Study On Hydrogen Production By Ethanol Fermentation Based On In Situ Separation Of Bipolar Membrane Electrodialysis

At present,environmental pollution and energy shortage are the biggest problems that human beings are facing.Development and utilization of clean energy is the direction of social development and is the focus of sustainable development.Hydrogen as a renewable energy,has gradually become the focus of research because of its clean and efficient characteristics.Biological hydrogen production with low energy consumption,high yield,no pollution in the process of preparation,is a hot spot in the current study,compared with the light fermentation,dark-fermentation bio-hydrogen can achieve continuous and stable hydrogen production,which can metabolize more substrates,is the most practical hydrogen production pathway.How to remove the inhibitory factors of fermentation and improve the growth and metabolism of dark fermentative microorganisms to achieve more stable and continuous hydrogen production is a bottleneck in the research breakthrough.In this paper,anaerobic hydrogen producing bacteria E.Harbinese B49 as the research object,to investigate the effects of DC into the fermentation broth on cell proliferation,substrate utilization and product synthesis,using carbon felt,graphite plate,ruthenium-plated titanium plate and coated graphite plate as electrode materials,monitoring the reaction process in the system of glucose utilization status,evaluation and screening can be used as electrode material in situ electrodialysis fermentation.Among them,the graphite plate and graphite plate coated as electrifying electrodes have a low glucose degradation rate,after fermentation the bacteria floating in the upper fermentation broth,and eventually metabolized 2.45g/L and 2.25g/L glucose,which are 73%and 67%of the non-energized reactor.On the contrary,the carbon felt and the ruthenium-plated titanium plate had no significant inhibitory effect on the growth of E.Harbinese B49 bacteria,and the bacteria settled well.The reaction finally metabolized 3.75g/L and 3.7g/L of glucose,which was not electrified 1.12 and 1.1 times,so the choice of carbon felt as the electrode.To further explore the carbon felt as the electrode material when the initial electrification and reaction after 5h on the growth and metabolism of E.Harbinese B49,the initial pH of the reaction system and the reaction system 5h were reduced to 4.57 and 4.27,the glucose degradation rate was 38.7%and 58.27%respectively.The test data showed that E.Harbinese B49 inoculated domesticated culture for a period of time after the power system,the bacterial growth and metabolism better than the initial electrification system.In examining the effect of current density on the hydrogen production metabolism of E.Harbinese B49,comparative experiments were conducted at DC of OmA/cm2,0.3mA/cm2,0.5mA/cm2,lmA/cm2,2mA/cm2 and 5mA/cm2.The results show;The DC lower than 2mA/cm2 could promote the growth and metabolism of E.Harbinese B49 to different degrees.At the end of the reaction,the accumulated biomass were 1.53 times,1.45 times,1.29 times and 1.14 times than the non-energized system,A maximum of 13.22mmol acetic acid and 1190mL H2 were obtained,which were 1.57 times and 1.40 times more than the non-energized system,the metabolic capacity of glucose up to 31.79mmol,which was 1.32 times more than the non-energized system,on the contrary,the 5mA/cm2 DC system had only 79%of the glucose metabolism capacity of the non-energized system.Thus,the weak DC current density can promote the proliferation of E.harbinense B49 cells,5mA/cm2 DC is inhibited fermentation hydrogen production bacteria metabolized glucose current density,0?2mA/cm2 could promote the growth and metabolism of E.Harbinese B49 to different degrees.In addition,the effect of current intensity used in the electrodialysis separation unit on the separation efficiency of the fermentation broth was discussed.Using 90cm2 carbon felt as the electrode material,the effect of separating the fermentation products at 90mA?lmA/cm2?,120mA?1.33mA/cm2?and 170mA?1.89mA/cm2?.The pH of the fermentation unit and concentration of acetic acid in the concentration chamber represente theBipolar membrane electrodialysis working condition,the pH values of the fermentation broth decreased continuously at the DC of 90mA and 120mA,the pH values decreased to 3.75 and 3.65 at the end of the reaction,and concentration of acetic acid in the concentration chamber were 210.54mg/L and 268.84mg/L.However,the system pH value of 170mA was stable at about 4.2 and the concentration of acetic acid was 1098.27mg/L at the end of the reaction.Therefore,170mA of DC can be bipolar membrane electrodialysis continuous and stable separation of acetic acid in the fermentation broth.Bipolar membrane electrodialysis and fermentation hydrogen production reactor were coupled,and continuous separation of acetic acid fermentation product continuously supplemented with glucose-based nutrients to observe changes in the fermentation of hydrogen production system of various substances to explore the hydrogen production efficacy and determine the optimal feed material.When fed with glucose,60.79mmol glucose was metabolized at the end of the reaction to obtain 79.10mmol acetic acid and 44.41mmol ethanol,accumulating 3120mL H2 and 1.34g/L biomass.When fed with basal medium,61₆6mmol acetic acid and 34.08mmol ethanol were obtained during the metabolism of 42.62mmol glucose,with a cumulative hydrogen production of 2290mL,cumulatively producing a cell dry weight of 1.69g/L.