Separation of arsenic and extraction of zinc and copper from high-arsenic copper smelting dusts by alkali leaching followed by sulfuric acid leaching

Separation of arsenic and extraction of zinc and copper from high-arsenic copper smelting dust (HACSD) is one of the difficulties in the world. A two-stage countercurrent alkali leaching followed by one-stage sulfuric acid leaching for arsenic separation and zinc and copper extraction was developed in this work. The dusts properties, metals leaching behaviors and their phase transformations in the alkali leaching and sulfuric acid leaching were explored systematically. Results indicate that >95.5% of As was successfully separated from HACSD into alkali leachate. Arsenic and metals (Zn, Pb, Bi, Sn) contents were up to 61.50 g.L-1 and as low as 0.001-0.21 g.L-1 in alkali leachate, respectively. >97.2% of Zn and >96.4% of Cu were extracted from the alkali leaching residues into sulfuric acid leachate. The sulfuric acid leaching residues were enriched with 34.16% of Pb, 8.38% of Bi and 11.54% of Sn in oxides and sulfates phases. The metals leaching behaviors, phase transformations and microstructure of metal compounds during the leaching processes were confirmed by X-ray diffraction and scanning electronic microscopy/energy dispersive spectroscopy. The proposed process offered high separation efficiency of arsenic, zinc and copper, as well as low environmental pollution.

Automated summary

The study developed a two-stage countercurrent alkali leaching followed by one-stage sulfuric acid leaching process to efficiently separate arsenic and extract zinc and copper from high-arsenic copper smelting dust. The results showed high separation efficiency of arsenic in alkali leachate and high extraction rates of zinc and copper in sulfuric acid leachate. The proposed process not only achieved successful separation of the metals, but also minimized environmental pollution.