Precipitation of Precious Metals Concentrates from Post-Elution Solutions from Ion-Exchange Processes

Abstract

Precious metals have long been considered as critical raw materials in many countries. There is a growing emphasis on recovering these metals from secondary sources such as automotive catalysts or WEEE (waste of electrical and electronic equipment). During the leaching process of these materials, solutions with low concentrations of precious metals are obtained, which necessitates the use of ion-exchange methods. Following sorption and elution, a post-elution solution called eluate is produced, containing precious metals and no impurities. This eluate must undergo further processing to obtain pure metals or its compounds. The objective of this study was to explore the feasibility of recovering precious metals from post-elution solutions through cementation, reduction, precipitation, or refining techniques. The analysis of the research results indicated that metallic zinc powder is the most effective cementing agent for platinum, palladium, rhodium, and gold. Metallic aluminum and copper powders can selectively cement gold and palladium, separating them from platinum and rhodium. Aqueous hydrazine hydrate solution is the best-reducing agent for precious metals, while an aqueous hydrogen peroxide solution can selectively reduce platinum and palladium, separating them from gold and rhodium.