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In this study, a microbial fuel cell (MFC) with granular activated carbon packed anode (GAC-MFC) is developed and compared with a MFC with granular graphite packed anode (GG-MFC), to evaluate the adsorptive effect of the granular activated carbon anode on MFC’s performance. The current output of GAC-MFC (11.1 mA, 18.1 mA and 21.6 mA) is much higher than that of GG-MFC (4.87 mA, 12.5 mA and 17.9 mA) at low substrate COD concentrations (∼50, ∼100 and ∼200 mg/L) when a low external resistance (20 Ω) and high circulation flow rate (20 mL/min) are applied. The half-saturation constant ( K s ) of GAC-MFC is about half as much as that of GG-MFC, suggesting that GAC-MFC has more affinity for anode substrate and deliver better kinetic performance than GG-MFC. Internal resistance distribution shows that mass diffusion resistance of GAC-MFC is at least 50% lower than that of GG-MFC when the substrate COD is ∼50 mg/L, indicating that the adsorptive effect of granular activated carbon packed anode helps to effectively facilitate mass transfer at low COD concentrations. Otherwise, the substrates adsorbed on GAC surface also serve to buffer the impact of COD concentration plummeting in bulk solution. [ABSTRACT FROM AUTHOR]

In this study, nitrogen-doped carbon nanotube (N-CNT) membrane compared with Pt-coated CNT (Pt-CNT) membrane and pristine CNT membrane were utilized as air cathode as well as filtration material of microbial fuel cells (MFCs). The MFCs were continuously operated for 39 days to investigate their power generation, organics removal, proton transfer, and fouling behavior under various influent concentrations and hydraulic retention times (HRTs). During operation, the N-CNT filtration MFC achieved the best effluent quality and power generation, with efficient removal of total organic carbon (TOC) (95.2%) and NH 4 + -N (97.7%), and maximum power density and current density of 408 mW/m 2 and 2.36 A/m 2 respectively. The excellent performance of the N-CNT MFC was mainly attributed to its special morphology and rich N-functional groups. The N-CNT membrane has a nanotube diameter of 37 ± 4 nm, pore size of 95 ± 33 nm, and porosity of 79.9%, which was even better than traditional microfiltration membrane as a filtration material for pollutant removal. The high nitrogen content (2.12 at%) and high specific surface area (93.5 m 2 /g) due to its network structure also enhanced O 2 reduction. In addition to the excellent performance of N-CNT cathode, the filtration operation enhanced cathode O 2 reduction by increasing mass transfer in cathode micro-pore and improving proton transfer with water flowing from anode to cathode. Moreover, a separate experiment also demonstrated that the cathode fouling could be mitigated under high current operation. [ABSTRACT FROM AUTHOR]