METHOD OF ISOLATION OF SILVER FROM WASTES CONTAINING HEAVY NONFERROUS METALS Russian patent published in 1997 - IPC

FIELD: nonferrous metallurgy. SUBSTANCE: invention concerns isolation of silver from dust-like intermediate products and wastes containing heavy nonferrous and precious metals. Silver- containing waste is treated with neutral (pH 6-8) 0.1-2.5 M (advantageously 0.25-1.0 M) sodium thiosulfate solution at 40-80 C for 10-120 min, maintaining solid to liquid phase ratio 1: (1-5). After leaching is terminated, solution is filtered and sulfide concentrate is precipitated from filtrate at 20-40 C by means of entering sodium sulfide solution to redox potential value 450-550 mV and metal to sulfur ratio (1.2-1.8):1 where metal is Ag, Cu, Pb, and Au. Concentrate is separated from solution, which is further recycled - transferred to stage of leaching a new portion of waste. Method makes it possible to isolate 66-99% of silver into solution, to separate selectively silver from main part of heavy nonferrous and precious metals, and isolate silver in the form of its 5-42% concentrates having no recourse to toxic and aggressive reagents and using no special corrosion-resistant equipment. EFFECT: increased isolation degree. 4 cl, 5 tbl