Efficient extraction and separation of zinc and iron from electric arc furnace dust by roasting with FeSO4·7H2O followed by water leaching

Electric arc furnace dust (EAFD) formed during steelmaking in electric arc furnace is rich in iron and zinc. Due to the negative effects of zinc, directly recycling as raw materials for ironmaking does not work so that it is still mostly accumulated. In this study, a novel process was proposed, wherein EAFD was roasted with FeSO4·7H2O followed by water leaching for the effective and selective extraction and separation of zinc and iron from EAFD. The optimal roasting conditions were determined as mass ratio of FeSO4·7H2O/EAFD of 1.5, roasting temperature of 675 °C, holding time of 3 h. The transfer mechanism of elements in EAFD was analyzed. 98.79% of zinc and only 0.11% of iron were dissolved in the leaching solution, respectively, avoiding the iron-removing step before the subsequent zinc electrodeposition. Meanwhile, most of Ca, Mg and Mn ions transformed into corresponding sulfates during roasting experiments and then entered leaching solution after water leaching. Thus, the leaching residue with 91.36% mass ratio of Fe2O3 could be applied as raw material for ironmaking industry. In addition, the majority of heavy metals (Pb and Cr) were remained and immobilized in the leaching residue, meeting the requirement of leaching toxicity standard. Results from this work provide a new insight into selective recovery of valuable metals from EAFD while at the same time exploiting the solid waste of Copperas.