Mechanism and Kinetics of Rh(IV) Radiation-Chemical Reduction in HNO3 Solutions

Reduction of Rh(IV) in γ-irradiated and nonirradiated solutions of HNO3 (0.3-3.0 M) was studied. In both systems, Rh(IV) is completely reduced to Rh(III). The reduction rates in nonirradiated solutions amount to 50-90% of rates in irradiated solutions. Reduction of Rh(IV) with water is postulated. The rates of Rh(IV) reduction in both irradiated and nonirradiated solutions increase with [Rh(IV)] growth and decrease with an increase in [HNO3] from 0.5-1 to 2-3 M. The dependence of the reduction rates on the dose rate is weak. Mathematical simulation was used to reveal the mechanism and kinetics of radiation-chemical reduction of Rh(IV) in HNO3 solutions. The rate constant of Rh(IV) reduction with water was calculated by fitting to the experimental data.