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    In the textile industry, a high-efficiency dye removal and low-retention of salt is demanded for recycling wastewater. In this study, polyvinylidene fluoride (PVDF) ultrafiltration membrane was transformed to a negatively charged loose nanofiltration (NF) membrane through UV-grafting of acrylic acid. At the optimal exposure of PVDF membrane in UV light for 5 min, the membrane had a high dye recovery above 99% (Congo red and Eriochrome® Black T) and a low sodium chloride (NaCl) rejection of less than 15% along with pure water flux of 26 L∙m−2∙h−1∙bar−1. Its antifouling and oleophobicity surface properties were verified using fluorescent- bovine serum albumin (BSA) and underwater mineral oil contact angle, respectively. According to the fluorescent microscopic images, the modified membrane had ten times lower adhesion of protein on the surface than the unmodified membrane. The underwater oil contact angle was raised from 110° to 155°. Moreover, the salt rejection followed this sequence: Na2SO4 > MgSO4 > NaCl > MgCl2, which agreed with the typical negatively charged NF membrane. In addition, the physicochemical characterization of membranes was further investigated to understand and link to the membrane performance, such as surface functional group, surface elements analysis, surface roughness/morphology, and surface hydrophilicity. 
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  3. Superhydrophilic zwitterions on the membrane surface have been widely exploited to improve antifouling properties. However, the problematic formation of a <20 nm zwitterionic layer on the hydrophilic surface remains a challenge in wastewater treatment. In this work, we focused on the energy consumption and time control of polymerization and improved the strong hydrophilicity of the modified polyvinylidene difluoride (PVDF) membrane. The sulfobetaine methacrylate (SBMA) monomer was treated with UV-light through polymerization on the PVDF membrane at a variable time interval of 30 to 300 s to grow a poly-SBMA (PSBMA) chain and improve the membrane hydrophilicity. We examined the physiochemical properties of as-prepared PVDF and PVDF–PSBMAx using numeric analytical tools. Then, the zwitterionic polymer with controlled performance was grafted onto the SBMA through UV-light treatment to improve its antifouling properties. The PVDF–PSBMA120s modified membrane exhibited a greater flux rate and indicated bovine serum albumin (BSA) rejection performance. PVDF–PSBMA120s and unmodified PVDF membranes were examined for their antifouling performance using up to three cycles dynamic test using BSA as foulant. The PVDF-modified PSBMA polymer improved the antifouling properties in this experiment. Overall, the resulting membrane demonstrated an enhancement in the hydrophilicity and permeability of the membrane and simultaneously augmented its antifouling properties. 
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  4. Nanofiltration membranes have evolved as a promising solution to tackle the clean water scarcity and wastewater treatment processes with their low energy requirement and environment friendly operating conditions. Thin film composite nanofiltration membranes with high permeability, and excellent antifouling and antibacterial properties are important component for wastewater treatment and clean drinking water production units. In the scope of this study, thin film composite nanofiltration membranes were fabricated using polyacrylonitrile (PAN) support and fast second interfacial polymerization modification methods by grafting polyethylene amine and zwitterionic sulfobutane methacrylate moieties. Chemical and physical alteration in structure of the membranes were characterized using methods like ATR-FTIR spectroscopy, XPS analysis, FESEM and AFM imaging. The effects of second interfacial polymerization to incorporate polyamide layer and ‘ion pair’ characteristics, in terms of water contact angle and surface charge analysis was investigated in correlation with nanofiltration performance. Furthermore, the membrane characteristics in terms of antifouling properties were evaluated using model protein foulants like bovine serum albumin and lysozyme. Antibacterial properties of the modified membranes were investigated using E. coli as model biofoulant. Overall, the effect of second interfacial polymerization without affecting the selectivity layer of nanofiltration membrane for their potential large-scale application was investigated in detail. 
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