Advanced Treatment Of Dye Wastewater Through Bio-electro-Fenton Coupled With Polypyrrole Modified Cathode

Bio-electro-Fenton?BEF?system plays a critical role in the efficient,clean and low-energy-consuming biological processing technologies.BEF is used to in situ produce hydrogen peroxide within the cathode chamber via the electric current generated by the electrogenerating microorganisms using microbial fuel cell,and then generates hydroxyl radicals to degrade the pollutants through Fenton reaction in an attached catalytic oxidation reactor.In recent years,many researchers have focused on preparing efficient Oxygen Reduction Reaction?ORR?catalytic electrodes and continuously degrading pollutants by Bio-electro-Fenton.Based on BEF,microbial desalination fuel cell and catalytic oxidation reactor were coupled to carry out continuous degradation treatment of dye wastewater.In this study,investigation for the fabrication of cathode electrode,characterization of the internal structure,and catalytic procedure of electrode on reducing oxygen was also explored.In addition,the treatment ability of dye contaminant,power generation and electronic utilization were further analyzed,and the operating parameters of the system were optimized.Finally,degradative pathway of the simulated wastewater was revealed.Main results of this study were shown as follows:?1?The preparative conditions of polypyrrole modified carbon fiber electrode were:the ratio of pyrrole monomer:sodium dodecyl benzene sulfonate=0.15:0.15 mol L^-1,oxidation potential at 0.80 V vs.SCE,polymerization time of 600 s.The charge transfer resistance(R_ct)of the modified electrodes reached the minimum 66?cm^-2 under the optimum conditions.Through physical characterization was it found that the polypyrrole was linked by?-?linkage,sulfonic acid group on the dopant sodium dodecyl benzene sulfonate?SDBS?could form hydrogen bond with the polypyrrole chain,and the electrode appeared as"coir flower",while N forms in the whole modified carbon fiber were mainly pyrrole N and graphite N.?2?Under acid condition,polypyrrole modified carbon fiber electrode could reduce O₂ to H₂O₂ via 2 e^-1,while the‘insertion-ejection'reaction of cation could be regulated under neutral conditions,indicating that the electrode not only catalyzed the production of H₂O₂ by ORR but also had a migration effect on cations within the solution.In addition,an overpotential of 136mV could be obtained through the polypyrrole-modified carbon fiber electrode catalyzed the ORR reaction.?3?With polypyrrole modified electrode the cathode electrode,performance of microbial desalination fuel cell?MDC?would be greatly promoted at the continuous flow mode,the organic removal efficiency of the anode chamber reached 0.41 kg COD m^-3 d^-1,which was increased by 28.13%.Moreover,the desalination rate of the middle chamber reached 4.35 g L^-1 d^-1 and was increased by 42.62%,while the H₂O₂ production rate of the cathode chamber reached 7.01 g H₂O₂ m^-3 d^-1 and was increased by 724%.At the same time,electrical performance of MDC was also enhanced by the polypyrrole modified electrode at inner recirculation mode.The average current reached 5.12 mA,the coulombic efficiency reached3.24%,the Faraday efficiency reached 28.80%,and the COD conversion efficiency reached0.94%,which were increased by 48.27%,19.12%,484%,and 571%respectively.?4?The optimal continuous flow rate of the continuous flow MDC?cMDC?was 900?L min^-1 of which the internal resistance was only 78?,whereas the power density reached 566mW m^-3.The current generated by cMDC also increased with NaCl concentration,while Faraday efficiency of the cathode chamber reached the maximum of 31.76%when the adopted NaCl concentration was as 35 g L^-1.?5?The continuous flow microbial desalination fuel cell coupled with catalytic oxidation reactor?cMDC-COR?had a removal rate of 80.07%for methylene blue?MB?in 3 days,and the degradation ability was 1.7 and 1.6 times that of iron-carbon microelectrolytic material and cMDC respectively.The effluent of the system was analyzed by GC-MS,and two degradative pathways were propsed,of the both pathways MB was decomposed by advanced oxidation facilitated with radicals·OH,and was further degraded into yielded smaller biodegradable molecules.