Recovery and Recycling of Tungsten by Alkaline Leaching of Scrap and Charged Amino Group Assisted Precipitation

Abstract

Herein, we present a charged amino group assisted precipitation (CAAP) method for recovery and recycling of high-purity tungsten from a solution obtained by alkaline leaching of cemented carbide (WC–Co alloy) scrap. When lysine hydrochloride, which contains a charged amino group (NH3+), was added to an alkaline leaching solution containing tungsten (307 mmol L–1), sodium (1236 mmol L–1), and vanadium (1.7 mmol L–1), over 90% of the tungsten was rapidly recovered as a lysine–tungsten precipitate. The sodium in the precipitate was successfully removed by a simple washing process. Calcination was then performed to obtain 99.6% high-purity tungsten oxide, and reduction and carburization of the obtained tungsten oxide resulted in tungsten carbide. A pilot study using the CAAP method demonstrated a considerable decrease (60%) in the displacement (i.e., volume of chemicals used/waste created) compared with that required for the conventional ion-exchange method for tungsten recycling.