Zinc and cobalt recovery from Co-Ni residue of zinc hydrometallurgy by an ammonia process

A new process for treating a Co-Ni residue of zinc metallurgy to produce zinc powder and recover cobalt in ammonia and ammonium sulfate(AAS) solutions was proposed. In this process, the baked Co-Ni residue was leached in AAS solutions. The leached solution was purified to remove the impurities by adding zinc powder and to separate Zn and Co from Cu, and Zn from Co and Cd. Under the optimal technical parameters, the metal leaching rate was 91.18 Zn, 96.98 Cu, 99.38 Cd and 89.35 Co in wt% respectively. The high cobalt-residue bearing 3.79wt% cobalt that of 8.4 times the raw Co-Ni residue can be used as a raw material for extracting cobalt or cobalt-salt. An active zinc powder could be obtained by using electrolysis from zinc purification solution, and current efficiency of the electrolysis is more than 88.19%. It's a practical technology for treating waste-residue in zinc hydrometallurgy and will be a feasible process to recover valuable metals.