Method for processing anode sludge
AssigneeOutotec Oyj
InventorsLeo Lindroos, Henri Virtanen, Olli Järvinen
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Abstract
The invention relates to a hydrometallurgical method for separating the precious metals and impurities of anode sludge obtained from copper electrolysis. According to the method, anode sludge copper is separated in atmospheric leaching; calcinated in two steps for separating selenium and for sulfatizing silver; the sulfatized silver is separated by leaching into a neutral aqueous solution, from which it can be separated by reduction or by extraction.
Claims24
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.
Dependencies are inferred from the claim text.