Tungsten carbide-cobalt alloys (WC–Cos), which are used for cutting tools, are mainly composed of tungsten carbide and cobalt with minor elements including chromium, tantalum, nickel. Recycling WC–Cos requires a large amount of energy and chemicals for leaching tungsten. We previously showed that tungsten in WC–COs can be leached by potentiostatic electrolysis at − 0.7 V in molten sodium hydroxide (NaOH) at 723 K; tungsten constituted 99.7 mass% of the leached component in the molten salt. In this study, we investigated tungsten leaching at a lower temperature by using a eutectic mixture of 51.5 mol% NaOH and 49.5 mol% potassium hydroxide (KOH) as the electrolyte. Tungsten was leached from the alloy at temperatures above 623 K, which was 100 K lower than the previous study. Cobalt dissolved in the molten salt, although it formed a passive layer. Chromium underwent oxidization and dissolved as a hexavalent ion below 623 K. Tantalum dissolved even without electrolysis. Tungsten was leached at 623 K in this system. Highly purifying tungsten could be obtained by dissolving the cooled molten salt in water and bringing it in contact with air to precipitate other metal ions. Therefore, the electrochemical process is expected to be used for separating tungsten from WC–Cos.

用于切削工具的碳化钨-钴合金（WC-Cos）主要由碳化钨和钴以及微量元素（包括铬，钽，镍）组成。回收WC-Cos需要大量能量和化学物质才能浸出钨。我们以前的研究表明，在723 K的熔融氢氧化钠（NaOH）中，恒电位电解在− 0.7 V时可以浸出WC-COs中的钨。钨占熔融盐中浸出组分的99.7质量％。在这项研究中，我们通过使用51.5 mol％NaOH和49.5 mol％氢氧化钾（KOH）的低共熔混合物作为电解质，研究了钨在较低温度下的浸出。钨在高于623 K的温度下从合金中浸出，比以前的研究低100K。钴溶解在熔融盐中，尽管它形成了钝化层。铬发生氧化，并在623 K以下以六价离子形式溶解。即使没有电解，钽也会溶解。在该系统中，钨在623 K浸出。通过将冷却的熔融盐溶解在水中并使之与空气接触以沉淀其他金属离子，可以得到高度纯化的钨。因此，电化学方法有望用于从WC-Cos中分离钨。