The Study Of Methane Production Performance From Reducing Carbon Dioxide In Microbial Electrosynthesis System

With the rapid consumption of fossil fuels,a large amount of greenhouse gas carbon dioxide is produced,and the problems of control and emission reduction of CO₂ have been highly concerned by all countries in the world.Using the bioelectrochemical system to reduce carbon dioxide has become an effective means of carbon dioxide utilization.This study had constructed a double chamber microbial electrosynthesis system?MES?,and using carbon fiber as the electrode material,the anaerobic activated sludge of large granular sludge reactor treating starch wastewater as the inoculum source for enrichment.We investigated the effects of environmental temperatures,applied potentials and anthraquinone-2-sulfonic acid,sodium salt,monohydrate?AQDS?on the reduction of CO₂ by MES,and the microbial community structure was also analyzed.The main contents and conclusions of this paper were as follows:1.As the temperature was increased from 15 ? to 50 ?,both the yield and rate of methane production increased simultaneously,but reduced when temperature was further increased to 65? and 70 ?.The current increases as the temperature increases gradually,while the coulombic efficiency of methane formation in the cathode was in a range of 19.15±2.31% to 73.94±2.18%,mainly due to by-products formation such as hydrogen and volatile fatty acids?VFAs?.The most suitable temperatures for methane production from CO₂ by MES was 35 ? ⁵0 ?.2.As the cathode potential was decreased from-0.70 to-0.90 V vs Ag/AgCl,both the yield and the rate of methane production were increased simultaneously,and the current was also substantially increased.Continue reducing the applied potential to-1.0 V,there was almost no methane production,and a large amounts of hydrogen emerged,while the coulombic efficiency on methane production in the cathode was in the range of 49% to 90%,and by-products formation also were hydrogen and VFAs.Therefore,the production of methane from CO₂ by MES must be controlled within a certain range of potentials3.In the process of anaerobic biodegradation,an electron mediator was introduced,which had higher activity and stability in biological enzymes,and could reduce the transmission barriers between electron donor and receptor,accelerate the electron transfer rate.The electronic media of AQDS was added into the culture medium in MES,and started the reactor under a certain applied potentials and temperatures,it was found AQDS could promote methane production from CO₂ by electrochemical reduction.4.A variety of microorganisms were found on the surface of biofilm through scanning electron microscopy?SEM?,and the morphologies of them were mainly in rods and spheres.16 S rRNA sequencing demonstrated that Methanobacterium was the predominant methanogen in the biocathode of the MES.The results showd that different temperatures and applied potentials had some effect on the structure of the functional microorganisms even to the growth and metabolism.