학술논문
Complexation of Uranium(Vl) by Gluconate in Acidic Solutions: a Thermodynamic Study with Structural Analysis.
Document Type
Article
Author
Source
Subject
*URANIUM compounds
*COMPLEX compounds
*STRUCTURAL analysis (Science)
*NUCLEAR magnetic resonance spectroscopy
*CHEMICAL bonds
*ACTINIDE elements
*THERMODYNAMICS research
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Language
ISSN
0020-1669
Abstract
Within the pCH range of 2.5 to 4.2, gluconate forms three uranyl complexes UO2(GH4)+, UO2(GH3)(aq), and UO2(GH3)(GH4)-, through the following reactions: (1) UO22+ + GH4- = UO2(GH4)+ (2) UO22+ + GH4 = UO2(GH3)(aq) + H+, and (3) UO22+ + 2GH4- = UO2(GH3)(GH4) + H+. Complexes were inferred from potentiometric, dalorimetric, NMR, and EXAFS studies. Correspondingly, the stability constants and enthalpies were determined to be log β1 = 2.2 ± 0.3 and ΔH1 = 7.5 ± 1.3 kJ mol-1 for reaction (1), log β2 = -(0.38 ± 0.05) and ΔH2 15.4 ± 0.3 kJ mol-1 for reaction (2), and log β3 = 1.3 ± 0.2 and ΔH3 = 14.6 ± 0.3 kJ mol-1 for reaction (3), at I = 1.0 M NaClO4 and t = 25 °C. The UO2(GH4)+ complex forms through the bidentate carboxylate binding to U(Vl). In the UO2(GH3)(aq) complex, hydroxyl-deprotonated gluconate (GH32-) coordinates to U(Vl) through the five-membered ring chelation. For the UO2(GH3)(GH4)- complex, multiple coordination modes are suggested. These results are discussed in the context of trivalent and pentavalent actinide complexation by gluconate. [ABSTRACT FROM AUTHOR]