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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.

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.

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.

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.

The support flux was first investigated as a separate influencing factor for its effect on performances of ceramic filtration membranes. Three pre-membranes were prepared by tape-casting and then transfer-coated to supports to form dual-layer ceramic membranes after sintering. Experiments demonstrated that membrane layers with almost the same properties were obtained despite the huge difference in support flux. When the support flux increases from 3.120 to 97.53 m3m−2h−1, the flux of these three membrane series have increased by 75%, 186% and 228%, respectively. Experimental rules can provide structural design and evaluation from the perspective of permeability. The limit membrane flux of a certain system was derived according to the resistance distribution law of internal membrane structure and the Darcy's theorem. On this basis, a method for designing support flux was proposed. Furthermore, we present a criterion to quickly and easily evaluate the match between the support and the top layer, which is the ratio of membrane resistance to total resistance. Finally, the filtration resistance of penetration caused by suction of membrane particles into the support was measured for the first time, taking the advantage of the transfer-coating method that inherently free of penetration. Our works are expected to deepen the understanding of the ceramic membrane structure and provided guidance for its rational design and optimization.

A simple and effective damage constitutive model for PVC-coated fabrics be developed, which could be used to predict the nonlinear mechanical response of membrane structures under tension more accurately. In this paper, based on continuum damage mechanics theory, a nonlinear damage constitutive model for PVC-coated fabrics was established. Firstly, the off-axis tensile tests were carried out on the membrane material at 0 °, 15 °, 30 °, 45 °, 60 °, 75 °, and 90 ° with an electronic universal tensile testing machine, and the tensile curves of seven specimens were obtained. Then, the Helmholtz free energy function is constructed based on the continuum damage mechanics theory and the existing research foundation, and the constitutive equation of the material is derived. Then, according to the characteristics of the off-axial tensile test curve of the coated fabrics, a damage evolution equation for the materials under tension was established with strain as an independent variable. By compiling a MATLAB program of the constitutive model, the parameters were obtained, and the off-axial tensile test curves of PVC-coated fabrics were predicted. The constitutive model was compiled using the user-defined subroutine UMAT in ABAQUS, and the correctness of the model was verified by simulating a static loading test of the membrane structure under in-plane tension. The model shows a good performance in computation and the obtained results are also in good agreement with experimental data. These features enable the proposed model to be used in numerical calculations for membrane structures.

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.

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.

In recent years, the construction of enclosed material yard projects has becoming an urgent requirement to improve ecological environment and living environment quality. Thin membrane structures have been widely used in industrial building, especially for storage building roofs. Due to the thermal-optical properties of translucent thin fabric material, such as the absorption and transmittance of solar radiation, the indoor thermal environment is seriously disturbed. Moreover, membrane building structures are usually irregular. Compared with conventional buildings material, the translucent thin fabric material particularly responsive to changes in external environment conditions. As a result, the solar radiation heat gain calculation of membrane buildings is complicated. It is worth exploring measures to tackle this problem. Therefore, in order to solve the problem that the relevant thermal-optical parameter is difficult to obtain. The 13 thin membrane samples were tested and the thermal optical characteristic parameters were analyzed in this paper. A practical enclosed membrane structure building was selected as the research object. In addition, a solar radiation heat transfer model was established. The indoor solar heat gain under the action of solar radiation heat was calculated and the effect of different light transmittance and absorptance on the indoor radiation heat gain was studied. It can provide reference for heat gain calculation and ventilation design of membrane structure storage buildings.

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.

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°.

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.

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.

Diffusion obstacles in membranes have not been directly visualized because of fast membrane dynamics and the occurrence of subresolution molecular complexes. To understand the obstacle characteristics, mobility-based methods are often used as an indirect way of assessing the membrane structure. Molecular movement in biological plasma membranes is often characterized by anomalous diffusion, but the exact underlying mechanisms are still elusive. Imaging total internal reflection fluorescence correlation spectroscopy (ITIR-FCS) is a well-established mobility-based method that provides spatially resolved diffusion coefficient maps and is combined with FCS diffusion law analysis to examine subresolution membrane organization. In recent years, although FCS diffusion law analysis has been instrumental in providing new insights into the membrane structure below the optical diffraction limit, there are certain exceptions and anomalies that require further clarification. To this end, we correlate the membrane structural features imaged by atomic force microscopy (AFM) with the dynamics measured using ITIR-FCS. We perform ITIR-FCS measurements on supported lipid bilayers (SLBs) of various lipid compositions to characterize the anomalous diffusion of lipid molecules in distinct obstacle configurations, along with the high-resolution imaging of the membrane structures with AFM. Furthermore, we validate our experimental results by performing simulations on image grids with experimentally determined obstacle configurations. This study demonstrates that FCS diffusion law analysis is a powerful tool to determine membrane heterogeneities implied from dynamics measurements. Our results corroborate the commonly accepted interpretations of imaging FCS diffusion law analysis, and we show that exceptions happen when domains reach the percolation threshold in a biphasic membrane and a network of domains behaves rather like a meshwork, resulting in hop diffusion.

One great advantage of graphene-polyelectrolyte multilayer (GPM) membranes is their tunable structure and internal charge for improved separation performance. In this study, we synthesized GO-dominant GPM membrane with internal negatively-charged domains, polyethyleneimine (PEI)-dominant GPM membrane with internal positively-charged domains and charge-balanced dense/loose GPM membranes by simply adjusting the ionic strength and pH of the GO and PEI solutions used in layer-by-layer membrane synthesis. A combined system of quartz crystal microbalance with dissipation (QCM-D) and ellipsometry was used to analyze the mass deposition, film thickness, and layer density of the GPM membranes. The performance of the GPM membranes were compared in terms of both permeability and selectivity to determine the optimal membrane structure and synthesis strategy. One effective strategy to improve the GPM membrane permeability-selectivity tradeoff is to assemble charge-balanced dense membranes under weak electrostatic interactions. This balanced membrane exhibits the highest MgCl2 selectivity (∼86%). Another effective strategy for improved cation removal is to create PEI-dominant membranes that provide internal positively-charged barrier to enhance cation selectivity without sacrificing water permeability. These findings shine lights on the development of a systematic approach to push the boundary of permeability-selectivity tradeoff for GPM membranes.

Porous polyvinylidene fluoride (PVDF)-filled MWCNT hollow fiber mixed matrix membranes were fabricated and applied for carbon dioxide absorption in a gas–liquid membrane contactor with Al2O3 water-based nanofluid absorbent. The formation of MWCNTs’ nanotubes was verified through Transmission electron microscopy (TEM) and Field emission scanning electron microscopy (FESEM) images while the resultant membranes were characterized for their morphology, gas permeation rate, pore size, porosity, surface hydrophilicity and wettability resistance. Upon the incorporation of MWCNT into the matrix, the formation of finger-like pores was facilitated and surface roughness increased. Gas permeation test results showed increasing the surface porosity and reducing the pore size. The surface contact angle also was improved from 83° ± 1.5 for the unfilled membrane to 103° ± 1.5 for the membrane containing 5 wt% CNT. CO2 absorption flux also was enhanced considerably. For instance, the flux of the membrane containing 5 wt% CNT as the best performing membrane at a liquid velocity of 2.5 m/s and Al2O3 water-based nanofluid as absorbent was 3.85 × 10−3 mol/m2 s which was approximately 200% higher than that of the plain membrane at the same operating conditions. A long-term absorption test also revealed non-wetting tendencies of the membranes as well as the unclogged membrane pores by the nanomaterials existed in the nanofluid absorbent. Therefore, it could be hypothesized that the improved membrane structure and synthesized nanofluid absorbent considering their superior performance to several commercial and in-house made membranes can be suitable alternatives to the current polymeric membranes and commercial used absorbents, respectively.

The synergistic effect of nanoboehmite particles and various amounts of poly(ethylene glycol) (PEG 4000, 0−4 wt.%) as a pore-former agent on the characteristics, permeability and fouling resistance ability of the nanoboehmite/EPVC blended membranes has been investigated. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and water contact angle analyses were utilized to examine the morphology, surface roughness, nanoboehmite dispersion and surface hydrophilicity, respectively. By increasing the PEG content in the EPVC dope solution, hydrophilicity, porosity and pores diameter improved, leading to the performance promotion of the membranes. The pure water flux (PWF), flux recovery ratio (FRR) and bovine serum albumin (BSA) flux of the nanoboehmite/EPVC composite membrane improved by enhancing the PEG loading up to 2 wt.% and then they dropped at higher content of it. Anti-fouling ability of the mixed-matrix nanoboehmite/EPVC composite membrane including 2 wt.% of PEG had a dramatic growth (68.3%) relative to the pristine EPVC membrane. Moreover, all the membranes were able to reject BSA proteins more than 98%. The obtained results displayed that the influence of PEG concentration enhancement on the characteristics and efficiency of the EPVC and EPVC/nano-composite membrane was different. The addition of various amounts of PEG to the nano-composite membranes matrix has not unfavorably influenced the amount of BSA rejection and membrane structure.

Phenolphthalein-based cardo poly(ether ether ketone) (PEEKWC)/polyethyleneimine (PEI) crosslinking membranes were prepared by solution casting followed by solution reaction at room temperature. The effects of reaction time and PEI content on the membrane structure and gas separation performances were investigated. Light transmittance measure and AFM evidenced the relationship between the microphase separation in PEEKWC-PEI membranes and reaction time. The CO2 permeability increased with the PEI content, while the N2 and CH4 permeability remained nearly constant. This result indicated that only CO2 was transported by the solution–diffusion mechanism and also that PEI exhibited a positive contribution as a fixed carrier for CO2 facilitated transport. Meanwhile the PEEKWC-PEI crosslinking membranes showed higher selectivities than the pure PEEKWC membrane. The highest CO2/N2 and CO2/CH4 selectivities were about 131 and 122 increasing from 33 and 30, respectively. The crosslinking structure of membranes improved the CO2 permeability stability.

Transmembrane proteins function within a continuous layer of biologically relevant lipid molecules that stabilizes their structures and modulates their activities. Structures and interactions of biological membrane-protein complexes or "memteins" can now be elucidated using native nanodiscs made by poly(styrene co-maleic anhydride) derivatives. These linear polymers contain a series of hydrophobic and polar subunits that gently fragment membranes into water-soluble discs with diameters of 5-50 nm known as styrene maleic acid lipid particles (SMALPs). High-resolution structures of memteins that include endogenous lipid ligands and posttranslational modifications can be resolved without resorting to synthetic detergents or artificial lipids. The resulting ex situ structures better recapitulate the in vivo situation and can be visualized by methods including cryo-electron microscopy (cryoEM), electron paramagnetic resonance (EPR), mass spectrometry (MS), nuclear magnetic resonance (NMR) spectroscopy, small angle x-ray scattering (SAXS), and x-ray diffraction (XRD). Recent progress including 3D structures of biological bilayers illustrates how polymers and native nanodiscs expose previously inaccessible membrane assemblies at atomic resolution and suggest ways in which the SMALP system could be exploited for drug discovery.

This paper reports a fast, cost-effective and environmental-friendly method to engineer the membrane structure, and simultaneously enhance the permeance and fouling resistance in reverse osmosis (RO). By free radical polymerization in water, copolymers containing fouling-resistant zwitterionic and hydroxyl-based anchoring groups are synthesized and quickly bonded to the polyamide membrane surface. The copolymer also functions as the molecular engine to reduce the thickness of the polyamide layer and drill nanopores, thereby re-shaping its 3D structure for higher permeability. It is revealed that by design of the size and functionality of the copolymer, the water permeability and salt rejection may be simultaneously increased. Our membrane demonstrates a pure water permeability of 10.5 L m−2 h−1 bar−1, NaCl rejection of 98.1%, and superior fouling resistance towards various foulants and realistic feed. This paper provides a new perspective for the development of highly permeable, fouling-resistance membranes not only for RO, but also nanofiltration.

Thin-film polyamide composite membrane (TFC) is a good representative model of highly permeable membrane. SEM analysis showed that TFC membrane structure is swelled by hexane vapors. Contrary, its porous structure collapsed when the used membrane is stored at dry conditions. The aging of membrane causes significant decrease of both hexane vapors and nitrogen permeances while the selectivity increases tenfold. The study is based on time influence and on wetting by various solvents. Methanol treatment opens and swells the pores of aged membrane. Furthermore, the transport and separation properties were studied after gradual wetting by mutually miscible solvents with decreasing polarity (methanol, isopropanol and hexane) that are commonly used for membrane drying. Surprisingly, this solvent exchange drying procedure leads to a regeneration of the TFC membrane. The regenerated membrane shows the same transport and separation properties as the pristine TFC membrane.

In this study, the capability of a mixed matrix composite membrane (MMCM) fabricated using polyether block amide polymer PEBAX MH1657 from Arkema and in lab synthesized aminated partially reduced graphene oxide (A-prGO) nanofiller as a selective layer has been studied for gas separation. Moreover, the effects of nanofiller addition on membrane structure properties and performance were examined. The PEBAX/A-prGO membrane was fabricated as a selective layer on top of a supporting substrate layer of polysulfone 1700. MMCM was prepared in five different loadings of A-prGO nanofiller (0, 0.05, 0.1, 0.2, 0.6 (w/w)%) of the used PEBAX amount. The synthesized nanofiller and fabricated MMCM were characterized using different characterization tests (XRD, FTIR, EDX, and SEM). The optimum separation of the membrane was found when the loading of A-prGO was 0.1%. The permeability of the membrane for CO2, N2 and CH4 gases were 47.5 Barrer for CO2, 0.45 Barrer for N2 & 2 Barrer for CH4 while the selectivity of CO2/N2 and CO2/CH4 are 105.6 and 23.75, respectively. Surprisingly, the fabricated membrane performance found to be above the Robeson 2008 upper bound of permeability- selectivity relation for CO2/N2 gases separation.

Cake formation is the most important phenomenon to reduce cross-membrane flux in cross-flow microfiltration although pore blocking and concentration polarization (CP) phenomena affect it. Electric field may be used to enhance process efficiency and decreased fouling phenomena in the process. An empirical model is developed here taking into consideration the cake formation effects on permeate flux reduction in the presence of AC electric field. A semi-empirical model is also developed in the presence and absence of electric field at two cases; with and without considering membrane structure in the modeling. It is the first time that electric field effects on microfiltration performance are modeled macroscopically and used with pore blocking phenomenon simultaneously. The predicted permeate fluxes by the models are compared against experimental permeate fluxes in absence and presence of electric field. Comparison of the model based predictions against experimental results indicate semi-empirical model precision with a maximum error of 8.9% for the case without and 3.6% for the case with pore blocking consideration and a maximum error for empirical model of 11.9%. Effects of different electric potentials and distances between the electrodes on CP layer thickness and oil concentration on membrane surface are also studied. The predicted results showed that the CP layer thickness is decreased by 60.9% through applying an electric potential of 500 V and also decreased by 65.2% through decreasing the distance between the electrodes from 2.3 to 1.3 mm at 200 V. The oil concentration on the membrane surface is also decreased by 72.3% as a result of applying the electric field while it is decreased by 19.2% when the electrodes distance is decreased from 2.3 to 1.3 mm at 200 V.

In this study, a quantitative performance of three commercial polyamide nanofiltration (NF) membranes (i.e., NF, NF90, and NF270) for phosphorus removal under different feed conditions was investigated. The experiments were conducted at different feed phosphorus concentrations (2.5, 5, 10, and 15 mg·L−1) and elevated pHs (pH 1.5, 5, 10, and 13.5) at a constant feed pressure of 1 MPa using a dead-end filtration cell. Membrane rejection against total phosphorus generally increased with increasing phosphorus concentration regardless of membrane type. In contrast, the permeate flux for all the membranes only decreased slightly with increasing phosphorus concentration. The results also showed that the phosphorus rejections improved while water flux remained almost unchanged with increasing feed solution pH. When the three membranes were exposed to strong pHs (pH 1.5 and 13.5) for a longer duration (up to 6 weeks), it was found that the rejection capability and water flux of the membranes remained very similar throughout the duration, except for NF membrane with marginal decrement in phosphorus rejection. Adsorption study also revealed that more phosphorus was adsorbed onto the membrane structure at alkaline conditions (pH 10 and 13.5) compared to the same membranes tested at lower pHs (pH 1.5 and 5). In conclusion, NF270 membrane outperformed NF and NF90 membranes owing to its desirable performance of water flux and phosphorus rejection particularly under strong alkali solution. The NF270 membrane achieved 14.0 L·m−2·h−1 and 96.5% rejection against 10 mg·L−1 phosphorus solution with a pH value of 13.5 at the applied pressure of 1 MPa.

A novel composite membrane with a built-in self-cleaning capability was fabricated, characterized and tested. The membrane consists of a piezoelectric lead-zirconate-titanate (PZT) separation layer and a macroporous Ti support. The Ti support provides mechanical strength to the membrane and is also used as one of the electrodes needed to operate the membrane in self-cleaning mode. The PZT layer serves as a size selective membrane and as the component that generates ultrasound (US) by application of an alternating voltage (AV). The membrane structure was made by dry pressing of PZT particles on the porous Ti, and heat-treated at 650 °C to achieve sufficient mechanical integrity. A low treatment temperature was chosen to avoid adverse effects of Ti support oxidation, differential shrinkage and thermal expansion mismatch between the support and the PZT layer. Characterizations were performed with X-ray photoelectron spectroscopy, thermogravimetry, scanning electron microscopy, and mechanical strength measurements. These led us to conclude that the PZT reacted with a thin film of TiO2, formed on the Ti surface, resulting in excellent interfacial strength. The membranes' performance was assessed from cross-flow water purification of oil in water (O/W) emulsions. For membrane structures with a poled PZT layer, operated with an AV of 60 V, the permeance became stationary at 92% of the initial value. For other membranes without US generation that number was ∼64%. The higher stationary permeance is ascribed to the fact that oil droplet accumulation on the membrane is avoided due to the action of in-situ generated US. The combination of Ti support and PZT membrane layer appeared particularly suitable because of minimal thermal expansion mismatches, excellent operational stability, and simplicity of the design.

An excellent positively charged nanofiltration (NF) membrane is of great significance for water softening. In this work, a novel positively charged composite PEI/TMA NF membrane was prepared by gradient cross-linking polyethyleneimine (PEI) with trimesic acid (TMA) on polyethersulfone ultrafiltration (PESU) membrane. The effects of concentration of PEI and TMA, the cross-linking reaction temperature and reaction time on membrane structure and performance were investigated in detail. The effects of PEI and TMA, reaction temperature and time on the membrane structure, composition and performance were investigated. The optimized preparation conditions of PEI/TMA NF membrane were fixed at 0.6% (m/v) PEI, 0.1% (m/v) TMA, 0.15% (m/v) SDS at 90 °C for 10 min. The as-prepared membrane exhibited a pure water flux of 19.1 L m−2 h−1 bar−1 and a rejection of MgCl2 93.0%, NaCl 38.2%, MgSO4 20.4%, and Na2SO4 8.8%. The functional layer is ultra-thin. Its high selectivity mainly results from Donnan effect. The long-term testing of our PEI/TMA NF membrane show a high stability. Compared with other positively charged membranes, the PEI/TMA NF membrane had unique advantages in the production process and a comprehensive performance.

Ceramic membranes with asymmetric structures play an important role in treating wastewater in the chemical engineering industry. However, the asymmetric structure requires repetitive “coating-drying-sintering” processes to achieve a ceramic membrane with satisfactory separation accuracy, which in turn requires a long fabrication period and has limited the widespread application of such membranes. Herein, a single-step coating preparation for a high-performance asymmetric ceramic membrane using macroporous fly ash supports has been developed using a thermal spraying technique. The novel coating process can not only prevent the penetration phenomenon and avoid the need for intermediate layers, but also significantly lower the fabrication time and cost of the ceramic membranes. Based on theoretical calculations using the Hagen-Poiseuille (H-P) and Darcy equations, the resistance of the supports and fabricated membrane layer accounted for 8.5% and 91.5% of the total resistance, respectively. The resistance distribution indicates a reasonable membrane structure, with the resistance being mainly concentrated on the membrane. This indicates that the supports only provide high bending strength and do not have an adverse effect on the permeability performance. The fly ash/alumina composite membranes (FACMs) fabricated under the optimized conditions had pore diameters of approximately 100 nm and a permeability of approximately 445 L m−2 h−1 bar−1 (at 0.1 MPa). In the treatment of oily emulsions and spent tin wastewater, the FACMs showed good total organic carbon (TOC) retention (above 99%) and a high rejection for stannic acid (above 99.9%) in industrial spent tin wastewater from the printed circuit board industry. The technique of combining low-cost fly ash supports and the optimized membrane structure could significantly decrease the membrane cost and serve as an efficient method for wastewater treatment.

Various experimental data reveal intriguing peculiarities in structural properties of biomimetic membranes. Interestingly, one of the common alterations that is observed at the membrane-water interface underlines the important role of membrane hydration properties. A plausible mechanism of action in the case of many membrane additives seems to be in shifting the water encroachment the way that bilayers absorb more or less water molecules - one of the smallest and often neglected biomolecule. The difference in water interactions with different lipids and cholesterol has been noted at the interface and up to the bilayer center, the ion depending interplay between lipid-water and ion-water hydrations has been shown, and the anaesthetic effect also appears to link tightly to hydration, to discuss but a few examples. Although a complete understanding of the physicochemical processes taking place in biomembranes is not established fully, the understanding of lipid bilayer structural changes as a result of different properties of environment outside and/or inside the membrane provides a foundation for better insights into the structure-function relationships that most certainly take place in complex biomembrane systems.

While a number of graphene oxide (GO) materials have been evaluated as nanofillers in ultrafiltration membranes, there remain outstanding questions regarding GO material properties relating to membrane structure(s) and eventual performance (i.e. structure-performance relationships). In this work, we synthesize, apply, and evaluate GO analog materials of different shape, flat GO and crumpled GO (CGO), as nanoscale fillers in polysulfone (PSF) ultrafiltration membranes. GO/CGO-PSF composite membranes were synthesized via phase inversion, characterized using both microscopic and spectroscopic techniques, and compared with respect to permeability, rejection, and anti-fouling properties. Experimental results show that graphene shape alone results in varied performance. Observed differences are attributed to the (more) effective dispersion/stability of CGO nanoparticles in solvent (NMP) as a result of shape effects, which lowers the tipping mass percentage after which the effect of viscosity increase outweighs that of hydrophilicity increase. Our results also suggest that the change(s) in membrane porosity is likely to be a more important factor compared to surface hydrophilicity in determining ultrafiltration membrane performance when graphene oxides are applied with these mass percentages. In addition to the effect of GO shape, this study also highlights the importance of nanoparticle dispersibility/stability in organic solvents when constructing the process-structure-performance relationships for nano-enabled ultrafiltration membranes synthesized via phase inversion.

In this work, high performance cross-linked anion exchange membranes with hydrophobic side-chains were prepared via quaternization reaction and a simple heat treatment. The cross-linked membrane structure, the hydrophobic side-chain and the micro-phase separated morphology of membranes have synergistic effect on ion selective separation. Accordingly, the obtained membranes possess excellent ion perm-selectivity and considerable OH− flux. Especially, QPPO-C6-120 membrane exhibits the superior perm-selectivity of 76 for OH−/ W O 4 2 − system and high OH− flux of 2.72 × 10−7 mol cm−2 s−1 at a current density of 30 mA cm−2. XPS and 1H NMR confirmed the introduction of long side-chain and the thermo-crosslinking reaction. Meanwhile, the microstructure of membranes was investigated by XRD and SAXS. More importantly, a new perspective of mesoscales by combining the molecule structure with the microstructure of membranes is innovatively used to explore the ion separation mechanism.

Niobate nanosheet membranes were fabricated by vacuum filtration using niobate nanosheets prepared by the hydrothermal method (HT-NbO membranes) and the exfoliation method (EX-NbO membranes). Membrane structure, water permeance and separation performance for these membrane types were measured and compared. Both membrane types had a dense structure and retained high structural stability in water via chemical cross-linking between sheets. The difference of the intercalated molecules and interaction between nanosheets affected the interlayer distance of the membranes. As a result, higher water permeance but lower rejection of polyethylene glycol, Na2SO4 and Acid Red 265 was observed for EX-NbO membranes than for HT-NbO membranes. This is due to the formation of larger nanochannels in EX-NbO membranes. A model of a water pathway through nanochannels based on void structure proposed for the HT-NbO membranes can also be applied for EX-NbO membranes.

Environmental protection and climate change are current issues at the heart of global economic growth. The awareness of the real risks connected with industrial membrane production sector has been the push towards the search of new, more sustainable, sol vents and raw materials . In this context, dihydrolevoglucosenone (Cyrene(TM)) comes as a green biosolvent derived from waste cellulose, with enormous potentiality, which could offer the possibility to re-design manufacturing processes from the origin. The increasing interest devoted to Cyrene(TM) has its basis in the similarity with many physi cal-chemical properties of highly toxic organic solvents normally used for fabrication membranes (such as N-Methyl-2-pyrrolidone, N,N-Dimethylformamide and N,N-dimethy l acetamide). In fact, Cyrene(TM) is presented as a polar aprotic organic solvent, comple tely miscible with water, and with a relatively high boiling point (227 °C). Herein, Cyrene(TM) was employed for the preparation of polyethersulfone (PES) and pol y(vinylidene fluoride) (PVDF) membranes via phase inversion [2]. By preparing PES/C yrene(TM) and PVDF/Cyrene(TM) casting solutions, without the use of any additive, and b y working at room temperature, microfiltration and ultrafiltration membranes were obta ined. Non-solvent induced phase separation (NIPS) and its combination with vapour-in duced phase separation (VIPS) were adopted as preparation procedure. PES and PVDF membranes were characterized in terms of thickness, porosity, pore size, contact angl e and pure water permeability. The morphology was also assessed. For PVDF membra nes, additional differential scanning calorimetry and Fourier transform infrared spectros copy analysis were performed. The obtained results evidenced as, by varying the exposure time to controlled humid a ir and temperature during the VIPS-NIPS process, membranes with different morpholo gy and properties can be prepared, demonstrating the applicability of Cyrene(TM) for a more sustainable membrane fabrication.

Novel porous and dense membranes based on polysulfone (PSF) modified by poly(ethylene glycol)–b–poly(propylene glycol)–b– poly(ethylene glycol) (Pluronic F127) were developed. The influence of Pluronic F127 introduction to the casting solution on different types of polymer membrane formation via two different phase inversion techniques—non-solvent induced phase separation (NIPS) for porous membranes and evaporation induced phase separation (EIPS) for dense membranes—was investigated. According to the triangular phase diagram obtained, PSF-Pluronic F127-N,N-dimethylacetamide (DMAc) systems feature lower critical solution temperature and have a tendency to micelle formation due to Pluronic F127 self-assembly. The structure, hydrophilic-hydrophobic balance and physicochemical properties of PSF-Pluronic F127 membranes were characterized by water contact angle measurements, scanning electron microscopy, nuclear magnetic resonance, small-angle X-ray scattering, and atomic force microscopy. The performance of dense membranes in pervaporation separation of water-ethyl acetate mixtures was investigated to reveal the effect of Pluronic F127 on the structure and free volume of the PSF-Pluronic F127 membranes. It was shown that Pluronic F127 introduction to the casting solution during membrane formation via two different techniques (NIPS and EIPS) leads to the increase in the pore size of the porous membranes and free volume of the dense membranes, as well as the increase in flux and surface hydrophilicity for both membrane types. Pluronic F127 was found to improve the antifouling performance of porous PSF-Pluronic F127 membranes in the BSA solution ultrafiltration. The introduction of 3 wt% Pluronic F127 into dense PSF membrane improved permeation flux in 1.7 and 2.7 times (15.1 and 27.3 g/(m2h)) at high selectivity level (100 wt% water in the permeate) during the separation of ethyl acetate-water mixtures (2 and 4 wt% ethyl acetate) compared to pristine PSF membrane.

Tough polymers are recognized as ideal membrane materials for gas and liquid separations in harsh environments. However, while solvent flux and solute rejection data, as well as permeability and selectivity data for light gases are widely available in the literature, fundamental studies of organic species transport in tough polymers and their correlation with the membrane structure are rare. This study focuses on the solubility of pure and mixed organic species in Celazole®, a commercial polybenzimidazole. Methanol was selected as a model penetrant to run sorption and diffusion experiments in the activity range 0–1. The role of polymer-penetrant interactions, membrane degree of swelling, and penetrant clustering on small molecule sorption and transport in Celazole® was discussed and several structure-property correlations were identified. Remarkably, polar penetrants, such as methanol, cause severe matrix plasticization. In contrast, Celazole® is highly stable in non-polar aliphatic and aromatic hydrocarbons. Finally, the polymer mechanical properties were measured before and after soaking in liquid water and methanol.

The surface of an α-Al2O3 carrier for semi-permeable zeolite membranes was modified with copper via an electroless plating process. Following hydrothermal synthesis, dense and highly organized zeolite membranes were obtained. Membrane thickness was confined to the nanoscale following layer-by-layer self-assembly of polyelectrolytes with opposite charges. This controllable and low-cost preparation method could drastically reduce the cost of fabricating reverse osmosis membranes, which is highly significant for the realization of large-scale seawater desalination through reverse osmosis. Understanding the influences of interactions between various ions and the zeolite pores, inter-crystalline gaps, membrane structure and surface chemical properties, transmembrane pressure, and temperature on the desalination process will help provide a theoretical basis and reference point for the development of reverse osmosis membranes.

To fabricate hydrophilic and anti-fouling PVDF ultrafiltration membrane, a kind of tailor-made symmetrical amphiphilic triblock copolymer, polyacryloylmorpholine-b-poly (methyl methacrylate)-b-polyacryloylmorpholine (PACMO-b-PMMA-b-PACMO, termed as PAMA), was prepared via RAFT polymerization and employed as an in situ surface segregation modifier. FTIR, 1H NMR, and GPC were used to verify the well-defined chemical structure of PAMA. The hydrophilic PACMO segments of PAMA were enriched on the surface of membrane skin and interior pores as confirmed by ATR-FTIR, XPS, EDX, and water contact angle tests, endowing the blend membranes with outstanding hydrophilicity. The different cross-sectional and surface morphologies of the PVDF/PAMA blend membranes indicated that the introduction of PAMA modifiers could manipulate membrane structure due to their strong pore-forming ability. Compared with the pure PVDF membrane, PVDF/PAMA blend membranes showed higher permeability for water (28.1 times higher), excellent rejection for bovine serum albumin (up to 98.3%), and enhanced fouling resistance with a higher flux recovery ratio (up to 98.1%). Therefore, the approach of in situ surface segregation employed the RAFT mediated well-defined amphiphilic PAMA triblock copolymer modifiers for the preparation of anti-fouling PVDF membranes showed a great potential in water purification.

For osmotic power generation using the pressure retarded osmosis (PRO) process, mechanically robust membranes with high osmotic water flux are needed to obtain high power density from a given osmotic pressure difference. Particularly in the case of support-free hollow fiber membranes (HFMs), the pressure tolerance is a critical factor in maximizing power density when operating at high applied pressure with concentrated brine. Here, mechanically robust integrally-skinned asymmetric (ISA) HFMs were developed by combining the nonsolvent induced phase separation (NIPS) with the quenching, into a facile approach called the thermally assisted NIPS (T-NIPS) method, to tailor the membrane structure for PRO applications. The prepared T-NIPS membranes exhibited two distinct layers: a dense ISA outer layer and an isoporous inner layer. Compared to conventional NIPS HFMs, the T-NIPS HFMs showed much higher power density and collapse pressure, up to 5.5 W/m2 and 18 bar, respectively. The effect of pore forming agents on the membrane structure during the T-NIPS process, and on PRO performance, were studied. In addition, the power density and the pressure tolerance were further enhanced by optimizing the membrane dimensions and structure of the T-NIPS HFMs.

Biological cells are enveloped by a heterogeneous lipid bilayer that prevents the uncontrolled exchange of substances between the cell interior and its environment. In particular, membranes act as a continuous barrier for salt and macromolecules to ensure proper physiological functions within the cell. However, it has been shown that membrane permeability strongly depends on temperature and, for phospholipid bilayers, displays a maximum at the transition between the gel and fluid phase. Here, extensive molecular dynamics simulations of dipalmitoylphosphatidylcholine bilayers were employed to characterize the membrane structure and dynamics close to phase transition, as well as its stability with respect to an external electric field. Atomistic simulations revealed the dynamic appearance and disappearance of spatially related nanometer-sized thick ordered and thin interdigitating domains in a fluid-like bilayer close to the phase transition temperature (Tm). These structures likely represent metastable precursors of the ripple phase that vanished at increased temperatures. Similarly, a two-phase bilayer with coexisting gel and fluid domains featured a thickness minimum at the interface because of splaying and interdigitating lipids. For all systems, application of an external electric field revealed a reduced bilayer stability with respect to pore formation for temperatures close to Tm. Pore formation occurred exclusively in thin interdigitating membrane nanodomains. These findings provide a link between the increased membrane permeability and the structural heterogeneity close to phase transition.

Pore surface modification of zeolite membrane is a challenging area to combat the trade-off between the high flux and high selectivity of the gas separation membrane. Herein we report facile method of pore along with defects modification of NaX zeolite membrane by incorporating graphite amine (Ga) into the membrane structure. Permeation properties of different membranes were evaluated by single gas permeance of H2, CO2 and separation factors for mixed gas H2-CO2 with different mixture ratio. These studies were done at room temperature and 100–300 kPa feed pressure. The results show that Ga is not only active for defect removal of NaX membrane but also enhanced the formation of NaX zeolite from mother sol. In addition, presence of graphite amine into NaX zeolite membrane increase the permeance of H2 from 5.1 × 10−7 mol m−2 s−1 kPa−1 to 36.5 × 10−7 moll m−2 s−1 kPa−1 with increase of feed pressure 100–300 kPa feed pressure due to its hydrophobic properties and separation factor of H2-CO2 enhanced up to 31 for H2-CO2 mixture gas compared to literature reported value 6.5 for FAU membrane over 3-aminopropyltriethoxysilane functionalized alumina. Herein for the first time we report that graphite amine catalyzes for the formation of NaX zeolite in addition to pore modification in zeolite membrane.

Low conductivity and stability of anion exchange membranes limited the durability and performance of corresponding fuel cells despite their unique advantages in compared to the proton exchange membrane fuel cells. In this work, we present a simple and efficient method to fabricate highly durable anion exchange membranes from commercial porous hydrocarbon substrates. Polyethylene/polypropylene (PE/PP) microfibers is employed as a substrate and radiation induced emulsion grafting is utilized to introduce poly(vinylbenzyl chloride) side chains. The grafted substrates with flexible content of side chains are converted to anion exchange membranes by converting into dense membranes and introducing quaternary amine groups. The dense membranes are characterized and employed in vanadium redox flow battery (VRFB) application. Developed membranes demonstrate high anion conductivity, low vanadium permeability and good chemical and mechanical stability. In compare to Nafion 117, superior performance is achieved for the developed membranes as the undesired vanadium ion permeability is reduced by 16 times and the energy efficiency significantly enhanced by 9% at current density of 80 mA cm−2. Such enhanced performance of the developed membrane is attributed to the presence of positive charged ionic groups in the membrane structure.

Exploring a desirable cross-linker applied in cation exchange membranes (CEMs) to improve dimensional stability as well as electrochemical performance has a great signifcance for the current membrane science and technology. In this investigation, a sequence of crosslinked sulphonated polysulfone (SPSF) CEMs has been prepared to explore the influence of the crosslinking functionality on the dimensional stability and electrodialysis (ED) performance of modified membranes. Different cross-linker structures were obtained according to the cross-linker agent content added during the synthesis route. As expected, the membrane surface became smoother with increasing cross-linker content, presumably as result of the denser structure established. The dimension stability increases according to the crosslinking degree applied, whereas the permselectivity of membranes depends on the conjunction of many important and interlinked factors, including the formation of narrow ion transport channels and the variations in the exchanges sites concentration. It was observed that the optimized CEM (60SPSF-C2#) showed the highest NaCl removal ratio (91.7%) during the desalination experiments and exhibited the higher current efficiency (95.7%) and lowest energy consumption (6.55 kWh kg−1). These results suggest the formation of the optimum three-dimensional network configuration for the membrane structure determined by the functionality of cross-liker selected in this investigation.

The interaction between proteins and membranes is of great interest in biomedical and biotechnological research for its implication in many functional and dysfunctional processes. We present an experimental study on the interaction between model membranes and alpha-lactalbumin (alpha-La). alpha-La is widely studied for both its biological function and its anti-tumoral properties. We use advanced fluorescence microscopy and spectroscopy techniques to characterize alpha-La-membrane mechanisms of interaction and alpha-La-induced modifications of membranes when insertion of partially disordered regions of protein chains in the lipid bilayer is favored. Moreover, using fluorescence lifetime imaging, we are able to distinguish between protein adsorption and insertion in the membranes. Our results indicate that, upon addition of alpha-La to giant vesicles samples, protein is inserted into the lipid bilayer with rates that are concentration-dependent. The formation of heterogeneous hybrid protein-lipid co-aggregates, paralleled with protein conformational and structural changes, alters the membrane structure and morphology, leading to an increase in membrane fluidity.

In this paper, polypeptide membranes composed by surfactant-like peptides were studied by using molecular dynamics simulations. The studied membranes are composed by 15 amino acids, being a hydrophobic part consisting of 3 isoleucine (ILE - I), 3 valine (VAL - V), 3 alanine (ALA - A), 3 glycine (GLY - G), and a hydrophilic one formed by 3 lysine (LYS - K). These amino acids were linked into two different primary sequences, I3V3A3G3K3, with the charged lysine bounded at the C-terminus and K3G3A3V3I3, with the charged lysine bounded at the N-terminus. The density profiles results, the average number of hydrogen bonds, the Coulombic and van der Waals interactions between the peptide-water (PEP-Water) and between each group of peptide residues (PEP-PEP) indicate that, despite the occurrence of much water infiltration (especially in the I3V3A3G3K3 membrane, which has greater porosity than the K3G3A3V3I3 membrane), they still maintain a membrane structure. Our results allow a better understanding of the influence of the interactions between the peptides as well as the role of each group of amino acids residues, peptide terminus and solvent in membrane stability.

Poly (ethylene chlorotrifluoroethylene) (ECTFE) membrane presents interesting properties for microfiltration (MF) and membrane distillation (MD). In this paper, ECTFE is prepared via thermally induced phase separation (TIPS) process using acetyl tributyl citrate (ATBC) as an environmentally friendly diluent. Phase diagram of the ECTFE/ATBC system is measured, and the effects of ECTFE concentration and quenching bath temperature on the membrane structure, properties and performance are investigated, by characterizing with scanning electron microscope (SEM), pure water flux, contact angle, mechanical properties, mean pore size and porosity. The results show that the ECTFE membranes prepared with ATBC as diluent possessed spherulite structure, high hydrophobicity and liquid entry pressure of water (LEPw), promising permeate flux, salt rejection and mechanical strength in vacuum membrane distillation (VMD). The permeate flux reached to 22.3 L/(m2.h) with salt rejection rate of 99.9%. These results indicated that ECTFE membranes prepared with green diluent ATBC is an interesting candidate for VMD operation.