Performance of electron acceptors in catholyte of a two-chambered microbial fuel cell using anion exchange membrane Soumya Pandit a , Arupananda Sengupta a , Sharad Kale b , Debabrata Das a,⇑ a Department of Biotechnology, Indian Institute of Technology, Kharagpur, India b Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Mumbai, India article info Article history: Received 15 August 2010 Received in revised form 5 November 2010 Accepted 9 November 2010 Available online 3 December 2010 Keywords: Electron acceptors Phosphate buffer Anion exchange membrane Initial pH abstract The performance of the cathodic electron acceptors (CEA) used in the two-chambered microbial fuel cell (MFC) was in the following order: potassium permanganate (1.11 V; 116.2 mW/m 2 ) > potassium persul- fate (1.10 V; 101.7 mW/m 2 ) > potassium dichromate, K 2 Cr 2 O 7 (0.76 V; 45.9 mW/m 2 ) > potassium ferricy- anide (0.78 V; 40.6 mW/m 2 ). Different operational parameters were considered to find out the performance of the MFC like initial pH in aqueous solutions, concentrations of the electron acceptors, phosphate buffer and aeration. Potassium persulfate was found to be more suitable out of the four elec- tron acceptors which had a higher open circuit potential (OCP) but sustained the voltage for a much longer period than permanganate. Chemical oxygen demand (COD) reduction of 59% was achieved using 10 mM persulfate in a batch process. RALEX™ AEM-PES, an anion exchange membrane (AEM), performed better in terms of power density and OCP in comparison to Nafion Ò 117 Cation Exchange Membrane (CEM). Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Microbial fuel cells (MFCs) can utilize organic substrates and subsequently convert their chemical energy to electricity using microorganisms. MFC represents an upcoming method for the sus- tainable production of energy, in the form of direct electricity from biodegradable compounds present in the wastewater, achieving simultaneous wastewater treatment (Thurston et al., 1985; Rabaey et al., 2003; Chaudhuri and Lovley, 2003; Logan and Regan, 2006). Microorganisms such as members of the Geobacter family (Bond and Lovley, 2003), Shewanella putrefaciens (Kim et al., 2002), Shewanella oneidensis (Ringeisen et al., 2005), Rhodoferax ferriredu- cens (Chaudhuri and Lovley, 2003), Pseudomonas aeruginosa (Rabaey et al., 2004), Clostridium butyricum (Park et al., 2001) and Aeromonas hydrophila (Pham et al., 2003) have been reported to oxidize the organic matter by donating electrons to the anode to complete their metabolic process. In spite of being a promising technology, MFC has some bottle- necks such as low power density, high cost etc. The factors which influence the performance of an MFC are substrate conversion rate, overpotentials at the anode and cathode, the ion exchange mem- brane performance, operational parameters, cell configuration and the electrode surface properties (Jadhav and Ghangrekar, 2009). The use of a suitable ion exchange membrane is essential for improving the efficiency of the MFC, Cation Exchange Membrane (CEM) are prevalently used in the MFC. The transport of cations other than protons through PEMs or CEMs leads to a decrease in the pH of the anodic chamber causing impairing of microbial activ- ity, while increasing the pH in the cathode chamber leads to reduc- tion of the cathode potential as well (Gil et al., 2003; Rozendal et al., 2006; Stenina et al., 2004). Moreover, Mo et al. (2009) and Liang et al. (2007) showed that the transferred cation precipitates on the surface of the cathode catalysts in a single-chamber MFC thereby increasing their internal resistance. On the other hand, use of an anion exchange membrane (AEM) results in improve- ment of the performance of the MFC compared to the traditional PEM/CEM (Kim et al., 2007; Mo et al., 2009; Rozendal et al., 2007; Zuo et al., 2008). Improved control for maintaining low pH gradient across the membrane can be achieved by using AEMs. The current production in MFCs is largely dependent on the reduction kinetics at the cathode. Hence in recent times lot of effort is being made to optimize and understand the reduction of the electron acceptor on the cathode surface (Li et al., 2009). Despite being cheap, abundant and having high redox potential, the use of oxygen as the terminal electron acceptor is limited by its slow reduction on the surface of the graphite/carbon electrodes (Gil et al., 2003). The power outputs of two-chamber MFCs using dissolved oxygen has been shown to be proportional to the concen- tration of the dissolved oxygen in the catholyte, which is limited in itself by the solubility of oxygen in water as also by the extraneous 0960-8524/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2010.11.038 ⇑ Corresponding author. E-mail address: ddas.iitkgp@gmail.com (D. Das). Bioresource Technology 102 (2011) 2736–2744 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech