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The hydrophilic modification of poly (vinylidene fluoride) (PVDF) membrane with poly (ethylene glycol) dimethacrylate (PEGDMA) through grafting reaction for antifouling was reported. The influence of PEGDMA content, reaction temperature and time, on the structure, morphology, antifouling, and hydrophilicity of PVDF-g-PEGDMA membrane has been investigated. The PEGDMA monomers that were grafted on the surface of PVDF microfiltration membrane were confirmed by Attenuation total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), and morphology study conducted by SEM revealed the changes before and after modification. The protein adsorption, filtration performance, water content, and dynamic contact angle were used to characterize the antifouling and hydrophilicity of the modified PVDF membranes. Compared with the pristine PVDF membrane, the bovine serum albumin (BSA) adsorption on the PVDF-g-PEGDMA membrane decreased about 80%, and the water contact angle of the membrane dropped to 0°. Besides, the experimental results revealed no significant differences between the membrane samples with respect to pore size. [ABSTRACT FROM PUBLISHER]

Herein, electrospinnability of perfluorosulfonic acid (PFSA)–polyvinylidene fluoride (PVDF) blends with different ratios of PVDF were investigated in detail. A well-formed nanofiber structure can be obtained only when the minimum ratio of PVDF in the blend reaches 9%. The reason was explained by the change in the properties, such as viscosity, conductivity, and surface tension, and interconnected aggregates in the blend solutions as revealed by dynamic light scattering (DLS) and the viscoelasticity behavior. After this, the property and morphology of the PFSA–PVDF nanofibers were investigated. SEM images showed that the average diameter of the nanofibers ranged from 75 to 170 nm. Small-angle X-ray scattering (SAXS) and DSC results showed that the microstructure of PFSA and the crystallization of PVDF in the nanofiber interfered with each other, which was attributed to the interaction between the backbone of PFSA and PVDF. CA and IEC revealed that the nanofibers were highly hydrophobic. Finally, the PFSA–PVDF nanofiber membranes were evaluated as a catalyst in the esterification reaction and as a separator in Li-ion battery. It was found that PFSA/PVDF nanofiber membrane with high PFSA ratio showed higher capacity and more stable cycle performance after 100 cycles as compared to the PVDF nanofiber, which could be used as a separator in Li-ion battery. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF)/polyvinyl alcohol (PVA) ultrafiltration (UF) membranes were prepared via a phase inversion method employing the modification of carboxylated multiwalled carbon nanotubes (MWCNTs-COOH). Various contents of MWCNTs-COOHs (0.00-0.15 wt%, weight of casting solution) were added into PVDF/PVA/dimethyl sulfoxide systems for the fabrication of the plate UF membrane. Fourier transform infrared spectroscopy spectra identified the successful introduction of carboxyl through the CO peak at 1730 cm−1. Scanning electron microscopy images exhibited the external surface and the asymmetric morphology with the appearance of a sponge-like inner structure. Atomic force microscopy analysis determined the roughness values and rougher topography. The hydrophilicity of the composite membrane containing 0.09 wt% of MWCNTs-COOHs improved the most. This sample has the highest pure water flux, approximately doubled (126.6 L·m−2·h−1) compared to the PVDF/PVA membrane (68.6 L·m−2·h−1), an enhanced bovine serum albumin flux recovery rate, showing an increase of 17%, and the best fouling resistance ability. Meanwhile, the porosity and dynamic contactangle also indicate the enhancement of membrane hydrophilicity. Dextran (DEX) 600k rejection reached 91.0%. Break strength, elongation at break, and Young's modulus also had improvements of 60%, 215.5%, and 56.7%, respectively, when the MWCNTs-COOH content was 0.12 wt%. POLYM. ENG. SCI., 56:955-967, 2016. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

We develop a novel polyvinylidene fluoride (PVDF) hollow fiber membrane utilizing the concept of in-situ self-assembly modulation, which is in terms of in-situ synthesis of amphiphilic copolymers and in-situ solubilization of polyvinylpyrrolidone (PVP). Utilizing the polytetrahydrofuran dimethacrylate ester (PTMGDA) and polyethylene glycol monomethyl ether methyl methacrylate (PEGMA) as reaction monomers, amphiphilic copolymers are in-situ synthesized, denoted as “P(PTMGDA-r-PEGMA)”. Results show that P(PTMGDA-r-PEGMA) and PVP have the synergistic effects on configuration and separation performance of PVDF membrane. P(PTMGDA-r-PEGMA) with high ratio in hydrocarbon chain (75.2%) and PVP not only effectively tunes micro-structure of the dope solutions but also results in the enhancement of the resultant membranes’ break strength and their stable permeability. Besides, the supramolecular aggregates of PVDF-P(PTMGDA-r-PEGMA)–PVP (size: 76–157 nm) work as “template” dependence of the macrovoids, which appear in the fibers׳ sponge-like cross-section structure, hence leading to the narrowing pore size distribution. Furthermore, the macrovoids’ size enlarges with the increase of content of P(PTMGDA-r-PEGMA) and PVP. It is also found that the permeation flux is controlled by the diffusion of PVP from the interior dope solution and pore-forming of P(PTMGDA-r-PEGMA) during demixing process, which is consistent with the in-situ self-assembly modulation concept. Finally, the newly developed PVDF hollow fiber membranes demonstrate remarkable long-term stable permeability. [ABSTRACT FROM AUTHOR]

In this present study, the facile approaches of coagulants and in situ free radical polymerization method for modulating configurations and performances of polyvinylidene fluoride (PVDF) membranes are investigated. Configuration images show that the supramolecular aggregates of PVDF-P(PEGMA-r-MMA) caused by in situ polymerization act as "template" of the tuned configurations of the resultant PVDF membranes. During delay demixing process (ethanol coagulant), the confine of the aggregates resulted in shift of the cauliflower nanograins to the stripe-type nanograins. On the other hand, for the membranes prepared from the instantaneous demixing process in water coagulant, the aggregates contributed to the formation of the confined finger-like structures and the globule agglomerates that constructed the whole thickness of the membrane bulk. Furthermore, those narrow distribution supramolecular aggregates and variation coagulants (water and ethanol) also yield the tuned performances. The membranes' improved mechanical properties and limited hydrophilicity improvement are attributed to the strong interconnection between the aggregates. Because of the fore-forming of the P(PEGMA-r-MMA) aggregates with narrow distribution, all PVDF membranes prepared from the two coagulants possess enlarged flux, narrow distributionmean effective pore size (µ), andmolecular weight cut-off. The delay demixing process contributes to the narrower µ andmolecular weight cut-off, as well increased flux. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF) flat-sheet membranes were prepared via a non-solvent-induced phase separation (NIPS) method at 60°C using a hydrophilic surfactant OP-10 (octylphenol polyoxyethylene ether) solely (Blank) or with a second additive [H2O or lithium chloride (LiCl)] as pore-forming agents. The influence of OP-10 concentration on the surface tension, viscosity, and precipitation rate of PVDF/(H2O, LiCl, or Blank) systems were investigated, and the ultrafiltration and mechanical properties of the resultant membranes were measured. It was found that an increased demixing rate during the coagulation process was the reason for the change in membrane morphology and properties. An obviously improved flux and slightly decreased mechanical properties and rejection were found in membranes prepared using a high concentration of OP-10 and the second component as additives. SEM pictures revealed an increased porous structure on the resultant membrane surface. A hypothesis was proposed to explain these phenomena; the reoriented surfactant molecules at the interface facilitated the water diffusion channels, which finally became the porous structure on the membrane surface. The weakened mechanical properties were due to the macrovoid structure in its membrane cross-section, which developed from the micelle structure in the casting solution. This hypothesis was further confirmed in a PVDF/OP-10/polyethylene glycol (PEG) system. Aconsistent conclusion was obtained. [ABSTRACT FROM AUTHOR]

ABSTRACT Poly(vinylidene fluoride) (PVDF) membranes were prepared with various residence times using water-ethanol (50 : 50, mass ratio) and pure ethanol coagulants as first coagulant, respectively. The physical properties of PVDF solution after free radical polymerization were investigated by dynamic light scattering (DLS), scanning electron microscopy (SEM), viscosity, precipitation kinetics, and surface tension. Resultant PVDF membranes were characterized by SEM, contact angle, mechanical properties, and filtration properties. The results showed that the longer residence time in the first coagulant contributed to the filtration properties improvement. Contact angles of the top-surfaces and bottom-surfaces of membranes decreased as residence time increasing in the first coagulant, and the top-surface showed better hydrophilicity than that of the bottom-surface. The pore size distributions of PVDF membranes showed that the dominating demixing process of the casting solution in water-ethanol coagulant was 5 s, and in that of ethanol was 10-15 s. Additionally, the short-time delay demixing process in water-ethanol first coagulant resulted in a thin dense layer near the top surface, and the longer time delay demixing process in that of ethanol contributed to the shift of the inter-globules to the cellular morphology in the case of the residence time increasing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39987. [ABSTRACT FROM AUTHOR]

Abstract: In situ free radical polymerization was proven to be successful for the preparation of PVDF membranes with superior mechanical behaviors and enhanced antifouling properties. Micro-structure adjustment of PVDF solution via in situ polymerization was investigated by dynamic light scattering (DLS) and scanning electron microscopy (SEM). The DLS and SEM results verified the formation of supramolecular polymer–copolymer aggregates. The narrow distribution of the supramolecular aggregates explained the decreasing surface tension, increasing viscosity with trivial strain thinning behavior and accelerating precipitation rate of the PVDF casting solution. The resultant PVDF membranes possessed narrowly distributed pore size and molecular weight cut off (MWCO) of the final filtration properties, which were attributed to the aggregates; additionally, their corresponding mean effective pore size (μ) and MWCO increased with increasing concentration of the monomers via in situ polymerization. Further, in situ polymerization not only enlarged the recovery water flux after filtration experiments with bovine serum albumin (BSA) but also improved the hydrophilicity of both the top-surface and the bottom-surface of the PVDF membranes. Additionally, in situ polymerization modulated the PVDF membrane configurations, varying from stripe-shaped grains to agglomerates of globule (with one of the globules bearing on the surface of another). The tunable morphologies, combined with the progressive enhanced crystallinity of the α and β phase (largely in the β phase form), were used to interpret the superior mechanical properties of the resulting PVDF membranes. [Copyright &y& Elsevier]

Abstract: P(PEGMA-r-MMA) amphiphilic copolymer with Mn of 66,500g/mol and Mw of 34,200g/mol was successfully synthesized via free radical polymerization. And polyvinylidene fluoride (PVDF)-P(PEGMA-r-MMA) blend membranes were fabricated from water and ethanol coagulants via simplified blend method by directly blending PVDF and P(PEGMA-r-MMA) amphiphilic copolymer solution (including the reaction mixture) to form casting solution. The formation of the supramolecular aggregates in PVDF solution containing the copolymer were confirmed by dynamic light scattering and scanning electron microscopy. This contributed to the micro-structure adjustment of PVDF solution and resulted in its decreasing surface tension, accelerating precipitation rate and increasing viscosity with trivial strain thinning behavior. Furthermore, the effects of the variations in dopant contents and coagulant compositions on the performances of those blend membranes were investigated. All PVDF-P(PEGMA-r-MMA) blend membranes possessed narrow distribution mean effective pore size (μ), molecular weight cut off (MWCO), improved recovery water flux after filtration experiments of bovine serum albumin and tuned configurations. Compared with the instantaneous demixing process in water coagulant, the delayed demixing process in ethanol favored the pore-forming and surface segregated of the polar head group of the copolymer, which induced the increasing μ, MWCO, tunable morphologies and hydrophilicity improvement. [Copyright &y& Elsevier]

The effects of nucleating agents on the morphology and performance of poly(vinylidene fluoride) (PVDF) microporous membranes via thermally induced phase separation were investigated. The nucleating agents studied were dicyclohexyl benzene amide (TMB-5), 2,2-methylene bis(4,6-tertiary butyl phenol) sodium phosphate (TMP-1), and 1,3 : 2,4-di- p-methylbenzylidene sorbitol (DM-LO). Light transmittance experiments and differential scanning calorimetry (DSC) were performed to obtain phase diagrams of PVDF/tributyl citrate/di(2-ethylhexyl) phthalate/nucleating agent doped solutions. The morphology and performance of the prepared PVDF microporous membranes were characterized with scanning electron microscopy and microfiltration experiments. The results show that the thermodynamics of liquid-liquid phase separation were not affected by the addition of the nucleating agents, but solid-liquid phase separation was influenced. The system with 0.3 wt % TMB-5 had the fastest crystallization rate and a better nucleation ability. The PVDF microporous membranes had a partly closed, lacy bicontinuous structure with TMP-1 and DM-LO, whereas the membrane with 0.3 wt % TMB-5 had an interconnected bicontinuous structure. The pore size distribution became narrower with the addition of nucleating agent. With 0.3 wt % TMB-5, the membrane had the minimum mean pore size (0.095 μm), a porosity of 80.3%, and a pure water flux of 270 L·m−2·h−1; these values were higher than those of the pure PVDF membrane. The performances of the membranes decreased with additions of TMB-5 of greater than 0.3 wt %. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride) (PVDF) membranes possessing interconnected bicontinuous structures with superior mechanical properties and improved hydrophilicity were obtained from PVDF/ N, N-dimethylacetamide (DMAc)/Tween 80/water systems via non-solvent induced phase separation (NIPS) with 60 °C and ambient temperature casting solution. Tween 80/HO mixtures were adopted as dopant; water/ethanol (50:50, mass ratio) and ethanol were chosen as coagulants. The effects of process parameters in terms of variations in dopant contents, casting solution temperatures, and coagulant compositions on the phase inversion process and performance of the resultant membranes were investigated. During the demixing process, water diffused from the interior of Tween 80 reverse micelles, resulting in an accelerated precipitation rate and surface segregation process of the polar head groups of Tween 80. The high temperature of the casting solution contributed to enhancing the diffusion rate of liquid-liquid demixing on crystallization. The coagulant compositions changed the liquid-liquid and solid-liquid demixing dynamics of the casting solutions. Ethanol coagulant contributed to crystallization of PVDF/DMAc/Tween 80/water systems prior to liquid-liquid demixing. This delayed demixing process favored the formation of porous foliage-type top structures with fibril or lath bicontinuous fine structure of membrane bulk, increasing flux, and significant hydrophilicity improvement. Casting solutions in water/ethanol coagulant exhibited a less delayed demixing process with both liquid-liquid demixing and crystallization, resulting in formation of fine structure in the form of strings or stripes and limited hydrophilicity improvement. The predominant typical α- and β-type crystallinity in PVDF was attributed to the existence of dopants, the high temperature of the casting solution, and water/ethanol coagulant. This was consistent with the superior mechanical properties of the corresponding PVDF membrane. The newly developed hydrophilic PVDF membranes with superior mechanical properties and low-fouling of bovine serum albumin (BSA) are anticipated to be suitable not only for wastewater treatment, but also for bioseparation. [ABSTRACT FROM AUTHOR]

Using the mixture of triethyl phosphate (TEP) and N, N-dimethylacetamide (DMAc) as solvent, PVDF microporous membranes with highly hydrophobic surface were prepared by a modified NIPS method with a dual coagulation process. The effects of the exposure time on these membranes before being immersed into the coagulation bath and the composition in the coagulation bath on precipitation rate, membrane morphology, membrane hydrophobicity, membrane mechanical property, and membrane performance were studied. The morphologies and hydrophobicities of PVDF microporous membranes were investigated by scanning electron microscopy (SEM) and contact angle (CA) measurement. The precipitation processes were observed by light transmittance measurement. The pore size distribution was determined by liquid permeation technique. PVDF microporous membrane obtained by passing evaporation period of 60 min before being immersed into the water bath showed a high water CA of 122.1°. Using ethanol (EtOH) as coagulation bath, the water CAs of the top surface and bottom surface of the membrane increased to 125.9 and 132.6°, respectively. To further improve PVDF membrane hydrophobicity, a dual coagulation process was used and the mixed solvent (TEP-DMAc) was added into the first coagulation bath for 30 sec. Increase in the TEP-DMAc content led to the change in the morphology type of the membrane, that is, from an asymmetric structure with a dense top surface to a symmetric structure with a skinless top surface, and the pore size distribution widened greatly. By increasing the mass ratio of TEP to DMAc, the denseness of the membrane surface decreased significantly. Adding 60 wt% of TEP-DMAc to the first coagulation bath and the mass ratio of TEP to DMAc was 60:40, the CA reached to a maximum as high as 136.6°, and PVDF microporous membrane showed a high porosity of 80% and an excellent mechanical property of 3.14 MPa tensile strength and 61.79% elongation ratio. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Polyvinylidene fluoride (PVDF)–perfluorosulfonic acid (PFSA) hollow fiber ultrafiltration blend membranes were prepared by wet-spinning method. The effects of PVDF–PFSA and ethanol concentrations on the structure morphology and performance of blend membranes were investigated. The coagulation kinetics was studied by light transmittance experiments. Blend membranes were characterized in terms of morphology, pore size distribution, molecular weight cut-off, water permeation flux and rejection. The wetting and fouling properties of blend membranes were also examined. Based on the experimental results, more sponge-like structures existed in the cross section of the blend membrane prepared from the dope solution with the increase in PVDF concentration, but the membrane showed a worse permeation performance. The increase of PFSA resulted in the formation and development of the finger-like voids. It was also found that the finger-like macrovoids began growing up inside the nascent membrane. Such changes were proved by scanning electron microscopy (SEM). By introducing different concentrations of ethanol from 1 to 5wt.% in PVDF–PFSA dope solution, thinner and more uniform finger-like voids appeared through the cross section, the pure water permeation flux, the mean effective pore size, molecular weight cut-off were increased. PVDF–PFSA hollow fiber UF blend membranes with low-molecular weight cut-off around 10,000Da were obtained and the morphology was elaborately controlled. [Copyright &y& Elsevier]

Abstract: Organic–inorganic polyvinylidene fluoride (PVDF)–silica (SiO2) composite hollow fiber ultrafiltration (UF) membranes were prepared by the combination of a tetraethoxysilane (TEOS) sol–gel process with a wet-spinning method. The membrane formation mechanisms were investigated in terms of viscosity, precipitation kinetics and morphology. Results showed the dope viscosity increased with the increment of TEOS concentration in dope. The addition of TEOS accelerated the precipitation of the dope. SEM pictures showed the cross-section morphology of PVDF composite membranes changed from finger-like macrovoids to sponge-like structure with increasing SiO2 content. The mechanical, thermal stabilities and permeation property of PVDF–SiO2 composite membranes were further examined. At lower TEOS concentration, the hydrolyzed SiO2 particles, which were homogeneously dispersed in PVDF matrix, acted as the physical crosslinking points, and led to an improvement of mechanical and thermal properties. While at higher TEOS concentration, SiO2 formed network, which restricted the movement of PVDF and led to the decrease of the mechanical and thermal stabilities. Moreover, XRD and FTIR results revealed that the crystal structure of PVDF underwent a transition from α-phase to β-phase due to the addition of TEOS. The contact angle and UF experimental results of PVDF–SiO2 composite membranes showed an improvement of hydrophilicity and permeability. The PVDF–SiO2 membrane prepared from the dope with 3wt.% TEOS concentration had the best UF performance and antifouling property. [Copyright &y& Elsevier]

Abstract: An improved process to prepare high separation performance polyamide (PA)/polyvinylidene fluoride (PVDF) hollow fiber composite nanofiltration (NF) membranes was presented. Conventional interfacial polymerization process to prepare composite NF membranes was done through submerging the support membrane in aqueous phase followed by in oil phase. The improved interfacial polymerization process was done by submerging the membrane into aqueous phase again after the conventional process. The experiment was done to prepare PA NF membrane on PVDF hollow fiber support membrane. Results showed that the membrane prepared through this improved process had better separation performance. Using this improved process, membrane structures were improved and the rejections of PA/PVDF hollow fiber composite NF membranes for Na2SO4, MgCl2, KCl, NaCl, PEG600 and PEG1000 were 92.3%, 7.0%, 9.5%, 14.2%, 88.4% and 89.3%, respectively. [Copyright &y& Elsevier]

Abstract: Polyvinylidene fluoride (PVDF)–perfluorosulfonic acid (PFSA) blend hollow fiber ultrafiltration (UF) membranes were prepared by wet-spinning method using pure water as an external coagulation solution. Coagulation kinetics of PVDF–PFSA–DMAc system was measured by light transmittance experiment. Using PEG10000 (M w =10,000), lysozyme (M w =14,400), PEG20000 (M w =20,000) and BSA (M w =67,000), the separation performances of PVDF–PFSA blend hollow fiber UF membranes were obtained. Based on the experimental results, the delayed demixing process was observed for the dope solution M-1 without PFSA-H while the instantaneous demixing process was observed for the others with PFSA-H in the dope solutions M-2 to M-6. The precipitation rate increased with the increment of the PFSA-H concentration in PVDF–PFSA dope solution. The bore fluid solution with 95:5 DMAc:H2O resulted in single finger-like voids for PVDF–PFSA-H UF membrane. The pure water permeation flux of PVDF–PFSA-H UF membranes firstly increased from <0.1×10−5 to 119.1×10−5 Lm−2 h−1 Pa−1 (<0.1 to 119.1Lm−2 h−1 bar−1) for M-1 to M-4(1) and 137×10−5 Lm−2 h−1 Pa−1 (137Lm−2 h−1 bar−1) for M-4(2), and decreased from 119.1×10−5 to 79×10−5 Lm−2 h−1 Pa−1 (119.1 to 79Lm−2 h−1 bar−1) for M-4(1), M-5 and M-6 as the PFSA-H concentration changed from 0% to 5% and total PVDF–PFSA-H concentration was 20wt.%. The molecular weight cut-off (MWCO) of PVDF–PFSA blend hollow fiber UF membranes spun from 20wt.% PVDF–PFSA-H concentration with 3–5wt.% PFSA-H was about 20,000 while that spun from 22wt.% PVDF–PFSA-H or PVDF–PFSA-Na concentration with 5wt.% PFSA-H or PFSA-Na was about 10,000. As the W PFSA-H/W PVDF increases from 2/18 to 5/15 for M-3–M-6, J BSA/J w increases from 0.53 to 0.79. The anti-fouling property of PVDF–PFSA-H blend UF membrane is superior to PVDF–PFSA-Na blend membrane. Based on FTIR spectra, PFSA-H existed in PVDF–PFSA blend hollow fiber UF membranes. There is no obvious variation of the intensity of the characteristic peak at 983cm−1 assigned to C–O–C group of PFSA-H molecules. This also illustrated that PVDF–PFSA-H blend hollow fiber UF membranes were stable. [Copyright &y& Elsevier]

In this study, a superhydrophobic nanofibrous membrane was prepared on the basis of an electrospun polyvinylidene fluoride (PVDF)–polytetrafluoroethylene (PTFE) nanofibrous scaffold coupled with a microporous PTFE substrate. The PVDF–PTFE nanofibrous scaffold was fabricated by electrospining of PVDF–PTFE blend solutions, it was observed that by changing the PTFE micro-powder content in the dope solutions from 0wt.% to 12wt.%, the water contact angle (WCA) and the liquid entry pressure (LEPw) of the membrane vary from 130.4° and 84kPa to 152.2° and 137kPa, respectively. The superhydrophobic PVDF–PTFE nanofibrous membrane was then tested for desalination by vacuum membrane distillation (VMD), a stable flux of 18.5kg/m2 h and salt rejection higher than 99.9% was presented throughout the entire testing period of 15h, indicating the great potential of the PVDF–PTFE nanofibrous membranes in VMD. For further application of the PVDF–PTFE nanofibrous membranes in VMD, a mathematical model was presented to predict the vapor flux of the novel membrane under various operation conditions. A good agreement between the experimental and theoretical values for vapor fluxes was obtained; the results indicated that the VMD flux increased with the increase of feed temperature and flow rate and decreased with the increase of permeate pressure. [ABSTRACT FROM AUTHOR]

• Carbon nanofiber with multilevel gradient porous structure is prepared. • Porous carbon nanofiber shows a specific capacitance of 331 F/g at 1 A/g. • Supercapacitor device possesses an energy density of 13.1 W h/kg. • CO 2 uptake of the prepared CNF at 0 °C and 1 bar is 5.08 mmol/g. In this work, we demonstrate a simple method to prepare carbon nanofiber (CNF) with multilevel gradient porous structure derived from polyvinylidene fluoride (PVDF)- polyvinyl pyrrolidone (PVP) /PVP core-shell nanofiber. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have confirmed that the as-prepared CNF contains a hollow channel embraced by mesoporous and microporous structures. Its specific surface area reaches to 1084 m2/g with the mesoporous volume contribution of 59%. The as-prepared porous CNF shows a high capacitance of 331 F/g at 1 A/g and 99.6% capacitance retention after 10,000 cycles at 5 A/g, which is better than the corresponding CNF with irregularly arranged hierarchical pores. The all-solid-state symmetric supercapacitor assembled using the as-prepared porous CNF as electrodes exhibits an excellent high specific capacitance of 147.4F/g at 1 A/g with a high energy density of 13.1 W h/kg. The capacitance retention still maintains at 89.2% after 2000 cycles at a current density of 5 A/g. Meanwhile, the as-prepared porous CNF also shows a high CO 2 adsorption uptake, 5.08 mmol/g at 0 °C and 1 bar. The possible reason and mechanism have been discussed. [ABSTRACT FROM AUTHOR]

A simply method to fabricate novel Metal-Organic Frameworks (MOFs)-polymer composite crystals with different morphologies was proposed firstly in the present study which were prepared via polymer-aid solvothermal (PAS) method by using commercially available polyvinylidene fluoride (PVDF) powder. The as-synthesized Zeolitic Imidazolate Framework 8 (ZIF-8)-PVDF composite crystals (ZIF-8-PVDF) were investigated systematically using different PVDF contents in the reaction solution. The results showed that the composite crystal transformed gradually from dodecahedron morphology with micropores to a hexagonal plate shape with the pores ranged in mesoporous scale. Carbon dioxide (CO 2 ) adsorption capacity was evaluated and demonstrated that the increasing PVDF content has a significant contribution to the molecular adsorption performances of the composite crystals accompanied with decreased specific surface area. [ABSTRACT FROM AUTHOR]

The modified membrane GO-Ag/PVDF was fabricated using co-polymer F127 and nanocomposite GO-Ag as functional additives via non-solvent induced phase separation (NIPS) method for natural organic matter (NOM) resistance. Due to the introduction of co-polymer F127 and nanocomposite GO-Ag, resultant membranes exhibited excellent hydrophilicity and permeability. Meanwhile, the modified membrane surface showed better fouling resistance to natural organic matter (NOM) and bacteria compared with pristine membrane. In summary, the membrane MF1825 under the optional additive combination possessed the better performance with pure water flux of 82 L·m −2 ·h −1 and the contact angle of 62° comparing the membrane MF1800 with pure water flux of 14 L·m −2 ·h −1 and the contact angle of 80°. In addition, the membrane MF1825 had the improved fouling resistance order to NOM models: BSA > SA > HA, which indicated a potential application in natural organic water treatment. [ABSTRACT FROM AUTHOR]

ZIF-8 modification can reduce aggregation of ZnO (a typical photocatalyst), and enhances antifouling property of PVDF membranes. In this study, we developed a novel membrane by adding ZnO@ZIF-8 nanoparticles into polyvinylidene fluoride (PVDF) substrates by using non-solvent induced phase separation (NIPS) method. Filtration test with bovine serum albumin (BSA) showed that the modified membrane has good pure water flux (395 L m−2 h−1, PWF) and high flux recovery rate (94%, FRR). Furthermore, the SiO 2 :ZnO@ZIF-8 membrane showed high separation effect in 4-NP degradation test under light condition, with the flux achieved about 321 L m−2 h−1 during filtration process. The degradation efficiency reached 81.5%, the apparent rate constant (Kapp/min−1) was 0.211 min−1. Besides, in prolonged 4-nitrophenol (4-NP) degradation test, the SiO 2 :ZnO@ZIF-8 membrane maintained higher flux and degradation rate. Thus, we reported a novel membrane with a prominent antifouling property. • ZIF-8 modification can reduce the aggregation of ZnO and enhances antifouling property of PVDF membranes. • Modified membrane flux was 395 L·m-2·h-1(PWF) and high flux recovery rate (94 %, FRR). • ZnO@ZIF-8 and SiO 2 modified PVDF UF membrane showed high separation performance in 4-NP degradation, high 4-NP removal rate and long-term stability under light condition. [ABSTRACT FROM AUTHOR]

Superhydrophilic and ultrafine polyvinylidene fluoride (PVDF) electrospun nanofibrous membranes (ENMs) were successfully fabricated by electrospinning based on an in situ free radical polymerization. The properties of electrospinning solution were investigated, as well as the morphologies and hydrophilicity of ENMs. The results showed that PVDF ENMs with in situ free radical polymerization had high porosities and rough surfaces endowing their surfaces superhydrophilicities. The water contact angle reduced from 135° to 0° within 0.2 s. [ABSTRACT FROM AUTHOR]

Abstract: The impact of chemical treatment on the poly(vinylidene fluoride)/perfluorosulfonic acid (PVDF/PFSA) hollow fiber ultrafiltration membranes in acid, alkali and hypochlorite solutions was contrastively studied with PVDF/polyvinylpyrrolidone(PVP) ultrafiltration membranes. The morphologies, surface properties, permeation performances, antifouling ability and mechanical properties of the membranes were characterized by numerous state-of-the-art analytical techniques. The results reveal that the chemical treatment has less effect on the PVDF/PFSA membranes than on the PVDF/PVP membranes. After treating with alkali and hypochlorite solutions, the surface hydrophilicity of PVDF/PFSA membranes increases, while the surface hydrophilicity of PVDF/PVP membranes decreases. In comparison with the original membranes, the antifouling ability of the PVDF/PFSA membranes is improved, while the antifouling ability of the PVDF/PVP membranes declines. Compared with the chemically treated PVDF/PVP membranes, the treated PVDF/PFSA membranes are more easily regenerated after fouling. The chemical treatments lead to the decline of the mechanical strength in different degrees for both PVDF/PFSA and PVDF/PVP membranes. Nevertheless, this influence on PVDF/PFSA membranes is evidently less severe than on PVDF/PVP membranes. [Copyright &y& Elsevier]

• The nanohybrid particle (SnO 2 -GO) was first added in membrane. • SnO 2 -GO/PVDF membranes have complete sponge-like pore morphology. • SnO 2 -GO/PVDF membrane indicated the lowest flux attenuation (lessened only 20.2%) under UV light. • The rejection rate of BSA exceeded 97.2% under high water flux (363.2 L m−2 h−1). • UV cleaning of membranes enabled high recovery (96.1%) of SnO 2 -GO/PVDF membrane. Excellent separation performance and anti-contamination of novel SnO 2 -graphene oxide/polyvinylidene fluoride (SnO 2 -GO/PVDF) membranes with complete sponge-like pores were produced by the delay phase conversion method via introducing the nanocomposite (SnO 2 -GO) into casting solution of PVDF, in which the interconnection of SnO 2 and GO was able to improve photocatalysis capacity and entrust modified membranes with self-cleaning capability. The SnO 2 -GO/PVDF membranes exhibited enhanced effectiveness of photodegradation (increased approximately 60-80%) and superb photodegradation kinetics to bovine serum albumin (BSA) in comparison with modified membranes replenished with GO and SnO 2 , respectively. Furthermore, the BSA rejection and permeation of SnO 2 -GO/PVDF membranes were also superior over other check samples on account of the enhanced hydrophilicity, special sponge-like pore structure and photodegradation capacity. Besides, the rejection rate of BSA attached breathtaking 97.2% under high flux (363.2 L m−2 h−1). Hence, the SnO 2 -GO/PVDF membranes could possess ample potentiality as the younger generation of multifunctional antipollution membranes for water treatment in the foreseeable future. [ABSTRACT FROM AUTHOR]