The leaching characteristics and changes in the leached layer of antimony-bearing ores from China

- Leaching results related to type of ores, species of Sb and pH value of solution
- Some alkaline ores released much more Sb, As, Pb and Cr than others.
- Total amounts and the released content of Sb, As, Pb and Cr are inconsistent.
- Sb(III) and S2 − on the surface of ore were oxidized to Sb(V) and S2O32 − and SO42 −.

China has the most abundant antimony (Sb) resources of any country in the world. Large quantities of Sb have been released from mining and smelting processes, causing serious Sb contamination in the mine or nearby areas. To understand the leaching characteristics of hazardous Sb, As, Pb and Cr from antimony minerals, 12 samples of antimony-bearing ores from eight large mines from China distributed in Hunan, Yunnan, Guizhou and Guangxi provinces were studied. The main compositions of these minerals are Sb2S3, SiO2 or CaCO3. The pH changes during the leaching indicated that some minerals themselves are alkaline, providing sufficient acid neutralizing capacity during leaching. However, some alkaline minerals release much more Sb, As, Pb and Cr than others. Inconsistencies between totals amounts and the released content of Sb, As, Pb and Cr were also found. The surface topography of an antimony sulfide mineral and the species changes of Sb and sulfur (S) on its leached surface were also characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. It is the oxidation dissolution of Sb2S3 that releases Sb. Sb(III) and S2 − on the surface of the fresh mineral were oxidized to Sb(V) and S2O32 − and SO42 −, respectively, and finally, an equilibrium of dissolution was reached over time. The release of Sb, As, Pb and Cr from typical antimony ores is a source of Sb, As, Pb and Cr in the weathering zone; with this in mind, it is easier to understand the geochemical processes and the pollution accidents involving Sb and As within the mining areas and their surroundings.