Isolation Of Sulfate-reducing Bacteria And Its Effect On Lignite

In recent years,bio-methane production from coal has been attracted more and more reseachers'attention as it can realize efficient and clean utilization of coal.Biogenic coal-bed methane was produced by the synergistic action of various microorganisms,Sulfate-reducing bacteria(SRB)plays an important role in the anaerobic degradation of coal to produce gas,but the study of its effect on lignite has been rarely reported.In this paper,the methanogenic mixed flora preserved in the laboratory was used as the source of bacteria,and the lignite from Zhao Tong,Yun Nan province,was used as the research object.Firstly,SRB in the mixed flora was separated and purified in a directional manner,and then its adsorption effect on the surface of lignite was studied.Finally,the physical and chemical properties of lignite before and after SRB's effect were compared and analyzed.The main conclusions were as follows:(1)Analysis of the microbial community structure of methanogenic mixed flora showed that SRB accounted for nearly 17%of the mixed flora,mainly for Desulfurispora(12.38%),Desulfotomaculum(2.71%)and Desulfitobacterium(1.80%).A strictly anaerobic SRB strain ZTS1 was domesticated,isolated and purified from mixed bacteria.The strain can produce hydrogen sulfide gas in the process of culture and form a black single colony on the anaerobic test tube wall.It was identified by molecular biology as belonging to the genus Desulfotomaculum,and the homology of Desulfotomaculum reducens MI-1 up to 99.94%.So we called it Desulfotomaculum reducens ZTS1.The results of SEM and TEM confirmed that it is a rod-shaped bacterium with a size of(1-2)?m×0.5?m and has a flagellate structure,a large number of electron dense particles are distributed around the cell membrane.(2)The effects of adsorption temperature,p H value,adsorption time and cell number on SRB adsorption on lignite surface were studied.The results showed that ZTS1 could perform better adsorption on lignite surface.It showed that ZTS1 could be adsorbed well on the surface of lignite,and the adsorption equilibrium could be approached after 6 min,the maximum adsorption rate could reach 35.4%.The optimal adsorption condition is 35 ~oC and p H=7.In addition,ZTS1 could maintain a good adsorption rate in the weak acidic environment,but its adsorption capacity would suddenly weaken in an alkaline environment.SEM results showed that ZTS1 was dispersed on the surface of lignite,which is a simple single-layer adsorption,and mainly concentrated in the rough surface area.The results of contact angle measurement showed that the surface hydrophilicity of lignite adsorbed by ZYS1 was enhanced.(3)With the times going,ZTS1 would reduce the p H of the solution system and would eventually be stable at about 5.2,while the Eh would increase with time.The results of XRD,surface potential,SEM,porosity and FT-IR analysis showed that the sodium thiosulfate basically disappeared after SRB effect.The surface potential of lignite would decrease,the surface roughness would increase,the pore structure in lignite would increase,and the increased pores main were micropore.Some functional groups on the lignite surface increased significantly after the experiment,including methyl,methylene and associated hydroxyl groups,while the free hydroxyl groups decreased significantly.In addition,the total number of-C-O-bonds remained stable but the forms in which they existed,such as carboxyls,phenols,ethers,alcohols,and esters,changed.There are 35 figures,10 tables and 118 references in this paper.