Characteristics Of Anode Biofilm Formation And Proton Transport In Microbial Fuel Cell

With the development of society and the advancement of science and technology,the energy and environmental problems have gradually become two major challenges which mankind facing in the 21st century and severely constrain the survival of mankind and the sustainable development of society.In recent years,the extensive use of traditional fossil fuels has not only depleted fossil fuels but also seriously polluted the environment.At the same time,environmental problems,especially water pollution,have also become increasingly serious.At present,wastewater treatment in the traditional sewage treatment industry has always been in a"high-input,zero-output"state.Therefore,in order to ensure the sustainable development of society,it is imperative to find new clean energy sources and new wastewater treatment processes.In this context,Microbial Fuel Cell(MFC)technology came into being and gradually developed.MFC uses microorganisms as an anode catalyst to convert the chemical energy of organic matter in waste water into electrical energy,and it produces electrical energy while treating sewage,which is a kind of clean and pollution-free renewable energy plant.Due to its unique advantage of being able to generate electric energy while being treated with sewage,MFC has drawn wide attention from domestic and foreign scholars.However,at present,the problem of low output power of MFC and low power generation performance has become a big bottleneck of its commercial application.Among the many factors that affect MFC power generation performance,the anode performance plays a very important role.In this paper,from the viewpoint of engineering thermophysics,in view of the mass transfer of substrates and products in the MFC anode,the transmission characteristics of H~+in the anode biofilm and anodic micro pores,and the water transmission between anode and cathode caused by the H~+transmembrane are studied.In this paper,the mass transfer characteristics of H~+inside the anode biofilm of a microbial electrochemical system using carbon paper as anode material,and the mass transfer characteristics of H~+inside a three-dimensional anode graphite rod array constructed using a graphite rod as an electrode unit were studied.The water transfer characteristics between the cathode and the anode of a dual-chamber microbial fuel cell constructed using a carbon brush as an electrode material were studied.The main research results of this paper are as follows:1.Mass transfer phenomenon in anodic biofilms in microbial electrochemical system(BES).A microbial electrochemical system was constructed with carbon paper as the anode material.After the start-up,the mass transfer phenomenon in the anode biofilm was studied.The mass transfer characteristics of the anode biofilm were studied by scanning the microbial anode with cyclic voltammetry(CV curve),electrochemical impedance spectroscopy(EIS curve),and biofilm morphology.The results show that when using cyclic voltammetry to test the microbial anode,the CV curve of the anode varies with different scan rates or different numbers of turns at the same scaning speed,the smaller the scanning speed,the more severe the oxidation current in the CV curve drops after reaching the peak value.Under substrate-free conditions,the maximum peak current is proportional to the square root of the scan rate;electrochemical impedance analysis tests show that the mass transfer resistance of the microbial anode is much larger than the ohmic resistance and the charge transfer resistance.2.Formation of active biofilm and pH distribution studies in micro-pore(0.5 mm)A three-dimensional stainless steel wire anode array(10×10)of millimeter-level pores was constructed by using graphite rods(diameter is 0.9 mm),POM plates and PTFE hard tubes,two adjacent graphite rod spacing(the pore size)is 0.5 mm.The current distribution,internal resistance distribution,pH distribution,electron transfer modes of biofilm oxidation substrates and biofilm morphology were studied in three-dimensional anodes.The results shows:from the outside to the inside,the current of the three-dimensional anode arrays decrease continuously,the ohmic resistance and the mass transfer resistance are basically the same,but the charge transfer resistance increases gradually,the pH value and the the active biomass keeps decreasing,the thickness of biofilm gradually decreases.3.Water transport characteristics between cathode and anode of dual-chamber microbial fuel cell.In this section,a dual-chamber microbial fuel cell with carbon brush as anode and cathode material was constructed.The effect of“electro-osmotic drag”due to H~+trans-membrane transport on the water transport phenomena between cathode and anode was studied.The results show that the phenomenon of water transport between the cathode and anode of the dual-chamber MFC is closely related to the discharge current intensity,the phosphoric acid buffer(PBS)concentration of the cathode and anode,and the thickness of the proton exchange membrane.The larger discharge current intensity,the lower the concentration of the anodic PBS solution relative to the concentration of the cathode PBS solution,and the thinner the thickness of the proton exchange membrane,the greater the amount of water transport between the anode and the cathode.