Recovery of enriched lead–silver residue from silver-rich concentrate of hydrometallurgical zinc smelter

Abstract

During the conventional zinc hydrometallurgical process operated in olden days prior to jarosite process, lead and silver reported in the neutral leach residue along with zinc ferrite. Lead and silver values from the zinc plant leach residue were recovered by a froth flotation process to obtain a silver-rich concentrate. This work deals with an alternative and innovative process to treat this silver-rich concentrate to produce an enriched lead–silver residue which can be consumed in lead smelter. The process involves the treatment of silver concentrate generated in the flotation circuit by acid-roasting followed by moderate temperature-water leach to solubilize zinc and iron completely thereby enriching lead and silver values in the leach residue. This residue contained high levels of silica which was removed by alkali roasting with caustic followed by water wash. Silica content dissolves into solution phase thereby generating a residue rich in lead and silver values. This residue was suitable for treatment in lead smelter to produce lead and silver metal. Based on the experimental results, a conceptual flowsheet was developed.