Study of Merrill-Crowe processing .1. Solubility of zinc in alkaline cyanide solution

A comprehensive study of zinc solubility was carried out in de-aerated alkaline cyanide solutions. Parameters investigated were: dissolved oxygen, cyanide and lead nitrate concentrations and pH. Zinc solubility increases significantly with increased dissolved oxygen and cyanide concentrations. Eh-pH diagrams have been developed and used to predict regions of stability of zinc hydroxide, which may inhibit gold precipitation. The interaction between cyanide and hydroxyl ion activities to prevent the formation of zinc hydroxide is presented. With lead nitrate additions, maximum solubility of zinc occurs in the range of 10-15 mg/l lead nitrate. SEM photomicrographs of zinc particles in the presence of lead nitrate are presented.