Selective Extraction of Sn from Zinc Leaching Residue by Two-Stage Leaching and Hydrolytic Precipitation

Abstract

Zinc leaching residue (ZLR), a representative multi-metallic hazardous waste, contains not only substantial amounts of toxic elements such as Pb and As but also valuable metals including Sn and Sb. There is a pressing demand to develop environmentally sustainable processing technologies for both the treatment of ZLR and the recovery of these valuable metallic components. However, the recovery of these metals from ZLR presents a significant challenge, particularly in the case of residue with high Sn and As content. For the environmentally friendly treatment of ZLR and recovery of Sn, “H2SO4+H2C2O4” was chosen as the leaching system, and a efficiently and greenly process of “two stage leaching - alkali hydrolysis precipitation” was developed. Under optimized leaching conditions revealed significant elemental selectivity, with Sn demonstrating 90.46 % leaching efficiency while Zn showed only 9.57% leaching. Notably, Pb is hardly leached. Subsequent hydrolysis yielded 96.82% Sn precipitation, producing tin rich products (32.3% Sn) with 15-fold enrichment. The novel method achieves high selectivity for Sn leaching with excellent recovery rates. Using a sulfuric-oxalic acid leaching agent, it remains compatible with existing Zn metallurgy. Closed-loop recycling of oxalic acid enhances its green efficiency, demonstrating strong industrial application potential.

Keywords: Selective extraction, Zinc leaching residue, Acid leaching, Recovery Sn