Sb recovery from an As pre-removed lead anode slime using a ZnS-Na2CO3 smelting reduction

Abstract

Lead anode slime is produced in large quantities during lead electrolysis, which has a high Sb content of 10-50 wt% and can be easily recycled. However, in a general alkaline pressure leaching process for pre-removal of As, Sb was partially converted to Na3SbO4 with high stability. This limited the Sb reduction and recovery in the subsequent Na2CO3 smelting reduction. Considering this fact, ZnS was creatively used as an additive in this study to destroy the stable structure of Na3SbO4 and increase Sb reduction, and meanwhile ZnS was reduced to volatile Zn (g) and recycled. In a certain range, increasing the amount of coke and ZnS increased the Sb yield, and Pb recycling could be accelerated. However, when an excessive amount of ZnS was added, the Sb compounds could be sulfurized and then combined with the generated PbS and Na2S, forming a sodium matte of Na-Pb-Sb-S. This limited the Sb reduction and reduced the Sb yield. Under the optimum conditions of a coke content of 13%, a ZnS/Sb molar ratio of 0.32, a smelting temperature of 1200 °C and a holding time of 90 min, Sb, Pb and Zn yields of up to 94.8%, 96.1% and 98.9%, respectively, were obtained.

Keywords

• as pre-removed lead anode slime
• sb recovery
• zns
• phase transformation
• smelting reduction