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A. S. A. Khan, Riaz Ahmed, M. L. Mirza
Kinetics and electrochemical studies of uranium in acetate and formate media by cyclic voltammetry
Keywords: Uranium, Acetate, Formate, Kinetics, Thermodynamics
The cyclic voltammetric behavior of uranyl ion was investigated at hanging mercury drop electrode in perchlorate supporting electrolyte. The standard heterogeneous electron transfer rate constant “ks” for the reduction of uranyl ion in perchlorate medium was (2.74±0.03)×10-3 cm s-1 while in acetate and formate medium the value of ks was (2.83±0.02)×10-3 and (2.66±0.02)×10-3 cm s-1, respectively. The effect of temperature on the values of ks was investigated and thermodynamic constants ΔH*, ΔS* and ΔG298* were evaluated. The values of ΔH*, ΔS* and ΔG298* were 8.06±0.03 kJ mol-1, -23.42±0.05 J mol-1 K-1 and 15.02±0.07 kJ mol-1 in simple perchlorate medium and 3.67±0.02 kJ mol-1, -38.04±0.05 J mol-1 K-1, and 15.01±0.03 kJ mol-1 in acetate medium and 0.79±0.02 kJ mol-1, -48.24±0.04 J mol-1 K-1 and 15.17±0.02 kJ mol-1 in formate medium, respectively. The thermodynamic data showed that the process of reduction of uranyl ion at hanging mercury drop electrode was endothermic and non-spontaneous. The stability constants of uranyl acetate and uranyl formate were calculated from an analysis of the shift in peak potential data. The logβ1 and logβ2 values for 1:1 and 1:2 uranyl acetate complexes were 2.67±0.04 and 4.71±0.01, respectively. The values of logβ1 and logβ2 of uranyl formate complex were 1.61±0.02 and 2.57±0.01, respectively, which are reported for the first time.
Radiochimica Acta, Oldenbourg Wissenschaftsverlag
Print ISSN: 0033-8230
Volume: 95, 12/2007
Pages: 693 - 699