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PVDF membrane has strong hydrophobicity and low anti-pollution performance, greatly limiting its practical application. These drawbacks have been successfully overcome by designing and then preparing a membrane with a semi-interpenetrating polymer (semi-IPN) of PVDF/poly(acrylic acid) (PAA) as the membrane matrix, TiO2 nanoparticles as functional components and F127 as pore-forming agent. The semi-IPN was prepared by copolymerizing acrylic acid with N,N methyl acrylamide in the presence of PVDF, and the TiO2 gel nanoparticles were in situ formed in the membrane-forming process. The properties of the composite membrane were significantly affected by the semi-IPN, F127 and TiO2. By adjusting the membrane structure with the semi-IPN, F127 and TiO2 nanoparticles, we prepared a composite membrane with a water contact angle of 40o, a BSA rejection ratio of 87.5% and a water flux of 802.5 L/m2/h/bar. After a simple UV irradiation, the water flux of this composite membrane rose to 1030 L/m2/h/bar, without any rejection decline. The membrane contaminated by humic acid could recover the water flux up to above 95.3% of its original value by a single UV irradiation, showing a very good antifouling performance. In addition, the composite membrane also exhibited a very strong pollution resistance and separation performance for bovine serum albumin and oil-water emulsion. All in all, based on the synergy of the semi-IPN and the evenly dispersed TiO2 nanoparticles, the prepared composite membrane exhibited excellent comprehensive properties and demonstrated a great potential for various separation applications.

The high concentrations of heavy metal ions in industrial effluents are one of the most challenging wastewaters to deal with. In this study and in order to change the inner diameter of the halloysite nanotubes (HNT), their internal surface was coated by different polymers (polydopamine, polyaniline and polystyrene) and then, the modified nanotubes were incorporated in the polyamide thin film NF membrane for the treatment of metal ions solutions. Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) studies indicated that the internal coating was successful. Furthermore, the neat and modified nanofiltration (NF) membranes were characterized in terms of morphology, contact angle, water flux and metal ion rejection. The modified membranes displayed lower contact angle values (29.4% reduction) that can be linked to the hydrophilic groups in the structure of the coated polymers and the smoother surface of the thin film nanocomposite (TFN) membrane. In addition, the permeation fluxes of the modified membranes were improved significantly (33.4% improvement) without any major reduction in their ion rejection; that shows HNTs act as the channels to transfer water through the membrane structure while the coating of the inner surface of HNT reduces the size of the channel and makes more repulsion and steric hindrance for the ion to pass through the nanotubes. Among the fabricated membranes, the NF membrane with 0.05 wt% polystyrene-coated HNT showed the lowest contact angle (55.30o) and the highest water permeation flux (27.51 L m-2 hr-1), compared to the neat TFC membrane (15.26 L m-2 hr-1) and the NF membrane with 0.05 wt% unmodified HNT (20.62 L m-2 hr-1).

In this study, poly (ether-block-amide) (Pebax) facilitated transport membranes (FTMs) containing aniline, and ionic liquid (IL) modified alumina (M-Al) particles were prepared. Aniline molecules acted as semi-mobile carriers and IL-modified particles as fixed carriers for CO2 molecules in these membranes. Different amounts of M-Al particles were added to the Pebax/aniline (50 wt%) membrane, and a facilitated transport membrane containing 5 wt% M-Al particles was obtained as the optimal membrane. For Pebax/aniline (50 wt%)/M-Al (5 wt%) membrane, CO2 permeability was 167 barrer, and CO2/N2 selectivity was 123 increased by 94% and 168% compared to pure Pebax membrane, respectively. The CO2 separation performance of the prepared FTMs was also evaluated in the humidified state. The results showed that in the presence of water, the amino groups in the structure of aniline and IL performed better and improved the facilitated transport mechanism. Therefore, for all FTMs, CO2 permeability significantly increased in the humidified state so that CO2 permeability and CO2/N2 selectivity reached 406 barrer and 123, respectively, for optimal membrane. The molecular simulation was used to study details of the motion of aniline molecules in the polymeric matrix. The simulation and experimental results confirmed each other and showed that the presence of aniline prevents the hopping mechanism from stopping even at low concentrations of particles as fixed carriers and creates a combined hopping-vehicle mechanism in the membrane structure that results in excellent performance membranes.

Mixed matrix membranes (MMMs) of cellulose acetate/poly(vinylpyrrolidone) (CA/PVP) infused with acid functionalized multiwall carbon nanotubes (f-MWCNTs) were fabricated by an immersion phase separation technique for hemodialysis application. Membranes were characterized using FTIR, water uptake, contact angle, TGA, DMA and SEM analysis. The FTIR was used to confirm the bonding interaction between CA/PVP membrane matrix and f-MWCNTs. Upon addition of f-MWCNTs, TGA thermograms and glass transition temperature indicated improved thermal stability of MMMs. The surface morphological analysis demonstrated revealed uniform distribution of f-MWCNTs and asymmetric membrane structure. The water uptake and contact angle confirmed that hydrophilicity was increased after incorporation of f-MWCNTs. The membranes demonstrated enhancement in water permeate flux, bovine serum albumin (BSA) rejection with the infusion of f-MWCNTs; whereas BSA based anti-fouling analysis using flux recovery ratio test shown up to 8.4% improvement. The urea and creatinine clearance performance of MMMs were evaluated by dialysis experiment. It has been found that f-MWCNTs integrated membranes demonstrated the higher urea and creatinine clearance with increase of 12.6% and 10.5% in comparison to the neat CA/PVP membrane. Thus, the prepared CA/PVP membranes embedded with f-MWCNTs can be employed for wide range of dialysis applications.

Nanofiber membranes have outstanding potential for filtration applications due to their great specific surface area, high porosity, and modifiable structure. Compared to conventional membranes, nanofiber membranes offer substantial high flux and high rejection ratios. This paper provides a comprehensive analysis on the filtration performance of plasma treatment on the polyacrylonitrile nanofiber membrane. The pores in the original membrane were utilized about a mere 10%, while those of the plasma-irradiated membrane were utilized nearly 60%. The membrane modification was performed using N2, O2, and Ar plasma. It was found that Ar plasma was most effective for etching the membrane structure. Fourier transform infrared spectroscopy was applied to detect the chemical changes on the membranes. The contact angle of the water droplets on the original membrane was 96.1°; however, after the Ar plasma treatment, it declined to 0°. Finally, the particle retention details in different cross sections of the filtered membranes were observed via a scanning electron microscope. The main innovation is to clarify the changes in the mechanism of the nanofiber membrane trapping particles before and after plasma treatment. In the filtration test after plasma treatment, the internal space of the membrane was fully and effectively utilized, and the flux was also improved. The obtained results suggest a potential application of the plasma-treated nanofiber membrane in water treatment.

Zero-dimensional carbon dots have emerged as important nanofillers for the separation membrane due to their small specific size and rich surface functional groups. This study proposed a strategy based on hydrophobic carbon dots (HCDs) to regulate water channels for an efficient forward osmosis (FO) membrane. Thin-film composite (TFC) membranes with superior FO performance are fabricated by introducing HCDs as the nanofiller in the polyacrylonitrile support layer. The introduction of HCDs promotes the formation of the support layer with coherent finger-like hierarchical channels and micro-convex structure and an integrated polyamide active layer. Compared to the original membrane, TFC-FO membrane with 10 wt% HCDs exhibits high water flux (15.47 L m−2 h−1) and low reverse salt flux (2.9 g m−2 h−1) using 1 mol/L NaCl as the draw solution. This improved FO performance is attributed to the lower structural parameters of HCDs-induced water channels and alleviated internal concentration polarization. Thus, this paper provides a feasible strategy to design the membrane structure and boost FO performance.

MXenes, two-dimensional metal carbides or nitrides with multifunctional surfaces, are one of the most promising antibacterial nanoscale materials. However, their putative bactericidal mechanism is elusive. To study their bactericidal mechanism, we investigated the interaction between a MXene nanosheet and a model bacterial membrane by molecular dynamics simulations and found that an adsorbed MXene on a membrane surface induced a local phase transition in a domain where the fluidity of the phospholipid in this domain at room temperature was comparable with that of the gel phase. The domain also showed a denser and thinner phospholipid membrane structure than the peripheral phospholipids. By comparing it with our previous experiments of the bactericidal activity of MXenes, we proposed the leakage of intercellular molecules at the phase boundary defects as a possible bactericidal mechanism of MXenes that leads to cell lysis. This study provides a useful model for tailoring new bactericidal nanomaterials.

The incorporation of various nanofillers into the interfacial polymerization (IP) process is widely applied to prepare higher performance NF membranes. However, few studies have reported the influence of nanofillers on nanocomposite membrane formation in the IP process. Here, an optical microscope was employed to study the change rule in the 8-NH2-POSS/PSA nanocomposite membrane formation process due to the addition of 8-NH2-POSS nanoparticles. First, the addition of 8-NH2-POSS reduced the diffusion rate of the polyacrylamide hydrochloride (PAH) water phase on the surface against the oil phase because of the interaction with the PAH molecules. Furthermore, the 8-NH2-POSS/PSA nanocomposite membrane structure was more homogeneous and exhibited uniform pinhole defects distribution due to the interaction of the 8-NH2-POSS nanoparticles to the PAH segment. A significant separation performance was observed in the 8-NH2-POSS/PSA nanocomposite membrane due to the hydrophilicity and positive charge of the 8-NH2-POSS nanoparticles. The permeation flux and MgCl2 rejection of the 8-NH2-POSS/PSA nanocomposite membrane increased up to 50.5 L/m2 h at 0.5 MPa and 94.8%, respectively, which corresponded to increases of 73.5% and 8.7% as compared to the pristine PSA membrane. 8-NH2-POSS/PSA nanocomposite membranes have great application potential in the water softening and treatment of divalent metals ions under acidic conditions.

Purpose The study aims to focus on the preparation of a heterogeneous cation exchange membrane by a three-dimensional (3D) method – fused filament fabrication using a series of nozzles of various diameters (0.4–1.0 mm). Polypropylene random copolymer (PPR) as a polymeric binder was mixed with 50 Wt.% of the selected conventional cation exchange resin, and a filament was prepared using a single screw mini extruder. Then filament was processed by FFF into the membranes with a defined 3D structure. Design/methodology/approach Electrochemical properties, morphology, mechanical properties and water absorption properties were tested. Findings Dependence of the tested properties on the used nozzle diameter was found. Both areal and specific resistances increased with increasing nozzle diameter. The same trend was also found for permselectivity. The optimal membrane with permselectivity above 90%, areal resistance of 8 O.cm2 and specific resistance of 124 O.cm2 was created using a nozzle diameter of 0.4 mm. Originality/value Using new materials for 3D print of cation exchange membrane with production without waste. The possibility of producing 3D membranes with a precisely defined structure and using a cheap 3D printing method. New direction of membrane structure formation. 3D-printed heterogeneous cation exchange membranes were prepared, which can compete with commercial membranes produced by conventional technologies. 3D-printed heterogeneous cation exchange membranes were prepared, which can compete with commercial membranes produced by conventional technologies.

Current thin film nanocomposite membranes incorporated with microporous particles are demanding for improving membrane performance. In this study, carbon nanotubes (CNTs)-modified poly(ethyleneimine) (PEI)/sodium lignosulfonate (SL) membranes were prepared through layer-by-layer assembly by dispersing CNTs into PEI and/or SL solutions, in order to investigate the effects of CNTs on membrane structure and forward osmosis performance. The characterization results indicated that the CNTs can be well-incorporated in the PEI/SL membranes, which contribute to a slightly lower hydrophilicity of membrane surface and different membrane morphology. The forward osmosis performance of the PEI/SL and CNTs-modified PEI/SL membranes were investigated for application in separating NaCl from water. Compare with the PEI/SL membrane, PEI/(SL–CNTs) membrane prepared by dispersing CNTs into the SL solution exhibited the best water flux and membrane selectivity. The increase in the CNTs content of the PEI/(SL–CNTs) membrane can enhance the water flux, but cannot significantly impact on the reverse salt flux, resulting in the improvement in membrane selectivity. The PEI/(SL–CNTs) membrane containing 0.075 g L−1 CNTs in SL showed a 66.3% higher water flux of 7.32 LMH, also exhibited better antifouling and foulant-release properties. This study offers a new method to design novel FO membranes for desalination and water purification.

Metal-organic framework (MOF) materials have received extensive attention for the design of advanced thin-film nanocomposite (TFN) membranes with excellent permselectivity. However, the relationship between the unique physicochemical properties and performance of engineered MOF-based membranes has yet to be extensively investigated. In this work, we investigate the incorporation of porous zinc-based MOFs (Zn-MOFs) into a polyamide active layer for the fabrication of TFN membranes on porous poly(phenylsulfone) (PPSU) support layers through an interfacial polymerization approach. The actual effects of varying the amount of Zn-MOF added as a nanofiller on the physicochemical properties and desalination performance of TFN membranes are studied. The presence and layout of Zn-MOFs on the top layer of the membranes were confirmed by X-ray photoelectron spectroscopy, scanning electron microscopy, and ζ potential analysis. The characterization results revealed that Zn-MOFs strongly bind with polyamide and significantly change the membrane chemistry and morphology. The results indicate that all four studied TFN membranes with incorporated Zn-MOFs enhanced the water permeability while retaining high salt rejection compared to a thin-film composite membrane. Moreover, the highest-performing membrane (50 mg/L Zn-MOF added nanofiller) not only exhibited a water permeability of 2.46 ± 0.12 LMH/bar but also maintained selectivity to reject NaCl (>90%) and Na2SO4 (>95%), similar to benchmark values. Furthermore, the membranes showed outstanding water stability throughout 72 h filtration and chlorine resistance after a 264 h chlorine-soaking test because of the better compatibility between the polyamide and Zn-MOF nanofiller. Therefore, the developed TFN membrane has potential to solve trade-off difficulties between permeability and selectivity. Our findings indicate that porous Zn-MOFs play a significant role in the development of a TFN membrane with high desalination performance and chlorine resistance.

Chlorosulfolipids (CSLs) are major components of flagellar membranes in sea algae. Unlike typical biological lipids, CSLs contain hydrophilic sulfate and chloride groups in the hydrocarbon tail; this has deterred the prediction of the CSL membrane structure since 1960. In this study, we combine coarse-grained (CG) and atomistic molecular dynamics (MD) simulations to gain significant insights into the membrane structure of Danicalipin A, which is one of the typical CSLs. It is observed from the CG MD that Danicalipin A lipids form a stable monolayer membrane structure wherein the hydrocarbon moieties are sandwiched by hydrophilic sulfate and chloride groups in both the head and tail regions. On the basis of the mesoscopic structure, we built the corresponding atomistic model to investigate the integrity of the CSL monolayer membrane structure. The monolayer membrane comprising bent lipids shows high thermal stability up to 313 K. The gel-liquid crystalline phase transition is observed around 300 K.

As an alternative to the energy-intensive evaporation-crystallization method, membrane distillation crystallization (MDC) was applied for the first time to obtain calcium nitrate crystals from its aqueous solution. Calcium nitrate solution was obtained through the reaction between calcium carbonate and nitric acid, and then it was concentrated in the membrane distillation (MD) process and further crystallized. The MD step was conducted using hydrophobic polyvinylidene fluoride (PVDF)/sorbitan trioleate (Span 85) membranes. Span 85 was incorporated into the membrane structure in various concentrations to improve the hydrophobicity of membranes, and the resultant membranes were characterized via different methods. In addition, the resultant calcium nitrate crystals were characterized by X-ray fluorescence (XRF) spectroscopy. The MDC results showed that the optimum amount of Span 85 in the polymeric solution was 4%, which led to the formation of a membrane with higher porosity (67.2%) and water contact angle (95.7°) compared to the neat PVDF membrane. The mentioned membrane exhibited the highest water flux in the MD process compared to the other membranes, and also it produced the highest amount of crystals due to its remarkably better performance in the MD step in terms of feed concentration.

The paper presents the results of an experimental study on the effect of high pressures on the transport of liquids through a composite reverse osmosis membrane of an AG-90 industrial membrane module (GE Water & Process Technologies), which membrane consists of a microporous substrate (polysulfone) coated with a selective polyamide layer. It has been found that when a “philic” liquid (water) is forced through the membrane, permeability changes nonlinearly with increasing pressure and passes through an extremum at 7.5 MPa. For the membrane from the AG-90 module, hysteresis during the pressure increasing–decreasing cycle has been observed, which can be associated with irreversible deformation of the membrane structure by interaction with water at high pressures. For “phobic” liquids (glycerol, propanol-1, and propanol-2), the membrane permeability decreases nonlinearly with increasing pressure and this change can be explained in terms of known transport models.

A novel mixed-matrix-composite (MMC) membrane was prepared by incorporating a novel SiO2@CuFe2O4 nanocomposite with a tunable antibacterial property which is synthesized via hydrothermal method, into the pristine membrane structure, in order to achieve the high dye removal performance and antibacterial properties. The results indicated that adding SiO2@CuFe2O4 nanocomposite improved the hydrophilicity, antifouling, and antibacterial properties. The performance of the MMC membranes were evaluated in terms of pure water flux and dye rejection in the filtration process by use of two anionic dyes as the contaminants. The MMC membrane containing 1wt% SiO2@CuFe2O4 nanocomposite, the water flux was about 23 L m−2 h−1and the rejection values were approximately reached to 99% for the both anionic dyes. Also, during the long-term filtration test for stability investigation, the separation efficiencies were maintained with the values of 99.88% Direct blue 199 and 88.99% Acid blue 25 dyes, comparing with the initial time of the filtration performance. High antifouling properties of the MMC membranes, increased the flux recovery ratio (FRR) up to 95%, which is a significant improvement comparing with the neat PES membrane with the value of 65%. The MMC membranes exhibited the relatively high antibacterial activity against Staphylococcus aureus and Escherichia coli bacteria via colony forming unit and disc diffusion methods.

Pulping and papermaking generate large amounts of waste in the form of lignosulfonates which have limited valorized applications so far. Herein, we report a novel lignosulfonate‐based nanofiltration membrane, prepared by using polyethylenimine (PEI) and sodium lignosulfonate (SL) via a layer‐by‐layer (LbL) self‐assembly. As a low‐cost and renewable natural polyelectrolyte, SL is selected to replace the synthetic polyelectrolyte commonly used in the conventional LbL fabrication for composite membranes. The prepared LbL (PEI/SL)7 membranes were crosslinked by glutaraldehyde (GA) to obtain (PEI/SL)7‐GA membranes with compact selective layer. We characterized (PEI/SL)7 and (PEI/SL)7‐GA membranes to study the chemical compositions, morphologies, and surface hydrophilicity. To improve the nanofiltration performances of the (PEI/SL)7‐GA membranes for water desalination, we investigated the effects of the crosslinking time, GA concentration and the NaCl supporting electrolyte on membrane structure and performance. The optimized (PEI/SL)7‐GA membrane exhibited a permeating flux up to 39.6 L/(m2·h) and a rejection of 91.7% for the MgSO4 aqueous solution 2.0 g/L concentration, showing its promising potential for water desalination. This study provides a new approach to applying the underdeveloped lignin‐based biomass as green membrane materials for water treatment.

Crosslinker is a vital factor for the preparation of polymeric membranes, which has a substantial effect not only on the membrane-forming process, but also on the membrane structure as well as separation performance. However, little attention has been paid on UV-crosslinked membrane for organics pervaporation. In this work, the effect of crosslinker 3-methacryloxypropylmethyldimethoxysilane (KH571) on (1) the UV-crosslinking kinetics was characterized by real-time infrared spectroscopy and photo-rheology, (2) the membrane structure was characterized by crosslinking density, and (3) separation performance was evaluated by ethanol pervaporation. Moreover, the conventional polydimethylsiloxane (PDMS) was replaced by polydimethylsiloxane-poly[(3,3,3-trifluoropropyl)methylsiloxane] (PDMS-PTFPMS) block copolymer, where the strong C–F bond contributes to enhance membrane hydrophobicity. Results show an ultrafast membrane-forming process (30−50 s) for all coating solution systems and an outstanding separation performance, including 11.3 of ethanol separation factor and 1149 g m−2 h-1 of total flux for pervaporation recovery of 5 wt% ethanol/water solution at 60 °C.

The development of microorganisms and formation of thrombus on a biomaterial surface can seriously lead to device failure and threaten human health. Nonetheless, a surface that has both antibacterial and anticoagulant properties has scarcely been developed. Herein, a novel dual-action membrane composed of polyethersulfone (PES) bulk material and a hydrophilic anionic poly-2-acrylamido-2-methylpropanesulfonic acid (PAMPS) polymer has been prepared via the cationic antibacterial agent poly(hexamethylene biguanide) (PHMB)-induced phase separation technique. Interestingly, the resultant membrane can offer tunable antibacterial and anticoagulant properties, while maintaining satisfactory permeability and greatly increasing selectivity. The membrane also shows excellent hydrophilicity, a well-defined porous surface, and cross section with a sponge gradient structure. Furthermore, the PHMB-PAMPS complex formed on the membrane surface displays outstanding long-term stability, which is crucial for further practical applications. More importantly, the hollow fiber membrane fabricated by the cationic polyelectrolyte-induced phase separation technique confirms its capability to control the membrane permeability (257.4 L·m-2·h-1·bar-1) and selectivity (95.9%) without destroying the membrane structure. The present work opens a straightforward and efficient avenue for the rational design of a functional surface to fight biomedical material-associated infections.

The thermobaric and concentrational stresses, which arise during the operation of a membrane element under cyclic conditions, can result in the violation of the integrity of a membrane comprising an element and in failure of the element. Studies of the effect of thermobaric cycling in a hydrogen atmosphere at operating parameters (pressure differential, temperature, time of operation) on the properties of membranes allow us to determine the optimum operation conditions of the membrane element. The stability of the Pd–6 wt % In–0.5 wt % Ru–1 wt % Co membrane structure is estimated using the studied temperature dependence of the specific hydrogen permeability of the membrane during its operation in a hydrogen atmosphere, and the possibility of efficient operation of the membrane under given conditions in a temperature range of 250–600°C is noted. The surface of the Pd–6 wt % In–0.5 wt % Ru–1 wt % Co membrane subjected to thermobaric cycling in a commercial-purity hydrogen atmosphere is studied by atomic force microscopy and X‑ray diffraction analysis.

We report on the fabrication of the defect-free mixed-matrix membrane (MMM) based on the polyethylenimine (PEI) matrix with uniformly dispersed metal-organic framework (MOF) filler UiO-66-NH2, covalently bonded by polyvinylpyrrolidone (PVP). The key feature of the molecular level-controlled filler deposition in prepared UiO-66-NH2-PVP-PEI membranes was bridging the MOF particles to the PEI polymer matrix via PVP polymer chains. Such an approach improved the polymer-filler interface interactions and boosted the MOF dispersion into the polymer matrix for higher MOF loadings up to 23 wt %. The overall membrane structure and properties were characterized using FTIR, XRD, TG, DSC, SEM and 3D optical profiler techniques. Obtained results revealed the uniform dispersion of UiO-66-NH2, the strong polymer-filler interface interactions and entanglement of PEI with UiO-66-NH2-PVP. Furthermore, the outstanding CO2/H2 separation performance was determined for the UiO-66-NH2-PVP-PEI membrane with 18 wt % of MOF loading; the average CO2 permeability of 394 Barrer and the separation factor of 12 for circa 100 h of the membrane testing overcome the 2008 Robeson reverse upper bound limit. Such improved CO2/H2 separation performance was achieved due to the combination of the diffusion-solution mechanism with the preferential adsorption of the CO2 via the reversible bicarbonate reaction with amino groups of the UiO-66-NH2 and PEI which acts as fixed CO2 carrier sites in MMM structure.

Polysulfone is among the polymers known for excellent electrical resistivity, elongation capacity, transparency and thermal resistance. Polysulfone is being used in battery caps, oil pumps, oil control pistons, transmission parts, water treatment, etc. The focus of the presented work is to control the porosity level of polysulfone membranes through plasma treatment for water treatment application. Polysulfone membrane was fabricated using phase inversion method and treated with microwave plasma of oxygen under fixed plasma conditions. The membrane samples were plasma treated for 15 s to 30 s and analyzed for surface morphology, pore size distribution and functional groups. Presence of benzene rings, sulfonic groups and phenols groups in the samples were observed in a range of 855–1000 cm−1, 1290–1360 cm−1 and 3250–3420 cm−1, respectively. The blank sample had wider pore size distribution (3–18 µm) while plasma treated samples exhibited narrow pore size distribution. The pore size distribution after 15 s and 30 s of treatment ranged from 3 to 9 µm and 3 to 5 µm, respectively. Conclusively, uniform pore size distribution was possible after 30 s of plasma treatment.

The implementation of the pore-forming agent in the polymeric membrane has been applied for ages in enhancing the characteristics and performance of mixed matrix membrane. In this work, chlorophyll extracted from spinach has been used as an additional pore-forming agent alongside polyethylene glycol (PEG) to improve the polysulfone's pore structure (PSf) mixed matrix membrane. The effect of chlorophyll was investigated in terms of characteristics and performance of the mixed matrix membrane. As a result, the cross-section morphologies show that the pore structure was enhanced significantly inside the membrane structure for 0.25 wt% chlorophyll concentration, thus resulted in better hydrophilicity, surface roughness, and membrane porosity value. Plus, the permeation and rejection performance was increased drastically due to the pore formation inside the mixed matrix membrane structure. These results prove that the addition of chlorophyll with low concentration managed to improve the characteristics and performance of the fabricated mixed matrix membrane.

The non-solvent induced phase separation (NIPS) method is often used to fabricate porous polymer membranes that have a wide variety of applications in the fields of purification and energy materials. Such applications typically require membranes with a well-controlled pore structure across multiple levels of structural hierarchy. However, with the NIPS method, the membrane porosity is typically restricted to a single structural level due to the use of just one type of templating agent, commonly a polymer amphiphile. To overcome this limitation, here we report a new dual-template approach to embed multilevel porosity into poly(ethersulfone) membranes. In this approach, the polymer amphiphile Pluronic® F127 (F127) is used to template the higher level structure (10 μm scale), while a secondary molecular template, 4-(phenyl)azobenzoic acid (PABA), is simultaneously introduced to enable structural control at the 1 μm level. Analysis of the membrane structure by scanning electron microscopy revealed that F127 creates larger finger-like pores, while PABA introduced a more fibrous, interconnected porous sub-structure. Contact angle measurements showed that the PABA additive increases the hydrophilicity of the resultant membranes, while dead-end permeability measurements demonstrated that the hierarchical pore structure results in a 95% increase in permeability compared to a single level pore structure. Solvent extraction studies revealed that quantitative removal of the PABA template could be achieved, without any modification to the secondary level pore structure. This process offered the benefit of removing flakes of crystallized PABA from the larger, finger-like pores, leading to a further 300% increase in permeability. Given the simplicity and versatility of the NIPS method, this dual-template approach presents an efficient route to hierarchically structured, porous polymer membranes whose properties may be tailored for a targeted application.

Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N2 permeation, overall porosity, critical water entry pressure (CEPw), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N2 permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m−1. CEPw of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m−2·h−1 which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.

The stability of graphene oxide (G-O) membranes in water can be enhanced via the simple addition of metal-cations to the planar laminate structure, however, the relationship between valency and hydration radius and the properties and performance of the membrane structure is unclear. This study examines the impacts of adsorbed monovalent (K+ and Na+), divalent (Cu2+ and Mn2+) and trivalent (Al3+, Fe3+ and La3+) cations on permeation for G-O membranes in water vapor permeation and pervaporation. Metal-cations with high electronegativity and a small hydration radius possess greater binding strength that constrains the G-O laminate channels (d-spacing). Both water permeation methods show a positive trend between permeation and interlayer spacing for metal-cations with the same valency. Amongst the different valence states, steric exclusion from cations is dominant for minimal water layers (water vapor permeation), while the ability for cations to attract and hold water molecules inside its outer shell has a greater effect on swollen channels (pervaporation). These findings help pave the road towards G-O based applications in next generation water filtration methods for desalination and wastewater treatment.

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°.

One-pot synthesis of novel hydrogel-based anion exchange membranes (AEMs), with only a single-phase monomer mixture, was used to eliminate surface heterogeneity and generate reproducible electroconvective microvortices in the over-limiting region of the current-voltage characteristic (CVC) curves. Diallyldimethylammonium chloride (DDA) was used as the main component to provide the cation charge groups, and 2-hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethyl acrylate (EGDMA) were used as the auxiliary structure monomers. The uniform membrane structure allowed reproducible and sensitive DNA detection and quantification, as probe-target surface complexes can gate the ion flux and produce large voltage shifts in the over-limiting region. Suppressed membrane curvature due to controlled swelling is a crucial part to avoid the reduction of depletion region for maintaining the influence of target gene hybridization. Fourier-transform infrared (FTIR) spectroscopy verified the synthesized membrane structure, with a residual vinyl group that allows easy carboxylation via additional photografting reaction. Consequently, a significantly higher DNA probe functionalization efficiency is obtained on the homogeneous AEMs, evidenced by the increasing nitrogen element content and bonding via X-ray photoelectron spectroscopy (XPS). The DDA content was optimized to provide a sufficient coulomb force between AEM and nucleic acid backbone to promote the specific binding efficiency but without high dimensional swelling which might change the surface geometry and restrict the voltage shifting for sensing in the over-limiting region, and the optimal DDA/HEMA ratio was found to be 4/10. The synthesized AEM sensor for recombinant 35S promoter sequence identification exhibited a reproducible calibration standard curve with dynamic range between 30 fM and 1 μM and high selectivity with only 0.01 V shift for 1 μM nontarget oligo.

The effect of the addition of triblock copolymer polyethylene glycol (PEG)–polypropylene glycol (PPG)–polyethylene glycol (PEG) (Pluronic F127) and polyethylene glycol (PEG-4000, Mn = 4000 g mol−1) to the polysulfone (PSF) casting solution on the membrane structure and performance was studied. The phase state, viscosity and turbidity of PSF solutions in N,N-dimethylacetamide (DMAc) with the addition of block copolymer Pluronic F127 were investigated. It was found that 18–22 wt.% PSF solutions in DMAc with Pluronic F127 content ≥ 5 wt.% feature a lower critical solution temperature (LCST). Membrane structure was investigated using scanning electron and atomic force microcopies. It was revealed that average pore size and pore amount on the surface of the membrane selective layer increase and pore size distribution becomes wider with an increase in Pluronic F127 content in the casting solution. It was found that the average surface roughness parameters of the membrane selective layer for PSF/Pluronic F127 membranes significantly exceed those for PSF/PEG-4000 membranes. It was shown that the increase in the membrane flux and the decrease in polyvinylpyrrolidone (PVP K-30, Mn = 40,000 g mol−1) rejection are a result of the addition of both Pluronic F127 and PEG-4000 into the casting solution. It was revealed that PSF/Pluronic F127 membranes are characterized by higher pressure resistance in ultrafiltration process, a lower total flux decrease during ultrafiltration of bovine serum albumin solutions. The antifouling performance of PSF/Pluronic F127 membranes was found to exceed significantly the antifouling performance of PSF/PEG-4000 membranes.

Developing an effective and mechanically durable biomimetic membrane for the separation of highly emulsified aqueous oil is significant but challenging owing to its low water flux and serious membrane fouling. In this work, a biomimetic membrane with superhydrophobicity and superoleophilicity was rationally developed via co-electrospinning of polysulfonamide/polyacrylonitrile (PSA/PAN) emulsion solution, followed by decorating of α-Fe2O3 nanowire onto the membrane surface to create membrane roughness, and grafting of 1H,1H,2H,2H-perfluorododecyltrichlorosilane (FTCS) to lower membrane surface free energy. Benefiting from the nanowire-wrapped rough membrane structure and the low surface free energy FTCS, the resultant membrane showed superhydrophobicity with a high water contact angle (WCA) of 156°, superoleophilicity with a low oil contact angle (OCA) of 0°, which can separate the highly emulsified aqueous oil with an ultrahigh permeation flux over 7000 L m−2 h-1 and high separation efficiency of about 99%. Significantly, the biomimetic membrane also displayed robust stability for long-term separation owing to its advantage of antifouling property, showing great potential applications in large-scale aqueous oil treatment.

Cerium fluoride (CeF(3)) nanoparticles (NPs) were synthesized and applied in polysulfone (PS) membrane fabricated by phase inversion method. The produced nanocomposite membranes (PS/CeF(3)) with different contents of CeF3 NPS (0.25%, 0.5%, 0.75% and 1% w/w) were used to treat pharmaceutical wastewaters. The membranes were characterized by FESEM, EDX, XRD, FTIR, porosity, and water contact angle analyses. Evaluation of the characteristics and performance of the nanocomposite membranes confirmed that utilizing photocatalytic CeF(3) NPs in membrane structure could effectively decompose organic contaminants in pharmaceutical wastewaters. It also improves the hydrophilicity and antifouling ability of membrane during filtration especially, in the presence of UV irradiation. The permeate flux of the PS membrane increased from 35.1 to 63.77 l/m(2)h by embedding 0.75% of CeF(3) NPs in membrane structure due to the porosity enhancement from 71.36–78.42% and the decrease in contact angle from 62.9º to 53.73º. Moreover, the flux decline of PS/CeF(3)-0.75% membrane under UV irradiation was from 63.6 to 46.1 l/m(2)h that considerably lower than that of the neat PS membrane (from 34.7 to 4.9). On the other hand, the degradation efficiency of PS/CeF(3)-0.75% membrane was more than 97%, and COD removed was more than 65% while they were 75% and 31%, respectively for the nascent PS membrane. Therefore, applying the appropriate amount of CeF(3) NPs in PS membranes not only greatly increased the permeate flux but also significantly enhanced the degradation efficiency and COD removal. This indicates that nanocomposite membranes can be confidently applied for pharmaceutical wastewater treatment UV irradiation. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s40201-020-00534-4) contains supplementary material, which is available to authorized users.

The water scarcity threatens environmental health and human development. Membrane distillation (MD) is one of the most applicable processes for purifying water using a hydrophobic membrane. In this study, the synergetic effect of SiO(2) nanoparticles as well as employing the dual coagulation bath on physical and mechanical properties of Polyvinylidene Fluoride (PVDF) flat-sheet membranes produced by dry-wet phase inversion (DIPS) technique has been investigated. The results of microstructural analysis using Scanning Electron Microscope (SEM) demonstrated that by adding nanoparticles while the pore size decreased noticeably, the percentage of porosity significantly increased. Also, it has been revealed that by utilizing isopropanol as the first coagulation bath the finger-like macro-voids became smaller in size, and the share of sponge-like structures rose remarkably. The membrane performance was tested by Vacuum Membrane Distillation (VMD) for measuring the flux and Liquid Entry Pressure (LEP(w)) laboratory setup. It can be seen that by increasing the content of SiO(2) nanoparticles to 6 wt.% while the LEP(w) approximately halved, the flux soared to about 10000 g/m(2)h. Moreover, mechanical testing showed that although the tensile strength of nanocomposite samples fabricated in isopropanol dual coagulation bath was improved by up to 66%, their ductility slightly declined. Furthermore, the hydrophobicity of each membrane was examined via contact angle measurements. Finally, it was found that all membranes completely rejected the NaCl in rejection test. [Figure: see text]

Partial substitution of the asymmetric 3,3',4,4'-biphenyl dianhydride monomer (aBPDA) into the backbone of a 6FDA-BPDA-DAM (6FDA=4,4'-hexafluoroisopropylidene, DAM=diaminomesitylene) diphthalic anhydride-based copolyimide based on symmetrical BPDA (sBPDA) was used to study membrane structure-processing-property relationships for gas separation. Properties of the polymer membrane as well as derived carbon molecular sieves (CMS) membranes were compared with copolyimides without the asymmetric monomer structure. CMS membranes derived from the copolyimides are very attractive for CO2 /CH4 separation. aBPDA provides the copolyimide with additional packing-inhibited structures compared with the symmetric ones and yields a corresponding CMS membrane with very high CO2 permeability and good CO2 /CH4 selectivity. This work, therefore, outlines a new strategy for tuning CMS membrane structure to meet separation performance needs.

Water management has been proven significant for enhancing both performance and durability of anion exchange membrane fuel cell. Besides searching new material, decreasing membrane thickness and modifying operation parameters, a simple and universal method of altering membrane structure is proposed in this work. Composite membranes made by unique processing method that includes both casting and electrospinning processes were compared with traditional casting membrane, all with the same thickness of 40 µm. Comparing to traditional casting membrane, the composite membrane put at proper position shows a higher water permeability, thus even more than 50% enhancement of the peak performance.

The polymer precursor plays a vital role in the membrane structure, as well as its permeance and rejection capability. In general, the polymer utilized in research is purified many times to obtain a higher purity, thus resulting in expensive and energy-consuming raw materials for membranes. Herein, we propose a facile method to prepare a nanofiltration hollow fiber membrane via reclaimed rubber recovered from waste tires as a precursor. The permeation tests reveal that the rubber-derived membrane with 12 wt% precursor concentration and three internal coating times exhibited the best performance for dye removal, with a methyl blue rejection rate of up to 93.1%. After three further filtration cycles, the permeate permeance obtained from the R1-12-L3 membrane could be maintained at 8.3 LMH/bar with a methyl blue rejection rate of 98.1%. These experimental results indicate that the rubber-derived hollow fiber membrane could be a feasible alternative for wastewater purification due to its low-cost, high-performing, and self-cleaning properties.

Currently, composite membranes play a significant role in the separation of acidic gases. Inorganic nanoparticles are used in these composite membranes to enhance the thermal and chemical properties of composites. In this study, polysulfone–polyethylene glycol/silica (PSF–PEG/silica) nanocomposite membranes were investigated for the purpose of improvement of the N2, O2, CH4 and CO2 separation properties. The results of gas permeability in nanocomposite membranes showed that the PSF/PEG 10,000 membrane, with 20 wt% of silica, provided the best gas separation properties. CO2 permeability in the nanocomposite membrane with 20 wt% of silica was 13.36 Barrer. In addition, the ideal selectivity for CO2/N2 paired gases in this membrane was 45.76, which was higher than the values obtained in the pure PSF membrane and the composite membrane with 20 wt% PEG 10,000. In addition, scanning electron microscopy, infrared spectroscopy, thermal gravimetric analysis, X-ray diffraction, differential scanning calorimetry and a tensile strength test were all used to examine the membrane structure and morphology of the nanocomposite. Finally, mechanical rheometry was used to study the rheological properties of hybrid nanosized composites and the effect of nanoparticle percentage on them.

Polyvinylidene fluoride-co-polytetrafluoroethylene, PVDF-co-PTFE polymer was used as a membrane support. The asymmetric membranes were formed by immersion of casted membrane film into the coagulation bath. This work manipulated the coagulant bath medium by mixing ethanol with distilled water at different weight percentages (0, 25 and 50 wt. % of ethanol). The structures of fabricated membranes were observed to have different morphologies. Higher ethanol content altered the membrane structure from finger-like to sponge-like structure, and hence differed in membrane porosity. Vacuum-based technique was chosen to impregnate the deep eutectic solvent (DES) into the pores of membrane support. DES was prepared by mixing choline chloride (ChCl) and ethylene glycol at a ratio of 1:3. Scanning electron microscopy (SEM) was used to study the membrane morphology changes while in order to determine the immobilization of DES, energy dispersive X-ray (EDX) analysis was used. The porosity of fabricated PVDF-co-PTFE membrane was determined by means of gravimetric method. Lastly, the membrane separation performance using CO2 and N2 gasses were used to determine the capability of the supported-DES-membrane. The results demonstrated the highest immobilization of DES in supported membrane pores was achieved when combination of 25 wt. % of ethanol and 75 wt. % distilled water was used as a coagulant bath medium. The respective membrane has 74.5% porosity with the most excellent performance of CO2 separation at 25.5 x 103 GPU with CO2/N2 selectivity of 2.89.

In this work, the polyvinyl chloride/alumina (PVC/Al2O3) ultrafiltration (UF) nanocomposite membranes were prepared with different amounts of Al2O3 within a range of 0–2 wt.%. Neat PVC and optimum nanocomposite membranes were evaluated in a submerged membrane system for the removal of humic acid (HA). The Fourier transform infrared (FTIR) spectroscopy confirmed the presence of hydroxyl group (OH) on the surface of the PVC nanocomposite membrane. Results revealed that the nanocomposite membrane with 1.5 wt.% of Al2O3 nanoparticles has the highest value in porosity and hydrophilicity when compared to other samples. The results obtained from the field emission scanning electron microscopy (FE-SEM) images showed that as Al2O3 was added to the membrane structure, more pores and larger pores were formed on the membrane surface. A higher critical flux was obtained by the PVC/Al2O3 (1.5 wt.%) nanocomposite membrane due to change in the surface characteristics. Antifouling analysis under subcritical conditions for neat PVC membrane showed that the main portion of the total fouling ratio was irreversible fouling ratio (IFR), while the nanocomposite membrane with 1.5 wt.% of Al2O3 nanoparticles significantly decreased IFR. Finally, the nanocomposite membrane had a higher HA rejection than the neat PVC membrane.