Recovery of Silver, Gold, and Lead from a Complex Sulfide Ore Using Ferric Chloride, Thiourea, and Brine Leach Solutions.
The Bureau of Mines 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 deg c in 6 h, extracted about 50 pct of the zinc and formed insoluble silver and lead chlorides. Subsequent acid thiourea leaching, for 1 to 3 h at 40 deg c, extracted about 85 pct of the gold and silver. Lead chloride was solubilized from the remaining residue with nacl brine solution at 55 deg c in 1 h. Lead metal was recovered from the brine solution in an electrolytic cell with an anion permselective membrane at a current efficiency of 95 pct 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 pct.