Study On Anaerobic System Promoted By Graphene-Based Materials

The overexploitation of fossil fuels and the acceleration of energy demand has greatly reduced the fuel storage.The burning of fossil fuels produces about 15 billion tons of carbon dioxide（CO₂）and 0.3 to 70 million tons of methane（CH₄）each year,contributing to global warming.Anaerobic fermentation is one of the ways to produce renewable energy（H₂ and CH₄）,which can achieve high organic load rate and low sludge formation.In this study,magnetite reduced graphene oxide nanocomposites（Fe₃O₄-r GO NCs）were prepared by loading magnetite nanoparticles（Fe₃O₄ NPs）onto reduced graphene oxide（r GO）sheets by solvothermal method.Fe₃O₄ NPs and Fe₃O₄-r GO NCs were added into the anaerobic fermentation capacity system as exogenous additives to improve the effect of anaerobic fermentation on hydrogen and methane production.The research contents include:（1）In order to explore the effects of Fe₃O₄ NPs and Fe₃O₄-r GO NCs on bio H₂production in dark fermentation.Fe₃O₄ NPs（10-400 mg/L）and Fe₃O₄-r GO NCs（10-400 mg/L）were added to the dark fermentation hydrogen production reactors to enhance the performance of dark fermentation hydrogen production.When the dosage was 100 mg/L,the optimal bio H₂ yield of G₂（Fe₃O₄ NPs）and G₃（Fe₃O₄-r GO NCs）reactors was 198.30 m L/g glucose and 225.60 m L/g glucose,which was 42.97%and62.65%higher than that of G₁（blank group）,respectively.Both Fe₃O₄ NPs and Fe₃O₄-r GO NCs could intensify butyrate-type fermentation and change the hydrogen-producing microorganism cells morphology,but the enhancement effect of Fe₃O₄-r GO NCs was superior.Microbial community structure analysis showed that the abundance of Clostridium-sens-stricto-1 increased from 37.77%to 40.58%in the Fe₃O₄NPs group.The abundance of Clostridium-sens-stricto-1 increased from 37.77%to44.02%in Fe₃O₄-r GO NCs group.These results indicated that Clostridium-sensu-stricto-1 became more dominant ultimately by Fe₃O₄-r GO NCs.（2）In order to explore the effect of Fe₃O₄ NPs and Fe₃O₄-r GO NCs on the degradation of butyrate to produce methane in the anaerobic fermentation.Fe₃O₄ NPs（50-400 mg/L）and Fe₃O₄-r GO NCs（50-400 mg/L）were added to the anaerobic reactors to enhance the methanogenic performance.When the dosage was 100 mg/L,the optimal bio H₂ yield of R₂（Fe₃O₄ NPs）and R₃（Fe₃O₄-r GO NCs）was 162.38 m L/g COD and 179.75 m L/g COD,which was 25.99%and 39.48%higher than that of R₁（blank group）,respectively.The results of soluble metabolite analysis showed that Fe₃O₄ NPs and Fe₃O₄-r GO NCs could promote the degradation of butyrate.Microbial community analysis results indicated that Fe₃O₄ NPs and Fe₃O₄-r GO NCs improved the microbial community structure.The abundance of Anaerolineaceae,Syntrophomonas,Proteiniphilum and Methanobacterium has increased.（3）In order to explore the effect of Fe₃O₄ NPs and Fe₃O₄-r GO NCs on the degradation of propionate to produce methane in the anaerobic fermentation process.Fe₃O₄ NPs（50-400 mg/L）and Fe₃O₄-r GO NCs（50-400 mg/L）were added to the anaerobic reactors to explore the methanogenic performance.When the dosage of was200 mg/L,the optimal bio H₂ yield of B₂（Fe₃O₄ NPs）and B₃（Fe₃O₄-r GO NCs）reactors was 137.13 m L/g COD and 150.00 m L/g COD,which was 15.84%and 26.72%higher than that of B₁（blank group）,respectively.The results of soluble metabolite analysis indicated that Fe₃O₄ NPs and Fe₃O₄-r GO NCs could promote the degradation of propionate.Microbial community analysis results showed that Fe₃O₄ NPs and Fe₃O₄-r GO NCs improved the microbial community structure.The abundance of Anaerolineaceae and Christensenellaceae＿R-7＿Group and Methanobacterium were increased.