Recovery of silver and gold

A process for recovering silver and gold values from a feed material selected from the group consisting of precious metal electrolytic sludges and Merrill-Crowe precipitates comprising:

• (a) sampling the feed material for percent metals;
• (b) leaching the feed material with a hot ferric chloride-acid brine solution in an amount and at a concentration, based on the percent metals in the feed materials, such that a saturated solution of silver chloride will result from leaching said feed material, without concomitant formation of a saturated solution of other metal salts;
• (c) separating said silver chloride-saturated leach solution from the solid residue containing the gold values;
• (d) cooling said silver chloride-saturated leach solution to precipitate silver as silver chloride;
• (e) treating said barren ferric chloride-acid brine leach solution of step (d) with zinc dust to precipitate impurities comprising copper;
• (f) separating the solids of step (e) from said leach solution and heating said solids to convert copper therein into copper oxide;
• (g) leaching said solids of step (f) with cold sulfuric acid to selectively dissolve oxidized base and ferrous metals;
• (h) separating said pregnant leach solution of step (g) from the residue and recovering copper therefrom;
• (i) subjecting said silver chloride of step (d) to fused salt electrolysis at a temperature at least as high as the melting point of silver to recover silver therefrom, in which electrolysis process chlorine gas is generated;
• (j) recycling said chlorine gas to the separated leach solution of step (f) to regenerate said leach solution and recycling said leach solution to step (b);
• (k) contacting said gold-containing residue of step (c) with hypochlorous acid to dissolve gold values;
• (l) separating said dissolved gold from said residue;
• and
• (m) contacting said gold-containing solution with sulfur dioxide to precipitate gold and recovering said gold precipitate.