Abstract：A clean route was developed to convert flue dusts of secondary copper smelters into value-added products. The process consists of microwave-assisted alkaline leaching, purification and electrolysis. Initially, 83% (mass percent) Zn is dissolved in 200 g/L NaOH under microwave radiation (4 cycles of 30 s), whereas most of Cu is left in the residue. The rates of zinc recovery are significantly higher under microwave conditions as compared to those observed with conventional leaching. Furthermore, a better zinc selectivity and lower NaOH consumption are obtained. Then, the purification by adding zinc powders is carried out to reduce the Pb and Cu to low levels (lower than 100 mg/L). Subsequently, ultrafine Na2S are produced by electrolysis and the best performance occurrs at reaction temperature of 35 ℃, current density of 1 000-1 500 A/m2 with a solution composition of 30-40 g/L Zn2+ and 180-220 g/L NaOH. The products were characterized by SEM, XRD and Malvern laser particle size analyzer. The clean method also promises to treat other industrial wastes containing Zn due to its low cost and simple design.
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2015, Vol. 25 
