Efficient separation and recovery of cobalt from grinding waste of cemented carbide using a sulfuric acid-sodium persulfate mixed solution

Abstract

The mechanical processing of cemented carbide often generates a considerable amount of grinding waste from cemented carbide (GWCC), which serves as an important secondary resource for recovering Co and W. However, efficient separation of tungsten carbide (WC) and Co from GWCC remains challenging. This study tested an efficient process for separating Co from GWCC using a mixed solution of H₂SO₄-Na₂S₂O₈. Under optimum conditions of 20 g/L H₂SO₄, 30 g/L Na₂S₂O₈, 60 °C, and 1 h, the leaching efficiency of Co reached 97.0 %, compared to only 58.6 % when using H₂SO₄ alone. The kinetics of Co leaching in H₂SO₄ and H₂SO₄-Na₂S₂O₈ solutions were determined to be a combination of chemical reaction control and diffusion control, suggesting that Co leaching rate in H₂SO₄ solution is significantly enhanced by introducing Na₂S₂O₈. Finally, complete recovery of Co was achieved, and pure Co powder with a flower-cluster morphology was prepared from the leaching solution through oxalic acid precipitation followed by vacuum pyrolysis. The regenerative WC and Co powder can be recycled for cemented carbide production.