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Although hydrophilic modification of the membrane surface is widely adopted, polymeric membranes still suffer from irreversible fouling caused by hydrophilic components in surface water. Here, an ultrathin hydrogel layer (40 nm) with hydrophilic-hydrophobic textures was in situ grown onto the polysulfone ultrafiltration membrane surface using an organic-radical-initiated interfacial polymerization technique. The interfacial polymerization of hydrophilic and hydrophobic monomers ensured the molecular-scale distribution of hydrophilic and hydrophobic nanodomains on the membrane surface. These nanodomains, with their molecular lengths, facilitated dynamic repulsion interactions between the uniformly textured surface and foulant components with different degrees of hydrophilicity. Chemical force characterization confirmed that the adhesion force between the hydrophilic-hydrophobic textured membrane surface and foulants (dodecane, bovine serum albumin, and humic acid) was greatly reduced. Dynamic filtration experiments showed that a hydrophilic-hydrophobic textured membrane always possessed the largest water flux and the best antifouling performance. Furthermore, the foulant coverage ratio on the membrane surface was first evaluated by measuring changes in surface streaming potentials, which demonstrated a 69% reduction in the amount of foulant adhering to the hydrophilic-hydrophobic textured membrane surface. Therefore, the construction of hydrophilic-hydrophobic nanodomains on the membrane surface provides a promising strategy for alleviating membrane fouling caused by both hydrophobic and hydrophilic components during ultralow pressurized ultrafiltration processes.

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 Ca 2+ were chosen as the representative cations, and humic acid (HA) was chosen as the membrane foulants. The results demonstrated Ca 2+ promoted the formation of reversible fouling, meanwhile higher removal efficiency of HA could also be achieved with the assistance of filtration cake containing HA + Ca 2+ . 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 Ca 2+ 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 Ca 2+ and K + also contributed to the different structures of foulant layers formed by HA + Ca 2+ and HA + K + . Given the abundance of K + and Ca 2+ in natural water, results of this study can provide valuable advice for practical membrane filtration process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

The novel H 2 O 2 -MnO 2 system was developed to achieve highly efficient membrane cleaning for both fouled PVDF and PES membranes in this study. Compared with conventional chemical cleaning process in which the whole membrane module had to be soaked in highly concentrated solution of chemical reagent for long period of time, the H 2 O 2 -MnO 2 cleaning process conducting for only 5 min in 0.5 wt% H 2 O 2 solution could achieve more than 95% recovery of permeate flux and almost total removal of the irreversible foulants. More importantly, the permeate flux and filtration efficiency of the membrane could be still kept stable after 6 runs of consecutive fouling and cleaning. Based on the systematic microscopic analyses, Electron Spin Resonance (ESR), Fourier Transform Infrared Spectroscopy (FTIR), as well as the quenching experiments with different free radical scavengers, the outstanding performance of H 2 O 2 -MnO 2 system was attributed to the generation of both free radicals and abundant oxygen simultaneously, leading to the physico-chemical membrane cleaning. Conclusively, the newly developed H 2 O 2 -MnO 2 system demonstrated noteworthy advantages on efficient membrane cleaning, and exhibited highly potential for the wide application in practical water treatment process., (Copyright © 2019. Published by Elsevier Ltd.)

A simple and efficient route was used to prepare an amphiphilic copolymer (poly(propylene glycol)-co-poly(ethylene glycol)-co-poly(propylene glycol)) (PPG-co-PEG-co-PPG) by one-pot polymerization reaction. This copolymer was used as the hydrophilic additive in preparation of poly(vinylidene fluoride) (PVDF) ultrafiltration membranes via immersion-precipitation process. Surface characteristics of the membranes were confirmed by contact angle measurements, zeta potential, attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. During filtration experiments, the modified membranes showed better permeation and antifouling performances compared to PVDF membranes with bovine serum albumin, sodium alginate and yeast. After hydraulic stirring cleaning with deionized water, water flux recovery and rejection ratio of the modified membranes were higher than those of pristine PVDF membrane, and the flux recovery ratio was maximized at 94.29%. It was suggested that PPG-co-PEG-co-PPG copolymer was anchored in the PVDF membrane through the two hydrophobic ends of PPG blocks, while the hydrophilic intermediate of the PEG block segregated onto the membrane or pore surface during the membrane preparation process. The synthesized method of amphiphilic PPG-co-PEG-co-PPG copolymer paved a novel way to solve the problems of less compatibility between the copolymer and membrane matrix and instability with water molecules in the ultrafiltration process.

• 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]

A novel hydrophilic nanocomposite additive (PVP-g-MMT), coupling of hydrophilic modifier, self-dispersant,and pore-formingagent (porogen), was synthesized by the surface modification of montmorillonite(MMT) with N-vinylpyrrolidone (NVP) via “graftingfrom” polymerization in the presence of H2O2–NH3·H2O as the initiator,and then the nanocomposite membrane of poly(vinylidene fluoride) (PVDF)and PVP-g-MMT was fabricated by wet phase inversiononto clean glass plates. The existence and dispersion of PVP-g-MMT had a great role on structures, morphologies, surfacecomposition, and chemistry of the as-prepared nanocomposite membranesconfirmed by varieties of spectroscopic and microscopic characterizationtechniques, all of which were the correlated functions of PVP-g-MMT content in casting solution. By using the dead-endfiltration of protein aqueous solution, the performance of the membranewas evaluated. It was seen that all of the nanocomposite membranesshowed obvious improvement of water flux and proper BSA rejectionratio, compared to the control PVDF membrane. Meanwhile, dynamic BSAfouling resistance and flux recovery properties were also greatlyenhanced due to the changes of surface hydrophilicity and morphologies.All the experimental results indicated that the as-prepared PVDF nanocompositemembranes showed better separation performances than the control PVDFmembrane. Hopefully, the demonstrated method of hydrophilic nanocompositeadditive synthesis would be applied for commonly hydroxyl group-containinginorganic nanoparticles, which was favorable to fabricate hydrophilicnanoparticle-enhanced polymer membranes for water treatment. [ABSTRACT FROM AUTHOR]

A novel polysulfone hybrid ultrafiltration membrane was developed by blending hydrophilic poly[poly(ethylene glycol) methyl ether methacrylate] [P(PEGMA)] grafted mesoporous SBA‐15 [SBA‐g‐P(PEGMA)] as filler. The hydrophilic SBA‐g‐P(PEGMA) fillers were synthesized via surface‐initiated atom transfer radical polymerization. The effects of the SBA‐g‐P(PEGMA) fillers on the prepared hybrid membranes were systematically investigated. Compared with pristine SBA‐15 fillers, SBA‐g‐P(PEGMA) fillers contributed to higher hydrophilicity and a more developed pore structure in the hybrid membranes. Specifically, SBA‐15 grafted with a moderate P(PEGMA) molecular weight could better preserve the valid open‐ended filler pore structure in the membrane matrix, thus facilitating membrane permeability. The pure water flux of the as‐prepared polysulfone (PSF)/SBA‐g‐P(PEGMA) membrane was three times that of the PSF/SBA‐15 membrane (271.7 L m−2 h−1 vs. 88.2 L m−2 h−1) with similar membrane selectivity. Moreover, the PSF/SBA‐g‐P(PEGMA) membranes showed improved antifouling property. This work paves the way for developing high‐performance hybrid membranes by blending of hydrophilic polymer‐functionalized mesoporous fillers in the future. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47353. [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]

Abstract Cleaning effect and mechanism of peroxymonosulfate (PMS)-based oxidation technology were systematically studied in metal oxide-coated ceramic membrane (CM) cleaning process. Metal oxides (MnO 2 , Fe 2 O 3 , Co 3 O 4 , CuO and Mn 3 O 4) were evenly coated on CM surfaces via silane modification and dip-coating followed by calcination. The performance of prepared CMs was investigated by filtrating Alcian Blue 8GX dye. Flux decline extents of different metal oxide-coated CMs were greatly influenced by metal oxide hydrophilicity, and their rejection rates for dye increased by 10.2–47.6%, probably due to the enhanced adsorption or electrostatic repulsion of pollutants. PMS had better cleaning effects on metal oxide-coated CMs than virgin CM (64.0%) following the order: MnO 2 -coated CM (75.3%)> Co 3 O 4 -coated CM (73.8%)> Fe 2 O 3 -coated CM (71.2%)> Mn 3 O 4 -coated CM (70.5%)> CuO-coated CM (70.2%). This was well consistent with order of dye degradation efficiency oxidized by PMS activated with those metal oxides, indicating that degradation efficiency of foulant largely determined cleaning effect. The mechanisms were proposed and then verified that radical (O 2 •–), and non-radical (1O 2 and PMS direct oxidation) pathways simultaneously occurred, and metal oxides coated on CMs surfaces mainly promoted non-radical oxidation process. This study provides insight to better utilize metal oxides activated PMS oxidation technology for membrane cleaning and improve its cleaning efficiency for dye wastewater treatment. Graphical abstract fx1 Highlights • Metal oxide-coated CM was made via silane modification, dip-coating and calcination. • Membrane flux recovery ratios increased after cleaned with PMS. • Degradation efficiency of dye by PMS mainly determined membrane cleaning effect. • Radical and non-radical oxidation mainly accounted for membrane foulant degradation. [ABSTRACT FROM AUTHOR]

The operational issues of low-pressure ultrafiltration (UF) membrane are associated with its long-term membrane fouling caused by organic and inorganic matters, especially in treating shale gas wastewater (SGW) with complex water compositions. Herein, the effect of ferrate (Fe(VI)) pretreatment on UF membrane fouling and water quality in treating SGW was systematically investigated. Fe(VI) pretreatment significantly mitigated membrane fouling and slightly improved the effluent quality. The hydraulically irreversible fouling index and the total fouling index decreased by 69%–87% and 58%–84%, respectively. The mechanism of membrane fouling mitigation was comprehensively analyzed by the classical pore blocking model, correlation analysis between membrane fouling index and water quality, and the extended Derjaguin-Landau-Verwey-Overbeek theory. The synergistic mechanisms of membrane fouling mitigation were as follows: (i) Macromolecular organic matters (high molecular weight humics and biopolymers) which would block the membrane pores were oxidized into low fractions organics and removed by Fe(VI); (ii) Fe(VI) pretreatment improved interaction free energy of cohesion of foulants-foulants making foulants more hydrophilic and stable, and increased interaction free energy of adhesion of membrane-foulants making it more difficult for foulants to deposit on the membrane surface. Fe(VI) pretreatment had huge potential in alleviating membrane fouling in treating SGW and other complex wastewater. [Display omitted] • Fe(VI) is combined with UF to treat shale gas wastewater for the first time. • Fe(VI) notably decreases TFI and HIFI by 58%–84% and 69%–87%, respectively. • Biopolymers and high MW humics are the main foulants causing membrane fouling. • XDLVO theory confirms fouling mechanism by analyzing adhesion/cohesion energies. [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]