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.