Membrane Material Research Articles

Three-Dimensional Reconstruction-Characterization of Polymeric Membranes: A Review.

Polymeric membranes serve as vital separation materials in diverse energy and environmental applications. A comprehensive understanding of three-dimensional (3D) structures of membranes is critical to performance evaluation and future design. Such quantitative 3D structural information is beyond the limit of most employed conventional two-dimentional characterization techniques such as scanning electron microscopy. In this review, we summarize eight types of 3D reconstruction-characterization techniques for membrane materials. Originated from life and materials science, these techniques have been optimized to reveal the 3D structures of membrane materials in the separation field. We systematically introduce the theories of each technique, summarize the sample preparation procedures developed for membrane materials, and demonstrate step-by-step data processing, including 3D model reconstruction and subsequent characterization. Representative case studies are introduced to show the progress of this field and how technical challenges have been overcome over the years. In the end, we share our perspectives and believe that this review can serve as a useful reference for 3D reconstruction-characterization techniques developed for membrane materials.

Effect of Carbon Nanomaterials Incorporated Polymeric Membrane Separators for Energy Storage Devices.

The rapid expansion of the global population and technological advancements have heightened the need for efficient energy conversion and electrochemical energy storage. Electrochemical energy systems like batteries and supercapacitors have seen notable development to meet this demand. However, conventional polymeric membrane separators in these systems face challenges due to limited porosity and poor mechanical and thermal properties, reducing overall electrochemical performance. Researchers have incorporated nanoparticles into the polymer matrix to address these limitations and enhance separator properties. Carbon-based nanomaterials, in particular, have gained prominence due to their unique features, such as surface-dependent characteristics, size, porosity, morphology, and electrical conductivity. These properties make carbon-based nanomaterials advantageous in improving energy storage compared to conventional materials. Advanced carbon-doped polymeric membrane separators have emerged as a potential solution to the issues faced by conventional separators. Adding carbon nanoparticles, such as graphene-based materials and carbon nanotubes to the polymeric separators of batteries and supercapacitors has helped researchers solve problems and improve the electrochemical performance. This review article provides a state-of-the-art overview of carbon-doped polymeric membrane separators, their properties, fabrication processes, and performance in lithium batteries, as well as supercapacitors. It emphasizes advantages of these novel separator materials and suggests future research directions in this field.

Morphology and properties of hollow fiber membrane prepared under different air gap lengths

The fabrication of hollow fibre membrane modules is affected by many spinning variables, including polymer composition, bath temperature, bore fluid ratio, fibre take-up velocity, and air gap length, resulting in varying properties. This study uses a dry-jet wet-spinning process to investigate the morphology and characteristics of PVDF hollow fibre membranes prepared at 10 cm (P10) and 20 cm (P20) air gap lengths. Polypropylene glycol was used as an additive. The dope extrusion rate, coagulation bath temperature, bore fluid ratio, and take-up velocity were set at 4 rpm, 30°C, 1.5 ml/hr, and 2 m/min, respectively. Atomic force microscopy determined the pore size distribution, roughness, and membrane thickness. Field emission scanning electron microscope (FESEM) analyzed membrane morphology. Membrane performance was tested using 10 mg/L of synthetic protein solution. The results showed that the diameters of the fibers as well as the inner and outer lumens were significantly influenced by the air gap. Membrane dimensions decreased with the increased air gap distance with the outer and inner diameter by 5% at a 10 cm air gap. FESEM images verified that the thickness of the skin layer increases with the increase in air gap distance. The resulting roughness of the membrane layer was found to be dependent on the pore size of the support layer. The protein separation test achieved the best rejection of 98 % using the P20 membrane. Thus, selecting an optimum air gap distance for hollow fibre membrane fabrication was discovered to be a viable strategy for improving separation performance in membrane filtration and improving solute separation in wastewater.

Use of Membrane Techniques for Removal and Recovery of Nutrients from Liquid Fraction of Anaerobic Digestate

This review focuses on the use of membrane techniques to recover nutrients from the liquid fraction of digestate (LFD) and emphasizes their role in promoting the principles of the circular economy. A range of membrane separation processes are examined, including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), membrane distillation (MD) and new tools and techniques such as membrane contactors (MCs) with gas-permeable membranes (GPMs) and electrodialysis (ED). Key aspects that are analyzed include the nutrient concentration efficiency, integration with biological processes and strategies to mitigate challenges such as fouling, high energy requirements and scalability. In addition, innovative hybrid systems and pretreatment techniques are examined for their potential to improve the recovery rates and sustainability. The review also addresses the economic and technical barriers to the full-scale application of these technologies and identifies future research directions, such as improving the membrane materials and reducing the energy consumption. The comprehensive assessment of these processes highlights their contribution to sustainable nutrient management and bio-based fertilizer production.

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.

Convenient preparation of inexpensive sandwich-type poly(vinylidene fluoride)/molecular sieve/ethyl cellulose mixed matrix membranes and their effective pre-exploration for the selective separation of CO2 in large-scale industrial utilization

Due to its high methane content, biogas is considered a potential replacement for natural gas as a clean and renewable energy source for future large-scale applications. In addition to CH4 (50–80%), biogas also includes CO2 (20–40%), N2 (0–5%), and other gases. Efficient capture and separation of CO2 not only enhances the calorific value of biogas but also aids in reducing greenhouse gas emissions. Utilizing membrane separation technology is an effective method for separating and capturing CO2 and N2. This technology is renowned for its controllability and efficiency. Here, a variety of ternary mixed matrix membranes consisting of poly(vinylidene fluoride)/molecular sieve/ethyl cellulose were successfully prepared using a simple layer-by-layer coating process. Among them, the porous polyvinylidene difluoride (PVDF) membrane serves as the bottom support layer, the molecular sieve (Titanate molecular sieve (TS-1) and Zeolite Socony Mobil-5 (ZSM-5)) acts as the middle selective layer, and ethyl cellulose (EC) forms the top fixed layer. These membrane materials were used in an attempt to efficiently separate CO2 from a CO2/CH4 gas mixture with a 1:1 ratio and a CO2/N2 gas mixture with a 1:1 ratio. It is encouraging to note that the PVDF/ZSM-5/EC mixed matrix membrane (with 10% ZSM-5), which is the most cost-effective among the ternary mixed matrix membranes, exhibited the best gas separation performance. For a mixture of CO2 and CH4 gases, the CO2 permeability was 891.23 Barrer, and the CO2/CH4 selectivity was 12.92. Its gas permselectivity exceeds the Robeson 2008 line. For the CO2 and N2 gas mixture, the CO2 permeability is 316.39 Barrer, and the CO2/N2 selectivity is 21.85. It exceeds the Robeson 1991 line for gas permselectivity. Although the PVDF/ZSM-5/EC mixed matrix membrane may not be highly effective in separating CO2 from a mixture of CO2 and N2 (in comparison to CO2/CH4 mixture gases), given the gas composition in biogas and natural gas, it is reasonable to conclude that our PVDF/ZSM-5/EC mixed matrix membrane is well-suited for the selective separation of CO2. This experiment is an important exploration for us to understand the transition of advanced membranes to practical applications. It lays a solid foundation for the production of PVDF/ZSM-5/EC ternary mixed matrix membranes at the lowest cost and for large-scale application in the field of biogas and natural gas purification, as well as greenhouse gas treatment from coal-fired power plants (CO2 selective separation).

An Innovative Approach for the Fabrication of Functional Antibacterial Membranes for Face Mask

ABSTRACTNumber of studies on the hydrophobic and antibacterial membranes has shown significant growth recently, particularly in masks created in response to the coronavirus pandemic. In this study, the supercritical CO2 (scCO2) annealing, a promising green alternative post‐processing method to traditional solvents for polymers, polymer blends, and composites, has been focused. And polymeric membranes were also improved with silver (inorganic) or limestone (organic) particles as antibacterial additives to the polypropylene/polyethylene glycol (PP/PEG) blend. The effect on the structure and properties of the synthesized membranes were examined including the antibacterial and topographical properties before and after CO2 annealing. With increasing contact angle by scCO2 annealing, it was possible to create superhydrophobic surfaces and antibacterial properties against Escherichia coli (E. coli), especially for silver‐loaded PP–PEG membranes based on the collected results. This study is thought to boost the effectiveness of masks against bacteria, the main causes of today's hygiene related epidemics. Finally, scCO2 can be safely applied in mask and membrane production as well as biomedical applications.

Recent advances in the extraction of nanocellulose from lignocellulosic waste for wastewater treatment applications.

Nano-cellulose is a sustainable and high-performance nanomaterial which developed as a transformative solution in different fields due to its excellent properties, including large surface area, and biodegradability. This review paper explored the different types of nano-cellulose (NC) that are Cellulose Nanocrystals, Cellulose Nano-fibers, and Bacterial NC and their distinctive characteristics that make a suitable for advanced applications and also focused on lignocellulosic materials, abundant renewable resources composed of cellulose, hemicellulose, lignin, and their complex structure, while challenging to analyze, offers significant potential for the extraction of nano-cellulose via the advanced process. Furthermore, this work emphasizes the methods used to extract the NCfrom lignocellulosic waste (LCW) and enzymatic pretreatment techniques that improve the efficiency of the process and highlight the fabrication of nano-cellulose membranes and their incorporation into wastewater treatment applications. The superior adsorption capacity and ability to remove organic pollutants, and pathogens make these membranes a capable solution to address the global water purification problems and also underscore the dual benefit of environmental sustainability. This comprehensive examination of nano-cellulose, its extraction from lignocellulosic biomass, and its application in wastewater treatment covered the way for innovations in renewable resources and green technologies.

Tape casting technique in the fabrication of ceramic membranes: A review of influential factors and applications in water and wastewater treatment

Tape casting technique in the fabrication of ceramic membranes: A review of influential factors and applications in water and wastewater treatment

Engineering in-situ fabrication of omniphobic PVDF membrane for high-performance CO2 capture

Engineering in-situ fabrication of omniphobic PVDF membrane for high-performance CO2 capture

Fabrication of niobium MXene-polyphenylsulfone membranes: Advancement in humic acid and dye separation from wastewater

Fabrication of niobium MXene-polyphenylsulfone membranes: Advancement in humic acid and dye separation from wastewater

PDMS membrane incorporated by zeolites with tunable pore chemistry for dimethyl carbonate/methanol azeotropic mixture separation

The separation of organic-organic azeotropic mixtures is important in the petrochemical, agrochemical, and pharmaceutical industries, which is energy-intensive by using the current distillation technology. Pervaporation process is energy-efficient for azeotropic separation, while lacks of high-performing membrane materials. In this work, to realize efficient separation of dimethyl carbonate/methanol azeotropic mixtures, a benchmarked membrane, polydimethylsiloxane (PDMS), was incorporated by zeolites with tunable pore chemistry. Specifically, MFI-type zeolite was grafted by alkyl chains with different carbon numbers (C1, C4, C8), thereby providing tunable transport channels for organic molecules. Based on systematic characterizations (e.g., sorption and LF-NMR) and permeation test, we found that the organophilic alkyl chain can trap organic molecules into the zeolitic pores while may also hinder the organic diffusion through the zeolite due to the steric hindrance effect. The PDMS mixed-matrix membrane (MMM) with optimized C1-grafted MFI loading as high as 50 wt% exhibited separation factor of 3.6, and permeation flux of 11.5 kg m-2 h-1 for 30 wt% DMC-methanol azeotropic mixture at 40 °C. With slightly higher separation factor, the flux of PDMS MMM is 1.5-fold higher than that of the pure PDMS membrane. This work highlights the critical role of filler pore chemistry on the solution-diffusion transport and thus performance enhancement of MMM.

Stereochemical tuning, post-synthesis crosslinking and quaternizing to tune the membrane performance of ultra-stable polyamine nanofiltration membranes

Solvent resistant and pH-stable nanofiltration membranes play a crucial role in solvent or water reuse across various industries, including pharma, chemical, dairy and mining, where stringent pH conditions and chemical stability are imperative. Previous research introduced a chlorine-resistant top-layer for nanofiltration membranes, using 1,2,4,5-tetra(bromomethyl)benzene and 1,2-diaminocyclohexane, with also exceptional stability at extreme pH values and a broad solvent resistance thanks to its crosslinked nature. To further optimize this remarkably stable and versatile membrane material, the unique property of 1,2-diaminocyclohexane, i.e. its stereochemistry, is employed here to manipulate membrane properties through diastereomerism and enantiomeric excess. Filtration experiments employing different 1,2-diaminocyclohexane isomers revealed significant variations in membrane performance, emphasizing the impact of stereochemistry on separation performance. Adjusting the enantiomeric excess of 1,2-diaminocyclohexane resulted in notable changes in membrane permeability and rejection, highlighting the general power of stereochemical control in membrane synthesis. Additionally, post-synthesis modifications, including further crosslinking and quaternization, allowed to tune the membrane structure and performance in both aqueous and solvent media, offering opportunities for optimization towards specific applications. SEM and XPS providing insights into membrane morphology and composition, confirmed the influence of stereochemistry and post-synthesis modifications on membrane properties. These findings demonstrate the efficacy of stereochemistry manipulation and post-synthesis techniques in tailoring pH-stable and solvent resistant nanofiltration membranes for specific applications, paving the way for advanced membrane design.

Facile Fabrication of Binary-Structured Fibrous Membranes with Antifouling and Flame-Retardant Properties for Durable Water/Oil Separation.

Membrane fouling from dispersed droplets during water/oil separation undermines performance and limits long-term use. Additionally, there is an urgent need for flame-retardant fibrous membranes capable of purifying high-temperature polluted oils. Inspired by the binary structure of taro leaves, this study introduces a novel fibrous membrane with both antifouling and flame-retardant properties for water/oil treatment. Eco-friendly cellulose acetate (CA) and multifunctional thermoplastic polyurethane (TPU) were used to construct a microfiber-based substrate membrane via electrospinning. A TPU/ammonium polyphosphate (APP) nanofiber layer with a beads-on-string structure was then electrosprayed onto the substrate as a functional layer. This binary-structured composite membrane leverages the adhesive properties of TPU within both the base microfibers and the functional nanofibers, enhancing stability and structural integrity. The functional layer's re-entrant structure effectively prevents dispersed droplets from adhering under the continuous phase, enabling efficient separation performance in both oil-in-water and water-in-oil emulsions. The membrane demonstrated strong antifouling properties and excellent recyclability, maintaining stable flux and a consistently high separation efficiency (>99.6%) across multiple cycles. Additionally, its flame-retardant properties allowed the membrane to self-extinguish when removed from direct flame. This study presents a novel strategy for fabricating multifunctional separation membranes, with detailed analysis of the underlying mechanisms.

Modulating the elasticity of milk exosome-based hybrid vesicles to optimize transepithelial transport and enhance oral peptide delivery.

To address challenges such as limited loading capacity, restricted targeting precision, and low yield of natural exosomes as drug carriers, the fusion of liposomes and exosomes to create hybrid vesicles has emerged as a viable solution approach. While current research mainly focuses on designing functionalized liposomes, less attention is given to how liposome membrane materials affect the elasticity of these hybrids and their delivery efficiency. This study utilized milk exosomes (mExos) as model exosomes, and generated hybrid vesicles with varying elasticity through the fusion of phospholipids with differing chain lengths, examining the disparities among various hybrid vesicles in their ability to overcoming the gastrointestinal barriers. It was observed that while hard hybrid vesicles exhibited reduced mucus penetration compared to soft hybrid vesicles, they demonstrated a notably higher efficacy in traversing the epithelial cell barrier. The enhanced transepithelial cell capability of hard vesicles can be attributed to their reduced tendency to aggregate in the lysosome through the down-regulated clathrin-mediated endocytosis pathway, as well as by the strengthening of the endoplasmic reticulum-Golgi exocytosis pathway due to their rigid characteristics. In comparison to soft hybrid vesicles, semaglutide (SET) loaded hard hybrid vesicles demonstrated improved in vivo epithelial permeability, enhanced oral bioavailability, and better therapeutic effectiveness. This study could provide valuable insights for determining the optimal elasticity of exosome-liposome hybrid vesicles in the development of oral nanocarriers.

Machine learning models for predicting interaction affinity energy between human serum proteins and hemodialysis membrane materials

Membrane incompatibility poses significant health risks, including severe complications and potential fatality. Surface modification of membranes has emerged as a pivotal technology in the membrane industry, aiming to improve the hemocompatibility and performance of dialysis membranes by mitigating undesired membrane-protein interactions, which can lead to fouling and subsequent protein adsorption. Affinity energy, defined as the strength of interaction between membranes and human serum proteins, plays a crucial role in assessing membrane-protein interactions. These interactions may trigger adverse reactions, potentially harmful to patients. Researchers often rely on trial-and-error approaches to enhance membrane hemocompatibility by reducing these interactions. This study focuses on developing machine learning algorithms that accurately and rapidly predict affinity energy between novel chemical structures of membrane materials and human serum proteins, based on a molecular docking dataset. Various membrane materials with distinct characteristics, chemistry, and orientation are considered in conjunction with different proteins. A comparative analysis of linear regression, K-nearest neighbors regression, decision tree regression, random forest regression, XGBoost regression, lasso regression, and support vector regression is conducted to predict affinity energy. The dataset, comprising 916 records for both training and test segments, incorporates 12 parameters extracted from data points and involves six different proteins. Results indicate that random forest (R² = 0.8987, MSE = 0.36, MAE = 0.45) and XGBoost (R² = 0.83, MSE = 0.49, MAE = 0.49) exhibit comparable predictive performance on the training dataset. However, random forest outperforms XGBoost on the testing dataset. Seven machine learning algorithms for predicting affinity energy are analyzed and compared, with random forest demonstrating superior predictive accuracy. The application of machine learning in predicting affinity energy holds significant promise for researchers and professionals in hemodialysis. These models, by enabling early interventions in hemodialysis membranes, could enhance patient safety and optimize the care of hemodialysis patients.

Performance and Stability of Selected Polymeric Membrane Materials for Use in High-H2S and Humid Natural Gas Feeds

Performance and Stability of Selected Polymeric Membrane Materials for Use in High-H₂S and Humid Natural Gas Feeds

Highly Permselective Contorted Polyamide Desalination Membranes with Enhanced Free Volume Fabricated by mLbL Assembly.

The permeability-selectivity trade-off in polymeric desalination membranes limits the efficiency and increases the costs of reverse osmosis and nanofiltration systems. Ultrathin contorted polyamide films with enhanced free volume demonstrate an impressive 8-fold increase in water permeance while maintaining equivalent salt rejection compared to conventional polyamide membranes made with m-phenylenediamine and trimesoyl chloride monomers. The solution-based molecular layer-by-layer (mLbL) deposition technique employed for membrane fabrication sequentially reacts a shape-persistent contorted diamine monomer with a trimesoyl chloride monomer, forming highly cross-linked, dense polyamide networks while avoiding the kinetic and mass transfer limitations of traditional interfacial polymerization. The mLbL process allows precise nanoscale control over polyamide selective layer thickness, network structure, and surface roughness. The resulting controlled film thicknesses enable direct measurements of water and NaCl permeabilities. The permselectivities of contorted polyamide membranes surpass those of commercial desalination membranes and approach the reported polyamide upper bound. Solution-diffusion transport modeling indicates that this high permselectivity may be attributed to enhanced water transport pathways in the contorted polyamides that increase water diffusivity-permeability while maintaining high solute rejection through solubility-selectivity.

Fabrication and Optimization of Alginate Membranes for Improved Wastewater Treatment

Alginate, a naturally occurring biopolymer extracted from brown algae, presents a promising avenue for developing sustainable and efficient membranes for wastewater treatment. This review comprehensively examines recent advancements in the fabrication, modification, and application of alginate-based membranes for effective water purification. The paper delves into various fabrication techniques, including casting, electrospinning, and 3D printing, which influence the structural and functional properties of the resulting alginate membranes. To enhance performance, strategies such as crosslinking, incorporation of porogens, and surface functionalization are employed. These modifications optimize crucial properties like mechanical strength, porosity, selectivity, and antifouling resistance. Furthermore, Response Surface Methodology (RSM) has emerged as a valuable tool for systematically optimizing fabrication parameters, enabling researchers to identify optimal conditions for achieving desired membrane characteristics. The integration of alginate membranes with biological treatment processes, such as phycoremediation (utilizing microalgae) and mycoremediation (employing fungi), offers a synergistic approach to enhance wastewater treatment efficiency. By immobilizing these microorganisms within the alginate matrix, their bioremediation capabilities are amplified, leading to improved pollutant degradation and nutrient removal. In conclusion, alginate-based membranes demonstrate significant potential as a sustainable and effective technology for wastewater treatment. Continued research and development, focusing on optimizing fabrication processes and exploring innovative integration strategies with biological systems, will further advance the application of alginate membranes in addressing the pressing global challenge of water pollution.

Simulation of fluid flow with Cuprophan and AN69ST membranes in the dialyzer during hemodialysis.

Hemodialysis is a crucial procedure for removing toxins and waste from the body when kidneys fail to perform this function effectively. This study addresses the need to improve the efficiency and biocompatibility of membranes used in dialyzers. We simulate fluid flow through two types of membranes, Cuprophan (cellulosic) and AN69ST (synthetic), to understand the complex mechanisms involved and quantify key variables such as pressure, concentration, and flow. This study presents a detailed model that applies mass conservation equations and Navier-Stokes principles adapted for porous media, along with heat and mass transfer considerations. The results revealed significant differences in the flow behavior and filtration efficiency between the two membranes, highlighting the superiority of the AN69ST membrane in terms of flow rate and toxin removal. This model serves as a valuable tool for characterizing new porous membranes in dialysis applications, enabling the prediction of the temperature, pressure, and concentration profiles. By providing this information without requiring extensive experimentation, the model complements the design and evaluation of new membranes and, optimizes their development. The ability to predict these profiles is crucial because they directly influence the parameters that determine treatment effectiveness. Moreover, this study underscores the importance of continued innovation in membrane materials and designs, contributing to improved clinical outcomes and treatment efficiency, representing a significant advancement in healthcare.&#xD.