Membrane Material Research Articles

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.

Broadband efficient light-absorbing SS-PPy@CNT membranes prepared by electrochemical deposition for photothermal conversion

Solar energy is an eco-conscious substitute, for solar energy absorption and subsequent light-to-heat conversion, light-absorbing materials require broad-spectrum light absorption capabilities. Herein, we present the fabrication of broadband light-absorbing polypyrrole-carboxylated carbon nanotube membranes via a facile electrochemical deposition route. By manipulating electrochemical deposition time, the structure of the membranes was tailored, resulting in enhanced absorption, achieving over 98.95 % across the entire solar spectrum. The membranes demonstrated exemplary thermal efficacy and insensitivity to incident angles in photothermal conversion, the membranes facilitated a notable 12 °C temperature elevation within a simulated greenhouse compared to ambient conditions. Thus, these membranes exhibit considerable potential for widespread application in photothermal conversion and greenhouse technology.

Novel polyethylene glycol methyl ether substituted polysiloxane membrane materials with high CO2 permeability and selectivity

Membrane gas separation is a promising technology for CO2 capture. However, one of the key challenges is the development of stable-in-time and highly permeable materials with increased CO2 permselectivity. In this study, two series of novel polysiloxanes with linear (methyl oligoethyleneglycol allyl ether (PEG8)) and branched (vinyl-bis- [methyltriethyleneglycol] (B-PEG4)) oxygen-containing side substituents were synthesized. By crosslinking PEG-substituted polymethylsiloxanes with polydimethylsiloxane (PDMS), a series of CO2-highly selective membrane materials with a PDMS content of 6.5–50 wt% was obtained for the first time. The effect of the side chain geometry on the sorption and transport properties of these membranes for different gases (N2, O2, CO2, CH4, C2H6) was evaluated. The specific interactions between the PEG substituents and CO2 that contribute to the enhanced selectivity of these materials were identified. The introduction of both linear and branched PEG substituents leads to in an increase in the selectivity of diffusion, solubility, and CO2/gas permeability, compared to PDMS.The CO2/N2 and CO2/CH4 permselectivities and diffusion selectivities are increases, as well as the permeability coefficients of the membrane materials for all gases are decreases, as the PDMS content reduces from 50 % to 6.5 % wt. Within the PDMS concentrations range between 6.5 and 12.5 % wt., there was a sharp increase in diffusion and permeability coefficients of membrane materials. For this polysiloxanes with linear PEG substituents, an unexpectedly high diffusion selectivity for CO2 was observed. Such value determined the maximum CO2 permselectivity among the polysiloxanes studied. The most promising membrane material from these series was identified as PEG8-substituted polysiloxane with 12.5 wt% PDMS. It has a CO2 permeability coefficient of 1300 Barrer, CO2/N2 selectivity of 37 and CO2/CH4 selectivity of 10.

Preprocessed Monomer Interfacial Polymerization for Scalable Fabrication of High-Valent Cluster-Based Metal-Organic Framework Membranes.

Current research on emergent membrane materials with ordered and stable nanoporous structures often overlooks the vital facet of manufacturing scalability. We propose the preprocessed monomer interfacial polymerization (PMIP) strategy for the scalable fabrication of high-valent cluster-based metal-organic framework (MOF) membranes with robust structures. Using a roll-to-roll device on commercial polymer supports, Zr-fum-MOF membranes are continuously processed at room temperature through the PMIP approach. These large-area membranes demonstrate the preeminent hydrogen separation capabilities, boasting an order of magnitude of permeance and a thrice-enhanced selectivity when juxtaposed with conventional polymeric membranes. The obtained PMIP-Zr-fum-MOF membranes possess superior stability in water compared with interfacial polymerization (IP)-processed low-valent metal-ion-based ZIF-8 membranes. Moreover, we have implemented the PMIP strategy's universality to process the other four diverse MOF membranes. The proposal of PMIP significantly advances the scalable fabrication of water-stable high-valent cluster MOF membranes.

Sustainable Water Purification Techniques: A Review Of Solar-Based Desalination Methods

Global water scarcity continues to pose a critical challenge, driving the need for sustainable water purification solutions. Solar desalination has emerged as a promising approach due to its reliance on renewable solar energy and minimal environmental impact. This study systematically reviews and synthesizes findings from a comprehensive set of 100 peer-reviewed articles to evaluate advancements in solar desalination technologies, including solar stills, photovoltaic-powered reverse osmosis (PV-RO) systems, hybrid solar desalination, and the application of nanotechnology. The review highlights significant progress in improving the efficiency, scalability, and cost-effectiveness of these systems, particularly through innovations such as multi-stage designs, advanced membrane materials, energy recovery devices, and the integration of phase change materials (PCMs) for thermal storage. Additionally, the incorporation of nanomaterials has proven effective in enhancing thermal conductivity and reducing fouling, thereby optimizing water output and system longevity. Findings also reveal the substantial environmental benefits of solar desalination, which can reduce the carbon footprint of water production by up to 70%, aligning with the United Nations Sustainable Development Goals (SDGs) related to clean water access and climate action. However, challenges remain, particularly concerning the initial capital costs and the need for further technological advancements to achieve widespread adoption. This review underscores the critical role of continued research, innovation, and supportive policies in scaling solar desalination technologies as a sustainable solution to global water scarcity.

Evaluation of the impact of hollow fiber pore size and membrane material on virus concentration using a handheld hollow fiber method.

Virus concentration using hollow fibers is widely used for vaccine production to maintain viral infectivity with low shear stress and to allow for easier scale-up of production. However, research laboratories often have limited available viral materials at the early stage of vaccine development, making it difficult to find an optimal hollow-fiber. In addition, few research articles have reported on optimizing hollow fiber pore size and membrane structure for virus concentration. In this study, the previously established handheld hollow fiber virus concentration method was modified to reduce the sample volume required and to enable simple and easy hollow fiber screening. The handheld hollow fiber screening method for virus concentration was confirmed to be effective using Zika as a model virus.

Constructing polyolefin-based lithium-ion battery separators membrane for energy storage and conversion

Owing to the escalating demand for environmentally friendly commodities, lithium-ion batteries (LIBs) are gaining extensive recognition as a viable means of energy storage and conversion. LIBs comprise cathode and anode electrodes, electrolytes, and separators. Notably, the separator, a crucial and indispensable element in LIBs that mainly comprises a porous membrane material, necessitates substantial research focus. Scholars have consequently strived to devise novel systems that augment separator efficiency, bolster safety measures, and surmount existing constraints. This review endeavors to equip researchers with comprehensive information on polyolefin-based separator membranes, encompassing performance prerequisites, functional attributes, scientific advancements, and so on. Specifically, it scrutinizes the latest innovations in porous membrane configuration, fabrication, and enhancement that utilize the most prevalent polyolefin materials today. Consequently, robust and enduring membranes fabricated have demonstrated superior effectiveness across diverse applications, facilitating a circular economy that curbs waste materials, reduces operational expenses, and mitigates environmental impact.

Supramolecular Interfacial Assembly: Integrating Supramolecular Hosts into Polymeric Membranes through an Aqueous Interface

AbstractEfficient incorporation of macrocycles in polymeric membranes can impart the overall matrix with new properties for a range of cutting‐edge applications. Here, we introduce a Supramolecular Interfacial Assembly (SIA) method for the fabrication of polymeric membranes featuring embedded macrocycles. Through harnessing the quasi‐liquid nature of the concentrated polymer solution, SIA orchestrates the homogeneous spreading of macrocycles in an aqueous layer on its surface, leading to the creation of an interface between “water/water” phases, subsequently forming a cross‐linked membrane driven by supramolecular electrostatic interactions. Remarkably, compared to the traditional interfacial polymerization, SIA adheres to a “green” paradigm without the need for organic solvents. The resultant composite membrane exhibits superior performance in organic solvent nanofiltration (OSN), owing to the precise molecular sieving property provided by the macrocycles with well‐defined permanent cavities. This fabrication method holds great promise for the innovative design and production of composite membranes that seamlessly integrates macrocycles with conventional polymers, which can greatly impact the design and preparation of advanced membrane materials in the future.

Supramolecular Interfacial Assembly: Integrating Supramolecular Hosts into Polymeric Membranes through an Aqueous Interface.

Efficient incorporation of macrocycles in polymeric membranes can impart the overall matrix with new properties for a range of cutting-edge applications. Here, we introduce a Supramolecular Interfacial Assembly (SIA) method for the fabrication of polymeric membranes featuring embedded macrocycles. Through harnessing the quasi-liquid nature of the concentrated polymer solution, SIA orchestrates the homogeneous spreading of macrocycles in an aqueous layer on its surface, leading to the creation of an interface between "water/water" phases, subsequently forming a cross-linked membrane driven by supramolecular electrostatic interactions. Remarkably, compared to the traditional interfacial polymerization, SIA adheres to a "green" paradigm without the need for organic solvents. The resultant composite membrane exhibits superior performance in organic solvent nanofiltration (OSN), owing to the precise molecular sieving property provided by the macrocycles with well-defined permanent cavities. This fabrication method holds great promise for the innovative design and production of composite membranes that seamlessly integrates macrocycles with conventional polymers, which can greatly impact the design and preparation of advanced membrane materials in the future.

Study on preparation of a pizza-like attapulgite-based composite membrane and its performance on methylene blue and ciprofloxacin removal

In this study, attapulgite (ATP) was made to unfolded in two-dimension on the surface of graphene oxide (GO) and metal oxides were loaded on it as active substances to prepare a multifunctional membrane material (Fe-Cu/ATP-GO) through an innovative pizza-like preparation method. The fabrication process of this composite membrane has undergone rigorous optimization to ensure optimal performance. In order to get insights into its structural and compositional features, the composite membrane was thoroughly investigated by XRD, FTIR, SEM, BET analysis, XPS, and TG, which showed ATP was uniformly dispersed on the surface of GO membrane and both Fe and Cu were successfully and uniformly loaded on the surface of ATP-GO membrane. The application of the Fe-Cu/ATP-GO membrane in treating wastewater contaminated with methylene blue (MB) or ciprofloxacin (CIP) showed over 90 % removal ratio of MB and over 70 % removal ratio of CIP after 10 min dynamic treatment experiments under optimal conditions, revealed its exceptional ability to effectively eliminate organic contaminants from water. Further mechanistic studies have shed light on the multifaceted treatment mechanisms employed by the composite membrane, including filtration, adsorption, and catalytic oxidation, etc. These mechanisms synergistically contribute to the membrane’s remarkable performance in removing refractory organics from water.

Influence of cyclic loading on physical and mechanical properties of thin-film membrane structures

The principle of modification of mechanical properties of thin-film membrane structures of arbitrary shape by non-contact method was proposed, realized and explained for the first time. The idea was tested on an aluminum thin-film membrane formed by magnetron method on a silicon substrate. The external influence was realized by means of cyclic loading in the form of discharge and supply of excess air pressure to the membrane. As a result of repeated impacts, physical properties of materials (grain size and roughness) and mechanical properties (internal mechanical stresses and critical overpressure) are changed. Changing the magnitude of residual mechanical stresses in the membrane material allows the formation of a surface with a desired curvature value. In this work, after cyclic loading with pressure equal to half of the critical pressure, the following effects were revealed: the deflection of the membrane in the absence of external influence increased by more than an order of magnitude, the structure shifted to the plastic type of deformation, the critical rupture pressure decreased by several tens of percent. Application of this methodology allows to create new materials with unique mechanical properties.

High detail resolution cellulose structures through electroprinting

Electrospinning is a technique used to fabricate polymer fibers in micro- and nanoscales. Due to the large distance between the nozzle and collector, there is a limited positioning accuracy of electrospun fibers. To enhance the possibility of fabricating structures with micrometer placement, an electroprinting technique has been developed. By reducing the distance between the nozzle and the collector it is demonstrated that it is possible to get an improved control over fiber positioning which gives a possibility to fabricate designed 3D structures at the micron scale. In this study, cellulose acetate (CA) has been selected as a biomaterial to advance the 3D printing of membranes with possible use in separation applications. Various parameters, such as CA concentration and molecular weight, printing speed, printing pattern, applied voltage, etc. are evaluated with respect to printing control. Results indicate that by optimizing the printing parameters it is possible to print structures with inter- fiber distances down to 3 µm and fiber diameters at a sub-µm scale. This electroprinting development is promising for the fabrication of customized separation membranes. However, printing speed still remains a challenge.

Achieving antibiofouling on microporous membranes prepared with a green solvent via spraying an aqueous antifouling copolymer solution

This study highlights a comprehensive investigation into the fabrication and characterization of sustainable membranes for antifouling applications. It utilizes γ-valerolactone as a green solvent to obtain microfiltration polyvinylidene difluoride (PVDF) membranes, and leverages spray-coating technique to modify these membranes. This research aims to enhance the surface and bulk properties of PVDF membranes while promoting sustainable practices. Chemical analyses of the membranes reveal that the surface and bulk of the membranes were successfully modified. Dynamic water contact angle measurements indicated that a 10 mg/mL coating solution (PVDF_10) resulted in the highest hydrophilicity. Different biofouling tests were conducted using proteins and bacteria. In adhesion tests with BSA, and E. coli, the PVDF_10 membrane demonstrated the highest resistance, reducing adhesion by approximately 83 % and 94 %, respectively. Additionally, cyclical water/bacterial filtration tests demonstrated that PVDF_10 membrane achieved a higher flux recovery ratio compared to commercial hydrophilic PVDF membranes. The modification remained stable even after 6 weeks of immersion in water. This study highlights the potential of γ-GVL and the spray-coating technique as environmentally friendly solvents and modification techniques for producing green antifouling PVDF membranes, aligning with sustainable practices and significantly enhancing membrane performance.

A Numerical Study of Dynamic Behaviors of Graphene-Platelet-Reinforced ETFE Tensile Membrane Structures Subjected to Harmonic Excitation

This study presents a numerical investigation of the dynamic behavior of graphene platelet (GPL)-reinforced ethylene tetrafluoroethylene (ETFE) tensile membrane structures subjected to harmonic excitation. Modal and harmonic response analyses were performed to assess both the natural frequencies and the dynamic responses of the ETFE membrane. GPLs were employed as the reinforcements to enhance the mechanical properties of the membrane materials, whose Young’s modulus was predicted through the effective medium theory (EMT). Parametric studies were conducted to examine the impact of pre-strain and the attributes of the GPL reinforcements, including weight fraction and aspect ratio, on the natural frequencies and amplitude–frequency response curves of the membrane structure. The first natural frequency substantially increased from 5.46 Hz without initial strain to 31.0 Hz with the application of 0.1% initial strain, resulting in a frequency shift that moved the natural frequency out of the range of typical wind-induced pulsations. Embedding GPL fillers into ETFE membrane was another potential solution to enhance the dynamic stability of the membrane structure, with a 1% addition of GPLs resulting in a 48.6% increase in the natural frequency and a 45.1% reduction in resonance amplitude. GPLs with larger aspect ratios provided better reinforcement, offering a means to fine-tune the membrane’s dynamic response. These results underscore that by strategically adjusting both pre-strain levels and GPL characteristics, the membrane’s dynamic behavior can be optimized, offering a promising approach for improving the stability of structures subjected to wind-induced loads.

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.

Recycling of puffed polystyrene beads waste as a low‐cost antifouling ultrafiltration membrane for water purification

AbstractCurrently, plastic waste, limited water resources, and water contamination are challenges of universal concerns. Recycling plastic waste as a membrane for water/wastewater treatment is of great significance from the perspective of environmental protection and safe drinking water supply. In this study, we used for the first time the puffed polystyrene beads waste (PPSBW) as a basic material for the fabrication of an ultrafiltration membrane and Pluronic F127 (PF127) as a plasticizer and hydrophilizing agent. Different ratios of PF127 were added to the casting solution, and the characteristics of the blank PPSBW and PF127‐modified membranes (PPSBW‐PF127) were evaluated in detail. The addition of PF127 increased the turbidity and viscosity of the casting solution, decreased the contact angle (increased the hydrophilicity), decreased the pure water flux, and increased the rejection of humic acid. The PPSBW membrane with 3 wt.% of PF127 showed the highest antifouling properties, the highest cleaning efficiency, and kept a satisfactory BSA and pure water flux for 4 runs. Overall, PF127 improved the hydrophilicity, organic matter separation, and enhanced the antifouling properties of the PPSBW‐derived membrane.Highlights Renew flow: Repurposing plastic waste as a UF membrane was successfully achieved. The PPSBW‐PF127 membrane was applied for wastewater treatment. Mechanical properties showed reasonable response by adding Pluronic F127. The PPSBW‐PF127 membrane demonstrated a significant rejection and permeability. The PPSBW‐PF127 membrane showed the highest antifouling and cleaning properties.

Fabrication and Characterization of UiO66-NH2 Blended PVC Membranes to Enhance Mazut Removal from Aqueous Solution

Fabrication and Characterization of UiO66-NH2 Blended PVC Membranes to Enhance Mazut Removal from Aqueous Solution

Combined Effects of Surface Roughness, Solubility Parameters, and Hydrophilicity on Biofouling of Reverse Osmosis Membranes.

The fouling of protein on the surface of reverse osmosis (RO) membranes is a surface phenomenon strongly dependent on the physical and chemical characteristics of both the membrane surface and the foulant molecule. Much of the focus on fouling mitigation is on the synthesis of more hydrophilic membrane materials. However, hydrophilicity is only one of several factors affecting foulant attachment. A more systematic and rationalized methodology is needed to screen the membrane materials for the synthesis of fouling-resistant materials, which will ensure the prevention of the accumulation of foulants on the membrane surfaces, avoiding the trial and error methodology used in most membrane synthesis in the literature. If a clear correlation is found between various membrane surface properties, in combination or singly, and the amount of fouling, this will facilitate the establishment of a systematic strategy of screening materials and enhance the selection of membrane materials and therefore will reflect on the efficiency of the membrane process. In this work, eight commercial reverse osmosis membranes were tested for bovine serum albumin (BSA) protein fouling. The work here focused on three surface membrane properties: the surface roughness, the water contact angle (hydrophilicity), and finally the Hansen solubility parameter (HSP) distance between the foulant understudy (BSA protein) and the membrane surface. The HSP distance was investigated as it represented the affinities of materials to each other, and therefore, it was believed to have an important contribution to the tendency of foulant to stick to the surface of the membrane. The results showed that the surface roughness and the HSP distance contributed to membrane fouling more than the hydrophilicity. We recommend taking into account the HSP distance between the membrane material and foulants when selecting membrane materials.

Recent Advances in High-Performance Membrane Materials for Fuel Cells

Fuel cells have emerged as a key technology for clean energy production, with proton exchange membrane (PEM) fuel cells being one of the most promising types due to their high efficiency and low emissions. A critical component of PEM fuel cells is the membrane, which plays a crucial role in ion transport and overall system performance. Recent advances in membrane materials have focused on improving proton conductivity, chemical stability, and durability while reducing production costs. This review discusses recent developments in high-performance membrane materials, including polymer blends, hybrid membranes, and metal-organic frameworks (MOFs). These innovative materials have shown significant potential in overcoming the limitations of traditional membranes like Nafion®. Advances in acid-base membranes, such as polybenzimidazole (PBI)-based systems, have demonstrated improvements in high-temperature performance. Enhanced cross-linking techniques, the use of antioxidant additives, and nanofillers have further contributed to improved membrane durability. Despite these advancements, challenges remain in scaling up production and reducing costs. Future research must focus on addressing these issues to enable the widespread commercial use of fuel cells. The progress in membrane material technology is critical to realizing the potential of fuel cells as a viable solution for sustainable energy.

Fabrication of COF-LZU1/PVDF composite loose nanofiltration membranes through oligomer-triggered interfacial polymerization (OT-IP) for highly efficient dye/salt separation

Covalent organic frameworks (COFs) have advantages such as easy functionalization, abundant regular pores, low density, and are widely used in the preparation of membrane materials. In this study, the well-grown COF-LZU1 (LZU for Lanzhou University)/polyvinylidene fluoride (PVDF) loose nanofiltration (NF) composite membranes were prepared through oligomer-triggered interfacial polymerization (OT-IP) at room temperature. Due to its pore size of 1.72 nm, the prepared COF-LZU1/PVDF membrane not only exhibited an ultra-high rejection for dyes (99.4 % for Methyl blue, 99.7 % for Congo red, and 99.1 % for Eriochrome black T). In addition, the filtration experiment of the mixed CR/NaCl solution showed a dye/salt selectivity factor of 328.7, as well as a permeance of 77.0 L·m−2·h−1·bar−1 and a high pure water permeability of 112.3 L·m−2·h−1·bar−1. A continuous filtration experiment showed that the COF-LZU1/PVDF membrane exhibited excellent operational stability. The findings suggest that COF-LZU1/PVDF membrane show promise for use in separating dyes and salts.