Chemical Engineering Journal 147 (2009) 259–264 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Phenol degradation in microbial fuel cells Haiping Luo a , Guangli Liu a,∗ , Renduo Zhang a , Song Jin b a School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, Guangdong 510275, China b Western Research Institute, Laramie, WY 82072, USA article info Article history: Received 13 March 2008 Received in revised form 25 June 2008 Accepted 2 July 2008 Keywords: Electricity generation Microbial fuel cell MFC Phenol degradation Biodegradation abstract Microbial fuel cell (MFC) has gained a great attention attributable to its ability in generating electric- ity directly from and potentially enhancing biodegradation of contaminants. In this study, MFCs using phenol or glucose–phenol mixture as the substrate (fuel) were designed to investigate the biodegrada- tion of phenol. In an aqueous air cathode MFC using phenol (400 mg/L) as the sole fuel, electricity was generated during the phenol degradation. The degradation rates of phenol in the MFC increased about 15% as compared to the open-circuit control. Further experiments were conducted by using a graphite- packed MFC with a ferricyanide cathode. When phenol served as the sole fuel, the peak voltage output was obtained when 90% of phenol was depleted. A unique pattern of twin voltage peaks was observed when phenol–glucose mixture was used as the fuel. At the occurrence of the first and second voltage peaks, phenol was degraded by 20% and 90%, respectively, suggesting a preferential sequence in sub- strate consumption. The maximal power densities were 9.1 and 28.3W/m 3 for MFCs using phenol and glucose–phenol mixture as the fuel, respectively. Co-occurring with electricity generation, the degrada- tion efficiencies of phenol in all the MFCs reached above 95% within 60 h. The results indicate that the MFC can enhance biodegradation of recalcitrant contaminants such as phenol in practical applications. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Microbial fuel cells (MFCs) have been operated successfully by using a variety of readily degradable compounds, such as glucose, acetate, monosaccharides, and complex carbohydrates (e.g., starch and biodegradable organics in food wastewater, swine wastewater, and domestic wastewater), as substrates (the fuel) [1–5]. In a few cases, some biorefractory organics, such as cellulose and petroleum contaminants, were also used as the fuel in MFCs [6,7]. The near- term application for MFCs was presumed to generate power from wastewater [8]. The amount of power produced from the MFCs varies on the specific sources of the fuel. For example, with simi- lar designs of the MFC, 506 mW/m 2 was produced with acetate [3], but 261 mW/m 2 with swine wastewater [2], and 146 mW/m 2 with domestic wastewater [9]. Toxic and biorefractory organics, which were found frequently in the wastewater, have a great influence on the wastewater treatment and should be concerned in the related MFC research. However, the development of MFCs using recalci- trant contaminants as fuels is still in its infancy and warrants further research. ∗ Corresponding author. Tel.: +86 20 84110052; fax: +86 20 84110692. E-mail addresses: liugl@mail.sysu.edu.cn, luohaiping2004@126.com (G. Liu). Phenol has been detected in effluents from industries, including coal gasification, pharmacy, and productions of pesticides, fertiliz- ers, dyes, and other chemicals. Although phenol is biodegradable both aerobically and anaerobically, it can be growth inhibitory to microorganisms at elevated concentrations, even to those species that can use it as a substrate [10]. Degradation of phenol was also found incomplete for concentrations higher than 400 mg/L, and the residual phenol might inhibit the removal of N and P in wastewater treatment [11]. In the anaerobic environment, phenol was degraded by methanogens, denitrifying, iron bacteria, and sulfate-reducing bac- teria [12–14]. However, methane-producing processes have not been widely used due to low energy recovery from phenol and high operational costs [15]. In the MFC, electricity can be produced directly from the degradation of organic matter and high energy recovery can be obtained [16]. While under the denitrifying, iron, and sulfate-reducing conditions, the exhaustion of these electron acceptors may prevent the complete degradation of phenol, and the anaerobic degradation rates are usually lower than that under aer- obic conditions. In the MFC, electrons released from the substrate oxidation in the anode are transferred via the external circuit to the cathode, where the electrons are eventually consumed by the terminal electron acceptors. The terminal electron acceptors can be easily replaced or even non-exhausted (e.g., using oxygen in ambi- ent air as the electron acceptor) [7]. Combining with the benefit 1385-8947/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2008.07.011