Patent ID: 8821613
Filing Date: 2014-09-02
Classification: C22B,Y02P

Abstract:
1. A method, comprising: (a) contacting, in the presence of an oxidant, a precious metal-containing material with a thiosulfate lixiviant to dissolve the precious metal and form a pregnant thiosulfate leach solution containing the dissolved precious metal and a polythionate derived from oxidation of thiosulfate; (b) contacting, at a pH ranging from about pH 5.5 to about pH 12, at least one of the pregnant leach solution and a barren leach solution derived therefrom with a polythionate reductant selected from the group consisting essentially of hydrogen gas, hydrogen sulfide gas, elemental sulfur, carbon monoxide, sulfide, bisulfide, polysulfide other than bisulfide, and mixtures thereof to form a regenerated solution, whereby at least most of the polythionate is reduced to thiosulfate; (c) conditioning the regenerated solution to oxidize any remaining polythionate reductant and form a conditioned solution; (d) recovering the dissolved precious metal, wherein the recovering comprises separating the regenerated solution from precious metal precipitates; and (e) recycling at least a portion of the conditioned solution to step (a), wherein the at least one of the pregnant leach solution and a barren leach solution is the pregnant leach solution, wherein the dissolved precious metal is gold, wherein, in step (b), the dissolved precious metal is precipitated as one of metallic gold and gold sulfide, wherein step (b) is performed under oxygen-depleted conditions, and whereby the pregnant leach solution has no more than about 1 ppm dissolved molecular oxygen.