Complexation of uranium(VI) and samarium(III) with oxydiacetic acid: temperature effect and coordination modes.
Complexation of uranium(VI) and samarium(III) with oxydiacetic acid: temperature effect and coordination modes.
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DOI：
10.1021/ic034227h
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发表时间：
2003-05
影响因子：
4.6
通讯作者：
L. Rao;A. Garnov;Jun Jiang;P. Di Bernardo;P. Zanonato;A. Bismondo
中科院分区：
文献类型：
--
作者：
L. Rao;A. Garnov;Jun Jiang;P. Di Bernardo;P. Zanonato;A. Bismondo
The complexation of uranium(VI) and samarium(III) with oxydiacetate (ODA) in 1.05 mol kg(-1) NaClO(4) is studied at variable temperatures (25-70 degrees C). Three U(VI)/ODA complexes (UO(2)L, UO(2)L(2)(2-), and UO(2)HL(2)(-)) and three Sm(III)/ODA complexes (SmL(j)((3-2)(j)+) with j = 1, 2, 3) are identified in this temperature range. The formation constants and the molar enthalpies of complexation are determined by potentiometry and calorimetry. The complexation of uranium(VI) and samarium(III) with oxydiacetate becomes more endothermic at higher temperatures. However, the complexes become stronger due to increasingly more positive entropy of complexation at higher temperatures that exceeds the increase in the enthalpy of complexation. The values of the heat capacity of complexation (Delta C(p) degrees in J K(-1) mol(-1)) are 95 +/- 6, 297 +/- 14, and 162 +/- 19 for UO(2)L, UO(2)L(2)(2-), and UO(2)HL(2)(-), and 142 +/- 6, 198 +/- 14, and 157 +/- 19 for SmL(+), SmL(2)(-), and SmL(3)(3-), respectively. The thermodynamic parameters, in conjunction with the structural information from spectroscopy, help to identify the coordination modes in the uranium oxydiacetate complexes. 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.
