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

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 (Sb 2 S 3 ) can quickly transform to senarmontite (Sb 2 O 3 ) in the presence of Fe 2 O 3 and Na 2 CO 3 , and then Sb 2 O 3 will be continuously reduced into metallic Sb. Sulfur in Sb 2 S 3 was conserved as FeS and Na 2 S x O y (Na 2 S, Na 2 SO 4 and/or Na 2 S 2 O 3 ). As a result, sulfur was immobilized and recycled in the solid state resource, instead of emitting SO 2 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 °C) by this new technique. 97.3% of sulfur was fixed and converted to sulfide as matte and sulfate. In other words, SO 2 emissions were reduced by 97.3%. By-product elemental sulfur was produced after the water-leaching step, and finally producing industrial H 2 SO 4 . 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 .