Zinc recovery by chlorination leach

Abstract

A pollution-free process for the recovery of high purity zinc from zinc containing material including sulfide ores which provides for maximum conservation and re-use of reagents, the process consisting of chlorinating the materials either with ferric chloride or chlorine gas followed by selective removal of metals other than zinc by standard procedures, such as, lead chloride crystallization, cementation, etc. to produce a solution containing essentially only zinc chloride and ferrous chloride. To enhance the purity of the zinc end product zinc chloride is separated from the ferrous chloride solution with a zinc selective extraction agent from which the zinc chloride is stripped with sodium chloride solution in a sodium chloride stripping circuit followed by precipitation of zinc as the carbonate. The sodium chloride formed in precipitating zinc carbonate with sodium carbonate goes to an electrolytic cell to produce chlorine and sodium hydroxide by electrolysis which latter is carbonated to sodium carbonate for circulation to the zinc carbonate precipitation. The sodium chloride stripping circuit includes the electrolytic cell where excess chlorine is removed from the stripping solution. The ferrous chloride raffinate from the zinc chloride extraction step is sent to a chlorination and hydrolysis step where ferric chloride leaching agent is regenerated and iron removed. Chloride from the electrolysis step is used for the chlorination step. The process results in very little loss of reagents from the system.