Variation of sulfur speciation of coal gangue leaching by acidophilic ferrous / sulfur oxidizing microbes

Acidophilic iron and sulfur oxidizing microorganisms Acidithiobacillus thiooxidans SOB-1 and Acidithiobacil-lus ferrooxidans SOB-2 were used to bioleach the coal gangue,and its sulfur speciation variations after leaching were analyzed with XRD and sulfur K-edge X-ray absorption near edge spectroscopy (XANES). XRD results showed that the pyrite in coal gangue disappeared after leaching treatment,however,the other mineral components always remained unchanged. XANES showed that the sulfur speciation in original coal gangue were mainly sulfur of pyrite,oxidized glu- tathione,thiosulfate,sulfate and a small amount of thiophene ( DBT). Compared with sterile control,the SOB-1 had poor effect on gangue leaching and the sulfur content variation in which was not obvious. Nevertheless,both SOB -2 and the mixed culture of SOB-1 and SOB-2 had an excellent ability on removing total sulfur and sulfur of pyrite in coal gangue and the highest removing rate of which were up to 51. 08% and 71. 5% ,respectively. The pyrite in coal gangue could be oxidized to thiosulfate and finally to sulfate,furthermore,the SOB -2 and mixed culture clearly im- proved the transformation of sulfur speciation. On the other hand,it seems that both two strains and their mixtures had ability to remove the sulfur of DBT.