Recovery of noble metals from refractory sulfide black-shale ores

•Roasting of flotation-gravitational concentrate•Leaching of noble metals from burnt pyrites•Recovery of noble metals on anion exchangers•Selective elution of Au, Ag, Pt and Pd by Na2SO3/NaNO2•Obtaining of Au, Ag, Pt and Pd in metal form

The processing of refractory sulfide black-shale ores and concentrates from the Sukhoy Log deposit containing gold, silver and platinum group metals (palladium and platinum) was investigated. The noble metals were leached both under atmospheric pressure and at 700 kPa at 200 °C in an autoclave. It was found that the preferred leaching method is the chlorination of the ore in HCl/NaCL solutions in the presence of MnO2. The sorption recovery of noble metals on Purolite anion exchangers and carbon adsorbent Calgon GRC-22 was carried out from solution with the following initial concentrations of noble metals (in mg/L): Au — 25; Pt — 5; Pd — 5; and Ag — 10 in the presence of 1 M FeCl3, 0.1 М CuCl2, 1 M NaCl and 1 М HCl. It was shown that the chloride complexes of noble metals can be effectively adsorbed from this solution. Then, the selective elution of noble metals from anion exchangers Purolite A170 and Purolite S992 by means of different complex-forming reagents was studied. The best elution results were obtained with Na2SO3 + NaNO2 and thiourea solutions.

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