Performance Of Composite Membranes Research Articles

Effect of one- and two-dimensional nanomaterials on polysulfone-based anion exchange membranes for fuel cells

To investigate nanoparticle morphology's impact on the performance of composite anion exchange membrane (AEM), one-dimensional quaternized branched polyethyleneimine @multi-walled carbon nanotubes (QBPEI@MWCNTs) and two-dimensional quaternized branched polyethyleneimine @graphene oxide sheets (QBPEI@GO) were prepared and incorporated into quaternized polysulfone (QPSF) matrices to form QQ-x-MWCNTs and QQ-x-GO AEMs. These AEMs exhibited superior mechanical properties due to the flexible QBPEI cross-linking and nanoparticle reinforcement. Moreover, QBPEI facilitated microphase separation and ion cluster formation along the surface of nanoparticles, enhancing OH− transport. As a result, QQ-1.0%-MWCNTs and QQ-0.7%-GO AEMs both showed high ionic conductivity (83.19 mS/cm and 76.14 mS/cm at 80 °C). QQ-x-MWCNTs AEMs displayed higher conductivity than QQ-x-GO AEMs over the entire temperature range (20–80 °C) at the same level of ion exchange capacity. QQ-0.7%-MWCNTs AEM excelled, achieving a peak power density of 102.44 mW/cm2 in an H2/O2 fuel cell (80 °C, 40 % RH), surpassing QQ-0.5%-GO AEM (86.50 mW/cm2). Evidently, one-dimensional MWCNTs are effective for establishing long-range interconnected ion transport channels, making them excellent AEM fillers.

Photocatalytic hydrogen evolution on tubular shape cellulose acetate/crystalline nanocellulose/polyvinyl alcohol membranes with embedded nanocrystalline catalysts

In this work, we design an efficient and cost-effective porous membrane composed by polymeric blend that supports different photocatalytic materials. The thin (300 μm) porous photocatalytic membrane has a tubular shape and was flexible for easy handle in the reactor. The membrane is composed of a polymeric blend based on cellulose acetate, crystalline nanocellulose and polyvinyl alcohol, obtained by the phase inversion method, using cold water as non-solvent. Bismuthates (KBiO3, NaBiO3) and aluminates (ZnAl2O4 and Cu0·9Zn0·1Al2O4) powders were synthesized by diverse methodologies and were embedded into polymeric matrix. The hydrogen evolution performance of photocatalyst powders and photocatalytic composite membranes, under UV light irradiation during 180 min, were compared. The best result of hydrogen evolution was obtained by Cu0·9Zn0·1Al2O4 powders reaching 117.74 μmolg−1h−1 and the M−CuZn membrane reaching 90.07 μmolg−1h−1. The obtained results show the high potential of these polymeric membranes as a green alternative support for photocatalysts for hydrogen evolution.

Enhanced water permeability and antifouling properties of cross-linked graphene oxide composite membranes with tunable d-spacings

Low flux and membrane fouling are major challenges in membrane distillation (MD) for treating concentrated wastewater. This study compared the performance of GO composite membranes with different interlayer distances, by covalently bonding the terminal amine groups of ethylenediamine (EDA) and 1,12-diaminododecane (DADD) with the carboxyl groups present on the GO sheets. The results indicated that the GO-DADD/PTFE membrane, with longer carbon chain cross-linking, achieved the highest flux and antifouling properties. At 70 °C, the pure water flux reached 68.5 kg/m2·h, and the fluxes for treating NaCl, HA containing NaCl, and BSA containing NaCl were 29.8 %, 37.1 %, and 38.5 % higher than the uncrosslinked GO/PTFE, and 95.7 %, 121.2 %, and 146.9 % higher than the PTFE membrane, respectively. Through mathematical models for mass and heat transfer, the study identified the key to this enhancement as the increased d-spacing within the GO layer due to cross-linking, which weakened the Kelvin effect and enhanced the vapor partial pressure on the hot side. The unique surface structure and electrostatic interactions induced by long-chain cross-linking further boosted the antifouling effect. These modifications not only overcome the typical trade-off between retention rates and flux but also offer a scalable and efficient solution for advanced membrane distillation applications.

Metal-organic framework integrated surface-engineered polyelectrolyte membranes enhancing tetrahydrofuran dehydration

BackgroundEnhancing composite membrane performance is crucial for industrial separation processes. Integrating metal-organic frameworks (MOFs) into membranes offers a promising strategy. We introduce a novel approach by integrating HKUST-1 MOF within a polyelectrolyte matrix to improve membrane efficiency. MethodsA layer-by-layer self-assembly technique on a hydrolyzed polyacrylonitrile support integrates HKUST-1 into a polyelectrolyte matrix. Polyethyleneimine (PEI) and polyacrylic acid (PAA) form the polyelectrolyte layer through electrostatic interactions. The incorporation of HKUST-1 within the PEI matrix enhances separation efficiency, particularly in tetrahydrofuran dehydration, with optimal conditions using 100 ppm of HKUST-1 and forming 2 bilayers. Significant findingsUnder optimal conditions, the resulting membrane exhibits exceptional performance. It demonstrates a permeation flux of 1442.30 g∙m−2∙h−1, a water concentration in the permeate of 98.0 wt%, and a separation factor of 440. The modified membrane also shows remarkable stability across varying temperatures (25–55 °C) and tetrahydrofuran concentrations in the feed (10–90 wt%) during long-term testing. These findings highlight the membrane's potential for enhancing separation processes in the chemical industry.

Positively charged nanofiltration membranes with gradient structures for enhancing separation properties

Creating a gradient structure in a separation layer is an effective approach for enhancing separation performance of thin film composite membranes. Here we present the preparation of a positively charged nanofiltration membrane with a gradient structure. An inner layer consisting of a loose polyester separation layer with large pores was formed through the interfacial polymerization (IP) reaction between triethanolamine (TEA) and trimesoyl chloride (TMC). And a dense and thin top layer composed of a polyamide separation layer was obtained by secondary interfacial polymerization (SIP) reaction using polyethyleneimine (PEI) along with unreacted TMC and residual acyl chloride groups of IP reaction. The influences of TEA concentration, PEI concentration and SIP time on the physicochemical properties and separation performances of the membrane were systematically analyzed. Our results show that the presence of the gradient structure optimized mass transfer pathways and reduced mass transfer resistance, resulting in significantly improved permeability of 13.0 ± 0.5 L·m−2·h−1·bar−1 (over 3 times compared with control-PEI), high MgCl2 rejection of 91.7 ± 0.6 %, and an excellent stability and anti-fouling performance. Our work provides valuable insights and guidance for developing high-performance positively charged NF membrane with gradient structures.

Multidimensional nanochannel design and regulation of ultra-thin GOQDs-AGQDs composite membranes

Graphene-based composite membranes with long and tortuous transport paths restricted its efficient and wide application in substance separation and purification field. In this study, we propose a multidimensional mass-transfer channel construction method for fabricating highly permeable 2D laminar membranes with lots of stable molecular transport channels. In particular, a robust GOQDs-AGQDs composite membranes with adjustable interlayer sieving channels were prepared based on vacuum assisted self-assembly by intercalating AGQDs with average size of 7.5 nm between GOQDs with average size of 34.0 nm, which presented highly permeability with plentiful nano-channels in both vertical and horizontal directions. As the mass fraction of doped AGQDs reached to 60 wt%, the best performance of GOQDs-AGQDs composite membranes was obtained, with a functional layer thickness of 24.1 nm, good stability, and strong acid and alkali resistance. The usage of small diameter GOQDs with intercalating smaller diameter AGQDs extremely shortened the transfer channel path and slightly increased the interlayer spacing (8.26 to 8.75 Å), which dramatically improved its permeation flux of 14 times higher than that of the pure GO membrane with similar dye rejection, and reached to 133.3 L·m−2·h−1 under 2 bar at the optimized condition. This study provided insights into self-assembling small-sized 2D nanomaterials into membranes and fine-tuning their nanochannel structure.

Prompted by surface-engineered honeycomb Turing nanostructures: Reflections on polyamide structure, growth and performance

The robust correlation between the performance of thin-film composite (TFC) reverse osmosis membranes and the polyamide (PA) active layer determines the necessity of precise design of the PA layer, and this regulation primarily involves the surface morphology and internal characteristics of the PA layer. In this study, we fabricated honeycomb Turing structure or nanovoid-rich TFC series membranes using polar/nonpolar organic phase additives. Characterization and simulation results confirmed that the enhancement of membrane performance relied more on the abundant nanovoids within the PA layer rather than the ordered honeycomb lattice surface. Notably, the TFC-nDCE membrane with multilayer nanovoids exhibited an approximately 89 % improvement in water permeability while maintaining satisfactory salt rejection (98.29 %). We emphasized the significant role of nanovoids in the diffusion process of amine monomers and investigated the potential relationship between nanovoids and the degree of surface cross-linking. Building upon this, a new insight into the formation of nanovoids induced by PA anisotropic growth was presented through a careful analysis of the amine monomer diffusion rate and the morphological evolution of nanovoids. The structure-property relationship between internal structures, surface morphologies, and performances was systematically and thoroughly investigated, pointing out the direction for the rational design of TFC membranes.

Efficient Cr(VI) remediation by electrospun composite porous nanofibers incorporating biomass with metal oxides and metal-organic framework

To develop a highly efficient adsorbent to remediate and remove hexavalent chromium ions (Cr(VI)) from polluted water, cellulose acetate (CA) and chitosan (CS), along with metal oxides (titanium dioxide (TiO2) and ferroferric oxide (Fe3O4)), and a zirconium-based metal-organic framework (UiO-66) were used to fabricate the composite porous nanofiber membranes through electrospinning. The adsorption performance, influencing factors, adsorption kinetics and isotherms of composite nanofiber membranes were comprehensively investigated. The multi-layer membrane with interpenetrating nanofibers and surface functional groups enhanced the natural physical adsorption and provided potential chemical sites. The thermal stability was improved by introducing TiO2 and UiO-66. CA/CS/UiO-66 exhibited the highest adsorption capacity (118.81 mg g−1) and removal rate (60.76%), which were twice higher than those of the control. The correlation coefficients (R2) of all the composite nanofibers regressed by the Langmuir model were significantly higher than those by the Freundlich model. The pseudo-first-order kinetic curve of CA/CS composite nanofibers showed the highest R2 (0.973), demonstrating that the whole adsorption process involved a combination of strong physical adsorption and weak chemical adsorption by the amino groups of CS. However, the R2 values of the pseudo-second-order kinetic model increased after incorporating TiO2, Fe3O4, and UiO-66 into the CA/CS composite nanofiber membranes since an enhanced chemical reaction with Cr (VI) occured during the adsorption

Efficient separation of CO2/CH4 by covering ultrathin ionic liquid film on COF membrane

Covalent organic framework (COF) membranes show great potential for gas separation, but their large pore size make it hard to effectively separate gases with similar kinetic diameters. A promising strategy is to cover the surface of COF membranes with an ultrathin film of ionic liquids (ILs) to improve the selectivity of gas permeation. Here, we investigated the CO2/CH4 separation performance of composite membranes composed of COF (CTF-1) and 20 kinds of ILs, respectively, using molecular simulations. The [C4mim][PF6]/COF membrane is found to exhibit the best separation performance, with CO2 permeability up to 7.93 × 104 GPU and CO2/CH4 selectivity of 12.33 when the IL thickness is 8 Å. By studying the microstructure of the composite membrane, it was found that there is a relatively dispersed distribution of cations and anions on the COF surface, which is beneficial to the diffusion of gas molecules. The gas permeation process results reveal that CO2 rapidly achieves equilibrium in both the adsorption and dissolution layers simultaneously, thereby enhancing the permeation rate of gas molecules. The analysis of interaction energy and PMF indicates that the improved selectivity is due to the stronger interaction between IL and CO2 than that for CH4.

High performance mixed-dimensional assembled MXene composite membranes for molecular sieving

Two-dimensional (2D) separation membranes have proved their superiorities in addressing global water scarcity and recycling resources. However, current 2D membranes usually suffer from swelling and irregular stacking issues, which result in poor separation performance. Herein, we developed novel mix-dimensional assembled MXene composite membranes with high permeability and selectivity by intercalating 1D carboxylated cellulose nanofibers (CNFs) into 2D lamellar MXene nanosheets. The effects of chain length of CNFs and MXene/CNFs mass ratios on the morphologies, physicochemical properties, and separation performances of composite membranes were systematically investigated. The optimized MXC-3-L membrane exhibited superior rejection to Congo red (CR, >99%) and remarkable separation efficiency of dye/salt. The separation factors for the CR/NaCl and CR/Na2SO4 mixtures were 512.0 and 517.2, respectively. Moreover, the MXC-3-L membrane showed distinct rejections to perfluoroalkyl substances (PFAS) (>95%) with a nearly 8-fold increase of permeance in comparison with the commercial polyamide membrane. The 2D X-ray diffraction analysis verified that the intercalation of 1D CNFs into 2D MXene nanosheets via strong hydrogen bonding can regulate the nanochannel into more stable and regularly stacking lamellar structures, which plays a key role in high permeance and excellent molecular separation efficiency. In addition, 1D CNFs play an essential role as “threading” and “stitching”, shielding the defects between adjacent MXene nanosheets and improving the separation efficiencies. Our work provides new insights into design of defect-free and highly selective 2D materials-based membranes for enhanced wastewater treatment and molecular sieving.

Alkaline-oxidized MXene composite membrane of ultra high flux and advanced rejection performance for water purification

MXene is a metal-carbon/nitrogen compound material with a two-dimensional layered structure. As a new form of two-dimensional material, it has great potential in the field of water purification because of its properties of high permeability and hydrophilicity. In this study, a MXene composite membrane was prepared by in-situ oxidation of titanium dioxide on the MXene surface by an alkaline oxidation method. A series of characterizations of the prepared MXene composite membrane was carried out. Scanning electron microscopy showed that with an increasing degree of oxidation, the extent of agglomeration of MXene nanosheets increased, thus generating more water channels that are conducive to the transport of water molecules, and an increasing water flux. The penetration performance, interception performance, and stability of the MXene composite membrane were tested. The effect of different concentrations of KOH on the properties of the composite membrane was investigated. It was found that the flux of the composite membrane increased with alkali concentration by 4.6–28.8 times the flux without exposure to alkali. It was found that the rejection rate of the composite membrane for pollutants (dyes, humic acid, bovine serum albumin protein) decreased only slightly with increasing alkali concentration, and was ≥94% of the pure MXene membrane rejection rate in all cases. The rejection performance of the composite membrane was related to the size and charge properties of the pollutant molecules. The results of the stability tests showed that the composite membranes had a high degree of physical and flux stability in a range of aqueous solutions.

Preparation and performance of magnetic carbon nanotubes modified PVC substrate composite nanofiltration membranes

Polyamide (PA)/ferroferric oxide/oxidized multi-walled carbon nanotubes (Fe3O4/o-MWCNTs)/polyvinyl chloride (PVC) composite nanofiltration (NF) membranes were prepared by the interfacial polymerization (IP) process with the Fe3O4/o-MWCNTs/PVC porous membrane as the substrate membrane, which was prepared by the magnetic field assisted non-solvent induced phase separation method (NIPS) with the synthesized superparamagnetic Fe3O4/o-MWCNTs nanoparticles (NPs) as the additives of the functional intermediate layer integrated with the substrate. The effects of the magnetic carbon nanotubes modified PVC porous substrate membrane on the surface chargeability, PA layer thickness, mechanical properties, pressure resistance and permeability of the composite NF membranes were investigated, and the comprehensive performance of composite NF membranes was enhanced. The results indicated that the porosity and hydrophilicity of the Fe3O4/o-MWCNTs/PVC porous substrate membrane were improved by the migration of magnetic Fe3O4/o-MWCNTs NPs to the upper edge of the substrate membrane and uniform enrichment under magnetic field induction, which further affected the structure and properties of the PA/Fe3O4/o-MWCNTs/PVC composite NF membrane. The prepared NF membrane presented smaller roughness, thinner PA layer, larger pore size, with excellent mechanical properties and better pressure resistance. Meanwhile, the PA/Fe3O4/o-MWCNTs/PVC composite NF membrane presented excellent divalent salt rejection, with the rejection of MgSO4 and Na2SO4 maintaining more than 95.2% and 93.4%, respectively, while the permeation flux could reach 35.4 L·m−2·h−1. In summary, the modification of the substrate integrated with the functional intermediate layer had certain enlightening significance for the preparation of the NF membrane with excellent comprehensive performance.

Low cytotoxicity, antibacterial property, and curcumin delivery performance of toughness-enhanced electrospun composite membranes based on poly(lactic acid) and MAX phase (Ti3AlC2)

MXenes, synthesized from their precursor MAX phases, have been extensively researched as additives to enhance the drug delivery performance of polymer matrices, whereas there is a limited number of previous reports on the use of MAX phases themselves for such applications. The use of MAX phases can exclude the complicated synthesis procedure and lessen resultant production and environmental costs required to convert MAX phases to MXenes. Herein, electrospun membranes of poly(lactic acid) (PLA) and a MAX phase (Ti3AlC2) have been fabricated for curcumin delivery. The composite membrane exhibits significantly higher toughness (8.82 MJ m−3) than the plasticized PLA membrane (0.63 MJ m−3) with low cytotoxicity, supporting proliferation of mouse fibroblast L929 cells. The curcumin-loaded composite membrane exhibits high water vapor transmission (∼7350 g m−2 day−1), porosity (∼85 %), water wettability, and antibacterial properties against E. coli and S. aureus. Seven-day curcumin release is enhanced from 45 % (PLA) to 67 % (composite) due to curcumin diffusion from the polymer fibers and MAX phase surface that contributes to overall increased curcumin adsorption and release sites. This work demonstrates the potential of the MAX phase to enhance both properties and curcumin delivery, promising for other eco-friendly systems for sustainable drug delivery applications.

The Performance of Cellulose Composite Membranes and Their Application in Drinking Water Treatment.

Water scarcity and water pollution have become increasingly severe, and therefore, the purification of water resources has recently garnered increasing attention. Given its position as a major water resource, the efficient purification of drinking water is of crucial importance. In this study, we adopted a phase transition method to prepare ZrO2/BCM (bamboo cellulose membranes), after which we developed IP-ZrO2/BC-NFM (bamboo cellulose nanofiltration membranes) through interfacial polymerization using piperazine (PIP) and tricarbonyl chloride (TMC). Subsequently, we integrated these two membranes to create a combined "ultrafiltration + nanofiltration" membrane process for the treatment of drinking water. The membrane combination process was conducted at 25 °C, with ultrafiltration at 0.1 MPa and nanofiltration at 0.5 MPa. This membrane combination, featuring "ultrafiltration + nanofiltration," had a significant impact on reducing turbidity, consistently maintaining the post-filtration turbidity of drinking water at or below 0.1 NTU. Furthermore, the removal rates for CODMN and ammonia nitrogen reached 75% and 88.6%, respectively, aligning with the standards for high-quality drinking water. In a continuous 3 h experiment, the nanofiltration unit exhibited consistent retention rates for Na2SO4 and bovine serum protein (BSA), with variations of less than 5%, indicating exceptional separation performance. After 9 h of operation, the water flux of the nanofiltration unit began to stabilize, with a decrease rate of approximately 25%, demonstrating that the "ultrafiltration + nanofiltration" membrane combination can maintain consistent performance during extended use. In conclusion, the "ultrafiltration + nanofiltration" membrane combination exhibited remarkable performance in the treatment of drinking water, offering a viable solution to address issues related to water scarcity and water pollution.

Effect of poly(2-(dimethylamino)ethyl methacrylate) brush-grafted graphene oxide on polyamide layer formation and nanofiltration performance

Thin film composite (TFC) membrane performance is often restricted by permeability and selectivity trade-off effect, even with the modification of nanoparticles. Graphene oxide-poly(2-(dimethylamino)ethyl methacrylate) (GO-PDMAEMA) with brush structure has abundant hydrophilic oxygen-containing functional groups and amine groups. It was synthesized via the atom transfer radical polymerization method and incorporated into TFC polyamide layer using interfacial polymerization. The GO-PDMAEMA-modified thin film nanocomposite membranes (TFNG-P) with Turing structure and higher surface hydrophilicity enhanced water permeability by 40.7–55%, with relatively low nanoparticle loading (0.005–0.02 wt%). Besides, TFNG-P2 (0.01 wt% GO-PDMAEMA) has the highest Na2SO4 rejection (97.8%), 4.4% higher than TFC. The PDMAEMA brushes on GO with additional amine groups promoted the amide linkage and increased the PA layer cross-linking by 16.2%. The higher cross-linking did not negatively affect the membrane flux, as the better hydrophilicity offset this effect. The utilization of the modified membranes in the treatment of palm oil mill effluent demonstrated enhanced resistance to fouling with TFNG-P2, which exhibited the highest flux recovery rate, reaching 89.4%. Thus, this study showed GO modification by grafting PDMAEMA brushes had enhanced the membrane properties, resulting in TFNG-P with higher permeability, promising separation and antifouling performance.

Enhanced PEBA composite membrane performance by solution-free melt coating for phenol pervaporation from aqueous solution

Solution-based membrane fabrication methods, which are widely used in the membrane industry, have a negative impact on the environment and fabrication effectiveness. In this study, a green solution-free melt coating method was proposed to rapidly fabricate a poly(ether-block-amide) copolymer (PEBA) composite membrane. Based on its melting point and viscosity, PEBA 1074 was chosen as a suitable membrane material for fabrication by solution coating and melt coating methods, which were compared by characterizations such as variable-temperature synchrotron X-ray diffraction and nano-scratching test to reveal the differences in such as crystallinity etc. The separation performance of these membranes for the pervaporation of phenol from aqueous solutions under different operating conditions was evaluated. The results showed that the PEBA composite membrane fabricated by the melt coating method possessed the same separation factor as the corresponding freestanding membrane because the sol-gel transition was avoided, and a separation factor of 74 for the separation of 1.5 wt% phenol/water solution at 70 °C can be obtained due to high density and crystallinity even with a thickness of 11 μm, which is superior to previously reported results. This study provides an ecologically friendly and effective approach for the fabrication of thermoplastic polymer membranes, thereby promoting their industrial applications.

Design of PDMS/PAN composite membranes with ultra-interfacial stability via layer integration.

The interfacial interaction between the selective layer and porous substrate directly determines the separation performance and service lifetime of functional composite membranes. Till now, almost all reported polymeric selective layers are physically in contact with the substrate, which is unsatisfactory for long-term operation. Herein, we introduced a functional composite membrane with ultra-interfacial stability via layer integration between the polydimethylsiloxane selective layer and polyacrylonitrile substrate, where a facile light-triggered copolymerization achieved their covalent bonding. The critical load for the failure of the selective layer is 45.73 mN when testing the interfacial adhesion, i.e., 5.8 times higher than that before modification and significantly higher than previous reports. It also achieves superior pervaporation performance with a separation factor of 9.54 and membrane flux of 1245.6 g m-2 h-1 feeding a 1000 ppm phenol/water solution at 60 °C that is significantly higher than the same type of polymeric ones. Not limited to pervaporation, such a strategy sheds light on the design of highly stable composite membranes with different purposes, while the facile photo-trigged technique shows enormous scalability.

Triazole-rich 3D metal-organic framework incorporated solid electrolytes for superior proton conductivity and durability in fuel cells.

Insufficient proton conductivity and oxidative stability of sulfonated hydrocarbons hinder their applicability as proton exchange membrane electrolytes in fuel cells. In this regard, fabrication of proton conducting mixed-matrix membranes (PC-MMMs) can be a superior approach to obtain desirable properties. In this work, a triazole ligand (1H-1,2,4 triazole) was coordinated to a zinc metal node to create a 3D metal-organic framework (MOF) and incorporated as an additive in a sulfonated poly(ether ether ketone) matrix at 1, 3, and 5 weight percentage to fabricate PC-MMMs by the casting process. Several characterization tools such as electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterise these membranes and study their potential application as electrolyte(s) in PEMFCs (proton exchange membrane fuel cells). Membranes were also tested for water uptake, ion-exchange capacity and oxidative stability in Fenton's reagent. The performance of the polymeric composite membrane containing a 3 wt% MOF was then assessed in a H2/O2 single cell as it demonstrated the highest proton conductivity of 0.04 S cm-1 among all the compositions and a maximum current density of 1191 mA cm-2. The membrane was also subjected to an OCV hold test for 12 hours to study the chemical durability over a period of time. This report establishes that the inclusion of a triazole based MOF enhances the proton conductivity, performance, and thermal and chemical durability of composite membranes which can be considered as a promising electrolyte material at intermediate temperatures after a proper optimisation of different cell parameters.

Tailoring the CH4/CO2/N2 separation performance of ultrapermeable polymeric composite membranes by altering the concentration of Pd/g-C3N4

Effectively tailoring the interfacial interaction between the nanoadditives and polymer matrix to develop defect-free membrane is the key parameter to fabricate mixed matrix membranes (MMMs) with improved gas separation performance. Here, MMMs were successfully fabricated by using Pd/g-C3N4 as a nanoadditive for the separation of CO2/CH4 and CO2/N2 gas mixtures. The g-C3N4 with palladium provides more compatible structure to the MMMs. The addition of Pd/g-C3N4 nanoadditive introduces additional functional groups into the membrane matrix which induces the permeability of the molecules. The Pd/g-C3N4:PSf MMMs exhibited better thermal, mechanical stability and gas permeability than the bare polysulfone (PSf) membrane. The MMM loaded with 300 mg of the nanoadditive exhibited greater permeability than unfilled membrane which is nearly 5 times for CH4, 4 times for N2 and 10 times for CO2 at 2 bar pressure with selectivity of 5.25 for CO2/CH4 and 2.15 for CO2/N2 mixtures. The permeability of the CO2 molecules is higher than the N2 and CH4 molecules because of its smaller kinetic diameter. The Pd/g-C3N4 nanoadditive exhibited microporous nature with presence of nitrogen-rich functional groups which develops CO2-philic functional groups in MMMs. These findings emphasize the unique properties of Pd/g-C3N4 nanoadditive in MMMs towards pure and mixed gas permeability and separation. This simplistic approach to modulate PSf membrane via Pd/g-C3N4 addition promotes the practical design of highly effective gas separation membranes.

Unveiling the impact of monomer reactivity on the morphology and functionality of thin-film composite membranes

This study delves into the impact of monomer selection and reaction pH on the morphology and performance of thin-film composite (TFC) membranes. The research provides an understanding of how polyamide (PA), polyester amide (PEA), and polyester (PE) membranes can be tailored for specific applications, employing piperazine (PIP) and glucose as monomers in aqueous solution alongside trimesoyl chloride (TMC) as a monomer in an organic solution. PEA-based membranes containing glucose demonstrated several notable improvements, including a reduced contact angle of 60 degrees, a smoother surface, and a more negative zeta potential. These enhancements underscore their increased hydrophilicity, decreased susceptibility to fouling, and heightened surface charge. Controlling pH during fabrication significantly changed the membrane surface charge, hydrophilicity, water flux, and rejection rate. At pH 11, the PA membrane excelled in rejection performance (99.5% Na2SO4, 32% NaCl, and 97.8% methyl orange) with a trade-off in lower water flux (56 LMH). Conversely, the PE membrane achieved the highest water flux (173 LMH) but lower rejection (58% Na2SO4, 10% NaCl, and 97% methyl orange). The PEA membrane offered notable water flux (82.5 LMH) and high rejection for methyl orange (99.3%) and Na2SO4 (99.2%). Increasing the pH reduced permeation rates but enhanced rejection, especially for NaCl. The PE and PEA membranes exhibited remarkable antifouling properties, boasting a flux recovery ratio compared to the PA membrane. This study highlights the pivotal role of monomer selection and pH control in TFC membrane performance, offering prospects for innovative design and optimization in water treatment membrane technology.