The Study On The Electricity Generation Of Sediment Microbial Fuel Cell And Its Application In Bioremediation

The development of human beings can not be separated from energy,the traditional fossil fuels are not renewable,and they will cause environmental pollution when they were used,so the traditional fossil fuel can not meet the sustainable development of human beings.The development of new energy,protection and restoration of the environment has become a solution to the two global problems of energy shortage and environmental pollution in the process of sustainable development of human beings.Sediment microbial fuel cells（SMFCs）is a technology to solve energy and environmental problems at the same time,to obtain renewable energy and to realize environmental bioremediation.According to the type of sediment,SMFC can be divided into activated sludge SMFC and lake sediment SMFC.Activated sludge SMFC can obtain high electricity production rate because of the high content of organic matter in sludge.However,during the operation,the biofilm attached to the surface of the cathode will affect the redox reaction of the cathode,reduce the electricity production performance of SMFC.The production efficiency of lake sediment SMFC is generally low,which is not conducive to collect electric energy,the bioremediation of Lake through in situ use of electric energy has become a hot research direction.In this paper,through rational design,carbon felt diaphragm was arranged on the sediment water interface of activated sludge SMFC to construct a carbon felt diaphragm SMFC,and its electric property and mechanism were studied.We constructed SMFC with sediment from lake and explored the influence factors of sediment source,cathode material and external resistance on SMFC bioremediation.The action mechanism of iron cathode in bioremediation is studied when zero valent iron was used as SMFC cathode.The study found that the carbon felt diaphragm SMFC could get higher total organic matter removal rate,and the power generation reached 376 mV,which was higher than the ordinary SMFC（332 mV）.The electrochemical impedance spectroscopy（EIS）,bacterial protein concentration and scanning electron microscopy（SEM）showed that the bacteria on the cathode of the carbon felt diaphragm SMFC could be significantly suppressed,thus reducing the protein concentration of the cathode and reducing the charge transfer resistance（from 118.9Ωto 91.6Ω）.This new carbon felt diaphragm SMFC can inhibit the growth of the biofilm by reducing the diffusion of organic matter in the sediment to the overlying water,which may accelerate the promotion and application of SMFC.In the lake sediment SMFC,the sediment of different sources had a significant effect on the denitrification of SMFC,and the removal rate of nitrate was up to 49.8%using the sediments from zizhuyuan,which has higher organic matter content.Different cathode materials had obvious effect on denitrification of SMFC.When iron sheet was used as cathode,the nitrate removal rate reached 54.3%.Further research on SMFC denitrification by different external resistors shows that the external resistance was 0Ω,that is,when a short circuit was formed,SMFC could use the generated electric energy in situ to obtain the best bioremediation effect,and the removal rate of nitrate was up to 78.8%.When the cathode of SMFC was zero valent iron,the bioremediation effect was most obvious.The mechanism of bioremediation of iron cathode was analyzed by SEM,XRD,protein concentration of biofilm,16S rRNA analysis and electrochemical characterization.It was found that during the operation of SMFC,the iron cathode was corroded,and there were bacterial attached to the cahtode.They formed a composite structure on the cathode surface.After the iron cathode SMFC running for 25 days,the iron oxide on the surface of iron cathode contained Fe₃O₄,which is consisted of Fe（II）and Fe（III）,and the cycle of the Fe（II）/Fe（III）would promote the transfer of electrons from the cathode to the nitrate.Compared with the control group,the autotrophic denitrifying bacteria Aeromonas sp.and Pseudomonas sp.were the dominant genera on the surface of SMFC cathode,which relative abundance was60.24%and 34.81%respectively.While the control group was mainly iron oxidizing bacteria and iron reducing bacteria.It is indicated that due to the role of SMFC,more bacterial grew on the cathode and the cathode microflora evolved.After forming the complex of iron oxide and bacteria,the SMFC cathode could improve the redox reaction of the cathode,reduce the charge transfer resistance,improve the electron transfer efficiency from the cathode to the nitrate,and then improve the bioremediation effect of the SMFC.In this paper,by solving the diffusion of organic matter from the activated sludge to overlying water,the electricity production performance of SMFC was significantly improved.At the same time,the reaction mechanism of SMFC in bioremediation was elucidated through the study of the iron cathode in short circuited SMFC.SMFC is a multidisciplinary technology,which still stays in the laboratory stage.This research provides new ideas and methods for solving the global energy shortage and environmental pollution problems through SMFC technology.It will also contribute to the further promotion and application of the technology.