Kinetics of the oxidation of U (IV) by hydrogen peroxide in sulfuric acid medium

✍ Scribed by P. K. Bhattacharyya; R. D. Saini; P. B. Ruikar

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 612 KB
• Volume: 13
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550130405

✦ Synopsis

T h e kinetics of the reaction (1) U (IV) + H202 UO;' + 2H+ have heen investigated in HzSO4 medium under different conditions. 'The observed bimolecular rate constant kobs, has been found to depend on [H+]-'l.ss and to increase with the initial concentration ratio of the reactants Ro = [H20~]o/[U (IV)],) above 0.49. T h e activation energy of the overall reaction has been determined a s 13.79 and 14.3 kcal/mol a t Ro = 1 and 0.35, respectively. Consistent with experimental data, a detailed reaction mechanism has been proposed where the hydrolytic reaction (4) followed by the rate-controlling reaction (10) and subsequent fast reactions of U (V) and O H radicals are involved: (4) LJ(so~)~+ + H ~O 3 u(so,)(oH)+ + H + I;

(10) U(SO4)(0H)+ + HnOr+IJ(SO4)(0H)Z + OH A kinetic expression has been derived from which a graphical evaluation of ( k K d ) -' and k-' has been made a t Ro = 1 as (12.30 f 0.09) X M min; and a t Ro = 0.35as (12.63 f 2.13) X 1W3 M min, (8.32 f 6.62) X M min, respectively. Indications of some participation of a chain reaction a t Ro = 1 have been obtained without affecting the second-order kinetics a s observed.