Electrochemical behavior and separation of Ce(III) in LiCl-KCl molten salt

Abstract

In order to improve the utilization of spent fuel, molten salt electrolysis is used to separate lanthanides from spent fuel. The electrochemical reduction mechanism of Ce(III) ions and dynamic properties of Ce(III)/Ce(0) were provided in the LiCl-KCl molten salt by diversified electrochemical techniques. The diffusion coefficient of Ce(III) and the exchange current densities of Ce(III)/Ce(0) on the W electrode were calculated by cyclic voltammetry and linear polarization, and the reaction activation energy was calculated to be 30.8 kJ∙mol−1. The electrochemical behaviors were measured in the LiCl-KCl-CeCl3-K2ZrF6 molten salt on the W electrode and LiCl-KCl-CeCl3 molten salt on the Zr electrode at 753 K. The redox mechanism of Ce(III) ions was studied on the Zr electrode. Compared the reaction at different electrodes, the reduction potential of cerium on the Zr electrode is more correct than that on the W electrode, the underpotential displacement of cerium and zirconium due to the formation of alloy is 0.26 V, which was detecteted using cyclic voltammetry, square wave voltammetry and chronopotentiometry. In addition, the feasibility of extracting Ce on the Zr electrode by potentiostatic electrolysis at −1.9 V and −2.2 V in the LiCl-KCl molten salt. The cathodic deposition output was characterized by XRD and SEM-EDS, Ce-Zr solid solution was derived under the different conditions. Simultaneously, the Ce metal was discovered when the deposition potential at −2.2 V. The ICP-OES results showed that the extraction ratio of was about 94.02 % for Ce(III) after potentiostatic electrolysis at −2.2 V for 5 h.