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[Display omitted] • Antifouling property of the membrane was improved by UV-initiated grafting. • Surface charge was regulated by electrostatic adsorption. • The membrane showed excellent antifouling properties when filtrating various foulant solutions. • The membrane was very stable due to the covalent bonding. In this study, positively charged monomers were grafted onto negatively charged membranes via UV radiation to improve the antifouling/antibiofouling properties of the polymeric membrane and the stability of the modification layer. The surface properties, morphologies, antifouling and antibiofouling properties, and stability of the modified membranes were systematically characterized. Results indicated that the introduction of [2-(methacryloyloxy) ethyl] trimethylammonium chloride (MTAC) monomers onto polyethersulfone (PES)/sulfonated polyethersulfone (SPES) membranes effectively increased the surface hydrophilicity. Meanwhile, the surfaces were neutralized with ~0 mV zeta potential in pH 3–10. Moreover, the formation of a polyampholytic copolymer and the antibacterial ability of MTAC considerably improved the antibiofouling properties of the modified membranes. The MTAC-grafted PES/SPES membranes showed excellent antifouling/antibiofouling properties during the treatment of various types of wastewater, including bovine serum albumin solution, oil/water emulsion, and bacterial suspension. Therefore, this study provides a simple and effective method of constructing stable and antifouling membranes for sustainable water treatment. [ABSTRACT FROM AUTHOR]

In this study, a simple approach was proposed to incorporate zwitterionic copolymers into polymer membranes via electrostatic adsorption to reduce organic fouling and biofouling. Zwitterionic copolymers carrying positive charges were successfully synthesized from [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA) and [2-(methacryloyloxy) ethyl] trimethylammonium chloride (MTAC) via radical polymerization. Quartz crystal microbalance (QCM) measurements were conducted to identify the optimum copolymer with suitable monomer ratio for surface coating. The copolymer with an SBMA to MTAC ratio of 7:3, and 1000 ppm polymer concentration showed the highest adsorption. A negatively charged membrane was modified with this zwitterionic copolymer by the dip-coating method, which was finished in 1 min. The surface properties and antifouling properties (i.e. anti-organic fouling and anti-biofouling) of the membranes were characterized. Moreover, the modified membrane was stable in various chemical solutions. Results indicated that improved anti-organic fouling and anti-biofouling properties was attributed to improved hydrophilicity and reduced negative charge. The zwitterionic coating layer was stable after treatment with various solutions (e.g., 70% ethanol, 0.01 M sodium dodecyl sulfate (SDS), 0.1 M sodium chloride (NaCl), and a pH11 aqueous solution) for 6 h. This study provides a simple, stable method of modifying negatively charged membrane to improve antifouling properties, which is of great importance in biomedicine. [ABSTRACT FROM AUTHOR]

Effect of the supporting layer structures on antifouling properties of forward osmosis (FO) membranes in active-layer-facing-draw-solution (AL-DS) mode was investigated through a series of polyketone (PK) membranes prepared by controlling the concentration of the polymer casting solution, initial casting height, and solvent system. A double-skinned FO membrane was prepared by interfacial polymerization on the bottom surface of the PK membrane. The surface pore sizes, bulk porosities, water permeability and alginic acid sodium salt rejection properties of the prepared PK membranes were determined, and the surface roughness, membrane thickness, pure water permeability, salt permeability and FO performance of the PK-based FO membranes were characterized. The alginic acid sodium salt was used to evaluate the antifouling properties of the FO membranes in AL-DS mode. The effect of surface roughness (or surface pore size), membrane thickness, and structural parameter (S value) on the membrane fouling was investigated. The results indicate that decreasing both the surface pore size of the supporting layer and the membrane thickness effectively improves the membrane performance; that is, the membrane possesses both enhanced antifouling properties and water permeability. This work provides firm guidelines for the design of proper supporting layer structures for FO membranes with high performance in AL-DS (or pressure retarded osmosis, PRO) mode. [ABSTRACT FROM AUTHOR]

To improve the antifouling properties of polymer membranes, a novel phosphate-based zwitterionic polymer (methacryloyloxyethylphosphorylcholine- co -poly(propylene glycol) methacrylate, i.e., MPC-PPGMA) is introduced into the polyvinyl chloride (PVC) membrane matrix. The solubility of this zwitterionic copolymer in common organic solvents and the compatibility between this copolymer and PVC are studied. A series of PVC blend membranes are prepared via non-solvent induced phase separation based on the good compatibility of the copolymer with PVC. Surface chemical compositions, wettability and porous structures of the membranes are characterized. Fluorescence-labeled proteins static adsorption and organic foulant filtration are conducted to evaluate the fouling resistance of the blend membranes. Antibiofouling properties of the membranes are also confirmed by the immersing method. Doping MPC-PPGMA in the casting solution can significantly improve the surface hydrophilicity and antifouling properties of the PVC blend membranes due to the strong hydration ability of the zwitterionic segments. The blend membranes show excellent and stable resistance to both organic fouling and biofouling. Overall, the novel zwitterionic copolymer MPC-PPGMA is a promising candidate to develop antifouling blend membranes due to its high effectiveness and long-term stability in the membranes. [ABSTRACT FROM AUTHOR]

Two new amphiphilic copolymers poly(methyl methacrylate- graft -poly(ethylene glycol) methacrylate) (PMMA -g- PEG) are synthesized and blended into polyvinyl chloride (PVC) to prepare membranes in different coagulation media (water and ethanol) via the non-solvent induced phase separation method. The prepared membranes are characterized by X-ray photoelectron spectroscopy, proton nuclear magnetic resonance, scanning electron microscopy, atomic force microscopy and water contact angle measurement. Their separation performance and fouling resistance (by protein adsorption and foulant filtration) are also compared. It is found that the membrane hydrophilicity is significantly increased by blending amphiphilic copolymer due to the introduction of hydrophilic poly(ethylene glycol) (PEG) segments of the copolymer. The membranes formed in water have more desirable structures (i.e., smoother surfaces and higher porosity) and better performance (i.e., higher permeability and rejection to bovine serum albumin) compared with those formed in ethanol. The amphiphilic copolymer blended membranes formed in the water coagulation bath exhibit excellent antifouling properties, in particular, showing ~100% fouling reversibility. Therefore, blending amphiphilic copolymers and selecting water as the coagulation media can be effective strategies to develop high performance antifouling membranes. [ABSTRACT FROM AUTHOR]

Polyampholytes, particularly zwitterionic polymers, are commonly used for the surface modification of membranes. This helps to improve the antifouling properties, anti-adhesion properties, and biocompatibility of the membranes. Surface coating and grafting are common surface modification methods; however, these methods lead to pore blocking and stability problems because polyampholytes exist only on the membrane surface. We propose a strategy to fabricate membranes with well-dispersed polyampholytic copolymers via a composite coagulation process. Negatively charged membranes are fabricated in a coagulation bath containing a polyampholytic copolymer. Thus, both membrane preparation and modification via electrostatic adsorption can be achieved via a one-step process. Moreover, the polyampholytic copolymer is expected to be dispersed within the membrane matrix as well as on the membrane surface. The chemical compositions within the membrane were analyzed using X-ray photoelectron spectroscopy combined with argon beam etching technique. The results indicated that the polyampholytic copolymer was well dispersed within the membrane matrix fabricated via this composite coagulation process, whereas only a thin coating layer was formed on the membrane surface via the normal surface coating method. The newly fabricated membrane exhibited greater water flux, better antifouling properties, and higher stability than pristine and surface-coated membranes. This paper presents a method to prepare high-performance membranes with polyampholytic copolymers. Image 1 • Hydrophilic membrane with well-dispersed polyampholytic copolymer was successfully fabricated. • The membrane was prepared via an in-situ composite coagulation process. • Well-dispersed chemical compositions were confirmed by XPS combined with argon beam etching technique. • Composite coagulation process provides a novel strategy for antifouling and high-permeability membrane. [ABSTRACT FROM AUTHOR]

In this study, a stable zwitterionic layer on the surface of a membrane was developed to improve antifouling properties of the membrane, whereby negatively-charged membranes were modified by a positively-charged zwitterionic copolymer via surface adsorption and a cross-linking reaction. Here, 2-methacryloyloxyethyl phosphorylcholine and 2-aminoethyl methacrylate hydrochloride copolymer (P(MPC- co -AEMA)) was used as a model zwitterionic copolymer that can be adsorbed onto negatively-charged surfaces, and cross-linked by glutaraldehyde. The surface chemical compositions, morphology, hydrophilicity, charge, and antifouling properties of the membranes were characterized. Furthermore, the stability of the coating layer was evaluated. The results indicated that the surface hydrophilicity and antifouling properties of the membrane were clearly improved after surface modification. In addition, the stability of the coating layer was significantly increased after cross-linking compared to that after only surface adsorption. This is likely due to the cross-linking of the interpenetrating polymer networks inside the porous structure on the surface. Our findings provide a simple and effective method for surface modification via surface adsorption for use in practical applications. • P(MPC- co -AEMA) was immobilized on surface via adsorption and cross-linking. • The membrane showed improved the antifouling property. • The stability of P(MPC-co-AEMA) was increased after cross-linking. [ABSTRACT FROM AUTHOR]

• A dual-functional ultrafiltration membrane containing quaternary ammonium and zwitterionic polymers was prepared. • The antifouling and antibacterial behavior of the membrane was studied. • The membrane showed the improved organic-/bio fouling resistance. • The membrane showed high-efficiency broad-spectrum antibacterial performance. To overcome the organic-/bio- fouling of the membrane, a dual-functional ultrafiltration membrane containing quaternary ammonium and zwitterionic polymers via quaternization and surface radical polymerization was designed, and its antifouling and antibacterial behavior was studied. In this work, poly(vinylidene fluoride)/poly(methyl methacrylate- co -dimethylamino-2-ethyl methacrylate) (PVDF/P(MMA- co -DMAEMA)) blend membrane was quaternized by p -chloromethyl styrene (p -CMS), and the double bonds were introduced onto the membrane surface, which further participated in the polymerization of zwitterionic monomers on the membrane surface. The results indicated that the resultant membrane exhibited obviously improved hydrophilicity and weak positive charge (isoelectric point, 7.49). The membrane presented higher flux recovery ratio and lower protein adhesion compared with the pure PVDF membrane. Meanwhile, the membrane showed high-efficiency broad-spectrum antibacterial performance, that is, the bacteria killing efficiency of S. aureus and E. coli reached 98.2% and 97.0%, respectively. Moreover, the membrane effectively inhibited bacterial adhesion, which is important for the long-term antibacterial properties of membrane. This antifouling and antibacterial PVDF membrane may have potential in the long-term filtration process, especially when dealing with microbiologically contaminated water. [ABSTRACT FROM AUTHOR]

To improve the permeability and antifouling properties of polyvinyl chloride (PVC) ultrafiltration (UF) membrane, amphiphilic sulfonated polysulfone (SPSF) was introduced into PVC matrix. Three types of PVC/SPSF blend membranes containing different SPSF with the sulfonation degree (SD) of 20%, 30%, and 50% were fabricated by non-solvent induced phase separation (NIPS) process. The excellent compatibility between PVC and SPSF was confirmed by differential scanning calorimetry (DSC). Surface chemical compositions, morphology, roughness, charge, hydrophilicity, permeability and antifouling properties of the pristine PVC membrane and the PVC/SPSF blend membranes were systematically compared and characterized. Due to the improved hydrophilicity and endowed negative charge, the blend membrane showed high water permeability (i.e. 880 L m−2h−1 bar−1), high bovine serum albumin (BSA) rejection (i.e. 95.7%), and high flux recovery ratio (i.e. 96%), which outperformed ever reported and commercialized PVC membranes. Furthermore, the permeability and rejection properties of PVC/SPSF UF membranes were maintained after soaking in acidic and alkaline solutions for 30 days, indicating their outstanding acid and alkali tolerance. Therefore, SPSF was expected as a potential versatile modifier for fabricating high performance UF membranes. [ABSTRACT FROM AUTHOR]