Selective separation of lead from alkaline zinc solution by sulfide precipitation

Zinc and lead are usually concomitantly present in Zn-Pb ores and solid wastes, such as electric arc furnace (EAF) dusts. One of the treatment methods is to extract zinc and lead from the ores and wastes by an alkaline leaching process if applicable. The selective and quantitative separation of lead from zinc is an important step in these processes. In this work, the separation of lead from zinc in alkaline zinc solution, in leaching solutions of EAF dusts, and in oxidized zinc ores by sodium sulfide precipitation was studied. When the weight ratio of sodium sulfide (average molecular weight 222) added to the lead present in alkaline solution was over 1.8-2.0 (molar ratio approximately 1.5-1.7), lead could be, separated selectively and quantitatively, while the zinc remained in the solution without concomitant loss. The residues from the precipitation step were identified as mixtures of PbS and Na2Pb(OH)(2)S, with PbS being the predominant compound.