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Complexation of Uranium(VI) with Thiodiacetic Acid in Solution at10 - 85oC

Journal Article · · European Journal of Inorganic Chemistry
OSTI ID:918820
The protonation of thiodiacetate and its complexation with uranium(VI) in 1.05 molkg{sup -1} NaClO{sub 4} are studied at variable temperatures (10-85 C). Three UVI complexes (UO{sub 2}L, UO{sub 2}HL{sup +}, and UO{sub 2}HL{sup 2-}, where L is thiodiacetate) are identified in this temperature range. The formation constants and the enthalpies of complexation are determined by potentiometry and calorimetry. The complexation of uranium(VI) with thiodiacetate becomes more endothermic at higher temperatures. However, the complexes become stronger due to increasingly more positive entropies of complexation at higher temperatures, which exceeds the increase in the unfavorable enthalpy of complexation. The values of the heat capacity of complexation ({Delta}Cp) are 122{+-}16, 302{+-}26, and 242{+-}23 JK{sup -1} mol{sup -1} for UO{sub 2}L, UO{sub 2}HL{sup +}, and UO{sub 2}HL{sup 2-}, respectively. The effect of temperature on the thermodynamics of the complexation is discussed in terms of the electrostatic model and the change in the solvent structure.
Research Organization:
COLLABORATION - U. diPadova/Italy
DOE Contract Number:
AC02-05CH11231
OSTI ID:
918820
Report Number(s):
LBNL--61629; BnR: KC0302030
Journal Information:
European Journal of Inorganic Chemistry, Journal Name: European Journal of Inorganic Chemistry Vol. 0; ISSN EJICFO; ISSN 1434-1948
Country of Publication:
United States
Language:
English

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