Abstract:The selective recovery of lead from the zinc oxide dust using an alkaline Na₂EDTA solution was investigated. The effects of temperature, leaching time, Na₂EDTA concentration and initial NaOH concentration on the leaching rates of lead and zinc were studied. The following optimized leaching conditions were obtained: liquid-to-solid ratio 5:1 mL/g, stirring speed 650 r/min, Na₂EDTA concentration 0.12 mol/L, initial NaOH concentration 0.5 mol/L, leaching temperature 70 °C, leaching time 120 min. Under the optimized conditions, the average leaching rates of lead, zinc, fluoride and chloride are 89.92%, 0.94%, 62.84% and 90.02%, respectively. The filtrate was used to electrowin lead powders. The average current efficiency of electrowinning is about 93% and lead content is higher than 98% under the conditions of temperature of 60 °C, current density of 200 A/m², H₃PO₄ concentration of 1.5 g/L, and lead ion concentration of above 5 g/L. The consumption of Na₂EDTA and the direct current are about respectively 0.218 kg and 0.958 kW·h for per kilogram of lead powder.

Key words: lead; zinc oxide dust; alkaline Na₂EDTA solution; electrowinning; leaching