Reaction behavior of coexisting cations in cadmium electrolytic deposition process

With the complexity and diversity of cadmium resources, cadmium electrowinning systems usually contain many impurity metals, such as copper, zinc, iron, and nickel. In this paper, through systematic experimental research, the reaction behavior of Cu²⁺, Ni²⁺, Fe²⁺ and Zn²⁺and their effects on the current efficiency, purity, and morphology of cathodic cadmium during the electrowinning process were investigated. Furthermore, the minimum influencing concentrations of Cu²⁺, Ni²⁺, Fe²⁺ and Zn²⁺ were determined. The results show that Cu²⁺ has almost no effect on cadmium electrodeposition when its concentration is below 1 mg/L, while even at a concentration of 2.5 g/L, Ni²⁺ has a negligible effect. The efficiency decreases when the concentration of Fe²⁺ is above 20 mg/L, and the impact on the electrowinning is relatively small when the concentration of Zn²⁺ is below 1.5 g/L. According to the electrochemical analysis and micro-morphology characterization, Cu²⁺ preferentially deposits and forms a compound with cadmium, and the redox reaction of Fe²⁺ leads to a decrease in current efficiency and increase in power consumption. Besides Ni²⁺, other ions including Cu²⁺, Fe²⁺ and Zn²⁺ all can affect the morphology of cathodic cadmium. The results further improve the basis for the cadmium electrolytic deposition in complex solutions.