Method for treating zinc-containing sulfate solution

Abstract

There is provided a method for treating zinc-containing sulfate solutions which comprises an acid removal for the recovery of a substantially pure sulfuric acid solution and a solution low in acid and containing the zinc and metal impurities from the sulfate solution. The acid removal is carried out by a membrane process that consists of dialysis, electrodialysis or dialysis integrated with electrodialysis. The dialyzate or diluate is subjected to a dual-circuit, side-by-side, simultaneous solvent extraction of zinc and sulfuric acid. In one circuit sulfuric acid is extracted from the dialyzate or diluate and the raffinate from the zinc extraction with an amine-containing extractant. Acid is stripped from the loaded organic with water or an alkaline substance, and is recovered as sulfuric acid or as a sulfate, preferably as ammonium sulfate. In the other circuit, zinc is extracted from the raffinate from the acid extraction with an organic phosphoric-, phosphinic-, phosphonic- or thiophosphinic acid-containing extractant. The zinc is stripped from the loaded organic with acid, and is recovered as a concentrated zinc sulfate solution. A residual solution substantially containing the impurities is removed from the process. The extraction and stripping may be carried out in one or more stages.

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