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Polyvinylidene fluoride (PVDF) membrane and its derivative have been investigated the permeation ability for creatinine and urea. The membrane was made by an inversion precipitation system in N,N-dimethyl acetamide (DMAc) and water as non-solvents. In this study, the modification of PVDF membrane permeability with PEG additives, CBT variations, and sulfonation was successfully carried out. The membrane solidification process was carried out on three variations of the coagulation bath temperature (CBT): 30, 45, and 60 °C. Eight types of membranes were characterized by using FT-IR and TGA/DSC, followed by the analysis of their porosity, hydrophilicity, water uptake, swelling degree, tensile strength, and permeability of creatinine and urea. The FT-IR spectra indicate that PVDF modification has been successfully carried out. The porosity, hydrophilicity, water uptake, and swelling degree values increase with the modification of functional groups. Furthermore, improvements in creatinine and urea permeability and clearances are achieved by increasing CBT and sulfonation in the PVDF/PEG membrane. The presence of sulfonate groups improves the membrane permeability through the interaction of intermolecular hydrogen with water and dialysate compounds. The existence of PEG as a porogen enhanced membrane porosity. Creatinine and urea clearance values increase from 0.29–0.58 and 6.38–20.63 mg/dL, respectively.

• Porous β-phase PVDF membranes were successfully fabricated by incorporating LiCl salt. • LiCl influences both PVDF chain arrangement and membrane structure. • Membrane performances were changed with the range of LiCl composition. • Polar β-phase PVDF membranes showed antifouling properties. Polyvinylidene fluoride (PVDF) membranes, acclaimed for their outstanding chemical resistance, thermal stability, and mechanical properties, play a crucial role in diverse industrial purification applications. While various methods have been employed for fabricating PVDF membranes such as thermally induced, evaporation-induced, vapor-induced, and nonsolvent-induced phase separation processes, controlling the polarity of PVDF chains using these techniques remains challenging. Recent studies have shown that the nonpolar α-phase PVDF is susceptible to organic acid fouling owing to hydrophobic interactions, whereas the β-phase PVDF has demonstrated polarity and offers antifouling properties. Herein, porous PVDF membranes predominantly composed of the β-phase were successfully fabricated by incorporating a small amount of LiCl salt into the PVDF dope solution. The addition of LiCl influences ion–dipole moments between ions and PVDF during phase separation, simultaneously affecting the PVDF chain arrangement and membrane morphology. Since the LiCl additive alters both the pore size and structure of PVDF membranes, both freestanding and non-woven supported membranes were prepared and characterized to assess the effects of polarity and pore size on fouling tendency. Characterizations of prepared PVDF membranes revealed considerable changes in the PVDF polymorph, membrane morphology, pore size, and antifouling properties upon introducing the salt additive. Our findings imply that β-phase–dominant PVDF membranes can be effectively utilized in water purification applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modification of polyvinylidene fluoride (PVDF) powder using polydopamine (PDA). • Nanoparticles of zero-valent nickel–iron (nZVNi/nZVI) are evenly distributed on the surface and within the pores of the membrane. • The composite membrane demonstrates efficient removal performance of hexavalent chromium and excellent stability. • The removal mechanism of the nZVNi/nZVI-PDA@PVDF membrane includes electrostatic attraction, surface complexation, and reduction. Nano zero-valent iron (nZVI) is extensively employed in the realm of wastewater treatment. However, conventional synthesis methods involve inherent risks of nZVI oxidation and aggregation, resulting in challenging recovery and potential waste generation. To address these concerns and improve stability, nano zero-valent nickel (nZVNi) was employed as a modifier for nZVI. The modified nZVNi/nZVI was successfully blended with polydopamine (PDA)-modified polyvinylidene fluoride (PVDF) powder, enabling the preparation of a novel hydrophilic composite membrane termed nZVNi/nZVI-PDA@PVDF (NFPP). PDA played a crucial role in effectively immobilizing nZVI particles and preventing their oxidation and aggregation. Scanning electron microscopy was used to confirm the consistent dispersion of nZVNi/nZVI particles both on the surface of the membrane and within its pores. Moreover, the NFPP membrane exhibited excellent performance in removing Cr(VI), with a maximum adsorption capacity of 75.65 mg/g. The presence of PDA endowed the NFPP membrane with a plentiful supply of hydroxyl and amino groups, enhancing its hydrophilicity, antioxidation properties, and loading capacity for nZVNi/nZVI. Additionally, the NFPP membrane demonstrated remarkable resistance to interference under different pH and ionic conditions. The removal of Cr(VI) by the NFPP membrane followed a pseudo-second-order kinetics and Langmuir isotherm adsorption model. Furthermore, the NFPP membrane retained good performance and stability in Cr(VI) removal even after undergoing five cycles. This study indicates that the highly efficient NFPP composite material holds promising potential for application as a functional material in heavy metal wastewater treatment. [ABSTRACT FROM AUTHOR]

Rational design of hydrophilic hierarchical structures on the membrane surface is a promising method to improve oil/water separation efficiency. However, oil droplets with intrinsic adhesion tend to accumulate on the membrane surface, which deteriorates membrane performance. In this study, tannic acid-Zn(II) complex was homogeneously anchored on the PVDF membrane surface and further in situ converted to ZIF-8 in the presence of 2-methylimidazole. Subsequently, Cu ion exchange was employed to transfer ZIF-8 layer to gerhardtite (Cu 2 (OH) 3 NO 3) with a hierarchical structure. Accordingly, the as-prepared PVDF/TA-gerhardtite membrane possessed attractive hydrophilicity and underwater superoleophobicity with oil contact angles above 150°, therefore achieving over 98 % oil rejection towards various surfactant stabilized oil-in-water emulsions. Moreover, self-cleaning properties can be realized by activating peroxymonosulfate, and 97 % of tetracycline hydrochloride, the target pollutant, was degraded within 30 min owing to the generation of sulfate radicals and hydroxyl radicals. Due to the attractive hydrophilicity and catalytic oxidation capacity of the gerhardtite hierarchical structure, degradation and bubble generation induced fouling recovery was accomplished after PMS cleaning, and the irreversible fouling decreased to 2.2 % after consecutive soybean oil fouling. Therefore, this work provides new insights into the construction of hierarchical structures on membrane surfaces and demonstrates their potential applications in oil/water separation and fouling mitigation. [Display omitted] • A gerhardtite hierarchical structure is formed on the PVDF membrane surface. • In situ conversion and ion exchange are employed to realize homogeneous modification. • PVDF/TA-gerhardtite membrane exhibits attractive oil/water separation efficiency. • The membrane features attractive stability and anti-fouling performance. • Irreversible oil fouling was significantly reduced in the presence of PMS. [ABSTRACT FROM AUTHOR]

• Waste utilization, simple process and no secondary pollution. • Underwater superoleophobicity can reduce membrane fouling. • The PDBS membrane can be reused to separate oil-in-water emulsions. • The PDBS membrane features high mechanical strength and excellent salt resistance. The wetting properties and roughness modification of membrane surfaces are crucial for their application in emulsion separation. However, traditional membrane modification methods suffer from high cost, complex preparation, and secondary pollution. In this study, a novel, simple, and economical interfacial engineering method was developed using tannic acid (TA), sodium alginate (SA), and sheep bone powder (BP) as raw materials. Through vacuum filtration, these materials were deposited onto polyvinylidene fluoride (PVDF) membrane to fabricate superhydrophilic/underwater superoleophobic filtration membrane (PDBS). BP induced surface roughness and wetting properties to the membrane, while preserving the porous structure of the substrate membrane. The complex formed by TA and SA encapsulated BP onto the surface of PVDF microfiltration membrane, enhancing its mechanical properties. The prepared membrane exhibited a membrane flux of 347 Lm−2h−1 bar−1 and a separation efficiency of 99.9 % for emulsified oil. Furthermore, after soaking in NaCl solution for 30 h, the membrane still showed excellent stability. Therefore, this study developed a new membrane surface modification strategy with promising application prospects in oily wastewater treatment. PDBS membrane has the property of super-hydrophilic in the air and super-oleophobic underwater, which can effectively separate oil-in-water emulsions. [Display omitted] [ABSTRACT FROM AUTHOR]

Oily wastewater with heavy metal ions poses a substantial environmental risk to human and ecosystem. The one-step separation of oily wastewater with heavy metal ions through membrane technology remains challenging due to membrane fouling and limited multifunctionality. In this work, a one-step polymerization and co-deposition process was employed to coat polyvinylidene fluoride (PVDF) membranes with layer of polydopamine (PDA) and poly-(sulfobetaine methacrylate) (PSBMA), finally obtaining the PDA/PSBMA-coated PVDF membranes. The zwitterionic nature of PSBMA in this coating, characterized by high dipole moment and strong hydrophilicity, significantly enhanced the antifouling properties and hydrophilicity of the PVDF membranes, meanwhile enabling the adsorption of heavy metal ions. The optimized mass ratio of dopamine (DA) to sulfobetaine methacrylate (SBMA) showed in a modified membrane with significantly increased permeability (from 0 to 5017.9 L m−2 h−1 bar−1) and high separation efficiencies (above 99.0 % for oil-water mixtures and 96.0 % for emulsions). The PDA/PSBMA-coated PVDF membranes demonstrated exceptional one-step separation performance for oil-water emulsion with heavy metal ions, particularly for the Cu2+ adsorption efficiency and oil-water separation efficiency of 63.2 % and 94.2 %, respectively. The atomistic molecular dynamics (MD) simulations theoretically revealed that the excellent performance of membrane separation could be attributed to the synergistic electrostatic and hydrophilic effects of the charged groups in the PDA/PSBMA coating. This study provides a practical strategy for the development of advanced multifunctional membrane technology suitable for the treatment of complex oily wastewater. [Display omitted] • PDA/PSBMA-coated PVDF membranes exhibit exceptional one-step separation performance for oil-water emulsion with heavy metal ions. • The outstanding performance is attributed to the synergistic electrostatic and hydrophilic effects of PDA/PSBMA coating. • Offering a feasible strategy for developing advanced membrane technology to separate complex oil-water mixtures. [ABSTRACT FROM AUTHOR]

Although membrane technology has demonstrated outstanding pathogen removal capabilities, current commercial membranes are insufficient for removing small viruses at trace levels due to certain limitations. The theoretical and practical significance of developing a new form of hydrophilic, anti-fouling, and virus-specific ultra-purification membrane with high capturing and separation efficiency, stability, and throughput for water treatment is of the utmost importance. In this study, molecularly imprinted membranes (MIMs) were fabricated from polyvinylidene fluoride (PVDF) membranes utilizing novel surface hydrophilic modification techniques, followed by the immobilization of virus-specific molecularly imprinted nanoparticles (nanoMIPs) as synthetic receptors. Three distinct membrane functionalization strategies were established and optimized for the first time: membrane functionalization with (i) polyethyleneimine (PEI) and dopamine (DOP), (ii) PEI and 3-(chloropropyl)-trimethoxysilane (CTS), and (iii) chitosan (CS). Hydrophilicity was enhanced significantly as a result of these modification strategies. Additionally, the modifications enabled spacer arms between the membrane surface and the nanoMIPs to decrease steric hindrance. The surface chemistry, morphology, and membrane performance results from the characterization analysis of the MIMs demonstrated excellent hydrophilicity (e.g., the functionalized membrane presented 37.84° while the unmodified bare membrane exhibited 128.94° of water contact angle), higher permeation flux (145.96 L m−2 h−1 for the functionalized membrane), excellent uptake capacity (up to 99.99 % for PEI-DOP-MIM and CS-MIM), and recovery (more than 80 % for PEI-DOP-MIM). As proof of concept, the cutting-edge MIMs were able to eliminate the model adenoviruses up to 99.99 % from water. The findings indicate that the novel functionalized PVDF membranes hold promise for implementation in practical applications for virus capture and separation. [Display omitted] • Three distinct surface modification strategies established for PVDF membranes. • Integration of synthetic receptors on functionalized membranes using spacer arms. • High performance virus capturing and separation using functionalized membranes. • Membrane modification optimized by AFM, SEM, contact angle & surface energy analyses. • 99.99 % elimination of pathogenic viruses from water samples. [ABSTRACT FROM AUTHOR]

Membrane‐based treatment for demulsification remains a significant challenge due to membrane fouling. In this work, the demulsification and membrane separation technology were combined to design polyvinylidene fluoride (PVDF) membrane with demulsification function. The hyperbranched polyethyleneimine was prepared by the acyl chloride reaction and grafted on the PVDF membrane by dopamine. The effects of different amounts of hyperbranched polyethyleneimine on PVDF membrane were studied. The modified membrane was characterized by SEM, CA, FTIR, and XPS, and then the optimum preparation conditions were selected. The separation test shows that the modified membrane can be used to separate oil‐in‐water emulsions and the separation efficiency was more than 90%, meanwhile it showed good anti‐pollution performance owing to the water‐based protective layer on the membrane surface and the steric effect of the branches. In addition, the demulsification mechanism was analyzed and it was found that the surface tension was the key point for demulsification. [ABSTRACT FROM AUTHOR]

The polyvinylidene fluoride (PVDF) membranes were synthesized using immersion precipitation technique. The effect of four solvents, N, N-dimethyl formamide (DMF), N, N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO) on the water flux and beef serum albumin (BSA) rejection efficiency was reported. The structure and morphology of PVDF membranes were studied using Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and water contact angle measurements. The cross-section of a membrane formed in a DMF as a solvent exhibit a spongy/fingerlike hybrid structure, while DMSO favors the formation of more porous structure. The increase in the solvent mass fraction facilitates liquid phase separation and solution casting, and changes the structure of PVDF membrane from denser, bicontinuous structure to a looser, stacked structure. Moreover, the results revealed that the properties of PVDF membranes sub-layer are controlled by the diffusion rate of the nonsolvent. The membrane with the best performance was prepared using 80% DMF (mass fraction) as a solvent, and it reached water flux of 66 L·m−2·h−1, and 91.53% BSA rejection efficiency. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF) membrane are widely used in water treatment due to its good physical and chemical properties, and the pores of PVDF membranes determine most of the characteristics of PVDF membrane. The hydrophilic porogens play an important role in the preparation of PVDF membranes and the regulation of membrane pores. In this work, three hydrophilic porogens with different quality components were used to prepare PVDF ultrafiltration membranes by the nonsolvent induced phase separation (NIPS) method. Through the Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), mechanical strength, contact angle and other characterizations, the influence of hydrophilic porogens on the surface free energy, microstructure and performance of PVDF membrane were studied. The results suggest that lithium chloride (LiCl) can inhibit the formation of macropores and improve the mechanical strength of the membrane. Polyvinylpyrrolidone (PVP) can form through-hole through the PVDF membrane. All three hydrophilic porogens can increased the surface free energy of the PVDF membranes, where polyethylene glycol (PEG) had the most impact on the surface free energy. [ABSTRACT FROM AUTHOR]

Fe3O4@TiO2 magnetic photocatalytic particles were synthesized and characterized. A composite PVDF separation membrane blended with Fe3O4@TiO2 particles was prepared by the phase inversion method. The main purpose was to explore the effect of magnetic fields on the performance of membranes during coagulation bath. The structure characterization, permeability, interception ability, and anti-pollution performance of inorganic particle blend membranes were then tested. Results showed that magnetic field coagulation baths have little effect on the pore structure and hydrophilicity of the membrane surface. When the liquid membranes was condensed under a magnetic field, the magnetic photocatalytic particles could migrate at a greater rate to the surface of the membrane. Through performance tests of the PVDF modified membranes, it was found that a magnetic coagulation bath could promote more Fe3O4@TiO2 to aggregate on the surface of the membrane, which led to the blend membrane formed under the magnetic coagulation bath had better antifouling performance against humic acid solution under ultraviolet light irradiation. Membranes with 0.5 wt% magnetic photocatalytic particles in a magnetic field coagulation bath performed best. When filtered under the condition of ultraviolet light, its pure water flux was 1752 L/(m2 h), and the rejection rate of 20 mg/L humic acid solution was 67.17%. The flux attenuation before and after filtration was 38.84%, the flux recovery rate was 91.10%, and the irreversible pollution index was only 8.90%.

A series of polyvinylidene fluoride membranes (PVDF) and TEOS modified PVDF membranes are prepared using N,N-dimethylacetamide (DMAc) as the solvent and the immersion preripitation phase inversion method (NIPS). The morphology of the film is observed with a scanning electron microscope, and the influence of the concentration of the casing solution and the TEOS additive on the properties of the film material is investigated through the contact angle, porosity, water permeability and other performance characteristics. The results show that compared with pure membranes, the addition of ethyl orthoriticate can improve the overall performance of hybrid membranes. The concentration of the casing solution is 17%, and the PVDF hybrid membrane prepared by adding 1% TEOS has a contact angle of 86.06°, a porosity of 42.86%, and a water permeability of 2.080 L/(m² • h). At this time, the synthesis of the hybrid membrane achieves the best performance. [ABSTRACT FROM AUTHOR]

In this paper, ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate was the first time successfully utilized as single solvent in preparing the PVDF membrane with a good performance by N-TIPs method. The effects of quenching temperature and hydrophilic additive content on the morphology, permeability, and strength of the membranes were studied. All the prepared PVDF membranes were proved to be a pure β phase by FTIR and XRD, possessing a narrow pore size distribution. By adjusting quenching temperature and additive content, membranes with a flux of 383.2 L/m2 h and concentrated pore diameter of 26 nm obtained. [ABSTRACT FROM AUTHOR]

[Display omitted] FeS 2 -embedded in porous carbon (FeS 2 /C) was prepared by simultaneous sulfidation and carbonization of an iron-based metal–organic framework precursor, and subsequently immobilized in polyvinylidene fluoride membranes (FeS 2 /C@PVDF) for organics removal via peroxymonosulfate (PMS) activation. The composition, structure, and morphology of the FeS 2 /C@PVDF membrane were extensively characterized. Scanning electron microscopy images manifest that the FeS 2 /C nanoparticles with an average diameter of 40 nm are assembled on the external and internal membrane surface. The as-prepared FeS 2 /C@PVDF membrane exhibits excellent performances over a wide pH range of 1.53–9.50, exceeding carbon-free syn -FeS 2 @PVDF. The effective degradation could be improved by inner pyrite FeS 2 cores and thus enhanced the electron transfer between carbon shell and PMS. Electron paramagnetic resonance and quenching experiments elucidated that radical ( HO ∙ , SO 4 ∙ - ) and nonradical (1O 2) species were the predominant reactive oxidants. In addition, FeS 2 /C@PVDF exhibited high stability with low Fe leaching (0.377 mg/L) owing to the effective protection of the outer carbon skeleton. Plentiful porosity of PVDF membranes not only affords a controlled size and confined uniform distribution of the immobilized FeS 2 /C nanoparticles, but also enables a persistent exposure of active sites and enhanced mass transfer efficiency. Our findings demonstrate a promise for utilizing the novel FeS 2 /C@PVDF membrane as an efficient catalyst for the environmental cleanup. [ABSTRACT FROM AUTHOR]

A double‐effect membrane distillation (DE-AGMD) process was developed by equipping air gap membrane distillation (AGMD) with internal heat recovery. In this arrangement, the latent heat of the first effect will be recycled as a source of heat for the second effect. More produced water without adding energy. This configuration improves the efficiency of the process, and SEC (specific energy consumption) decreases. The potentialities of DE-AGMD to desalt seawater were investigated. Response surface methodology (RSM) is used to model and optimize the operating parameters for water desalination by DE-AGMD. Permeate flux (Jp) and salt rejection (R %) were the main performance responses to optimize. The temperature difference (ΔT), width of air gap (δ), feed flow rate (Qf) and cooling solution flow rate (Qc) were the operating parameters investigated to optimize the performance of DE-AGMD. The obtained quadratic regression model is validated by analysis of variance (ANOVA). The high values of R2 = 99.86 and R2 adj = 99.7 confirmed that the quadratic equation properly fitted the experimental data. The optimal operation parameters are found to be 52.28 °C for the temperature difference, 25.62 L h−1 for the feed flow rate, 23.87 L h−1 for the permeate flow rate and 3 mm for the air gap width. Under these conditions, the permeate flux could reach 4.69 L m−2 h−1. The experimental and predicted results show a good agreement confirming the fit of the models by 97.78%. The modeling of salt rejection is found to be difficult due to the steadiness of response for all experimental runs (> 97%). [ABSTRACT FROM AUTHOR]

Oily wastewater is one of the most challenging streams to deal with especially if the oil exists in emulsified form. In this study, electrospinning method was used to prepare nanofiberous polyvinylidene fluoride (PVDF) membranes and study their performance in oil removal. Graphene particles were embedded in the electrospun PVDF membrane to enhance the efficiency of the membranes. The prepared membranes were characterized using a scanning electron microscopy (SEM) to verify the graphene stabilization on the surface of the membrane homogeneously; while FTIR was used to detect the functional groups on the membrane surface. The membrane wettability was assessed by measuring the contact angle. The PVDF and PVDF / Graphene membranes efficiency was tested in separation of emulsified oil from aqueous solutions. The results showed that PVDF-Graphene nanofiber membrane exhibited better performance than the plain PVDF nanofiber membrane with average water flux of 210 and 180 L.m-2.h-1, respectively. Both membranes showed high oil rejection with more than 98%.

Membrane materials have been extensively applied in the field of separation of oil–water mixtures. However, most membrane materials are limited to separate oil–water mixtures and difficult to separate stable oil–water emulsions. Therefore, the polymer membrane, which is a type of underwater superoleophobic membrane material, has attracted extensive attention for its excellent antipollution performance and emulsion separation ability. In this work, we combined the synthesized poly (acrylic acid)‐co‐poly(3‐[trimethoxysilyl]propyl methacrylate) (PAA‐co‐PTMSPMA) with micro–nanoparticles to modify polyvinylidene fluoride (PVDF) membranes. By means of this strategy, PVDF membranes with excellent superhydrophilicity–underwater superoleophobicity were successfully fabricated. The obtained PVDF membrane could efficiently realize the separation of various oil‐in‐water emulsions, and the separation efficiency was greater than 99%. In addition, the separation efficiency of the modified superhydrophilic PVDF membrane maintained stable after 10 separation cycles (>98.6%). When relying on this simple and eco‐friendly preparation strategy, this superhydrophilic–underwater superoleophobic membrane material has broad application prospects in the field of industrial and domestic wastewater treatment. [ABSTRACT FROM AUTHOR]

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In this study, a high-flux PVDF membrane for dye desalination was prepared using the small-molecule stacked swelling strategy. Firstly, 1,3-bis [tris(hydroxymethyl) methylamino] propane was grafted on the molecular chain of poly(vinylidenefluoride-co-chlorotrifluoroethylene)(PVDF-CTFE) to prepare the non-porous membrane with a thin skin layer by the NIPS method. Then, this non-porous membrane was placed in the glutamate reaction solution to make it undergo the nucleophilic substitution reaction with the C–Cl bond on the main chain of PVDF-CTFE, and then swelling treatment was performed with an alkaline aqueous solution. In this paper, the influence of the swelling effect of small-molecule glutamate with different degrees of reactivity on the membrane pore size and structure was investigated, and the dye/salt separation performance of glutamate-treated swelling membrane was compared with that of the membrane treaded with the larger-molecule tris-propanesulfonic acid. Based on the fact that glutamic acid has small molecular size and steric hindrance, the results show that glutamic acid with different reaction degrees induced single-molecule swelling and multi-molecule stacked swelling, which led to the stepwise increase of membrane pore size. Within a certain degree of reaction, the membrane pore size entered into the pore size platform of different gradients. Therefore, the controllable adjustment of the pore size of the swollen membrane was realized by controlling the degree of reaction of the grafted side chains. The pore size of the multi-molecule stacked swelling membrane of small molecules not only achieved the effect of the single-molecule swelling membrane of larger molecules but also had a greater number of through holes and higher water flux, and the mechanical properties of the small-molecule stacked swelling membrane did not deteriorate significantly. The optimal small-molecule stacked swelling membrane, G12, not only had a high water flux of 99.4 Lm-2h-1bar-1 but also rejected nearly 99 % of the dye and allowed most of the salts (>98 %) to permeate through the membrane when dealing with the mixed solution of direct red 80 and NaCl. [Display omitted] • Adjusting the degree of reaction of the hydrophilic side chains can initiate single-molecule swelling and multi-molecule stacked swelling effects. • The pore size platform of membrane appears at the different gradients, and the number of through holes and membrane flux rises at the pore size platform stage. • The stacked swelling membrane of small molecules provides higher flux and more excellent separation performance of dye/salt compared to the single-molecule swelling membrane of larger molecules. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PVDF membranes can be γ-ray modified with N-vinyl-2-pyrrolidinone (NVP). • The mechanism of γ-ray graft modification of PVDF membrane was elucidated. • Water treatment properties of the prepared membrane exhibited significant improvement compared with PVDF membrane. • The interaction between the membrane and water molecules was investigated through molecular dynamics simulation. Polyvinylidene fluoride (PVDF) membrane is a cheap and commonly used separation material, but its inherent hydrophobicity results in significant membrane contamination, which limits its engineering application and further development. The hydrophilic PVDF-g/co-NVP membrane was prepared through low-dose γ-ray irradiation and using N-vinyl-2-pyrrolidinone (NVP) as a modifier in this study. The effects of γ-ray dose and incorporating NVP additive on the microstructure, hydrophilicity, anti-fouling capability, and mechanical capacity of membranes were discussed. Molecular dynamics (MD) simulation method was used to comprehensively investigate the impact of the NVP on the physicochemical characteristics of membrane structure. Under a specific NVP load, the water contact angle of the membrane decreases from 87.92° to 52.66°. The pure water permeance reaches 362.1 L/m2 h, and the porosity increases to 55.21 %±1.29 %, which indicates that γ-ray irradiation with NVP addition can effectively adjust the pore structure and hydrophilicity of the membrane. During anti-fouling test against bovine serum albumin (BSA), the modified membrane exhibits remarkable anti-fouling characteristics, including reduced BSA accumulation, enhanced flux recovery, lower irreversible contamination level, and extended cleaning cycle compared with the original pure PVDF membrane because of its higher hydrophilicity and positive zeta-potential value. This study elucidates the mechanism underlying γ-ray graft modification of PVDF membranes, thereby providing valuable insights into the development of efficient functional membrane materials. [ABSTRACT FROM AUTHOR]

This work presents an approach to form zwitterionic porous poly(vinylidene fluoride) (PVDF) membranes fabricated by vapor-induced phase separation (VIPS). The reaction between maleic anhydride groups, incorporated initially in the casting solution by blending styrene maleic anhydride (SMA), with 3-((3-aminopropyl)dimethylammonio)propane-1-sulfonate led to the desired zwitterionic moieties. XPS and FTIR analyses confirm the functionalization of the membrane. SEM analyses revealed that it did not have any major impact on the membrane morphology deemed to be close to bicontinuous. While the mean pore size of the virgin membrane was 0.57 μm, it increased to 0.85 μm suggesting the pore-forming effect of SMA during the phase-inversion process. Hydration was significantly enhanced, attributed to the zwitterionic groups on the one hand, but also to the formation of carboxylic acid and amide groups following the ring-opening reaction. It led to significant resistance to bacterial attachment as tested with 4 strains of bacteria including Escherichia coli , Stenotrophomonas maltophilia , Staphylococcus aureus and Streptococcus mutans (>99 % reduction for each). Applied in cyclic water/bacterial solution filtration tests, the modified membrane showed clear improvement in overall performances. Hence, for the virgin membrane, the initial water permeability, flux recovery ratio after the first cycle and flux recovery ratio after the second cycle were found to be 3000 L m−2 h−1.bar−1, 12 % and 53 %, respectively. For the optimized zwitterionic membrane, they were measured to be 7000 L m−2 h−1.bar−1, 26 % and 100 %, respectively. The efficacy of styrene maleic anhydride as a precursor for achieving stable and efficient zwitterionization of PVDF microfiltration membranes is evidenced, rendering it valuable for the filtration of microorganism-containing wastewater. Moreover, its potential application extends to the biomedical realm. [Display omitted] • Zwitterionization of membranes based on the ring-opening of maleic anhydride is proposed. • Mitigation of attachment by gram-positive/gram-negative bacteria and blood cells is achieved. • The modification mitigates irreversible fouling by Escherichia coli during filtration. • The sulfobetaine-derivative and arising resistance to Escherichia coli remain after long immersion. [ABSTRACT FROM AUTHOR]

[Display omitted] • MOFs like MIL-88A(Fe) were synthesized by industrial precursors and solvents. • MOFs were efficiently separated and purified by a self-made apparatus. • Continuous operation significantly reduced invested, operation, time, and human cost. Metal-organic frameworks (MOFs) have been widely investigated due to their fascinating structures and properties. However, the time-cost synthetic process and the difficult separation from liquid phase hinder their practical application. In this study, a self-made automatic apparatus containing commercial poly(vinylidene fluoride) (PVDF) hollow fiber membranes was used to separate MOFs from large-volume suspension. Taking MIL-88A(Fe) synthesized with industrial-grade chemicals as an example, the investment cost, operation cost, human cost, time duration during separation process, and unit cost price of MIL-88A(Fe) were significantly reduced by 62%, 82%, 100%, 90%, and 36%, respectively, compared to those of centrifugation. More importantly, MIL-88A(Fe) powders that were separated and purified by the apparatus were easy to be removed from membrane surface by slight vibration, which displayed good morphology, crystallinity, as well as high degradation efficiency toward organic contaminants via photo-Fenton reaction. Meanwhile, the membrane can be reused instantly without any rinse. More encouragingly, this method is applicable to other MOFs' separation, like ZIF-8 and ZIF-67. This study further confirmed the potential and prospective of high-throughput production and facile separation of MOFs for practical applications. [ABSTRACT FROM AUTHOR]

There is growing interest in membrane distillation (MD) as a means of desalinating seawater with 100 % theoretical salt rejection which has the capacity to address freshwater scarcity. MD has huge potential for commercial applications owing to its low operating temperature and pressure requirements. However, wetting polymeric membranes inhibits water permeance and lowers salt rejection. MXene nanosheet-incorporated polyvinylidene (PVDF) membranes have been constructed for enhanced vapor transport with high water repellence and antiwetting properties. MXene nanosheets in PVDF polymeric matrices are responsible for their high super-hydrophobicity, which can mitigate membrane fouling and wetting during the MD process. As far as experimental outcomes are concerned, the pristine PVDF membrane exhibited severe wetting with salt leakage. Ti 3 C 2 Tx MXene nanosheets allow the formation of hierarchical polymeric micro/nanostructures, changing the intrinsic hydrophilicity to super-hydrophobicity. Surface engineering of a PVDF membrane with MXene nanosheets enables efficient saline desalination during the MD process. The surface-engineered MXene/PVDF membrane demonstrated a high-water contact angle of 143° with extremely high self-cleaning characteristics as compared to that of pristine PVDF membrane. As far as the performance of the membrane is concerned, the water flux of the pristine PVDF membrane decreased from 6.5 LMH to 6 LMH after the 14th hour which can be attributed to partial pores wetting during MD operation. Eventually, the pristine PVDF membrane exhibited a continuous salt flux (SF) increase. However, MXene/PVDF membrane showed stable water flux (8 LMH) and negligible SF. The study therefore demonstrates a facile and holistic approach for constructing MXene-based PVDF membranes that exhibit superior antiwetting performance during MD operation. [Display omitted] • Incorporation of MXene nanosheets in polyvinylidene (PVDF) polymeric matrices • Pristine PVDF membrane exhibited lower productivity in terms of flux and salt rejection. • Self-cleaning and antiwetting characteristics observed for MXene/PVDF membrane. • Increase of nearly 45.9 % in contact angle and decreased by 77.5 % in sliding angle [ABSTRACT FROM AUTHOR]

• The copolymer of P (PEGMA-co-BVIm-Br) with PVI and PEGMA monomer was prepared by polymerization (RAFT) method and the newly modified super-hydrophilic M2-M6 membrane through NIPS. • Structural parameters in the morphology and performance of M1-M6 modified and unmodified membranes were investigated. • The modified membrane has a high anti-fouling nature and cleanliness nature and temperature-sensitive. • The M6 membrane exhibits a super hydrophilic membrane with a Mean±SD contact angle of 33.8±1.55 and the Mean±SD oil rejection of 96.1±1.3% and an increase in water flux. The conventional Polyvinylidene Fluoride (PVDF) membrane was modified by polymerization Reversible addition−fragmentation chain-transfer (RAFT) with copolymer (PEGMA-co-BVIm-Br) on the upper bulk. This copolymer was obtained from the synthesis of (BVIm-Br) 3-butyl-1-vinyl-1-H-imidazole-3-ium bromide and the vinyl imidazole (VI) monomer N-vinyl imidazole (a hydrophilic monomer) and 1-bromobutane (C4H9Br). The analysis of such as ATR-FTIR, the magnetic resonance of H-NMR nuclei, zeta potential, Water Contact Angle (WCA), and Scanning Electron Microscopy (SEM) confirmed the presence of copolymer on the surface of the modified membrane. The bonding of this copolymer on the membrane surface reduced the WCA of the membrane water (from 89.5 ±1.96 to 33.8 ±1.55). The raw PVDF membrane (M1) and modified membrane (with total ratio-P(PEGMA-co-BVIm-Br) copolymer 2.5 % (M2), 5 % (M3), 10 % (M4), 20 % (M5), and 40% (M6) to (raw PVDF membrane) membrane showed appropriate hydrophilic nature and excellent separation of oil droplets from water/oil emulsions in the simulated effluent on the surface. This operation was performed for a comprehensive study on the determined parameters and by filtration with simulated petrochemical industry effluent (containing water/oil emulsion). Therefore, the recovery efficiencies of water flux, flow flux, oil recovery amount, as well as total fouling of M6 membrane were reported 96.14±0.99 and 428±2.6 L/ (m2 h), 96.1±1.3%, and 17.18±0.37%, respectively. This study aimed to prepare a copolymer-modified membrane that can show high performance in cleaning and resistance to various fouling, such as Rt, Rr, and Rir at the specified temperature, after long-term emulsion separation. [Display omitted] [ABSTRACT FROM AUTHOR]

• New hybrid material composed of ginger extract and silica nanoparticles (GE-SiNPs) were synthetized via sol-gel process. • GE-SiNPs material implicated in the increasing of hydrophilicity and anti-biofouling of membrane. • The PVDF/GE-SiNPs membrane showed antibacterial properties against Escherichia coli and Staphylococcus aureus. • Fouling analysis of BSA concentration was studied using cross-flow filtration. The highest flux recovery ratio (FRR) was satistifically reached of 97.92%. Hybrid material combines organic-inorganic substituents that can impose hydrophilicity and anti-biofouling properties in polymeric membranes. In this study, ginger extract-silica nanoparticles (GE-SiNPs) hybrid materials were synthesized through the sol-gel technique and was applied as a new additive to improve polyvinylidene fluoride (PVDF) membrane properties. Ginger (Zingiber officinale Roscoe) extract (GE) contains phenol derivatives that provide anti-microbial properties; while silica nanoparticles (SiNPs) plays role to increase membrane hydrophilicity and prevent organic fouling. The PVDF/GE-SiNPs membrane was prepared using non-solvent induced phase separation method and was applied to concentrate Bovine Serum Albumin (BSA). The resulted membranes were characterized in terms of morphology, hydrophilicity, tensile strength, porosity, pure water flux, antibacterial property, and its ultrafiltration performance on BSA concentration. The result analysis of fabricated membrane revealed that increasing the loading amount of GE-SiNPs improved membrane hydrophilicity and enlarged membrane porosity. Water permeability was enhanced up to 9.89 from 4.97 LMH. The highest rejection of BSA solution reached of 68.19 %, with the BSA initial concentration of 50 ppm and trans membrane pressure of 1 bar. The flux recovery ratio (FRR) was satistifically reached of 97.92 %. Furthermore, the PVDF/GE-SiNPs also showed antibacterial properties against Escherichia coli and Staphylococcus aureus. [Display omitted] [ABSTRACT FROM AUTHOR]

The performance of a novel polyvinylidene fluoride (PVDF) membrane with high hydrophilicity and enhanced separation ability was discussed with the addition of a small amount of reduced graphene oxide nanoparticles (rGO). The PVDF-rGO ultrafiltration composite membrane was effectively synthesized, by incorporating rGO (0.1% wt) as nanoparticles by the phase inversion process. The impact of these modifications was studied. The morphological structure of the membranes was evaluated by scanning electron microscopy (SEM). The changes in the chemical structure were investigated using Fourier-transform infrared spectroscopy. The SEM images revealed that in the PVDF membrane, the diameter of the pores increased after rGO grafting. Performance tests showed that the PVDF membrane has flux and a rejection of bovine serum albumin about 92% at an optimum transmembrane pressure of 4 bar. The incorporation of rGO improved the protein rejection, reaching a rejection rate of around 92% at 4 bar. These results suggest that incorporating rGO nanoparticles can enhance the permeability of the membrane. The PVDF membrane modified with 0.1 wt.% rGO showed a considerably higher flux than the unmodified membrane. [ABSTRACT FROM AUTHOR]

Novel CoFe alloy and CoFe 2 O 4 nanoparticles encapsulated in N -doped microtube composites (CoFe-NMTs) were firstly fabricated through in-situ pyrolysis of simple-source PBA. As expected, CoFe-NMTs-800 exhibited excellent catalytic activity for PMS activation to depredate tetracycline in a wide pH (2.55–9.55) and in the presence of Cl−, HCO 3 −, H 2 PO 4 − and humic acid (HA). Subsequently, CoFe-NMTs-800 was immobilized into polyvinylidene fluoride (PVDF) membrane as catalytic self-cleaning membrane, the fabricated membrane maintained excellent removal efficiency and self-cleaning property for TC degradation (over 90%) in TC/HA coexistence system. Furthermore, SO 4 −, OH and 1O 2 were responsible for TC degradation and SO 4 − was a major contributor. Recently, the development of dual functional catalytic membrane for the synergistic degradation and filtration of persistent pollutants has attracted considerable attention in environmental remediation. Herein, novel CoFe alloy and CoFe 2 O 4 nanoparticles encapsulated in N -doped microtube composites (CoFe-NMTs) were firstly fabricated through in-situ pyrolysis of simple-source Prussian blue analogues (PBA). As expected, this unique structure not only inhibited the nanoparticles agglomeration, but also provided a "highway" that accelerated the Co3+/Co2+ and Fe3+/Fe2+ redox cycles. Therefore, CoFe-NMT-800 (0.1 g/L, pyrolyzed at 800 °C) achieved over 90% tetracycline (TC, 30 mg/L, 0.1821 min−1) removal after 30 min at a wide pH (2.55–9.55) by coupling with peroxymonosulfate (PMS, 0.3 g/L), which dramatically outperformed the majority of the reported catalysts (such as Co 3 O 4 , CoFe alloy, CoFe 2 O 4 and N -doped carbon nanotubes, etc.). Additionally, CoFe-NMTs-800 also exhibited excellent catalytic activity in the existence of inorganic anions (Cl−, HCO 3 − and H 2 PO 4 −) and natural organic matters (humic acid (HA)). Subsequently, CoFe-NMTs-800 was immobilized into polyvinylidene fluoride (PVDF) membrane as catalytic self-cleaning membrane via applying phase-inversion technology. It was found that CoFe-NMTs-800/PVDF membrane not only maintained high removal efficiency for TC degradation (over 90%) in TC/HA coexistence system, but also effectively eliminated the adverse effect of membrane fouling. Besides, the fabricated membrane also showed desirable reusability and neglectable metal leaching (0.003 mg/L Fe and 0.015 mg/L) with almost constant flux after five cycles. The quenching experiments and electron paramagnetic resonance (EPR) results clearly indicated that sulfate radicals (SO 4 −), hydroxyl radicals (OH and singlet oxygen (1O 2) were responsible for TC degradation and SO 4 − was a major contributor. Significantly, this work was very meaningful to construct novel catalytic self-cleaning membrane for water purification. [ABSTRACT FROM AUTHOR]

The inorganic salts addition can affect the interactions among the polymer chains and further influence the membrane structure. In this work, the effects of calcium chloride (CaCl2) on the crystal structure and separation performance of poly(vinylidene fluoride) (PVDF) membranes were studied. The influence of CaCl2 addition with varying concentrations (0-3 wt.%) was investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and molecular dynamic (MD) simulations. XRD and FTIR characterizations indicated that CaCl2 could induce the transformation of PVDF crystal structure from a to ß, which was further confirmed by molecular dynamic simulation. The MD simulation results revealed that the interaction between Ca2+ and F atom distorted the dihedral angle of PVDF chains, inducing the crystal structure transforming partially. SEM characterization indicated that the finger-like voids became longer and broader with increasing amount of CaCl2 addition. The membrane consisting of 0.7 wt.% CaCl2 exhibited the best performance with bovine serum solution rejection of 84.7% and water permeability of 203.6 L m-2 h-1 bar-1. [ABSTRACT FROM AUTHOR]

Here, we successfully fabricated antifouling zwitterionic polyvinylidene fluoride (PVDF) membranes based on the in situ cross‐linking polymerization of sulfobetaine methacrylate (SBMA) in the casting solutions with the non‐solvent induced phase separation (NIPS) technique. The structure and performance of zwitterionic PVDF membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR) and X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), dynamic water contact angle measurement and filtration experiments. The producing of zwitterion chains anchored on the membrane surfaces and resulted in enhanced hydrophilicity and the separation performance of the membrane has a noticeable improvement. The flux recovery of the membrane increased significantly from ∼ 45.1 to ∼ 90%, reversible fouling (Rr) increased from ∼ 22.2 to ∼ 40.5%, irreversible fouling (Rir) decreased from ∼ 54.9 to ∼ 10% and the bovine serum albumin (BSA) rejection increased from ∼ 9.9 to ∼ 81.5%, indicating the prepared PVDF/PSBMA membranes have excellent anti‐fouling property and high separation efficiency. [ABSTRACT FROM AUTHOR]

Heavy metals like mercury, chromium, lead and copper present in groundwater at lower concentrations cause severe health issues and can even be fatal when consumed. The biopigment/biopolymer melanin can be reaped from different sources like bacterium, fungus, and human hair. It has excellent heavy metal ion scavenging property and can be exploited for non-biological applications, substantially including water purification. In this work, melanin nanoparticles were derived from the marine bacterium Pseudomonas stutzeri and were coated onto hydrophobic polyvinylidene fluoride (PVDF) membrane as a support, for batch and continuous removal of heavy metal studies. Batch studies on the effect of pH, temperature and adsorbate dose and continuous adsorption studies on the effect of flow rate, adsorbate and adsorbent mass loadings were carried out by using biosynthesised melanin-coated PVDF membranes for the removal of Hg(II), Cr(VI), Pb(II) and Cu(II). Scanning electron microscope (SEM) images revealed the surface morphology, Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) deciphered the chemical characteristics of melanin-coated PVDF membranes before and after adsorption. Contact angle measurement confirmed the improvement in hydrophilicity of PVDF membrane upon coating with melanin. The maximum removal percentages of heavy metals achieved by melanin-coated PVDF membranes under batch mode operation were 87.6%, 88.45%, 91.8% and 95.8% for mercury, chromium, lead and copper, respectively optimised at 318 K and pH of 3 for chromium and 5 for other metals. However, the continuous mode of operation with a flow rate of 0.5 mL/min having 1 mg/L of heavy metal solution concentration exposed to 50 mg of melanin loading with a working volume of 200 mL showed better removal efficiencies compared with batch mode. The dynamic studies using Thomas and Yoon–Nelson models described the transient stage of the breakthrough curve and the model constants were calculated for column design and scale-up. [ABSTRACT FROM AUTHOR]

Herein, a composite membrane was synthesized by adding β-cyclodextrin modified Fe3O4/GO (β-MGO) to polyvinylidene fluoride (PVDF), in the presence or absence of magnetic field via the combination of magnetic field induction and phase conversion techniques. FT-IR, Raman, XRD, TEM, XPS and hysteresis loop results indicate β-MGO was synthesized successfully. By analyzing the characterization results of the membrane, β-MGO can be adsorbed onto the surface of the membrane under magnetic field (M-β-MGO) conditions. The changes of pure water flux, BSA rejection, hydrophilicity, porosity, pore size and anti-pollution performance of M-β-MGO and β-MGO membrane were discussed with the content of β-MGO. The M-β-MGO membrane shows the best performance when the β-MGO content is 0.7%. In addition, our experimental results on the removal of heavy metal Cu2+ show that after five cycles, the rejection rate and adsorption capacity of Cu2+ are still as high as 75% and 0.94 mg/g. Meanwhile, it is find that pH > 6 can significantly increase the removal rate of Cu2+, and the membrane is suitable for removing Cu2+ concentrations below 30 mg/L. Therefore, this study presents a novel strategy for developing high-performance hybrid membranes via manipulating the migration of nanomaterials to the membrane surface. [ABSTRACT FROM AUTHOR]

The aim of the research is to develop a cost-effective and environmentally friendly membrane inspection method for over-stored PVDF membranes. It is generally accepted that PVDF-based fiber membranes are sensitive to dehydration during storage. The current practice to prevent this is that membranes stored beyond the planned period are returned to the manufacturer’s site for costly re-impregnation, which like the original impregnation, delivers a glycerol-water solution to the pores. This is a costly process, as it is labor-intensive, needs high raw material consumption, and requires membrane cassettes to be transported over long distances. During the research our goal was to replace this, so we developed a new method to control the drying process. The method involves the in-situ sampling of membrane fibers from filters and transporting the samples to the manufacturer’s laboratory. There we measured the membranes’ performance with a custom-built permeability tester, and the data obtained here were compared with the values measured at the time of manufacturing and from this data we inferred to the condition of the fibers. After 5 y of storage no fiber property degradation was observed. With this method, it’s possible to save 98.78% of the normal storage extension cost. We also experienced a significant reduction in the environmental load, as the yearly transportation of the cassette can be eliminated, thus significantly reducing the CO2 emissions associated with traveling, by 2,423,250 kg for the project under investigation. [ABSTRACT FROM AUTHOR]

• A novel amphiphilic SMA-HEA linker is designed by ring opening reaction. • SMA-HEA is consisted with hydrophobic SMA and hydrophilic HEA segments. • SMA-HEA links PVDF via benzene with hydrophobiC–Hydrophobic adsorption. • SBMA polymerization with SMA-HEA linker for hydrophilicity improving. • Excellent anti-BSA adsorption ability of modified PVDF membrane. The amphiphilic copolymer polystyrene-maleic anhydride (SMA)-2-hydroxyethyl acrylate (HEA) was synthesized for the first time in this study, and used as a linker to graft zwitterionic sulfobetaine methacrylate (SBMA) in order to enhance the hydrophilicity and anti-adsorption ability of polyvinylidene difluoride (PVDF) membranes. This amphiphile linker is composed of a hydrophobic extremity, i.e., the SMA copolymer, and a hydrophilic extremity, i.e., the HEA. The SMA-HEA linker was first dispersed into the PVDF matrix via the blending method, and the hydrophobic polystyrene of SMA was adsorbed into the PVDF membrane via hydrophobic–hydrophobic interaction. The SBMA was then grafted onto the expanded HEA via free radical polymerization. The functional groups, morphologies, and hydrophilicity of the amphiphile-modified PVDF membranes were analyzed by attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscopy (FE-SEM), and water contact angle (WCA) measurements. The PVDF membrane modified with the SMA-HEA amphiphile linker showed significant enhancement in hydrophilicity as the WCA decreased from 135.0° to 45.0°, and the protein adsorption of the modified membrane decreased from 112.5 to 33.3 μg⋅cm−2. Furthermore, dynamic protein separation was performed, and the pure water flux recovery rate reached 100%, indicating good anti-adsorption ability. [ABSTRACT FROM AUTHOR]

Developing high-efficiency membrane for oil and dye removal is very urgent, because wastewater containing them can cause great damage to human and environment. In this study, a coated membrane was fabricated by applying DAC and PEI onto the commercial PVDF microfiltration membrane for supplying the demand. The coated membrane presents superhydrophlic and superoleophobic properties with a water contact angle of 0o and underwater oil contact angle exceed 150°, as well as excellent low underwater oil adhesion performance. The coated membrane shows high separation efficiency exceeded 99.0% and flux 350.0 L·m−2·h−1 when used for separating for six kinds of oil including pump oil, sunflower oil, n-hexadecane, soybean oil, diesel and kerosene in water emulsions. Additionally, the coated membrane can effectively remove anionic dyes, achieving rejection rates of 94.7%, 93.4%, 92.3%, 90.7% for the CR, MB, RB5, AR66, respectively. More importantly, the membrane was able to simultaneously remove emulsified oil and soluble anionic dyes in wastewater containing both of them. Therefore, this novel coated membrane can be a promising candidate for treating complex wastewater. [Display omitted] • The DAC and PEI were applied onto PVDF membrane surface for modification. • The coated membrane was high hydrophilicity and underwater superoleophobic. • The coated membrane can be used for separating different oil water emulsions. • The coated membrane can simultaneously remove emulsified oils and anionic dyes. [ABSTRACT FROM AUTHOR]

Non-solvent-induced phase separation is a significantly important method for the fabrication of polymer membranes for water treatment. However, the rather short time of phase separation causes serious trouble for engineering repeatable and controllable surfaces, which affects the separation performances of the membranes. Here, vapor-induced phase separation (VIPS) with a broad time window for membrane formation was employed for the fabrication of polyvinylidene difluoride- graft -poly(N-isopropyl acrylamide) (PVDF- g -PNIPAM) membranes. Efforts were made to study the effects of exposure time of a liquid film to water vapor (t e), relative humidity of water vapor (RH), dissolution temperature of the polymer (T d), and other parameters on the microstructures of the obtained membranes. It can be found that membranes tend to evolve from dense/smooth to porous/rough with t e , RH , and T d , which is associated with the development of the crystallinity and the β -crystal of PVDF. Furthermore, the pure water flux of membranes with spherical-like surfaces increases significantly, despite hydrophobicity surfaces, highlighting the efficiency of the pore structure. The rough membranes were further decorated with hydrophilic β -FeOOH nanorods, which endowed the surfaces with underwater superoleophobicity, exhibiting anti-oil fouling and efficient separation for oil-in-water emulsion. Overall, the present work suggests that the VIPS process can be readily employed to construct PVDF membranes with controllable surface microstructures, which provides an excellent platform for further modification. [Display omitted] • Microstructures of membranes can be controlled effectively by VIPS. • Membranes tend to evolve from dense/smooth to porous/rough with t e , RH , and T d. • Rough membrane is used to construct underwater superoleophobic surface by loading β -FeOOH) nanorods. • The composite membranes are featured with both high flux and anti-oil fouling. [ABSTRACT FROM AUTHOR]

The increasing demand for freshwater is driving the rapid development of new water treatment materials. Furthermore, there is significant pressure to replace the toxic substances often used in membrane production with environmentally friendly, biocompatible, and natural compounds. In this work, poly(vinylidene fluoride) (PVDF) membranes were modified for the first time with a naturally occurring, non-toxic, biodegradable substance – cinnamic acid. The application of its molecules for membrane modification allows for diminishing the problem of bioaccumulation and toxicity in the environment. The procedure was selected with the accordance of green chemistry principles (green modifier – cinnamic acid, and green solvent – ethanol), and employed to chemically bind the modifier to the membrane surface. The modified membranes exhibited an increase in the hydrophobicity of the surface. The water contact angle increased from 124.7° for the pristine membrane to 139.3° for the membrane modified with a 10 % concentrated solution of cinnamic acid (PVDF-Cin10). All membranes possessed an excellent salt rejection coefficient. Membrane antiwetting features have been determined under challenging conditions of salt (3 M NaCl) and low surface tension liquid (sodium dodecyl sulfate). The dynamic goniometric studies were implemented to evolve membranes' wetting stability. [Display omitted] • New, antiwetting membranes were acquired. • Chemical attachment of natural modifier – cinnamic acid – was achieved. • Green chemistry and environmentally friendly methods were utilized. • An increase in the hydrophobicity of the modified methods was observed. • Non-toxicity of the modifier was confirmed with very low bioaccumulation potential. [ABSTRACT FROM AUTHOR]

Efforts have been made in thermally induced phase separation (TIPS) process to modify the morphology of polyvinylidene fluoride (PVDF) membranes in order to improve their permeation performance and mechanical properties. Nevertheless, many methods not only altered the outer surface but also impacted the overall membrane structure, resulting in a trade-off between permeability and mechanical properties. In this study, we utilized a modified TIPS process to refine the outer surface morphology without altering the bulk structure. This was achieved by introducing NaCl in the coagulation bath. The PVDF membranes were fabricated using a dope with water insoluble diluent dimethyl phthalate (DMP) as main solvent and water-soluble additives polyethylene glycol 400 (PEG400)/triethylene glycol (TEG) as pore formers. The inclusion of NaCl in the coagulation bath serves to decrease the solubility of PEG within this medium, owing to the salting-out effect. Consequently, the NaCl concentration in the coagulation bath emerges as a crucial factor in regulating the migration of PEG400 toward the membrane surface. This control mechanism facilitates the precise adjustment of the outer surface morphology in the fabrication of membranes. As the NaCl concentration increases in the coagulation bath, the outer surface of the fabricated membrane transited from a mesh-like structure to a spherulite structure. As 0.5 mol L−1 NaCl was added to the coagulation bath, the membranes displayed a pure water permeability of 1073.9 L m−2 h−1 bar−1 while maintaining a narrow pore size distribution. Compared to the membranes fabricated without NaCl addition, the increment of the PWP contributed to the slight increase in mean pore size from 65 nm to 84 nm. Meanwhile, the water-insoluble diluent DMP was not affected by the addition of NaCl, which means that the bulk structure of the membrane could be maintained. Consequently, the increase in permeability did not compromise the mechanical properties of the membranes. All the membranes fabricated in this study maintained a reasonable tensile strength of approximately 3 MPa. This study introduces a simple and environmental method to increase the permeability effectively and fine-tune the pore size of the TIPS membranes while having little effect on the bulk structure. Furthermore, the study provides valuable insights into how changes in outer surface morphology can impact the pore size and permeability of TIPS PVDF membranes. [Display omitted] • Ultrafiltration PVDF membranes was fabricated by a modified TIPS method. • NaCl coagulation bath could control the outflow of PEG toward membrane surface. • The surface of the membranes could be fine-tuned without altering the bulk structure. • The ultrafiltration membranes present a narrow pore size distribution and high permeability. [ABSTRACT FROM AUTHOR]

In this study, Polyvinylidene Fluoride (PVDF) nanocomposite membrane consisting of electrospun titanium dioxide (TiO2) nanofibers (PVDF/e-TiO2) was prepared by hot pressing the as-spun TiO2 nanofibers onto PVDF flat sheet membrane. The hot press technique was carried out by applying the operating pressure at 1 bar, 1.5 bar and 2 bar for 30 seconds. The nanocomposite membrane was characterized by Scanning Electron Microscope (SEM) spectroscopy. The SEM images and analysis shows good adhesion and dispersion of TiO2 nanofibers in PVDF membrane. Based on the results, it can be concluded that a fine-tuning on the optimization study of the membrane hydrophilicity by several approaches such as pure water flux, glucose rejection and contact angle is desirable in order to ensure the developed PVDF/e-TiO2 membranes can be simultaneously efficiently functioned by means of filtration applications. Membrane successfully done glucose rejection and then COD analysis is carried out with higher efficiency. As the pressure increases the chemical oxygen demand (COD) increases because dissolved oxygen is removed in retentate side together with glucose.

Tetracycline (TC) contamination in water has progressively exacerbated the environmental crisis. It is urgent to develop a feasible method to solve this pollution in water. However, polluted water often contains oil. This paper reported a glass fiber (FG)-assisted polyvinylidene fluoride (PVDF) hybrid membrane with dual functions: high TC degradation efficiency in emulsion and oil-water separation. It can meet the catalytic degradation of tetracycline in complex water. This membrane was decorated by coating the glass fiber with PVDF solution containing hydrophilic graphene oxide hybridized NH2-MIL-101(Fe) particles. Moreover, due to its strong mechanical strength enhanced by the glass fiber, it can be reused as TC degradation catalysts for dozens of times without cracking. Thanks to the hydrophobicity of PVDF and the surface pore size of MOFs, the prepared membrane showed a good oil-water separation performance. Besides, the hydrophilic graphene oxide (GO) and NH2-MIL-101(Fe) improved the membrane’s anti-fouling performance, allowing it to be reused as the separation membrane. Therefore, the outstanding stability and recoverability of the membrane make it as a fantastic candidate material for large-scale removal of TC as well as oil-water separation application.

The influence of ultrasonication on membrane performance was investigated by two ultrasonication modes, direct and indirect ultrasonication as pretreatment, and simply improved PVDF-TiO2 membranes' performance was systematically compared. Ultrasound intensity of 100% and ultrasonication time ranged from 1 to 2 h positively affect membrane permeability. Characterization results manifested that membrane structure was eventually optimized with an even nano-TiO2 dispersion by direct ultrasonication. Analysis of surface roughness reflected that PVDF-TiO2 (MS-U2) surface morphological pattern was peak-valley structure that resisted fouling greatly. A good fitting of experimental result and Tansel's simulation illustrated that anti-fouling ability was realized direct ultrasonication modified membrane. PVDF-TiO2 (MS-U2) membrane showing the lowest |τ| reflecting the time required to reach a certain level of the fouling degree was the lowest. Relying upon modified Hermia's model analysis, protein blockage within the membrane pore was one major fouling mechanism; surface blockage degree of PVDF-TiO2 (MS-U2) was relative slight. Fouling mechanism analyzed by two models reflected that PVDF-TiO2 (MS-U2) membrane exhibited a higher anti-protein fouling ability during cross-flow filtration process. [ABSTRACT FROM AUTHOR]

In order to obtain the tunable and charged surface of the membranes, polymerized ionic liquid(PIL) block copolymers poly (methyl methacrylate) (PMMA)-b-poly(1-[(2-methacryloyloxy)ethyl]-3-butylimidazoliumbromide) (PMEBIm-Br) with different poly(ionic liquid) brush lengths were synthesized by RAFT polymerization method and used in the fabrication of poly(vinylidene fluoride) blend membranes. Chemistry analysis confirmed the successful copolymerization of P(MMA-b-MEBIm-Br) with different chain lengths of PMEBIm-Br blocks, and the PIL groups was also detected on the surface of the blend membranes, which contributes to the hydrophilic and positively charged surface of the membrane. These properties were further enhanced by the chain length of PMEBIm-Br blocks in the copolymer. The surface wettability of the membranes can be regulated from hydrophilicity to hydrophobicity by anion exchange, and the water flux changes also confirmed these phenomena. In addition, the effects of PMEBIm-Br blocks on the separation properties of the membranes were investigated using two dyes, namely, orange G and rhodamine 6G. Results indicated that the blend membranes with long length of PMEBIm-Br blocks had high rejection and good antifouling property to rhodamine 6G. Furthermore, the adsorption experiment of the blend membranes to the two dyes also indicated that blend membranes with long length of PMEBIm-Br blocks would have good dye adsorption-separation property. [ABSTRACT FROM AUTHOR]

CuFe2O4 nanocrystals with the size about 60 nm were synthesized under hydrothermal conditions, and doped them into polyvinylidene fluoride (PVDF) membranes for enhancing their photocatalytic performance. The morphology, phase, and photoelectric performance of CuFe2O4/PVDF membranes were confirmed by X-ray photoelectron spectroscopic (XPS), scanning transmission microscopy (SEM), and transient photoelectrochemical analysis. As a result, the morphologies of CuFe2O4 nanocrystals could change with the concentration of NaOH solution under hydrothermal conditions. CuFe2O4 nanocrystals showed strong facet-dependent photoelectric and photocatalytic properties. PVDF membrane doped with CuFe2O4 nanocubes showed excellent photocatalytic activity of Congo red degradation (95%), and kept the good self-cleaning performance after five circles. The flux and rejection performance displayed the CuFe2O4 nanocubes/PVDF membrane kept high water flux (40 L/m2 h) and Congo red rejection (99%), and the composite membrane have good potential in water treatment applications. Highlights: CuFe2O4 nanocrystals were synthesized under hydrothermal conditions. The CuFe2O4 nanocubes showed the higher photoelectrochemical performance. The CuFe2O4 /PVDF membrane showed the better photocatalytic performance. [ABSTRACT FROM AUTHOR]