Separators are needed in microbial fuel cells (MFCs) to reduce electrode spacing and preventingelectrode short circuiting. The use of nylon and glass fiber filter separators in single-chamber, air-cathodeMFCs was examined for their effect on performance. Larger pore nylon mesh were used that had regular meshweaves with pores ranging from 10 to 160 μm, while smaller pore-size nylon filters (0.2 – 0.45 μm) and glassfiber filters (0.7 – 2.0 μm) had a more random structure. The pore size of both types of nylon filters had adirect and predictable effect on power production, with power increasing from 443±27 to 650±7 mW/m2forpore sizes of 0.2 and 0.45 μm, and from 769±65 to 941±47 mW/m2for 10 to 160 μm. In contrast, changes inpore sizes of the glass fiber filters resulted in a relatively narrow change in power (732±48 to 779±43 mW/m2)for pore sizes of 0.7 to 2 μm. An ideal separator should increase both power density and coulombic efficiency(CE). However, CEs measured for the different separators were inversely correlated with power production,demonstrating that materials that reduced the oxygen diffusion into the reactor also hindered proton transportto the cathode, reducing power production through increased internal resistance. Our results highlight the needto develop separators that control oxygen transfer and facilitate proton transfer to the cathode.
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