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. Duringcooling of the off-gas in the off-gas system the volatile metals are deposited on the dust particles. In electric arc furnace dust the zinccan be present in different compounds, for example as zinc oxide and zinc ferrite. Although recycling of EAF dust and utilization forzinc recovery are practiced in several countries approximately 50% of the EAF dust produced worldwide is still goes to landfill. In thisstudy the EAF dust from a mini mill was investigated by chemical fractionation. The experiment was carried out in a sequence of fiveleaching 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 containedapproximately 25% of the zinc. The reduced fraction contained approximately 8% of the zinc and the majority of the zinc was in theresidual fraction.