Production Of Membranes Research Articles

Molecular Weaving Towards Flexible Covalent Organic Framework Membranes for Efficient Gas Separations.

Covalent organic frameworks (COFs) exhibit considerable potential in gas separations owing to their remarkable stability and tunable pore structures. Nevertheless, their application as gas separation membranes is hindered by limited size-sieving capabilities and poor processability. In this study, we propose a novel molecular weaving strategy that combines hydroxyl polymers and 2D TpPa-SO3H COF nanosheets, achieving high gas separation efficiency. Driven by the strong electrostatic interactions, the hydroxyl chains thread through the COF pores, effectively weaving and assembling the composites to achieve exceptional flexibility and high mechanical strength. The penetrated chains also reduce the effective pore size of COFs, and combined with the "secondary confinement effect" stemming from abundant CO2 sorption sites in the channels, the PVA@TpPa-SO3H membrane demonstrates a remarkable H2 permeance of 1267.3 GPU and an H2/CO2 selectivity of 43, surpassing the 2008 Robson upper bound limit. This facile strategy holds promise for the manufacture of large-area COF-based membranes for small-sized gas separations.

Gravity-Based PVC/PVP/SiO2 Membrane for River Water Treatment

In this study, UF-GDM membranes are made from PVC (12-14% weight), which is mixed with PVP (0-5% weight) and SiO2 (1-3% weight) in a DMAc solvent. The results showed that the PVC/PVP/SiO2 membrane formulation 12/5/1 produced a membrane with the lowest water contact angle of 55° and a permeate flux of 34 L.m-².h-1. However, the membrane is more susceptible to fouling, characterized by a 21% decrease in flux during 5 hours of operation. This is due to the large porosity of the membrane (84%). PVC/PVP/SiO2 formulations 14/2,5/1 showed the highest decrease in contaminants (turbidity above 99.9%, TDS of 47-51%, conductivity of 96%, and organic matter of 97.5%), but low permeate flux (8 L.m-².h-1) due to tighter membrane pores and high flux decrease (20%) due to fouling. The best formulation was obtained in a 12/2,5/1 PVC/PVP/SiO2 composition, with a more stable flux (37 L.m-².h-1) and a decrease of 9% over 5 hours. This formulation also showed a decrease in TDS of 38%, turbidity of 99.9%, conductivity of 96%, and organic substances of 98%. With clear water results, this formulation has the potential to be further developed in the manufacture of membranes for environmentally friendly and energy-efficient clean water supply.

Monolithic Polyepoxide Membranes for Nanofiltration Applications and Sustainable Membrane Manufacture.

The present work details the development of carbon fiber-reinforced epoxy membranes with excellent rejection of small-molecule dyes. It is a proof-of-concept for a more sustainable membrane design incorporating carbon fibers, and their recycling and reuse. 4,4'-methylenebis(cyclohexylamine) (MBCHA) polymerized with either bisphenol-A-diglycidyl ether (BADGE) or tetraphenolethane tetraglycidylether (EPON Resin 1031) in polyethylene glycol (PEG) were used to make monolithic membranes reinforced by nonwoven carbon fibers. Membrane pore sizes were tuned by adjusting the molecular weight of the PEG used in the initial polymerization. Membranes made of BADGE-MBCHA showed rejection of Rose Bengal approaching 100%, while tuning the pore sizes substantially increased the rejection of Methylene Blue from ~65% to nearly 100%. The membrane with the best permselectivity was made of EPON-MBCHA polymerized in PEG 300. It has an average DI flux of 4.48 LMH/bar and an average rejection of 99.6% and 99.8% for Rose Bengal and Methylene Blue dyes, respectively. Degradation in 1.1 M sodium hypochlorite enabled the retrieval of the carbon fiber from the epoxy matrix, suggesting that the monolithic membranes could be recycled to retrieve high-value products rather than downcycled for incineration or used as a lower selectivity membrane. The mechanism for epoxy degradation is hypothesized to be part chemical and part physical due to intense swelling stress leading to erosion that leaves behind undamaged carbon fibers. The retrieved fibers were successfully used to make another membrane exhibiting similar performance to those made with pristine fibers.

Brine separation with polyamide and polyimine thin film composite nanofiltration membranes obtained from biobased monomers

Thin film composite (TFC) membranes are state-of-the-art membranes that are widely applied in water treatment and seawater desalination. However, these membranes are typically prepared using petrochemical-based monomers and toxic solvents. Herein, plant-based monomers, namely priamine (PA), 2,5-furandicarboxaldehyde (FDA) are used to fabricate green PA–FDA TFC membranes via interfacial polymerization. Additionally, PA was also combined with trimesoyl chloride (TMC) to obtain PA–TMC TFC membranes. The reaction conditions were varied to investigate their effects on membrane morphology and performance. The resultant membranes exhibited smooth surfaces with an average roughness ranging from 15 to 30 nm, and increasing the monomer concentration increased the film thickness. The PA–TMC free-standing films had higher thicknesses (130–300 nm) than the PA–FDA films (36–122 nm). Furthermore, PA–TMC and PA–FDA films were hydrophobic due to the long aliphatic chains of PA. Moreover, PA–TMC membranes demonstrated a water permeance of ∼4 L m−2 h−1 bar−1 with 74% NaCl rejection, while PA–FDA membranes achieved better NaCl rejection (∼80%) but lower water permeance (0.3–4 L m−2 h−1 bar−1). Applied in brine separation, the membranes demonstrated ∼90% divalent ion rejection and only 70% monovalent ion rejection. The proposed plant-based monomer combination provides a steppingstone toward green TFC membrane manufacturing for water treatment and desalination applications.

Ultra-hydrophilic MOF-303 on electrospun nanofibers with Burr Puzzles structure for the purification of oily wastewater containing heavy metal ions

The current oil-water separation field is extremely complex and the material system is variable. Therefore, the full process applicability of membrane technology is extremely demanding, both in terms of high oil-water separation efficiency and the treatment of soluble substances in wastewater, such as heavy metal ions. The high demand for membrane performance is accompanied by the complexity of the membrane manufacturing process, resulting in the development of membrane technology being hindered. If we can purify heavy metal ions from wastewater while meeting the conditions of oil-water treatment, and simplify the process flow, it is an innovation that we are happy to see. Herein, the use of a seed pre-embedded growth strategy is taking polyacrylamide (PEI) as a breakthrough point, we take advantage of blending to introduce embedding sites in polyacrylonitrile (PAN) membranes. Uniform growth of MOF-303 with Burr Puzzle structure on membrane surface using in situ hydrothermal growth method. The Burr Puzzles structure on the membrane surface is not only able to effectively deal with nanoscale stabilized oil-water mixture and effectively adsorb heavy metal ions, but also enables the MOF-303 crystals to grow more firmly on the membrane surface, so that the modified membrane still maintains good performance in harsh environments. The separation fluxes of the oil-in-water emulsions were all higher than 6987 L m−2 h−1 for oil-in-water emulsion with a separation efficiency of 98.4 %, and the adsorption efficiency of heavy metal ions was also as high as 98.3 %. After 20 cycles, the membrane maintains its promising performance. Due to its simple preparation process and excellent efficiency of emulsions separation and heavy metal ions separation, simplifies complex membrane processes while meeting the rigors of wastewater treatment. it has great prospects for development in the current complex wastewater treatment process.

Scalable Graphene Oxide Hollow Fiber Membranes for Dye Desalination Enabled by Multi-Purpose Polyamine Functionalization.

2D nanosheets such as graphene oxide (GO) can be stacked to construct membranes with fine-tuned nanochannels to achieve molecular sieving ability. These membranes are often thin to achieve high water permeance, but their fabrication with consistent nanostructures on a large scale presents an enormous challenge. Herein, GO-based hollow fiber membranes (HFMs) are developed for dye desalination by synergistically combining chemical etching to form in-plane nanopores (10-30nm) to increase water permeance and polyamine functionalization to improve underwater stability and enable facile large-scale production using existing membrane manufacturing processes. HFM modules with areas of 88 cm2 and GO layer thicknesses of ≈500nm are fabricated, and they exhibited a stable dye water permeance of 75 L m-2 h-1 bar-1, rejection of >99.5% for Direct red and Congo red, and Na2SO4/dye separation factor of 300-500, superior to state-of-the-art commercial membranes. The versatility of this approach is also demonstrated using different short polyamines and porous substrates. This study reveals a scalable way of designing 2D materials into high-performance robust membranes for practical applications.

Synergistic Enhancement of Mechanical and Electrochemical Properties in Grafted Polymer/Oxide Hybrid Electrolytes.

Lithium metal batteries operated with high voltage cathodes are predestined for the realization of high energy storage systems, where solid polymer electrolytes offer a possibility to improve battery safety. Al2O3_PCL is introduced as promising hybrid electrolyte made from polycaprolactone (PCL) and Al2O3 nanoparticles that can be prepared in a one-pot synthesis as a random mixture of linear PCL and PCL-grafted Al2O3. Upon grafting, synergistic effects of mechanical stability and ionic conductivity are achieved. Due to the mechanical stability, manufacture of PCL-based membranes with a thickness of 50µm is feasible, yielding an ionic conductivity of 5·10-5S cm-1 at 60°C. The membrane exhibits an impressive performance of Li deposition in symmetric Li||Li cells, operating for 1200h at a constant and low overvoltage of 54mV and a current density of 0.2mA cm-2. NMC622|Al2O3_PCL|Li cells are cycled at rates of up to 1 C, achieving 140 cycles at >80% state of health. The straightforward synthesis and opportunity of upscaling as well as solvent-free polymerization render the Al2O3_PCL hybrid material as rather safe, potentially sustainable and affordable alternative to conventional polymer-based electrolytes.

Slot-die coating of vinyl-PDMS composite membranes for alcohol perm-selective pervaporation

The use of pervaporation membranes has shown great potential in the extraction of bioethanol. However, a simple, continuous, and controllable alcohol perm-selective membrane manufacturing process is needed for practical applications. In this study, the slot-die coating technique was utilized to deposit low-viscosity vinyl-polydimethylsiloxane (vinyl-PDMS) and crosslinker onto a porous substrate. A defect-free separation layer could be created within just 20 min, which includes the membrane forming and drying process, due to the rapid hydrosilylation reaction between vinyl-PDMS and the crosslinker. Therefore, the efficient fabrication process is suitable for continuous roll-to-roll industrial production. Additionally, by optimizing the slot-die parameters, the thickness of the separation layer could be regulated from 0.4 to 15 μm. The obtained vinyl-PDMS composite membrane demonstrated a total flux of 2.8 kg m−2 h−1 and a separation factor of 10.3 for 5 wt% ethanol/water mixture at 60 °C.

Ultrafast 2D Nanosheet Assembly via Spontaneous Spreading Phenomenon.

In 2D materials, a key engineering challenge is the mass production of large-area thin films without sacrificing their uniform 2D nature and unique properties. Here, it is demonstrated that a simple fluid phenomenon of water/alcohol solvents can become a sophisticated tool for self-assembly and designing organized structures of 2D nanosheets on a water surface. In situ, surface characterizations show that water/alcohol droplets of 2D nanosheets with cationic surfactants exhibit spontaneous spreading of large uniform monolayers within 10s. Facile transfer of the monolayers onto solid or flexible substrates results in high-quality mono- and multilayer films with high coverages (>95%) and homogeneous electronic/optical properties. This spontaneous spreading is quite general and can be applied to various 2D nanosheets, including metal oxides, graphene oxide, h-BN, MoS2, and transition metal carbides, enabling on-demand smart manufacture of large-size (>4 inchϕ) 2D nanofilms and free-standing membranes.

In Situ Transformation of an Amorphous Supramolecular Coating to a Hydrogen-Bonded Organic Framework Membrane to Trigger Selective Gas Permeation.

We introduce a "solution-processing-transformation" strategy, deploying solvent vapor as scaffolds, to fabricate high-quality hydrogen-bonded organic framework (HOF) membranes. This strategy can overcome the mismatch in processing conditions and crystal growth thermodynamics faced during the facile solution processing of the membrane. The procedure includes the vapor-trigged in situ transformation of dense amorphous supramolecules to crystalline HOF-16, with HOF-11 as the transient state. The mechanism involves a vapor-activated dissolution-precipitation equilibrium shifting and hydrogen bonding-guided molecule rearrangement, elucidated through combined experimental and theoretical analysis. Upon removal of the molecular scaffolds, the resulting HOF-16 membranes showcase significant improvement in hydrogen separation performance over their amorphous counterparts and previously reported HOF membranes. The method's broad applicability is evidenced by successfully extending it to other substrates and HOF structures. This study provides a fundamental understanding of guest-induced ordered supramolecular assembly and paves the way for the advanced manufacture of high-performance HOF membranes for gas separation processes.

Application of Cellulose Acetate Propionate Biopolymer Membrane in The Treatment of Textile Wastewater Containing Remazol Dye

Textile liquid waste is pollution resulted from textile industry activities that often produce hazardous and toxic materials. Therefore, appropriate processing techniques are needed. There are many processing methods that can be used in treating this textile liquid waste, one of which is using membrane technology with phase inversion techniques. Membrane technology has advantages over other processing methods such as, being biopolymeric, relatively lower energy consumption, does not use chemicals in the processing process, and does not cause new waste in the processing process. In this study, 3 variations of cellulose acetate propionate (CAP) concentration were carried out in the manufacture of membranes including, 13% CAP; 14% CAP; and 15% CAP. Membranes that have been made are then carried out several analyses, namely porosity analysis; flux analysis; rejection analysis; and color concentration reduction analysis. The results in this study found that the highest porosity value, rejection value and flux value were found in the CAP membrane with a concentration of 13%. The CAP membrane has the best rejection value on reducing the remazol concentration of 43% with a membrane of 13% CAP.

Investigating the Physical and Operational Characteristics of Manufacturing Processes for MFI-Type Zeolite Membranes for Ethanol/Water Separation via Principal Component Analysis

In this study, Principal Component Analysis (PCA) was applied to discern the underlying trends for 31 distinct MFI (Mobil No. 5)-zeolite membranes of 11 textural, chemical, and operational factors related to manufacturing processes. Initially, a comprehensive PCA approach was employed for the entire dataset, revealing a moderate influence of the first two principal components (PCs), which collectively accounted for around 38% of the variance. Membrane samples exhibited close proximity, which prevented the formation of any clusters. To address this limitation, a subset acquisition strategy was followed, based on the findings of the PCA for the entire dataset. This resulted in an enhanced overall contribution and the revelation of diverse patterns among the membranes and the considered manufacturing factors (total variance between 55% and 77%). The segmentation of the data unveiled a robust correlation between silica (SiO2) concentration and pervaporation conditions. Additionally, a notable clustering of the chemical compositions of the preparation solutions underscored their significant influence on the operational efficacy of MFI zeolite membranes. On the other hand, an exclusive chemical composition of the preparation solution was noticed. This highlighted the high influence of the chemical composition on the operational efficiency of MFI zeolite membranes. The coupling of PCA with experimental results can provide a data-driven enhancement strategy for the manufacturing of MFI-type zeolite membranes used for ethanol/water separation.

Nanostructural modulation of chitosan matrix for facilitating transport of organic molecules across the membrane by pervaporation

Chitosan, as the second most abundant biopolymer on earth, is constantly increasing attention from different fileds such as biomedicals, food, energy, and the environment. However, its application in membrane technology such as pervaporation is lacking of an effective membrane manufacture strategy to improve its separation efficiency. Herein, we use a chitosan-based membrane subjected to neutralization and crosslinking procedures in contrasting solvents—specifically, water and ethanol—to explore the impact of polymer-solvent interactions on the effective nanogaps between polymer nanofibers. Under identical conditions, the procedures conducted in water yield hydrated membranes, while those in ethanol resulted in anhydrous membranes. In hydrated membranes, strong hydrogen bonds formed between water and amine groups block nanogaps amongst polymer nanofibers, significantly impeding molecular transport. Conversely, the absence of such strong hydrogen bonds in anhydrous membrane avoided this effect. This study highlights the potential of controlling the transport of organic molecules by tuning the nanogaps within the membrane matrix. This was achieved through a novel strategy involving washing the chitosan-based membranes with pure ethanol to remove free acids, followed by direct crosslinking in a glutaraldehyde ethanol solution. This strategy was able to double the membrane selectivity despite a 25 % reduction in methanol permeance.

A Janus, robust, biodegradable bacterial cellulose/Ti3C2Tx MXene bilayer membranes for guided bone regeneration

Guided bone regeneration (GBR) stands as an essential modality for craniomaxillofacial bone defect repair, yet challenges like mechanical weakness, inappropriate degradability, limited bioactivity, and intricate manufacturing of GBR membranes hindered the clinical efficacy. Herein, we developed a Janus bacterial cellulose(BC)/MXene membrane through a facile vacuum filtration and etching strategy. This Janus membrane displayed an asymmetric bilayer structure with interfacial compatibility, where the dense layer impeded cell invasion and the porous layer maintained stable space for osteogenesis. Incorporating BC with Ti3C2Tx MXene significantly enhanced the mechanical robustness and flexibility of the material, enabling clinical operability and lasting GBR membrane supports. It also contributed to a suitable biodegradation rate, which aligned with the long-term bone repair period. After demonstrating the desirable biocompatibility, barrier role, and osteogenic capability in vitro, the membrane's regenerative potential was also confirmed in a rat cranial defect model. The excellent bone repair performance could be attributed to the osteogenic capability of MXene nanosheets, the morphological cues of the porous layer, as well as the long-lasting, stable regeneration space provided by the GBR membrane. Thus, our work presented a facile, robust, long-lasting, and biodegradable BC/MXene GBR membrane, offering a practical solution to craniomaxillofacial bone defect repair.

Engineered Cell Membrane-Coated Nanoparticles: New Strategies in Glioma Targeted Therapy and Immune Modulation.

Gliomas, the most prevalent primary brain tumors, pose considerable challenges due to their heterogeneity, intricate tumor microenvironment (TME), and blood-brain barrier (BBB), which restrict the effectiveness of traditional treatments like surgery and chemotherapy. This review provides an overview of engineered cell membrane technologies in glioma therapy, with a specific emphasis on targeted drug delivery and modulation of the immune microenvironment. This study investigates the progress in engineered cell membranes, encompassing physical, chemical, and genetic alterations, to improve drug delivery across the BBB and effectively target gliomas. The examination focuses on the interaction of engineered cell membrane-coated nanoparticles (ECM-NPs) with the TME in gliomas, emphasizing their potential to modulate glioma cell behavior and TME to enhance therapeutic efficacy. The review further explores the involvement of ECM-NPs in immunomodulation techniques, highlighting their impact on immune reactions. While facing obstacles related to membrane stability and manufacturing scalability, the review outlines forthcoming research directions focused on enhancing membrane performance. This review underscores the promise of ECM-NPs in surpassing conventional therapeutic constraints, proposing novel approaches for efficacious glioma treatment.

Recent Advances in Water Treatment Membranes Based on Nanomaterials (A Review)

Nanomaterials have emerged as the next generation of materials for high-performance water treatment membranes, with the ability to address the global problem of pollution in water. Application of nanoparticles as membranes improves permeability feature for water, mechanical performance, efficiency of separation, and membrane fouling. As a result, the nanomaterials open up a new avenue for effectively selective membranes for purification of the water. This paper discusses the enhancements in membrane caused by the presence of various nanomaterials, such as nanoparticles (NPs), two-dimensional nano-materials (2D), nanofibers, nanosheets, and other nano-composite structure materials. Furthermore, the many uses of these membranes-based nanoparticles in treatment of water applications are emphasized. The goal is to show how important nanoparticles are in the membrane manufacturing in treatment of water. Nanomaterials and nanotechnology were discovered to have enormous promise for the progress of sustainable treatment of water and its wastes.

Hairy quaternary ammonium-functionalized metal organic framework integrated in polyacrylonitrile nanofiber membrane for efficient removal of arsenate

In this work, the metal–organic framework (MOF) particles (i.e., UiO-66-NH2) was covalently modified with poly(4-vinylpyridine) (P4VP) through surface-initiated atom transfer radical polymerization (SI-ATRP) method. The hair MOF product, referred to as UiO-66-g-P4VP, was then subjected to quaternization with 1-bromoethane, resulting in UiO-66-g-qP4VP (quaternized P4VP is denoted as qP4VP). Finally, these UiO-66-g-qP4VP particles were incorporated into a polymer matrix made of polyacrylonitrile (PAN) to develop a nanofibrous composite membrane using the electrospinning technique. After modification of quaternized P4VP, the surface of the MOFs carry strong positive charges. Therefore, the electrospun UiO-66-g-qP4VP/PAN nanofiber membrane can serve as an adsorbent in efficient removal of negatively charged arsenate through strong electrostatic interactions. The adsorptive efficacy of the nanofiber membrane exhibited considerable stability within the pH spectrum extending from 4 to 10, indicating that the membrane could potentially maintain its functionality across a broad range of pH conditions. Our developed approach opens up an avenue for manufacturing of polyelectrolyte-functionalized MOF nanofiber membranes, which hold great promise for application in water remediation.

Predicting the wicking rate of nitrocellulose membranes from recipe data: a case study using ANN at a membrane manufacturing in South Korea

Lateral flow assays have been widely used for detecting coronavirus disease 2019 (COVID-19). A lateral flow assay consists of a Nitrocellulose (NC) membrane, which must have a specific lateral flow rate for the proteins to react. The wicking rate is conventionally used as a method to assess the lateral flow in membranes. We used multiple regression and artificial neural networks (ANN) to predict the wicking rate of NC membranes based on membrane recipe data. The developed ANN predicted the wicking rate with a mean square error of 0.059, whereas the multiple regression had a square error of 0.503. This research also highlighted the significant impact of the water content on the wicking rate through images obtained from scanning electron microscopy. The findings of this research can cut down the research and development costs of novel NC membranes with a specific wicking rate significantly, as the algorithm can predict the wicking rate based on the membrane recipe.Graphical abstractCorrelation matrix displaying the distribution of the variables and linear correlations

A perspective on cellulose dissolution with deep eutectic solvents

Currently, membrane manufacturing relies heavily on fossil-based solvents and polymers, resulting in significant negative impacts on human health and the environment. Thus, there is an urgent need for eco-friendly, low-toxicity, and sustainable solvents and polymers to comply with the United Nations’ sustainable development goals. Cellulose, as a green, natural, and abundant polymer, offers a sustainable source for membrane manufacturing. However, a significant challenge exists in dissolving cellulose due to strong intermolecular and intramolecular hydrogen bonds within cellulose molecules. Deep eutectic solvents (DESs), which contain both hydrogen bond donor and acceptor groups, have received significant attention as alternative solvents for cellulose dissolution owing to their low cost, low toxicity, environmentally friendly nature, ease of synthesis, and versatility. This review examines experimental studies, and theoretical approaches, highlighting key findings and factors influencing cellulose dissolution in deep eutectic solvents.

Roll-to-Roll Manufacturing of Breathable Superhydrophobic Membranes.

Self-cleaning and anti-biofouling are both advantages for lotus-leaf-like superhydrophobic surfaces. Methods for creating superhydrophobicity, including chemical bonding low surface energy molecular fragments and constructing surface morphology with protrusions, micropores, and trapped micro airbags by traditional physical strategies, unfortunately, have encountered challenges. They often involve complex synthesis processes, stubborn chemical accumulation, brutal degradation, or infeasible calculation and imprecise modulation in fabricating hierarchical surface roughness. Here, a scalable method to prepare high-quality, breathable superhydrophobic membranes is proposed by developing a successive roll-to-roll laser manufacturing technique, which offers advantages over conventional fabrication approaches in enabling automatically large-scale production and ensuring cost-effectiveness. Nanosecond laser writing and femtosecond laser drilling produce surface microstructures and micropore arrays, respectively, endowing the membrane with superior antiwater capability with hierarchical microstructures forming a barrier and blocking water infiltration. The membrane's breathability is carefully optimized by tailoring micropore arrays to allow for the adequate passage of water vapor while maintaining superhydrophobicity. These membranes combine the benefits of anti-aqueous corrosive liquid behaviors, photothermal effects, thermoplastic properties, and stretchable performances as promising comprehensive materials in diverse scenes.