Preparation of high-purity cobalt

A process consisting of anion exchange in a hydrochloric acid solution, electrowinning, plasma arc melting and electron beam melting of electrolytic cobalt has been developed for preparing high-purity cobalt. Glow discharge mass spectrometry (GDMS) and residual resistivity ratio (RRR) were applied for analysis and purity evaluation of the produced cobalt. Almost all the metallic impurities except for copper were removed efficiently and reduced to lower than 1 mass ppm by the anion exchange step. Electron beam melting at a final step was very useful for removal of copper by vaporization from the molten cobalt and the copper concentration could be lowered to below 1 mass ppm. As a result, high-purity cobalt with above 99.9995% in purity (RRR=210) was produced by this practical purification process.