Staged separation and recovery of As, Pb, Bi, and Zn from lead smelting dusts

Abstract

The lead smelting dust is extensively produced in the lead smelting process. It poses a huge threat to environmental safety if not properly disposed, because of its high contents of heavy metals. Wherever, from another point of view, it is a high-valued resource for heavy metals. This study proposed an efficient approach to gradually separate and recycle As, Pb, Bi, and Zn from it. FeS2 was firstly used as a reductant for the As separation and recovery, via which As2O5, BiAsO4, and Pb3(AsO4)2 from the dust were reduced to volatile As2O3&As2S3 and then separated. Moreover, Pb3(AsO4)2 and PbSO4 could be sulfurized to PbS, decreasing the formation of PbO·PbSO4 and then the sintering of the residue. The As volatilization was accelerated and achieved 95.4 %. Pb, Zn, and Bi retained in the residue in the sulfur compounds of PbS, PbSO4, ZnS, and Bi2S3. In the followed smelting reduction, Na2CO3 was used as an additive to promote these sulfur compounds conversion, reduction and recycle. The recovery rates of Pb, Bi, and Zn achieved up to 96.5 %, 95.9 %, and 94.3 % respectively. While, with an excess Na2CO3 in the presence of 7.50 % coke, a sodium matte named Na-Pb-Bi-S was formed, decreasing the metals reduction and recycling. This study provided an efficient method to separate and recover As, Pb, Zn, and Bi gradually from solid wastes.