FeS-assisted restructuring of zinc-bearing phases into sulfated compounds for efficient zinc extraction from hazardous electric furnace dust

Abstract

Electric arc furnace dust (EAFD) is a hazardous solid waste generated as a byproduct in the steelmaking process, containing significant amounts of zinc and iron, making it a primary secondary source of zinc. The separation of zinc and iron in an environmentally-friendly and efficient manner poses a crucial technological challenge for the safe disposal and resource utilization of EAFD, facilitating the recovery of valuable zinc and the direct reuse of iron as raw materials for ironmaking. In this study, a novel method for restructuring zinc-bearing phases into sulfated compounds through low-temperature roasting by introducing FeS in EAFD were proposed. Simultaneously, the iron-containing phases undergo a transformation into Fe2O3. Subsequently, efficient separation of zinc and iron is achieved through a leaching process using dilute sulfuric acid. The conditions for the theoretical transformation of zinc-containing phases into ZnSO4 and iron-containing phases into Fe2O3 in EAFD were determined by thermodynamic calculations incorporating FeS. The temperature range for sulfation calcination was determined to be within 550–700 °C based on TG-DSC analysis and the evaluation of SO2 release during the decomposition of FeS. The optimal conditions for the roasting process were determined as an E/F ratio of 1:3, a temperature of 650 °C, and a duration of 3 h. In addition, the optimal conditions for the leaching process were determined as the addition of 1 mL of 1 M H2SO4 and a liquid–solid ratio of 25 mL/g. Under these conditions, the extractions of Zn and Fe reached 95.33 % and 0.17 %, respectively. The mechanism of phase reconstruction from zinc-containing phases to sulfate phases in EAFD was thoroughly analyzed, revealing that the Zn species in EAFD were transformed into Zn3O(SO4)2 through solid–solid and gas–solid reactions, while the majority of Fe species in EAFD and FeS were converted into Fe2O3. Effective separation of zinc and iron was achieved by dissolving Zn3O(SO4)2 in diluted sulfuric acid while retaining Fe2O3 in the residue. This study provides a fresh perspective on the recovery of zinc from zinc-containing solid waste resources, offering significant potential for the sustainable management and utilization of EAFD.