Electrochemical Leaching of Tungsten from Hard Metal Alloy Using Molten Sodium Hydroxide

抄録

Hard metal alloy, which is used as material for cutting tools, comprises tungsten carbide, cobalt, and other elements and possesses excellent hardness and heat resistance. Hard metal alloy is difficult to recycle, and its rate of recycling in Japan is low. In this study, components of hard metal alloy were leached by electrolysis in molten sodium hydroxide. The optimum experimental condition was potentiostatic electrolysis at an oxidation potential of −0.7 V. Tungsten constituted 99.7 mass% of the leached component in the molten salt, and other metals oxidized to passive materials. Tantalum was dissolved in the molten salt without electrolysis. Chromium was oxidized from its metal state to its trivalent oxide, which was converted to the hexavalent oxide by trace oxygen in the atmosphere of the reactor.