Notes Bull. Korean Chem. Soc. 2010, Vol. 31, No. 6 1729 DOI 10.5012/bkcs.2010.31.6.1729 Performance of a Microbial Fuel Cell using a Magnet Attached Cathode Changho Choi, Mia Kim, † Seok Won Hong, ‡ Yong Su Choi, ‡ Young Il Song, § Sunghyun Kim, # and Hyung Joo Kim * Department of Microbial Engineering, Konkuk University, Seoul 143-701, Korea. * E-mail: hyungkim@konkuk.ac.kr † Department of Microbiology, Pusan National University, Busan 609-735, Korea ‡ Water Environment Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, Korea § EIA division, Korea Environment Institute, Eunpyeong, Seoul 122-706, Korea # Department of Bioscience and Biotechnology, Konkuk University, Seoul 143-701, Korea Received February 2, 2010, Accepted March 26, 2010 Key Words: Membrane-less microbial fuel cell, Magnet, Cathode reaction Multimeter External resistance DAQ system Air pump Wastewater Microbial fuel cell Drain Cathode Magnet PP felt Air regulator Anode Figure 1. Schematic diagram of the MLMFC system used in the study. Recently, a significant amount of attention has been focus- ed on renewable energy sources that might help to satisfy in- creasing demand for energy consumption and environmental protection. From this perspective, microbial fuel cells (MFCs) are becoming an attractive prospect, owing primarily to their concurrent activities in wastewater treatment and electricity generation using wastewater as a fuel. 1 An MFC is an electro- chemical device which converts chemical energy to electrical energy using the catalytic activities of microorganisms. In re- cent years, significant effort has been expended toward the de- velopment of biological (i.e. bacteria and/or enzyme, etc.) and non-biological components (i.e. electrochemical mediator, elec- trodes, membrane, MFC structure etc.) for use in MFCs. Despite recent efforts to improve the electrical power performance of MFCs, there remain many technological barriers to overcome before the practical operation of a stable electrical power source becomes feasible. 2 In the meanwhile, the membrane-less microbial fuel cell (MLMFC) using electrochemically active bacteria (EAB) is re- ceiving increased attraction, due to its simplicity and the relative inexpensiveness of its components as compared to a conven- tional MFC system-for example, the MLMFC does not require an electrochemical mediator or an ion-selective membrane. 3 One of the additional attractions of this type of arrangement is that it cannot merely generate electricity, but also consumes a broad range of practical organic wastes (e.g. animal or human sewage, organic wastewater from various fermentation pro- cesses, organic-rich sediment in freshwater and marine environ- ments), owing to the comparatively simplicity of its construc- tion. 4 Because MLMFCs can utilize renewable substrates as feedstock, they also offer the prospect of long-term eco-friendly electrical energy generation. The approaches described above, however, have solved only some of the problems associated with conventional MFCs, and there remains a continuing need for a reliable electrical power source that will allow for more eco-friendly electricity generation. Attempts to increase the performance of MFCs have yielded several alternative methods based on electrochemical reactions, including membrane modi- fication (e.g. membrane-electrode assembly), 5 and electrode modification (e.g. Pt catalyst coating, rotating electrode, appli- cation of conductive polymer etc.). 1,2,6,7 Previous studies have shown that a sufficient supply of oxy- gen, which functions as an oxidant for the cathode reaction, is one of the most crucial factors for the operation of MFCs. 8 Gaseous oxygen is a unique gas that evidences paramagnetic properties due to its parallel spins in the electron configuration of a molecule. 9 Due to this characteristic, the flow of oxygen gas can be controlled via magnetic force. It has recently been determined that this magnetic attractive force toward oxygen gas induces gas flow, and affects chemical reactions associated with oxygen gas-for example, combustion in diffusion flames and the cathode construction of a conventional chemical fuel cell. 8,9,10 In this study, we evaluated the effects of a constant magnet on the cathode of an MLMFC, and also assessed the electro- chemical performance of the magnet-attached MLMFCs. To the best of the authors’ knowledge, this is the first report con- cerning the application of a constant magnet for the enhanced performance of a microbial fuel cell. Experimental Procedures MLMFC construction. Fig. 1 shows a schematic diagram of the membrane-less microbial fuel cell (MLMFC) employed in this study. 3,5 The MLMFC consisted of an anode and cathode positioned at opposite sides of a poly-acrylic plastic cylindrical chamber (d = 120 mm, h = 200 mm, empty bed volume of ca. 2000 mL). Both the anode (d = 80 mm, t = 18 mm) and cathode (d = 60 mm, t = 6 mm) of the MLMFC were graphite felt (GF