China Nonferrous Metallurgy

Cobalt removal is a key step in the purification process of zinc hydrometallurgy. With a rising content of impurities in zinc sulfate solution, issues will emerge, such as lowered qualified rate of purified solution, difficulty in pressure filtration of purified residue, high unit consumption of zinc powder and unstable electrowinning process. A smelting enterprise uses cobalt removal process by antimony salt to purify zinc sulfate solution. In order to address the above issues, a comparative test on atomized zinc powder and EF zinc powder used in the purification process is carried out. A conclusion is drawn that the atomized zincpowder of high purity can be applied to stage-1 purification process to remove copper and cadmium in the liquid and alleviate the impact of impurities in zincpowderon the grade of sponge cadmium and sponge copper; EF zincpowder with 1%-4% lead can realize in-depth cobalt removal within a short time; the concentration of Zn2+ and Ca in zinc sulfate solution is controlled to be not larger than 155g/L and 0.4g/L respectively, which can ensure smooth operation of cobalt removal. When cobalt is removed from zinc sulfate solution, EF zinc powder as the leading reagent is coupled with atomized zinc powder to maintain a high cobalt removal rate and avoid cobalt re-dissolution resulting from prolonged pressure filtration. Besides, improvement of zinc powder quality and reasonable control of process parameters for cobalt removal are significant measures to lower unit consumption of zinc powder, enhance qualified rate of purified solution and ensure steady production of zinc electrowinning.