Steelmaking Dust: Speciation of Zinc by Sequential Leaching

In electric arc furnace (EAF) steelmaking significant amounts of dust are generated. The main component in the dust is usually iron. Additionally, increased concentrations of metals which are volatile in the steelmaking process like zinc are found in the dusts. During cooling of the off-gas in the off-gas system the volatile metals are deposited on the dust particles. In electric arc furnace dust the zinc can be present in different compounds, for example as zinc oxide and zinc ferrite. Although recycling of EAF dust and utilization for zinc recovery are practiced in several countries approximately 50% of the EAF dust produced worldwide is still goes to landfill. In this study the EAF dust from a mini mill was investigated by chemical fractionation. The experiment was carried out in a sequence of five leaching steps, where the residue from a leaching step was treated in the next step. The total zinc content of the EAF dust was approximately 6.4%. In the water-soluble fraction no zinc was found, while the carbonated fraction and the oxide fraction each contained approximately 25% of the zinc. The reduced fraction contained approximately 8% of the zinc and the majority of the zinc was in the residual fraction.