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Anti-fouling performance and mechanism of anthraquinone/polypyrrole composite modified membrane cathode in a novel MFC–aerobic MBR coupled system

Xu, Lei, Zhang, Guo-quan, Yuan, Guang-en, Liu, Hai-yan, Liu, Jia-dong, Yang, Feng-lin
RSC advances 2015 v.5 no.29 pp. 22533-22543
ammonium nitrogen, anthraquinones, bioelectricity, catalytic activity, cathodes, chemical oxygen demand, cleaning, electrostatic interactions, energy recovery, fouling, free radicals, hydrogen peroxide, hydroxyl radicals, membrane bioreactors, microbial fuel cells, physicochemical properties, polyesters, pyrroles, sulfonates, wastewater treatment
In this study, an aerobic membrane bioreactor (MBR) equipped with anthraquinone–disulphonate/polypyrrole (AQDS/PPY) composite modified polyester (PT) flat membrane serving as the cathode of a dual-chamber microbial fuel cell (MFC) was developed for wastewater treatment, energy recovery and membrane fouling mitigation. Various physicochemical characteristic parameters were investigated to determine the surface properties of the AQDS/PPY/PT membrane. During most of the operation period, the chemical oxygen demand and NH₄⁺–N removal efficiencies of this novel MFC–MBR coupled system averaged 92.5% and 70.6%, respectively. Over the hydraulic retention time of 11.58 h and the external resistance of 1000 Ω, a maximum power density of 0.35 W m⁻³ and a current density of 2.62 A m⁻³ were obtained, meanwhile, the membrane fouling mitigation achieved the best status the H₂O₂ concentration in membrane effluent also reached the highest value of 2.1 mg L⁻¹. The effective membrane fouling mitigation was attributed mainly to the continuous self-generated bio-electricity of MFC, which not only accelerates the back-diffusion of negative charged foulants away from the membrane surface through the electrostatic repulsion, but also realizes membrane chemical cleaning through the in situ electrogenerated H₂O₂ and even ˙OH radicals on the membrane surface and/or inside the membrane pore from the self-sustainable heterogeneous electro-Fenton process. Though the electricity recovery of the MFC–MBR coupled system was much lower than other high-output MFC systems, this study provided a new insight into the membrane anti-fouling mechanism and will arouse extensive interests to explore more high-efficiency catalytic membrane materials to maximize power output and minimize membrane fouling.