Comparison of Di-n-methyl Phthalate Biodegradation by Free and Immobilized Microbial Cells

To compare the biodegradation of di-n-methyl pathalate by free and immobilized microbial cells. Methods The enrichment and isolation technique was used to isolate the microorganism. The PAV-entrapment method was utilized to immobilize the microorganisms. The scanning electron microscophy (SEM) was used to observe the growth and distribution of microbial cells immobilized inside the PVA bead gels. The GC/MS method was used to identify the main intermediates of DMP degradation. Results The microbial cells could grow quite well in PVA gel. The metabolic pathway did not change before and after immobilization of the microbial cells. The degradation rate of immobilized cells was higher than that of free cells. Conclusion The immobilized microbial cells possess advantages than free cells when applied to the biodegradation of toxic organic pollutants.

Tailoring Iron-Ion Release of Cellulose-Based Aerogel-Coated Iron Foam for Long-Term High-Power Microbial Fuel Cells

The presence of iron(Fe) has been found to favor power generation in microbial fuel cells(MFCs). To achieve long-term power production in MFCs, it is crucial to effectively tailor the release of Fe ions over extended operating periods. In this study, we developed a composite anode(A/IF) by coating iron foam with cellulose-based aerogel. The concentration of Fe ions in the anode solution of A/IF anode reaches 0.280 μg/mL(Fe^(2+) vs. Fe^(3+) = 61%:39%) after 720 h of aseptic primary cell operation. This value was significantly higher than that(0.198 μg/mL, Fe^(2+) vs. Fe^(3+) = 92%:8%) on uncoated iron foam(IF), indicating a continuous release of Fe ions over long-term operation. Notably, the resulting MFCs hybrid cell exhibited a 23% reduction in Fe ion concentration(compared to a 47% reduction for the IF anode) during the sixth testing cycle(600-720 h). It achieved a high-power density of 301 ± 55 mW/m^(2) at 720 h, which was 2.62 times higher than that of the IF anode during the same period. Furthermore, a sedimentary microbial fuel cell(SMFCs) was constructed in a marine environment, and the A/IF anode demonstrated a power density of 103 ± 3 mW/m^(2) at 3240 h, representing a 75% improvement over the IF anode. These findings elucidate the significant enhancement in long-term power production performance of MFCs achieved through effective tailoring of Fe ions release during operation.

Hydrogen production performance of the non⁃platinum⁃based MoS_(2)/CuS cathode in microbial electrolytic cells

MoS_(2)/CuS composite catalysts were successfully synthesized using a one-step hydrothermal method with sodium molybdate dihydrate,thiourea,oxalic acid,and copper nitrate trihydrate as raw materials.The hydrogen pro-duction performance of MoS_(2)/CuS prepared with different molar ratios of Mo to Cu precursors(n_(Mo)∶n_(Cu))as cathodic catalysts was investigated in the two-chamber microbial electrolytic cell(MEC).X-ray diffraction(XRD),X-ray pho-toelectron spectroscopy(XPS),scanning electron microscopy(SEM),transmission electron microscope(TEM),linear scanning voltammetry(LSV),electrochemical impedance analysis(EIS),and cyclic voltammetry(CV)were used to characterize the synthesized catalysts for testing and analyzing the hydrogen-producing performance.The results showed that the hydrogen evolution performance of MoS_(2)/CuS-20%(nMo∶nCu=5∶1)was better than that of platinum(Pt)mesh,and the hydrogen production rate of MoS_(2)/CuS-20%as a cathode in MEC was(0.2031±0.0237)m^(3)_(H_(2))·m^(-3)·d^(-1) for 72 h at an applied voltage of 0.8 V,which was slightly higher than that of Pt mesh of(0.1886±0.0134)m^(3)_(H_(2))·m^(-3)·d^(-1).The addition of a certain amount of CuS not only regulates the electron transfer ability of MoS_(2) but also increases the density of active sites.

The growth of biopolymers and natural earthen sources as membrane/separator materials for microbial fuel cells:A comprehensive review

Microbial fuel cell(MFC)technology has emerged as an effective solution for energy insecurity and bioremediation.However,identifying suitable components(particularly separators or membranes)with the required properties,such as low cost and high performance,remains challenging and restricts practical application.Commercial membranes,such as Nafion,exhibit excellent performance in MFC.However,these membranes have high production costs,which considerably increase the overall MFC unit cell cost.Among the numerous types,the separators or membranes developed from biopolymers and naturally occurring earthen sources have proven to be a novel and efficient concept due to their natural abundance,cost-effectiveness(approximately$20 m^(-2),$5 m^(-2),and$1 kg-1for biopolymers,ceramics,and earthensources,respectively),structural properties,proton transportation,manufacturing and modification ease,and environmental friendliness.In this review,we emphasize cost-effective renewable green materials(biopolymers,bio-derived materials,and naturally occurring soil,clay,ceramics or minerals)for MFC applications for the first time.Biopolymers with good thermal,mechanical,and water retention properties,sustainability,and environmental friendliness,such as cellulose and chitosan,are typically preferred.Furthermore,the modification or introduction of various functional groups in biopolymers to enhance their functional properties and scale MFC power density is explored.Subsequently,separator/membrane development using various bio-sources(such as coconut shells,banana peels,chicken feathers,and tea waste ash)is described.Additionally,naturally occurring sources such as clay,montmorillonite,and soils(including red,black,rice-husk,and Kalporgan soil)for MFC were reviewed.In conclusion,the existing gap in MFC technology was filled by providing recommendations for future aspects based on the barriers in cost,environment,and characteristics.

The biofilm characteristics and enhanced performance of a marine microbial-electrolysis-cell-based biosensor under positive anodic potential

Microbial fuel cells have already been used as biosensors to monitor assimilable organic carbon(AOC).However,their signal production from AOC is known to be completely suppressed by dissoved oxygen(DO).In this study,two identical microbial electrolysis cell(MEC)based biosensors were inoculated with marine sediment and operated at two different anodic potentials,namely-300 mV and+250 mV relative to Ag/AgCl.The MEC biosensor operated under positive anodic potential conditions had electrochemically active microbial communities on the anode,including members of the Shewanellaceae,Pseudoalteromonadaceae,and Clostridiaceae families.However,the strictly anaerobic members of the Desulfuromonadaceae,Desulfobulbaceae and Desulfobacteraceae families were found only in the negative anodic potential MEC biosensor.The positive anodic potential MEC biosensor showed several other advantages as well,such as faster start-up,significantly higher maximum current production,fivefold improvement in the AOC detection limit,and tolerance of low dissolved oxygen,compared to those obtained from the negative anodic potential MEC biosensor.The developed positive anodic potential MEC biosensor can thus be used as a real-time and inexpensive detector of AOC concentrations in high saline and low DO seawater.

Magnetically modified microbial cells:A new type of magnetic adsorbents

Microbial cells, either in free or immobilized form, can be used for the preconcentration or removal of metal ions, organic and inorganic xenobiotics or biologically active compounds. Magnetic modification of these cells enables to prepare magnetic adsorbents that can be easily manipulated in difficult-to-handle samples, such as suspensions, in the presence of external magnetic field. In this review, typical examples of magnetic modifications of microbial cells are presented, as well as their possible applications for the separation of organic xenobiotics and heavy metal ions.

Melamine modified carbon felts anode with enhanced electrogenesis capacity toward microbial fuel cells

Surface electropositivity and low internal resistance are important factors to improve the anode performance in microbial fuel cells (MFCs). Nitrogen doping is an effective way for the modification of traditional carbon materials. In this work, heat treatment and melamine were used to modify carbon felts to enhance electrogenesis capacity of MFCs. The modified carbon felts were characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscopy (AFM) and malvern zeta potentiometer. Results show that the maximum power densities under heat treatment increase from 276.1 to 423.4 mW/m(2) (700 degrees C) and 461.5 mW/m(2) (1200 degrees C) and further increase to 472.5 mW/m(2) (700 degrees C) and 515.4 mW/m(2) (1200 degrees C) with the co-carbonization modification of melamine. The heat treatment reduces the material resistivity, improves the zeta potential which is beneficial to microbial adsorption and electron transfer. The addition of melamine leads to the higher content of surface pyridinic and quaternary nitrogen and higher zeta potential. It is related to higher MFCs performance. Generally, the melamine modification at high temperature increases the feasibility of carbon felt as MFCs's anode materials. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Sustainable biochar as an electrocatalysts for the oxygen reduction reaction in microbial fuel cells

Microbial fuel cells(MFCs)have gained remarkable attention as a novel wastewater treatment that simultaneously generates electricity.The low activity of the oxygen reduction reaction(ORR)remains one of the most critical bottlenecks limiting the development of MFCs.To date,although research on biochar as an electrocatalyst in MFCs has made tremendous progress,further improvements are needed to make it economically practical.Recently,biochars have been considered to be ORR electrocatalysts with developmental potential.In this review,the ORR mechanism and the essential requirements of ORR catalysts in MFC applications are introduced.Moreover,the focus is to highlight the material selection,properties,and preparation of biochar electrocatalysts,as well as the evaluation and measurement of biochar electrodes.Additionally,in order to provide comprehensive information on the specific applications of biochars in the field of MFCs,their applications as electrocatalysts,are then discussed in detail,including the uses of nitrogen-doped biochar and other heteroatom-doped biochars as electrocatalysts,poisoning tests for biochar catalysts,and the cost estimation of biochar catalysts.Finally,profound insights into the current challenges and clear directions for future perspectives and research are concluded.

Nitrogen and Sulfur Co-doped Porous Carbon Derived from ZIF-8 as Oxygen Reduction Reaction Catalyst for Microbial Fuel Cells

Nitrogen and sulfur co-doped porous nanocarbon (ZIF-C-N-S) catalyst was successfully synthesized derived from ZIF-8 and thiourea precursors.The electrochemical measurements indicate that the as-obtained ZIF-C-N-S catalyst exhibits higher electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline electrolyte and superior durability-longer than commercial Pt/C catalyst.The enhancment of electrocatalytic activity mainly be come from the open pore structure,large specific surface area as well as the synergistic effect resulted from the co-doping of N and S atoms.In addition,the ZIF-C-N-S catalyst is also used as the air cathode catalyst in the microbial fuel cell (MFC) device.The maximum power density and stable output voltage of ZIF-C-N-S based MFC are 1315 mW/m2 and 0.48 V,respectively,which is better than that of Pt/C based MFC.

Comparative Study of Two Carbon Fiber Cathodes and Theoretical Analysis in Microbial Fuel Cells on Ocean Floor

Cathode activity plays an important role in the improvement of the microbial fuel cells on ocean floor （BMFCs）. A comparison study between Rayon-based （CF-R） and PAN-based carbon fiber （CF-P） cathodes is conducted in the paper. The two carbon fibers were heat treated to improve cell performance （CF-R-H ＆ CF-P-H）, and were used to build a new BMFCs structure with a foamy carbon anode. The maximum power density was 112.4mWm-2 for CF-R-H, followed by 66.6mWm-2 for CF-R, 49.7 mWm-2 for CF-P-H and 21.6mWm-2 for CF-P respectively. The higher specific area and deep groove make CF-R have a better power output than with CF-P. Meanwhile, heat treatment of carbon fiber can improve cell power, nearly two-fold higher than heat treatment of plain fiber. This improvement may be due to the quinones group formation to accelerate the reduction of oxygen and electron transfer on the fiber surface in the three phase boundary after heat treatment. Compared to PAN-based carbon fiber, Rayon-based carbon fiber would be preferentially selected as cathode in novel BMFCs design due to its high surface area, low cost and higher power. The comparison research is significant for cathode material selection and cell design.

Carbon material-based anodes in the microbial fuel cells

For the performance improvement of microbial fuel cells(MFCs),the anode becomes a breakthrough point due to its influence on bacterial attachment and extracellular electron transfer(EET).On other level,carbon materials possess the following features:low cost,rich natural abundance,good thermal and chemical stability,as well as tunable surface properties and spatial structure.Therefore,the development of carbon materials and carbon-based composites has flourished in the anode of MFCs during the past years.In this review,the major carbon materials used to decorate MFC anodes have been systematically summarized,based on the differences in composition and structure.Moreover,we have also outlined the carbon material-based hybrid biofilms and carbon material-modified exoelectrogens in MFCs,along with the discussion of known strategies and mechanisms to enhance the bacteria-hosting capabilities of carbon material-based anodes,EET efficiencies,and MFC performances.Finally,the main challenges coupled with some exploratory proposals are also expounded for providing some guidance on the future development of carbon material-based anodes in MFCs.

Microbial Electrolysis Cells for Hydrogen Production

Microbial electrolysis cells(MECs)present an attractive route for energy-saving hydrogen(H2)production along with treatment of various wastewaters,which can convert organic matter into H2 with the assistance of microbial electrocatalysis.However,the development of such renewable technologies for H2 production still faces considerable challenges regarding how to enhance the H2 production rate and to lower the energy and the system cost.In this review,we will focus on the recent research progress of MEC for H2 production.First,we present a brief introduction of MEC technology and the operating mechanism for H2 production.Then,the electrode materials including some typical electrocatalysts for hydrogen production are summarized and discussed.We also highlight how various substrates used in MEC affect the associated performance of hydrogen generation.Finally we presents several key scientific challenges and our perspectives on how to enhance the electrochemical performance.

Characterization of Fe/N-doped graphene as air-cathode catalyst in microbial fuel cells

This work proposed a simple and efficient approach for synthesis of durable and efficient non-precious metal oxygen reduction reaction（ORR） electro-catalysts in MFCs. The rod-like carbon nanotubes（CNTs）were formed on the Fe–N/SLG sheets after a carbonization process. The maximum power density of1210 ± 23 m W·mobtained with Fe–N/SLG catalyst in an MFC was 10.7% higher than that of Pt/C catalyst(1080 ± 20 mW ·m) under the same condition. The results of RDE test show that the ORR electron transfer number of Fe–N/SLG was 3.91 ± 0.02, which suggested that ORR catalysis proceeds through a four-electron pathway. The whole time of the synthesis of electro-catalysts is about 10 h, making the research take a solid step in the MFC expansion due to its low-cost, high efficiency and favorable electrochemical performance. Besides, we compared the electrochemical properties of catalysts using SLG, high conductivity graphene（HCG, a kind of multilayer graphene） and high activity graphene（HAG, a kind of GO） under the same conditions, providing a solution for optimal selection of cathode catalyst in MFCs.The morphology, crystalline structure, elemental composition and ORR activity of these three kinds of Fe–N/C catalysts were characterized. Their ORR activities were compared with commercial Pt/C catalyst.It demonstrates that this kind of Fe–N/SLG can be a type of promising highly efficient catalyst and could enhance ORR performance of MFCs.

Power production enhancement with polyaniline composite anode in benthic microbial fuel cells

In this study,conductive polymer polyaniline(PANI)is employed to modify the anodes of benthic microbial fuel cells(BMFC).Four electrochemical methods are used to synthesize the polyaniline anodes;the results show that the PANI modification,especially the pulse potential method for PANI synthesis could obviously improve the cell energy output and reduce the anode internal resistance.The anode is modified by PANI doped with Fe or Mn to further improve the BMFC performance.A maximum power density of 17.51 mW/m2 is obtained by PANI-Fe anode BMFC,which is 8.1 times higher than that of control.The PANI-Mn anode BMFC also gives a favorable maximum power density(16.78 mW/m2).Fe or Mn modification has better effect in improving the conductivity of polyaniline,thus improving the energy output of BMFCs.This work applying PANI composite anode into BMFC brings new development prospect and could promote the practical application of BMFC.

A Comprehensive Review on Oxygen Reduction Reaction in Microbial Fuel Cells

The focus of microbial fuel cell research in recent years has been on the development of materials,microbes,and transfer of charges in the system,resulting in a substantial improvement in current density and improved power generation.The cathode is generally recognized as the limiting factor due to its high-distance proton transfer,slow oxygen reduction reaction(ORR),and expensive materials.The heterogeneous reaction determines power gen-eration in MFC.This comprehensive review describes-recent advancements in the development of cathode mate-rials and catalysts associated with ORR.The recent studies indicated the utilization of different metal oxides,the ferrite-based catalyst to overcome this bottleneck.These studies conclude that some cathode materials,in parti-cular,graphene-based conductive polymer composites with non-precious metal catalysts provide substantial ben-efits for sustainable development in the field of MFCs.Furthermore,it also highlights the potentiality to replace the conventional platinum air cathode for the large-scale production of the next generation of MFCs.It was evi-dent from the experiments that cathode catalyst needs to be blended with conductive carbon materials to make cathode conductive and efficient for ORR.This review discusses various antifouling strategies for cathode biofoul-ing and its effect on the MFC performance.Moreover,it also depicts cost estimations of various catalysts essential for further scale-up of MFC technology.

Utilization of Nanomaterials as Anode Modifiers for Improving Microbial Fuel Cells Performance

Microbial fuel cells(MFCs)are an attractive innovation at the nexus of energy and water security for the future.MFC utilizes electrochemically active microorganisms to oxidize biodegradable substrates and generate bioelectricity in a single step.The material of the anode plays a vital role in increasing the MFC’s power output.The anode in MFC can be upgraded using nanomaterials providing benefits of exceptional physicochemical properties.The nanomaterials in anode gives a high surface area,improved electron transfer promotes electroactive biofilm.Enhanced power output in terms of Direct current(DC)can be obtained as the consequence of improved microbe-electrode interaction.However,several limitations like complex synthesis and degeneration of property do exist in the development of nanomaterial-based anode.The present review discusses different renewable nanomaterial applied in the anode to recover bioelectricity in MFC.Carbon nanomaterials have emerged in the past decade as promising materials for anode construction.Composite materials have also demonstrated the capacity to become potential anode materials of choice.Application of a few transition metal oxides have been explored for efficient extracellular electron transport(EET)from microbes to the anode.

Electrochemical Properties of Electrodes with Different Shapes and Diffusion Kinetic Analysis of Microbial Fuel Cells on Ocean Floor

Microbial fuel cell(MFC) on the ocean floor is a kind of novel energy-harvesting device that can be developed to drive small instruments to work continuously.The shape of electrode has a great effect on the performance of the MFC.In this paper,several shapes of electrode and cell structure were designed,and their performance in MFC were compared in pairs:Mesh(cell-1) vs.flat plate(cell-2),branch(cell-3) vs.cylinder(cell-4),and forest(cell-5) vs.disk(cell-6) FC.Our results showed that the maximum power densities were 16.50,14.20,19.30,15.00,14.64,and 9.95 mWm-2 for cell-1,2,3,4,5 and 6 respectively.And the corre-sponding diffusion-limited currents were 7.16,2.80,18.86,10.50,18.00,and 6.900 mA.The mesh and branch anodes showed higher power densities and much higher diffusion-limited currents than the flat plate and the cylinder anodes respectively due to the low diffusion hindrance with the former anodes.The forest cathode improved by 47% of the power density and by 161% of diffusion-limited current than the disk cathode due to the former's extended solid/liquid/gas three-phase boundary.These results indicated that the shape of electrode is a major parameter that determining the diffusion-limited current of an MFC,and the differences in the elec-trode shape lead to the differences in cell performance.These results would be useful for MFC structure design in practical applica-tions.

Multi-objective steady-state optimization of two-chamber microbial fuel cells

A microbial fuel cell(MFC)is a novel promising technology for simultaneous renewable electricity generation and wastewater treatment.Three non-comparable objectives,i.e.power density,attainable current density and waste removal ratio,are often conflicting.A thorough understanding of the relationship among these three conflicting objectives can be greatly helpful to assist in optimal operation of MFC system.In this study,a multiobjective genetic algorithm is used to simultaneously maximizing power density,attainable current density and waste removal ratio based on a mathematical model for an acetate two-chamber MFC.Moreover,the level diagrams method is utilized to aid in graphical visualization of Pareto front and decision making.Three biobjective optimization problems and one three-objective optimization problem are thoroughly investigated.The obtained Pareto fronts illustrate the complex relationships among these three objectives,which is helpful for final decision support.Therefore,the integrated methodology of a multi-objective genetic algorithm and a graphical visualization technique provides a promising tool for the optimal operation of MFCs by simultaneously considering multiple conflicting objectives.

Scalability of biomass-derived graphene derivative materials as viable anode electrode for a commercialized microbial fuel cell: A systematic review

Microbial fuel cell(MFC) is an advanced bioelectrochemical technique that can utilize biomass materials in the process of simultaneously generating electricity and biodegrading or bio transforming toxic pollutants from wastewater. The overall performance of the system is largely dependent on the efficiency of the anode electrode to enhance electron transportation. Furthermore, the anode electrode has a significant impact on the overall cost of MFC setup. Hence, the need to explore research focused towards developing cost-effective material as anode in MFC. This material must also have favourable properties for electron transportation. Graphene oxide(GO) derivatives and its modification with nanomaterials have been identified as a viable anode material. Herein, we discussed an economically effective strategy for the synthesis of graphene derivatives from waste biomass materials and its subsequent fabrication into anode electrode for MFC applications. This review article offers a promising approach towards replacing commercial graphene materials with biomass-derived graphene derivatives in a view to achieve a sustainable and commercialized MFC.

Bimetallic catalysts as electrocatalytic cathode materials for the oxygen reduction reaction in microbial fuel cell:A review

Microbial fuel cell(MFC) is one synchronous power generation device for wastewater treatment that takes into account environmental and energy issues, exhibiting promising potential. Sluggish oxygen reduction reaction(ORR) kinetics on the cathode remains by far the most critical bottleneck hindering the practical application of MFC. An ideal cathode catalyst should possess excellent ORR activity, stability, and costeffectiveness, experiments have demonstrated that bimetallic catalysts are one of the most promising ORR catalysts currently. Based on this, this review mainly analyzes the reaction mechanism(ORR mechanisms, synergistic effects), advantages(combined with characterization technologies), and typical synthesis methods of bimetallic catalysts, focusing on the application effects of early Pt-M(M = Fe, Co, and Ni) alloys to bifunctional catalysts in MFC, pointing out that the main existing challenges remain economic analysis, long-term durability and large-scale application, and looking forward to this. At last, the research trend of bimetallic catalysts suitable for MFC is evaluated, and it is considered that the development and research of metal-organic framework(MOF)-based bimetallic catalysts are still worth focusing on in the future, intending to provide a reference for MFC to achieve energy-efficient wastewater treatment.