Fiber Membrane Surface Research Articles

Hierarchically structured hollow PVDF nanofibers for flexible piezoelectric sensor

The emergence of flexible sensors addresses the limitations of traditional detection equipment, such as large size, high cost, and inconvenient portability. These sensors have significantly advanced the development of wearable electronic devices for applications in electronic skin, energy harvesting, and energy storage. To enhance the sensitivity of flexible sensors, we developed a hierarchical polyvinylidene fluoride (PVDF) nanofiber-based piezoelectric sensor. By utilizing coaxial electrospinning, we fabricated nanofibers with hollow interiors and porous outer walls. Additionally, microstructures were constructed on the fiber membrane surface by modifying the collector’s shape. The resulting microstructured hollow PVDF nanofiber membrane exhibited high β-phase content (91.31 %), excellent flexibility (maximum strain 56.9 %), and high porosity (88.94 %). The sensor demonstrated a sensitivity of 2.7 V/N (1.08 V/kPa) and a maximum output voltage of 10.1 V, approximately three times higher than that of solid PVDF nanofibers without microstructures. Even after 14,400 cycles of impact, the sensor maintained stable output. The sensor was successfully applied to human activity monitoring and gesture recognition, showcasing its ability to monitor various human activities, respond rapidly (60.4 ms), and synchronously control a mechanical palm to perform different gestures. This work highlights the potential of hierarchically structured hollow PVDF nanofibers in advancing the performance and application scope of flexible piezoelectric sensors.

Nanofiber membranes fabricated by coaxial electrospinning with porous channel structure for high-efficiency oil-water separation

The electrospinning nanofiber membranes modified by nanoparticles can effectively improve anti-oil adhesion and separation performance. However, the low stability of nanoparticles on the fiber membrane surface substantially limits the operational lifespan of the membrane. Herein, poly(vinylidene fluoride) (PVDF) nanofiber membranes with multi-scale microporous channel structures are prepared using coaxial electrospinning and a sacrificial template strategy. Subsequently, iron phytate nanoparticles are grown in situ on the fibers to fill the porous structures by utilizing the hollow and porous nanofibers as a framework. The interlocking structure between the nanoparticles and the porous fibers significantly enhances the stability and durability between nanoparticles and the fiber membrane. Even after being subjected to ultrasonic treatment for 7 h, there is no discernible shedding of nanoparticles from the fiber membrane. The prepared nanofiber membrane demonstrates exceptional superhydrophilicity and underwater superoleophobicity, exhibiting remarkable self-cleaning capability and resistance to crude oil contamination. Additionally, the membrane efficiently separates various oil-in-water emulsions, achieving a high separation efficiency of over 99%. Moreover, the membrane also demonstrates excellent adsorption capability towards cationic dyes. Therefore, this interlocking structure composed of nanoparticles and nanofibers presents new ideas and insights for the preparation of high-performance and durable oil–water separation membranes.

A novel glue attachment approach for precise anchoring of hydrophilic EGCG to enhance the separation performance and antifouling properties of PVDF membranes

A novel glue attachment approach was proposed to form a durable hydration layer on a hydrophobic PVDF hollow fiber membrane (PVDF HFM) surface to improve its hydrophilicity and antifouling ability during wastewater filtration. The functional glue was synthesized from reclaimed styrene butadiene rubber (SBR) and a hydroxyl group was created with an epoxidation reaction (ESBR). The hydrophilic epigallocatechin-s-gallate (EGCG) was then precisely anchored via hydrogen bonding with multiple phenolic hydroxyl groups in the ESBR without penetrating into the inner matrix of the PVDF to prevent flux decline. The hydrophilicity of the PVDF membrane increased drastically and the water contact angle decreased from 62.7° to 45.1° with only a 25% decline in the pure water flux. Furthermore, due to precise anchoring of the EGCG, the modified EGCG-ESBR/PVDF membrane showed a higher pure water flux (110.6 L m−2h−1) and much higher BSA and oil (kerosene) rejection rates (approximately 94.5% and 99.5%, respectively) compared to membranes directly coated with EGCG (EGCG-PVDF). Moreover, the modified membrane also showed higher water flux recovery after multiple filtration cycles. This promising and efficient hydrophilic modification suggests great potential for application of the eco-friendly material in wastewater treatment.

Improved Spherical Particle Preparation of Ceftriaxone Sodium via Membrane-Assisted Spherical Crystallization

Spherical drug particles prepared by the spherical crystallization technique can simultaneously improve the mobility of particles, mechanical properties, drug solubility and bioavailability, etc. However, high-efficient mixing of a solution and the formation of uniform bridging liquid droplets were crucial for accurate control of spherical crystallization processes. Herein, a novel membrane-assisted spherical crystallization (MASC) technology was proposed to produce monodisperse spherical agglomerates of ceftriaxone sodium. The poor solvent permeation rate of MASC was stabilized by adjusting the liquid flow velocity in the shell side and tube side. Uniform bridging liquid droplets constructed by a polytetrafluoroethylene hollow fiber membrane were observed in real time. A stable flow field and crystallization microenvironment were provided on the hollow fiber membrane surface. The crystal size distribution and the coefficient of variation of ceftriaxone sodium products were improved compared with those of conventional spherical crystallization (CSC) under the same stirring rate. The impurities of CSC products did not meet the requirements due to the degradation after 14 days’ acceleration experiment, while the one of MASC products still met the pharmacopoeia requirements after 30 days. This study provides a potential membrane-based technology for the enhancement of spherical crystallization of related drugs.

Surface modified materials for active capture of enzymes.

The insertion of bis(diarylcarbene)s onto a glass fiber (GF) membrane surface provided an active coating for the direct capture of protein - exemplified by the enzyme, cellulase - through a mild diazonium coupling process which does not require additional coupling agents. Successful cellulase attachment on the surface was demonstrated by the disappearance of diazonium and formation of azo functions in the N 1s high resolution spectra, the appearance of carboxyl group in C 1s spectra, both observed by XPS; the -CO vibrational bond observed by ATR-IR; as well as the observation of fluorescence. Further, five support materials (polystyrene XAD4 bead, polyacrylate MAC3 bead, glass wool, glass fiber membrane, polytetrafluoroethylene membrane) with different morphology and surface chemistry, were examined in detail as supports for cellulase immobilization using this common surface modification protocol. Of interest is that such covalently bound cellulase on modified GF membrane gave both the highest enzyme loading (∼23 mg cellulase per g support), and retained more than 90% of activity after 6 cycles of re-use, compared with substantial loss of enzyme activity for physiosorbed cellulase after 3 cycles. Optimization of the degree of surface grafting and the effectiveness of a spacer between surface and enzyme for enzyme loading and activity were conducted. This work shows that carbene surface modification is a viable strategy for introducing enzymes onto a surface under very mild conditions and retaining a meaningful level of activity, and particularly, using GF membrane as a novel support provides a potential platform for enzyme and protein immobilization.

Simulation of novel jellyfish type of process for bioremediation application

A bioinspired device was fabricated as a sustainable remedial method and its performance as a membrane-enzyme reactor with cyclic ultrafiltration was investigated. The body of the jellyfish-like device was composed of two parts: 1) Jellyfish arms: Mono and co-axial electrospinning have been utilized to synthesize the flexible parts (e.g., multilayer membrane PS-PVDF/PAN/PS-PVDF) used for immobilization of aliphatic degrading enzymes, and 2) Jellyfish tentacles: Hollow fiber membranes were selected for physical immobilization of polycyclic aromatic hydrocarbon (PAH) degrading enzymes. To study the behavior of the membrane/enzyme reactor, the hollow fiber enzyme reactor with pulsation was operated by recycling an enzyme solution to assess ultrafiltration efficiency. A mathematical model was suggested to describe the experimental data obtained in this study to predict the effectiveness of the reactor for PAH removal. When testing the performance of the jellyfish-like device, those equipped with nanofibers with an oil sorption capacity of (10. ±0.7gdilbit/gfiber) were more effective at removing oil particles before they touched the hollow fiber membrane surface. Moreover, the reaction rate measured in a free soluble enzyme and a recirculating immobilized enzyme solution exhibited a slight difference in the kinetic parameter, Km (0.03 and 0.021 mM) due to the internal diffusional resistance. Based on biodegradation studies, a synergistic effect between membrane adsorption, enzymatic degradation, and ultrafiltration was proposed for the removal of anthracene from the column of water.

Flexible Multifunctional Self-Expanding Electrospun Polyacrylic Acid Covalently Cross-Linked Polyamide 66 Nanocomposite Fiber Membrane with Excellent Oil/Water Separation and High pH Stability Performances

In this paper, we report for the first time the successful formation of a covalent cross-linking structure between polyacrylic acid and polyamide 66 in an electrospun nanofiber membrane by the facilitated amidation reaction using N-Hydroxy-succinimide (NHS) and N-(3-Dimethylaminopropyl)-N’-ethyl-carbodiimide hydrochloride (EDC). The structure and properties of the fiber membrane are characterized using scanning electron microscopy, wide field X-ray diffraction and differential scanning calorimetry. The results show that the presence of the cross-linked structure not only affects the construction of the nanofiber network framework but also influences the pore size distribution and size of the fiber membrane surface, which in turn affects its retention of contaminants and water absorption performance. After modification, the cross-linked membranes exhibited a significant retention performance of up to 77% for methyl tert-butyl ether (MTBE) with a reduced pure water flux. Furthermore, after crosslinking, the fiber membrane has been strongly enhanced with more stable pH response behavior.

Green preparation of PVDF hollow fiber membranes with multiple pore structure via melt spinning method for oil/water separation

Poly(vinylidene fluoride) (PVDF) is one of the most widely used membrane forming polymers with good processability, outstanding mechanical properties, excellent thermal and chemical stability. In this work, PVDF hollow fiber membranes were prepared through the melt spinning method with CaCl2 and PEG as the composite pore forming agents. The influence of different contents of CaCl2 and PEG on the membrane’s structure and properties were studied based on the pore size distribution, porosity, permeation flux, and oil/water separation test etc. There was no obvious dense layer on the PVDF hollow fiber membrane surface, which exhibited multiple pore structure. With the increase of PEG contents, the pore size, the porosity and oil flux improved effectively, correspondingly, the water contact angle and liquid entry pressure decreased. The permeation fluxes of kerosene also increased obviously with the increase of PEG contents, and the maximum flux of M-3 reached as high as 398.4 L·m-2·h-1. Applied to oil/water separation test, M-3 exhibited good oil/water separation performance, and its separation efficiency for water-in-kerosene emulsion can still reach more than 95 % after ten cycles. In particular, there were not any solvents and diluents used in the preparation process, which was a relatively green preparation process.

A novel method to immobilize zwitterionic copolymers onto PVDF hollow fiber membrane surface to obtain antifouling membranes

Zwitterionic materials are considered to be a promising new-generation non- or low-fouling materials. However, stable, and straightforward introduction of zwitterions into membranes for commercial production remains as a big challenge yet. Herein for the first time we propose a simple approach to immobilize zwitterionic copolymers on poly(vinylidene fluoride) (PVDF) hollow fiber membrane (HFM) surfaces with considerably high stability via surface entrapment and subsequent simple reactions. First, a commercial amphiphilic copolymer, viz. styrene–maleic anhydride (PSMA), was entrapped on the outer surface of PVDF membranes using co-extrusion by a triple orifice spinneret. PSMA exhibited excellent stability on the PVDF membrane, and its reactive anhydride (MA) group was stabilized on the outer membrane surface. Next, the commercially available zwitterionic copolymer poly(2-methacryloyloxyethyl phosphorylcholine-co-2-aminoethyl methacrylate hydrochloride) (P(MPC-AEMA)) was immobilized on the PVDF/PSMA membrane surface by a simple reaction between the MA groups of PSMA and the amine groups of P(MPC-AEMA). The P(MPC-AEMA) reacted membrane exhibited noticeable bovine serum albumin (BSA) antifouling and antibacterial properties during both static adsorption and dynamic filtration. The flux recovery ratio (FRR) of the membrane exceeded 80% after seven cycles of BSA filtration. The modified membrane showed an even higher FRR (∼95%) during bacterial filtration, and such excellent performance was attributed to its super hydrophilicity. Our novel, advanced and straightforward modification method lights on a spotlight for a new pathway to make immobilization of zwitterions on polymeric membrane without needing complicated reactions or procedures.

MO272: Effect of the Hollow Fiber Diameter and Membrane Surface Area of the Polymethyl Methacrylate Membrane Filter Used in Continuous Renal Replacement Therapy on the Lifetime of the Filter

Abstract BACKGROUND AND AIMS When polymethyl methacrylate (PMMA) membranes are used in renal replacement therapy, inflammatory cytokines and other substances are removed by adsorption. However, these filters are also prone to clogging and the filter lifetimes are likely to be short. In the present study, we investigated the effects of the hollow fiber inner diameter and membrane area of PMMA membranes on the filter lifetime and protein removal performance using an in vitro continuous hemofiltration (CHF) experimental model with porcine blood. METHOD Three filters with different hollow fiber inner diameters and membrane areas were used: CH-1.0N (membrane area, 1.0 m2; hollow fiber inner diameter, 200 µm), CH-1.0W (prototype: 1.0 m2; 240 µm), and CH-1.8W (1.8 m2; 240 µm). Blood samples from one pig were divided into three portions, and in vitro CHF experiments for each filter were performed at QB = 100 mL/min and QS = QF = 10 mL/min. The pressure changes, total protein concentration in the blood, and total protein amount in the filtrate were measured during the experiments. From the results of the pressure changes, the time for the TMP to reach 200 mmHg (corresponding to the time when the membrane pores were clogged) and the time for the pressure drop through the filter to reach 200 mmHg (corresponding to the time when the hollow fibers were clogged) were calculated as the filter lifetime for comparative evaluation. RESULTS The time for the TMP to reach 200 mmHg was significantly longer with CH-1.8W than that with CH-1.0N or CH-1.0W (Friedman test, P < .05, n = 15). The time for the pressure drop through the filter to reach 200 mmHg was significantly longer with CH-1.8W than that with CH-1.0N or CH-1.0W (Friedman test, P < 0.05, n = 15). The results suggest that an increased membrane surface area is an essential factor for extending the filter lifetime. The total protein adsorption was significantly higher for the CH-1.0W and CH-1.8W filters than for the CH-1.0N filter (two-way ANOVA and post hoc Tukey test, P < 0.01, n = 15). Thus, the membranes with larger hollow fiber inner diameters (CH-1.8W and CH-1.0W) adsorbed more protein. CONCLUSION A larger membrane area contributes to a longer filter lifetime, whereas increase in the hollow fiber inner diameter does not. On the other hand, the protein removal performance, especially the adsorption performance, was higher for membranes with larger hollow fiber inner diameters.

Dehydrogenation Coupling of Methane Using Catalyst-Loaded Proton-Conducting Perovskite Hollow Fiber Membranes.

Catalytic dehydrogenation coupling of methane (DCM) represents an effective way to convert natural gas to more useful C2 products (C2H6, C2H4). In this work, BaCe0.85Tb0.05Co0.1O3−δ (BCTCo) perovskite hollow fiber membranes were fabricated by the combined phase inversion and sintering method. SrCe0.95Yb0.05O3−δ (SCYb) perovskite oxide was loaded as a catalyst onto the inner hollow fiber membrane surface, which promoted the CH4 conversion and the C2 hydrocarbon selectivity during the DCM reaction. The introduction of steam into the methane feed gas mixture elevated the C2 selectivity and yield due to the alleviation of coke deposition. Switching N2 to air as the sweep gas further increased the C2 selectivity and yield. However, the conversion of methane was limited by both the low permeability of the membrane and the insufficient catalytic activity of the catalyst, leading to low C2 yield.

A Novel, Stable and Straightforward Method to Immobilize Zwitterionic Copolymers Onto Pvdf Hollow Fiber Membrane Surface to Obtain Antifouling Membranes

A Novel, Stable and Straightforward Method to Immobilize Zwitterionic Copolymers Onto Pvdf Hollow Fiber Membrane Surface to Obtain Antifouling Membranes

Biofilm-Integrated Glycosylated Membrane for Biosuccinic Acid Production.

Biofilm-based cell-immobilized fermentation technology is regarded as the technique with the most potential for biobased product (chemicals, biofuelss materials, etc.) production in industry. Glycosylated membrane can mimic natural extracellular matrix (ECM) and improve cell adhesion and biofilm formation based on carbohydrate-microbial lectin interaction. Here, we applied glycosylated membrane with rhamnose modified surface for constructing Actinobacillus succinogenes biofilm and producing biosuccinic acid. Polymer hollow fiber (PHF) membrane surface was first modified by glycosylation based on physical adsorption approach. The approach is simple, green, and suitable for scale-amplification. Then, the microbial biofilm formed dramatically on the modified membrane surface. And for subsequent biosuccinic acid production, the maximum titer of succinic acid reached 67.3 g/L, and the yield was 0.82 g/g. Compared with free cell fermentation, the titer and yield increased by 18% and 9% in this biofilm-based cell-immobilized fermentation system, respectively. Importantly, the production efficiency of biosuccinic acid increased obviously for subsequent biofilm-based cell-immobilized fermentation. In addition, the biofilm-integrated glycosylated membrane showed high reusability for succinic acid production. This result is important for developing biofilms for a wide range of applications in bioproduct (chemicals, biofuels, materials, etc.) production.

One-step entrapment of a PS-PEGMA amphiphilic copolymer on the outer surface of a hollow fiber membrane via TIPS process using triple-orifice spinneret

A robust hydrophobic membrane modification method is required to avoid fouling that significantly affects membrane separation performance and energy consumption. In this study, we developed a one-step surface entrapment of an amphiphilic copolymer onto a poly(vinylidene fluoride) (PVDF) hollow fiber membrane (HFM) surface prepared via a thermally induced phase separation (TIPS) method. By extruding a poly(styrene)-b-poly(ethylene glycol) methacrylate (PS-PEGMA) solution at the outermost layer of a triple-orifice spinneret, entrapment of the amphiphilic copolymer onto the PVDF HFM was performed. The results showed that the preparation conditions significantly altered the membrane surface hydrophilicity without changing the bulk structure of the membrane. A longer air-gap distance, lower polymer concentration in the polymer solution, and higher PS-PEGMA concentration are favorable for better copolymer entrapment at the membrane surface. By comparing the water contact angle and BSA adhesion obtained using the proposed method and that achieved by the conventional coating process of the PS-PEGMA, it can be concluded that our one-step modification method is more robust and reliable.

Cationic hyperbranched poly(amido-amine) engineered nanofiltration membrane for molecular separation

High-efficient separation of molecules is of great significance in food, biotechnology, pharmaceutical and dairy industries. To this end, cationic hyperbranched poly (amido-amine)s (HBPs) with different numbers of quaternary ammonium groups were employed as a new kind of 3D spherical macromonomers to fabricate nanofiltration (NF) membranes, through interfacial polymerization (IP) between cationic HBPs and trimesoyl chloride (TMC) on a polyvinyl chloride ultrafiltration (PVC-UF) hollow fiber membrane surface. Apart from the inner voids inside cationic HBP molecules for fast transport of water molecules, sizes and charge properties of the outer voids between cationic HBP molecules can be modulated by changing the numbers of quaternary ammonium groups on cationic HBP molecule surfaces for enhancing both high permeability and selectivity (water permeance and MgCl2 rejection rate of the resultant NF membrane are up to 310.5 L m−2 h−1 MPa−1 and 92.0% respectively). Based on the separation mechanism of combined steric and Donnan effects, the resultant NF membrane exhibits ultrahigh retentions to molecules with high molecular weights (MWs) or positive charges, thus molecular-level selectivity to VB12/VB2 (neutral molecules with distinct MWs) or VB1/VB2 (cationic/neutral molecules with similar MWs) can be achieved.

Preparation of Polypropylene/PVDF Composite Membrane by Dip-Coating Method

In this research, a composite membrane was prepared by dipping a hollow fiber polypropylene (PP) membrane in a polyvinylidene fluoride (PVDF) solution. A small concentration of volatile solvent (acetone and tetrahydrofuran/THF) was added to the PVDF solution to form a tight structure in the membrane surface. The influence of PVDF concentration, type of volatile solvents (acetone and THF), and the dip-coating cycle on membrane characteristics, including porosity, swelling degree, and contact angle, were investigated. The flux and rejection of the membranes were also investigated during the filtration of hexane/oil solution. The experimental results showed that low membrane porosity (3%), low swelling degree (0.1%), and high water contact angle (140°) were obtained when 8%wt PVDF was blended with 10%wt acetone and then coated on PP hollow fiber membrane surface with 3 (three) dip-coating cycles. The oil rejection was 68% after 45 minutes of filtration time with a permeate flux of 20 L.m−2.h−1. Higher membrane porosity and permeate flux can be obtained by reducing the dip-coating cycle; however, a lower oil rejection was achieved.

The effect of grafting monomer charge on the antifouling performance of poly(ether ether ketone) hollow fiber membrane by ultraviolet irradiation polymerization

AbstractTo improve the antifouling properties of poly(ether ether ketone) (PEEK) membrane, negatively charged acrylic acid (AA), neutral ethyl hydroxyacrylate (HEA) and positively charged acryloxyethyl trimethylammonium chloride (DAC) as hydrophilic monomers were respectively grafted onto the PEEK hollow fiber membrane surface via ultraviolet irradiation polymerization. The effects of the grafted monomers on surface chemical structure, surface morphology, zeta potential, hydrophilic performance, permeability and the antifouling properties of the membrane were investigated in detail. The results show that the charge state of the membrane surface is closer to the monomer charge characteristic, which obviously affects the permeability and antifouling performance of the membrane. The pure water flux of the membrane grafted with neutral hydrophilic HEA monomer is increased and the antifouling properties to bovine serum albumin (BSA) and sodium alginate (SA) are also enhanced, while the pure water flux of the membranes grafted with negatively charged AA monomer or positively charged DAC monomer is decreased, with different antifouling properties to BSA and SA. Furthermore, the antifouling experiment with BSA under different pH conditions revealed that membrane fouling depends on the pH value, and membrane fouling was the most serious at the isoelectric point of BSA. © 2020 Society of Chemical Industry

One step surfactant entrapment onto PVDF hollow fiber membrane surface by the TIPS process using a triple-layer orifice spinneret

One step entrapment of the several kinds of surfactants on the outer surface of the PVDF hollow fiber membrane during the air gap distance was studied by extruding the surfactant solution as the outermost layer of the triple layer nozzle via thermally induced phase separation (TIPS) process. Effect of the membrane preparation conditions, including the air gap distance, surfactant concentration and types of surfactant with different hydrophilic-lipophilic balance (HLB) number and molecular weight on the membrane surface hydrophilicity and protein fouling resistance were evaluated. Using a long air gap distance with optimal surfactant concentration was resulted in a membrane with a considerable improvement in hydrophobicity. Surfactants with the lowest HLB number and molecular weight improved membrane hydrophilicity and resistance against pure water permeability decrease after drying membrane in air. Based on water contact angle results, entrapment of the surfactant with a more hydrophobic segment to hydrophilic segment ratio (smaller HLB) plays a crucial role to increase the membrane surface hydrophilicity regardless the intrinsic hydrophilicity of the surfactant molecule. The stability of the surfactant entrapped by this method was higher than that of the simple coating method. Static adsorption of the lysozyme on the surface of the surfactant entrapped membrane was in line with water contact angle results. Thus, entrapping surfactants with low HLB number and molecular weight was recommended to obtain a membrane with the considerable anti-fouling property.

Characterization and stability study of pseudo-emulsion hollow fiber membrane: Separation of Ethylparaben

Ethylparaben (EP), being one of the members of parabens family is an endocrine disrupting compound. Despite their efficient elimination in waste water treatment plants, parabens are still noticed in river waters. Studies were conducted by Pseudo-emulsion hollow fiber strip dispersion (PEHFSD) system using pseudo-emulsion comprised of Trioctylamine (carrier), n-heptane (solvent) and Na2CO3 (strippant) for EP elimination from aqueous feed phase. Influence of different operational factors like concentration of feed, carrier and stripping phase were studied for EP removal. 100% removal of EP was achieved by PEHFSD system. Permeability studies were conducted and mass transfer coefficient for aqueous and membrane phase were also evaluated at optimum conditions. Fourier transform infrared spectroscopy confirmed the bonding and existence of various functional groups in the membrane phase. Field emission scanning electron microscope revealed the pores on hollow fiber membrane surface. Droplet size distribution and backscattering profile of pseudo-emulsion at different impeller speed indicated instability of pseudo-emulsion and concentrated EP can be easily recovered. Multiple runs conducted with fresh feed solution and fresh pseudo-emulsion showed 100% removal of EP for five runs which indicated stability of membrane phase within the micropores for longer time. The recyclability of pseudo-emulsion phase was also studied by contacting the fresh feed with the previously used pseudo-emulsion phase. It was observed that removal of EP was 100%, 73% and 43% for 1st, 2nd and 3rd run respectively.

Fabrication of superhydrophilic PVDF hollow fiber membranes with a fish-scale surface for water treatment

With enhancing rejection and antifouling properties, the permeate flux of membranes is usually reduced during the surface modification. Here, a novel method is presented to break through the permeability-selectivity trade-off by grafting zwitterionic copolymers and constructing the fish-scale microstructures on the PVDF hollow fiber membrane surface. The surface microstructure was optimized by manipulating the reaction temperature. Mainly, the molecule chains of zwitterionic copolymers were regularly aggregated due to the intermolecular attractive electrostatic forces, forming the fish-scale microstructures. Excitingly, the pore size was not decreased but slightly increased due to the stretching resulted from different aggregates. In contrast with the original membrane, the water fluxes of the as-prepared membrane M2 and M3 were largely increased from 245.8 L/m2 h to 766.9 L/m2 h and 733.0 L/m2 h, and separation efficiencies of oil/water emulsion were also highly elevated from 46.5% to 99.3% and 98.4%, respectively. The antifouling performance was simultaneously enhanced, and the flux recovery ratios were increased from 37.9% to 97.2% and 95.6%. As expected, this study can offer novel insights into overcoming the trade-off.