| China’s textile industry has 2.37×109 tons of wastewater to be discharged every year,80%of which is printing and dyeing wastewater.If untreated wastewater is discharged into the water body,it will increase the chroma of the water body,prevent sunlight from entering the water body,and damage the ecological environment of the water body.At the same time,printing and dyeing wastewater contains a large number of toxic and harmful substances.A large number of printing and dyeing wastewater discharge has brought great challenges to the water treatment industry.Although some conventional water treatment technologies have been developed for this kind of wastewater,these technologies generally need to be used together to achieve a certain effect,and the cost of using these technologies is high.Microbial fuel cell（MFC）is a new renewable clean energy recovery technology,which can enrich and utilize microorganisms to degrade pollutants and recover energy simultaneously,so it has great potential in the field of wastewater treatment.However,the research of MFC has not yet made breakthrough progress.The low efficiency of ORR limits the main performance of MFC.Although commercial Pt/C catalysts have overcome the lack of ORR efficiency,the high price and short service life of Pt/C limit its large-scale application.To solve the problem of insufficient oxygen reduction recation dynamics and the high cost of cathode of MFC,a new ORR catalyst（Fe-N-PPC）with great potential was developed in this study.The cost of the catalyst is lower than that of Pt/C,and waste grapefruit peel is used as a raw material to achieve the purpose of waste recycling.In order to study the Fe-N-PPC catalyst in depth,a series of technologies are used to study its catalytic mechanism.Moreover,Fe-N-PPC is applied to the MFC to construct a Fe-N-PPC cathode MFC to degrade Congo red wastewater.The actual efficiency and degradation mechanism of the system were studied,and the influence of Fe-N-PPC catalyst on the microorganisms in MFC was deeply studied.X-ray diffraction spectroscopy（XRD）,scanning electron microscope（SEM）,X-ray energy spectroscopy（EDS）,and X-ray photoelectron spectroscopy（XPS）were used to analyze the microstructure,surface elements and morphology of Fe-N-PPC catalysts.The analysis confirmed the existence of Fe3C and Fe Nx active sites and the unique CNT structure;the electrochemical performance of the catalyst was studied by cyclic voltammetry（CV）,Tafel curve（Tafel）and electrochemical impedance spectroscopy（EIS）,The results show that Fe-N-PPC reduces the internal resistance by degrading the charge transfer resistance（Rct）of MFC,and its reduction peak current（4.6 A）and exchange current density(4.17×10-5 m A/cm2)are both higher than Pt/C catalyst;finally,the actual production conditions of sodium acetate substrate were degraded by Fe-N-PPC in the MFC to optimize the preparation conditions,and the preparation temperature of800℃and the precursor ratio of 2:1 was determined to be the preparation of Fe-N-PPC.Under the optimal conditions,the maximum power density of the Fe-N-PPC catalyst prepared under this condition reached 262.6 m W/m2,which was 34.6%higher than the power density of the Pt/C catalyst（172.0 m W/m2）.The effects of initial Congo red concentration,initial COD concentration,initial p H value and external resistance on the degradation of Congo red wastewater by Fe-N-PPC cathode MFC were investigated.The results show that the toxicity of Congo red dye can inhibit the performance of MFC.High concentration of COD and low external resistance are conducive to the degradation of dyes,and the neutral environment of the solution can improve the operation efficiency of the system.By comparing the effects of different cathodes on the degradation of Congo red,it was found that Fe-N-PPC has the best power generation performance,and the decolorization rate of Pt/C was more excellent,while the power generation and decolorization ability of PPC decreased significantly.Then,the effluent of MFC was detected by UV-Vis spectrophotometer and LC-MS.the results showed that Congo red could be effectively removed in this system.16S r RNA high-throughput sequencing was used to study the community structure of anodes.The results show that when the ORR performance of the cathode is weak,the activity of the anode biofilm is low,so the performance of the cathode and anode will limit the power generation efficiency of MFC at the same time;when the orr performance of the cathode is strong,the factor limiting the power generation of MFC is only the performance of the cathode.Geobacter,Acinetobacter and Comamonas are the main electrogenic bacteria and Proteobacteria is the main bacteria responsible for decolorization in Fe-N-PPC sample. |
