Microstructure Of Membranes Research Articles

Anti-swelling gel polymer electrolyte membrane for high-performance lithium-ion battery

Gel polymer electrolyte (GPE) represents an effective and advanced substitution of polyolefin separator in high-rate lithium-ion rechargeable batteries. We here develop a novel pyridine ionic liquid (IL)-based GPE membrane for that purpose via a one-step reactive vapor-induced phase separation (RVIPS) method. Casting mixture solution of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and 1-butylpyridinium hexafluorophosphate ([C4Py]PF6) to evaporate solvent in ammonia water vapor, the IL-based membrane was successfully prepared in one step. The effects of the IL content on the membrane microstructure were investigated in detail. Our results demonstrate that the pyridine IL plays a role as plasticizer to suppress crystallization of the polymer, while the RVIPS process can induce dehydrofluorination-crosslinking of PVDF-HFP to greatly reduce swelling of the membrane in liquid electrolyte. Based on those, the GPE from the membrane containing 10 % [C4Py]PF6 exhibits the best electrochemical properties (ionic conductivity of 1.48 mS cm−1, Li+ transference number of 0.66, and electrochemical stable window of 5.2V), though it uptakes a moderate amount of liquid electrolyte. Moreover, the long-term interfacial stability of the GPE with the metal anodes was checked to indicate its suitability as excellent GPE. According to the battery tests, the GPE exhibits superior discharge capacities at high C-rates, achieving 129.7 mAh g−1 at 3C and 115.5 mAh g−1 at 5C, while remains a low capacity decay of 0.014 % per cycle over 300 cycles at 3C. Therefore, our work provides a facile strategy of one-step RVIPS to prepare pyridine ionic liquid-based GPE, which demonstrates promising potential for high-performance rechargeable lithium-ion battery.

Precursor-chemistry engineering toward ultrapermeable carbon molecular sieve membrane for CO2 capture

Carbon capture is an important strategy and is implemented to achieve the goals of CO2 reduction and carbon neutrality. As a high energy-efficient technology, membrane-based separation plays a crucial role in CO2 capture. It is urgently needed for membrane-based CO2 capture to develop the high-performance membrane materials with high permeability, selectivity, and stability. Herein, ultrapermeable carbon molecular sieve (CMS) membranes are fabricated by pyrolyzing a finely-engineered benzoxazole-containing copolyimide precursor for efficient CO2 capture. The microstructure of CMS membrane has been optimized by initially engineering the precursor-chemistry and subsequently tuning the pyrolysis process. Deep insights into the structure-property relationship of CMSs are provided in detail by a combination of experimental characterization and molecular simulations. We demonstrate that the intrinsically high free volume environment of the precursor, coupled with the steric hindrance of thermostable contorted fragments, promotes the formation of loosely packed and ultramicroporous carbon structures within the resultant CMS membrane, thereby enabling efficient CO2 discrimination via size sieving and affinity. The membrane achieves an ultrahigh CO2 permeability, good selectivity, and excellent stability. After one month of long-term operation, the CO2 permeability in the mixed gas is maintained at 11,800 Barrer, with a CO2/N2 selectivity exceeding 60. This study provides insights into the relationship between precursor-chemistry and CMS performance, and our ultrapermeable CMS membrane, which is scalable using thin film manufacturing, holds great potential for industrial CO2 capture.

A Smart Polycage Membrane with Responsive Osmotic Energy Conversion Based on Synchronously Switchable Microporosity and Chargeability.

Membranes with specific pore sizes are widely used in molecular separation, ion transport, and energy conversion. However, the molecular understanding of structure-property performance in membrane science has been an urgent and long-standing problem. A promising but challenging solution lies in the fine-tuning of the membrane microstructure and properties to control membrane performance. Here, we designed an exofunctionalized triskelion cage to construct smart polycage membranes with concurrently responsive pore apertures and charge property. The synthetic polyaza cage is decorated with exoextended aldehyde groups for membrane fabrication and multiple amine sites for postmodification. The engineered polycage membranes thereby are endowed with pH-responsive porosity and chargeability, which serve as excellent candidates to explore the influence of the pore size and charge properties on membrane performance. In this regard, we successfully demonstrated the responsive osmotic energy conversion of the polycage membrane with a power density increase of over fourfold. This result indicates that the chargeability here outcompetes microporosity in energy conversion performance, which is further supported by molecular simulations. Therefore, this smart polycage membrane not only offers a feasible strategy to regulate the membrane microstructure and charge property reversibly but also balances pore size and chargeability to control the membrane performance at the molecular level.

Physical and Chemical Dual Confinement Promotes Controllable Synthesis of Loose-Structured Azine-Linked Nanofilms for Fast Molecular Separation.

Thin-film composite (TFC) membranes, featuring nanoscale film thickness and customizable pore structures, hold promise for solute-solute separations. However, achieving on-demand molecular sieving requires fine control over the membrane microstructure. Here, the concept of physical and chemical dual confinement (PCDC) is introduced to fabricate loose-structured TFC membranes via confined interfacial polymerization (IP). This concept leverages the synergistic effects of physically restricted monomer diffusion and a chemically inhibited reaction to achieve controlled nanofilm growth. Dorsal addition of the aqueous phase to the hydrogel reduces the diamine diffusion via electrostatic and H-bonding interactions within its nanopores. The prepassivation of hydrazine using acid protonation effectively weakens its ability for nucleophilic reactivity. This confined IP between twisted TFPA and short-chain hydrazine yielded loosely structured azine-linked nanofilms, which displayed a high permeability of 53.4 LMH bar-1 and effective differentiation of binary mixtures. This PCDC concept offers a useful guideline to finely tailor polymeric nanofilms for precise separations.

Quaternized poly(aryl imidazolium) containing bulky binaphthyl group as proton exchange membrane for high-temperature fuel cells

The low power output and high phosphoric acid (PA) leakage are the main constraints restricting the commercialization of PA-doped high-temperature proton exchange membranes (HT-PEMs). Ionized imidazoles have been shown to be an effective strategy to improve PA retention, however, less research has been conducted on the fractional free volume (FFV) of the backbone of the main chain on PA loss. Herein, novel imidazolium ions polymer (PQBN-4-IM) material with bulky binaphthyl (BN) group was prepared as PA-doped HT-PEM using a one-step superoxid acid catalyzed polycondensation and subsequent methylation process. The rigidity and hydrophobicity of the BN group promote PQBN-4-IM PEM to produce more obvious microphase separation morphology and large FFV, which is beneficial for forming better ion transport channels and excellent PA interaction. Notably, the PA-doped PQBN-4-IM (PQBN-4-IM/PA) membrane has the highest proton conductivity (90.26 mS cm−1, 180 ℃) and peak power density (PPD) (802.5 mW cm−2, 180 ℃) than PQTP-4-IM/PA and m-PBI/PA HT-PEMs. Moreover, the PQBN-4-IM/PA membrane has higher PA retention at 80 ℃/40 % relative humidity (RH), 40 ℃/60 % RH, or immersed in water due to enhancement on ion-pair interactions by microstructure. Under the accelerated stress test (AST) of the fuel cell (FC), the PQBN-4-IM/PA membrane loses only 12.22 % of PPD after 200 cycles at 80 ℃, which exhibits higher PPD retention than that of the PQBP-4-IM/PA (70.23 %), PQTP-4-IM/PA (74.36 %) and m-PBI/PA (65.25 %) membranes, and shows excellent durability of cell performance for more than 1000 h without significant voltage decay at 160 °C. Thus, the outstanding performance suggests that the microstructure and morphology of imidazolium ions polymer membranes significantly influence proton conductivity, performance, and the durability of a cell.

Fabrication of high-performance SiC ceramic membranes modified using in situ grown mullite whiskers and high-temperature filtration

The gas permeance and particle removal efficiency of silicon carbide (SiC) membranes are the most important performance indicators for high-temperature gas filtration. The rational design of SiC membrane microstructure has a positive impact on the improvement of performance indicators. This work prepared SiC membranes modified by in situ grown mullite whiskers, optimized their preparation conditions and investigated their performance improvement. The membrane suspension composition and sintering temperature were optimized using Taguchi’s method and gas permeance as the target. The thickness of the membrane was regulated by adjusting the spraying cycles and solid content in membrane suspension. Results showed that best membrane performance was obtained when the content of sintering aids, MoO3, and AlF3·3H2O were 8, 12, and 12 wt%, respectively; the solid concentration in membrane suspension was 30 wt%; the number of spraying cycles was 2, and the temperature was 1350 °C. The resulting membrane obtained a pore size of 5.8 µm and the Darcy's permeability coefficient k was 8.58 × 10−12 m2. It also had good interfacial adhesion and thermal shock and corrosion resistances. The membrane achieved a PM2.5 removal rate of more than 99.9 % at room temperature and high temperatures (100 °C–400 °C) with a low pressure drop below 1.4 kPa. Overall, the SiC ceramic membranes are prospective candidates for dust-laden gas filtration at high temperatures.

Mechanical and suture-holding properties of a UV-cured atelocollagen membrane with varied crosslinked architecture

The mechanical competence and suturing ability of collagen-based membranes are paramount in guided bone regeneration (GBR) therapy, to ensure damage-free implantation, fixation and space maintenancein vivo. However, contact with the biological medium can induce swelling of collagen molecules, yielding risks of membrane sinking into the bone defect, early loss of barrier function, and irreversibly compromised clinical outcomes. To address these challenges, this study investigates the effect of the crosslinked network architecture on both mechanical and suture-holding properties of a new atelocollagen (AC) membrane. UV-cured networks were obtained via either single functionalisation of AC with 4-vinylbenzyl chloride (4VBC) or sequential functionalisation of AC with both 4VBC and methacrylic anhydride. The wet-state compression modulus (Ec) and swelling ratio (SR) were significantly affected by the UV-cured network architecture, leading up to a three-fold reduction in SR and about two-fold increase inEcin the sequentially functionalised, compared to the single-functionalised, samples. Electron microscopy, dimensional analysis and compression testing revealed the direct impact of the ethanol series dehydration process on membrane microstructure, yielding densification of the freshly synthesised porous samples and a pore-free microstructure with increasedEc. Nanoindentation tests via spherical bead-probe atomic force microscopy (AFM) confirmed an approximately two-fold increase in median (interquartile range (IQR)) elastic modulus in the sequentially functionalised (EAFM= 40 (13) kPa), with respect to single-functionalised (EAFM= 15 (9) kPa), variants. Noteworthy, the single-functionalised, but not the sequentially functionalised, samples displayed higher suture retention strength (SRS = 28 ± 2-35 ± 10 N∙mm-1) in both the dry state and following 1 h in phosphate buffered saline (PBS), compared to Bio-Gide® (SRS: 6 ± 1-14 ± 2 N∙mm-1), while a significant decrease was measured after 24 h in PBS (SRS= 1 ± 1 N∙mm-1). These structure-property relationships confirm the key role played by the molecular architecture of covalently crosslinked collagen, aimed towards long-lasting resorbable membranes for predictable GBR therapy.

Polyamide membranes with tannic acid-ZIF-8 for highly permeable and selective ion-ion separation

Highly permeable polyamide (PA) membranes with precise ion selection can be used for many energy-efficient chemical separations but are limited by membrane inefficiencies. Herein, polyphenol-mediated ZIF-8 nanoparticles with hydroxyl-rich hollow structure were synthesized by tannic acid tailored regulation. PA-based membranes with fast penetration, high retention, and precise Cl−/SO42− selection were then synthesized through spatially and temporally controlling interfacial polymerization with modified ZIF-8 nanoparticles (tZIF-8) as aqueous phase additives or as interlayers. The effects of the embedding position of tZIF-8 on the structure, morphology, physicochemical properties, and performance of PA-based membranes were explored through a sequence of characterization techniques. The results revealed that the PA-based membrane with tZIF-8 embedded in the PA layer could achieve a high water permeance of 24.8 L m−2 h−1 bar−1 with a high retention of 99.4 % Na2SO4 and a Cl−/SO42− selectivity of 141, which was superior to most state-of-the-art PA-based membranes. Comparatively, the Cl−/SO42− selection of the PA-based membrane with tZIF-8 embedded between the PA layer and the substrate was 136, while the water permeance was slightly enhanced to 28.2 L m−2 h−1 bar−1. Excitingly, the resulting membranes all exhibit superior antifouling properties and stability. Our facile strategy for tuning membrane microstructures provides new ideals into the development of highly permeable and excellently selective PA-based membranes for precise ion sieving.

Deep learning-assisted prediction and profiled membrane microstructure inverse design for reverse electrodialysis

Compared to traditional inter-membrane spacers, profiled ion exchange membranes significantly improve the energy harvesting performance of reverse electrodialysis (RED). Here computational fluid dynamics is employed to generate data regarding the flow and mass transfer characteristics and performance index under different profiled membrane microstructures. Data-driven deep learning models are constructed for microstructure shape generation, physics field prediction, and performance forecasting. Results show that the microstructure shape generation via the Bezier generative adversarial network, the physical field prediction via conditional generative adversarial network for the velocity field and the performance prediction via multi-layer perceptron for power number and Sherwood number achieves satisfied accuracy, respectively. The gradient descent algorithm is utilized to optimize the microstructure shape achieving higher mass transfer performance and lower pump power consumption. Compared to the traditional straight ridge channel, the optimized microstructure channel exhibits a reduction of 18.85 % in the power number and an increase of 41.00 % in the Sherwood number, rendering significantly boosted performance.

Enhanced Organic Solvent Nanofiltration Membranes with Double Permeance via Laser‐Induced Graphitization of Polybenzimidazole

AbstractThis study investigates the fabrication of organic solvent nanofiltration (OSN) membranes through laser‐induced graphitization of polybenzimidazole (PBI). Employing a CO2 laser, the polymer is converted into graphene, resulting in controlled submicron‐scale porous 3D structures, a feat not achievable with traditional methods such as chemical crosslinking. The effectiveness of this process hinges on precise adjustments of laser parameters, such as fluence, to attain the ideal graphitization levels. The findings indicate that partial graphitization, as opposed to excessive, is crucial for preserving the membrane's microstructure and enhancing its functional properties. The partially graphitized PBI‐LIG (Polybenzimidazole ‒ Laser‐induced Graphene) membranes achieved up to 94% rejection of Congo red from ethanol, with an ethanol permeance rate of 12.14 LMH bar−1—nearly twice that of standard PBI membranes. Additionally, these membranes showcased outstanding chemical stability and solvent resistance, maintaining over 99% structural integrity and experiencing <1% weight loss after prolonged exposure to various industrial solvents over a week. These results highlight the potential of laser‐graphitized PBI membranes for applications in harsh chemical conditions, paving the way for further optimization of high‐performance OSN membranes. This research advances membrane technology, merging laser engineering with materials science, and contributes to environmental sustainability and industrial efficiency.

Solvent-free green synthesis of anion exchange membranes via photo-polymerization for efficient desalination by electrodialysis

A green anion exchange membrane for electrodialysis desalination was synthesized using a solvent-free photo-polymerization approach. Vinylbenzyl chloride (monomer), tripropylene glycol diacrylate (crosslinker), and photoinitiator were mixed and subjected to UV polymerization for 20 min to create the base membrane, followed by positive charge modification with 1-methylimidazole. This method avoids organic solvents, offering economic and environmental benefits. By adjusting the degrees of crosslinking and positive charge, precise control over the membrane's microstructure and properties was achieved. The optimized membrane showed an area resistance of 1.67 Ω cm2 and a transport number of 0.956, demonstrating exceptional electrochemical performance. Under comparable conditions, the optimized membrane improved the NaCl removal rate by 11.47 %, increased current efficiency by 10.61 %, and reduced energy consumption by 16.75 % compared to commercial AMV membrane, highlighting its potential for scalable seawater desalination through electrodialysis.

The role of one-dimensional materials in modulating the selective mass transport of covalent organic framework membranes for nanofiltration

Two-dimensional covalent organic frameworks (2D COFs) membranes have well-ordered nanochannels for selective molecular sieving. One-dimensional (1D) materials have been proposed to link the loosely packed COFs nanosheet for enhancing the separation performance of COFs membranes. However, it remains unclear how the enhancement arises. Herein, we demonstrate the role of 1D materials in modulating the microstructure and interlayer force of 2D COFs membranes. The optimized composite membrane, assembled from 2D COFs and chitosan exhibits a 75% enhancement in permeance without sacrificing selectivity towards different dyes. Our results show that the interaction forces between COFs and 1D materials are directly correlated to the transport nanochannels. When the interaction forces are stronger, the microstructure is more densely packed. Meanwhile, the shielding effect of 1D materials on the intrinsic channels of 2D COFs is more significant, resulting in narrow transport channels for mass transfer. In contrast, the weaker interaction forces prevent the excessive shrinkage of nanochannels, facilitating fast mass transfer and maintaining the high molecular selectivity. The work unravels the interaction forces between 2D COFs and 1D materials leading to the shaping of mass transfer nanochannels, offering a new perspective for the advancement of COFs membrane for nanofiltration.

Effect of N-isopropylacrylamide and graphene oxide on the microstructure and performance of thermo-responsive membranes by Ce (IV)-induced redox radical polymerization

In this study, a series of novel thermo-responsive materials were synthesized using polyvinylidene fluoride, N-isopropylacrylamide (NIPAM) and graphene oxide (GO) via Ce (IV)-induced redox radical polymerization name as PNG. Thermo-responsive membranes were prepared by non-solvent induced phase separation. The results demonstrated that the CO and N-H stretching absorption intensities increased with the addition of NIPAM. XPS analysis demonstrated that the PNG1 membrane exhibited abundant functional group structure under the dosage of NIPAM at 1 g. The finger-like porous structure of membrane became longer and wider with the addition of NIPAM at 1 g, leading to a maximum porosity of 45.5 %. The CA decreased from 62.4 ° to 49.0 ° at 35 °C under the adding dosage of NIPAM at 1 g. The temperature-sensitive of PNG1 membrane was 35 °C. In addition, The PNG1 membrane had the lower Rir and higher flux recover than the others under the BSA rejection. According to the XDLVO theory analysis, the total interaction energy for PNG1 membrane achieved the maximum absolute values of −33.850 mJ/m2 and −19.956 mJ/m2 than the others under the temperature at 25 °C and 35 °C. This interaction influenced the adsorption between the pollutant and membrane surface, resulting in reversible fouling.

Exploring of novel reverse thermally induced phase separation process based on preparation and characterization of polysulfate ultrafiltration membranes with bicontinuous structure

AbstractContaminated water sources from various industries pose severe environmental challenges due to their complex compositions, high toxicity, and fluctuating qualities. This study introduces a groundbreaking strategy for fabricating advanced polysulfate (PSE) ultrafiltration membranes using a novel reverse thermally induced phase separation (RTIPS) process. By manipulating the cloud point through the DMAc/DEG solvent/nonsolvent system, our work innovatively controls membrane microstructure, overcoming limitations of conventional nonsolvent‐induced phase separation (NIPS). Our findings reveal that RTIPS, when employed above the cloud point, yields PSE membranes with a unique bicontinuous sponge‐like structure, significantly improving upon conventional NIPS products. Specifically, the optimized RTIPS membranes exhibit enhanced pure water flux (916.23 vs. 336.23 LMH), larger pore sizes (0.083 vs. 0.054 μm), increased tensile strength (1.32 vs. 0.84 MPa), and improved fouling resistance (FRR 65.5% vs. 55.2%). This research pioneers a facile yet potent method for tailoring membrane properties, achieving a balance between permeability, mechanical stability, and filtration efficacy. The demonstrated success of RTIPS in enhancing PSE membrane performance not only contributes to the development of high‐performance water treatment technologies but also charts a new course in membrane science, offering a promising avenue for sustainable wastewater management solutions.

Highly selective thin B-oriented MFI zeolite membranes on scalable modified stainless steel supports

Enhancing the separation performance of molecular sieve membranes relies significantly on precise control over their membrane morphology and microstructure. This involves creating thin, closely packed, oriented, and uniform coatings of seed crystals, enabling subsequent intergrowth to establish continuous membranes. To address industrial needs, it is crucial to generate a thin and flawless membrane efficiently producible on a large-scale support. Porous stainless supports offer scalability and easy integration into membrane modules. In this study, we present a novel and straightforward process for modifying stainless-steel supports to seed zeolite membrane layers. High-performance, b-oriented MFI zeolite membranes can be synthesized on these modified stainless-steel supports through scalable filtration seeding of MFI zeolite nanosheets followed by secondary growth. By employing a carefully designed pre-treatment procedure, we achieved the growth of well-intergrown, highly b-oriented MFI zeolite membranes on the modified stainless-steel support, establishing a robust interaction with the substrate. The membranes, fabricated through gel-free secondary growth of nanosheets deposited on a scalable stainless-steel support using this technique, demonstrate ultra-selective capabilities in separating para-xylene from ortho-xylene, with a high separation factor of 388.

Solar/microwave-driven composite membrane evaporation and its application in seawater desalination

Increased economic growth and population expansion has heightened the demand for water resources, leading to escalating levels of water scarcity. Sustainable seawater desalination methods, powered by renewable energy, offer promising solutions to the long-standing global water shortage. This study presents a method for seawater desalination that employs eco-friendly materials. The approach involves utilizing metakaolin-based porous geopolymer (GP) as the base material, and depositing graphene oxide (GO) to create a graphene oxide geopolymer (GOGP) composite membrane. The membrane undergoes in-situ self-reduction to obtain reduced graphene oxide geopolymer (rGOGP). The study examines the composition, microstructure, and water evaporation performance of the composite membrane under both solar/microwave-driven. The results show that, under microwave conditions with a frequency of 2450 MHz and power of 400 W, the evaporation rate can reach up to 4.13 kg·m−2·h−1, doubling the evaporation rate achieved through solar-driven evaporation at an equivalent efficiency level. Furthermore, the evaporation rate of the composite membrane remains consistent when exposed to high-concentration saltwater of 15 wt%. Notably, the removal rates of Na+, K+, Ca2+, and Mg2+ all exceed 99 %, meeting the drinking water requirements established by the World Health Organization. This study provides a novel approach to seawater desalination utilizing environmentally friendly materials and clean energy sources.

Sandwich-structured electrospun polyvinylidene difluoride sensor for structural health monitoring of glass fiber reinforced polymer composites

Stress monitoring and interlaminar failure detection attract much attention in glass fiber reinforced polymer (GFRP) structural health monitoring area. However, due to limitations of sensing or electrode materials, existing embedding sensors cannot be designed to have both of the abilities without sacrificing mechanical properties. This work fabricated a sandwich-structured sensor, which is composed of three layers of electrospun polyvinylidene difluoride membranes. The upper and lower electrodes are flexible membranes that ensure stable signal collection in the rigid GFRP material system. The sensor can quantitatively monitor the stress based on piezoelectric effect, and interlaminar crack propagation based on parallel plate capacitors. The voltage and capacitance values have a linear relationship with the stress level and crack length (R-square of the functions is 0.999 and 0.933), respectively. Due to the porous microstructure of electrospun membranes, polymer matric can well infiltrate the polyvinylidene difluoride nanofibers while preparing the sensor embedded GFRP. Thus, the perfect bonding of the sensor within GFRP ensures the effective sensing abilities until sample failure and negligible effect (< -7%) on the mechanical properties of GFRP.

Improved purification efficiency and stability of photocatalytic cement-based pavement coated with colloidal graphitic carbon nitride

Photocatalytic coatings applied onto cement-based pavement materials have been intensely developed to purify runoff pollution and vehicle exhaust. However, the masking effect of the adhesive incorporation often results in an unsatisfactory purification efficiency. Thus, developing an adhesive-free photocatalytic coating with high stability and purification efficiency on cement-based pavements is still urgently needed. Herein, a colloidal graphitic carbon nitride (g-C3N4) modified with hydroxyl groups was sprayed onto cement pastes to prepare a photocatalytic coating on the cement-based materials. The results of photocatalytic degradation of Rhodamine B (RhB) indicated that the RhB degradation efficiency and stability of the colloidal g-C3N4-coated cement paste were significantly improved compared to pristine g-C3N4-coated cement paste. After a runoff-washing trial, photocatalytic RhB degradation by colloidal g-C3N4-coated cement paste was 13.8-fold higher than that of pristine g-C3N4-coated cement paste. Mechanistic studies suggested that the well-distributed membrane microstructure of colloidal g-C3N4 and coordinate bonds between colloidal g-C3N4 and calcium-silicate-hydrates were mainly responsible for the improved stability and purification efficiency of colloidal g-C3N4-coated cement pastes. These results support the use of colloidal g-C3N4 as a promising strategy to prepare photocatalytic cement-based pavements with good stability and purification efficiency.

Titania and zirconia ceramic nanofiltration membrane fabrication by coating method on mullite and mullite-alumina microfiltration supports for industrial wastewater treatment

Industrial wastewater treatment increasingly relies on membrane separation, with ceramic membranes offering many advantages such as thermal stability and pH resistance. The resistance of ceramic membranes to extreme pH conditions indicates their ability to maintain structure and performance when exposed to highly acidic or alkaline environments. A high-permeability ceramic nanofiltration membrane was developed, boasting excellent rejection rates through a multilayer asymmetric design. Initially, two tubular porous supports, mullite and mullite-alumina, with a weight percent of 50, were fabricated using the extrusion method. Subsequently, a colloidal sol of titania (TiO2) and titania-zirconia (TiO2- ZrO2) was prepared via the sol–gel method and coated on the ceramic supports using the dip-coating method. After analyzing the membrane microstructure using SEM, XRD, and BET, the efficiency of the membranes in treating synthetic oily wastewater was evaluated. The results underscore the significant impact of the Donnan exclusion mechanism on the rejection of nanofiltration (NF) membranes. An increase in pressure led to a rise in rejection rates up to 7 bars. The Chemical Oxygen Demand (COD) rejection for mullite-titania zirconia (MTZ) and mullite-alumina-titania zirconia (MATZ) membranes was 98.65 % and 98 %, respectively. The pure water permeability test results for mullite and mullite-alumina supports, as well as MTZ and MATZ membranes, were recorded as 254, 382, 70, and 89 L bar-1m-2h−1, respectively.

Mechanistic insights into the separation behaviors of polyamide desalination membranes for emerging micropollutants removal

As emerging micropollutants (EMPs) become a global environmental concern, it is crucial to devise energy-efficient methods that can effectively remove EMPs from water. Polyamide thin-film composite (PA-TFC) membranes are state-of-the-art water separation membranes and their applications for EMPs separations have been increasingly conscripted in recent years. However, a comprehensive fundamental understanding of the underlying relationship between membrane microstructures and EMPs transport across the PA-TFC membranes remains enigmatic. To address this gap, we thoroughly investigated the separation behaviors of two PA-TFC membranes with distinct PA microstructures toward a wide spectrum of EMPs with various dimensions and chemistries. By reconciling experimental evidence and density-functional theory (DFT), we disclosed that the water permeance of the PA-TFC membrane is predominately governed by the effective filtration area associated with surface protuberances and the intrinsic wall thickness of the PA microlayers. Precise control of the solute–PA interactions is explicitly important for membrane selectivity toward EMPs, which deserves more attention in future membrane design besides synchronously regulating membrane pore size and size distribution. This work represents a conspicuous step forward in the fundamental understanding of the structure–performance relationship of PA-TFC membranes for EMPs separations, which would inspire the rational construction and structural regulation of high-performance membranes for new pollutants removal.