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For successful field-scale application of microbial fuel cell (MFC), the power recovery from field-scale MFC needs to be improved considerably with simultaneous reduction in its fabrication cost. These problems can be addressed by applying low-cost and efficient cathode catalyst in MFCs. In this regard, Cu0.5Mn0.5Fe2O4 (CuMnFe) was synthesized and applied as cathode catalyst in lab and field-scale MFCs with capacity of 150 ml and 25 l, respectively. Lab-scale MFC having CuMnFe as cathode catalyst demonstrated power density of 176.0 ± 8.2 mW m-2, which was competitive with MFC having Pt as cathode catalyst (183.0 ± 12.6 mW m-2) and it was about seven times higher than control MFC (25.5 ± 4.5 mW m-2) having no catalyst. Application of CuMnFe as cathode catalyst in field-scale MFC produced power density of 7.74 mW m-2, which was three-times higher than the power produced by the field-scale MFC operated without any cathode catalyst (2.58 mW m-2). The cathode catalyst CuMnFe also demonstrated excellent anti-biofouling properties, which in turn improved the power production of field-scale MFC. Therefore, low-cost CuMnFe can be anticipated as an efficacious cathode catalyst for application in MFCs that would produce long term stable higher power, while offering simultaneous treatment to wastewater. [ABSTRACT FROM AUTHOR]

There has been a considerable increment in the atmospheric CO2 concentration, which has majorly contributed to the problem of global warming. This issue can be extenuated by effectively developing microbial electrosynthesis (MES) for the sequestration of CO2 with the concurrent production of biochemical and biofuels. Though the MES technology is in its infancy, it has exhibited enormous potential for sustainable mitigation of CO2 and bioelectrosynthesis of multi-carbon organic compounds. The problem of storage of excess renewable electrical energy by conventional means can also be alleviated by employing MES, which stores it in the form of C–C bonds of chemicals. This review focuses on the various aspects of MES and recent developments made in this field to overcome its bottlenecks, such as the lower yield of organic compounds, separation of products of higher chain organic compounds, etc. In particular, the microbial catalysts and cathode materials employed in MES have also been emphasized. Keeping in mind the potential of this innovative technology, researchers should focus on improving the yield of MES by developing novel low-cost cathode materials and discovering efficient and robust micro-organisms, which would be a significant step forward towards the further advancement of this technology. [ABSTRACT FROM AUTHOR]

Proton exchange membranes (PEMs) were synthesized in polyvinyl alcohol (PVA) matrix by impregnating TiO2-Si or SrTiO3-Si as proton exchanger for microbial fuel cells (MFCs). These PEMs were physically characterized, which approved the presence of hygroscopic oxides like SiO2 to increase the proton transfer due to the formation of Si-H along with the water channelling through TiO2 or SrTiO3 induced microstructural modifications. Chemical characterization techniques further illustrated their comparable performance to the commercially available Nafion-117 and superior performance than bare PVA membrane. Polarization curves for MFCs using TiO2-Si- or SrTiO3-Si-based PVA membranes exhibited a power density of 6.16 ± 0.31 W m−3 and 5.39 ± 0.27 W m−3, respectively. Power density of MFC with TiO2-Si membrane was comparable to that of the MFC using Nafion-117 (6.50 ± 0.33 W m−3). Thus, comparable properties and 30-folds less synthesis cost of the fabricated TiO2-Si-impregnated PVA membrane in comparison to Nafion, demonstrate its potential for real-life applications in MFC. [ABSTRACT FROM AUTHOR]

Sodium dodecyl sulfate (SDS) is a widely used anionic surfactant, which finds its way to the receiving water body due to the incapability of conventional wastewater treatment systems to completely remove it. A hybrid treatment system consisting of upflow microbial fuel cell (MFC) with titanium dioxide (TiO2) as a photocathode catalyst was developed for treating synthetic wastewater spiked with SDS (10.00 ± 0.46 mg L−1). Effluent from anodic chamber of MFC was passed through raw laterite soil filter followed by the photo-cathodic chamber with TiO2-coated cathode irradiated with the UV spectrum. This hybrid system was operated under varying hydraulic retention time (HRT) in anodic chamber of MFC. The SDS removal efficiency of more than 96% along with organic matter removal efficiency of more than 71% was obtained by this hybrid system at different HRTs. The MFC having cathode coated with TiO2 could generate a maximum power density of 0.73 W m−3 and 0.46 W m−3 at the HRT of 12 h and 8 h, respectively, showing the adverse effect of increased SDS loading rate on the electrical performance of MFC. This investigation highlighted the importance of HRT in anodic chamber of MFC and offered solution for effective removal of surfactant from wastewater. [ABSTRACT FROM AUTHOR]

Catalysts play an essential role in various electrochemical reactions followed during the synthesis of hydrogen peroxide (H2O2). Plenty of investigations on the role of catalysts in the synthesis of H2O2 have been made in recent times. In this regard, palladium (Pd) is the most favored catalyst used by the researchers for the production of H2O2; however, monometallic Pd catalysts hydrogenate H2O2 if no acids or halide stabilizers are used. Nowadays, direct synthesis of H2O2 is mainly furnished by active metal-based catalysts such as gold, palladium, nickel, platinum, iron, silver, or manganese. However, the alloys of Au-Pd/C, Ni-Pd/C, and Au-Pd/TiO2 are also being encouraged because of their increased electrochemical activity. The efficacy of H2O2 production is highly dependent upon the type of cathode catalyst used and the pH of the solution. The electro-Fenton process, which uses Fenton reagents (dissolved Fe+2 and H2O2) to produce hydroxyl ions, is also an effective method for the degradation of biorefractory organic pollutants present in wastewater. This novel process can be made feasible if H2O2 can be produced in situ. In situ H2O2 production can be particularly important and attractive for tertiary treatment of sewage and for the removal of emerging contaminants. Thus, this mini review focuses on the effectiveness of various metal-based catalysts and the application of bioelectrochemical systems for the synthesis of H2O2. [ABSTRACT FROM AUTHOR]

Waste generation from healthcare facilities now has become a concerning issue as it contain plastic and metals. Medicine wrappers are one of the major portions of healthcare solid waste, which impel intensive solid waste management practice due to fewer possibilities of deriving by-products. However, it can be recycled and used as an electrode material in microbial fuel cells (MFCs). An electrode material for application in MFCs is a crucial component, which governs total fabrication cost as well as power recovery, thus a cost-effective, stable and durable electrode is essential. In this endeavour, a new metallic (aluminium) waste material, a waste medicine wrapper (WMW), was evaluated for feasibility to be used as anode/cathode in MFCs. Based on the stability test under corrosive environment (1 N KCl), the WMW electrode sustained a maximum current of 46 mA during cyclic voltammetry (CV) and noted only 14% reduction in current at an applied voltage of +0.4 V after 2500 s in chronoamperometry, indicating its good stability. Power recovery from MFC using WMW was higher than the MFC using bare carbon felt as an anode (27 vs. 21 mW/m2). The entire analytical test results viz. CV, electrochemical impedance spectroscopy and power performance established WMW as an excellent anode rather than cathode material. [ABSTRACT FROM AUTHOR]

Low cost tungsten oxide/bismuth tungstate (WO3/Bi2WO6) composite was synthesized and used as cathode catalyst in microbial fuel cell (MFC). Almost 1.5 times increment in specific surface area of WO3/Bi2WO6 composite was observed as compared with WO3 and WO3/Bi2WO6 exhibited efficient oxygen reduction reaction (ORR) having a current peak of 8.1 mA at - 12.6 mV during cyclic voltammetry analysis, demonstrating less ORR overpotential. The MFC using WO3/Bi2WO6 catalysed cathode could recover a power density (PD) of 145 ± 4.5 mW/m2 and coulombic efficiency (CE) of 28.3 ± 1.5%, followed by 35 ± 5.8 mW/m2 and 17.5 ± 2.4%, respectively, for MFC with WO3 catalyzed cathode and 10.4 ± 3.2 mW/m2 and 10.3 ± 0.9%, respectively, for MFC without any cathode catalyst. Moreover, the PD and CE of 138 ± 6.8 mW/m2 and 27.5 ± 2.0%, respectively, obtained from MFC using Pt/C cathode catalyst, was slightly lower than the MFC with WO3/Bi2WO6 catalyst on cathode. The specific power recovery per unit cost of cathode fabrication of 23.8 mW/$ obtained from MFC with WO3/Bi2WO6 catalyzed cathode is higher than the MFC with Pt/C (12.2 mW/$), making it low cost alternative for scaling-up of MFCs. [ABSTRACT FROM AUTHOR]

Cu-Sn bimetallic alloy supported on acetylene black was prepared and tested under different loadings per unit cathode surface area viz. 1 mg.cm-2, 2 mg.cm-2 and 5 mg.cm-2 as a catalyst to improve the oxygen reduction reaction (ORR) and to enhance performance of the microbial fuel cell (MFC). Electrochemical analyses were performed to evaluate the ORR kinetics. Results of cyclic voltammetry showed multiple redox current peaks for all the loadings of Cu-Sn with positive onset potential of ~0.25 V. Among different loadings, cathode with Cu-Sn loading of 2 mg.cm-2 proved to be the best choice for application in MFC, due to less charge transfer resistance and high redox current. Power density and coulombic efficiency of 470 mW.m-2 and 36%, respectively, were obtained from MFC using Cu-Sn catalyzed cathode with a loading of 2 mg.cm-2, which was higher than the MFCs using cathodes with 1 and 5 mg.cm-2 of Cu-Sn loadings and it was even found slightly higher than the MFC using Pt-C catalyst on cathode. Power generation per unit cost of catalyst for MFC using Cu-Sn catalyst was found to be 11-fold higher than the MFC using Pt-C cathode, ascertaining former as low-cost cathode catalyst for harvesting more power from MFCs. [ABSTRACT FROM AUTHOR]

Methanogenic substrate loss is reported to be a major bottleneck in microbial fuel cell (MFC), which significantly reduces the power production capacity and coulombic efficiency (CE) of this system. Nitroethane is found to be a potent inhibitor of hydrogenotrophic methanogens in rumen fermentation process. Influence of nitroethane pre-treated sewage sludge inoculum on suppressing the methanogenic activity and enhancing the electrogenesis in MFC was evaluated. MFC inoculated with nitroethane pre-treated anodic inoculum demonstrated a maximum operating voltage of 541 mV, with CE and maximum volumetric power density of 39.85% and 20.5 W/m3, respectively. Linear sweep voltammetry indicated a higher electron discharge on the anode surface due to enhancement of electrogenic activity while suppressing methanogenic activity. A 63% reduction in specific methanogenic activity was observed in anaerobic sludge pre-treated with nitroethane, emphasizing the significance of this pre-treatment for suppressing methanogenesis and its utility for enhancing electricity generation in MFC. [ABSTRACT FROM AUTHOR]

Electrosynthesis of multi-carbon compounds from the carbon dioxide present in biogas is a nascent approach towards purification of biogas. Microbial electrosynthesis (MES) cells, fabricated using different electrode materials, were operated using different electrolytes and mixed anaerobic culture as biocatalysts in the cathodic chamber under an applied cathode potential of -0.7 V vs standard hydrogen electrode (SHE). The rate of production of acetate, isobutyrate, propionate and 2-piperidinone from reduction of CO2 in the cathodic chamber of the MES was 0.81 mM/day, 0.63 mM/day, 0.44 mM/day and 0.53 mM/day, respectively. As methane was also present in the biogas, methyl derivatives of these acids were also found in traces in catholyte. It was observed that the use of nickel foam as an anode, 1 M NiSO4 solution as anolyte, graphite felt as a cathode, phosphate buffer solution as catholyte at a pH of 5.2 proved to be the best possible combination for MES for this study to get enhanced product yield at higher energy efficiency. [ABSTRACT FROM AUTHOR]

An appropriate current collector (CC) is crucial for harvesting substantial power in a microbial fuel cell (MFC). In the present study, stainless steel (SS) and titanium wires were used as the CCs for both the anode and cathode of MFC-1 and MFC-2, respectively. Tungsten wire (TW) was used as the anode CC in MFC-3, with SS wire as the cathode CC. In MFC-4, TW was used as the cathode CC with SS wire as the anode CC, and in MFC-5 both electrode CCs were TW. The power density, current density, oxidation current and bio-capacitance were compared to select the best and most cost effective CC material to enhance the power output of MFCs. Maximum power densities (mW/m²) of 32.28, 93.10, 225.38, 210.74, and 234.88 were obtained inMFC-1,MFC-2,MFC-3,MFC-4, and MFC-5, respectively. The highest current density (639.86mA/m²) and coulombic efficiency (23.12±1.5%) achieved in MFC-5 showed TW to be the best CC for both electrodes. Themaximum oxidation current of 7.4 mA and 7 mA and bio-capacitance of 10.3 mF/cm² and 9.7 mF/cm² were achieved in MFC-3 and MFC-5, respectively, suggesting TW is the best as the anode CC and SS wire as the cathode CC to reduce MFC fabrication costs. [ABSTRACT FROM AUTHOR]

A hybrid upflow anaerobic sludge blanket (UASB)–moving bed biofilm (MBB) and rope bed biofilm (RBB) reactor was designed for treatment of sewage. Possibility of enhancing granulation in an UASB reactor using moving media to improve sludge retention was explored while treating low-strength wastewater. The presence of moving media in the top portion of the UASB reactor allowed a high solid retention time even at very short hydraulic retention times and helped in maintaining selection pressure in the sludge bed to promote formation of different sized sludge granules with an average settling velocity of 67 m/h. These granules were also found to contain plenty of extracellular polymeric substance (EPS) such as 58 mg of polysaccharides (PS) per gram of volatile suspended solids (VSS) and protein (PN) content of 37 mg/g VSS. Enriched sludge of nitrogen-removing bacteria forming a porous biofilm on the media in RBB was also observed in a concentration of around 894 g/m2. The nitrogen removing sludge also had a high EPS content of around 22 mg PS/g VSS and 28 mg PN/g VSS. This hybrid UASB-MBB-RBB reactor with enhanced anaerobic granular sludge treating both carbonaceous and nitrogenous matter may be a sustainable solution for decentralized sewage treatment. [ABSTRACT FROM PUBLISHER]

Sediment microbial fuel cells (SMFCs) are bio-electrochemical devices generating electricity from redox gradients occurring across the sediment–water interface. Sediment microbial carbon-capture cell (SMCC), a modified SMFC, uses algae grown in the overlying water of sediment and is considered as a promising system for power generation along with algal cultivation. In this study, the performance of SMCC and SMFC was evaluated in terms of power generation, dissolved oxygen variations, sediment organic matter removal and algal growth. SMCC gave a maximum power density of 22.19 mW/m2, which was 3.65 times higher than the SMFC operated under similar conditions. Sediment organic matter removal efficiencies of 77.6 ± 2.1% and 61.0 ± 1.3% were obtained in SMCC and SMFC, respectively. With presence of algae at the cathode, a maximum chemical oxygen demand and total nitrogen removal efficiencies of 63.3 ± 2.3% (8th day) and 81.6 ± 1.2% (10th day), respectively, were observed. The system appears to be favorable from a resources utilization perspective as it does not depend on external aeration or membranes and utilizes algae and organic matter present in sediment for power generation. Thus, SMCC has proven its applicability for installation in an existing oxidation pond for sediment remediation, algae growth, carbon conversion and power generation, simultaneously. [ABSTRACT FROM AUTHOR]

A pilot-scale upflow anaerobic sludge blanket-moving bed biofilm (UASB-MBB) reactor followed by a high-rate algal pond (HRAP) was designed and operated to remove organic matter, nutrients and pathogens from sewage and to facilitate reuse. For an influent chemical oxygen demand (COD) concentration of 233±20 mg/L, final effluent COD was 50± 6 mg/L. Successful biomass granulation was observed in the sludge bed of the upflow anaerobic sludge blanket (UASB) reactor after 5 months of operation. Ammonia removal in HRAP was 85.1± 2.4% with average influent and effluent ammonia nitrogen concentrations of 20± 3 mg/L and 3 ±1 mg/L, respectively. Phosphate removal after treatment in the HRAP was 91±1%. There was a 2-3 log scale pathogen removal after treatment in HRAP with most probable number (MPN) of the final effluent being 600-800 per 100 mL, which is within acceptable standards for surface irrigation. The blackwater after treatment in UASBMBBR-HRAP is being reused for gardening and landscaping. This proper hydro-dynamically designed UASB reactor demonstrated successful granulation and moving bed media improved sludge retention in UASB reactor. This combination of UASB-MBB reactor followed by HRAP demonstrated successful sewage treatment for a year covering all seasons. [ABSTRACT FROM AUTHOR]

The effect of influent chemical oxygen demand (COD), hydraulic retention time (HRT), and influent pH on COD removal efficiency and power generation was studied in a dual-chambered microbial fuel cell (MFC) having stainless-steel mesh electrodes and treating synthetic wastewater. Statistical models were formulated based on these three variables to predict the responses, namely COD removal efficiency and power generation, in MFC using a two-level full factorial design. It was observed from statistical analyses that all the three variables affected the COD removal efficiency, whereas proper combination of the operating variables was of utmost importance in enhancing power generation. Average influent COD concentration of 2200-2400 mg/L and HRT of 22-25 h was found to be optimum for achieving optimal COD removal efficiency and power. Validation of the model's predictions for treatment of synthetic wastewater revealed the efficacy of these models. Under optimal conditions when these MFCs were operated with a graphite plate cathode and using aerated distilled water and persulfate as cathodic electrolyte, respective volumetric power densities of 979 and 7,408 mW/m3 were observed. [ABSTRACT FROM AUTHOR]

Contamination of water and sediment in water bodies is caused by the runoff from agriculture fields, and release of untreated/ partially treated domestic and industrial wastewaters. Polluted water can affect the health of humans and aquatic organisms, and nutrient discharge can lead to algal blooms. A sustainable solution is required to treat these pollutants to protect future populations from environmental hazards. Sediment microbial fuel cells (SMFCs) is a new technology that has the potential to remediate sediment and water from sluggish water bodies and ponds, and generate some electricity as a byproduct. This critical review discusses types of SMFCs, factors affecting performance of the SMFCs, its capability to offer in situ treatment of sediment and wastewater, and challenges to overcome to make this technology efficient for remediating water quality and harvesting electricity. [ABSTRACT FROM AUTHOR]

An electrochemically active bacteria Pseudomonas aeruginosa IIT BT SS1 was isolated from a dark fermentative spent media fed anode, and a bioaugmentation technique using the isolated strain was used to improve the start-up time of a microbial fuel cell (MFC). Higher volumetric current density and lower start-up time were observed with the augmented system MFC-PM (13.7 A/m³) when compared with mixed culture MFC-M (8.72 A/m³) during the initial phase. This enhanced performance in MFC-PM was possibly due to the improvement in electron transfer ability by the augmented strain. However, pure culture MFC-P showed maximum volumetric current density (17 A/m³) due to the inherent electrogenic properties of Pseudomonas sp. An electrochemical impedance spectroscopic (EIS) study, along with matrix-assisted laser desorption/ionization-time-offlight (MALDI-TOF) analysis, supported the influence of isolated species in improving the MFC performance. The present study indicates that the bioaugmentation strategy using the isolated Pseudomonas sp. can be effectively utilized to decrease the start-up time of MFC. [ABSTRACT FROM AUTHOR]

A five-chamber microbial desalination cell (MDC) with anode, cathode, one central desalination chamber and two concentrate chambers separated by ion exchange membranes was operated in batch mode for more than 60 days. The performance of the MDC was evaluated for chemical oxygen demand (COD) removal, total dissolved solids (TDS) removal and energy production. An average COD removal of 81±2.1% was obtained using acetate-fed wastewater as substrate in the anodic chamber inoculated with mixed anaerobic sludge. TDS removals of 58, 70 and 78% were observed with salt concentration of 8, 20 and 30 g/L, respectively, in the middle desalination chamber. The MDC produced a maximum power output of 16.87 mW/m2 during polarization. The highest Coulombic efficiency of 12± 2.4% was observed in this system using mixed anaerobic sludge as inoculum. The system effectively demonstrated capability for simultaneous organic matter removal and desalination along with power generation. [ABSTRACT FROM AUTHOR]