A comprehensive review on recycling methods for cemented tungsten carbide scraps highlighting the electrochemical techniques

Abstract

The scraped and end-of-life tungsten carbide materials demand innovative recycling methods to recover valuable refractory and strategic metals like tungsten, cobalt, nickel etc. The efficient treatment of this material significantly benefits to economics as compared to its ore. Several methods based on pyrometallurgy or hydrometallurgy or their suitable combination have been explored. These methods encompass several unit operations tested at the laboratory as well as on the pilot scale. Some of the methods also matured into technology on a commercial scale. However, the demonstration at the pilot plant scale is towards the validation of the developed process. Each of the methods tested so far has its own pros and cons. For instance, the combination of pyro-hydrometallurgical process has some advantages over hydrometallurgical processes such as higher efficiency, lower costs, and a few industrial requirements, but it is energy-intensive and requires high capex. Besides, considerable attempts have been put into the development of the electrodissolution processes, recently. Several studies available through reports, research articles, and patents recommend a selective electro-dissolution process, which is flexible enough to recycle different varieties of WC scraps. Various electrolytes based on acidic (H2SO4, HCl, H3PO4, HNO3) and alkaline (NaOH and NH3) media worked well to dissolve the refractory metal. Several additives are often added as supporting agents to obviate the most common constraint in electrodissolution, i.e., passivation of the anode. This review particularly highlights the electrochemical methods for the recycling of WC materials along with other recycling methods in brief.