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

Abstract

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 Zn 2+) at T: 40 °C with diluted H 2SO 4 (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 H 2SO 4, while the current density was kept constant at 500 A/m 2.