Electroactive Membrane Research Articles

Electroanalytical detection of fruit ethylene by a novel electroactive biosensing membrane

Purpose This study aims to present an innovative approach to detect and monitor ethylene gas during fruit ripening. Design/methodology/approach It uses a specialized composite membrane in conjunction with a solid-state electrochemical method. This unique electroactive membrane, composed of polyvinyl alcohol (PVA), chitosan (CHT), lithium chloride (LiCl) and ammonium molybdate (AMO), exhibits synergistic behavior when applied to a microelectrode chip surface. This composite enhances the sensitivity of electrochemical ethylene detection. Empirical experiments were conducted to elucidate the ripening kinetics in various fruit specimens, including apples, pears and mangoes. These fruits released ethylene, which was analyzed using the molybdenum-permeated electroactive biopolymer composite membrane, a critical determinant of ethylene levels. Findings Characterization of the synthesized composite through techniques such as X-ray diffraction and Fourier-transform infrared spectroscopy revealed reduced crystallinity and decreased hydrogen bond interactions upon activation with Mo ions. Field emission scanning electron microscopy images exhibited a distinctive porous surface morphology with spherical microgranules. Energy dispersive X-ray analysis indicated a significant change in the mass or atomic composition of Mo in the composite membrane after Mo ion activation. Electrochemical measurements, including cyclic voltammetry and potentiostatic electrochemical impedance spectroscopy, validated the efficiency of the Mo-activated PVA-CHT-LiCl-AMO membrane, manifesting an impressive 87.79% increase in sensitivity compared to the nonactivated membrane. Practical implications This research work represents a significant advancement in the field of ethylene detection and fruit ripening monitoring. The Mo-activated PVA-CHT-LiCl-AMO membrane offers a reliable and effective solution for real-time ethylene detection, providing an invaluable tool for the horticultural industry to optimize fruit ripening processes, extend shelf life and ensure the delivery of high-quality produce to consumers. Social implications The findings of this study hold great promise for fostering sustainability and efficiency within the global fruit supply chain, ultimately benefiting both producers and consumers alike. Originality/value The implications of this research extend to the fabrication of a sensor based on a solid-state electroactive PVA-CHT-LiCl-AMO composite membrane, which upon Mo-activation exhibits robust electrochemical fruit ethylene detection when exposed to different fruits.

(Invited) Electrochemical Processes Drive Membrane-Based Recovery of N and P

We expend a large amount of energy and money on the treatment of municipal and industrial wastewater, relying on redox reactions to transform contaminants (e.g, ammonium, reduced carbon) into other less/non-harmful species (N2/NO3 -, CO2), or on biological accumulation approaches that sequester contaminants into bacteria (e.g., biomass, PO4 -3). In the worst case, these contaminants are simply released into the environment where they cause harm and are lost. Yet, many of these contaminants are actually valuable resources (e.g., NH3, PO4 -3). In an age where environmental sustainability and climate change mitigation are of utmost importance, it makes little sense to invest large amounts of energy into the conversion and elimination of these valuable resources, only to turn around and use fossil fuels to produce more. In addition, the value of these resources is often higher than the value of the treated water, making their recovery an economically-attractive prospect.Here, we discuss our recent work on membrane-based separations of ammonia, phosphate, and volatile fatty acids (VFAs) from different waste streams. Critically, in all cases we achieve separation by leveraging electrochemical reactions and processes. For ammonia recovery, we utilize an electroactive membrane contactor that is used as a cathode – the application of cathodic potentials to the membrane surface increases the local pH at the membrane/water interface, which transforms ammonium to ammonia and enables its effective volatilization and recovery across the membrane. For VFA recovery, we use a composite electroactive membrane that combines electrothermal heating and an electrochemical pH swing to protonate and extract these volatile species from water. Finally, for phosphate separation, we engineer a phosphate-specific pathway through a cation exchange membrane, and use electrodialysis to pull phosphate ions from a mixed anion solution. Together, these approaches can be used to recover valuable products from complex waste streams, such as municipal and industrial wastewater, without the need to rely on bulk pH and temperature modification.

Cobalt-substituted porous calcium copper titanate electrodes for paracetamol degradation by an electro-oxidation/peroxymonosulfate system

Developing cobalt-substituted perovskite electroactive membranes with an efficient Co/Cu combination mode is an important environmental challenge for removing drugs via peroxymonosulfate (PMS) activation. In this work, cobalt (Co)-substituted calcium copper titanatewas synthesized with an easy ball milling process and used as an anode in electro-oxidation in the presence of PMS for paracetamol degradation. The Co-CCTO anode with a Co ratio of 0.5 showed the highest removal efficiency (100 % of 10 ppm paracetamol after 180 min) due to the increase of the active sites and the appearance of the Co2+/Co3+ cycle that accelerates the charge transfer with Co incorporation into the lattice. Scavenger experiments showed that sulfate radicals (SO4̇−), oxygen radicals (O2̇-), hydroxyl radicals (̇OH), and singlet oxygen (1O2) were generated in the electro-oxidation-PMS reaction system and that SO4̇−, 1O2, and O2̇- were the dominant active radicals. The toxicity tests with Vibrio fischeri confirmed paracetamol mineralization and decomposition and the elimination of harmful by-products. It is crucial to explore the substitution of CCTO with different metal dopants in order to optimize the membrane performance and overcome the limitations associated with cobalt substitution.

Wettability of an electroactive membrane in surfactant-containing brine for conductive heating membrane distillation

Membrane distillation (MD) is a technology that has proven to be highly efficient in desalination. However, the occurrence of membrane wetting can lead to the failure of the process. Given this, we developed an electroactive membrane (RC-M) using carbon nanotubes and reduced graphene oxide. The wettability of RC-M was then examined after treatment with cationic or anionic surfactants in brines during the conductive heating membrane distillation process. Results indicated that the RC-M had an abundance of charged functional groups and multiple defects in the graphene structure. Using 0.3 mol/L NaCl and 30 mg/L sodium dodecylbenzenesulfonate (SDBS), the RC-M worked for 600 mins with 97.2 % rejection. While, in a feed with hexadecyltrimethylammonium bromide, rejection dropped to 93.6 % in 350 minutes. When a potential was applied to the RC-M, the SDBS displayed electrostatic repulsion when interacting with the membrane, thereby preventing its adsorption. Moreover, the interaction between the feed and the charged RC-M caused electrolysis, and the resultant bubbles helped reduce wetting. Additionally, the RC-M itself possessed a hydrophilic layer that aided in mitigating wetting. The findings of this research offer valuable understanding regarding the durability of MD membranes and techniques to postpone membrane wetting.

Boosting Upconversion Efficiency in Optically Inert Shelled Structures with Electroactive Membrane through Electron Donation.

This study innovatively addresses challenges in enhancing upconversion efficiency in lanthanide-based nanoparticles (UCNPs) by exploiting Shewanella oneidensis MR-1, a microorganism capable of extracellular electron transfer. Electroactive membranes, rich in c-type cytochromes, are extracted from bacteria and integrated into membrane-integrated liposomes (MILs), encapsulating core-shelled UCNPs with an optically inactive shell, forming UCNP@MIL constructs. The electroactive membrane, tailored to donate electrons through the inert shell, independently boosts upconversion emission under near-infrared excitation (980 or 1550nm), bypassing ligand-sensitized UCNPs. The optically inactive shell restricts energy migration, emphasizing electroactive membrane electron donation. Density functional theory calculations elucidate efficient electron transfer due to the electroactive membrane hemes' highest occupied molecular orbital being higher than the valence band maximum of the optically inactive shell, crucial for enhancing energy transfer to emitter ions. The introduction of a SiO2 insulator coating diminishes light enhancement, underscoring the importance of unimpeded electron transfer. Luminescence enhancement remains resilient to variations in emitter or sensitizing ions, highlighting the robustness of the electron transfer-induced phenomenon. However, altering the inert shell material diminishes enhancement, emphasizing the role of electron transfer. This methodology holds significant promise for diverse biological applications. UCNP@MIL offers an advantage in cellular uptake, which proves beneficial for cell imaging.

One electron oxidation-induced degradation of brominated flame retardants in electroactive membrane filtration system: Vital role of dichlorine radical-mediated process

Reactive chlorine species (RCS) are inevitably generated in electrochemical oxidation process for treating high-salinity industrial wastewater, thereby resulting in the competition with coexisting hydroxyl radicals (•OH) for oxidizing recalcitrant organic compounds. Due to the low redox potentials compared to •OH, the role of RCS has been often overlooked. In this work, we developed an electroactive membrane filtration (EMF) system that had a high removal efficiency (99.1 ± 0.5 %) for tetrabromobisphenol S (TBBPS) at low energy consumption (1.45 kWh m−3). Electron spin resonance spectroscopy and molecular probing tests indicated the predominance of Cl2•–, of which steady-state concentration (2.2 ×10−10 M) was extremely higher than those of ClO• (6.7 ×10−13 M), •OH (0.95 ×10−13 M), and Cl• (2.39 ×10–15 M). The density functional theory (DFT) and intermediate product analysis highlighted that Cl2•– radicals had a higher electrophilic attack efficacy than •OH radicals for inducing changes in the electron density of the carbon atoms around phenolic hydroxyl groups, thus leading to the generation of transition state intermediates and accelerating the degradation of TBBPS. Our work demonstrates the vital role of Cl2•– radicals for pollutant degradation, highlighting the potential of this technology for cost-effective removal of recalcitrant organic compounds from water and wastewater.

Integrated Electrochemical Treatment Process for Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), Hexavalent Chromium, and Ammonia Using Electroactive Membranes

Integrated Electrochemical Treatment Process for Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), Hexavalent Chromium, and Ammonia Using Electroactive Membranes

Dynamic membrane filtration accelerates electroactive biofilms in bioelectrochemical systems

Bioelectrochemical systems (BES) have emerged as a dual-function technology for treating wastewater and recovering energy. A vital element of BES is the rapid formation and maintenance of electroactive biofilms (EABs). Previous attempts to accelerate EAB formation and improve electroactivities focused on enhancing the bacterial adhesion process while neglecting the rate-limiting step of the bacterial transport process. Here, we introduce membrane filtration into BES, establishing a dynamic membrane filtration system that enhances overall performance. We observed that optimal membrane flux considerably reduced the startup time for EAB formation. Specifically, EABs established under a 25 L m−2 h−1 flux (EAB25 LMH) had a formation time of 43.8 ± 1.3 h, notably faster than the 51.4 ± 1.6 h in the static state (EAB0 LMH). Additionally, EAB25 LMH exhibited a significant increase in maximum current density, approximately 2.2 times higher than EAB0 LMH. Pearson correlation analysis indicated a positive relationship between current densities and biomass quantities and an inverse correlation with startup time. Microbial analysis revealed two critical findings: (i) variations in maximum current densities across different filtration conditions were associated with redox-active substances and biomass accumulation, and (ii) the incorporation of a filtration process in EAB formation enhanced the proportion of viable cells and encouraged a more diverse range of electroactive bacteria. Moreover, the novel electroactive membrane demonstrated sustained current production and effective solid-liquid separation during prolonged operation, indicating its potential as a viable alternative in membrane-based systems. This approach not only provides a new operational model for BES but also holds promise for expanding its application in future wastewater treatment solutions.

Optimizing electroactive membrane performance for microalgae harvesting: A response surface methodology study of membrane formulation and operating parameters for electro filtration

Developing electroactive membranes for filtration has gained importance owing to their effectiveness in mitigating the long-lasting issue of fouling faced with traditional membranes. Here, we developed thin electroactive metallic films on to stainless steel mesh (SSM) using electrodeposition method and evaluated their performance for microalgae harvesting via electro filtration. The effect of electrodeposition parameters on membrane formulation and operating parameters for electro filtration, both in continuous and intermittent modes, were evaluated and optimum values were obtained using response surface methodology (RSM). The optimal combination of electrodeposition parameters is 1000 μA/cm2 and 5 min for deposition current density and time, respectively. Whereas the electric field strength of 20 V/mm with an application time of 1 min is suggested to be the optimal combination of electro filtration parameters for maximized flux recovery and corresponding experimental rejection efficiency of more than 90%. Overall, this research contributes to a better understanding of the parameters governing electro-filtration and offers insights for improving the performance of membrane-based microalgae harvesting systems.

Effect of Electrode on the Dynamics of Electroactive Membrane

Abstract The dynamics of the electroactive membranes are being studied extensively due to their vast application at the current time. However, the effect of the mechanical behavior of the compliant electrode needs to be addressed. This article presents the nonlinear analysis of an electrically actuated membrane, considering the inertia of the electrode. The membrane is modeled as a hyperelastic material and is assumed to be incompressible, homogeneous, and isotropic. The proposed analysis is discussed in a generalized way for both the compression and suspension phases. Since the membrane is vulnerable to pull-in instability, the conditions to prevent electromechanical instability are defined. Further, an analytical relation is established for breakdown voltage and is validated with experimental data. The analytical solution of axial vibration is presented in the form of elliptic integrals and by the use of multiple scale method in a generalized way for both the phases. The resultant motions and their various physical aspects under suspension and compression phases for general initial conditions are described through graphical results to comprehend the proposed analysis. Also, parameter values are quantified analytically, for which the system executes reverse behavior in a given configuration.

Fabrication and development of novel micromachined parylene-based electroactive membranes with embedded microfluidic architectures

This work describes the design, fabrication, modeling, and testing of monolithic micromachined parylene-based electroactive membranes (µPEMs) with embedded microfluidic channels. The design and modeling employed analytical plate theory to determine the optimal membrane dimensions and structural shapes for various microsystem designs. The µPEMs were fabricated using a combination of surface and bulk micromachining techniques incorporating Parylene C as a biocompatible polymeric structural material combined with patterned electrodes for actuation. Experimental actuation of the electroactive membranes demonstrated reliability with minimal voltage shifts, and theoretical pull-in voltages closely matching experimental results. Different structural parameters of the µPEMs were also tested, such as varying the overall membrane thickness/structural rigidity and actuation chamber depth. Dynamic actuation of the membrane, including, the deflection and system response to various actuation frequencies, was observed and quantified via optical coherence tomography techniques. Microfluidic architectures were monolithically integrated with the membrane actuator and successfully perfused, with no signs of leakage. This compact microsystem has potential applications in microfluidics and Lab/System-On-a-Chip devices, for use in micromixers, particle manipulators, and applying strain to adherent cells cultured on top of the membrane.

Electroactive membrane fusion-liposome for increased electron transfer to enhance radiodynamic therapy.

Dynamic therapies have potential in cancer treatments but have limitations in efficiency and penetration depth. Here a membrane-integrated liposome (MIL) is created to coat titanium dioxide (TiO2) nanoparticles to enhance electron transfer and increase radical production under low-dose X-ray irradiation. The exoelectrogenic Shewanella oneidensis MR-1 microorganism presents an innate capability for extracellular electron transfer (EET). An EET-mimicking photocatalytic system is created by coating the TiO2 nanoparticles with the MIL, which significantly enhances superoxide anions generation under low-dose (1 Gy) X-ray activation. The c-type cytochromes-constructed electron channel in the membrane mimics electron transfer to surrounding oxygen. Moreover, the hole transport in the valence band is also observed for water oxidation to produce hydroxyl radicals. The TiO2@MIL system is demonstrated against orthotopic liver tumours in vivo.

Simple and Low-Cost Electroactive Membranes for Ammonia Recovery.

Ammonia is considered a contaminant to be removed from wastewater. However, ammonia is a valuable commodity chemical used as the primary feedstock for fertilizer manufacturing. Here we describe a simple and low-cost ammonia gas stripping membrane capable of recovering ammonia from wastewater. The material is composed of an electrically conducting porous carbon cloth coupled to a porous hydrophobic polypropylene support, that together form an electrically conductive membrane (ECM). When a cathodic potential is applied to the ECM surface, hydroxide ions are produced at the water-ECM interface, which transforms ammonium ions into higher-volatility ammonia that is stripped across the hydrophobic membrane material using an acid-stripping solution. The simple structure, low cost, and easy fabrication process make the ECM an attractive material for ammonia recovery from dilute aqueous streams, such as wastewater. When paired with an anode and immersed into a reactor containing synthetic wastewater (with an acid-stripping solution providing the driving force for ammonia transport), the ECM achieved an ammonia flux of 141.3 ± 14.0 g.cm-2.day-1 at a current density of 6.25 mA.cm-2 (69.2 ± 5.3 kg(NH3-N)/kWh). It was found that the ammonia flux was sensitive to the current density and acid circulation rate.

Electroactive membrane with the electroactive layer beneath the separation layer to eliminate the interference of humic acid in the oxidation of antibiotics

Removing harmful antibiotics is essential to reclaiming water from municipal secondary effluent. Electroactive membranes are effective in the removal of antibiotics but challenged by the abundant coexisting macromolecular organic pollutants in municipal secondary effluent. To eliminate the interference of macromolecular organic pollutants in the removal of antibiotics, we propose a novel electroactive membrane with a top polyacrylonitrile (PAN) ultrafiltration layer and a bottom electroactive layer composed of carbon nanotubes (CNTs) and polyaniline (PANi). When filtering the mixture of tetracycline (TC, a typical antibiotic) and humic acid (HA, a typical macromolecular organic pollutant), the PAN-CNT/PANi membrane performed sequential removal. It retained HA at the PAN layer (by ∼96%) and allowed TC to reach the electroactive layer where it was electrochemically oxidized (e.g., by ∼92% at 1.5 V). The TC removal of the PAN-CNT/PANi membrane was marginally affected by HA, unlike that of the control membrane with the electroactive layer on the top that showed decreased TC removal after the addition of HA (e.g., decreased by 13.2% at 1 V). The decreased TC removal of the control membrane was attributed to the attachment (but not competitive oxidation) of HA on the electroactive layer that impaired the electrochemical reactivity. The HA removal prior to TC degradation realized by the PAN-CNT/PANi membrane avoided the attachment of HA and guaranteed TC removal on the electroactive layer. Long-term filtration for 9 h revealed the stability of the PAN-CNT/PANi membrane, and its advantageous structural design was conformed in the context of real secondary effluents.

Electro mitigation of calcium carbonate and calcium sulfate scaling in an optimized thermal conductive membrane distillation process

Desalination technology can obtain fresh water from brine to alleviate the pressure of global water scarcity. Membrane distillation (MD) is a promising technology for desalination, especially for hypersaline brine. Although the emergence of novel processes enhances the competitiveness of MD in desalination, membrane-based separation technology inevitably leads to membrane fouling, thereby decreasing flux and thermal efficiency. Herein, we prepared an electroactive membrane and using it in an optimized thermal conductive membrane distillation process. Optimizing the thermal conducting layer can improve the desalination performance. Aiming to the typical membrane scaling of calcium carbonate and calcium sulfate, we elucidated the influence of the thermal conducting layer temperature, porosity, and feed velocity on the formation of the foulants. Results showed that the increase in porosity of the thermal conducting layer, the decrease in temperature, and the increase in feed flow velocity were conducive to alleviating the scaling of calcium carbonate and calcium sulfate. Regular electro-cleaning effectively alleviated calcium carbonate scaling, whereas continuous application of a potential to the membrane mitigated the calcium sulfate scaling. The mechanism of electrochemical mitigation of calcium carbonate and calcium sulfate scaling included forming an electric double layer, generating electrostatic repulsion to inhibit the formation of crystals, and changing the pH to dissolve the crystals.

High performance electroactive ultrafiltration membrane for antibiotic resistance removal from wastewater effluent

As emerging contaminants, antibiotic and antibiotic resistance genes (ARGs) in wastewater effluent induce and increase the risk of antibiotic resistance spreading in the environment. Herein, we fabricated a series of polyaniline/carbon nanotube-assisted electroactive membranes (PANI/CNT-EMs) to remove low-concentration antibiotics (i.e., sulfamethoxazole, SMX), antibiotic-resistant bacteria (ARB), and ARGs, thus reducing ecotoxicity and antibiotic resistance pollution in wastewater effluent. The PANI/CNT-EMs possess excellent electrochemical properties with a uniform and stable structure. Compared with pristine EMs, the PANI/CNT-EMs effectively enhanced SMX degradation and substantially lessened the ecotoxicity of the degradation products. The PANI/CNT-EMs show higher inactivation ability in intercepted ARB and significant degradation of both intracellular and extracellular ARGs (iARGs and eARGs) during wastewater effluent electrofiltration under a low voltage of +2 V. More importantly, the reduced integron (i.e., intI1) abundance and ARG transfer frequency further demonstrated that the PANI/CNT-EMs are more conducive to controlling the spread of antibiotic resistance. Furthermore, compared with pristine EMs, the antifouling property of PANI/CNT-EMs is improved by 42.1% during wastewater effluent treatment. Overall, these findings offer a promising approach for antibiotic resistance control in wastewater effluent treatment.

Piezoelectric Polyvinylidene Fluoride Membranes with Self-Powered and Electrified Antifouling Performance in Pressure-Driven Ultrafiltration Processes.

Electroactive membranes have the potential to address membrane fouling via electrokinetic phenomena. However, additional energy consumption and complex material design represent chief barriers to achieving sustainable and economically viable antifouling performance. Herein, we present a novel strategy for fabricating a piezoelectric antifouling polyvinylidene fluoride (PVDF) membrane (Pi-UFM) by integrating the ion-dipole interactions (NaCl coagulation bath) and mild poling (in situ electric field) into a one-step phase separation process. This Pi-UFM with an intact porous structure could be self-powered in a typical ultrafiltration (UF) process via the responsivity to pressure stimuli, where the dominant β-PVDF phase and the out-of-plane aligned dipoles were demonstrated to be critical to obtain piezoelectricity. By challenging with different feed solutions, the Pi-UFM achieved enhanced antifouling capacity for organic foulants even with high ionic strength, suggesting that electrostatic repulsion and hydration repulsion were behind the antifouling mechanism. Furthermore, the TMP-dependent output performance of the Pi-UFM in both air and water confirmed its ability for converting ambient mechanical energy to in situ surface potential (ζ), demonstrating that this antifouling performance was a result of the membrane electromechanical transducer actions. Therefore, this study provides useful insight and strategy to enable piezoelectric materials for membrane filtration applications with energy efficiency and extend functionalities.

Enhance the anti-scaling performance of conductive heating vacuum membrane distillation by carbon nanotube-based electroactive membrane

Membrane distillation (MD) is an emerging technology for the brine desalination. Directly heating feed liquid at the membrane-water interface for improving the performance of MD has been demonstrated, while the problem of membrane scaling remained. Herein, carbon nanotube-based electroactive membranes were prepared and characterized by a variety of methods. It was then used in a conductive heating vacuum membrane distillation system. We firstly increased the flux by optimizing system configuration, placing a spacer in the feed channel, and setting vent holes on the thermal conducting layer. Then, aiming at silicates and sulfates scaling in MD, the electroactive membranes and titanium were used as working electrodes and the counter electrode, respectively, to discuss the electrochemical anti-scaling performance and mechanism. Results showed that the silicate scale on the membrane surface can be effectively cleaned by using the electroactive membrane as the cathode and applying a potential of − 5 V to destroy the structure of the silicate through an electrochemical reaction. With the electroactive membrane as the anode, the scaling of calcium sulfate can be mitigated by providing a continuous potential through electrostatic repulsion. This paper may provide further insights into inorganic scaling control in conductive heating vacuum membrane distillation process.

Preparation of reduced graphene oxide-carbon nanotubes membranes for conductive heating membrane distillation treatment of humic acid

Membrane distillation (MD) has attracted extensive attention as a technology to solve water scarcity in the fields of desalination. Surface-heated membrane distillation techniques that have emerged in recent years have improved flux due to the elimination of temperature polarization, but still suffer from membrane fouling. The use of electrochemical techniques for in-situ cleaning of membrane fouling in MD is expected to be an effective solution. Herein, electroactive membranes were prepared by loading mixtures of reduced graphene oxide (rGO) and carbon nanotube (CNT) with four mass ratios on polytetrafluoroethylene (PTFE) hydrophobic membranes. A series of analytical methods, such as scanning electron microscopy, atomic force microscopy, pore size analysis, water contact angle, Raman spectroscopy, membrane surface zeta potential, and cyclic voltammetry curve, were employed to characterize the properties of the rGO-CNT membranes. The best separation performance and conductivity were achieved at a 2:1 mass ratio of rGO to CNTs (R2 membrane). Then, the rGO-CNT membranes were applied to a conductive heating vacuum membrane distillation system to treat humic acid (HA). Compared with the PTFE membrane, the four rGO-CNT membranes showed a significant improvement in the rejection of HA. Using the rGO-CNT membranes as the cathode and the titanium as the anode, after a certain potential was applied, the flux decreases slowly. The fluxes of all rGO-CNT membranes were maintained over 9.5 kg/(m2·h) for 10 h of continuous operation. An increase in potential helps to increase change by alleviating membrane fouling. The highest flux and HA rejection reached 13 kg/(m2·h) and 99.8 %, respectively, with R2 membrane and −5 V potential applied. The mechanism of antifouling included electrostatic repulsion and electrocatalytic oxidation.

Improvement of microbial extracellular electron transfer via outer membrane cytochromes expression of engineered bacteria

The effective contact between proteins on the electroactive membranes or nanowires determines the efficiency of the electroactive in bioelectrochemical systems (BES) biofilm. However, most electroactive biofilms are multi-layer bacterial aggregates, and the microorganisms in the outer layer cannot directly contact the electrode surface electron transfer. Herein, we construct a genetically engineered bacterium (GEB) that can express outer membrane cytochrome OmcA to improve the microbial extracellular electron transfer in the biofilm. The engineered bacterium improves the maximum power density of the mixed bacteria microbial fuel cell (MFC) by 2.36 times to 3.76 A cm−2, and increases the current density to 1.98 W m−2. This improved behavior was stable for at least three feeds. Adding the engineered bacteria generates a more compact biofilm structure and significantly improves the electrochemical performance of the anode biofilm. The engineered bacteria with the electron transfer function also increase the content of the OmcA gene in the bacterial community, thereby promoting the microbial extracellular electron transfer and increasing the proportion of electrogenic bacteria in the biofilm. With its expression of the conductive protein, the GEB can effectively improve the extracellular electron transfer efficiency of the outer layer bacteria in the biofilm of the MFC. Our study provides a new choice for building an efficient electrochemical system.