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Two monomers, positively charged N,N‐dimethylaminoethyl methacrylate (DMAEMA) and negatively charged monomer sodium vinylsulfonate (VSA), were employed to generate a zwitterionic copolymer layer on the surface of PES/SPSf blend membrane via UV‐light grafting. The effect of monomer concentration and irradiation time on the properties of the modified membranes was studied. Results showed that the degree of grafting (DG) accelerated with the increase in monomer concentration and irradiation time. The zeta potential of the zwitterionic membrane was tailored from negative (−21.4 mV) to positive charge (+30.8 mV) by varying the concentration DMAEMA monomer and irradiation time. Optimized membrane fabrication conditions were 15 g L−1 of DMAEMA and 10 min irradiation time (Mc15). The molecular weight cut‐off of Mc15 was calculated to be 40 kDa, while the zeta potential was found to be +8.56 mV (pH = 7). Mc15 showed excellent rejection rates for both positively and negatively charged dyes. In contrast Mc15 maintained low rejection rates for Na2SO4 (<10%) and high dye/salt selective separation performance (retention rates for basic blue 26 and Na2SO4 were 97 and 6.5%) over long continuous operation (50 h). In summary, our study provides tailoring implementation strategies to enhance dye/salt selective separation of tight ultrafiltration membranes. [ABSTRACT FROM AUTHOR]

To balance the permeability-selectivity trade-off effect of the polyamide nanofiltration membrane, interfacial polymerization regulation strategy is widely used to optimize the physicochemical structure of the polyamide film. In the present work, the compound additives of phytic acid and ferric chloride were added into the aqueous phase to regulate the interfacial polymerization process. On the one hand, a lot of piperazine monomers will be adsorbed around the phytic acid molecules due to the electrostatic interaction between phosphoric acid groups and amino groups. Meanwhile, the phytic acid molecules and ferric ions can form a complex in the piperazine solution, which results in a low diffusion rate of the other piperazine monomers without adsorbed on the phytic acid and ferric chloride complex due to steric hindrance. The synergistic effect of electrostatic interaction and steric hindrance leads to the optimized nanofiltration membrane with a thinner and looser polyamide structure. The best-performing nanofiltration membrane exhibits an approximately four-fold water permeance (28.4 L m−2 h−1 bar−1) compared with the controlled M0 nanofiltration membrane (6.5 L m−2 h−1 bar−1) without obviously sacrificing the Na 2 SO 4 rejection (96.9 %). This simple interfacial polymerization regulation strategy provides a novel insight for the preparation of high-performance NF membrane. Phytic acid&FeCl3 compound additives-regulated interfacial polymerization. [Display omitted] • Phytic acid and ferric chloride were employed to regulate interfacial polymerization. • The compound additives can inhibit piperazine monomer diffusion. • The nanofiltration membrane shows a thin and loose polyamide layer. • The optimized membrane exhibits high water permeance and Na 2 SO 4 rejection. [ABSTRACT FROM AUTHOR]

The aqueous dispersion of graphene oxide (GO) was employed as additive to fabricate antifouling and antibacterial polyethersulfone (PES)/sulfonated polysulfone (SPSf)/GO mixed matrix membranes (MMMs) by the non-solvent induced phase separation (NIPS). The effect of different amounts of GO on the morphology and performance of MMMs were studied. The results showed that the casting solution exhibited an increasing trend in viscosity with increment in GO concentration (from 0 to 0.016 wt%) owing to the hydrogen bonding (H-bonding) interaction among GO, H 2 O and SPSf. Raman and molecular dynamic (MD) simulations analyses confirmed that there existed H-bonding interaction among SPSf, GO and H 2 O. Specifically, the agglomeration of GO was inhibited and stable homogeneous casting solution was obtained. Meanwhile, the H-bonding interaction also played a key role in the MMMs structure and improved properties. It was found that GO nanosheets were uniformly embedded to form many cellular-like voids in the asymmetric PES/SPSf/GO MMMs with a sponge-like structure. The pure water flux of the MMMs with a very low GO content of 0.012 wt% was up to 816.9 L/m2h and the rejection of bovine serum albumin (BSA) was more than 99.2% under a pressure of 0.1 MPa. Additionally, the mechanical properties of MMMs was also improved with the increase of GO content. Importantly, the MMMs displayed excellent antifouling and antibacterial performance. A high fouling recovery (94.2%) and antibacterial rate (90.0%) against Escherichia coli (E. coli) obtained were attributed to improved hydrophilicity, enhanced negative charge and GO nano-size effect. In summary, our study provides a simple approach to tailor MMMs with the enhancement of permeation, antifouling and antibacterial properties at a very low content of GO. [ABSTRACT FROM AUTHOR]

Abstract Macrovoid-free polyethersulfone/sulfonated polysulfone (PES/SPSf) ultrafiltration (UF) membranes containing oxidized multi-walled carbon nanotubes (O-MWCNTs) were fabricated via a non-solvent induced phase separation method using H 2 O and PEG 20 kDa as a non-solvent additives. The results show that the fully sponge-like morphology of the PES/SPSf membranes could be achieved as the content of O-MWCNTs in the casting solutions was increased, due to the formation of strong hydrogen bonds between SPSf, H 2 O, PEG 20 kDa and O-MWCNTs. Such morphology provided excellent mechanical strength properties with the highest of 4.02 ± 0.08 MPa obtained for the membrane containing 0.1 wt% O-MWCNTs. Microscopic analysis revealed homogenous distribution of O-MWCNTs in the PES/SPSf mixed-matrix membranes. Moreover, pure water flux initially increased from 598 to 713 L/m2 h followed by a decline to 590, 560, 553 and 578 L/m2 h as the content of O-MWCNTs was increased from 0 wt% to 0.005, 0.01, 0.03, 0.05 and 0.1 wt%, respectively. A rejection of > 99.9% for bovine serum albumin (BSA) was achieved by membranes containing 0.05 wt% O-MWCNTs. The water flux recovery ratio of membranes containing O-MWCNTs was found to be higher (> 90%) than that of pristine PES/SPSf (75%) even after the second fouling and cleaning stages. Furthermore, it was found that only 85% of E. coli bacteria were killed by pristine PES/SPSf, compared to 99% by PES/SPSf membrane containing the highest O-MWCNT loading. The fabricated flat-sheet membranes display attractive features for use as UF membranes in the pre-treatment stage of water treatment. Highlights • PES/SPSf/O-MWCNT UF membranes produced via non-solvent induced phase separation. • H-bonding between SPSf, PEG and O-MWCNTs led to strong interfacial interactions. • Macrovoids completely suppressed in the presence of O-MWCNTs. • Uniform distribution of O-MWCNTs in MMMs led to enhanced mechanical strength. • O-MWCNTs in PES/SPSf matrix enhanced its antifouling and antibacterial properties. [ABSTRACT FROM AUTHOR]

Polyethersulfone (PES)/sulfonated polysulfone (SPSf)/TiO 2 mixed matrix membranes (MMMs) were fabricated using non-solvent induced phase inversion (NIPS) technique for oil-in-water emulsion separation. The performance of the membrane was tailored by tuning the morphology through the addition of TiO 2 nanoparticles (NPs) (0.05–0.15 wt %) and by varying the polymer concentrations (18–28 wt). The optimum concentration of TiO 2 was found to be 0.075 wt %), where the water permeability and solute rejection trade-off neutralised. In this membrane the polymer concentration was 22 wt %. In terms of performance, the membrane had pure water permeance of 555.2 LMH bar-1 , 90% oil rejection and 89.5% permeance recovery rate (PRR) at an initial concentration of 900 ppm. The surface porosity was 13.1%. Molecular dynamic (MD) simulations and spectroscopic analyses proved that the NPs formed hydrogen bonds with the polymer chains. This resulted in two effects with ripple impacts: a) slowed movement of polymer chains or slow solid-liquid phase separation, leading to the MMMs with the thicker top layer and high surface porosity, and b) stable and even distribution of NPs within the framework as observed with elemental mapping. Accordingly, the MMMs obtained desired asymmetric features corresponded to their overall superior performance. In conclusion, small concentrations of TiO 2 NPs can be used to successfully modify morphology and separation performance of membranes used for oil-in-water emulsion filtration. Image 1 • Hydrogen bonding between TiO 2 NPs and polymer chains promoted membrane formation. • TiO 2 NPs blended in small dosages impacted the membrane morphology and properties. • Hydrophilicity and surface morphology determined oil-in-water emulsion separation. [ABSTRACT FROM AUTHOR]

Sulfonated polysulfone (SPSf) and water as additives were employed to tailor the morphology and performance of polyethersulfone (PES) ultrafiltration (UF) membrane using non-solvent induced phase separation (NIPS) for the purposes of dye and salt selective separation. Results showed that the viscosity of PES/SPSf/DMAc casting solution (polymer concentration 28 wt%) sharply increased from 1900 to 2650 mPa s with the addition of H 2 O (7 wt%) owning to the formation of pregelation. It was also revealed that PES polymer chains solidified and shrank faster than SPSf polymer chains during NIPS process, leading to –SO 3 - groups of SPSf to cover the surface of PES/SPSf polymer matrix. The resultant PES/SPSf UF membrane possessed superior pure water permeance (110.4 L/m2 h bar) compared with the pristine PES membrane (0.13 L/m2 h bar). The improvement in water permeance was ascribed to the synergy of SPSf and water, which enhanced the surface pore size, top surface porosity and hydrophilicity of PES membrane. Meanwhile, molecular dynamic (MD) simulations revealed that H 2 O can weaken the interaction between PES and SPSf chains and slow down the mutual diffusion in favour of the movement and ordered arrangement of chains. Additionally, the rejection of Evans blue (EB), Coomassie brilliant blue (BBR), Congo red (CR) and Acid fuchsin (AF) dye solution (0.1 g/L) by PES/SPSf membrane were 99.0%, 99.9%, 99.2% and 90.1%, respectively, whereas Na 2 SO 4 rejection was less than 5%. In sum, this work supplies a simple avenue to tailor PES membrane with enhanced permeance as well as separation performance of dye/salt mixture. Image 1 • The synergistic effect between SPSf and H 2 O was proposed for the first time. • MD simulation verifies H 2 O can weaken the interaction between PES and SPSf chains. • PES shows a faster curing rate than SPSf which induces –SO 3 - covering the matrix. • Synergistic effect of SPSf & H 2 O raised pore size & hydrophilicity of PES membrane. • PES/SPSf membrane shows high permeability and selectivity for dye/salt separation. [ABSTRACT FROM AUTHOR]

Polysulfone (PSf)-grafted graphene oxide (GO) nanosheets (GO- g -PSf) were synthesized via a nucleophilic substitution reaction between hydroxyl groups of GO and chloromethyl groups of chloromethylated polysulfone (CMPSf). GO- g -PSf dispersion in N-methyl pyrrolidone (NMP) was employed to fabricate GO- g -PSf composite membranes for dye separation by a vacuum filtration self-assembly method using polyamide (PA) composite membranes as the supports. The chemical structure and morphology of GO- g -PSf nanosheets were characterized by XRD, FTIR, Raman, XPS and TEM analyses. The morphology and filtration performance of membranes with various GO and GO- g -PSf depositions were investigated. The GO- g -PSf composite membrane with a deposition rate of 31.8 μg cm−2 exhibited a much higher pure water flux (88.0 L m−2 h−1 (LMH)) than pure GO composite membrane (12.8 LMH) at 2 bar owing to the enlarged interlayer spacing between the GO- g -PSf nanosheets. Simultaneously, the rejection rate of the GO- g -PSf composite membrane reached 90.3% for acid black 1 (AB), 99.5% for Congo red (CR) and 99.8% for methyl blue (MB) dyes under a cross-flow process at 2 bar. Moreover, the water permeance of the GO- g -PSf composite membrane remained at 25.9 LMH bar−1 after 60 h of operation for CR separation. Notably, the GO- g -PSf composite membrane also exhibited improved structural stability after 2 h of ultrasonic irradiation due to the physical entanglement of PSf chains. This study provides a simple approach to enhancing the permeability and structural stability of GO-based membranes used for dye separation. Image 1 • GO- g -PSf was synthesized via nucleophilic substitution between GO and CMPSf. • GO- g -PSf membranes were prepared via vacuum filtration using PA as support. • The pure water flux of GO- g -PSf membrane reached 88.0 LMH at 2 bar. • GO- g -PSf membrane exhibited a higher permeance than GO membrane in dye rejection. • GO- g -PSf membrane showed excellent stability due to the entanglement of PSf chains. [ABSTRACT FROM AUTHOR]

Polyethersulphone (PES)/sulfonated polysulphone (SPSf) blend ultrafiltration membrane was prepared via non-solvent induced gelation phase separation (NIGPS) using H 2 O as the non-solvent additive in the casting solution with N,N-dimethylacetamide (DMAc) as the solvent. An ultrasonic technique was employed to monitor membrane formation so as to provide the quantitative information during the phase separation. The effect of H 2 O concentration in the PES/SPSf/DMAc casting system on the membrane structure and properties was investigated. Results indicated that the viscosity of the casting solution increased with the increase of H 2 O content from 3 wt% to 9 wt% owing to the strong interaction between H 2 O molecules and the –SO 3 - group of SPSf chains, finally leading to the gelation of the system. Simultaneously, the microporous structure of the resultant membranes changed gradually into sponge-like structure from macrovoids with the increase of H 2 O content in the casting solution. It was related to the changes of the phase separation behavior from instantaneous demixing to delay demixing. Specifically, the approaching ratio could be used to predict the behaviors of the instantaneous and delay demixings. Moreover, the pure water flux of PES/SPSf blend membrane obtained under the conditions of polymer concentration 18 wt%, PES: SPSf = 84:16 wt/wt and 9 wt% H 2 O in the casting solution was up to 858 L/m 2 h. The bovine serum albumin (BSA) rejection was 90.5%. [ABSTRACT FROM AUTHOR]

[Display omitted] • A polyethersulfone/sulfonated polysulfone loose NF membrane was fabricated. • The membrane exhibited high flux and enhanced selectivity of PPCPs/minerals. • The removal of ionic PPCPs is mainly dominated by charge exclusion and adsorption. • Non-ionizable PPCPs are removed by adsorption and size exclusion. Nanofiltration (NF) membranes have a high removal rate for pharmaceutical and personal care products (PPCPs) in drinking water, but they also reject critical minerals (e.g., calcium and magnesium) that are beneficial to health. Herein, polyethersulfone (PES)/sulfonated polysulfone (SPSf) loose NF membranes were fabricated using non-solvent induced phase separation (NIPS) to enable efficient rejection of PPCPs while preserving high mineral permeability. The resultant loose NF membrane showed increased negative charge owing to the -SO 3 - groups of SPSf. It also exhibited a high water permeance of ∼20.8 L m-2 h−1 bar−1 characterized by high PPCPs/minerals selectivity (i.e. , rejection of PPCPs > 90 % and rejection of Mg2+ < 5 %). The filtration performance of resultant membrane indicated that the ionic PPCPs (e.g., Indomethacin, Diclofenac Sodium, Levofloxacin, Norfloxacin) were removed by the electrostatic repulsion and adsorption, while the removal of non-ionic PPCPs (e.g., Bisphenol A, Carbamazepine) was primarily dominated by the synergy of adsorption and size exclusion. Therefore, the superior removal rate of hydrophilic PPCPs was due to enhanced PPCP-membrane adsorptive interaction. This study provides a profound understanding of the selective separation mechanism of loose NF membranes for micropollutants and minerals. [ABSTRACT FROM AUTHOR]

[Display omitted] • PEG as compatibilizer enhanced the miscibility of PSF/EVOH as H-bond interaction. • EVOH improved surface pore size of PSF/EVOH blend membrane in the presence of PEG. • Increasing PEG at fixed EVOH concentration increased spongy morphology (PSF/EVOH). • Blend membranes showed improved hydrophilicity and antifouling properties. Hydrophilic poly (ethylene-co-vinyl alcohol) (EVOH) was blended with hydrophobic polysulfone (PSF) in the presence of polyethylene glycol (PEG) (20 kDa), which acted as a hydrophilic additive and compatibilizer, to fabricate ultrafiltration (UF) membranes with high porosity and antifouling properties. The polymer blend containing 10 wt% EVOH was selected for optimization using PEG (0 to 24 wt%). After a detailed study, it was concluded that 20 wt% of PEG content was optimal for mixing with PSF/EVOH to increase miscibility. The membranes were characterized using differential scanning calorimetry (DSC) analysis, contact angle, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The effectiveness of PEG as a compatibilizer was observed via no phase separation occurred when the solution was allowed to stand at room temperature for four weeks. It was further confirmed by the appearance of a single T m peak in DSC. In addition, molecular dynamic simulations illustrated that the PSF/EVOH 90/10 wt% blend had a radial distribution of g(r) = 3.29 Å, and g(r) = 2.69 Å in the presence of PEG, indicating better miscibility in the presence of PEG. Pure water permeance of blend membrane (85/15 wt%) reached 316 L.m-2h−1 bar−1, 54% greater than the pristine membrane. Simultaneously, bovine serum albumin (BSA) rejection of up to 97% and permeance recovery ratio of 87% were observed for the PSF/EVOH 90/10 wt% blend membrane, showing improved hydrophilicity and antifouling properties. These findings identify a potential modifier for fabricating low fouling UF membranes for wastewater treatment by blending with EVOH and PEG. [ABSTRACT FROM AUTHOR]