Anti-biofouling Membranes Research Articles

Anti-biofouling membrane coated with polyvinyl alcohol/sodium carboxymethylcellulose/tannic acid hydrogel for efficient dye/salt separation

Biofouling is the most severe challenge for separation membranes. In this study, a metal-organic framework (MOF)-based mixed-matrix membranes (MMMs) with polyvinyl alcohol (PVA)/sodium carboxymethylcellulose (CMC)/tannic acid (TA) hydrogel coating exhibited a comprehensive anti-biofouling property and high efficient for dye/salt separation. For the hydrogel layer, ethanol inhibited the cross-linking of the hydrogen bond between the PVA, CMC and TA, forming a uniform “hydrogel paint” applied to the membrane surface using the coating method. Subsequently, the hydrogen bond was re-established by evaporating the ethanol. The hydrogel coating could form a dense hydrated layer, endowing the membrane with excellent anti-fouling properties, including oil, proteins, and bacteria. For the MOF-based MMMs layer, the skeleton structure of polyvinylidene fluoride anchored the bimetallic MOF crystals to mitigate the phenomenon of “trade-off”. The hydrogel-coated MOF-based MMMs showed excellent properties, such as the water permeability was ~200 Lm−2 h−1, the rejection for Reactive Blue 19 was 100 %, the rejection for NaCl was 10.9 %, and it showed excellent stability for long-term service. Furthermore, the hydrogel-coated MOF-based MMMs presented a significant inhibitory effect on surface bacteria growth. In brief, this paper provided a new insight into preparing hydrogel-coated MOF-based MMMs, which had potential applications in separating dye/salt.

Innovative temperature-responsive membrane with an elastic interface for biofouling mitigation in industrial circulating cooling water treatment

To address the issues of scaling caused by heat and water evaporation in regard to circulating cooling water (CCW), TFC membrane filtration systems have been increasingly considered for terminal treatment processes because of their excellent separation performance. However, membrane biofouling phenomenon significantly hinders the widespread utilization of TFC membranes. In this study, to harness the thermal phenomenon of CCW and establish a stable and durable multifunctional antibiofouling layer, temperature-responsive Pnipam and the spectral antibacterial agent Ag were organically incorporated into commercially available TFC membranes. Biological experimental findings demonstrated that above the lower critical solution temperature (LCST), the contraction of Pnipam molecular chains facilitated the inactivation of bacteria by the antibacterial agent, resulting in an impressive sterilization efficiency of up to 99 %. XDLVO analysis revealed that below the LCST, the establishment of a hydration layer on the functional interface resulted in the creation of elevated energy barriers, effectively impeding bacterial adhesion to the membrane surface. Consequently, a high bacterial release rate of 98.4 % was achieved on the low-temperature surface. The alterations in the functional membrane surface conformation induced by temperature variations further amplified the separation between the pollutants and the membrane, creating an enhanced "elastic interface." This efficient and straightforward cleaning procedure mitigated the formation of irreversible fouling without compromising the integrity of the membrane surface. This study presents a deliberately engineered thermoresponsive antibiofouling membrane interface to address the issue of membrane fouling in membrane-based CCW treatment systems while shedding new light on the mechanisms of "inactivation" and "defense."

Biomimetic peptoid-assisted fabrication of antibiofouling thin-film composite membranes

Polyamide (PA) thin-film composite (TFC) membranes are extensively used in water purification but suffer from chronic biofouling, which has spurred extensive research on the development of antibiofouling membranes. In this study, we present a facile method to fabricate a biofouling-resistant, high-performance PA TFC membrane by adding a biomimetic antimicrobial peptoid (i.e., oligo-N-substituted glycines) to the reaction medium during an interfacial polymerization (IP) process. The amphiphilic peptoid facilitates IP by acting like a surfactant, thereby enabling the formation of a highly crosslinked and permeable PA separation layer. Consequently, the peptoid-added TFC (pept-TFC) membrane exhibits superior separation performance compared with pristine, commercial, and other laboratory-made TFC membranes. Furthermore, because the peptoid is strongly incorporated into the PA separation layer network, the resultant pept-TFC membrane is endowed with excellent antimicrobial and antibiofouling properties. Importantly, the enhanced separation and antibiofouling performances of the pept-TFC membrane persist during long-term membrane operation, indicating the robust implantation of the peptoid and permanent changes in the structure and properties of PA. The proposed strategy provides a versatile and environmentally benign platform for fabricating functional membranes by simply employing structurally tailored peptoids with specific functions.

Construction of antimicrobial peptides/alginate multilayers modified membrane: Antibiofouling performance and mechanisms

Biofouling remains to be one of major obstacles for membrane-based technology in water and wastewater treatment, calling for the development of antibiofouling membranes. For the traditional release-killing strategy, uncontrollable release of biocides and thus a short lifetime as well as the potentially environmental risk are thorny issues for the modified membranes. Herein, hydrophilic hydrogel multilayers with controllable thickness at nanometer scale on a poly(vinylidene fluoride) (PVDF) microfiltration membrane were constructed via layer-by-layer (LbL) self-assembly of non-drug-resistant antimicrobial peptides (AMPs) and alginate. The AMPs/alginate multilayers modified membranes exhibited enhanced hydrophilicity, well-controlled pore size distribution and prominent antimicrobial ability against Escherichia coli and Staphylococcus aureus. As the number of multilayers of alginate increased, both initial and steady release rate of Ponericin G1 reduced; in particular, the AMPs/alginate modified membranes with fifteen multilayers (MSA15) had the slowest release kinetics (i.e., an initial release rate of 1.79 ± 0.07 μg/cm2 d and a steady release rate of 0.55 ± 0.03 μg/cm2 d), resulting in about 60% less release compared with the AMPs/alginate modified membranes with five multilayers (MSA5). Long-term antibiofouling tests showed that the AMPs/alginate modified membranes with ten multilayers (MSA10) exhibited a significantly reduced transmembrane pressure increase rate of 0.81 ± 0.01 kPa/d which was much lower than that of the control membranes (1.80 ± 0.20 kPa/d), mainly attributed to the antibacterial activity imparted by the lasting release of AMPs and competing membrane basic properties. Furthermore, the AMPs/alginate multilayers modified membranes revealed high stability suffering from long-term operation and chemical cleaning cycles. The novel AMP/alginate-incorporated modifying method provides a new dimension to enhance antibiofouling performance of membranes for water and wastewater treatment.

Minimizing bacterial adhesion on membrane: Multiscale characterization of surface modifications

The control of biofouling is required to improve membrane performance for water filtration. In this context, developing bioinspired approaches to modify membranes and give them antifouling properties is an interesting alternative. In this study, we elaborated new anti-biofouling membranes by coating them with vanillin, a natural bioactive molecule acting as a Quorum Sensing Inhibitor (QSI). The adsorption of vanillin by filtration was optimized to obtain homogeneous surface modifications. The modified membranes were then characterized in terms of physical-chemical properties: the results showed that they were more hydrophobic and exhibited a 14% decrease in pure water flux. Then, their anti-fouling properties were evaluated using complementary multiscale characterization methodologies: AFM single-cell experiments showed that vanillin adsorption had an effect on both the probability of bacterial cells to adhere to the surface, and on the force of adhesion. Direct EFM and SEM observation and adhesion assays further confirmed the effect of vanillin-modified membranes at the population-scale which showed a decrease in the bacterial coverage rate up to 50%. Altogether, it confirms the multifunctionality of vanillin-coated membranes against biofouling: reduction of bacterial initial adhesion by changing the membranes surface properties and reduction of biofilm formation by quorum sensing inhibition.

Facile preparation of anti-biofouling nanofiltration membrane using safety inhibitor with high separation performances

Anti-biofouling nanofiltration (NF) membranes can reduce the damage of bacteria to membranes and are typically fabricated by grafting bactericidal chemicals on membrane surface, with potential environmental safety issues as well as health hazards. Vanillin (VA) is a natural non-toxic bacterial inhibitor that has been proven to inhibit a wide range of bacteria. In this study, VA was introduced as an aqueous phase additive to the selective layer by interfacial polymerization reaction thus preparing NF membranes with excellent anti-biofouling properties. The biofilm area on the optimized membrane surface formed by Bacillus subtilis and Escherichia coli were reduced by 66.0 % and 75.1 %, respectively. In addition, the hydrophilicity enhancement and the membrane surface roughness reduction were attributed to the VA introduction, which resulted in an improvement of the anti-adhesion properties of modified membranes, and flux recovery ratio of optimal membranes was 75.7 % while flux decline ratio was 50.4 %. The water permeability for mixed salt solution of membrane with the optimized VA concentration was 1.22 times higher than control membrane and rejection of NaSO4 was 99.0 %, meanwhile the separation factor of NaCl/Na2SO4 stabilized in the range of 27.4–28.0. This facile process provided an non-biotoxic method to prepare environmentally friendly and effective anti-biofouling membranes.

Tailoring Zeolite-Composite (ZC) Impregnated Thermally Endured Nonporous Cellulose Acetate Membranes for Potential Gas Separation and Antibacterial Performances

Cellulose acetate (CA) composite membranes are tailored for potential gas-transportation and antibacterial activity by incorporating various ratios (0-8wt. %) of zeolite-CuO (10:1, ZC) composite. The aim behind this is to develop an anti-biofouling membrane with enhanced CO2permeation and selection properties. In situ coprecipitation route is adopted to synthesize ZC that imparted morphological, structural, thermal, and performance characteristics of membranes synthesized by solution casting mechanism. FESEM analysis revealed, pores size transformed from 1µm to 1.4 nm as observed in M0 (virgin) and M4 (8wt. % ZC) membranes, respectively. The existence and linkages of impregnated ZC in the developed membranes are verified by FTIR investigations. TGA-tested thermally endured membranes are tested for gas permeation/selectivity. In comparison to virgin CA membrane, three folds enhancements in CO2permeation and two folds in CO2/N2selectivity are observed. Membranes are also evaluated for antibacterial test against ‘gram-negative bacteria’ elucidates that increasing ZC content in composite membranes exhibit remarkable results.

Graphene oxide/methyl anthranilate modified anti-biofouling membrane possesses dual functions of anti-adhesion and quorum quenching

Biofouling has always been a persistent problem impeding the applications of membranes in water treatment. Quorum sensing (QS) inhibitors are able to interfere with bacterial cell-to-cell communication to alleviate membrane biofouling, among which, methyl anthranilate (MA) aims at disrupting the Pseudomonas quinolone signal (PQS)-mediated QS system to inhibit biofilm formation. In this study, we developed a novel anti-biofouling membrane via immobilizing MA on graphene oxide (GO) nanocarrier, which was then successfully coated onto a polyvinylidene fluoride (PVDF) membrane through layer-by-layer assembly method. The introduction of QS inhibitor MA suppressed the expression of PQS synthesis gene pqsABCDE, N-acyl homoserine lactones (AHL) synthesis gene lasI, rhamnolipid synthesis gene rhlA and PQS receptor gene pqsR, thereby mitigating biofilm formation on the modified membrane. GO on membrane surface contributed to the reduction of bacterial initial adhesion. The synergistic effect of GO and MA endowed the modified membrane with dual resistance to biofouling. Compared with the virgin membrane, the extracellular polymeric substances (EPS), ATP and total cell fluorescence on GO/MA-PVDF membrane (GO:MA = 1:3, 5 layers) were substantially reduced by 50%, 73% and 86%, respectively, illustrating its excellent anti-biofouling capability. Notably, the incorporation of GO/MA was still efficient when treating real secondary effluent, with the evidence of lower flux decline and restrained biofilm formation. Taken together, we believe that GO/MA-PVDF membrane with both anti-adhesion and anti-biofilm capability has broad prospects for biofouling control in water treatment.

Induced mazEF-mediated programmed cell death contributes to antibiofouling properties of quaternary ammonium compounds modified membranes

Functionalized antibiofouling membranes have attracted increasing attention in water and wastewater treatment. Among them, contact-killing antibiofouling membranes deliver a long-lasting effect with no leaching or release, thus providing distinctive advantages. However, the antibiofouling mechanism especially in the vicinity of the membrane surface remains unclear. Herein, we demonstrate that mazEF-mediated programmed cell death (PCD) is critical for the antibiofouling behaviors of quaternary ammonium compounds modified membranes (QM). The viability of wild type Escherichia coli (WT E. coli) upon exposure to QM for 1 h was decreased dramatically (31.5 ± 1.4% of the control). In contrast, the bacterial activity of E. coli with the knockout of mazEF gene (KO E. coli) largely remained (85.8 ± 5.2%). Through addition of quorum sensing factor, i.e., extracellular death factor (EDF), the antibacterial activity was significantly enhanced in a dilute culture, indicating that the density-dependent bacterial communication played an important role in the mazEF-mediated PCD system in biofouling control. Long-term study further showed that QM exhibited a better antibiofouling performance to treat feedwater containing WT E. coli, especially when EDF was dosed. Results of this study suggested that the bacteria on the membrane surface subject to contact killing could modulate the population growth in the vicinity via quorum-sensing mazEF-mediated PCD, paving a way to develop efficient antibiofouling materials based on contact-killing scenarios.

Anti-biofouling property and anti-leaching investigation of modifier for PVDF ultrafiltration membrane by incorporating antibacterial graphene oxide derivatives

To improve the anti-biofouling property of polyvinylidene fluoride (PVDF) membrane, three kinds of antibacterial graphene oxide (GO) derivatives were prepared, including imidazole-functionalized GO (Im-GO) and quaternized GO (Q-GO) synthesized by chemical grafting method, and GO loaded with silver nanoparticles (GO-Ag) synthesized by in-site reduction method. The structural characteristics and antibacterial abilities of three kinds of GO derivatives were characterized and investigated. It was demonstrated that GO could be used as a good carrier to prepare the anti-biofouling modifiers. Correspondingly, Im-GO/PVDF, Q-GO/PVDF, and GO-Ag/PVDF ultrafiltration membranes were fabricated using the phase inversion method. In contrast with the blank PVDF membrane, all the GO derivatives/PVDF membranes showed greatly improved permeability and anti-biofouling property. Significantly, the inhibition zone test and fluorescence staining experiment were carried out to investigate the differences between Im-GO, Q-GO, and GO-Ag in the antibacterial mechanisms. The corresponding results suggest that the imidazole and quaternary ammonium salt groups grafted on Im-GO and Q-GO possess great anti-leaching characteristics, while the loss of Ag+ from GO-Ag is relatively obvious. Therefore, Im-GO and Q-GO synthesized by chemical grafting method have greater potential as the anti-biofouling membrane modifiers, considering the accumulation of harmful ions in water and possible reduction in antibacterial stability for GO-Ag.

A super-hydrophobic and antibiofouling membrane constructed from carbon sphere-welded MnO2 nanowires for ultra-fast separation of emulsion

The discharge of large quantities of oily wastewater has become a serious threat to ecosystem and human health. Superhydrophobic/superhydrophobic under-oil porous materials have received considerable attention for its applications in oil/water mixture separation. However, some challenges still exist, such as low flux, poor stability, and high production cost. Here, a simple vacuum filtration-calcination welding method was used to fabricate super-hydrophobic membranes for the ultra-fast separation of W/O emulsions. Inorganic nanowires MnO2 and carbon spheres were used as the membrane-forming material. Here, carbon spheres not only function as the pore-forming and weld agent to form welded nanowire-constructed framework, but also improve membrane surface roughness. Through this fabrication technique, the resulting composite membrane has a very stable structure. Compared with those of most previously reported advanced oil/water separation membranes, the super-hydrophobic MnO2&Carbon Sphere (MCS) composite membranes show remarkable high separation fluxes and separation efficiencies for various oil phases with different viscosities. In addition, the superhydrophobic membranes show excellent reusability, which is greatly important for long-term oil/water separation applications. In addition, the prepared super-hydrophobic MCS composite membrane shows obvious anti-bacterial properties. The high separation fluxes and long-lasting cycling stability of super-hydrophobic MCS composite membrane make it show great potential in water purification application.

Electroless deposition of copper nanoparticles integrates polydopamine coating on reverse osmosis membranes for efficient biofouling mitigation

In this study, highly antimicrobial CuNPs were integrated into a hydrophilic polydopamine (PDA) coating and immobilized on a RO TFC membrane via a mild and facile reduction approach to form a stable and durable dual-functional layer. Based on the XDLVO analysis, the introduction of PDA increased the membrane-foulant total interaction energy (ΔGmwf) to 14.13 mJ/m2, resulting in improved anti-adhesive properties as demonstrated by a 37% decrease in BSA adsorption for the modified membranes. The well dispersed and high loadings of CuNPs induced by PDA conferred strong bacterial toxicity to the modified membranes, reducing the viability of E. coli by 76%. Furthermore, the presence of catechol groups on PDA favors the formation of covalent bond with CuNPs, thus prolonging the durability of the copper-based anti-biofouling membranes. The combination of PDA coating and CuNPs functionalization imparts the membrane with simultaneous anti-adhesive and anti-microbial properties, leading to a substantial reduction in biofouling propensity in dynamic biofouling experiments. Specifically, the flux decline due to biofouling observed for the modified membranes significantly decreased from 65% to 39%, and biofilm thickness and TOC biomass were 58%, and 55% lower, respectively. This study provides a facile and versatile strategy to construct high performance RO membranes with excellent anti-biofouling functionality.

Layered Antibiofouling Composite Membrane for Quenching Bacterial Signaling.

Bacterial quorum quenching (QQ) media with various structures (e.g., bead, cylinder, hollow cylinder, and sheet), which impart biofouling mitigation in membrane bioreactors (MBRs), have been reported. However, there has been a continuous demand for membranes with QQ capability. Thus, herein, we report a novel double-layered membrane comprising an outer layer containing a QQ bacterium (BH4 strain) on the polysulfone hollow fiber membrane. The double-layered composite membrane significantly inhibits biofilm formation (i.e., the biofilm density decreases by ~58%), biopolymer accumulation (e.g., polysaccharide), and signal molecule concentration (which decreases by ~38%) on the membrane surface. The transmembrane pressure buildup to 50 kPa of the BH4-embedded membrane (17.8 h ± 1.1) is delayed by more than thrice (p < 0.05) of the control with no BH4 in the membrane’s outer layer (5.5 h ± 0.8). This finding provides new insight into fabricating antibiofouling membranes with a self-regulating property against biofilm growth.

Integration of a Hydrophilic Hyperbranched Polymer and a Quaternary Ammonium Compound to Mitigate Membrane Biofouling

Membrane biofouling, adhesion of microorganisms on the surface and the subsequent formation of a biofilm, remains a persistent and inevitable issue, which results in a dramatic reduction of permeability and lifespan. Constructing a membrane with active bacteria-killing and passive anti-adhesion properties is still a challenge to mitigate membrane biofouling. Herein, an active–passive anti-biofouling membrane was originally fabricated by integration of hydrophilic hyperbranched poly(N-acryloylmorpholine) (HPA) and the dimethylaminoethyl acrylate–dodecylammonium bromide (DD) quaternary ammonium compound. Inspired by modern dopamine biomimetic adhesion chemistry, thiolated HPA was first immobilized on the polydopamine (PD)-modified poly(vinylidene fluoride) membrane surface through Michael addition, followed by conjugation of DD via a thiol–ene click reaction. The membrane surface changes of the chemical structure, hydrophilicity, and zeta potential proved that bacteria-killing DD and the anti-adhesion HPA layer were successively conjugated. The initial contact angle of the M-PD/HPA/DD membrane was reduced from 120.5° for the pure membrane to 52.3°. Furthermore, the water flux of the M-PD/HPA/DD membrane increased from 318.9 L m–2 h–1 (0.02 MPa) for the pure membrane to 854.4 L m–2 h–1. In addition, the M-PD/HPA/DD membrane exhibited excellent active bacteria-killing property with inhibition rates of ∼90% for Escherichia coli and ∼95% for Staphylococcus aureus, respectively. Meanwhile, in the filtration of artificial bacteria wastewater, the M-PD/HPA/DD membrane showed a higher water flux recovery rate of 86.9% than 43.3% for the pure membrane, indicating an excellent anti-biofouling property. Therefore, this molecular-level design approach for the modification of the membrane surface could significantly enhance permeability and mitigate membrane biofouling, which provides a promising dimension for the preparation of the anti-biofouling membrane.

Pilot-scale modification of polyethersulfone membrane with a size and charge selective nanocellulose layer

The utilisation of plant-derived nanoscale cellulosic materials (cellulose nanofibrils, CNF) in tailoring water purification membranes is constantly gaining interest in the context of green-functionalised membrane solutions. However, most of the existing approaches based on renewable and biobased materials suffer from the lack of efficient and scalable processing strategies. Here, we introduce a roll-to-roll membrane modification approach based on thin submicron nanocellulose coatings (400–800 nm) to manufacture anti-biofouling membranes with size and charge dependent selectivity using unit operations compatible with existing industrial lines. We turned a commercial polymeric polyethersulfone (PES) microfiltration membrane into highly hydrophilic and tight membrane structure by applying thin and water-durable cellulose nanofibril layers using cast or spray coating methods. Nanocellulose coated membranes exhibited water permeance values of 80 – 100 LMH/MPa with the highest rejection levels of > 90% for Cytochrome C. Furthermore, the nanocellulose layers were able to withstand relatively high filtration pressure levels of 1 MPa, indicating that the selected procedures to improve mechanical integrity i.e. polyethylene imine-based anchoring and acid induced CNF cross-linking were successful. The coated membranes with the thinnest nanocellulose layer exhibited a molecular weight cut-off (MWCO) of 2 kDa for negatively charged polystyrene sulfonate and 14 kDa for neutral dextrane indicating charge selective behaviour. It can be concluded that our nanocellulose coated PES membranes represent nanofiltration membranes and lower boundary of ultrafiltration membranes with clear anti-biofouling performance directly evidenced via systematic bovine serum albumin (BSA) adsorption investigations. Our approach paves the way towards tunable and sustainable water treatment technologies simultaneously opening space for novel biobased solutions in membrane sector.

Fabrication of CuO nanoparticles immobilized nanofiltration composite membrane for dye/salt fractionation: Performance and antibiofouling

The separation of dye/salt mixtures is a challenging task in treating high salinity textile industrial wastewater. Therefore, there is a need to develop highly permeable and antibiofouling membranes for efficient disposal of textile industrial effluents. Membrane-based separation is evolving as an alternative purification technology to the conventional energy intensive separation and purification processes. In the current work, a new loose nanofiltration membrane was fabricated through two rounds of interfacial polymerization on ultrafiltration polysulfone support by constructing copper oxide (CuO) nanoparticles (NPs) containing semi-Interpenetrating Network (semi-IPN) polyamide as an active layer. The newly constructed thin film nanocomposite loose nanofiltration membrane namely CuO/PA@PS/PET was thoroughly characterized by ATR-FTIR, FESEM, AFM, Zeta-potential, Water Contact Angle (WCA), EDX, elemental mapping and XRD. FTIR and FESEM analysis of the membrane showed the contribution of hydrophilic CuO NPs in the crosslinking event of the fabrication of semi-IPN active layer. The WCA was decreased from 78° in case of PS/PET to 62° CuO/PA@PS/PET. The CuO/PA@PS/PET showed exceptional performance in terms of flux of DI water reaching to > 140 L/m2h−1 at 16 bars and > 99% rejection of Methylene Blue (MB) while allowing CaCl2, MgCl2 and NaCl to permeate through it. The incorporation of CuO NPs not only enhanced the water flux and rejection but it also developed antibiofouling features of the membrane as the CuO/PA@PS/PET showed bacteriostasis of E. coli and S. aureus upto 95.19% and 82.23%, respectively. Hence, the newly fabricated CuO/PA@PS/PET membrane can be an excellent choice for fractionating dye/salt mixtures with remarkable antibiofouling.

Simultaneous production and extraction of bio-chemicals produced from fermentations via pervaporation

Pervaporation (PV) technology has been widely applied for the separation of different types of azeotropic mixtures, aching its large-scale application in industry for the dehydration of organics (e.g., ethanol, butanol, among others). So far, thanks to its versatility and high selectivity towards specific molecules, PV has been a candidate to assist chemical and biochemical reactions. Fermentative processes allow the production of specific bio-based chemicals of interest, such as ethanol, butanol, acetone, among others. However, their separation and extraction from fermentation broths is a challenging task due to their complexity, in this regard, PV has been successfully applied. Therefore, the goal of this review is to elucidate and provide a compelling outlook about the potential of PV for the separation of such chemicals. A particular emphasis has been paid to the key developments and meaningful insights in the recovery of bio-chemicals from fermentation broths along with future trends and perspectives in the field. For the new readers in the field, a brief introduction of the PV technique and its principles are also given. Further large-scale implementation of PV processes remains a challenge due to several constraints including cost, specificity, fouling, and energy-consumption. However, implementation of new materials, PV-fermentation configurations, anti-biofouling membranes, and reduction of by-products through genetic, metabolic, or system modifications, represent an alternative to overcome such limitations.

Live membrane filters with immobilized quorum quenching bacterial strains for anti-biofouling

Membrane filters are core materials for water treatment, reuse, and desalination. However, their fouling caused by biofilm growth is a major challenge, needing resolution. Here, we report the new strategies and efficacy of anti-biofouling membranes fabricated through the immobilization of quorum quenching (QQ) bacterial strains (Rhodococcus sp. BH4). The QQ cells are not attached to the membrane by direct phase inversion. However, they anchor to the membrane with its incubation in the presence of hydrophilic polymers (polyvinyl alcohol and alginate) as evidenced in the spectroscopic and morphological observations. Membrane filters with live QQ bacteria can degrade a signal molecule (N-octanoyl-l-homoserine lactone) with the first-order rate constant of 0.58–0.82 h−1 and inhibit the growth of a biofilm-forming bacterium (PAO1) and its secretion of biopolymers. The QQ membrane demonstrates its significant anti-biofouling effect in bioreactors for treating synthetic wastewater (i.e., membrane fouling was delayed by 57–67% compared to the naked membrane), although the initial water permeabilities are reduced with surface modification by 34–47% compared to pristine condition. The findings of this work bring the broad potential for material fabrication requiring biofouling control, encountered in our daily lives and mechanical, marine, and medical industries in addition to membrane filters.

Facile ultrasonic preparation of a polypyrrole membrane as an absorbent for efficient oil-water separation and as an antimicrobial agent

Polypyrrole (PPY) spherical particles synthesized using carbon dots as an efficient catalyst were strongly embedded on fluorinated nonwoven fabric by ultrasonication to form a membrane with high hydrophilicity. An optimal amount of PPY adhered to the membrane after 30 min of sonication enhanced the overall membrane area with high hydrophilicity. Oil with high hydrophobicity was repelled by the resulting membrane, whereas water was freely penetrated and diffused from the membrane. The membrane exhibited good reusability and efficiency for the recovery of oil from a cooking oil–water mixture within 30 s. The incorporation of PPY in the fluorinated fabric imparts significant antibacterial properties against two common pathogens, Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The anti-biofouling membrane could pave the way for its potential application to separate spilled oil from contaminated waters, comprising different microorganisms and living species. The novelty of this manuscript is described in a new system, the fabrication of PPY membranes with two important properties: biocidal and oil/water separation.

Antibiofouling Thin‐Film Nanocomposite Membranes for Sustainable Water Purification

AbstractMembrane technology provides a reliable and powerful solution to combat the global water crisis by producing fresh water through sustainable desalination. However, the decline in system performance due to membrane biofouling is a limitation and significant efforts have been made to explore fouling control mechanisms and develop simple methods to inhibit or eliminate membrane fouling. Nanotechnology has increased the number of options for the development of antibiofouling membranes by incorporating nanoparticles within the polyamide layer to produce a thin‐film nanocomposite (TFN) structure. This review presents recent advances in the preparation of antifouling TFN membranes and incorporation of different nanoparticles into the design. The review also discusses the strategies and mechanisms for reducing membrane fouling and proposes a future outlook for the field.