Nano SiO2 and TiO2 embedded polyacrylonitrile/polyvinylidene fluoride ultrafiltration membranes: Improvement in flux and antifouling properties

Polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) ultrafiltration (UF) membranes are widely used in drinking water and wastewater applications. These membranes are prone to fouling and membrane efficiency decreases with time under constant operation. Significant improvements/modifications are necessary to apply these polymers as sustainable membrane materials. In this study, PVDF and PAN UF membranes were modified through incorporation of nanoparticles (NPs) namely SiO₂ and TiO₂. PVDF and PAN UF membranes were prepared by phase inversion method from polymer solutions having dispersed SiO₂ and TiO₂ NPs in it. Membrane surface hydrophilicity, charge, roughness, and morphology were studied. Equilibrium water content and molecular weight cut-off of the membranes were also measured. Addition of NPs increased membrane surface hydrophilicity, equilibrium water content, and surface potential. NPs modified membranes exhibited better membrane flux (35–79% higher) and antifouling properties (flux recovery ratio values 28–41% higher) than the virgin membranes.     

Synthesis and characterization of low content of different SiO2 materials composite poly (vinylidene fluoride) ultrafiltration membranes

A comparison of the morphology and performance of virgin poly (vinylidene fluoride) (PVDF) ultrafiltration (UF) membrane, and PVDF-composite membranes with low content of two different SiO₂ (N-SiO₂ and M-SiO₂ particles) was carried out. Cross-sectional area and surface morphology of the membranes were observed by scanning electron microscopy and atomic force microscopy. Surface hydrophilicity of the porous membranes was determined through the measurement of a contact angle. Performance tests were conducted on the composite membranes through water flux and bovine serum albumin (BSA) retention. Average pore size and surface porosity were calculated based on the permeate flux. Thermal stability and mechanical stability were determined by thermogravimetric analysis and tensile stress tests. The results indicate that N-SiO₂/PVDF (P-N) membranes possessed larger average pore size and porosity, which led to higher water flux and a slight decline in BSA retention. On the other hand, M-SiO₂/PVDF (P-M) membranes had better mechanical stability and anti-fouling performance with enhanced membrane hydrophilicity and decreased membrane surface roughness. Both of the P-N and P-M membranes exhibited typical asymmetric morphology and improved thermal stability.     

Preparation and characterization of a novel hydrophilic PVDF/PVA UF membrane modified by carboxylated multiwalled carbon nanotubes

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     

Studies on the surface properties of mixed‐matrix membrane and its antifouling properties for humic acid removal

A major factor limiting the use of ultrafiltration (UF) membrane in water treatment process is the membrane fouling by natural organic matter such as humic acid (HA). In this work, neat PVDF and PVDF/TiO₂ mixed‐matrix membranes were prepared and compared in terms of their antifouling properties. Two commercial types of TiO₂ namely PC‐20 and P25 were embedded to prepare the mixed matrix membranes via in situ colloidal precipitation method. The contact angles for the mixed‐matrix membranes were slightly reduced while the zeta potential was increased (more negatively charged) compared with the neat membrane. Filtration of HA with the presence of Ca²⁺ demonstrated that mixed‐matrix membrane could significantly mitigate the fouling tendency compared with the neat membrane with flux ratio (J/J₀) of 0.65, 0.70, and 0.82 for neat PVDF membrane, PVDF/TiO₂ mixed‐matrix membrane embedded with P25 and PC‐20, respectively. PC‐20 with higher anatase polymorphs exhibited better antifouling properties due to its hydrophilicity nature. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fouling behavior of poly(vinylidene fluoride) (PVDF) ultrafiltration membrane by polyvinyl alcohol (PVA) and chemical cleaning method

Severe fouling to poly(vinylidene fluoride) (PVDF) membrane is usually caused as filtrating the papermaking wastewater in the ultrafiltration (UF) process. In the paper, fouling behavior and mechanism were investigated, and the low-concentration polyvinyl alcohol (PVA) contained in the sedimentation tank wastewater was found as the main foulant. Consequently, the corresponding cleaning approach was proposed. The experiment and modeling results elaborated that the fouling mode developed from pore blockage to cake layer along with filtration time. Chemical cleaning conditions including the composition and concentration of reagents, cleaning duration and trans-membrane pressure were investigated for their effect on cleaning efficiency. Pure water flux was recovered by over 95% after cleaning the PVDF membrane using the optimal conditions 0.5 wt% NaClO (as oxidant) and 0.1 wt% sodium dodecyl benzene sulfonate (SDBS, as surfactant) at 0.04 MPa for 100 min. In the chemical cleaning method, hypochlorite (ClO⁻) could first chain-scissor PVA macromolecules to small molecules and SDBS could wrap the fragments in micelles, so that the foulants were removed from the pores and surface of membrane. After eight cycling tests, pure water flux recovery maintained above 95% and the reused membrane was found intact without defects.     

Hydrophilic modification of poly(vinylidene fluoride) membrane with poly(vinyl pyrrolidone) via a cross‐linking reaction

A highly hydrophilic hollow fiber poly(vinylidene fluoride) (PVDF) membrane [PVDF‐cl‐poly(vinyl pyrrolidone) (PVP) membrane] was prepared by a cross‐linking reaction with the hydrophilic PVP, which was immobilized firmly on the outer surface and cross‐section of the PVDF hollow fiber membrane via a simple immersion process. The cross‐linking between PVDF and PVP was firstly verified via nuclear magnetic resonance measurement on PVP solution after cross‐linking. The hydrophilic stability of the modified PVDF membrane was evaluated by measuring the pure water flux after different times of immersion and drying. The anti‐fouling properties were estimated by cyclic filtration of protein solution. When the cross‐linking time was as long as 6 hr and the PVP content reached 5 wt %, the pure water flux (J_v) was constant as ～ 600 L m^?2 hr^?1. The hydrophilicity of the PVDF‐cl‐PVP membrane was significantly enhanced and exhibited a good stability. The PVDF‐cl‐PVP membrane showed an excellent anti‐protein‐fouling performance during the cyclic filtration of bovine serum albumin solution. Therefore, a highly hydrophilic and anti‐protein‐fouling PVDF hollow fiber membrane with a long‐term stability can be prepared by a simple and economical cross‐linking process with PVP. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fouling behavior of poly(vinylidene fluoride) (PVDF) ultrafiltration membrane by polyvinyl alcohol (PVA) and chemical cleaning method

Severe fouling to poly(vinylidene fluoride) (PVDF) membrane is usually caused as filtrating the papermaking wastewater in the ultrafiltration (UF) process. In the paper, fouling behavior and mechanism were investigated, and the low-concentration polyvinyl alcohol (PVA) contained in the sedimentation tank wastewater was found as the main foulant. Consequently, the corresponding cleaning approach was proposed. The experiment and modeling results elaborated that the fouling mode developed from pore blockage to cake layer along with filtration time. Chemical cleaning conditions including the composition and concentration of reagents, cleaning duration and trans-membrane pressure were investigated for their effect on cleaning efficiency. Pure water flux was recovered by over 95% after cleaning the PVDF membrane using the optimal conditions 0.5 wt% NaClO (as oxidant) and 0.1 wt% sodium dodecyl benzene sulfonate (SDBS, as surfactant) at 0.04 MPa for 100 min. In the chemical cleaning method, hypochlorite (ClO^-) could first chain-scissor PVA macromolecules to small molecules and SDBS could wrap the fragments in micelles, so that the foulants were removed from the pores and surface of membrane. After eight cycling tests, pure water flux recovery maintained above 95% and the reused membrane was found intact without defects.     

PEG/GO/TiO2纳米复合材料改性PVDF膜的制备及其抗污性能

为改善聚偏氟乙烯(PVDF)膜的抗污性能,以聚乙二醇2000接枝的GO/TiO₂(PEG/GO/TiO₂)纳米复合材料为添加剂,通过非溶剂诱导沉淀相分离法制备了一系列PEG/GO/TiO₂/PVDF复合超滤膜。采用FTIR、SEM和接触角测试仪对其结构和形貌进行了表征,采用超滤法评价其纯水通量和抗污性能。结果表明,当PEG/GO/TiO₂纳米复合材料质量分数为0.60%时,制备的PEG/GO/TiO₂/PVDF复合超滤膜(记为0.60%PEG/GO/TiO₂/PVDF)表现出最佳的亲水性和抗污性能,其接触角比PVDF膜下降8.2°,总孔隙率增加13.40%,PEG/GO/TiO₂纳米复合材料在PVDF膜中分散较均匀。在0.08 MPa的工作压力下,0.60%PEG/GO/TiO₂/PVDF的纯水通量高达282.44 L/(m²·h),对腐植酸溶液的过滤通量为131.96 L/(m^2...     

Characterization and performance of PVA/Psf composite hollow fiber UF membrane prepared with interfacial polymerization

A new composite hollow fiber ultrafiltration (UF) membrane was prepared with the interfacial polymerization method. A dense layer of polyvinyl alcohol (PVA) was coated on the surface and embedded into the pores of the support polysulfone (PSf) membrane through a dead‐end filtration process and cross‐linked reaction with diisocyanate (TDI) at room temperature. The surface morphology and functional groups of the composite membrane were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and Fourier transformation infrared spectrometer (FTIR). Anti‐fouling experiments were conducted to study the hydrophilicity and anti‐fouling properties of the support and composite membranes. The performances of the composite membrane were significantly influenced by preparation conditions. The composite membrane that performed most efficiently was prepared at an optimal condition: 30 min of dead‐end filtration, 0.25 wt% of PVA, 0.50 vol% of TDI, and 60 sec of interfacial reaction. Laboratory scale tests demonstrated that the new composite PVA/PSf membrane has a higher anti‐fouling capability and higher flux for oily wastewater treatment. The hydrophilic groups (? OH) enriched in the PVA molecules on the composite surface could play an important role for the improvement of the anti‐fouling property and the enhancement of flux recovery rate of the composite membrane. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Structural and performance properties of UV-assisted TiO2 deposited nano-composite PVDF/SPES membranes

In this research, the surface of poly (vinylidene fluoride) (PVDF)/sulfonated polyethersulfone (SPES) blend membrane prepared via immersion precipitation was modified by depositing of TiO₂ nano-particles followed by UV irradiation to activate their photocatalytic property. The membranes were characterized by FTIR, SEM, AFM, contact angle, dead end filtration (pure water flux and BSA solution flux), antifouling analysis and antibacterial activity. The FTIR spectrum confirmed the presence of OH functional groups on the PVDF/SPES membrane structure, which was the key factor for deposition, and self-assembly of TiO₂ nanoparticles on the membrane surface. The SEM and AFM images indicated that the TiO₂ nanoparticles were deposited on the PVDF/SPES membrane. The contact angle measurements showed that the hydrophilicity of PVDF/SPES membrane was strongly improved by TiO₂ deposition and UV irradiation. The filtration results indicated that the initial flux of TiO₂ deposited PVDF/SPES membranes was lower than the initial flux of neat PVDF/SPES membrane. However, the former membranes showed lower flux decline compared to the neat PVDF/SPES membrane. The BSA rejection of modified membranes was improved. The fouling analysis demonstrated that the TiO₂ deposited PVDF/SPES membranes showed the fewer tendencies to fouling. The results of antibacterial study showed that the UV irradiated TiO₂ deposited PVDF/SPES membranes possess high antibacterial property.     

Amphiphilic PVDF-g-PDMAPMA ultrafiltration membrane with enhanced hydrophilicity and antifouling properties

It is easy to adsorb the pollutants from water owning to the hydrophobicity of the poly(vinylidene fluoride) (PVDF) ultrafiltration (UF) membrane. To improve the hydrophilicity of the PVDF UF membrane, a novel amphiphilic copolymer PVDF-g-poly-N-(3-dimethylaminopropyl)methacrylamide] (PDMAPMA) was developed. The amphiphilic PVDF-g-PDMAPMA was synthesized with PVDF and N-(3-dimethylaminopropyl)methacrylamide (DMAPMA) via free-radical polymerization, and characterized by Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance. The scanning electron microscopy and energy dispersive X-ray spectroscopy were used to characterize the structure morphologies and elementals of the blend PVDF membranes, respectively. The pure water flux (PWF), molecular weight cutoff, and bovine serum albumin (BSA) solution filtration experiments were tested to evaluate the permeation performance and antifouling properties of the membranes. The experimental results showed that the PWF was 263.1 L m⁻² h⁻¹, BSA rejection rate was 98.1% and flux recovery rate was 95.1% of the prepared blend membrane which had obvious improvement compared with the pristine PVDF membrane (17.3 L m⁻² h⁻¹, 91.0, and 83.8%, respectively). The antibacterial activity test showed the prepared blend membrane had good potency against microorganisms. A novel hydrophilic PVDF membrane with good antibacterial properties was developed and would be promising for wastewater treatment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48049.     

Preparation of PVDF ultrafiltration membranes using PVA as pore surface hydrophilic modification agent with improved antifouling performance

Novel polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes were facilely fabricated using polyvinyl alcohol (PVA) aqueous solution as the coagulation bath through phase inversion method. In the process, PVA was introduced into the pore surfaces of the PVDF membranes via the interdiffusion of the non‐solvent water and the solvent. The effects of PVA content in the coagulation bath on membrane properties were systematically discussed. The results indicated that the increase of PVA content in coagulation bath resulted in the formations of the more sponge‐like structures and the higher surface hydrophilicity. Smaller pore size led to lower water flux and higher bovine serum albumin rejection. Fouling resistance measurement indicated that the membranes made in PVA/water coagulation bath had higher flux recovery ratio (92.1%) than the membrane made in a pure water bath (71.0%). Furthermore, mechanical property test revealed that the resulting membranes had high tensile strength and Young's modulus. In this work, we found that the morphology and the property of the novel PVDF membranes could be determined by the PVA content in the coagulation bath. POLYM. ENG. SCI., 59:E384–E393, 2019. © 2018 Society of Plastics Engineers     

Poly(ether imide) membranes modified with charged surface‐modifying macromolecule—Its performance characteristics as ultrafiltration membranes

Modification of poly (ether imide) (PEI) ultrafiltration (UF) membranes was attempted by blending charged surface modifying macromolecule (cSMM). Compared to the pure PEI membrane, blending of PEI with cSMM resulted in blend membranes with enhanced UF characteristics such as lower hydraulic resistance (R_m) and higher pure water flux (PWF) coupled with higher water content (WC). Among the various modified membranes, blend membranes with 5 wt % cSMM concentration exhibited higher PWF (60.38 L m^?2 h^?1), WC (73.6%), protein permeate flux (27.12 L m^?2 h^?1) and lower flux decline rate (R_fd) (55.1%), R_m (5.21 kPa/L m^?2 h^?1), bovine serum albumin (BSA) rejection (87.1%). Meanwhile, the fouling resistant ability was studied by flux recovery ratio (FRR) after water and alkali cleaning, irreversible and reversible fouling rate. Higher FRR after water cleaning (95.07%), FRR after alkali cleaning (97.1%), reversible fouling rate (50.14%) and lower irreversible fouling rate (5%) exhibited by 5 wt % cSMM membranes showed its better antifouling ability compared to pure PEI and other blend membranes because of its higher hydrophilic nature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40320.     

High permeability poly(vinylidene fluoride) ultrafiltration membrane doped with polydopamine modified TiO2 nanoparticles

In order to improve the water permeability of poly(vinylidene fluoride) (PVDF) ultrafiltration (UF) membranes with low molecular weight cut-off (MWCO), polydopamine (PDA) was employed in the membrane preparation process. Owing to its merits of material-independent adhesion, PDA was coated on inorganic particles or added in coagulation bath to tailor the final membrane structure and property. The introduction of PDA broke through the permeability/selectivity trade-off of the PVDF membrane. By adding the PDA coated titanium dioxide (PDA/TiO₂) nanoparticles, water flux increased by 287% while MWCO kept similar with the pristine PVDF membrane. Thermodynamics and Kinetics of the PVDF/additives/non-solvent were analyzed and shown that nanoparticles reduced the thermodynamic stability and increased the phase separation speed, and the speed can be adjusted using different nanoparticles. Additionally, X-ray diffraction (XRD) test indicated that PVDF crystalline form changed from α phase to β phase after adding different nanoparticles. Permeability/selectivity trade-off was broken through by DA addition in coagulation bath. Compared with the original PVDF membrane, when the DA concentration of the coagulation bath was 2.0 g·L⁻¹, water flux increased by 312%, and MWCO of the PVDF membrane ranged in 10,000 to 20,000 Da as well as contact angle decreased from 81.4° to 45°.     

Effect of additives concentration on the surface properties and performance of PVDF ultrafiltration membranes for refinery produced wastewater treatment

The aim of this study was to investigate the effect of pore-forming hydrophilic additives on the porous asymmetric polyvinylideneflouride (PVDF) ultrafiltration (UF) membrane morphology and transport properties for refinery produced wastewater treatment. PVDF ultrafiltration membranes were prepared via a phase inversion method by dispersing lithium chloride monohydrate (LiCl·H₂O) and titanium dioxide (TiO₂) nanoparticles in the spinning dope. The morphological and performance tests were conducted on PVDF ultrafiltration membranes prepared from a different additive content. The top surface and cross-sectional area of the membranes were observed using a field emission scanning electron microscope (FESEM) and energy dispersive X-ray (EDX) analysis. The surface wettability of porous membranes was determined by the measurement of a contact angle. The mean pore size and surface porosity were calculated based on the permeate flux. The results indicated that the PVDF/LiCl/TiO₂ membranes with lower TiO₂ nanoparticles loading possessed smaller mean pore size, more apertures inside the membrane with enhanced membrane hydrophilicity. LiCl·H₂O has been employed particularly to reduce the thermodynamic miscibility of dope which resulted in increasing the rate of liquid–liquid demixing process. The maximum flux and rejection of refinery wastewater using PVDF ultrafiltration membrane achieved were 82.50 L/m² h and 98.83% respectively at 1.95 wt.% TiO₂ concentration.     

Enhanced water flux through ultrafiltration polysulfone membrane via addition‐removal of silica nano‐particles: Synthesis and characterization

In the present paper, hierarchically structured ultrafiltration polysulfone (PSf) membrane was prepared to explore the effect of addition and subsequent removal of SiO₂ nano‐particles on the membrane morphology, hydrophilicity, and separation properties. The PSf based membranes namely PSf, PSf/SiO₂ and PSf/WSiO₂ (i.e. SiO₂ nano‐particles was acid‐washed and removed from PSf/SiO₂), were synthesized and characterized by different characterization methods. Pure water flux through the membranes was determined using a filtration unit operating at a continuous dead‐end flow mode. The modification enhanced the morphology, hydrophobicity, porosity and transport properties of the modified membranes, although the molecular weight cut‐off (MWCO) of the membranes was not changed considerably. In comparison, PSf/WSiO₂ membrane exhibited excellent pure water flux (about 4.5 times the flux of PSf, and 17 times the flux of PSf/SiO₂), although antifouling property of PSf/SiO₂ in separation of bovine serum albumin (BSA) was better than that of PSf and PSf/WSiO₂ membranes. The results suggested that the addition/removal of sacrificial solid fillers within/from a membrane matrix may provide a promising strategy to enhance PSf membrane transport property. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43556.     

Preparation and characterization of PVDF-PFSA flat sheet ultrafiltration membranes

High performance polyvinylidene fluoride (PVDF) flat sheet ultrafiltration (UF) membranes have been prepared by an immersion precipitation phase inversion method using perfluorosulfonic acid (PFSA) as a pore former and as a hydrophilic component of the membranes and polyethylene glycol (M_w = 400) (PEG400) as a pore forming agent. The effects of the presence of PEG and the concentration of the PFSA on the phase separation of the casting solutions and on the morphologies and performance of UF membranes including their porosity, water flux, rejection of bovine serum albumin (BSA) protein, and anti-fouling property were investigated. Phase diagrams, viscosities and the phase separations upon exposure to water vapor showed that both PEG400 and PFSA promoted demixing of the casting solution. Scanning electron microscopy measurements showed that the PVDF-PFSA blend membranes had more macropores and finger-like structures than the native PVDF membranes. The PVDF-PFSA membrane (5 wt-% PEG400+ 5 wt-% PFSA) had a pure water flux of 141.7 L/m²·h, a BSA rejection of 90.1% and a relative pure water flux reduction (RFR) of 15.28%. These properties were greatly superior to those of the native PVDF membrane (pure water flux of 5.6 L/m²·h, BSA rejection of 96.3% and RFR of 42.86%).     

Fabrication of antifouling membranes by blending poly(vinylidene fluoride) with cationic polyionic liquid

Membrane fouling problem is now limiting the rapid development of membrane technology. A newly synthesized cationic polyionic liquid (PIL) [P(PEGMA-co-BVIm-Br)] was blended with poly(vinylidene fluoride) (PVDF) to prepare antifouling PVDF membranes. The PVDF/P(PEGMA-co-BVIm-Br) exhibited an increased surface hydrophilicity, the water contact angle was reduced from 77.8° (pristine PVDF) to 57.9°. More porous membrane structure was obtained by adding PIL into the blending polymers, as high as 478.0 L/m²·h of pure water flux was detected for the blend PVDF membrane in comparison with pristine PVDF (17.2 L/m²·h). Blending of the cationic PIL with PVDF gave a more positive surface charge than pristine PVDF membrane. Blend membranes showed very high rejection rate (99.1%) and flux recovery rate (FRR, 83.0%) to the positive bovine serum albumin (BSA), due to the electrostatic repulsion between the membrane surface and proteins. After three repeated filtration cycles of positive BSA, the blend PVDF membranes demonstrated excellent antifouling performance, the permeation flux of the membranes was recovered very well after a simple deionized water washing, and as high as 70% of FRR was obtained, the water flux was maintained at above 350 L/m²·h. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48878.     

Pore morphology control and hydrophilicity of polyacrylonitrile ultrafiltration membranes

The effects of different solvents (dimethyl formamide: DMF and dimethylsulfoxide: DMSO) on the solubility of polyacrylonitrile (PAN) were investigated by the phase diagrams of H₂O/DMF/PAN and H₂O/DMSO/PAN ternary systems through cloud‐point titration method at low polymer concentration. The influences of polymer concentrations and temperatures on the morphologies of PAN ultrafiltration membranes were elucidated. The morphologies of fabricated UF membranes were characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM), and the basic performance of ultrafiltration including pure water flux and rejection of BSA were explored. At 25°C, the pure water flux of ultrafiltration membranes at the lower PAN content (16 wt % PAN in 84 wt % DMSO) reached 213.8 L/m/bar and the rejection of BSA was 100%. Interestingly, the water flux of UF membranes dramatically decreased to 20.6 L/m/bar (20 wt %) and 2.9 L/m/bar (24 wt %) when increasing PAN concentrations in DMSO. On the other hand, the hydrophilicity of membranes can be enhanced by increasing coagulation temperatures and polymer concentrations which were characterized by static contact angle, fitting well with the variation tendency of roughness. Although there are many works concerning on the effects of phase inversion conditions on the performance of PAN UF membranes, to our best knowledge, there is seldom works focusing on investigating the membrane hydrophilicity trend by adjusting phase inversion conditions. To disclose the reason of the enhanced hydrophilicity, the water and glycol contact angles of various membranes were measured and the surface tensions were presented. The results illustrated that the enhanced hydrophilicity of PAN UF membranes fabricated at higher temperatures or higher polymer concentrations was due to the higher polarity on membrane surface. Since the vast majority of ultrafiltration membranes in labs and in industrial scale have been fabricated by immersion phase inversion method, this work can provide a guidance to obtain hydrophilic PAN UF membranes by adjusting the process of phase inversion. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41991.     

Fabrication of efficient pervaporation desalination membrane by reinforcement of poly(vinyl alcohol)–silica film on porous polysulfone hollow fiber

Pervaporation membrane technology is commercially successful in the dehydration of organic solvents, and the technology has potential for seawater desalination with high recovery because of its capability to treat highly saline water. But to make the technology advantageous over the other available membrane desalination technologies in terms of productivity flux without additional energy cost, the selective barrier layer is required to be extremely thin, defect‐free, hydrophilic, and selective to water. In this work, we prepared an efficient membrane by reinforcing a highly water‐permeable but continuous barrier layer of poly(vinyl alcohol)–silica (PVA‐SiO₂) hybrid material on porous polysulfone hollow fibers. The PVA‐SiO₂ in acidified and hydrated ethanol was aged at room temperature for a period to allow solvent evaporation to obtain the solution concentration desired for the reinforcement. The reinforced hollow fiber membrane with optimal PVA‐SiO₂ barrier layer thickness exhibited a performance with a flux of 20.6 L m^?2 h^?1 and 99.9% salt rejection from a saline feed of 2000 ppm NaCl at 333 K. The effects of PVA‐SiO₂, temperature, and feed salinity on the pervaporation performance of the membrane were also studied. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45718.