China Nonferrous Metallurgy

The output of organically cobalt residue produced in the purification procedure in zinc hydrometallurgy is increasing year by year. Cobalt in the cobalt residue mainly exists in the state of organic chelate compound, which is insoluble in water and dilute acid. Therefore, the leaching rate of cobalt by conventional leaching method is very low. In line with the characteristics of such cobalt residue, this article comes up with a method of recovering cobalt from organically purified cobalt residue by employing a process comprising low-acidity leaching—calcining—reductive leaching—oxidizing cobalt precipitation. This process involves two innovation points. First, the calcination process is employed to destroy the organic components in the organic cobalt residue and convert it into easily recoverable CoO and CoSO₄; Second, in the cobalt oxide precipitation procedure, H₂O₂ is used as oxidizing agent instead of conventional Na₂S₂O₈ for oxidizing cobalt precipitation, to avoid a large consumption of oxidizing agent and cumbersome treatment of post cobalt precipitation liquor among other issues. Under the optimal process parameters of each procedure, the cobalt enrichment cobalt (Ⅲ) hydroxide (Co(OH)₃) obtained by this process contains 51.74% of cobalt, the cobalt enrichment ratio of the whole process is up to 9.5 times, and the comprehensive cobalt recovery is up to 87.42%, fulfilling the high-efficiency separation and recovery of cobalt from the organically cobalt residue in zinc hydrometallurgy.