Reduction of Volatile Impurities in Zinc Chloride Melt with Metallic Iron and Its Effect on Vacuum Separation Behavior

Abstract

Metallic Zn production currently generates toxic gases and residues that cannot be recycled, and consumes a large amount of energy. To develop more efficient process using chlorination reaction of Zn resources, purification methods for crude ZnCl₂ melt have been developed with limited success. In this study, we have investigated a new type of pyrometallurgical purification that combines reduction reactions of FeCl₃ and CuCl₂ in ZnCl₂ melt using metallic Fe with vacuum distillation. Metallic Fe reduced FeCl₃ and CuCl₂ into FeCl₂ and CuCl/Cu, respectively, which show lower vapor pressures than ZnCl₂. Vacuum distillation of the crude ZnCl₂ melt after the Fe reduction successfully produced a high-purity ZnCl₂ deposit with less contamination by Fe and Cu. This study reveals that reduction treatment with metallic Fe converts FeCl₃ and CuCl₂ into less volatile substances and suppresses contamination by such substances into ZnCl₂ recovery.