Patent ID: 7862786

Claim:
A method for recovering copper ions and zinc ions from an aqueous solution comprising iron ions, copper ions, and zinc ions by selective precipitation, the method comprising: (a) adjusting the pH of the aqueous solution to a pH sufficient to precipitate the iron ions as an iron oxy-hydroxide compound while avoiding the precipitation of compounds of copper and zinc thereby yielding an iron oxy-hydroxide precipitate and an iron-depleted aqueous solution comprising copper ions and zinc ions; (b) contacting the iron-depleted aqueous solution with a source of sulfide ion comprising hydrogen sulfide to precipitate the copper ions as a copper sulfide while avoiding the precipitation of the sulfide of zinc thereby yielding copper sulfide precipitate and a copper-depleted aqueous solution comprising zinc ions; and (c) contacting the copper-depleted aqueous solution with a source of sulfide ion comprising hydrogen sulfide in a concentration sufficient to precipitate the zinc ions as a zinc sulfide wherein co-precipitation of aluminum hydroxide and gypsum therewith is avoided; wherein the pH of the copper-depleted solution produced in (b) is lower than the pH of the iron-depleted solution produced in (a); and wherein the steps (a), (b), and (c) are carried out in that order .