title: Anolyte recirculation effects in buffered and unbuffered single-chamber air-cathode microbial fuel cells.
abstract: Two identical microbial fuel cells (MFCs) with a floating air-cathode were operated under either buffered (MFC-B) or bufferless (MFC-BL) conditions to investigate anolyte recirculation effects on enhancing proton transfer. With an external resistance of 50 Ω and recirculation rate of 1.0 ml/min, MFC-BL had a 27% lower voltage (9.7% lower maximal power density) but a 64% higher Coulombic efficiency (CE) than MFC-B. MFC-B had a decreased voltage output, batch time, and CE with increasing recirculation rate resulting from more oxygen transfer into the anode. However, increasing the recirculation rate within a low range significantly enhanced proton transfer in MFC-BL, resulting in a higher voltage output, a longer batch time, and a higher CE. A further increase in recirculation rate decreased the batch time and CE of MFC-BL due to excess oxygen transfer into anode outweighing the proton-transfer benefits. The unbuffered MFC had an optimal recirculation rate of 0.35 ml/min.
authors.affiliation: Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing 40003, China; Institute of Engineering Thermophysics, Chongqing University, Chongqing 400030, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing 40003, China; Institute of Engineering Thermophysics, Chongqing University, Chongqing 400030, China. Electronic address: zhuxun@cqu.edu.cn.
authors.forename: Xun
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, United States.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kashima
authors.affiliation: Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing 40003, China; Institute of Engineering Thermophysics, Chongqing University, Chongqing 400030, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing 40003, China; Institute of Engineering Thermophysics, Chongqing University, Chongqing 400030, China.
authors.forename: Ding-Ding
authors.initials: DD
authors.lastname: Ye
authors.affiliation: Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing 40003, China; Institute of Engineering Thermophysics, Chongqing University, Chongqing 400030, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Liao
authors.affiliation: Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, United States.
authors.forename: John M
authors.initials: JM
authors.lastname: Regan
mesh_terms: D000388:Air; D061249:Batch Cell Culture Techniques; D001674:Bioelectric Energy Sources; D057919:Biological Oxygen Demand Analysis; D004560:Electricity; D004566:Electrodes; D005240:Feasibility Studies; D006863:Hydrogen-Ion Concentration; D011522:Protons
chemical_list: D011522:Protons
keywords: Anolyte recirculation; Bufferless; Microbial fuel cell; Oxygen transfer; Proton transfer