A novel hydrothermal method for zinc extraction and separation from zinc ferrite and electric arc furnace dust

A novel hydrothermal process was developed to extract zinc from pure zinc ferrite (ZnFe₂O₄) nanopowder and zinc-containing electric arc furnace (EAF) dust using hexahydrated ferric chloride (FeCl₃·6H₂O) as a decomposing agent. The effects of solid FeCl₃·6H₂O to ZnFe₂O₄ ratio by mass (R_F/Z), hydrothermal reaction temperature, and time on zinc extraction were systematically investigated. In the results, when the hydrothermal reaction is conducted at 150℃ for 2 h with R_F/Z of 15:20, the efficiency of zinc extraction from ZnFe₂O₄ reaches 97.2%, and the concentration of ferric ions (Fe³⁺) in the leaching solution is nearly zero, indicating a high selectivity for zinc. In addition, the zinc extraction efficiency from the EAF dust reaches 94.5% in the case of the hydrothermal reaction performed at 200℃ for 10 h with the solid FeCl₃·6H₂O to EAF dust ratio by mass (R_{F/EAF dust}) of 15:10. Zinc and iron separation is achieved by adjusting the pH value of the leaching solution according to the different precipitation pH values of metal hydroxides.