Electrochemical Recovery of Uo2 from Licl-Kcl-Uo2f2 Molten Salt

Abstract

To recover UO2 from LiCl-KCl-UO2F2 molten salt, the electrochemical behavior of UO22+ and nucleation mechanism of UO2 were studied by a series of electrochemical methods. The results of cyclic voltammetry and square wave voltammetry showed that UO2 was formed through two-step reduction process of UO22+ involving one electron transfer. The disproportionation reaction of UO2+ was investigated by calculating electric charge, demonstrating the disproportionation reaction occurred as 2UO2+=UO22++UO2. The exchange current densities of UO2+/UO2  couple were determined at various temperatures by Tafel technique, and their values increased with the increasing temperature, which was in accordance with the Arrhenius equation, therefore, the activation energy of the reaction was estimated to be 32.21 kJ mol-1. Meanwhile, the nucleation mechanism of UO2 was investigated to follow the progressive nucleation by chronoamperometry. Furthermore, potentiosatic electrolysis was performed at various applied potentials, and the results indicated that UO2 had a regular octahedral microstructure, and the applied potential affected the size of UO2crystal.

Keywords: Electrochemical recovery, UO22+, exchange current density, nucleation mechanism, UO2