Direct electrolytic separation of tungsten and cobalt from waste cemented carbide and electrochemical behavior of tungsten and cobalt ions in NaF–KF molten salts

Abstract

In this study, WC–10Co cemented carbide scrap was used as a consumable anode to separate and prepare tungsten and cobalt powders in NaF–KF melts at 1073K. The feasibility of direct electrochemical dissolution of WC main phase to produce metallic tungsten was analyzed by thermodynamic calculations and experimental verifications. Furthermore, a series of electrolysis experiments were performed under constant cell voltage for selective preparation of tungsten and cobalt powders. The results show that metal cobalt powder was obtained at ≤0.6V whereas metal tungsten powder was produced between 0.6V and 1.2V. The analysis of cathode products using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) show that tungsten and cobalt powders can be prepared in NaF–KF melts. Finally, linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were used to investigate the dissolution of WC–10Co anode. The electrochemical properties of tungsten and cobalt ions in NaF–KF melts were studied by cyclic voltammetry (CV) and square wave voltammetry (SWV). The results show that WC–10Co anode could be used to produce tungsten and cobalt powders and the electroreduction of tungsten and cobalt ions in NaF–KF melts was achieved through a one-step reaction involving the transfer of two electrons.