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• Zwitterionic hydrogel nanolayer was synthesized by interfacial polymerization. • Zwitterionic monomer modulated the hydrogel layer structure and membrane characters. • Zwitterionic hydrogel hindered the adhesion of biomacromolecules and killed microbes. • The growth of biofilm on zwitterionic hydrogel nanolayer surface was inhibited. Ultralow-pressurized ultrafiltration membrane process with low energy consumption is promising in surface water purification. However, membrane fouling and low selectivity are significant barriers for the wide application of this process. Herein, an ultrathin zwitterionic hydrogel nanolayer was in-situ grown on polysulfone ultrafiltration membrane surface through interfacially-initiated free radical polymerization. The hydrogel-modified membrane possessed improved biological fouling resistance during the dynamic filtration process (bovine serum albumin, Escherichia coli and Staphylococcus aureus), comparing with commercial polysulfone membrane. The enhanced biofouling resistance ability of zwitterionic hydrogel nanolayer was derived from the foulant repulsion of hydration shell and the bactericidal effect of quaternary ammonium, according to the results of foulant-membrane interaction energy analyses and antibacterial performances. In surface water treatment, the zwitterionic hydrogel layer inhibited biofouling and resulted in the formation of a loose and thin biofilm. In addition, the hydrogel-modified membrane possessed 22% improvement in dissolved organic carbon (DOC) removal and 134% increasement in stable water flux, compared to commercial polysulfone membrane. The in-situ grown zwitterionic hydrogel nanolayer on membrane surface offers a prospectively alternative for biofouling control in ultralow-pressurized membrane process. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract We demonstrated a dual-functionalization strategy of polymeric membrane with both "defensive" (adhesion resistance) and "offensive"(bacterial inactivation) efficacies via combining external-hydrophilic β-cyclodextrins (β-CDs) and bactericidal enrofloxacin (ENR) for combating biofouling. β-CDs were immobilized onto polydopamine (PDA) pre-modified membrane surface, followed by host-guest assembly of ENR. Both static adhesion tests and dynamic fouling experiments implied that the CD-modified membranes showed significantly reduced adsorption and lower water flux decline against organic foulant. The enhanced "defensive" (fouling resistance) capacity of CD-modified membrane was mainly attributed to hydrophilicity improvement. Next, antimicrobial tests demonstrated that the integration of ENR in the functional layer could improve the "offensive" (biocidal) activity of modified membrane. Conspicuous reduction in biomass and ATP content further illustrated that the PVDF/CD-ENR membranes could effectively suppress biofilm formation during dynamic cross-flow biofouling tests. Finally, flow cytometry (FCM) assessment was first combined with heterotrophic plate counts (HPC) method in the present study, implying that the antimicrobial mechanism of the dual-functional membrane lies in inhibition of bacterial breed without disrupting the cell membrane. Graphical abstract Schematic illustration of dual-functionalization on PDA-based polymeric membrane and mechanism of action. fx1 Highlights • Hydrophilic CD-modified membranes exhibited enhanced fouling resistance property. • ENR host-guest assembly in CD layer imparts outstanding antimicrobial efficacy. • PVDF/CD-ENR membranes suppress biofilm formation during cross-flow experiments. • Antimicrobial mechanism lies in bacterial inhibition without cell membrane damage. • This modification strategy is substrate-independent for organic/bio-fouling control. [ABSTRACT FROM AUTHOR]

Increasing attention has been focused on the removal of micropollutants from contaminated drinking source water. However, low rejection efficiency and membrane fouling still inhibit further application of nanofiltration membrane in this field. Interesting results were found that the residual hydrolyzed-aluminum nanoparticles from supernatant after coagulation and sedimentation strongly improved the nanofiltration performance for micropollutant removal. A simulated raw water containing humic acids, micropollutants and kaolinite clay was employed to investigate the factors of water matrix affecting the nanoparticle-enhanced nanofiltration for micropollutant removal. Results of experiments showed that these hydrolyzed-aluminum nanoparticles easily induced the aggregation of bisphenol-A (BPA) and humic acids in the supernatant. The enhancement of BPA removal was mainly attributed to the repelling interaction between the Al-BPA-DOC complexity and in situ -modified membrane surface during nanofiltration. 'This in situ surface modification by the hydrolyzed-aluminum nanoparticles improved membrane hydrophilicity, roughness and positively-charging capacity. For the treatment of River Songhua water spiked with micropollutant, the percentage removal of BPA was improved to be 88.5%, much more than the case of single nanofiltration without coagulation (60.7%). Meanwhile, the membrane fouling was reduced by 2.13 times than the case of single nanofiltration without the dynamically deposited-layer of nanoparticles. This in situ modification of nanofiltration membrane by hydrolyzed-aluminum nanoparticles achieved excellent removal efficiency for micropollutants from River Songhua water background. Image 1 • Micropollutant removal by nanofiltration was enhanced by hydrolyzed-aluminum nanoparticles. • Loosely hydrophilic deposition on membrane surface alleviated membrane fouling. • Aluminum-deposited membrane achieved excellent performance in background of river water. [ABSTRACT FROM AUTHOR]

Inhibiting algae-induced membrane fouling has become an extremely challenging work in algae-laden water treatment. In this study, we developed a novel Polyvinylidene Fluoride (PVDF) ultrafiltration membrane to inhibit algal fouling by in-situ formed four-arms star poly(styrene)- block -poly(ethylene oxide)monomethacrylate (FAS-PS- b -PEGMA) micropillars on membrane surface via nonsolvent induced phase separation technique. Morphology characterization revealed that the protruding micropillars were formed on membrane surface after the addition of FAS-PS- b -PEGMA. The formation of micropillars affected phase separation behaviors, resulting in more porous membrane structure. Surface analyses suggested that the hydrophilic PEGMA chains of the amphiphilic copolymers were enriched onto the surfaces of micropillars, and endowed the modified membranes with higher hydrophilicity and lower electronegativity. The excellent permeability and antifouling properties of the modified membranes were demonstrated by gravity-driven filtration of Microcystis aeruginosa solution. Especially for M5 membrane, the stable permeation flux was more than 5 times than that of the control membrane. The flux decline ratio was only 51.3%, which was much lower than the control membrane (80.1%). Furthermore, the analyses of fouling layer further confirmed that the micropillars could inhibit the accumulation of algae cells on the membrane surface. This study provides a one-step strategy on the modulation of ultrafiltration membrane preparation, modification and performance for algae-laden water treatment. [Display omitted] • A novel PVDF membrane was prepared by in-situ formed hydrophilic micropillars on surface. • The membrane exhibited more porous structure. • The micropillars endowed the membrane with higher hydrophilicity and lower electronegativity. • The micropillars inhibited the coverage of algae cells on the membrane surface. • The permeability and antifouling properties of membranes were markedly enhanced. [ABSTRACT FROM AUTHOR]

Understanding the influences of cations on membrane fouling was important to improve the performance of membrane filtration system, however, opposite conclusions were made in different studies. Meanwhile, although the influences of cation concentration have been studied extensively, few attentions have been paid to the cation valence. To clarify it, the effects of typical cations on membrane fouling and cleaning, as well as the related mechanisms were investigated systemically in this study. K+ and Ca2+ were chosen as the representative cations, and humic acid (HA) was chosen as the membrane foulants. The results demonstrated Ca2+ promoted the formation of reversible fouling, meanwhile higher removal efficiency of HA could also be achieved with the assistance of filtration cake containing HA + Ca2+. However, K+ led to the formation of more recalcitrant irreversible fouling. By comparing the concentration of cations in feed and permeate, analyzing the influence of cations on size of HA flocs, and the detailed SEM, AFM and TEM observation, it could be found that different mechanisms dominated the interaction between cations and HA. The bridging effect induced by Ca2+ attributed to the extension of HA molecules, while the electrostatic shielding effect induced by K+ led to the compression of them. Moreover, the different characteristics of hydrated Ca2+ and K+ also contributed to the different structures of foulant layers formed by HA + Ca2+ and HA + K+. Given the abundance of K+ and Ca2+ in natural water, results of this study can provide valuable advice for practical membrane filtration process. Image 1 • K+ makes the HA pollution layer more compact by electrostatic shielding. • HAs aggregation driving by HA-Ca2+ complexation contributes to pollutant removal. • The hydration force of cations is a key factor for membrane fouling. [ABSTRACT FROM AUTHOR]

In this study, we demonstrated the antifouling MOF membrane via the in-situ growth of metal azolate framework-4 (MAF-4) on polyethersulfone (PES) substrates and then epitaxial growth of MAF-7. The basal MAF-4 layer, which was confirmed to bind to the substrate by chelation, was flawless to ensure the desalination performance. The upper MAF-7 shell, which was confirmed to possess crystal characteristics and leave an unbound nitrogen atom, was hydrophilic and smooth to subserve the membrane permeability and antiadhesion. The as-prepared MAF-7@4/PES membrane exhibited exceptional salt rejection (98.7% for NaCl) and preferable permeability (1.24 L m−2 h−1 MPa−1), along with a flux decline ratio of 22.4% by employing bovine serum albumin (BSA) as the model foulant. The synergy of MAF-4 and MAF-7 enhanced the photocatalytic activity of membranes probably imputed to the almost perfect lattice match at the junction interface of epitaxial growth, leading to a bactericidal rate of nearly 100%. The main bactericidal mechanism was proved to be massive detected reactive oxygen species (•OH, H 2 O 2 and •O 2 −) generated under visible light, rather than the role of leached metal ions and ligand precursor as recognized. Finally, the significant reduction in flux loss and the inhibition of biofilm formation in dynamic filtration indicated MAF-7@4/PES membrane had the potential for the application of desalination with a prominent antifouling property. [Display omitted] • Flawless bare MOF membranes were synthesized via in-situ growth. • Hydrophilic epitaxial growth availed desalination and photocatalytic performance. • The MOF membranes had remarkable antiadhesive and bactericidal properties. • Substantial ROS were detected, dominating in the bactericidal mechanism. • The biofouling of MOF membranes was effectively mitigated. [ABSTRACT FROM AUTHOR]

• One-step polyphenol deposition strategy was applied to prepare multifunctional MF membranes. • Modified membranes with large pore sizes exhibited >6 log pathogenic reduction. • Metal ions were in-situ captured and reduced by polyphenol-based surface chemistry. • The membrane system showed effective biofouling prevention under gravity filtration. • Improved hydrophilicity and antimicrobial effects promote antibiofouling performance. In remote industrial areas, access to safe drinking water is often hindered by local water contamination and unreliable infrastructure. Hence, energy-effective water treatment and safe storage technology is vital and highly desirable to tackle complex water pollution caused by heavy metals and pathogenic contaminants for boundary circumstances. Here, we originally engineered a multifunctional gravity-driven membrane system to provide a household-level approach to pathogenic disinfection and biofouling prevention. Facile one-step polyphenol deposition strategy was applied on microporous membranes, tailoring the membrane surface with enhanced positive charge, favorable hydrophilicity and metal-binding ability. When applied in gravity-driven filtration of simulated multi-component wastewater containing heavy metals and pathogenic contaminants, the as-prepared membrane achieved >6 log pathogenic reduction. Metal ions could be in-situ captured and stabilized at membrane interface via natural binding and reduction by polyphenol-engineered surface chemistry, endowing ensuing membranes with improved antibacterial activity. By virtue of enhanced membrane surface properties and antimicrobial synergy, such engineered membrane platform showed potent efficacy in biofilm prevention with 97% reduced ATP content and easy permeation recovery (>90%) in cyclic operation. This study is promising for developing low-energy and easy-to-use membrane system to improve contaminated water sources in remote and underdeveloped areas at household level. [ABSTRACT FROM AUTHOR]

• The deposited layers improved the removal of contaminants and membrane permeability. • The micro fine particles enhanced the hydrophilicity of membrane surfaces. • The micro fine particles decreased adhesion free energy between membrane surfaces and foulants. • The micro fine particles influenced on the biofilm structures. Micro fine particles (micro fine powdered activated carbon (MFPAC) or micro fine powdered zeolite (MFPZ)) were deposited on hydrophobic polyvinylidene fluoride (PVDF) membrane to enhance gravity-driven ultrafiltration performances. A distinct flux attenuation and permeate quality difference were observed between pristine and deposited membrne systems. The results indicated that both MFPAC-PVDF and MFPZ-PVDF membranes exhibited a high pure fluxes, a gentle flux downward trend and a high stable permeate flux compared to the pristine PVDF membrane. Additional, compared to the pristine membrane, the deposited membrane systems exhibited a significantly enhanced removal of TOC, NH 4 +-N, and TN (increased by 48%, 93% and 22% for the MFPAC-PVDF membrane, by 18%, 89%, and 20% for MFPZ-PVDF membrane). The improved performance of deposited membranes were attributed to both the changed initial surface properties and the subsequent biofilm characteristics. Owing to the presence of MFPAC and MFPZ filtration layer, the enhanced hydrophilicity due to the introduction of surface –C-O and –OH groups, as well as the decreased free energy of adhesion between membrane surfaces and foulants, impart deposited memrbanes promising potential of permeability improvement and fouling mitigation. Furthermore, the biofilm amounts and compositions of deposited membranes were also significantly influenced, presenting a reduction of accumulated organic compounds by 40 and 50%, repectively, compared to the pristine membrane, contributing to alleviated membrane fouling. The MFPAC could function as a live bacteria incubator, resulting in a higher bacteria bioactivity and enhanced degradation in the biofilm layer. While The MFPZ was in favour of hydrophilic protein cover to form a hydration shell on biofilm surface, helping to prevent the approach of hydrophobic foulants. [ABSTRACT FROM AUTHOR]