ZnCl2 and Liquid Zinc Assisted Electrochemical Extraction of Thulium from LiCl–KCl Melt

Abstract

This work presents a study of the electrochemical behavior of Tm at liquid Zn electrode in LiCl–KCl–TmCl3 melt and the co-reduction of Zn, Li and Tm on W electrodes in LiCl–KCl–ZnCl2–TmCl3 melt at 753 K. The deposition potential of Tm in liquid Zn material was found to be 0.9 V more positive than that at a solid W electrode. In LiCl–KCl–ZnCl2–TmCl3 melt, five Zn–Tm intermetallic compounds were detected in Zn-coated W electrode by cyclic voltammetry and chronopotentiometry. Extraction of Tm was carried out on a W electrode in LiCl–KCl–ZnCl2–TmCl3 melt and at liquid Zn electrode in LiCl–KCl–TmCl3 melt. The obtained deposits showed Tm2Zn17 phase. The morphology and micro-zone chemical analysis of the deposits was characterized by scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). The composition of the deposits was analyzed by inductive coupled plasma atomic emission spectrometer (ICP-AES). The deposits obtained at W and liquid Zn electrodes were composed of 50.6 wt% and 22.3 wt% Tm, respectively.