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

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....

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Bibliographic Details
Published in:European journal of inorganic chemistry 2006-01
Main Authors: Di Bernardo, Plinio, Zanonato, PierLuigi, Bismondo, Arturo, Jiang, Huijian, Garnov, Alexander Yu, Jiang, Jun, Rao, Linfeng
Format: Article
Language:English
Subjects:
CALORIMETRY
ELECTROSTATICS
ENTHALPY
POTENTIOMETRY
SOLVENTS
SPECIFIC HEAT
THERMODYNAMICS
URANIUM
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Summary: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.
ISSN:1434-1948
1099-0682