Electrochemical extraction of gadolinium on Sn electrode and preparation of Sn-Gd intermetallic compounds in LiCl-KCl melts

Abstract

For the development of nuclear energy, it is important to remove the fission products which hinder nuclear reactions. In this paper, Gd was extracted by an electrochemical method in LiCl-KCl molten salts. The electrochemical reactions of GdCl3 and SnCl2 are measured by a series of electrochemical means. Three kinds of Sn-Li and four Sn-Gd alloys are obtained by cyclic voltammetry and other electrochemical means. Thermodynamic and kinetic parameters of electrode processes for Gd(III) and Sn(II) ions are calculated by different electrochemical test methods. The diffusion coefficient and diffusion activation energy of the Sn(II) ion are reactions as 2.23–3.78 × 10-5 cm2 s-1 and 24.4 kJ mol-1, respectively. Thermodynamic parameters of Sn3Gd intermetallic compounds were calculated based on open circuit chronopotentiometry at different temperatures (ΔHf0(Sn3Gd)=−229.225kJmol-1 and ΔSf0(Sn3Gd)=−38.2Jmol-1K-1). Metallic Gd is extracted by potentiostatic and galvanostatic electrolysis on liquid Sn electrode in melts, respectively. According to X-ray diffraction (XRD) and scanning electron microscopy and elemental dispersive spectrometry (SEM-EDS), the products are mainly composed of the intermetallic compound Sn3Gd and Sn metal. The experimental results show that the fission element Gd can be extracted with high extraction rate by electrolysis in molten salt system.