Experimental Study On The Effect Of Cadmium On Long-period Zinc Electrowinning

At present, zinc are mainly produced by zinc sulfide of hydrometallurgy of roasting-leaching-decontaminating-deposition processs.For the mostly process of the hydrometallurgy, electrodeposition of zinc's development requirement is mechanization and automation,the long period zinc-elelctrowinning(the period is not less than 48h)is the premise of mechanization and automation.The existing of impurity ions is directly related to the electrowinning and process index of zinc.so the behavior and impact of the impurity to the zinc electrowinning have been studied a lot by some of metallurgist,the cadmium ions have the influence which we can't neglect.This paper analysed the present status of thermodynamics and kinetics of zinc electrowinning process and the influence of mainly impurities, also included the method of cadmium removal from zinc electrolyte on the basis of referring a large number of zinc electrowinning process and the influence of impurities materials. Base on this foundation,we studied the electrochemical behaviour of the cadmium ions in the zinc electrolyte and the influence of cadmium ions to the zinc electrowinning.Through the experiment of the routine-period (24h) zinc electrowinning and the long-period(48h) zinc electrowinning, we studied the influence of the cadmium ions to the current efficiency,the electrical power consumption, and the quality of electrolytic zinc.The study shows When the ion concentration of cadmium reduce or increase, the efficiency of its current electricity and the electrical power consumption did not change significantly. The current efficiency maintained the basic of 80% plus or minus less. The electrical power consumption maintained 3000 KWh·t-1, not change so much.Through the Electron Probe (EPMA) and scanning electron microscope(SEM),we studied the quality of electrolytic zinc.The study shows that when the concentration of cadmium from 0.5mg·L-1 to 2mg·L-1,the surface of zinc electrowinning from small particles on the surface of the large, relatively dense to relatively loose.Through the Microanalysis of zinc products, The result shows in the long-period power plot case when the ion concentration of cadmium in the electrolyte below 10 mg·L-1, the zinc electro winning to be in line with national standards for the production of zinc ingots, when the ion concentration of cadmium pass the 50 mg·L-1, from the zinc is not in line with the national power production request.In this paper,we can obtain the main effects of cadmium ions in the zinc electrowinning process though the behavior of cadmium ions and long-period zinc electrowinning experiments.Tthis research can provide some of guidance for the further study of removing cadmium deeply and the influence of other impurities in long-period zinc electrowinning.