DE2602827

1481295 Recovery of precious metals NATIONAL INSTITUTE FOR METALLURGY 29 Jan 1976 [29 Jan 1975] 03495/76 Heading C1A [Also in Division C7] Precious metals (defined as Pt. group, Au and Ag) are recovered from a concentrate by alloying the concentrate with Al, and leaching the alloy to produce a solution containing the precious metals. The alloy is preferably produced by melting the concentrate and Al powder at 1000‹ C or by an aluminothermic process by igniting a mixture of concentrate, Al powder and an oxide or sulphide (e.g. Fe 2 O 3 or FeS), at 1000‹ C (the oxide or sulphide may be omitted if already present in the concentrate). If the precious metal content of the concentrate is below 30 wt.%, the alloy may be formed by mixing the concentrate with C and CaO, roasting at 800‹ C, smelting with scrap iron in an arc furnace, removing the slag and adding Al scrap to form an Al-Fe-precious metal alloy. The alloy is initially leached with HCl or H 2 SO 4 to remove the Al and base metals, the residue being further leached under oxidizing conditions in HCl, using Cl 2 as the oxidant, to effect dissolution of the precious metals. If desired, the residue from the initial leaching step may be leached to dissolve Cu prior to the precious metal leach.