Electrochemical Behavior and Extraction of CE on Liquid Sn Cathode in Lif-Licl Eutectic

Abstract

The electrochemical investigation of Ce(III) was carried out on W, Sn film and liquid Sn electrodes in LiF-LiCl eutectic by a variety of electrochemical methods. It was determined that Ce(III) was reduced to metallic Ce on W electrode via a one-step three-electron transfer, which was a quasi-reversible process controlled by diffusion. The diffusion coefficient of Ce(III) in LiF-LiCl eutectic was estimated by CV and CP, while the diffusion activation energy was calculated to be 20.86 kJ mol-1 and 20.95 kJ mol-1, respectively. The electrochemical behavior of Ce(III) was studied on Sn film electrode by CV and OCP. Eight alloy compounds CexSn could be prepared because of the underpotential deposition of Ce on the pre-deposited Sn film electrode. The activities of Ce in CexSn and standard Gibbs formation energies of CexSn were evaluated, respectively. Moreover, on Sn film electrode, the electrochemical extraction of Ce was performed at -1.5 V. XRD, SEM and EDS results exhibited the formation of CeSn3 and Ce2Sn5. The electrochemical extracting Ce was also conducted on liquid Sn electrode at -1.3 V, CeSn3 was obtained. In addition, the extraction rates and efficiencies of Ce on liquid Sn electrode were estimated using ICP-AES at different durations. It was found that as the extraction proceeded, the extraction rate decreased, while the extraction efficiency increased. The extraction efficiency reached over 98% after electrolysis for 10 h.

Keywords: LiF-LiCl, Liquid Sn electrode, Electrochemical extraction, Thermodynamic properties, Ce-Sn Alloy