Electrochemical separation of tungsten from scrap cemented carbide WC in FLiNaK melt

Abstract

Molten salt electrolysis is an innovative technology applied to recover tungsten from the scrap of cemented carbide, which enables the realization of energy saving and consumption reduction goals. Currently, numerous studies have focused on the molten salt electrolysis of chlorine salt systems, but still face challenges including low electrolysis efficiency and salt volatilization. Here, we propose to employ the FLiNaK molten salt system for recovering tungsten from the scrap cemented carbide and analyze the feasibility of the dissolution of WC occurring at the anode from the perspective of thermodynamics and electrochemical polarization curves. Moreover, the influence of electrolysis temperature on the dissolution of the anode is also investigated and the productions are identified as nano-flake tungsten powder by characterizing the cathode product using XRD, SEM, EDS, and XPS. A two-step reduction mechanism of W ions was analyzed by electrochemical means such as CV, SWV, etc., and the ionic groups stabilized by W6+ and W4+, and F− in the molten salts were deduced to be WF33+ and WF3+ by DFT simulation calculations. This work provides new guidance for the application of molten salt electrolysis in the recovery of tungsten from scrap cemented carbide.