Extractive Separation of Zinc from Oxidic Solid Bulk Feed

Dust from steel processing is a heterogeneous, multicomponent mixture of metal oxides of zinc, lead, and iron, and several trace elements such as cadmium, nickel, cobalt, and copper. The hydrometallurgical separation and downstream processing of nonferrous metals from dust of electric arc furnaces (EAF) was investigated. Solid–liquid extraction was carried out with aqueous acetic acid. In a next step, isolation of metals from the solvent phase and solvent recovery was tested. Besides isolation of intermediates, the electrochemical deposition of the metallic substances was investigated. Electrochemical deposition of zinc from aqueous feed needs high-grade purity of the feed electrolyte due to sensitivity of the hydrogen overvoltage. The effect of nickel on the break down of the hydrogen overvoltage is a major concern in electrochemical deposition of zinc from sulfate-based feed. Nickel contamination has to be kept at minimum concentration level. In contrast to sulfate-based electrolytes, the hydrogen overvoltage in acetic acid can be kept high, even when electrolyzing the extract phase without pretreatment of the extract phase