The kinetics of the oxidation-reduction reaction between uranium(VI) and titanium (III) in HCl solution

The oxidation-reduction reaction between U(VI) and Ti(III) in HCl solution was studied spectrophotometrically. The reaction is second-order at all concentrations of reactants, HCl, ferrous chloride and mannitol used in this work. In 5M HCl the rate constant k increases with increasing Ti(III) concentration, whereas it decreases with increasing U(VI) concentration, with increasing HCl concentration from 1.00M to 7.17M and increases thereafter from 7.17M to 11.79M. The addition of mannitol causes a consistent decreases in the rate of reaction, whereas ferrous chloride chloride has no effect. The activation energy for this oxidation-reduction reaction was 47.90 ± 0.11 kJ x mol-1. The values of δH≠, δG≠ and δS≠ were 45.40 ± 0.11 kJ x mol-1 and -91.10 ± 0.22 J x k-1 x mol-1, respectively. The mode of reaction is discussed in the light of kinetic results. (author) 23 refs.; 8 figs.; 2 tabs