Deflocculation and classification of electric arc furnace dust in aqueous solution

Electric arc furnace (EAF) flue dust is generated during EAF steelmaking from iron-containing scrap such as recycled automobile bodies. The relatively high level of Zn (20-30 wt%) in EAF dusts provides a potentially valuable resource, even though the zinc is present as oxide phases such as zincite (ZnO) and zinc ferrite (ZnFe₂O₄). In this work, a method to deflocculate and disperse ZnO and ZnFe₂O₄ particles in aqueous suspension of EAF dust is developed and the efficiency of Zn recovery by the classification method was evaluated. Major findings of this study indicate that citric acid, a tetradendate chelating agent, demonstrates the best liberation and dispersion efficiency for EAF dust. Elutriating at 0.01 cm/min fluid velocity we recover 10 wt% of EAF dust (mostly ZnO particles) at a grad of 70 wt% Zn from a well-liberated and dispersed suspension of EAF dust. About 30 wt% of Zn recovery may be achieved using only simple classification.