Electrochemical behavior of tungsten ions from WC scrap dissolution in a chloride melt

This paper presents a novel method of electrochemical extraction of tungsten from tungsten carbide (WC) scrap in the molten NaCl-KCl salt. WC was used as a consumable anode and dissolved electrochemically to extract tungsten at 1023 K. In this method, the kinetics of the WC anode was analyzed through linear polarization and electrochemical impedance spectroscopy (EIS). Electrochemical techniques, such as cyclic voltammetry (CV), chronopotentiometry (CP), square wave voltammetry (SWV), and chronoamperometry, were employed to investigate the electrochemical behavior of tungsten ions derived from the WC anode in the melt. Results confirmed that the redox reaction of tungsten on a platinum working electrode is reversible; this reaction was controlled through tungsten ion diffusion in the electrolyte. During reduction, a stable electro-active species was detected through CP and SWV. Electrochemical reduction of tungsten ions proceeded in one step with two exchanged electrons. The nucleation mode of tungsten deposition was also determined. Chronoamperometry results revealed that electro-deposition follows progressive nucleation with a three-dimensional nuclei growth. After galvanostatic electrolysis, the deposition was analyzed through X-ray diffraction and scanning electron microscopy. Results verified the formation of pure tungsten powders with a diameter of <100 nm at a cathodic current density of 0.125 A cm(-2). (C) 2015 Elsevier Ltd. All rights reserved.