Protonation and complexation of isosaccharinic acid with U(VI) and Fe(III) in acidic solutions: potentiometric and calorimetric studies

Verfasser / Beitragende:
[Linfeng Rao, Alexander Yu. Garnov, Dhanpat Rai, Yuanxian Xia, Robert C. Moore]
Ort, Verlag, Jahr:
2004
Enthalten in:
Radiochimica Acta/International journal for chemical aspects of nuclear science and technology, 92/9-11/2004(2004-11-01), 575-581
Format:
Artikel (online)
ID: 378927418
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024 7 0 |a 10.1524/ract.92.9.575.54970  |2 doi 
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245 0 0 |a Protonation and complexation of isosaccharinic acid with U(VI) and Fe(III) in acidic solutions: potentiometric and calorimetric studies  |h [Elektronische Daten]  |c [Linfeng Rao, Alexander Yu. Garnov, Dhanpat Rai, Yuanxian Xia, Robert C. Moore] 
520 3 |a Protonation and complexation of α-isosaccharinic acid with U(VI) and Fe(III) have been studied in acidic solutions at t=25°C and I=1.0mol dm-3 NaClO4. From the potentiometric titrations, the protonation constant of the carboxylate group is calculated to be 3.65±0.05 and the data are consistent with the presence of three and four successive mononuclear complexes for U(VI) and Fe(III), respectively. The formation constants of the complexes, log βj for the reactions of M+L=MLj where j=1-3 for U(VI), j=1-4 for Fe(III) and L stands for isosaccharinate, are determined to be 2.91±0.15 (UO2L), 5.37±0.07 (UO2L2), 7.25±0.18 (UO2L3), 5.06±0.17 (FeL), 8.51±0.15 (FeL2), 11.00±0.16 (FeL3), and 12.99±0.17 (FeL4). From the calorimetric titrations, the enthalpy of protonation of the carboxylate group is determined to be -(7.94±0.03)kJ mol-1, similar to that of other α-hydroxycarboxylates. The enthalpies of complexation between U(VI) and isosaccharinate are quite small: Δ H1 = -(1.0±1.0)kJ mol-1, Δ H2=1.4±1.8kJ mol-1 and Δ H3=-(6.2±3.0)kJ mol-1, typical of the interactions between carboxylates and hard-acid cations. The complexation between U(VI) and isosaccharinate is mainly entropy-driven. In comparison, the enthalpies of complexation for FeL3 and FeL4 are large and exothermic, contributing significantly to the stability of the complexes. 
540 |a © 2004 Oldenbourg Wissenschaftsverlag GmbH 
690 7 |a Laboratory techniques, experiments  |2 nationallicence 
690 7 |a Analytical chemistry  |2 nationallicence 
690 7 |a Inorganic chemistry  |2 nationallicence 
700 1 |a Rao  |D Linfeng  |4 aut 
700 1 |a Garnov  |D Alexander Yu  |4 aut 
700 1 |a Rai  |D Dhanpat  |4 aut 
700 1 |a Xia  |D Yuanxian  |4 aut 
700 1 |a Moore  |D Robert C.  |4 aut 
773 0 |t Radiochimica Acta/International journal for chemical aspects of nuclear science and technology  |d Oldenbourg Wissenschaftsverlag GmbH  |g 92/9-11/2004(2004-11-01), 575-581  |x 0033-8230  |q 92:9-11/2004<575  |1 2004  |2 92  |o ract 
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950 |B NATIONALLICENCE  |P 700  |E 1-  |a Garnov  |D Alexander Yu  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Rai  |D Dhanpat  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Xia  |D Yuanxian  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Moore  |D Robert C.  |4 aut 
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