Simultaneous Removal of Nickel and Cadmium During the Cold Purification of Zinc Sulfate Solution

One of the most important steps in the zinc processing industries is the removal of impurities. In this step, cobalt, nickel and cadmium are removed from the leach solution by hot and cold purification, respectively. In this research, the effective parameters on cold purification reactor of Dandi zinc smelting plant (Zanjan—Iran) such as temperature, consumption of zinc dust, residence time, copper sulfate additive, pH of solution, zinc dust particle size and mixing speed are studied. Results demonstrated that optimum concentration of zinc dust to remove impurities properly is 2 g/L, which is less than the factory’s consumption by up to 30%. It was also found that the copper sulfate had no effect on the removal process of nickel and cadmium, and hence exclusion of this additive can cause cost-effectiveness in the process. Optimum amounts of residence time, temperature, pH and mixing speed are 75 min, 80 °C, 4.5 and 400 rpm, respectively. It was demonstrated that the smaller particle size has more effect on the removal of nickel and cadmium. The maximum efficiency was observed at < 45 µm. More ever, the high density of zinc ions had a deterrent effect on the efficiency of nickel and cadmium removal.