Influence of morphology on cadmium cementation from zinc sulfate electrolyte

Impurities present in zinc sulfate electrolyte used for electrowinning can often have a major effect on the product obtained. Because of this, it is necessary to minimize the concentration of undesirable impurities such as cadmium, copper, cobalt, and nickel. Cementation processes using zinc dust as the reducing agent are most commonly used to remove the impurity ions. The present study involves an evaluation of the influence of certain electrolyte components on the morphology of the cementation residue obtained. Tests were conducted on both a batch laboratory scale as well as on a larger, industrial mini-plant, which was designed to approximate the continuous plant operations. The importance of the morphology of the cementation product on the physical condition and handling characteristics of the residue is discussed. It was also found that the physical characteristics of the solids influenced the reaction rate for impurity removal and the quantity of zinc dust required for the reaction