Hydrometallurgical process for zinc recovery from electric arc furnace dust (EAFD). Part II: Downstream processing and zinc recovery by electrowinning

The characterization and the agitation leaching of electric arc furnace dust (EAFD) by diluted sulphuric acid have been studied in Part I, as a separate article. The aim of the present research work (Part II) is the development of a purification process of the leach liquor for the recovery of high-purity zinc by electrowinning. The proposed hydrometallurgical process consists of the following four (4) unit operations: (1) Removal of iron as easily filterable crystalline basic sulphate salt of the jarosite type, at atmospheric pressure, by chemical precipitation at pH: 3.5 and 95 °C. (2) Zinc solvent extraction by Cyanex 272 at pH: 3.5, T: 40 °C, with 25% extractant concentration. (3) Stripping of the loaded organic phase by zinc spent electrolyte (62.5 g/L Zn2+) at T: 40 °C with diluted H2SO4 (3 mol/L). (4) Zinc electrowinning from sulphate solutions (at 38 °C) using Al as cathode and Pb as anode. The acidity of the electrolyte was fixed at 180 g/L H2SO4, while the current density was kept constant at 500 A/m2.