nettement que les petites erreurs peuvent conduire à la sélection d'espèces qui pourraient ne pas exister.

*Service des Matériaux de systèmes Service de Recherche en dosimétrie Laboratoires de Recherches de Chalk River Chalk River, Ontario KOJ 1J0 1986 décembre

AECL-9266 ATOMIC ENERGY OF CANADA LIMITED

THE POTENTIOMETRIC AND LASER RAMAN STUDY OF THE HYDROLYSIS OF URANYL CHLORIDE UNDER PHYSIOLOGICAL CONDITIONS AND THE EFFECT OF SYSTEMATIC AND RANDOM ERRORS ON THE HYDROLYSIS CONSTANTS

L.L. Deschenes*, G.H. Kramer, K.J. Monserrat* and P.A. Robinson

ABSTRACT

The hydrolysis of uranyl ions in 0.15 mol/L (Na)Cl solution at 37°C has been studied by potentiometric titration. The results were consistent with the formation of (UO2>2(OH)2> (UO2)3(OH)4»

(UO2)3(OH)5 and (UO2>4(OH)7. The stability constants, which were evaluated using a version of MINIQUAD, were found to be: log ".•: = -5.693 + 0.007, log 35,4 =-11.499 + 0.024, log r-35 = -16.001 j 0.050, log -7 = -21.027 +_ 0.051. Laser Raman spectroscopy has been used to identify the products including (UO2)4(OH)7 species. The difficulties in identifying the chemical species in solution and the effect of small errors on this selection has also been investigated by computer simulation. The results clearly indicate that small errors can lead to the selection of species that may not exist.

*Systems Materials Branch Dosimetric Research Branch Chalk River Nuclear Laboratories Chalk River, Ontario KOJ 1JO 1986 December

AECL-9266 INTRODUCTION

The hydrolysis of the uranyl ion has been studied over 30 years (e.g. references within reference 1). The bulk of these studies have been performed by potentiometric titration at 25°C and fixed ionic strength (0.1 to 3.0 mol/L). Other techniques for studying the uranyl hydrolysis include cryoscopy (2, 3), conductivity measurements (4), Raman spectroscopy (5, 6), dilution methods (7, 8) and kinetic methods (9). Other experimental conditions include a study of uranyl hydrolysis in heavy water (10) and temperatures other than 25°C (11-13).

The continued study of the uranyl-water system is probably explained by its complexity. The earlier studies agree in few things except that polynuclear hydrolytic ions are formed. Indeed, one can find postulates for species ranging from U02(0H)+ to (UO2)5(OH)g (14) with many differing intermediates. The popular theory of "core + link" (15) in which the hydrolysis is explained as an unlimited series UO2((OH)2 UO2) has been both criticized (12, 16) and later supported (2); however, in contrast to most of the earlier work, some recent Raman spectroscopic studies (5, 6) 2+ indicate that only U0 , (UO2)2(OH) t and (U02)3(0H)5 exist in nitrate solution. There was a minor contribution of (1102)3(011)3 also reported (5). Despite this evidence for only trimeric species being present there is still much evidence in the recent literature (17-19) for the inclusion of higher polynucleated species such as (U0)(0H)

The hydrolysis of the uranyl ion is undoubtedly complicated and sensitive to other components as is evidenced by the well documented medium effects (12, 16, 20) of chloride ion which give rise to the additional complex (1102)3(011)7. Milic (21) has attempted to explain this phenomenon in terms of "the factor of the medium" derived from the hydration energy, charge and concentration of the ions of the medium. Clearly then, this is an area yet to be resolved and each study performed under different conditions must stand alone.

This work has attempted to elucidate the hydrolysis of the uranyl ion under physiological conditions (37°C, 0.15 mol/L NaCl) as the precursor to further studies of uranium complexes in a physiological environment by both potentiometric titration and Laser Raman spectroscopy. The utilization of Laser Raman spectroscopy has proved to be an excellent method of experimentally verifying the chemical model suggested by the potentiometric titration. We report here for the first time the identification of

(UO2)4(OH)J species.

Additionally, we have performed a computer simulation to test the effect of small systematic and/or random errors on the chemical models selected. These results further substantiate the need for experimenters to attempt to verify their conclusions based on potentiometric titrations by an alternate physical method. - 2 -

EXPERIMENTAL

Reagents

Uranyl nitrate (depleted) was obtained from the Fisher Scientific Company and purified and converted to uranyl chloride as described elsewhere (18). Sodium chloride was purchased from Anachemia Limited as ACS reagent grade and was dried at 120°C for two hours and kept in a dessicator prior to use. Sodium hydroxide (Anachemia, reagent grade) was purified by preparing a 50% w/v aqueous solution maintained under a CO2 free atmosphere. Distilled deionized water ( >13 Mf2) was used for all reagents. Sodium hydroxide was standardized against potassium biphthalate (Baker analyzed reagent, dried before use). The standardized hydroxide was in turn used to standardize diluted doubly distilled hydrochloric acid. Uranium concentrations were estimated by standard gravimetric procedures (22). Sodium chloride solutions were prepared by weight. Air buoyancy corrections were applied to all weighings.

Titration Procedure

Titrations were performed using a Metrohm E655 piston buret controlled by a Hewlett-Packard HP-85 microcomputer. Hydrogen ion concentrations were measured as [HT*"] using an Orion Ross electrode and a Ross double-junction electrode, and a Metrohm pH-104 meter also controlled by the HP-85. The solution to be studied was titrated in a vessel similar to that described by Perrin and Sayce (23) which was thermostatted at 37°C (+ 0.1) by a Haake FK circulating water bath. Temperature within the cell was monitored using a model 2100 digital thermometer obtained from the H-B Instrument Company. Purified nitrogen gas was continually passed through the titration vessel to exclude CO2.

Each titration was preceded by an electrode calibration performed by titrating NaOH against HC1 with the same ionic background as the uranium hydrolysis determinations. Preliminary values of the standard electrode potential and ionization constant of water were obtained using a BASIC program, KW-IT, on the HP-85. These values verified the apparatus was performing correctly and that the hydrolysis determination could proceed. Further refinements of the data were performed on the Chalk River Nuclear Laboratories' (CRNL) main frame computers using FORTRAN77 programs.

Laser Raman Studies

Raman spectra were recorded on a conventional spectrometer. An Ar+ ion laser (Coherent) was used as the excitation source. A Spex 1403 double monochromator, equipped with photon counting electronics, was used to analyse the scattered Raman light. An RCA C31034, housed in a Peltier cooling jacket, was used. Spectra were recorded using the 514.5 nm line of the Ar+ laser. The beam was passed through a Spex Lasermate and focused onto the sample. To minimize sample degradation by laser heating incident beam power was limited to 200 mW. Scattered light was collected at 90°. The double monochromator was electronically tuned using the lines of a standard low pressure Hg lamp. The calibration and resolution of the instrument were checked - 3 - using CCI4. Samples examined by LR spectroscopy were taken directly from the titration cell, described above, and stored under nitrogen in sealed tubes.

RESULTS

Experimental Data

Preliminary Data Reduction

The reactions studied by this investigation can be summarized as follows:

2p q)+ + i (U02) (OH)J " + q H

The various species will be referred to by their formulae or by (p,q) pairs.

The titration data for each set of analytical conditions was converted to an average number of 0H~ bound by the UO^+ion, Z, as a function of [IT1"]. This is represented in Figure 1. Clearly the data shows polynucleation of the uranyl ion-hydroxide complexes from the dependence of Z on [UO 2"*] (24). The similarity in shape of the Z curves indicated that Z may be a function 2 + + t of [\JO 2 ]/[U ] . Further analysis yielded a value of t = 2 and the subsequent plot is shown in Figure 2. Analysis of this data (25) indicates that the primary hydrolysis product is (2, 2); however, the onset of precipitation limited the range of pH that could be studied such that it was not possible to reach a maximum Z value. No definitive information about higher polynucleated species can be obtained from Figure 2. The lack, of complete overlap in Figure 2 also indicates other major species to be present.

The data was analysed to determine the "average composition of species" as described by Sillen (26), see Figure 3. The plot indicates that a species lower than (2, 2) is formed but does not give a limiting higher polynucleated species. Other species of importance that can be inferred from Figure 3 are (3, 5) and (4, 7).

Computer Analysis of Data

The preliminary data suggest that (2, 2), (3, 5) and (4, 7) predominate in solution at different pH values. There may also be contributions from lower and higher polynucleated species. It was, therefore, decided to base the models around this group of complexes and attempt to explain the data in terms of a combination of (1, 1), (1, 2), (2, 1), (2, 2), (3, 3), (3, 4), (3, 5), (4, 6), (4, 7), (5, 8) and (5, 9). The summary of the model calculation is shown in Table 1. A model was rejected if any of the values become negative and the remaining models are compared on the basis of the residual, the standard deviation of 3 and chemical common sense. Laser Raman Spectroscopy

Raman spectroscopy was performed on solutions of UO2CI2 in the pH range 2 to 5.1; however, no useful spectra could be collected above pH 4 because the solutions precipitated when placed in the laser beam. We have no indication of what photochemical reaction was taking place at this time. The spectra collected clearly shows the UO ; + peak (871 cm"1) at pH 2.0. This peak decreases in intensity as hydrolysis occurs until at pH 4.0 it is a minor contribution to the spectrum. Other peaks appear and grow in intensity with increasing pH until at pH 4.0 there are contributions from the polynuclear hydrolysis products. These spectra are shown in Figure 4.

Synthetic Data

Using the hydrolysis constants in model 13 the experimental data was simulated as follows. The experimental parameters (analytical concentrations, E°, temperature) were used to determine the free concentrations of [ff*"] , [UO „"*] and the complexes at a known volume of base added during the titration. Once the free [H+] was known the simulated electrode potential was simply calculated. The free concentrations were calculated using some of the subroutines within MINIQUAD.

The synthetic data (generated in part by MINIQUAD) was then reanalyzed by MINIQUAD after it had been altered by the program, KERROR, to include any combination of the following: systematic error in E°, systematic error in the titrate volume, random error in the electrode reading, random error in the volume of base added. The data was analysed using the model which had originally generated it and also by a totally different model. The results are shown in Tables 2 and 3.

DISCUSSION

Potentiometrie

The hydrolysis of the uranyl ion apparently begins with dimerisation forming (UO2)2(OHJ^~ as is indicated from the good overlap shown in Figure 2. The value of t = 2 indicates that the first major hydrolysis should be this dimer. As the pH increases Z appears to tend to a limit of approximately 2 which is consistent with such species as (U02)3(0H)g, (UO2)4(OH)g, etc. The lack of an accurate upper limit on Z precludes any definitive assignment to higher polynucleated species in this pH region.

More information can be gained from the graph of the "average composition of species" (26), Figure 3. It can be clearly seen that the following species fall on or close to the straight line: (2, 2), (3, 5) and (4, 7). The lowest limit of the line indicates that perhaps some simpler species such as 1,1 are also formed; however, we have been unable to find any computational evidence for these types of hydrolysis products. Even if they are formed their contribution to the overall picture is not significant. This point will be discussed later. - 5 -

The models shown in Table 1 were devised from the above reasoning. Despite the fact that other independent methods (5, 6) claim that species higher than (3, 5) cannot be present, our work (and that of many others) indicates that higher polynucleation does exist. Table 1 offers several models that describe the data quite adequately. On the basis of the residual sum of squares the models may be ranked in order of beet to worst as 23-26, 20, 21, 14, 13, 11, 7, 6, 1, 2, 4. A closer examination, however, reveals that the standard deviations of the log Bpn values are large and in some cases large enough ( >0.2) to indicate that the species does not exist (27). On this basis we car. eliminate models 23, 26, 20, 21, 11 and 4. Clearly then, the data is best described by models 14, 13, 6 and 1. Model 1 can be eliminated on the basis of the high residual. Model 14 does not make a great deal of chemical sense as there is no indication from Figure 3 that the polynucleation greatly exceeds 4. Model 13 is, therefore, selected as the best descriptor for the hydrolysis of the uranyl ion in sodium chloride solution. These results also substantiate earlier work (12, 16, 20) that demonstrated the formation of the (3, 4) complex in the presence of the chloride ion. However, Sylva and Davidson maintain that the formation of the (3, 4) complex is independent of the medium (17) and is perhaps only enhanced by the presence of chloride ions.

Table 1 clearly shows that the (1, 1) species is absent (model failed); however, it was possible to force the (1, 1) to "exist" by fixing the values for the equilibrium constants in model 13 and optimizing on the (1, 1) species. The model did not fail and a reasonable convergence achieved (residual sum of squares = 2.89 x 10"^). The equilibrium constant for the (1, 1) was found to be log f\ll = -5.675 + 0.173.

Considering the differences in experimental conditions, this result is statistically indistinguishable from the value (log 3n = -5.4 +0.4) obtained from thermodynamic properties by Lemire and Tremaine (28) and similar to other values obtained at 25°C in various media (18). These results do not substantiate nor rule out the existence of the (1, 1) complex under our experimental conditions; however, an examination of the species distribution including the (1, 1) complex reveals its relative unimportance. The (1, 1) complex never exceeds 3% formation.

The species distribution for model 13 is shown in Figure 5. The (2, 2) complex is initially formed and remains predominant until the pH reaches about 4.2. The (3, 5) complex becomes briefly predominant but is quickly overwhelmed by the increasing amount of higher polynucleated species, in this case, the (4, 7) complex. As the uranium concentration decreases the species distribution also shifts. The formation of the (3, 5) complex becomes more important and complex formation does not occur at low pH. Ultimately at uranium concentrations above 10~5 mol/L, the predominance of the (2, 2) complex is from approximately pH 4.0, where complex formation begins in appreciable quantities, to approximately pH 5.0. At high pH values the (3, 5) complex predominates until precipitation occurs. The major difference between high and low uranium concentrations is the relative amount of (3, 4) formed. In the former case it is a significant species over the pH range 4-5 but at low uranium concentrations its contribution is slight indeed. - 6 -

Figure 5 has been extended well beyond the pH region that uranium precipitates. It can be seen that if the hydroxides were soluble the higher polynucleated species would predominate. This is also true for low (10"-' mol/L) uranium concentrations but the calculations show high polynucleation would not greatly occur until above pH 7 (30% formation of (4, 7)) well above the precipitation point. Undoubtedly this is the cause of the diverse composition of uranium hydroxide precipitation observed elsewhere (29).

Laser Raman Data

The potentiometric data suggested that polynucleation of the U02 ion exceeded 3. The Laser Raman experiments were performed in order to prove this supposition either correct or incorrect. It is exceedingly unfortunate that we could not obtain any spectroscopic data above pH 4 due to the photochemical precipitation; however, we do observe a new band in the Raman spectrum that has not previously been reported.

The uranyl ion is clearly unhydrolyzed at pH 2.0 as can be seen from Fig. 4 (873 cm"1). As the pH rises to 3.8 other major hydrolysis products can be seen at 856 cm"! and 831 cm"-'-. Based on previous work (5) these bands are assigned to the (2, 2) and (3, 5) complexes, respectively. Finally at pH 4.1 another peak is found at a lower frequency.

It has already been demonstrated (5) that the frequency decreases as the polynucleation increases and the uranyl bonds are weakened by the added hydroxyl ligands; furthermore, a comparison of the species distribution at pH = 4.0 with the relative intensities (area) of the peaks shown in Fig. 3 (c). The species distribution predicts the following approximate relative percentages: (1, 0), 34% (2, 2) 41%, (3, 4) 11%, (3, 5) 9%, (4, 7) 4%._ The relative peak areas are as follows: 872 cm"1 37%, 855 cm"1 47%, 832 cm"1 6.5%, 820 cm"1 6.1%, 812 cm"1 3%. Considering the relative difficulty in deconvoluting the partially resolved Raman spectrum, this is excellent agreement.

Synthetic Data

The analysis of the synthetic data is displayed in Tables 2 and 3. Table 2 is divided into three subsections. The first two subsections are for the model (1, 1), (2, 2), (3, 4), (3, 5), (4, 6) and (4, 7) and the third subsection is for the model (2, 2), (3, 4), (3, 5), (5, 8) and (5, 9). Each entry consists of the residual sum of squares at convergence with rejected species in parentheses to the right of that value. The perfect data, EE = VE = ER = VR = 0, gives the residual 4.78 x 10"8 with the rejection of # (1, 1) and (4, 6), as it should, but a closer examination of the matrix shows that good residuals can be obtained when the errors are substantial, i.e. EE = 1 rav, VE = 3.0 mL, residual = 5.2 x 10~7 and rejection of (1, 1) and (4, 6). The main conclusion that can be drawn from Table 3 is that MINIQUAD remains fairly tolerant of errors. On the whole the spurious species, (1, 1) and (4, 6), are usually rejected; however, it is clear that the absolute value of the residual is a reasonable indication of the fitness - 7 -

of the total data set. The lower portion of Table 2 shows clearly that the synthetic data generated by one set of hydrolysis constants can be fitted extremely well (residual = 4.72 x KT8 VE = EE = NR = ER = 0) by a different set of constants. This exemplifies one of the reasons why the hydrolysis of the uranyl ion has given so many diverse models after analysis.

Obviously the residual is not the final answer. Table 3 shows the standard deviation on log 3 for the lower set of residuals in ascending order. Again it is clear that data is relatively insensitive to small systematic and/or random errors. In most cases the spurious species (1, 1) and (4, 6) are rejected or have large standard deviations which cast doubt on their existence. The second portion of Table 3 shows that the incorrect set of hydrolysis constants fits the synthetic data exceedingly well. Clearly, without other evidence no definitive decision between the models can be made solely on the basis of residuals and standard deviations. REFERENCES

1. J.E. Grindler, "Handbook of Experimental Pharmacology", Chapter 2, XXXVI, H.C. Hodge, J.N. Stannard and J.B. Hursh (Eds.). Springer-Verlag. New York/Hendlberg/Berlin, 1973.

2. D.V.S. Jain, CM. Jain and R.N. Vaid, J. Chem. Soc. A. 915, 1967.

3. J. Sutton, J. Inorg. Nucl. Chem. 1_, 68, 1955.

4. K.Ii. Schmidt, J.C. Sullivan, S. Gordon and R.C. Thompson, Inorg. Nucl. Chem. Lett. 14_, 429, 1978.

5. L.M. Toth and G.M. Begun, J. Phys. Chem. 85_, 547, 1981.

6. M. Asano and J.A. Koningstein, Can. J. Chem. 60_, 2207, 1982.

7. B.P. Nikolskii and V.l. Paramonova, Zh. Fiz. Khim. _2_, 687, 1931.

8. A.S. Perskin, Radiokhimiya 25^, 404, 1983.

9. D.L. Cole, E.M. Eyring, D.T. Rampton, A. Silzars and R.P. Jensen, J. Phys. Chem. 71_, 2771, 1967.

10. M. Maeda and H. Kakihana, Bull. Chem. Soc. Japan 43_, 1097, 1970.

11. R. Robbins, J. Inorg. Nucl. Chem. 28_, 119, 1966.

12. C.F. Baes and N.J. Meyer, Inorg. Chera. JL, 780, 1962.

13. J.A. Hearne and A.G. White, J. Chem. Soc. 2168, 1957.

14. A. Peterson, Acta. Chem. Scand. J_5_, 101, 1961.

15. L.G. Sillen, Acta. Chem. Scand. 8_, 299, 318, 1954.

16. R.M. Rush, J.S. Johnson and K.A. Kraus, Inorg. Chem. 1^ 378, 1962.

17. R.N. Sylva and M.R. Davidson, J. Chem. Soc. Dalton 465, 1979.

18. N.B. Milic and G. El Kass, Bull. Soc. Chim. Beograd, 44_, 275, 1979.

19. L.H. Lajunen and S. Parhi, Finn Chem. Lett. 143, 1979.

20. R.M. Rush and J.S. Johnson, J. Phys. Chem. 6]_, 821, 1963.

21. N.B. Milic, J. Chem. Soc. Dalton 229, 1973.

22. A.I. Vogel, "Textbook of Quantitative Inorganic Analysis", 4th Edition, Longmans Group Ltd., New York, 1981. 23. D.D. Perrin and I.G. Sayce, Chem. Ind. 661, 1966.

24. F.J.C. Rossotti and H. Rospotti, "The Determination of Stability Constants", McGraw-Hill, New York, 1961.

25. C.F. Baes and R.E. Mesmer, "The Hydrolysis of Cations", Wiley-Interscience, New York, 1976.

26. L.G. Sillen, Acta. Chera. Scand. 15, 1981, 1961.

27. A. Braibainti and C. Bruschi, Annal. Chim. _6_7_, 471, 1977.

28. R.J. Lemire and P.R. Tremaine, J. Chem. Eng. Data 25_, 361, 1980.

29. J. Maly and V. Vesely, J. Inorg. Nucl. Chem. ]_, 119, 1958.

30. M. Aberg, Acta. Chem. Scand. 24, 2701, 1970. - 10 -

TABLE 1

SUMMARY OF MODELS USED TO FIT EXPERIMENTAL DATA

10 Residual Sum ID Model -log 8 100 of Squares

1 (2, 2) 5.574 .006 0 .11 9.01 (3, 5) 15.599 .008 0.05

2 (2, 2) 5.430 .025 0 .46 200.00 (3, 6) 20.256 .046 0 .23

3 (2, 2) Mcdel Failed

4 (2, 2) 6.227 .180 299.7 (3, 4) 11.058 .039 j i 5 (1, 1) (2, 2) Model Failed (3, 5)

6 (2, 2) 5.724 .035 0 .61 i (3, 3) 15.602 .007 0 .04 7.74 i (3, 5) 7.579 .089 1.17 i 7 (2, 2) 5.651 .008 0 .14 (3, 4) 15.690 .009 0 .05 4.49 (3, 5) 11.261 .032 0 ,27

8 (2, 2) (3, 5) Model Failed (3, 6)

I 9 (2, 2) (3, 4) Model Failed (3, 5) (3, 6)

10 (1, 1) (2, 2) Model Failed (3, 4) (3, 5)

11 (2, 2) 5.732 .025 0.44 (3, 3) 7.863 .132 1.68 4.16 (3, 4) 11.788 .034 0.29 (3, 5) 15.686 .009 0.06 - 11 -

TABLE 1 (Continued)

1 1 10 Residual Sum ID Model -log B °R 100 p °B/B of Squares T

12 (2, 2) (3, 4) Model Failed (3, 5) (3, 6)

13 (2, 2) 5.693 .007 0.12 (3, A) 11.499 .024 0.21 9 7Q j (3, 5) 16.001 .050 0.31 /. • / y (4, 7) 22.027 .051 0.23

14 (2, 2) 5.683 .007 0.12 (3, 4) 11.562 .022 0.19 o 7O (3, 5) 15.812 .017 0.11 (5, 9) 28,334 .053 0.19

15 (2, 2) (3, 3) (3, 4) Model Failed (3, 5) I 1 (3, 6) | 16 (2, 2) (3, 3) (3, 4) Model Failed (3, 5) I (4, 6)

17 (2, 2) i j (3, 3) (3, 4) Model Failed I (3, 5) (4, 7)

18 (2, 2> j (3, 4) 1 (3, 5) Model Failed (4, 6) (4, 7)

19 (2, 2) (3, 4) (3, 5) Model Failed <4, 6) (5, 8) - 12 -

TABLE 1 (Continued)

10 Residual Sum ID Model -log B Or, 100 3 3/3 of Squares

20 (2, 2) 5.665 .008 0.14 (3, 4) 11.673 .047 0.40 (3, 5) 15,969 .062 .39 2.51 (4, 6) 17,520 .143 0.82 (5, 9) 28.146 .061 0.22

21 (2, 2) 5.691 .007 0 .12 (3, 4) 11.457 .026 0.23 (3, 5) 16.387 .337 2.06 2.58 (4, 7) 21.903 .053 0.24 (5, 8) 23.490 .174 0.74 1 22 (2, 2) I (3, 4) (3, 5) Model Failed (4, 7) (5, 9)

23 (2, 2) 5.683 .007 0.12 (3, 4) 11.508 .024 0 21 (3, 5) 16.067 .102 0 .63 2.43 (5, 8) 23.332 .129 0 55 (5, 9) 28.143 .058 0 21

24 (2, 2) (3, 4) (3, 5) Model Failed (4, 6) (4, 7) (5, 9)

25 (2, 2) (3, 4) (3, 5) Model Failed (4, 7) (5, 8) (5, 9)

26 (2, 2) 5.680 .011 0.19 (3, 4) ! 11.253 .064 0.57 (3, 5) i 16.067 .097 0.60 (A, 6) 18,308 > 1 > 5 2.43 (5, 8) 23.383 .241 1.03 (5, 9) 28.136 .064 0.23 TABLE 2 (a)

EFFECT OF SYSTEMATIC AND RANDOM ERRORS ON THE RESIDUAL SUM OF SQUARES AND ACCEPTANCE OF POSTULATED SPECIES

VR = 0

VE ER EE => 0 EE - 1 EE = 2 EE = 3 EE = 4 EE = 5

0 .47800E-7(l,l:4,6) .14695E-4(1,1:4,6) .26346E-4(1,1:4,6) .56393E-4(1,1:4,6) .96O29E-4(1,1:4,6) .14413E-3(1,1:4,6) 0 1 .2479E-5(1,1:4,6) .86509E-5U, 1:4,6) .27O74E-4(1,1:4,6) .56399E-4(1,1:4,6) .95392E-4(1,1:4,6) .1429E-3(1,1:4,6) 2 .98781E-5U.1) .14694E-4(1,1:4,6) .31892E-4(1,1:4,6) .60113E-4(l,l:4,6) .9811OE-4(1,1:4,6) .14775E-3(1,1:4,6) I 0 .34891E-6(4,6) .39257E-5(1,1:4,6) .19740E-4(l,l:4,6) .46498E-4(1,1:4,6) .82966E-4(1,1:4,6) .12802E-3(l,l:4,6)

1 1 .29921E-5(4,6) .56769E-5(1,1:4,6) .2O677E-4(1,1:4,6) .46706E-4(l,l:4,6) .82522E-4(1,1:4,6) .12699E-3(1,1:4,6) 2 .10636E-4(4,6) .11963E-4(1,1:4,6) .25729E-4(1,1:4,6) .50643E-4(l,l:4,6) .85455E-4(1,1:4,6) .12902E-3(l,l:4,6)

0 .14562E-5(4,6) .17476E-5(1,1:4,6) .14216E-4Q, 1:4,6) .37751E-4(1,1:4,6) .71114E-4(1,1:4,6) .11317E-3(1,1:4,6) 2 1 .43062E-5(4,6) .37114E-5(1,1:4,6) .15358E-4(1,1:4,6) .38155E-4(1,1:4,6) .70859E-4(l,1:4,6) .U233E-3(1,1:4,6) 2 .1219E-4(4,&) .10236E-4(l,l:4,6) .20638E-4(l,l:4,6) .42312E-4(1,1:4,6) .74003E-4(l,l:4,6) .11456E-3(1,1:4,6)

0 .3320E-5(4,6) .52321E-6(1,1:4,6) .97124E-5(1,1:4,6) .30088E-4(l,l:4,6) ,60408E-4(l,l:4,6) .99536E-4(1,1:4,6) 3 1 ,63735E-5(4,6) .26950E-5(l,l) .11054E-4(l,l:4,6) .30685E-4(l,l:4,6) ,60338E-4(l,l:4,6) .98871E-4(1,1:4,6) 2 .14494E-4(4,6) ,94526E-5(1,1) .16558E-4(1,1:4,6) .35056E-l(l,l:4,6) .63688E-4(1,1:4,6) .10130E-3(l,l:4,6) TABLE 2 (b)

EFFECT OF SYSTEMATIC AND RANDOM ERRORS ON THE RESIDUAL SUM OF SQUARES AND ACCEPTANCE OF POSTULATED SPECIES

VR = .1

VE ER EE = 0 EE = 1 EE - 2 EE = 3 EE = 4 EE = 5

0 .20319E-5(l,l:4,6) .89089E-5(l,l:4,6) .27953E-4(1,1:4,6) .57821E-4(1,1:4,6) .97286E-4(1,1:4,6) .14522E-3(1,1:4,6) 0 1 .4730E-5(4,6) . 10698E-4U, 1:4,6) .28925E-4(1,1:4,6) .58O61E-4(1,1:4,6) .96871E-4(1,1:4.6) .14422E-3(1,1:4,6) 2 .12390E-4(-) .16992E-4U,1:4,6) .33983E-4(1,1:4,6) .62003E-4(l,l:4,6) .99808E-4(l,l:4,6) .14626E-3(1,1:4,6)

1 0 .23391E-5(4,6) .57365E-5(1,1:4,6) .21368E-4(1,1:4,6) .47950E-4(l,l:4,6) .84248E-4(l,i:4,6) .12914E-3(1,1:4,6) 1 1 .52453E-5(4,6) .774O8E-5(1,1:4,6) .22547E-4(1,1:4,6) .48388E-4(1,1:4,6) .84025E-4(l,l:4,6) .12832E-3(1,1:4,6) 2 .13148E-4(4,6) .14276E-4(1,1:4,6) .27837E-4(1,1:4,6) .52553E-4(1,1:4,6) .87175E-4(1,1:4,6) .13056E-3(l,l:4,6)

0 .34512E-5(4,6) .35759E-5(1,1:4,6) .15864E-4(1,1:4,6) .39225E-4(1,1:4,6) .72420E-4(l,l:4,6) .11432E-3(1,1:4,6) 1 .65618E-5(4,6) .57906E-5(l,l:4,6) .17246E-4(1,1:4,6) .39858E-4(1,1:4,6) .72385E-4(1,1:4,6) .11369E-3(1,1:4,6) 2 .14702E-4(4,6) .12562E-4(1,1) .22761E-4(1,1:4,6) .4424OE-4(1,1:4,6) .75744E-4(1,1:4,6) .116123E-3(1,1:4,6)

0 .5320E-5(4,6) .23676E-5(1,1:4,6) .U378E-4(1,1:4,6) .31582E-4(1,1:4,6) .61737E-4Q,1:4,6) .10071E-3(l,l:4,6) 1 .86317E-5(4,6) .47881E-5(1,1) .l2958E-i(l,l:4,6) .32406E-4(l,l:4,6) .61884E-4(1,1:4,6) .10O25E-3(l,1:4,6) ! 3 .17007E-4(4,6) .117898E-4(1,1) .18696E-4(1,1:4,6) .37001E-4(l,l:4,6) .65448E-4U,1:4,6) .10288E-3(l,l:4,6) TABLE 2 (c)

EFFECT OF SYSTEMATIC AND RANDOM ERRORS ON THE RESIDUAL SUM OF SQUARES AND ACCEPTANCE OF POSTULATED SPECIES

VR = 0

VE ER I EE = 0 ' EE = 1 EE = 2 EE = 3 EE = 4 EE = 5

0 ' .47169E-7(5,8) .71351E-5 .26384E-4(5,8) .5645lE-4(5 ,8) .96109E-4(5,8) .14423E-3C5 ,8) 0 2 .98655E-5(5,8)

.39659E-6(5,8) .39395E-5(5,8) .19773E-4(5,8) .46551E-4(5 ,8) .83040E-4(5,8) .128UE-3(5 ,8) I .10695E-4(5,8) .11964E-4(5,8) .25748E-4(5,8) .50681E-4(5 ,8) .85514E-4(5,8) o , .16883E-5(5,8) .17573E-5(5,8) .14245E-4(5,8) .3779E-4(5, 8) .71182E-4(5,8) .U326E-3C5 ,8) 2 2 ' .10234E-4(5,8) .20653E-4(5,8) .42346E-4(5 ,8) ,74056E-4(5,8)

0 .3865-E-5(5,8) .52903E-6(5,8) .37798E-4(5,8) .3O13OE-4(5 ,8) .60470E-4(5,8) .99619E-4(5 ,8) 3 - 16 -

TABLE 3 (a)

STD DEVIATION ON LOG 3 VE EE VR ER S. OF SQUARES 1, 1 2, 2 3, 4 3, 5 4, 6 4, 7

0 0 0 0 .47800E-7 R .002 .01 .005 R .01 1 0 0 0 .34891E-6 .07 .01 .04 .01 R .03 3 1 0 0 .52321E-6 R .006 .04 .02 R .04 2 0 0 0 .14562E-5 .06 .03 .15 .03 R .06 2 1 0 0 .17476E-5 R .01 .08 .03 R .07 0 0 .1 0 .20319E-5 R .01 .06 .04 R .09 1 0 .1 0 .23391E-5 .18 .03 .09 .04 R .09 3 1 .1 0 .23676E-5 R .01 .07 .04 R .09 0 0 0 1 .2479E-5 R .01 .08 .04 R .09 3 1 0 1 .26950E-5 R .02 .18 .05 >1 .13 1 0 0 1 .29921E-5 .20 .04 .14 .04 R .09 3 0 0 0 .3320E-5 .06 .06 1.0 .04 R .08 2 0 .1 0 .34512E-5 .096 .04 .16 .05 R .10 2 1 .1 0 .35759E-5 R .02 .09 .05 R .12 ; 2 1 0 1 .37114E-5 R .02 .11 .05 R .11 i l 1 0 0 .39257E-5 R .02 .13 .05 R .10 2 0 0 1 .43062E-5 .11 .05 .30 .05 R .10 0 0 .1 1 .4730E-5 >1 .04 .10 .07 R .15 3 1 .1 1 .47881E-5 R .02 .19 .08 >1 .21 1 0 .1 1 .52543E-5 .25 .05 .14 .07 R .15 3 0 .1 0 .5320E-5 .08 .07 .38 .06 R .11 1 1 0 1 .56769E-5 R .02 .15 .06 R .13 1 1 .1 0 .57365E-5 R .02 .12 .06 R .15 2 1 .1 1 •57906E-5 R .02 .11 .07 R .16 3 0 0 1 .63735E-5 .09 .09 .21 .06 R .11 2 0 .1 1 .65618E-5 .13 .06 .23 .07 R .15 1 1 .1 1 .774O8E-5 R .02 .13 .07 R .18 - 17 - TABLE 3 (a) (Continued)

STD DEVIATION ON LOG 3 VE EE VR ER S. OF SQUARES 1, 1 2, 2 3, 4 3, 5 4, 6 4, 7

3 0 .1 1 .86317E-5 .10 .10 .54 .08 R .15 0 1 0 1 .86509E-5 R .02 .20 .07 R .16 0 1 .1 0 .89089E-5 R .02 .15 .08 R .19 3 1 0 2 .94526E-5 R .03 .45 .11 >1 .29 0 0 0 2 .98781E-5 R .03 .39 .11 >1 .29 - 18 -

TABLE 3 (b)

STD DEVIATION ON LOG 6 EE VR ER S. OF SQUARES i 2, 2 3, 5 3, 4 5, B 5, 9

0 0 0 0 .47168E-7 .002 .003 .005 R .01 l 0 0 0 .39659E-6 .005 .010 .014 R .04 3 1 0 0 .529O3E-6 .005 .012 .017 R .04 2 0 0 0 .16883E-5 .009 .02 .03 R .08 2 1 0 0 .17573E-5 .010 .02 .03 R .08 3 0 0 0 .3865OE-5 .014 .03 .05 R .14 1 1 0 0 .39395E-5 .015 .03 .04 R .12 0 1 0 0 .71351E-5 .02 .05 .06 R .17 0 0 0 2 .9865E-5 .02 .05 .08 R .23 - 19 -

FIGURE 1

The average number of bound hydroxyl ions, ZBAR, as a function of pH. - 20 -

I I I I I I I I I I

1.0 2.0 3.0 4.0 5.0 6.0 7.0 2 log ([uo2]/[H] )

FIGURE 2

The average number of bound hydroxyl ions, ZBAR, as a function of

+ + 2 log [U02 ,/tH ] - 21 -

1 -

FIGURE 3

MESAK diagram for the predominant species (UO ) (OH) in solution. - 22 -

en •z.

800 850 900 RAMAN SHIFT (cm"1)

FIGURE 4

Laser Raman spectra of the uranyl hydrolysis products lower curve, pH = 2.2, [UOJ[ ] = 0.0073 mol/L; middle curve, pH = 3.8, [U0i+] = 0.0069 mol/L; upper curve, pH = 4.1, [U02+] = 0.0092 tnol/L. All spectra corrected for background and smoothed. 2 - 23 -

o CD o C3 o Ox ao o (VI 1V13N

FIGURE 5 Species distribution of the uranyl hydrolysis products. 2+ [U02 ] = o.Ol mol/L. ISSN 0067-0367 ISSN 0067-0367

To identify individual documents in the series Pour identifier les rapports tndividuels faisant we have assigned an AECL- numberto each. partie de cette serie nous avons assigne unnumeroAECL- achacun.

Please referto the AECL- number when re- Veuillezfaire mention du numeroAECL- si questing additional copies of this document vous demandez d'autres exemplaires de ce rapport

from au

Scientific Document Distribution Office Service de Distribution des Documents Officiels Atomic Energy of Canada Limited L'EnergieAtomiquedu Canada Limitee Chalk River, Ontario, Canada Chalk River, Ontario, Canada K0J1J0 KOJ1JO

Price: A Prix: A

319-86