Microbial Fuel Cell Membrane Research Articles

Next‐Generation Proton‐Exchange Membranes in Microbial Fuel Cells: Overcoming Nafion's Limitations

The adoption of microbial fuel cell (MFC) technology hinges on the development of efficient proton‐exchange membranes (PEMs), which significantly influences fuel cell performance and cost. PEMs have a critical role in preventing oxygen crossover, maintaining electrochemical neutrality, and supporting microorganisms within MFCs. Nafion, the current industry‐standard PEM, grapples with environmental, cost, and performance issues. Although improvements to Nafion have been reported using additives, immersion in heteropolyacids, different pretreatment methods, and UV irradiation, many of the challenges still remain. Herein, the recent developments in the area of alternative PEMs are reviewed and analyzed. Among them, sulfonated aromatic hydrocarbons, particularly sulfonated polyether ether ketone, have emerged as top contenders in terms of scale up and commercial viability. At the same time, membranes based on polyvinyl alcohol, ionic liquids, and natural materials are also being actively researched for various MFC applications. Since most studies are short term and lab scale, there is a need evaluate long‐term stability and economic cost of PEMs in terms of standardized parameters such as power‐to‐cost and normalized energy recovery. Additionally, for emerging low‐energy‐density MFC applications like biosensors and in vivo power sources, PEM properties and design need to be tailored carefully.

Recent Advances in the Development of Sustainable Composite Materials used as Membranes in Microbial Fuel Cells.

MFC can have dual functions; they can generate electricity from industrial and domestic effluents while purifying wastewater. Most MFC designs comprise a membrane which physically separates the cathode and anode compartments while keeping them electrically connected, playing a significant role in its efficiency. Popular commercial membranes such as Nafion, Hyflon and Zifron have excellent ionic conductivity, but have several drawbacks, mainly their prohibitive cost and non-biodegradability, preventing the large-scale application of MFC. Fabrication of composite materials that can function better at a much lower cost while also being environment-friendly has been the endeavor of few researchers over the past years. The current review aims to apprise readers of the latest trends of the past decade in fabricating composite membranes (CM) for MFC. For emphasis on environmental-friendly CM, the review begins with biopolymers, moving on to the carbon-polymer, polymer-polymer, and metal-polymer CM. Lastly, critical analysis towards technology-oriented propositions and realistic future directives in terms of strengths, weakness, opportunities, challenges (SWOC analysis) of the application of CM in MFC have been discussed for their possible large-scale use. The focus of this review is the development of hybrid materials as membranes for fuel cells, while underscoring the need for environment-friendly composites and processes.

Cost effective, high proton conductive and low oxygen crossover novel modified biochar doped microbial fuel cell membrane

The current study focuses on synthesizing a cost-effective high proton conductive and low oxygen crossover proton exchange membrane. The membrane is prepared using modified biochar from chili stalk waste in a sulfonated polyether sulfone polymer for microbial fuel cell applications for tamarind wastewater treatment. The membrane shows desired modification confirmed through instrumental characterization using FTIR, XRD, TGA, and SEM. The ultimate analysis confirmed the high carbon and nitrogen content in modified biochar that induces elevated proton conductivity (0.098 Scm−1) and less oxygen diffusivity (3.33 × 10-8 m2 s−1) in a 5% modified biochar doped sulfonated polyether sulfone membrane with a desired mechanical strength, IEC, and moisture content. The high oxygen reduction reaction due to nitrogen content in modified char enhances columbic efficiency and bacterial activity that eventually improves the MFC performance in terms of high-power density (0.148 Wcm−2) and 82.2% of COD elimination. The presence of graphitic and pyridinic, pyrrolic, and N groups accompanying carbon structures favor oxygen reduction via the 2e− or 4e− pathway, respectively. Finally, molecular dynamics simulation also confirmed the low oxygen diffusion and reduced fraction-free volume for oxygen diffusion after including modified biochar in SPES. The economic assessment shows a five times lower cost of modified biochar doped membrane than Nafion 117 membrane.

Optimal aeration area of cathode electrode in the batch type of microbial fuel cells with non-woven interface

Microbial fuel cells (MFCs) are based on the biochemical reaction of microorganisms to decompose organic wastewater for converting chemical energy into power energy. MFCs are considered an environmentally friendly technology that is gaining popularity due to their simultaneous digestion and energy production abilities. To enhance its real application in wastewater treatment, this study proposes to use a non-woven material for replacing the usage of expensive membranes in MFCs. In addition, the study aims to consider a series of different aeration areas of cathode electrodes for finding an optional design. Results have shown that the adoption of non-woven with 0.45 μm can effectively prohibit the diffusion of oxygen into the anode chamber. Moreover, the non-woven material played an important role as an interface between the anode and cathode, enhancing the MFC performance. The usage of suitable non-woven material can replace the role of the membrane when applied in real wastewater applications. The results have shown that the case study where a combination of a 50% aeration area of the cathode electrodes with 25% exposure of the cathode plate in the air yielded relatively better aeration in terms of a higher current density of 250 mA/m2, higher power density of 220 mW/m2, and higher open voltage circuit of 0.4 V, compared to other case studies considered. These results indicate the optimal aeration configuration for MFCs applied in commercial wastewater treatment in the future.

Investigating the Performance of a Zinc Oxide Impregnated Polyvinyl Alcohol-Based Low-Cost Cation Exchange Membrane in Microbial Fuel Cells.

The current study investigated the development and application of lithium (Li)-doped zinc oxide (ZnO)-impregnated polyvinyl alcohol (PVA) proton exchange membrane separator in a single chambered microbial fuel cell (MFC). Physiochemical analysis was performed via FT-IR, XRD, TEM, and AC impedance analysis to characterize thus synthesized Li-doped ZnO. PVA-ZnO-Li with 2.0% Li incorporation showed higher power generation in MFC. Using coulombic efficiency and current density, the impact of oxygen crossing on the membrane cathode assembly (MCA) area was evaluated. Different amounts of Li were incorporated into the membrane to optimize its electrochemical behavior and to increase proton conductivity while reducing biofouling. When acetate wastewater was treated in MFC using a PVA-ZnO-Li-based MCA, the maximum power density of 6.3 W/m3 was achieved. These observations strongly support our hypothesis that PVA-ZnO-Li can be an efficient and affordable separator for MFC.

Strategic development and performance evaluation of functionalized tea waste ash-clay composite as low-cost, high-performance separator in microbial fuel cell

ABSTRACT The separator is an important component of the microbial fuel cells (MFCs), which separates anode and cathode entities and facilitates ion transfer between both. Despite the high research in separators in recent years, the need for cost-effective, waste-driven selective separators in MFCs persists. Present study discloses the strategic fabrication of functionalized-tea-waste-ash-clay (FTWA-C) composite separator by integrating functionalized tea waste ash (FTWA) with potter’s clay. Clay was used as a base, while FTWA was used as cation exchanger. FTWA and clay were separately mixed in four different ratios, 00:100 (C1); 05:95 (C2); 10:90 (C3); 15:85 (C4). Mixtures were then crafted manually as consecutive four layers. C1-side faced anode while separator-cathode-assembly was developed at C4. The separator was characterized by evaluating proton and oxygen transfer coefficient, and water-uptake analysis. The separator was also analysed for elemental composition, microstructure, particle size, and surface area and porous structure. SEM analysis of FTWA showed the presence of 15–100 nm pores. EDS analysis of the FTWA-C showed the presence of hygroscopic oxides, mainly SO4 2− and SiO2. A slight peak observed at P/P o∼1, confirmed the presence of macropores. The FTWA-C separator showed proton transfer coefficient as high as 18.7 × 10−5 cm/s, and oxygen mass transfer coefficient of 2.1 × 10−4 cm/s. The FTWA-C displayed the highest operating voltage of 612.4.2 mV, the power density of 1.81 W/m3, and COD removal efficiency of 87.52%. The fabrication cost of this separator was estimated to be $9.8/m2. FTWA-C could be an affordable and high-efficiency alternative for expensive ion-exchange membranes in MFCs.

Recent Development of Polymer Based Membranes in Microbial Fuel Cells

Recent Development of Polymer Based Membranes in Microbial Fuel Cells

The Implications of Membranes Used as Separators in Microbial Fuel Cells.

Microbial fuel cells (MFCs) are electrochemical devices focused on bioenergy generation and organic matter removal carried out by microorganisms under anoxic environments. In these types of systems, the anodic oxidation reaction is catalyzed by anaerobic microorganisms, while the cathodic reduction reaction can be carried out biotically or abiotically. Membranes as separators in MFCs are the primary requirements for optimal electrochemical and microbiological performance. MFC configuration and operation are similar to those of proton-exchange membrane fuel cells (PEMFCs)—both having at least one anode and one cathode split by a membrane or separator. The Nafion® 117 (NF-117) membrane, made from perfluorosulfonic acid, is a membrane used as a separator in PEMFCs. By analogy of the operation between electrochemical systems and MFCs, NF-117 membranes have been widely used as separators in MFCs. The main disadvantage of this type of membrane is its high cost; membranes in MFCs can represent up to 60% of the MFC’s total cost. This is one of the challenges in scaling up MFCs: finding alternative membranes or separators with low cost and good electrochemical characteristics. The aim of this work is to critically review state-of-the-art membranes and separators used in MFCs. The scope of this review includes: (i) membrane functions in MFCs, (ii) most-used membranes, (iii) membrane cost and efficiency, and (iv) membrane-less MFCs. Currently, there are at least 20 different membranes or separators proposed and evaluated for MFCs, from basic salt bridges to advanced synthetic polymer-based membranes, including ceramic and unconventional separator materials. Studies focusing on either low cost or the use of natural polymers for proton-exchange membranes (PEM) are still scarce. Alternatively, in some works, MFCs have been operated without membranes; however, significant decrements in Coulombic efficiency were found. As the type of membrane affects the performance and total cost of MFCs, it is recommended that research efforts are increased in order to develop new, more economic membranes that exhibit favorable properties and allow for satisfactory cell performance at the same time. The current state of the art of membranes for MFCs addressed in this review will undoubtedly serve as a key insight for future research related to this topic.

Ceramic membrane modified with rice husk ash for application in microbial fuel cells

Ceramic membranes have been widely used as an affordable cation exchange membrane in microbial fuel cells (MFCs). This study deals with the fabrication of low-cost ceramic membranes by blending rice husk ash (RHA) with soil for its application in MFCs. Ceramic membrane having 10% RHA exhibited higher proton mass transfer and lower oxygen diffusion. The presence of silica in RHA enhanced the hydration properties of the membrane and aided proton mobility form anode to cathode chamber. Performance of the MFCs using modified (with RHA, MFCT) and unmodified (without RHA, MFCC) membrane was evaluated for the treatment of rice mill wastewater under continuous mode operation. The maximum volumetric power densities were 2.14 W mˉ3 and 1.33 W mˉ3, and COD removal efficiencies were 70.7 ± 1.24% and 63.8 ± 1.08% for MFCT and MFCC, respectively. Form the electrochemical impedance spectroscopy (EIS) study, ohmic resistance (RΩ) of MFCC and MFCT was found to be 91.3 Ω and 47.1 Ω, respectively. The RHA composite membrane displayed less tendency of membrane fouling, making it more favorable for long-term operation. This study reveals that the RHA composite membrane could serve as a suitable alternative to expensive polymeric membranes in MFC with higher power performance and minimum oxygen diffusion.

Microbial Fuel Cell Membrane Bioreactor in Wastewater Treatment, Electricity Generation and Fouling Mitigation

AbstractMembrane bioreactors (MBR) have gained much attention due to their ability to achieve higher treatment efficiency. However, high external energy consumption in aeration for membrane fouling mitigation has been limiting their application. Microbial fuel cells (MFC) can ideally extract energy from wastewater in the form of electricity and reduce membrane fouling. Thus, the use of MFC‐MBR is rapidly expanding. However, the MFC‐MBR design and operation is not fully mature and further research is needed to optimize the process efficiency and enhance the applicability. This review gives an overview of recent studies on the performances of MFC‐MBR systems, regarding the design and configuration of the integrated system, irrespective of whether optimization was done or not in the operating system.

Development and Application of Supported Ionic Liquid Membranes in Microbial Fuel Cell Technology: A Concise Overview.

Membrane separators are key elements of microbial fuel cells (MFCs), especially of those constructed in a dual-chamber configuration. Until now, membranes made of Nafion have been applied the most widely to set-up MFCs. However, there is a broader agreement in the literature that Nafion is expensive and in many cases, does not meet the actual (mainly mass transfer-specific) requirements demanded by the process and users. Driven by these issues, there has been notable progress in the development of alternative materials for membrane fabrication, among which those relying on the deployment of ionic liquids are emerging. In this review, the background of and recent advances in ionic liquid-containing separators, particularly supported ionic liquid membranes (SILMs), designed for MFC applications are addressed and evaluated. After an assessment of the basic criteria to be fulfilled by membranes in MFCs, experiences with SILMs will be outlined, along with important aspects of transport processes. Finally, a comparison with the literature is presented to elaborate on how MFCs installed with SILM perform relative to similar systems assembled with other, e.g., Nafion, membranes.

Microbial Fuel Cell-Membrane Bioreactor Integrated System for Wastewater Treatment and Bioelectricity Production: Overview

AbstractEconomic development and the related increase in global energy demands have created pressure on the supply of energy resources. To promote sustainable development, a safe and renewable ener...

Applications of Nanoscale Polypyrrole Proton Exchange Membrane in Microbial Fuel Cells

Applications of Nanoscale Polypyrrole Proton Exchange Membrane in Microbial Fuel Cells

Energy recovery and hygienic water production from wastewater using an innovative integrated microbial fuel cell–membrane separation process

Abstract In this study, wastewater treatment was destined for generation of electricity and hygienic water by an innovative integrated microbial fuel cell – membrane separation process (MFC-MSP). An optimal antifouling nanofiltration membrane (blended with O-carboxymethyl chitosan bound Fe3O4 magnetic nanoparticles (CC Fe3O4 NPs)), an antifouling ultrafiltration (UF) membrane (blended with polycitrate-alumoxane nanoparticle (PC-A)) and a high efficiency proton exchange membranes were applied in MSP and MFC processes. Firstly, the performance of MFC unit under different operating conditions of reaction time (RT), mixed liquor suspended solid (MLSS) concentration and influent chemical oxygen demand (COD) concentration was investigated in terms of COD removal efficiency and power generation for synthetic dairy wastewater treatment. The experiments were modeled using response surface methodology (RSM). The results indicated that by increasing in RT and CODin concentration, the COD removal was decreased. Also, the high concentration of MLSS in anodic chamber led to high COD removal efficiency. By increasing of MLSS beyond 3000 mg/L, the maximum power generation was decreased that reveals an adverse impact of biofouling on membrane performance. After primary treatment in anodic chamber of MFC at optimum condition, the anodic chamber effluent was passed through the membranes in two modes, direct nanofiltration (NF) membrane and UF-NF membranes in series. The results indicated that the UF membrane alleviated the organic loading of NF membrane by 72% relative to the direct NF filtration. The permeation flux shows a sustain performance of the NF when is coupled with UF membrane.a.

Improving the performances of Nafion™-based membranes for microbial fuel cells with silica-based, organically-functionalized mesostructured fillers

Abstract Microbial Fuel Cells (MFCs) can be conveniently used for wastewater treatment and bioelectricity production. Their efficiency is strongly influenced by the physico-chemical properties of the ion-conducting membrane. In this work we prepare Nafion™-based composite membranes by using mesoscale SBA-15 silica, and organic-inorganic fillers obtained by functionalizing SBA-15 with SO3H groups. The proposed membranes are tested as alternative separators in MFCs for applications in wastewater treatment and their performances compared to those of standard Nafion™ 117. Prolonged (3 months) MFC operation shows that the composite membrane with 5 wt% of SBA-15 functionalized with 10 mol% of SO3H gives maximum power density of 380 mW m−3, namely three times better than that of Nafion™ after 90 days of operation. The same membrane offers a very effective COD removal after 14 days (more than 95%), an impressive coulombic efficiency of 34%, and very high resistance to biofouling. We conclude that the use of silica-based SO3H functionalized fillers is a powerful strategy to improve the performances of Nafion™ membranes in MFCs.

Characterization of Polyester Cloth as an Alternative Separator to Nafion Membrane in Microbial Fuel Cells for Bioelectricity Generation Using Swine Wastewater.

Polyester cloth (PC) was selected as a prospective inexpensive substitute separator material for microbial fuel cells (MFCs). PC was compared with a traditional Nafion proton exchange membrane (PEM) as an MFC separator by analyzing its physical and electrochemical properties. A single layer of PC showed higher mass transfer (e.g., for O₂/H⁺/ions) than the Nafion PEM; in the case of oxygen mass transfer coefficient (ko), a rate of 50.0 × 10⁻⁵ cm·s⁻¹ was observed compared with a rate of 20.8 × 10⁻⁵ cm/s in the Nafion PEM. Increased numbers of PC layers were found to reduce the oxygen mass transfer coefficient. In addition, the diffusion coefficient of oxygen (DO) for PC (2.0-3.3 × 10⁻⁶ cm²/s) was lower than that of the Nafion PEM (3.8 × 10⁻⁶ cm²/s). The PC was found to have a low ohmic resistance (0.29-0.38 Ω) in the MFC, which was similar to that of Nafion PEM (0.31 Ω); this resulted in comparable maximum power density and maximum current density in MFCs with PC and those with Nafion PEMs. Moreover, a higher average current generation was observed in MFCs with PC (104.3 ± 15.3 A/m³) compared with MFCs with Nafion PEM (100.4 ± 17.7 A/m³), as well as showing insignificant degradation of the PC surface, during 177 days of use in swine wastewater. These results suggest that PC separators could serve as a low-cost alternative to Nafion PEMs for construction of cost-effective MFCs.

Evaluation of energy-distribution of a hybrid microbial fuel cell–membrane bioreactor (MFC–MBR) for cost-effective wastewater treatment

A low-cost hybrid system integrating a membrane-less microbial fuel cell (MFC) with an anoxic/oxic membrane bioreactor (MBR) was studied for fouling mitigation. The appended electric field in the MBR was supplied by the MFC with continuous flow. Supernatant from an anaerobic reactor with low dissolved oxygen was used as feed to the MFC in order to enhance its performance compared with that fed with synthetic wastewater. The voltage output of MFC maintained at 0.52±0.02V with 1000Ω resister. The electric field intensity could reach to 0.114Vcm−1. Compared with the conventional MBR (CMBR), the contents rather than the components of foulants on the cake layer of fouled MFC–MBR system was significantly reduced. Although only 0.5% of the feed COD was translated into electricity and applied to MBR, the hybrid system showed great feasibility without additional consumption but extracting energy from waste water and significantly enhancing the membrane filterability.

A method based on impedance spectroscopy for predicting the behavior of novel ionic liquid-polymer inclusion membranes in microbial fuel cells

MFCs (microbial fuel cells) are an emerging technology for simultaneous treatment of wastewater and energy recovery. These devices exploit microbial metabolism to generate electricity from organic matter. The separator is a critical factor in the design of MFCs as it plays a crucial role in the transport of protons from the anode to the cathode, affecting the performance of the cell. It is thus of interest to develop a method to predict the behavior of a separator before being used in MFCs. The present work proposes a new method based on spectroscopy to calculate the internal resistance of several PIMs (polymer inclusion membranes) based on ILs (ionic liquids) and predict their behavior as novel proton exchange membranes in MFCs. Four types of PIMs based on three different groups of ionic liquids were prepared and electrochemically characterized: Methyltrioctyl ammonium chloride, [MTOA+][Cl−], 1-methyl-3-octylimidazolium hexafluorophosphate, [OMIM+][PF6−], Tri-butylmethylphosphonium methylsulphate, [P4,4,4,1+][MeSO4−], and Triisobutyl-(methyl)-phosphonium tosylate, [PI4,I4,I4,1+][TOS−], some of which were patented by our research group to be used as separator in MFCs (P201330453). Finally, the PIMs were evaluated in MFCs for energy production and wastewater treatment and compared with Nafion®117. The results show that the [PI4,I4,I4,1+][TOS−]-based membrane outperformed the rest of separators in terms of power output.

Use of Bacterial Cellulose from Gluconacetobacter hansenii NOK21 as a Proton-permeable Membrane in Microbial Fuel Cells

An acetic acid bacterium NOK21 from the pellicle on the surface of rancid wine was isolated and identified as Gluconacetobacter hansenii based on morphological, physiological, and genetic characteristics. When the bacterial isolate was grown in static broth containing ethanol, a maximum pellicle concentration of 5.2 g/? was obtained at 3% ethanol concentration and a maximum acidity of 3.97% was reached at 5% ethanol concentration. At ethanol concentrations higher than 6%, no bacterial growth was observed. Analysis with solid state 13C-NMR spectroscopy showed that the pellicle from the NOK21 culture was composed of a relatively pure cellulose polymer and had a few carboxylate (COO-) groups. Also, observation of the pellicle with SEM revealed a multi-layer network structure where nano-diameter cellulose fibers were tangled together at random. The pellicle cellulose polymer was used as a proton-permeable membrane in a microbial fuel cell (MFC) and had about a 3-fold higher efficiency for electric power generation than a cation exchange membrane Neosepta CMX. Moreover, electric power was generated stably at 150-200 mW/m2 per anode surface area. These results suggest that the microfibril cellulose membrane from the NOK21 culture may be suitable for use as an alternative to expensive proton exchange membranes in MFCs.

A review on the role of proton exchange membrane on the performance of microbial fuel cell

Proton exchange membranes (PEMs) are the most frequently used separators in microbial fuel cells (MFCs). The role of proton transportation in MFC performance makes PEMs one of the most important components in the cell. The effect of PEMs in MFC performance is commonly determined according to generated power density and coulombic efficiency. Nafion is the commonly used membrane in MFCs, but there are still a number of problems associated with the use of Nafion including oxygen transfer rate, cation transport and accumulation rather than protons, membrane fouling and substrate loss. Moreover, additional problems can also be attributed to the effect of PEMs including internal resistance and pH change in MFCs. Recent developments in PEM performance are attributed to two categories including utilization of other types of membranes and improvements in Nafion by pre-treatment methods. Copyright © 2014 John Wiley & Sons, Ltd.