Separation of tungsten and cobalt from cemented tungsten carbide by rapid breakdown anodization

Abstract

Cemented tungsten carbide (WC-Co) has been used as an important industrial material and secondary resource of tungsten (W) and cobalt (Co). The recycling methodology of WC-Co scraps has drawn much attention because the recovery of strategic metals such as W and Co are critical. Here, rapid breakdown anodization (RBA) was applied for the first time to the conversion of WC-Co into high-purity hydrated tungsten oxide (WO3-H2O) up to 99.99 wt% and pure Co metal up to 90.43 wt% by using WC-Co as a sacrificial anode. Effective cobalt leaching was achieved in acidic aqueous solution without encountering anodic passivation issue due to the successful removal of tungsten oxidation layer during the electro-dissolution of WC-Co. Based on the particle formation mechanism of RBA, a two-stage reaction was confirmed, including electrochemical dissolution and chemical precipitation. The high purity of recovered WO3-H2O powders was realized by using high current density and high electrolyte concentration. We demonstrate that RBA is a new pathway for effective and environmentally-friendly WC-Co recycling with a significantly simplified process compared to conventional hydrometallurgical methods.