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Complexation of Uranium(VI) with Thiodiacetic Acid in Solution at 10–85 °C
Author(s) -
Di Bernardo Plinio,
Zaato PierLuigi,
Bismondo Arturo,
Jiang Huijian,
Garnov Alexander Yu.,
Jiang Jun,
Rao Linfeng
Publication year - 2006
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200600554
Subject(s) - chemistry , protonation , endothermic process , enthalpy , uranium , calorimetry , standard enthalpy of formation , solvent , inorganic chemistry , stability constants of complexes , heat capacity , standard enthalpy change of formation , atmospheric temperature range , aqueous solution , thermodynamics , organic chemistry , ion , adsorption , physics , materials science , metallurgy
Abstract The protonation of thiodiacetate and its complexation with uranium(VI) in 1.05 mol kg –1 NaClO 4 are studied at variable temperatures (10–85 °C). Three U VI complexes (UO 2 L, UO 2 HL + , and UO 2 HL 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 (Δ C p °) are 122 ± 16, 302 ± 26, and 242 ± 23 J K –1 mol –1 for UO 2 L, UO 2 HL + , and UO 2 HL 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)