Recovery of tungsten and cobalt from tungsten carbide tool waste by hydrometallurgical method

Abstract

In a present process to treat the tungsten carbide (WC) tool waste, the wastes are roasted in air and then an alkali leaching is carried out in an autoclave. An environmentally friendly process is required to recover rare metals (Co and W) from the wastes. The effect of mechano-chemical (MC) treatment on leaching of rare metals was investigated in this study. The solvent extraction and crystallization-stripping methods were applied to separate and recover tungsten and cobalt in the leached solutions. The MC treatment for the rare metal leaching is effective to dissolve rare metals from the wastes due to the change in crystalline structure of WC and oxidation of WC with KMnO4. Cobalt ions are extracted with di-2-ethylhexyl phosphoric acid by a cation-exchange reaction. Tungsten in the leachate can be extracted by tri-octyl amine as an extractant, because tungsten species exist as anionic species in acidic solution. The rare metals in organic phase are recovered as insoluble salts such as oxalates and ammonium salts in the crystallization-stripping process.