Patent ID: 7731777

Claim:
A hydrometallurgical method for separating valuable metals and impurities from anode sludge obtained from copper electrolysis and containing at least 30% copper, wherein the method comprises: (a) leaching the anode sludge at atmospheric pressure in a sulfuric acid solution in the presence of oxygen, at a temperature of 80-100° C. for dissolving some copper from the sludge while leaving silver, gold, platinum metals and residual copper in the sludge, (b) removing the copper solution from the sludge such that the copper content of the sludge is at least 3%, (c) calcinating the sludge in a first step for removing selenium as selenium dioxide and in a second step for sulfatizing silver and copper in the sludge, (d) leaching the sludge into a neutral aqueous solution for dissolving sulfatized silver and copper while leaving gold and platinum metals in the residue, (e) separating silver from the aqueous solution, (f) separating gold from the residue obtained from silver and copper leaching, and (g) separating platinum metals from the residue obtained from gold separation.