Electrolyte purification in energy-saving monovalent copper electrowinning processes

A suitable method has been proposed to purify a copper electrolyte within the framework of an energy-saving cuprous electrowinning process. In this method, the impurities are selectively removed from the electrolyte that contains a large amount of cuprous ion in an ammoniacal alkaline solution at pH 9-11. Among these impurities, precious metals such as silver are removed by cementation with copper powder. Other metals such as cobalt, nickel, zinc, aluminum, manganese, lead etc. are removed selectively by solvent extraction using an oxine-type chelating extractant (LIX 26). Equilibrium and kinetic studies for the extraction of cobalt, nickel, and zinc were performed under different experimental conditions with or without synergistic agents. Loading tests of LIX 26 were carried out, and McCabe-Thiele diagrams were constructed for stage calculations for these metals. The metals are extracted with LIX 26 via a cation exchange mechanism, and slope analysis suggested that the nickel and zinc chelates, extracted by LIX 26, were 1:2 metal:reagent species. The loaded organic is regenerated by stripping the metals completely using dilute sulfuric acid. Copper loss in the purification stages is about 10% because monovalent copper is not extracted with LIX 26 from the ammoniacal alkaline solution. (C) 2007 Elsevier B.V. All rights reserved.