Research On A New Method For Removing Cobalt From High Cobalt Zinc Sulfate Solution

In this paper,cobalt removal,which is the key problem of zinc hydrometallurgy,is studied.The applicability of removing cobalt with zinc powder in the presence of new activator is emphasized for zinc sulfate solution containing high cobalt concentration.Various technological conditions and influencing factors of cobalt removal with the activator and zinc powder were determined.The conclusions are drawn as follows:(1)For zinc sulfate solution with initial cobalt concentration of 150 mg/L,cadmium concentration of 30 mg/L and zinc concentration of 126 g/L,the technological conditions of cobalt removal by zinc powder-activator cementation were systematically studied.The optimum technological parameters were as follows: reaction temperature 80~85 C,cobalt removal time 45~60 min,activator dosage 0.27 g/L,pre-adjusted acid dosage 0.96 g/L,zinc powder dosage 4.80 g/L,under the above experimental conditions.The residual cobalt concentration in the solution was reached 0.64 mg/L after cobalt removal.(2)The effects of the concentration of impurity elements Cd and Fe on the removal of cobalt by zinc powder-activator were systematically investigated: when the concentration of Cd was in the range of 0~50 mg/L,it was beneficial to remove cobalt,and when the concentration of cadmium was greater than 50 mg/L,The depth of cobalt removal is significantly worse.When the concentration of Fe is in the range of 0~20 mg/L,it is beneficial to carry out the cobalt removal reaction.When the concentration of Fe is more than 20 mg/L,the cobalt removal depth is significantly deteriorated,and the cobalt slag remelting phenomenon is obvious with the extension of the reaction time.(3)The effect of secondary acid addition on the cobalt removal by zinc powderactivator and the grade of cobalt slag was investigated: when the secondary acid addition amount was 1.88 g/L,the residual cobalt concentration of the precipitated cobalt solution was 3.5 mg/L,the cobalt content of cobalt slag was 26.11%.(4)Using the synergistic effect of the new activator and zinc powder,the conditions of zinc powder addition were tested for different initial cobalt concentrations of the working solution.When the cobalt concentration of working solution varies from 25 mg/L to 150 mg/L,the zinc powder is preferably added in an amount of 2.88~5.35 g/L.Under the process conditions,the cobalt concentration of the liquid can be generally reduced to less than 0.3 mg/L,and the lowest can be less than 0.1 mg/L.(5)When the initial cobalt concentration of the working solution is less than 75 mg/L,the activator is added at first,and then zinc powder is added after 1 minute.This sequence is beneficial to the cobalt removal.When the initial cobalt concentration of the working solution is greater than 75 mg/L,the addition of zinc powder first is beneficial to the cobalt removal process.(6)Under the condition of initial cobalt concentration of 25mg/L and reaction temperature of 75?~90?,it was verified that the cobalt removal reaction accorded with the first-order reaction kinetics,and the activation energy Ea=106.86 k J/mol.The new activator in combination with zinc powder is used to cement cobalt.The process is simple and easy.With the corresponding experimental conditions obtained in this study,the high concentration of cobalt can be removed to a lower level at one time.The higher the cobalt concentration in the solution,the less zinc powder dosage is required for per cobalt,which is different from previous research findings and industrail practice,which shows the unique properties of this activator.