The Study On The Speciation And Transformation Of Elemental Sulfur Mediated By Thermophile Sulfolobus Metallicus

Microbial leaching of metals from sulfide is a consequence of the interactions between bacteria and mineral. Sulfur transformation during bioleaching is complex and may involve the minerals passivation. Investigating the sulfur speciation during sulfide dissolution is a key to understand the mechanisms of sulfide oxidation and evaluate the composition of passivation layer. In present work, we chose three typical metal sulfides including pyrite, sphalerite and chalcopyrite, of which, pyrite is acid insoluble while sphalerite and chalcopyrite are acid soluble. To verify the surface sulfur speciation transformation of metal sulfides bioleaching with the thermophile Sulfolobus metallicus at 65℃. we adopted X-ray diffraction (XRD), diffuse reflectance Fourier transform infrared spectroscopy (FT-IR) and sulfur K-edge X-ray absorption near edge structure spectroscopy (XANES). The primary subjects of which include four parts as follows:(1) Growth and surface properties of thermoacidophilic Archaea strain Sulfolobus metallicus YN-25 grown on different substratesThe growth characteristics of Sulfolobus metallicus YN-25 have been investigated. The cells were cultured with ferrous sulfate, elemental sulfur and pyrite mineral respectively, and the electrokinetic behaviour and the surface groups of cells grown under above substrate have been investigated. The results showed that the the Zeta-potential of cells grown in ferrous sulfate presented distinctly characteristics compared to the cells cultured in solid substrate. The FT-IR spectra indicated that the sulfur grown cells contained a higher amount of protein component than the ferrous ion-grown cells on the cells surface.(2) Investigation of sulfur speciation transformation during bioleaching of pyrite-containing sphalerite concentrate by thermophile Sulfolobus metallicus at 65℃Sulfur speciation transformation during bioleaching of pyrite-containing sphalerite concentrate by extremely thermophile S. metallicus was investigated by XRD, FT-IR and sulfur K-edge XANES. Bioleaching results showed the presence of S. metallicus can effectively enhance its dissolution. The pyrite in the mineral facilitated the dissolution in the early stage, but hindered the dissolution in the late stage for the accumulation of jarosite. The results of sulfur speciation analyses confirmed jarosite and elemental sulfur are the main composition of the bioleached residues, and the accumulation of jarosite is mainly responsible for the decline of the dissolution rate.(3) Investigation of sulfur speciation transformation during bioleaching of pyrite concentrate by thermophile Sulfolobus metallicus at 65℃Sulfur speciation transformation during bioleaching of pyrite concentrate by extremely thermophile S. metallicus was investigated by XRD, FT-IR and sulfur K-edge XANES. Bioleaching results showed the presence of S. metallicus can effectively enhance the extration of iron ion from pyrite. The results of sulfur speciation analyses confirmed that jarosite, elemental sulfur and small amount of sulfite are detected on the surface of minerals during bioleaching, and the accumulation of jarosite is mainly responsible for the decline of the dissolution rate.(4) Investigation of sulfur speciation transformation during bioleaching of pyrite concentrate by thermophile Sulfolobus metallicus at 65℃Sulfur speciation transformation during bioleaching of chalcopyrite concentrate by extremely thermophile S. metallicus was investigated by XRD, FT-IR and sulfur K-edge XANES. Bioleaching results showed the presence of S. metallicus can effectively enhance the dissolution of chalcopyrite. The results of sulfur speciation analysis confirmed that there are a variety of sulfur compounds detected, including covellite, chalcocite, bornite, jarosite, elemental sulfur, accompanying with the leaching behavior elucidation, we suppose that jarosite accumulated on mineral surface is the main component of the passivation layer and responsible for the chalcopyrite passivation.