, Volume 38, Issue 6, pp 18-22
Date: 26 Oct 2012

Ferric Chloride, Thiourea and Brine Leach Recovery of Ag, Au and Pb from Complex Sulfides

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The Bureau of Mines recently investigated a hydrometallurgical procedure to recover gold, silver, and byproduct lead from a complex lead-zinc sulfide ore. A ferric chloride (Fecl3) preleach, at 40°C for six hours extracted about 50 percent of the zinc and formed insoluble silver and lead chlorides. Subsequent acid thiourea leaching, for one to three hours at 40°C, extracted about 85% of the gold and silver. Lead chloride was solubilized from the remaining residue with NaCl brine solution at 55°C in one hour. Lead was recovered from the brine solution in an electrolytic cell with an anion perm selective membrane at a current efficiency of 95 percent and current density of 100 A/m2. Spent FeCl3 leach solution was reoxidized in the anode compartment at a current efficiency between 75 and 95 percent.

R.G. Sandberg and J.L. Huiatt are currently with the Department of the Interior, Bureau of Mines, at the Salt Lake Research Center in Salt Lake City, Utah.
Editor’s Note: This article has been adapted from a full length research presentation at the TMS session “Innovation in Precious Metals Processes” at the 1986 Annual Meeting in New Orleans.