The Effect Of TiO₂ Nanoparticles On The Methane Production Of Short Chain Fatty Acids And Terephthalic Acid

Anaerobic methanogenesis process is an effective way for organic wastes harmless treatment and green energy production,which is of great influence for the serious energy crisis and environmental problems in nowadays.During methanogenesis,the interspeciese electron transfer manner between syntrophs and methanogens is an important factor,thus the regulation of methanogenic process can be achieved by adding exogenous materials to mediate the interspecies electron transfer process.In present study,the influence of TiO2 nanoparticles on methane production process with three kinds of short chain fatty acids of sodium acetate,sodium propionate and sodium butyrate and complicated carbon source of terephthalic acid as carbon source were investigated.The variation of property index,interaction of material with microbial and structure of microbial community were determined during the methanogenesis process,which explores the mechanism of nano-materials on methane production process.The main results are obtained as following:(1)The methane production process with three kinds of short fatty acids of sodium acetate,sodium propionate and sodium butyrate as carbon source were significantly promoted with the addition of TiO2 nanoparticles.The maximum methane formation rate was increased by 43.3%,27.3%and 47.4%respectively in sodium acetate,sodium propionate and sodium butyrate systems.In addition,maximum cumulative methane production was increased by 25.2%,7.7%and 6.3%respectively.Although there is no significant change of the stagnation periods of methane production in sodium propionate system,the time were shortened by 22.2%and 20.0%in sodium acetate and sodium butyrate system respectively.The degradation of carbon sources were also accelerated with the addition of TiOO2 nanoparticles in sodium acetate and sodium propionate system.Although there is no significant impact on degradation of initial carbon source in sodium butyrate,the degradation of acetic acid as intermediate was also accelerated.(2)The microbial community structure was significantly changed with the addition of TiO2 nanoparticles in sodium acetate,sodium propionate and sodium butyrate system,and may promote the process of direct interspeciese electron transfer(DIET)between syntrophys and methanogens.Microbial community analysis was shown that the relative abundance of bacteria Proteiniclasticum and archea Methanosarcina in sodium acetate system were raised with addition of TiO2 nanoparticles,the relative abundance of bacteria Coriobacteriaceae,Anaerolineaceae and archea Methanosarcina,Methanobacterium in sodium propionate system and bacteria Pseudomonas,Syntrophomonas and archea Methanosarcina,Methanobacterium in sodium butyrate system were also enriched.Furthermore,the relative abundance of total methanogens in the three systems were all increased significantly.More important,the enriched methanogens of Methanobacterium,Methanosarcina might participated in DIET,this conclusion was further supported with the results of conductivity analysis,SEM and XRD characteration of sediment,that the electrical conductivity of system was improved after TiO2 addition and the distribution of materials and micribal was not conducive to the interspeciese H2/methanol transfer.(3)For substrate of terephthalic acid,TiO2 nanoparticles also significantly promoted the methane production and degradation of substrate.Addition of TiO2 nanoparticles increased maximum methane formation rate by 40.0%,increased maximum methane production by 27.7%.The methane production period and the time of completely degradation of substrate terephthalic acid were shortened by 8.0%and 19.2%respectively.(4)The microbial community structure was altered with the addition of TiO2 nanoparticles after terephthalic acid degradation,may promote DIET between syntrophs and methanogens.The relative abundance of terephthalic acid decomposition bacteria Syntrophorhabdus and methanogens Methanolinea?Methanosaeta were enriched with the addition of TiO2.Moreover the relative abundance of total methanogens were increased significantly.In addition,the methanogens Methanolinea and Methanosaeta might have the ability of DIET,this possibility was further supported with the results of conductivity analysis,SEM and XRD characteration of sediment.