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

• Published in: Hydrometallurgy Vol. 105; no. 1; pp. 127 - 133
• Main Authors: Aparajith, B., Mohanty, D.B., Gupta, M.L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2010; Elsevier
• Subjects: Acid roasting; Alkali roasting; Applied sciences; Enrichment; Exact sciences and technology; Ferrite; Hydrometallurgy; Iron; Lead–silver residue; Metals. Metallurgy; Production of metals; Residues; Roasting; Silicon dioxide; Silver; Smelters; Washing; Water leaching; Zinc; Water leaching; Alkali roasting; Washing; Lead–silver residue; Acid roasting; Hydrometallurgy; Silver; Lixiviation; Ore concentrate; Recovery; Lead-silver residue
• ISSN: 0304-386X; 1879-1158
• DOI: 10.1016/j.hydromet.2010.08.010

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. ►Silver concentrate produced from zinc leach residue contained high iron and silica restricting its consumption in lead smelter. ►Major portion of zinc and iron were in the form of sulphides and ferrites. Atmospheric leaching under normal acidity–temperature conditions showed poor iron removal. Tests were conducted for roasting with acid followed by water leach to dissolve the zinc and iron from concentrate. Extraction efficiency for zinc and iron were up to 96% and 96% respectively. Zinc–iron rich liquor can be used in jarosite section to precipitate iron and recover zinc by recycling back into the leaching stream. ►The acid roast-leached residue was enriched in lead, silver and silica content with typical silica assays of 15–18%. Alkali roasting is found to be effective to eliminate silicate impurities. The roasted mixture was repulped with water to free the material of alkalinity which will effectively remove the silicate in the process. The residue thus produced had low zinc, iron and silica content with lead and silver of 40% and 2.1% respectively. This enriched lead–silver residue can be consumed in lead smelter for metal recovery.