Hydrometallurgical Process For Recovery Of Cobalt From Zinc Plant Residue

With the development of economy, the requirement of cobalt increases sharply. Because of the lack of cobalt resources and the unreasonable exploitation, the use of cobalt secondary resources is very important.The raw material is zinc plant residue. The residue contains a great quantity of Zn, Cd, Cu, Pb and Co. In addition, it contains a little Ni, Fe and Mn. Based on the complex components of the residue, the processes consist of the following four major steps:(1)leaching the residue in sulfuric acid;(2)precipitating Cu of leach liquor by sulfide precipitation using9H2O·Na2S;(3)precipitating Mn and Fe by oxidizing precipitation and hydrolytic precipitation using Na2S2O8, NaC103and Na2CO3;(4)recycling Co of purified solution by oxidizing precipitation using Na2S2O8.The experiment conditions and the optimum results were obtained with single factor experiment.The sulfuric acid leaching was conducted at70℃for20min with the H2SO4amount of theoretical amount and the liquid to solid ratio of4:1. The leaching rates of Co, Zn, Cd, Ni, Cu, Mn, Fe and Pb are97.87%,92.03%,95.68%,87.33%,88.80%,89.60%,71.58%and0.1131%, respectively. The Pb content of leaching residue is46.9%, and the main phase of leaching residue is PbSO4.The sulfide precipitation was conducted with the9H2ONa2S amount of1.1times theoretical amount. The Cu precipitation rate is99.98%, and the Cu residual amount of solution is less than0.002g/L. The Cu content of copper residue is39.1%, and the main phase of copper residue is CuS.The oxidizing precipitation was conducted at90℃for0.5h with the Na2S2O8amount of6times theoretical amount and the initial pH value(pH=1.1). The hydrolytic precipitation was conducted at90℃for0.5h with the NaC103amount of theoretical amount and the pH value of4.0. The precipitation rates of Mn and Fe are99.97%and99.78%, respectively, and the Mn and Fe residual amount of solution are less than0.0001g/L and0.002g/L, respectively. The Mn and Fe contents of residue are2.6%and12.4%, respectively.The oxidizing precipitation of purified solution was conducted at80℃for2h with the Na2S2O8amount of4times theoretical amount and the pH value of4.0. The Co recovery reaches up to99.81%, and the Co residual amount of solution is less than0.01g/L. The Co content of cobalt product achieves45.2%, and the main phase of cobalt product is CoO(OH). The particle size of cobalt product is uniform.After the whole processes, the total recoveries of Co, Zn, Cd, Ni, Cu, Mn, Fe and Pb are89.69%,77.75%,82.67%,75.49%,88.14%,89.40%,70.00%and99.04%, respectively.