Study On The Performance Of Modified Electrode Microbial Fuel Cell In The Treatment Of Nitrobenzene Wastewater

Nitrobenzene is a typical nitroaromatic compound,which has great harm to the human body（teratogenic,carcinogenic and mutagenic）.How to achieve green,clean and efficient treatment of nitrobenzene wastewater has important research significance.Microbial fuel cell（MFC）is due to its highly efficient catalytic performance.And it can provide electricity while treating waste water,which has a good prospect in terms of pollutant removal and microbial power generation.Therefore,this article prepares modified electrodes for MFC cathode treatment of nitrobenzene wastewater,optimizes its influencing factors,and designs a series MFC continuous flow system to improve the mass transfer and treatment capacity of MFC.In this study,three modified electrodes,Fe/Fe₂O₃/polyaniline/polyethylene glycol/carbon felt（Fe/Fe₂O₃/PANI/PEG/CF）,Fe/Fe₂O₃/PEG/CF,and PANI/PEG/CF,were prepared first.Three modified electrodes and blank CF were used as cathode electrodes for the treatment of nitrobenzene wastewater in MFC cathodes,and their superiority in degradation and electricity generation performance was investigated.Afterwards,the structure characterization and electrochemical performance test of the modified electrode and blank CF were carried out.And choose the optimal electrode Fe/Fe₂O₃/PANI/PEG/CF as the cathode material to continue research.Further study the role of Fe/Fe₂O₃/PANI/PEG/CF electrode+microorganism,Fe/Fe₂O₃/PANI/PEG/CF electrode,and various parts of microorganisms in the degradation of nitrobenzene wastewater.The experimental results show that the removal rate of nitrobenzene,the removal rate of COD and the output voltage of the modified electrode on the MFC cathode are all higher than that of the blank CF.Among them,the Fe/Fe₂O₃/PANI/PEG/CF electrode has the best effect.The removal rates of nitrobenzene and COD after 48 hours of reaction are90.06%and 84.54%,respectively.Scanning electron microscope（SEM）analysis showed that the surface of the modified Fe/Fe₂O₃/PANI/PEG/CF electrode carbon fiber became rough and the specific surface area increased.Through cyclic voltammetry（CV）and electrochemical impedance spectroscopy（EIS）electrochemical tests,it is found that the oxidation and reduction peaks of Fe/Fe₂O₃/PANI/PEG/CF are the strongest,and the ohmic resistance is the smallest,the diffusion resistance is the largest,and the electrode The modification increases the active sites on the surface of the carbon fiber and improves the activity of the electrode material.The combined action of the modified electrode and the microorganism plays a synergistic effect on the removal and mineralization of nitrobenzene,and the cathode microorganism can be used as a catalyst to increase the transfer rate on the electronically modified electrode.Secondly,as the degradation and electricity generation performance of MFC are affected by a variety of parameters,the preferred electrode Fe/Fe₂O₃/PANI/PEG/CF is used as the cathode and anode electrode.Five parameters of resistance,temperature,nitrogen content,sludge volume,and initial nitrobenzene concentration were selected to optimize the MFC.The experimental results show that the optimum resistance,temperature,nitrogen content and sludge volume are 600Ω,35℃,no external nitrogen source and 80 m L sludge volume.In the bio-cathode MFC under the above optimum conditions,the removal rates of nitrobenzene and COD were 94.12%and 88.97%after the reaction of 80 mg/L nitrobenzene for 48 h,and the concentration of nitrobenzene increased to 240 mg/L.After 48 h,the removal rates of nitrobenzene and COD were 80.00%and 49.89%,respectively.The optimization of conditions significantly improved the removal effect of nitrobenzene,and high-concentration nitrobenzene has certain limitations in a single MFC system.Finally,in view of the limited removal efficiency of a single MFC for nitrobenzene,this paper designed a series MFC cathode-cathode continuous flow system（MFC1-MFC2）.The cathode/anode electrodes are all Fe/Fe₂O₃/PANI/PEG/CF.In this mode,the effluent from the cathode chamber 1 is used as the continuous feed of the cathode chamber 2.The experimental results show that the reduction products of nitrobenzene caused by electron transfer under closed-circuit conditions are more likely to be mineralized,and the removal rate of COD under closed-circuit conditions was 16.86%higher than that under open-circuit conditions.As the concentration of nitrobenzene increases,the difference in the removal rate of nitrobenzene between MFC1 and MFC2 increased.The nitrobenzene concentration increased to 240 mg/L can still maintain a certain nitrobenzene removal rate,and the COD removal rate of the final effluent of MFC2 under different nitrobenzene concentrations was higher than 92.43%.Correspondingly,as the concentration of nitrobenzene increases,the output voltage of both MFCs increased.Gradually reducing the co-substrate glucose concentration found that with the decrease of glucose concentration,the removal rate of nitrobenzene increased,and the output voltage of MFC also showed an upward trend.The intermediate product of MFC2 effluent after2 h,6 h and 24 h was identified by GC-MS.Intermediate products such as phenylhydroxylamine,o-hydroxyaniline,phenol,（1Z,3Z）-butadiene-1,4-diol and oxalic acid were detected by GC-MS.The possible degradation pathways of nitrobenzene in this system are proposed through the analysis of intermediate products.The series MFC cathode-cathode continuous flow system greatly improves the salinity of nitrobenzene.This flow system allows more available substrates in the cathode biofilm for microbial consumption,enables microbial bacteria to fully contact pollutants,improves the mass transfer effect of the reactor,and expands the amount of pollutants handled by MFC.Therefore,this system provides a new strategy for the effective treatment of nitrobenzene wastewater.