Performance Enhancement Study Of MnO₂@rGO Modified Stainless Steel Mesh Cathode Membrane For MFC-MBR Coupled System

Membrane bioreactor（MBR）,as a new wastewater treatment technology,has received wide attention and research because of its small footprint and stable treatment effect.However,the technology suffers from serious membrane contamination,high energy consumption and maintenance costs during practical application,thus limiting its further development.Microbial fuel cell（MFC）is a green power generation technology capable of recovering pollutants and has a wide application prospect,but its treatment effect on wastewater is poor.The coupling of MBR and MFC can make up for each other’s shortcomings,as the electrical energy generated by MFC can supplement the energy consumption of the system and alleviate membrane contamination,while MBR can ensure the water treatment effect of the system.The MnO₂@rGO modified stainless steel mesh cathode membrane is used as the cathode of the MFC-MBR coupling system,which can promote the cathode oxygen reduction reaction and further improve the system performance.In this paper,the attachment of MnO₂ and rGO（reduced graphene oxide）on a fine stainless steel mesh was achieved by electrochemical deposition,and a composite structure with high redox activity was formed.The basic properties of the composite catalyst were characterized by SEM,TEM,Raman and FT-IR.The results showed that the MnO₂ nanoparticles were covered and wrapped by rGO,and the structure suppressed the particle aggregation phenomenon during the reaction.To further investigate the performance of the composite catalytic oxygen reduction reaction,electrocatalytic degradation experiments were conducted by varying the applied voltage intensity and initial p H conditions.The best degradation efficiency of the composites was achieved at an applied voltage of-5 V and p H=7.The MnO₂@rGO modified stainless steel mesh cathode membrane was proven to be the best by studying the degradation effect of different modified stainless steel mesh on rhodamine B under the same conditions.Meanwhile,the cyclic voltammetric curves showed that the composites possessed strong redox peaks at-0.4～0 V,which further proved their excellent catalytic oxygen reduction reaction ability.The MnO₂@rGO modified stainless steel mesh cathode membrane was made into a conductive membrane assembly and applied to the coupled MFC-MBR system.Firstly,the microorganisms in the anode anaerobic sludge and cathode aerobic sludge were domesticated by using synthetic wastewater as the feed water source to make the sludge flocs hang on the anode and cathode.The output voltage of the system was around 200 m V after successful start-up operation.Then,the operation of the coupled MFC-MBR system was compared with different modified stainless steel mesh as the cathode membrane,including electricity production performance,water treatment performance and resistance to membrane contamination.The results showed that the application of MnO₂@rGO modified stainless steel mesh cathode membrane significantly improved the power production performance of the MFC-MBR coupled system,with the maximum power density reaching 1.59 W/m~3 and the Coulomb efficiency increasing to 5.9%.In wastewater treatment,the removal of COD in the anode chamber was significantly improved,while the removal of COD and ammonia nitrogen in the system reached up to 93%and 97.8%.In addition,the membrane contamination process was analyzed by means of TMP,Zeta potential and electrochemical tests.The application of modified stainless steel mesh cathode membrane can strengthen the electric field strength on the membrane surface and affect the electronegativity of the sludge mixture,making the sludge particles easier to flocculate and less likely to be deposited,and significantly improving the anti-membrane contamination performance during operation.In summary,the modified cathode membrane MFC-MBR coupling system has good electrical production performance and wastewater treatment effect.It can effectively suppress membrane contamination,which provides a reference for the performance optimization and scale up application of the MFC-MBR coupling system.