Influence Of Birnessite Modified Electrode On MFC Cathode Denitrification Performance

Microbial fuel cell(MFC)is a bioelectrochemical system that converts chemical energy into electrical energy through microbial catalysis on the electrode.The quality of the electrode material directly affects the electron transfer performance in the MFC,which in turn affects the production of electricity and pollutants degradation.Studies have shown that the physical and chemical properties of the cathode material in the reactor directly affect the denitrification efficiency of MFC.In order to improve the denitrification efficiency of MFC cathode,birnessite was used to modify the cathode material.The conventional carbon-based cathode materials are modified with birnessite(B-1),birnessite doped with cerium(B-2),birnessite doped with cobalt(B-3),etc.,and the doped elements are adjusted The ratio and electrodeposition time are used to obtain modified electrodes with different performances.Physical and electrochemical tests are performed on them to initially evaluate the electrochemical performance of various modified materials and determine their optimal modification conditions.The experimental results show that the doping of metals such as cerium and cobalt in birnessite does not change the crystal structure,let alone generate separate oxides.When birnessite is doped with cerium(B-2),its specific capacitance is the largest and its electrochemical properties are excellent;when the doping ratio is different,it is found that when the molar ratio of Mn:Ce in B-2 is 10:1,its electrochemical properties are the best Good;the weight of the supported substance deposited for 10 minutes is 0.0017 g,the loading rate is 3.40%,and the birnessite cerium-doped carbon felt obtained when deposited for 10 minutes has the best electrochemical properties.The electrocatalytic denitrification experiment was carried out by comparing MFC with modified carbon felt electrode and ordinary carbon felt electrode as cathode.The removal rate of the reaction substrate in the modified cathode reactor was higher,and the effluent concentration after six hours of treatment Only 15.03mgL^-1(NO₃^--N) and 0.96 mg L^-1(NO₂^--N),the removal rate was 8.31% and 5.77% higher than that of conventional reactors.Indicating that the electrode has good conductivity after modification,and provides enough electrons for the cathode to carry out the reduction reaction,so the reaction substrate Have a higher removal rate.The ordinary carbon felt electrode (M1) and the modified electrode (M2) were respectively composed of an MFC reactor,and their effects on the start-up and electricity generation performance of MFC were compared.During the start-up of the reactor,the cathode potential of M2 stabilized at-170.00±3.68mV,compared with the M1 output voltage(193.00±3.40mV),its stable voltage is 37.00±8.48 mV higher,and M2 obtains a stable voltage of at 12d before M1,the maximum power density of the M2 reactor can reach 2.96W m^-3;the COD removal rate of the anode and cathode of the M2 reactor is increased by 14.82%and 10.02%,respectively,and the total nitrogen removal rate of the cathode is increased by 9.05%;The results indicate that the cathode electrode modified with Ce can improve the start-up process and electrical performance of MFC,and further promote the denitrification efficiency of the reactor.Biological denitrification was studied in the M1 and M2 reactors to analyze the effect of pollutants removal and electricity generation performance,and to evaluate the efficiency of the water sodium manganese ore modified electrode as MFC cathode in the process of denitrification.After applying constant potential,the nitrate effluent concentration and total nitrogen removal rate of M1 and M2 reactors can reach 18.00mgNL^-1,46.55%and 15.31 mgNL^-1,56.96%respectively;when no constant potential is applied,its M2 The total nitrogen removal rate of the reactor is 7.05%higher than that of the M1,but when a constant potential is applied,the total nitrogen removal rate of the M2 reactor is 10.41%higher than that of the M1;it shows that the reactor composed of modified carbon felt is due to its rough surface,It is more suitable for the growth of biofilms,and the conductivity is also better,resulting in a better denitrification effect.