Extraction of zinc from EAF dust by alkaline leach followed by fusion of the leach residue in caustic soda

Zinc was recovered from two samples of electric arc furnace (EAF) dusts containing 24.8% and 16.8% zinc using direct alkaline leach followed by fusion of the resulting leach residues with caustic soda. The extraction of zinc was dependent on the iron content of the dust, both for the alkaline leach and the alkaline fusion steps. A higher iron content resulted in a lower zinc recovery, 53% and 38% of zinc was extracted from the dust samples when they were leached with 5 M NaOH for 42 hours. The zinc remaining, in the leach residues, presumably present as zinc ferrite, was extracted by fusing the residues with caustic soda. Quantitative extraction of zinc was obtained from the leach residue from first sample, while only 85% of zinc was recovered from the second sample. A proposed flowsheet for zinc recovery from the dusts was presented.