Electrolytic reduction mechanism of Np(V) and the effect of coexisting nitric acid

The behaviors of reduction of NpO2+ by controlled potential electrolysis were studied, and a unique time course of electrolysis current was observed. It was concluded that NpO2+ was reduced by two reduction processes, which were the chemical reaction with Np3+and the electrocatalytic reduction by adsorbed hydrogen atom on platinum electrode surface. The time courses of current for controlled potential electrolysis of NpO2+ under various conditions of the solution were investigated, and the effects of the concentration of H+ and NO3- on electrolysis behavior were explained by proposed reduction mechanisms. The Np4+was prepared from NpO2+ in 3 mol dm-3 HNO3 by electrolytic reduction at the potential where evolution of hydrogen gas and reduction of NO3- were inhibited. The electrolysis efficiency could be improved.