Hydrophilic Membrane Research Articles

Biocompatible Zn-Phthalocyanine/Gelatin Nanofiber Membrane for Antibacterial Therapy.

In this study, the fabrication and characterization of Zn-phthalocyanine/gelatin nanofibrous membranes is reported using the electrospinning technique. The membranes exhibit a homogeneous distribution of Zn-phthalocyanine within the gelatin matrix, maintaining the structural integrity and photosensitizing properties of the phthalocyanine. Scanning electron microscopy revealed that the electrospun fibers possess diameters ranging results as 100-300, 200-700, and 300-800nm for Gel, ZnPc/Gel 1, and ZnPc/Gel 2, respectively. The addition of ZnPc does not decrease the hydrophilicity of the Gel membrane. The nanofibrous membranes showed good cytocompatibility, as indicated by the high viability of Vero cells exposed to membrane extracts. Furthermore, these composites supported cell adhesion and proliferation on their surfaces. The two Zn-phthalocyanine/gelatin nanofiber formulations exhibited significant antimicrobial activity toward Escherichia Coli (E. Coli) and Staphylococcus Aureus (S. Aureus) under visible light illumination, achieving reductions of 3.4 log10 and 3.6 log10 CFUmL-1 for E. coli, and 3.9 log10 and 4.1 log10 CFUmL-1 for S. aureus. These results demonstrate the potential of Zn-phthalocyanine/gelatin nanofibrous membranes as effective agents in antibacterial photodynamic therapy, providing a promising solution to control bacterial infections and antibiotic resistance.

Contributions of Colloidal Forces to the Heterogeneous Separation of Stable Oil-In-Water Emulsions.

We use theory to study the distribution of spherical emulsion oil droplets in water near a lipophilic surface as a guideline for designing membranes for oil/water phase separation. Heterogeneous phase separations are shown in our laboratory using hydrophilic and hydrophobic membrane designs, where the affinity of the membrane surface to one of the phases in the mixture locally increases its concentration. Considering a colloidal emulsion (nano- to microemulsions) of spherical and noncoalescing droplets, we assess the contribution of colloidal forces, i.e., van der Waals, electrical double layer, and hydrophobic interactions and the finite size of the droplets to the accumulation of spherical emulsion droplets near a surface. We use our theory to study an experiment-inspired case study and find that an isolated lipophilic membrane surface in contact with an oil-in-water emulsion supports the oil-enriched emulsion phase in a thin layer near the membrane surface, suggesting that a membrane pore size comparable to this thickness should support oil-enriched emulsion in the membrane pores and hence past the membrane.

Zwitterion Modification in Desalination Membrane for Rejecting Salt and Salt Ions in Brackish Water – A Mini Review

ABSTRACTDesalination membrane using zwitterion modification provides a significant opportunity to enhance excellent properties for rejecting salt and salt ions. The outstanding properties are designed by positive and negative charges attached to the membrane surface, including water permeability, salt permeability, fouling, and hydrophilicity of the membrane surface. The hydrophilic membrane, which is mentioned as one of the types of desalination membrane, presents the ability to repel salt and salt ions and pass the water. The modification of hydrophilic membranes is also affected by several factors, including water permeability, salt permeability, fouling of membrane surfaces, crossflow velocity, transmembrane pressure, and temperature. Regarding membrane modification, zwitterion has been applied for several ranges, such as the hemodialysis process, live cell imaging, antibacterial surfaces, and wound dressing. However, using a zwitterion modification membrane for desalinating water containing salt content, including brackish water, has yet to be developed. In addition, literature reviews related to polymer membranes for brackish water desalination have never been comprehensively documented. Thus, this review article addresses the zwitterion modification for desalination membranes, which can reject salt and salt ions in brackish water. Furthermore, the mechanism of zwitterion modification for desalination membranes has been presented. Finally, the challenge of zwitterion modification for desalination membranes has been evaluated to inspire insight for future studies.

Synthetic Periodontal Guided Tissue Regeneration Membrane with Self-Assembling Biphasic Structure and Temperature-Sensitive Shape Maintenance.

Periodontal disease poses significant challenges to the long-term stability of oral health by destroying the supporting structures of teeth. Guided tissue regeneration techniques, particularly barrier membranes, enable local regeneration by providing an isolated, protected compartment for osseous wound healing while excluding epithelial tissue. Here, this study reports on a thermosensitive periodontal membrane (TSPM) technology designed to overcome the mechanical limitations of current membranes through a semi-interpenetrating network of high molecular weight poly(L-lactic acid) (PLLA) and in situ-polymerized mesh of poly(ε-caprolactone)diacrylate (PCL-DA), and poly lactide-co-glycolide diacrylate (PLGA-DA). An optimized composition allows facile reshaping at greater than 52 °C and rigid shape maintenance at physiological temperature. Its unique bilayer morphology is achieved through self-assembly and thermally-induced phase separation, resulting in distinct yet continuous smooth and nanofibrous compartments adequate for epithelial occlusion and regeneration. Incorporating PLGA-DA enhances the membrane's hydrophilicity and degradation properties, facilitating a more rapid and controlled degradation and therapeutic delivery. This study demonstrates its ability to promote local regeneration by serving as a barrier membrane and simultaneously as a scaffolding matrix in a rat orthotopic periodontal defect model. The TSPM outperformed a clinically available material (Epi-Guide) to facilitate robust alveolar bone and periodontal ligament regeneration at 4 and 8 weeks.

Beta-Cyclodextrin-Modified Covalent Organic Framework Nanochannel for Electrochemical Chiral Recognition of Amino Acids.

The chiral recognition and separation of enantiomers are of great importance for biological research and the pharmaceutical industry. Preparing homochiral materials with adjustable size and chiral binding sites is beneficial for achieving an efficient chiral recognition performance. Here, a homochiral covalent organic framework membrane modified with β-cyclodextrin (CD-COF) was constructed, which was subsequently utilized as an electrochemical sensor for the enantioselective sensing of tryptophan (Trp) molecules. The preferential adsorption of l-Trp over d-Trp at the β-CD sites can enhance the surface charge density and hydrophilicity of the CD-COF membrane, resulting in an increased transmembrane ionic current. Trp enantiomers with concentrations down to 0.28 nM can be effectively discriminated. The l-/d-Trp recognition selectivity increases with the Trp concentration and reaches a value of 19.2 at 1 mM. The selective adsorption of l-Trp to the CD-COF membrane will also hinder its transport, resulting in a l-/d-Trp permeation selectivity of 15.3. This study offers a new strategy to construct homochiral porous membranes and achieve efficient chiral sensing and separation.

Hydrophilic PVDF emulsion separation membranes prepared using TA/APTES as a non-solvent: Effect of lithium chloride hydrate additive content

Currently, surfactant-containing oil–water emulsions are the more difficult part of oily wastewater to treat because of their small droplet size and stable oil–water interface. Membrane separation technology is commonly used for emulsion separation due to its surface wettability and adjustable pore size. Here, tannic acid (TA) and 3-aminopropyltriethoxysilane prepolymerization solutions are used as the exchange solvents, allowing growth on the surface and inside of polyvinylidene difluoride (PVDF). Among them, the content of lithium chloride (LCM) hydrate modulates the range and amount of growth. In the pressure range of 0.1–0.7 bar, the modified hydrophilic PVDF-TA/LCM-2 membranes exhibit high pure water permeation fluxes and emulsion separation efficiencies that can be adapted to different separation conditions. At 0.2 bar, the PVDF-TA/LCM-2 achieves pure water permeate flux and emulsion separation fluxes of 1860 and 648 L m-2 h−1 bar−1, and an emulsion separation efficiency of 99.5 %. In addition, for different kinds of oil-in-water emulsions, the high separation fluxes and high separation efficiencies indicate that PVDF-TA/LCM-2has good emulsion separation performance.

In-situ water separation enhanced methyl glycolate oxidation to methyl glyoxylate by catalytic membrane reactor

The selective oxidation of methyl glycolate by oxygen is a green route for the synthesis of methyl glyoxylate, which however faces great challenges like the consecutive hydrolysis reaction between methyl glyoxylate and by-product water. Herein, we fabricated an in-situ water separation catalytic membrane reactor (CMR) to suppress the hydrolysis of methyl glyoxylate, which can promptly and preferentially remove water from the reaction system by a hydrophilic NaA membrane. The MoO3@NaA CMR achieved a high methyl glyoxylate selectivity of 84.0 % at 260 °C and 2 bar, being 32.4 % higher than that of the conventional fixed-bed reactor (FBR), while the methyl glycolate conversion was almost the same for both modes. Moreover, the deactivation of the MoO3 catalyst caused by water in CMR was also greatly inhibited, exhibiting excellent stability as compared to FBR. The in-situ water separation strategy in this work contributed to a new concept to improve the selectivity of easily hydrolyzable products.

Synthetic membrane selection for in vitro release testing (IVRT): A case study of topical mometasone furoate semi-solid dosage forms

In vitro release testing (IVRT) is extensively used to develop the formulation of topical semi-solid products, to evaluate the quality and consistency of the product after scale-up and post-approval changes, and more recently to aid the evaluation of topical generic products’ equivalency. The selection of synthetic membrane is one of the most critical parameters of the method development part of IVRT. It is well known that the membrane features namely its polymer matrices, porosity, pore size, thickness can have a substantial effect on the IVRT data. However, there is no detailed information available in the literature regarding the membrane selection for different types of topical dosage forms. Therefore, we aimed to investigate whether difference topical semi-solid dosage forms of the same drug molecule would cause to variation in the membrane selection. Within this framework, rheological behaviour of commercially available three different types of topical semi-solid dosage forms (ointment, cream, and lotion) of mometasone furoate (0.1%) were primarily characterized. Then, the membrane inertness test was conducted using a series of synthetic hydrophilic membranes (regenerated cellulose, cellulose acetate, cellulose nitrate, mixed cellulose ester membranes) and hydrophobic membranes (polyether sulfone, polypropylene, polytetrafluoroethylene membranes) after identifying of an appropriate receptor medium that ensures sink condition for mometasone furoate. Lastly, IVRT studies from the topical semi-solid products were performed utilizing Franz-type diffusion cells. The membrane inertness and in vitro release data demonstrated that the cellulose acetate membrane showed superior diffusion properties in general while the other synthetic membranes exhibited varying outcomes for different semi-solid dosage forms of mometasone furoate. Overall, the results indicated that the release rate and the cumulative drug released amount of drug after 6 h through the different synthetic membranes might vary depending on the semi-solid dosage form. In order to select the synthetic membrane for IVRT, it should also be considered potential interactions between the polymer matrices and the chemical structure of drug molecule as well as formulation components prior to conducting membrane inertness test and IVRT studies.

Preparation and properties of bio-based PA56/SiO2–NH2 composite nanofiber membranes for high efficiency oil-water separation

With the continuous development of environmental protection and resource recycling demands, the development of bio-based separation membrane materials has increasingly attracted attention. Bio-based polyamide 56 (PA56), exhibiting excellent hydrophilicity, spinnability, and mechanical properties, is expected to complement and replace traditional separation membrane materials. In this study, the electrospinning preparation and structural control of PA56 nanofiber membranes were achieved through the optimization of PA56 content and mixed solvent ratios. The study found that when the PA56 content was 16 wt% and the formic acid to acetone ratio in the mixed solvent was 8:2, the nanofiber diameter distribution was the most uniform. Building on this, amino-functionalized modified silica (SiO2–NH2) nanoparticles were introduced to prepare PA56/SiO2–NH2 composite nanofiber membranes featuring a cobweb-like nanofiber network and micro-nodule structure. The effects of the addition of SiO2–NH2 nanoparticles on the morphology, structure, and properties of the fiber membranes were studied. The results indicate that the control of the mixed solvent ratio and the addition of SiO2–NH2 nanoparticles led to the formation of a cobweb-like nanofiber network and micro-nano nodular structure on the nanofiber surface, enhancing the hydrophilicity of PA56 nanofiber membranes. The M − 3 membrane with a nanoparticle addition amount of 0.8 wt% exhibited high hydrophilicity and underwater superoleophobic properties, achieving efficient separation of stable oil-in-water emulsions with a separation efficiency of 99.8 %. This work provides a new bio-based membrane material and its preparation method for treating oily wastewater using the membrane separation method.

Poly(l-lactic acid) Janus Shape Memory Membranes with Uniform Vertically Penetrative Channels and Slit Pores for Enhanced Fog Collection: Synergistic Effect of Transport through Membranes and Sequential Sliding Behaviors of Water Droplets.

In this work, poly(l-lactic acid) (PLLA) Janus shape memory membranes with uniform vertically penetrative channels (SMEUVs) with slit pores have been fabricated with the help of template-assisting spray-coating and uniaxial tension at high temperature. During fog collection, superhydrophobic and hydrophilic surfaces act as the front (fog-facing) side and back side, respectively, in which the structural characteristics play essential roles. On one hand, the vertically penetrative channels in SMEUVs and the special pore geometry contribute to lower resistance, accelerating the transport of captured water through membranes (from the superhydrophobic side to the hydrophilic side). On the other hand, the movement of water droplets along the back side has been guided by the oriented structures of slit pores, promoting the detachment of droplets from the hydrophilic surface. Their synergistic effect removes captured water in a timely manner and provides fresh sites for the subsequent nucleation of water, enhancing fog collection performance. As a result, the optimal specimen (Janus SMEUVs with a draw ratio of 2.5, placed in the parallel direction) exhibits a much higher water collection rate (∼6×) relative to references (superhydrophobic and hydrophilic membranes). Our results are significant for sustainable development in view of both fog collection in arid regions and the biodegradability of PLLA.

Typical Heterotrophic and Autotrophic Nitrogen Removal Process Coupled with Membrane Bioreactor: Comparison of Fouling Behavior and Characterization.

There is limited research on the relationship between membrane fouling and microbial metabolites in the nitrogen removal process coupled with membrane bioreactors (MBRs). In this study, we compared anoxic-oxic (AO) and partial nitritation-anammox (PNA), which were selected as representative heterotrophic and autotrophic biological nitrogen removal-coupled MBR processes for their fouling behavior. At the same nitrogen loading rate of 100 mg/L and mixed liquor suspended solids (MLSS) concentration of 4000 mg/L, PNA-MBR exhibited more severe membrane fouling compared to AO-MBR, as evidenced by monitoring changes in transmembrane pressure (TMP). In the autotrophic nitrogen removal process, without added organic carbon, the supernatant of PNA-MBR had higher concentrations of protein, polysaccharides, and low-molecular-weight humic substances, leading to a rapid flux decline. Extracellular polymeric substances (EPS) extracted from suspended sludge and cake sludge in PNA-MBR also contributed to more severe membrane fouling than in AO-MBR. The EPS subfractions of PNA-MBR exhibited looser secondary structures in protein and stronger surface hydrophobicity, particularly in the cake sludge, which contained higher contents of humic substances with lower molecular weights. The higher abundances of Candidatus Brocadia and Chloroflexi in PNA-MBR could lead to the production of more hydrophobic organics and humic substances. Hydrophobic metabolism products as well as anammox bacteria were deposited on the hydrophobic membrane surface and formed serious fouling. Therefore, hydrophilic membrane modification is more urgently needed to mitigate membrane fouling when running PNA-MBR than AO-MBR.

Graphene oxide-polydopamine loaded uniform fibrous membranes via robust multi-channel microfluidic-electrospinning method

The rapid development of modern industries has caused serious water pollution such as dyes wastewater, which brings environmental problems and threatens human health. Thus, methods allowing efficient dyes removal from wastewater are substantially desirable. In this work, we fabricated graphene oxide-polydopamine (GO-PDA) by microfluidics, which enables rapid synthesis of products with excellent uniformity due to the precise control of reaction conditions. In addition, the GO-PDA/ thermoplastic polyurethane (GO-PDA/TPU) composite fibrous membrane was prepared in a high-efficiency manner by microfluidic electrospinning with a four-channel chip. Interestingly, GO-PDA not only improves the mechanical strength and hydrophilicity of the composite fibrous membrane, but also endows the membrane with efficient dye adsorption and separation capacity both for single and mixed dyes. It has been proved that the GO-PDA/TPU composite fibrous membrane exhibits selectivity towards cationic dyes, where the removal efficiency is up to 99 wt%. Moreover, the fibrous membrane could be utilized in a continuous and cyclic manner, which still maintains a high adsorption rate (>95 wt%) after 5 recycling, illustrating outstanding durability and reusability. This work proposes an efficient GO-PDA/TPU composite fibrous membrane towards selective adsorption of cationic dyes, which is of great significance in wastewater purification.

Structure and properties of homogeneous toughened poly(vinyl alcohol) blended membrane and exploration of application in membrane separation

Polyvinyl alcohol (PVA) has excellent physical and chemical properties; however, its rigidity easily leads to brittleness and breakage during use. Additionally, due to intramolecular hydrogen bonding, the dense structure of the film limits its application. This research used a self-toughening approach by homogeneously blending PVA 0588 and PVA 0499 with different molecular weights to enhance the toughness of PVA and create a porous structure for broader application in membrane separation. Porous PVA membranes were then produced through mechanical stretching. Rheological testing, differential scanning calorimetry, and dynamic thermomechanical analysis confirmed that the blend system is partially compatible. Mechanical characterization revealed that adding PVA 0499 decreased the tensile modulus, strength, and bending modulus of the blended film but increased the elongation at break, reaching a maximum of 179 %. This result indicates that homogeneous blending effectively achieved PVA self-toughening. After this, the PVA blended membrane underwent mechanical stretching. Results showed that the stretched membrane developed a porous structure with a PVA 0588 content of 60 wt%, yielding a pure water flux of 70.3 L m−2 h−1 MPa−1 and a glucan rejection rate of 91.07 %. The molecular weight cut-off test demonstrated that the resulting porous membrane was suitable for water treatment, effectively filtering substances with a molecular weight of ≥70 kDa. The membrane also exhibited notable antifouling properties. The hydrophilicity and high roughness of the porous membrane facilitated the formation of additional hydrogen bonds between the membrane surface and water molecules, thereby reducing direct contact between pollutants and the membrane surface. This study provides preliminary theoretical and experimental insights into enhancing PVA toughness and expanding its applications in membrane separation. Furthermore, homogeneous blending opens new avenues for improving the mechanical performance of polymers.

The synergistic actions of copper/l-glutamine co-grafting in improving anti-biofouling and desalination performances of reverse osmosis thin film composite membrane

There have been ongoing efforts to improve membrane surfaces by adding specific functional groups through physical or chemical approaches to minimize fouling propensity. This study introduces a facile grafting and deposition approach to enhance the performance of thin film composite polyamide reverse osmosis (TFC PA RO) membrane. The synergistic effects of l-glutamine and Cu nanoparticles in altering the physico-chemical properties and improving desalination performances were investigated. The l-glutamine improved the hydrophilicity of membrane, while Cu NPs offered significant antibacterial characteristics to improve the functionality of membrane. The findings revealed that TFC-l-glutamine/Cu3 showed optimum performance with water flux of 16.5 L.m−2 h−1 and salt rejection of 96.8 % at an operating pressure of 1.5 MPa. The TFC-l-glutamine/Cu3 membrane exhibited an absence of dense colonies against both S. aureus and E. coli, on account of the antibacterial effectiveness of Cu NPs. The S. aureus- and E. coli-fouled TFC-l-glutamine/Cu3 membrane showed the lowest flux decline of 20 % and 25 % for, respectively. The TFC-l-glutamine/Cu3 membrane exhibited promising antifouling performance, with a flux recovery ratio (FRR) of 95.2 % for bovine serum albumin (BSA) foulants. The TFC-l-glutamine/Cu3 membrane exhibited a low copper leaching of ≤3 %, suggesting its high stability. The modification strategy demonstrated in this study provides a feasible solution to simultaneously address multiple issues of TFC RO membranes, which potentially leading to more efficient desalination.

Increased Dialyzer Membrane Hydrophilicity Improves Hemocompatibility and Performance: A Randomized Investigation

Increased Dialyzer Membrane Hydrophilicity Improves Hemocompatibility and Performance: A Randomized Investigation

Energy and exergy analysis of a novel solar-powered passive multi-stage osmosis desalination system for sustainable water production

Climate change and population growth constantly exacerbate global water scarcity, and seawater desalination technology is crucial to addressing this crisis. Conventional fossil-fuel desalination poses environmental and economic challenges, especially in remote, water-scarce regions. Renewable energy offers sustainable options for seawater desalination; however, most related technologies face challenges in flexible deployment. Among passive technologies, interfacial evaporation still confronts issues of salt accumulation impacting desalination efficiency. Therefore, this study investigates a novel solar-powered passive multi-stage osmosis device that emulates mangroves’ transpiration and natural osmosis processes. Harnessing solar energy, it employs hydrophilic nanoporous membranes for water movement and evaporation and an osmosis membrane for solute retention, aiming for efficient seawater desalination without external power and pressure. Energy and exergy analyses reveal key efficiency factors. Results reveal significant pressure gradients across the osmosis membrane as a challenge. Optimizing salinity and adjusting the area ratio of the nanoporous membrane to the osmosis membrane is vital for stability and performance. Moreover, potential increases in water production from 0.97 kg/m2/h to 3.53 kg/m2/h with a five-stage setup, though benefits diminish with additional stages due to heat/exergy losses. The exergy efficiency increases from 0.14 % for a five-stage device to 0.18 % for a ten-stage system. This study demonstrates the solar-powered passive multi-stage osmosis device’s dependence on solar flux and highlights the importance of optimizing the air gap thickness and insulation to boost efficiency.

Multienzyme Immobilization on PVDF Membrane via One-Step Mussel-Inspired Method: Enhancing Fouling Resistance and Self-Cleaning Efficiency.

Immobilizing different enzymes on membranes can result in biocatalytic active membranes with a self-cleaning capacity toward a complex mixture of foulants. The membrane modification can reduce fouling and enhance filtration performance. Protease, lipase, and amylase were immobilized on poly(vinylidene fluoride) (PVDF) microfiltration membranes using a polydopamine coating in a one-step method. The concentrations of polydopamine precursor and enzymes were optimized during the immobilization. The higher hydrolytic activities were obtained using 0.2 mg/mL of dopamine hydrochloride and 4 mg/mL of enzymes: 0.90 mgstarch/min·cm2 for amylase, 10.16 nmoltyrosine/min·cm2 for protease, and 20.48 µmolp-nitrophenol/min·cm2 for lipase. Filtration tests using a protein, lipid, and carbohydrate mixture showed that the modified membrane retained 41%, 29%, and 28% of its initial water permeance (1808 ± 39 L/m2·h·bar) after three consecutive filtration cycles, respectively. In contrast, the pristine membrane (initial water permeance of 2016 ± 40 L/m2·h·bar) retained only 23%, 12%, and 8%. Filtrations of milk powder solution were also performed to simulate dairy industry wastewater: the modified membrane maintained 28%, 26%, and 26% of its initial water permeance after three consecutive filtration cycles, respectively, and the pristine membrane retained 34%, 21%, and 7%. The modified membrane showed increased fouling resistance against a mixture of foulants and presented a similar water permeance after three cycles of simulated dairy wastewater filtration. Membrane fouling is reduced by the immobilized enzymes through two mechanisms: increased membrane hydrophilicity (evidenced by the reduced water contact angle after modification) and the enzymatic hydrolysis of foulants as they accumulate on the membrane surface.

Manufacture and performance assessment of PVDF-La@TiO2 Photocatalyst implanted membrane for efficient produced water treatment via ozonation-adsorption process under visible-light exposure

This research aims to develop a visible light-activated photocatalytic membranes for produced water treatment system by employing the phase inversion technique for implantation of La@TiO2 photocatalytic nanoparticles into PVDF membrane at concentrations varying from 0 % to 2 % wt. The results demonstrated significant amplification of COD and NH3-N removal efficiency. Implantation of the photocatalyst into PVDF membranes via bulk mixing, coupled with elemental doping and combination with La@TiO2 appreciably reduces band gap energy and increases visible light absorption thereby improves membrane's optical properties. SEM-EDX analysis confirms uniform distribution of La@TiO2 nanoparticles on the membrane surface, which leads to amplify membrane's hydrophilicity and water absorption. The modified membrane facilitated concurrent photocatalytic degradation and filtration processes that lead to remarkable reductions in TDS, COD, and NH3-N pollutants, with the highest flux was achieved when 1.5 % wt. La@TiO2 was incorporated into the membrane matrix. Obviously, adsorption and ozonation processes promote synergistic effect and amplify pollutant flux and efficiency to a greater extent. Furthermore, the modified membrane exhibited extraordinary antifouling properties and stability, providing excellent reusability with a 96.22 % fouling reduction rate after five consecutive cycle tests.

Alkoxy-functionalized covalent organic Framework membranes for efficient molecular sieving with high water permeance

The presence of various trace water-soluble organic pollutants, such as dyes, poses significant potential risks to human health and ecosystems. Membrane technology presents a promising and sustainable approach for their removal from aqueous environments. However, the amorphous structure of most commercial membranes makes it challenging to achieve effective separation with high water flux. Here, we present a novel series of hydrophilic COF membranes with different alkoxy sidechain lengths for the first time. These alkoxy sidechain functional COF membranes exhibit efficient rejection of water-soluble organic dyes, including rose bengal (> 50 %), congo red (> 98 %), brilliant blue R250 (> 99 %), and alcian blue (> 99 %). Moreover, these membranes demonstrate a high water flux exceeding 291.8 L m-2h−1 bar−1 and exceptional long-term operational stability lasting at least 2880 min. The superior performance of COF membranes is attributed to their optimal pore size, excellent hydrophilicity, and high crystallinity. This finding offers a promising approach for effectively eliminating water-soluble organic pollutants, thereby ensuring the safety and sustainability of the water supply.

Swelling-assisted surface grafting strategy for multichannel antifouling membranes: Reconstruction of surface pore structure and applications in microalgae harvesting and blood purification

Membrane fouling remains a major challenge in membrane separation. The modification of hydrophilic membrane surfaces can mitigate irreversible fouling deposition, thereby improving antifouling properties. Effective surface modification strategies are essential techniques for developing highly efficient antifouling membranes. In this work, a swelling-assisted surface grafting strategy was proposed for multichannel antifouling membranes, where various lengths of polyvinylpyrrolidone (PVP) brushes were grafted on the surface of polysulfone membrane using reversible addition-fragmentation chain transfer polymerization. The successful grafting of PVP polymer brushes was confirmed using Fourier transform infrared spectrometer and X-ray Photoelectron Spectroscopy. Changes in membrane morphology and pore structure were observed via scanning electron microscope and atomic force microscope. During the grafting process, the amphiphilic macromolecules formed through grafting were selectively swelled by graft solvent, leading to the formation of mesopores in both the surface layer and sublayer of the membrane, which formed additional water transport channels. The introduction of hydrophilic polymer brushes and the change of pore structure significantly boosted the hydrophilicity and permeability of the membranes. As a result, the water contact angle decreased from 85° to 42°, accompanied by an approximate 3.24-fold increase in pure water flux (PWF). Due to superior hydrophilicity, modified membranes demonstrated exemplary performance in microalgae harvesting, boasting a microalgae retention rate nearing 100 % and low fouling resistance (2.12 × 1012 m−1). In algal filtration experiments, a confocal laser scanning microscope was employed to assess the activity of filtered algae on the membrane surface. The prepared membranes effectively maintained the bioactivity of algae while also achieving a high flux recovery rate (90.7 %) following filtration and cleaning. Furthermore, in blood cell compatibility tests, the modified membranes exhibited resistance to blood cell adhesion and sustained a low hemolysis rate (0.06 %). Overall, this strategy offers unique insights into the fabrication of antifouling surfaces and shows considerable promise for large-scale applications in microalgae harvesting and blood purification.