Ming Li,Xiaoli Xi,Zuoren Nie,Liwen Ma,Qingqing Liu
The recycling of WC–Co hard metal scraps has been taken into consideration in the literature, due to the release of toxic substances and long recovery process. In this study, the recovery of tungsten process, based on the molten salt electrolysis treatment of WC–Co hard metal scraps, was developed. The anode polarization curves were applied to investigate the dissolution of the WC–Co hard metal scrap. Then, the electrochemical behavior of tungsten and cobalt ions dissolved from WC–Co scrap anode, was studied by cyclic voltammetry (CV) and square wave voltammetry (SWV). The results demonstrated that the reduction of tungsten and cobalt ions occurred through a one-step process involving the transfer of two electrons. This process was achieved by the diffusion of tungsten and cobalt ions in the melts. Finally, the parameters, such as the electrolysis current, the electrolysis duration and temperatures, were applied to analyze the effect of different electrolysis conditions on the composition of recycled products. The results demonstrated that the electrolysis current and the electrolysis temperature, compared to electrolysis duration, have significant effects on the selectivity of tungsten recycling. Furthermore, the analysis of cathode products demonstrated that a tungsten powder of approximately 500 nm could be selectively recovered from WC–Co hard metal scrap with the electrolysis condition of 60 mA for 4 h at 1073 K in NaF–KF molten salt.
Molten salt electrorefining offers a promising approach for green and efficient recycling of waste cemented carbides. However, the conventional halide-based electrolytes suffer from volatile tungsten halide losses and only recover metallic tungsten, necessitating energy-intensive carburization to recover tungsten carbide (WC). Herein, we propose a novel electrolytic refining and recovery method based on an oxygen-containing CaCl 2 -CaO molten salt electrolyte. The introduction of CaO suppresses the formation of volatile tungsten halides, enabling simultaneous dissolution of carbon (C) and tungsten (W) in the WC-Co anode to non-volatile CaCO 3 and CaWO 4 , respectively. Retention of Co in the anode slime is achieved through controlling anodic potential, realizing component separation. The dissolved CaCO 3 and CaWO 4 are reduced at the cathode, resulting in the generation of WC powder. This work accomplishes the direct recycling of WC from spent cemented carbides without intermediate stages. The composite products of WC and carbon are deposited on the cathodes, of which morphologies are comprised of granular aggregates and flakes. The presence of carbon suppresses the formation of W 2 C and W. However, the residual carbon does not affect hard alloy reprocessing since the W/C ratio can be adjusted via controlled W addition during subsequent alloying. This paper proposes a novel short-process green recycling technology for strategic tungsten resources.
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