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[Display omitted] • Aerotolerant bioanode was constructed with small external resistance or high shear stress. • Aerotolerant biofilm was flat and compact with a large laminar boundary layer for reducing oxygen diffusion. • Compact electrode assembly MFC with aerotolerant bioanode achieved a power density of 4300 mW/m2. Reducing electrode spacing is considered the most effective way to maximize the power density of microbial fuel cell (MFC) due to the effective reduction of internal resistance. However, reducing electrode spacing presents the challenge of diffusing oxygen from the cathode to the anode, thereby reducing anode performance. Constructing aerotolerant anode may be one of the effective ways to minimize the effect of oxygen on anode performance. Here, we report that using small external resistance or maintaining high nitrogen sparging rate during bioanode enrichment could significantly enhance the aerotolerant characteristic of the bioanode. The voltage loss affected by oxygen was significantly reduced and, as a result, the power density of the compact electrode assembly MFC increased by 85% reaching 4300 mW/m2. The aerotolerant bioanode had a flat and compact biofilm structure and a larger laminar boundary layer (over 300 μm) to reduce oxygen diffusion, while the aerointolerant bioanode had a rough and porous biofilm structure and a smaller laminar boundary layer (less than 80 μm). The microbial community of all the bioanodes was dominated by Geobacter (over 55%). Therefore, this study provides a sample way to construct an aerotolerant bioanode for high power generation in MFCs. [ABSTRACT FROM AUTHOR]

Inoculum is critical for the start-up and performance of microbial fuel cells (MFCs). The effluent of mature MFCs is usually used as inoculum for the start-up of immature MFCs. However, the effluent of mature MFCs contains bacteria both from anode biofilm (ASB) and cathode biofilm (CSB). Here, ASB and CSB and their mixtures were used as inoculum in the start-up of MFCs in order to gain more insight into the influence of CSB on the start-up of MFCs. Compared to anode inoculum-enriched MFCs, using cathode inoculum reduced start-up time from 5 d to 3 d. The time needed for scavenging oxygen was reduced from 900 min to 600 min, maximum power density was 19% lower (691 mW/m2 vs 823 mW/m2), and the charge transfer resistance increased from 29.0 Ω to 48.3 Ω. The decreased start-up time and power generation of cathode inoculum-enriched MFCs was attributed to the increasing abundance of Azospirillum (80.02% vs. 12.68%) and the decreasing abundance of Geobacter (9.08% vs. 61.25%). This research suggested that CSB in the effluent of mature MFCs, when used as inoculum, has a side-effect on the start-up of MFCs. [ABSTRACT FROM AUTHOR]

Poor anode performance is one of the main bottlenecks in the development of microbial fuel cells (MFCs) for practical applications. Multilayered Ti 3 C 2 MXene (m -MXene) is an alternative anode modification material because of its high specific surface area and electrical conductivity. However, the multilayered structure, negatively charged surface, and electropositivity of m -MXene could limit its modification effects. In this work, we used a solution-phase flocculation method (ammonium ion method) to restack and aggregate MXene nanosheets as an anode modification material (n-MXene). The n-MXene-modified anode had a higher specific surface area, surface hydrophilicity and surface electropositivity than the m -MXene-modified anode. The n-MXene-modified anode obtained a maximum current density of 2.1 A m−2, which was 31.2% and 61.5% higher than that of the m -MXene-modified anode (1.6 A m−2) and bare carbon fiber cloth anode (1.3 A m−2). This improved anode performance was attributed to both the decrease in the charge transfer resistance and diffusion resistance, which were related to the increased quantity of biomass and microbial nanowire (or pili)-shaped filaments on the electrode surface. This work provides a simple and cost-effective approach to prepare MXene nanosheets for the modification of MFC anodes. [Display omitted] • An ammonium ion method was used to restack and aggregate of multi-layered MXene. • Modifying ammonium treated MXene increased hydrophilic and surface charge of anode. • Anode performance increased 61.5% with the modification of ammonium treated MXene. • Modifying ammonium treated MXene increased biomass and conductive matrix of biofilm. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) have the potential for simultaneous electricity generation and nitrogen removal in the treatment of wastewater that contains nitrate, but the denitrification of nitrate might affect electricity generation in single-chamber MFCs. In this study, the effect of nitrate on electricity generation in single-chamber air cathode MFCs was investigated. The chemical oxygen demand (COD) was removed faster by denitrification (0.977 ± 0.013 g COD g −1 NO 3 − ) than by electricity generation in the MFCs. When the concentration of COD that excluded the COD removed by denitrification was more than 300 mg O 2  L −1 , denitrification only resulted in the decrease in the voltage of the MFCs at the denitrification stage, but did not affect the stable voltage and maximum power density (MPD) of the MFCs after the denitrification stage. The average MPDs during the 660-day batch operation ranged from 27.4 ± 0.9 to 28.4 ± 1.2 W m −3 . At the same concentration of COD that excluded the COD removed by denitrification, the coulombic efficiency of the MFCs after the denitrification process increased with an increasing initial concentration of nitrate, which was probably attributed to the inhibition of the activity of certain non-exoelectrogenic bacteria by nitrate. A microbial community analysis showed that Thauera was the dominant genus of denitrifying bacteria and Geobacter was the dominant genus of exoelectrogenic bacteria at the anodes of the MFCs. With an increase in the initial concentration of nitrate, the proportion of denitrifying bacteria increased, whereas the proportion of exoelectrogenic bacteria decreased. [ABSTRACT FROM AUTHOR]

• Plasma oxidation and microbial fuel cell was combined for mineralization of MB dye. • Fast plasma treatment effectively improved the biodegradability of MB dye. • Mineralization percentage of combined process increased by 2.7 times. • Specific mineralization energy consumption of combined process decreased by 58.2%. • Degradation pathway of MB was analyzed. Plasma advanced oxidation process (PAOP) has great ability to break recalcitrant pollutants into small molecular compounds but suffers from poor performance and low energy efficiency for mineralizing dyeing pollutants. Combining advanced oxidation process with biodegradation process is an effective strategy to improve mineralization performance and reduce cost. In this study, a combined process using PAOP as pre-treatment followed by microbial fuel cell (MFC) treatment was investigated to mineralize methylene blue (MB). The PAOP could degrade MB by 97.7%, but only mineralize MB by 23.2% under the discharge power of 35 W for 10 min. Besides, BOD 5 /COD ratio of MB solution raised from 0.04 to 0.38 while inhibition on E. coli growth decreased from 85.5% to 28.3%. The following MFC process increased MB mineralization percentage to 63.0% with a maximum output power density of 519 mW m−2. The combined process achieved a mineralization energy consumption of 0.143 KWh gTOC−1 which was only 41.8% of that of PAOP. FT−IR, UV–vis and pH variation demonstrated that PAOP could break the aromatic and heterocyclic structures in MB molecule to form organic acids. Possible degradation pathways of MB were accordingly proposed based on LC–MS, GC–MS, and density functional theory calculation. [ABSTRACT FROM AUTHOR]