We compared novel size-selective separators, namely the textile fabrics of polyphenylene sulfide (PPS) and sulfonated polyphenylene sulfide (S-PPS), and the nonwoven fabrics of polypropylene80 (PP 80) and PP 100, with commonly used ion exchange separators (Nafion 117 and cation exchange membane-7000; CMI-7000) in terms of power generation, oxygen diffusion, and biofilm formation in a single chamber microbial fuel cell. Size-selective separators exhibited more power generation than ion selective separators. MFC operation with size-selective separators generated power output ranging 0.407 to 0.591 V (1000 Ω), whereas with Nafion it was 0.272 V. In polarization analysis, S-PPS resulted in the highest power density of 190 mW/m 2 , whereas it was 24 mW/m 2 with Nafion-117. Size selective separators showed similar or higher proton conductivity than Nafion 117. Oxygen mass transfer coefficients of size-selective separators (K O = 3.77 .5 10 -5 ) were lower or similar to Nafion (K O = 7.5 10 -5 ).Fourier-transform infrared spectroscopy and scanning electron microscopy analysis revealed that all separators (PP80, S-PPS, and Nafion) contained proteins or carbon chain compounds after 300-day operation, and however, Nafion 117 seems to be more susceptible to biofouling than the other separators.

No abstract

The performance of a single chamber microbial fuel cell (MFC) with a low-cost polypropylene separator was investigated at various electrode interspaces in a separator electrode assembly (SEA). The lag period was shortened (3.74-0.17 days) and voltage generation was enhanced (0.2-0.5 V) as electrode spacing was increased from 0 to 9 mm. Power density was increased from 220 to 370 mW/m with increased spacing. The highest power density of 488 mW/m was obtained in polarization analysis with 6 mm. The oxygen mass transfer coefficients with 0 mm (K = 3.69 × 10 cm/s) electrode spacing were 3.8 times higher than with 9 mm (K = 0.96 × 10 cm/s) spacing. Columbic efficiency (CE) was increased from 5 to 32% due to less oxygen diffusion with increase in electrode spacing, but on contrary the ohmic resistance (R ) was increased from 2 to 4 Ω. In a long-term operation (200 days), a gradual decrease in cathode potentials was observed in all electrode spacing as the main limiting factor of stable MFC performance.

Microbial fuel cells (MFCs) have gathered attention as a novel bioenergy technology to simultaneously treat wastewater with less sludge production than the conventional activated sludge system. In two different operations of the MFC and aerobic process, microbial growth was determined by the protein assay method and their biomass yields using real wastewater were compared. The biomass yield on the anode electrode of the MFC was 0.02 g-COD-cell/g- COD-substrate and the anolyte planktonic biomass was 0.14 g-COD-cell/g-COD-substrate. An MFC without anode electrode resulted in the biomass yield of 0.07 ± 0.03 g-COD-cell/g-COD-substrate, suggesting that oxygen diffusion from the cathode possibly supported the microbial growth. In a comparative test, the biomass yield under aerobic environment was 0.46 ± 0.07 g-COD-cell/g-COD-substrate, which was about 3 times higher than the total biomass value in the MFC operation.