Sustainable phase-conversion method for antimony extraction and sulfur conservation and waste treatment at low temperature

摘要

This work proposes a novel environmentally-friendly, low temperature phase-conversion method for antimony extraction and studies its experimental application and feasibility in pyrite cinder waste co-treatment. The detailed phase transformations and microstructural evolution mechanisms during antimony extraction and sulfur fixation process were investigated. The results show that stibnite (Sb2S3) can quickly transform to senarmontite (Sb2O3) in the presence of Fe2O3 and Na2CO3, and then Sb2O3 will be continuously reduced into metallic Sb. Sulfur in Sb2S3 was conserved as FeS and Na2SxOy (Na2S, Na2SO4 and/or Na2S2O3). As a result, sulfur was immobilized and recycled in the solid state resource, instead of emitting SO2 gas. Laboratory-scale batch experiments employed pyrite cinder as sulfur-fixing agent indicate that more than 92.6% of antimony can be extracted and recovered by one step conversion from stibnite at 1123 K (850 degrees C) by this new technique. 97.3% of sulfur was fixed and converted to sulfide as matte and sulfate. In other words, SO2 emissions were reduced by 97.3%. By-product elemental sulfur was produced after the water-leaching step, and finally producing industrial H2SO4. Iron contained in pyrite cinder waste will also be recycled. This novel method is an energy-saving, environmentally friendly and promising alternative for antimony extraction and waste treatment. (c) 2020 Elsevier Ltd. All rights reserved.