Effects of microbial anaerobic metabolites on nanoporosity of anthracite

To study the effect of anaerobic metabolites on the evolution of coal nanopores,the anaerobically de grading anthracite to produce biogas was performed using the anthracite obtained from Sihe in Qinshui basin,and the in situ mixed microflora of fungi and methanogens enriched from produced water associated with Qinshui Basin.Sodium 2 bromoethanesulfonate (BES) was added to inhibit the biomethane formation and promote the accumulation of metabolites in coal biodegradation.Lowtemperature nitrogen adsorption,organic solvent extraction,and gas chromatograph/mass spectrometer (GC/MS) were used to analyze the changes of pore structure and organic matter composition of coal under microbial degradation.The results showed that the total pore volume and specific surface area of coal decreased,the pore fractal dimension D1 (<2 nm) andD2 (2-10 nm) increased,and the roughness of pore surface and the complexity of pore structure increased after anaerobic biodegradation.The addition of BES enhanced the effect of anaerobically microbial degradation on coal pore structure.Meanwhile,the soluble organic composition and content in coal changed significantly,and the content of oxygencontaining aromatic derivatives and heterocyclic organics increased after anaerobic biodegradation.The addition of BES promoted more soluble organic matter,especially the pcresol in oxygencontaining aromatic derivatives trapping in the coal.Besides,the content of oxygencontaining aromatic derivatives showed significantly negative correlations with the total pore volume and specific surface area of coal,whereas there was a positive relationship with coal pore fractal dimension D1 and D2.These results indicated that the anaerobic metabolites played an important role in the effect of microbial degradation on coal pore structure.The accumulation of soluble organic matter,especially oxygencontaining aromatic derivatives in coal,was the main way in the reduction of the pore evolution of coal by anaerobic biodegradation