On the radiolytic oxidation of U(IV) to U(VI) in H2SO4 and HCl media

The radiolytic oxidation of U(IV) to U(VI) has been investigated in H2SO4 and HCl media and the radiolytic yield, G[U(VI)] has been determined at various concentrations of U(IV) both in aerated and deaerated solutions. It has been found that G[U(VI)] increases with increasing concentration of U(IV) and ultimately attains a limiting value of 9.2 in aerated H2SO4 and 7.8 in aerated HCl medium, whereas in deaerated H2SO4 the limiting value reduces to 2. In deaerated HCl medium G[U(VI)]sub(vac) has been found to increase from 0.4 to 1.3 over the range of the concentration of U(IV) investigated. The oxidation of U(IV) by Cl2- in HCl medium has been confirmed by flash photolysis and the production of OH radicals in the reaction between U(IV) and H2O2, has been supported by the studies using benzene as scavenger. A mechanism consistent with the results has been proposed. (author)