Membranes

28 pages, 2479 KB

Open AccessReview

Emerging Approaches to Mitigate Neural Cell Degeneration with Nanoparticles-Enhanced Polyelectrolyte Systems

by Angelika Kwiatkowska, Anna Grzeczkowicz, Agata Lipko, Beata Kazimierczak and Ludomira H. Granicka

Membranes 2025, 15(10), 313; https://doi.org/10.3390/membranes15100313 (registering DOI) - 14 Oct 2025

Abstract

Counteracting neurodegenerative diseases (NDs) presents a multifaceted challenge in the aging societies of Western countries. Each year, millions of people worldwide are affected by such ailments as Parkinson’s disease (PD), Alzheimer’s disease (AD), Huntington’s disease (HD), multiple sclerosis (MS), spinal cord injury, ischemic [...] Read more.

Counteracting neurodegenerative diseases (NDs) presents a multifaceted challenge in the aging societies of Western countries. Each year, millions of people worldwide are affected by such ailments as Parkinson’s disease (PD), Alzheimer’s disease (AD), Huntington’s disease (HD), multiple sclerosis (MS), spinal cord injury, ischemic stroke, motor neuron disease, spinal muscular atrophy, spinocerebellar ataxia, and amyotrophic lateral sclerosis (ALS). Advancements in modern biomaterial technologies present substantial opportunities for the field of regenerative medicine. Nevertheless, limitations arise from the requirement that biomaterial design be tailored to the specific biological parameters of the target cell types with which they are intended to interact. Such an opportunity creates nanomaterials involving nanoparticles. The surface chemistry of nanoparticles, especially when functionalized with bioactive agents, enhances biocompatibility and facilitates interactions with nervous cells. Herein, we review contemporary strategies in the application of biomaterials for nerve regeneration, with particular emphasis on nanomaterials and biocompatible polyelectrolyte layers, which the authors identify as having the most significant potential to drive transformative advances in regenerative medicine in the near future. Full article

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17 pages, 1854 KB

Open AccessArticle

Application of Two-Compartment Bipolar Membrane Electrodialysis for Treatment of Waste Na₂SO₄ Solution

by Young-Jae Lee, Min-Hyuk Seo, Jae-Hyuk Chang, Jun-Hee Kim and Jae-Woo Ahn

Membranes 2025, 15(10), 312; https://doi.org/10.3390/membranes15100312 - 14 Oct 2025

Abstract

This study evaluated the performance of a constant-current two-compartment bipolar membrane electrodialysis (BMED) system comprising cation exchange membranes and bipolar membranes for the recovery of sodium hydroxide (NaOH) from sodium sulfate (Na₂SO₄) solution. Key operating parameters, current density, feed [...] Read more.

This study evaluated the performance of a constant-current two-compartment bipolar membrane electrodialysis (BMED) system comprising cation exchange membranes and bipolar membranes for the recovery of sodium hydroxide (NaOH) from sodium sulfate (Na₂SO₄) solution. Key operating parameters, current density, feed concentration, initial base concentration, and solution volume, were systematically varied to investigate their effects on ion transport, NaOH concentration, current efficiency, and energy consumption. At 450 A/m² with 1.30 M Na₂SO₄, 0.10 M initial NaOH, and 1.00 L solution volume, the system achieved a NaOH recovery yield of 69.21%, a final concentration of 2.13 M, a current efficiency of 36.39%, and an energy consumption of 1.82 kWh/kg Na₂SO₄ processed, corresponding to 4.72 kWh/kg NaOH produced, indicating optimal energy efficiency and process stability. To maximize concentration, the highest NaOH concentration of 2.85 M was obtained at the same current density by reducing the initial NaOH volume to 0.50 L, although this led to increased water transport and higher energy consumption (2.31 kWh/kg Na₂SO₄; 5.99 kWh/kg NaOH), compromising process efficiency. Full article

(This article belongs to the Special Issue Electrochemical Membrane and Membrane Processes)

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15 pages, 2958 KB

Open AccessArticle

Practical Algal Control in Lower Yangtze Reservoirs Using Composite Microfiltration Physical Enclosure

by Bin Xu, Fangzhou Liu, Qi Zhang, Congcong Ni, Jianan Gao and Xin Huang

Membranes 2025, 15(10), 311; https://doi.org/10.3390/membranes15100311 - 13 Oct 2025

Abstract

Source water reservoirs in the lower reaches of the Yangtze River are increasingly threatened by algal contamination, driven by fluctuations in upstream water quality. To ensure stable reservoir operation and protect downstream drinking water sources, physical enclosures are widely used. However, most algal [...] Read more.

Source water reservoirs in the lower reaches of the Yangtze River are increasingly threatened by algal contamination, driven by fluctuations in upstream water quality. To ensure stable reservoir operation and protect downstream drinking water sources, physical enclosures are widely used. However, most algal pollution in reservoirs consists of microalgae (diameters < 100 μm), and conventional algae barriers are effective primarily against visible algal blooms but perform poorly against microscopic algal clusters. To address this limitation, we developed a composite microfiltration physical enclosure system by integrating a microfiltration membrane, supported by a mechanical layer, onto physical enclosures. The algal removal performance of this system was evaluated from lab-scale tests to field-scale applications. Results demonstrated that the composite membrane exhibited excellent interception efficiency against algal aggregates, with algae density in the filtered water reduced by over 80%. The composite enclosure effectively filters multiple algae species, significantly reducing the risk of algae entering downstream water treatment plants, thereby alleviating the burden of traditional processes and reducing operating costs. Full article

(This article belongs to the Special Issue Functionalized Membranes for Water/Wastewater Treatment)

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19 pages, 2166 KB

Open AccessArticle

Life Cycle Assessment and Critical Raw Materials Analysis of Innovative Palladium-Substituted Membranes for Hydrogen Separation

by Ali Mohtashamifar, Simone Battiston, Stefano Fasolin, Stefania Fiameni, Francesca Visentin and Simona Barison

Membranes 2025, 15(10), 310; https://doi.org/10.3390/membranes15100310 - 13 Oct 2025

Abstract

Palladium-based membranes for hydrogen separation offer the most promising gas permeation and selectivity, but their large-scale application has been limited due to the high environmental burdens and criticality of palladium. Herein, the possibility of substituting Pd with candidate elements in the composition of [...] Read more.

Palladium-based membranes for hydrogen separation offer the most promising gas permeation and selectivity, but their large-scale application has been limited due to the high environmental burdens and criticality of palladium. Herein, the possibility of substituting Pd with candidate elements in the composition of metallic micro-scale membranes (with permeability in the range of 5–50 × 10⁻¹² mol m^–1 Pa^–1 s⁻¹) deposited via High Power Impulse Magnetron Sputtering was investigated. This study proposed an innovative framework for a more comprehensive investigation of the sustainability challenges related to this lab-scale technology by integrating Life Cycle Assessment (LCA) and criticality analyses, thereby supporting materials selection efforts. First, the criticality status of several elements used in hydrogen separation membranes was screened with two different approaches. Furthermore, the environmental impacts of novel membrane compositions were compared with a high Pd-content reference membrane (Pd₇₇Ag₂₃) through cradle-to-gate LCA. For robust LCA modeling, uncertainty analysis was performed via Monte Carlo simulation, exploiting errors estimated for both primary and secondary data. A direct relationship was identified between the Pd content in membranes and the associated environmental impacts. VPd proved to be a promising candidate by exhibiting lower total impacts than the PdAg (65% or 71% considering thickness of 3.16 µm or permeance of 2.03 × 10⁻⁶ mol m⁻² Pa⁻¹ s⁻¹, respectively). Full article

(This article belongs to the Special Issue Membranes and Membrane Reactors for Gas Purification and Production: Towards More Sustainable Processes)

13 pages, 1639 KB

Open AccessArticle

Assessing the Stability of Polymer Inclusion Membranes: The Case of Aliquat 336-Based Membranes

by Kalina Velikova, Todor Dudev, Tsveta Sarafska, Lea Kukoc-Modun, Spas D. Kolev and Tony Spassov

Membranes 2025, 15(10), 309; https://doi.org/10.3390/membranes15100309 - 13 Oct 2025

Abstract

Leaching of the extractant from polymer inclusion membranes (PIMs) into the feed and receiving aqueous solutions shortens their life. Therefore, when a particular PIM extractant has been selected, it is important to choose a base polymer that will minimize to the greatest extent [...] Read more.

Leaching of the extractant from polymer inclusion membranes (PIMs) into the feed and receiving aqueous solutions shortens their life. Therefore, when a particular PIM extractant has been selected, it is important to choose a base polymer that will minimize to the greatest extent extractant leaching compared to other base polymers, thus providing the best stability of the PIM. However, comparisons of the stability of PIMs composed of the same extractant and different base polymers is usually conducted by multiple cycles of extraction and back-extraction steps, which are time-consuming and labor-intensive. An alternative approach based on thermal analysis (thermogravimetric analysis (TGA) and differential thermal analysis (DTA)) was developed and applied to PIMs containing 40 wt.% Aliquat 336, one of the most frequently used PIM extractants, and the three most frequently used PIM base polymers, i.e., poly(vinyl chloride) (PVC), cellulose triacetate (CTA), and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). The temperatures and enthalpies associated with Aliquat 336 release were compared, with PVDF-HFP exhibiting the highest values, indicating the strongest interaction between the extractant and the polymer matrix and, thus, the highest stability. The PVC-based PIM was predicted to be the most prone to extractant leaching among the PIMs studied. This stability ranking was confirmed theoretically by quantum chemistry (DFT) calculations, which provided molecular-level insights into the likely interaction sites between Aliquat 336 and the polymer chains. An experimental validation of the above leaching order was also provided by PIM leaching experiments in aqueous 0.1 M and 0.05 M NaCl solutions, where membrane mass losses over a 24 h period were determined. The results of the current study demonstrated thermal analysis to be a fast and viable approach in comparing the stability of PIMs with the same extractant but different base polymers. Full article

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20 pages, 4981 KB

Open AccessArticle

Main Techniques to Reduce Concentrate and Achieve Salt–Organic Separation During Landfill Leachate Treatment Using Low-Rejection Nanofiltration Membranes

by Alexei Pervov, Dmitry Spitsov and Tatiana Shirkova

Membranes 2025, 15(10), 308; https://doi.org/10.3390/membranes15100308 - 10 Oct 2025

Viewed by 191

Abstract

Landfill is a source of environmental concern as it may contaminate surface and groundwater, which could be a major source of potable water supply. Reverse osmosis (RO) membrane treatment is a well-known technique for treating leachate, but it requires high pressures of 80 [...] Read more.

Landfill is a source of environmental concern as it may contaminate surface and groundwater, which could be a major source of potable water supply. Reverse osmosis (RO) membrane treatment is a well-known technique for treating leachate, but it requires high pressures of 80 bars or more to function. In addition, pretreatment, scaling, biofouling and concentrate disposal bring additional challenges to RO operation. The use of nanofiltration (NF) membranes with low rejection ensures the concentrate is separated into organic and salt solutions at a low pressure of 16–18 bars and ensures the concentrate volume is reduced to less than 3% of its initial value. This results in a reduction in energy consumption by a factor of least three compared to using conventional high-pressure RO, which reduces the initial leachate amount to 9–10%, and evaporation results in a subsequent reduction in concentrate volume to 3–4 per cent of the initial leachate volume. Due to the low osmotic pressure, the volume of an organic solution after separation can be reduced by three to four times compared to a saline solution of the same concentration. Full article

(This article belongs to the Special Issue New Advances in Membrane Separation Technology for Water Pollution Control and Membrane Fouling Mitigation)

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18 pages, 5645 KB

Open AccessArticle

Cost-Effective and Durable Ceramic Membrane: Fabrication and Performance Optimization

by Ahmed H. El-Shazly and Yomna A. Fahmy

Membranes 2025, 15(10), 307; https://doi.org/10.3390/membranes15100307 - 9 Oct 2025

Viewed by 254

Abstract

The main objective of this work is to develop a cost-effective and durable ceramic membrane for water purification. The low-cost ceramic membrane was fabricated using readily available materials, such as clays, aluminum oxide, and calcium carbonate, The membrane was fabricated by uniaxial pressing [...] Read more.

The main objective of this work is to develop a cost-effective and durable ceramic membrane for water purification. The low-cost ceramic membrane was fabricated using readily available materials, such as clays, aluminum oxide, and calcium carbonate, The membrane was fabricated by uniaxial pressing at different pressures and sintering temperatures, then tested using a scanning electron microscope (SEM) and XRD. The porosity of the resulting membrane was 38.7%, and the contact angle was 65° indicating good hydrophilicity for filtration applications. The main composition was 70% clay, 25% CaCO₃, and 5% alumina. The removal % for methylene blue was tested at varying concentrations, achieving up to 99% removal, an initial flux of 496.8 L m⁻² h⁻¹, and an average pore size of 2 µm. Furthermore, the research explores the effect of backwashing cycles and techniques on the membrane long-term performance. The results indicated that washing the membrane for four cycles to cleanness has achieved an improved efficiency of the membrane and % dye rejection. Back washing was achieved using no chemicals; only distilled water and drying were used. A preliminary costs assessment of the production for affordable membrane resulted in a value of 170 USD/m². The findings demonstrate that optimizing backwashing cycles is essential for prolonging the membrane lifespan and lowering operation costs. Full article

(This article belongs to the Special Issue Ceramic Membranes for Wastewater and Water Reuse (2nd Edition))

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21 pages, 5920 KB

Open AccessArticle

Enhanced CO₂ Separation Performance of Mixed Matrix Membranes with Pebax and Amino-Functionalized Carbon Nitride Nanosheets

by Mengran Hua, Qinqin Sun, Na Li, Mingchao Zhu, Yongze Lu, Zhaoxia Hu and Shouwen Chen

Membranes 2025, 15(10), 306; https://doi.org/10.3390/membranes15100306 - 7 Oct 2025

Viewed by 376

Abstract

Highly permeable and selective membranes are crucial for energy-efficient gas separation. Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) has attracted significant attention due to its unique structural characteristics, including ultra-thin thickness, inherent surface porosity, and abundant amine groups. However, the [...] Read more.

Highly permeable and selective membranes are crucial for energy-efficient gas separation. Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) has attracted significant attention due to its unique structural characteristics, including ultra-thin thickness, inherent surface porosity, and abundant amine groups. However, the interfacial defects caused by poor compatibility between g-C₃N₄ and polymers deteriorate the separation performance of membrane materials. In this study, amino-functionalized g-C₃N₄ nanosheets (CN@PEI) was prepared by a post-synthesis method, then blended with the polymer Pebax to fabricate Pebax/CN@PEI mixed matrix membranes (MMMs). Compared to g-C₃N₄, MMMs with CN@PEI loading of 20 wt% as nanofiller exhibited a CO₂ permeance of 241 Barrer as well as the CO₂/CH₄ and CO₂/N₂ selectivity of 39.7 and 61.2, respectively, at the feed gas pressure of 2 bar, which approaches the 2008 Robeson upper bound and exceeded the 1991 Robeson upper bound. The Pebax/CN@PEI (20) membrane showed robust stability performance over 70 h continuous gas permeability testing, and no significant decline was observed. SEM characterization revealed a uniform dispersion of CN@PEI throughout the Pebax matrix, demonstrating excellent interfacial compatibility between the components. The increased free volume fraction, enhanced solubility, and higher diffusion coefficient demonstrated that the incorporation of CN@PEI nanosheets introduced more CO₂-philic amino groups and disrupted the chain packing of the Pebax matrix, thereby creating additional diffusion channels and facilitating CO₂ transport. Full article

(This article belongs to the Special Issue Novel Membranes for Carbon Capture and Conversion)

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13 pages, 1099 KB

Open AccessArticle

Photochemical Methods to Study the Radical-Induced Degradation of Anion-Exchange Membranes

by Panna Solyom, Thomas Nauser and Tamas Nemeth

Membranes 2025, 15(10), 305; https://doi.org/10.3390/membranes15100305 - 7 Oct 2025

Viewed by 293

Abstract

We adapted two photochemical methods to generate radicals and assess their impact on anion exchange membrane stability, independent of base-induced degradation. Through the exposure of aqueous solutions of potassium nitrite or suspensions of TiO₂ to UV light at 365 nm, we generated [...] Read more.

We adapted two photochemical methods to generate radicals and assess their impact on anion exchange membrane stability, independent of base-induced degradation. Through the exposure of aqueous solutions of potassium nitrite or suspensions of TiO₂ to UV light at 365 nm, we generated hydroxyl radicals or a combination of hydroxyl and superoxide radicals. The methods’ applicability to anion exchange membranes (AEMs) is demonstrated on three commercial AEMs: PiperION-40, FM-FAA-3-PK-75, and PNB-R45. Changes in ion-exchange capacity, along with FT-IR and NMR analyses, revealed significant degradation in thinner, non-reinforced membranes, while thicker and reinforced membranes showed greater resistance. We attribute this to the limited penetration depth of highly reactive radicals into the membrane. Both methods are practical and inexpensive tools for benchmarking AEM stability against radical attack. Full article

(This article belongs to the Section Membrane Applications for Energy)

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57 pages, 3245 KB

Open AccessReview

Cellulose-Based Ion Exchange Membranes for Electrochemical Energy Systems: A Review

by Nur Syahirah Faiha Shawalludin, Saidatul Sophia Sha’rani, Mohamed Azlan Suhot, Shamsul Sarip and Mohamed Mahmoud Nasef

Membranes 2025, 15(10), 304; https://doi.org/10.3390/membranes15100304 - 6 Oct 2025

Viewed by 316

Abstract

Cellulose, the most abundant polysaccharide on earth, possesses desirable properties such as biodegradability, low cost, and low toxicity, making it suitable for a wide range of applications. Being a non-conductive material, the structure of the nanocellulose can be modified or incorporated with conductive [...] Read more.

Cellulose, the most abundant polysaccharide on earth, possesses desirable properties such as biodegradability, low cost, and low toxicity, making it suitable for a wide range of applications. Being a non-conductive material, the structure of the nanocellulose can be modified or incorporated with conductive filler to facilitate charge transport between the polymer matrix and conductive components. Recently, cellulose-based ion exchange membranes (IEMs) have gained strong attention as alternatives to environmentally burdening synthetic polymers in electrochemical energy systems, owing to their renewable nature and versatile chemical structure. This article provides a comprehensive review of the structures, fabrication aspects and properties of various cellulose-based membranes for fuel cells and water electrolyzers, batteries, supercapacitors, and reverse electrodialysis (RED) applications. The scope includes an overview of various cellulose-based membrane fabrication methods, different forms of cellulose, and their applications in energy conversion and energy storage systems. The review also discusses the fundamentals of electrochemical energy systems, the role of IEMs, and recent advancements in the cellulose-based membranes’ research and development. Finally, it highlights current challenges to their performance and sustainability, along with recommendations for future research directions. Full article

(This article belongs to the Section Membrane Applications for Energy)

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16 pages, 1854 KB

Open AccessArticle

Electrostatic Targeting of Cancer Cell Membrane Models by NA-CATH:ATRA-1-ATRA-1: A Biophysical Perspective

by Maria C. Klaiss-Luna, Małgorzata Jemioła-Rzemińska, Marcela Manrique-Moreno and Kazimierz Strzałka

Membranes 2025, 15(10), 303; https://doi.org/10.3390/membranes15100303 - 6 Oct 2025

Viewed by 301

Abstract

Breast cancer continues to be the leading cancer diagnosis among women worldwide, affecting populations in both industrialized and developing regions. Given the rising number of diagnosed cases each year, there is an urgent need to explore novel compounds with potential anticancer properties. One [...] Read more.

Breast cancer continues to be the leading cancer diagnosis among women worldwide, affecting populations in both industrialized and developing regions. Given the rising number of diagnosed cases each year, there is an urgent need to explore novel compounds with potential anticancer properties. One group of such candidates includes cationic peptides, which have shown promise due to their unique membrane-targeting mechanisms that are difficult for cancer cells to resist. This study presents an initial biophysical assessment of NA-CATH:ATRA-1-ATRA-1, a synthetic peptide modeled after NA-CATH, originally sourced from the venom of the Chinese cobra (Naja atra). The peptide’s interactions with lipid bilayers mimicking cancerous and healthy cell membranes were examined using differential scanning calorimetry and Fourier-transform infrared spectroscopy. Findings revealed a pronounced affinity of NA-CATH:ATRA-1-ATRA-1 for eukaryotic membrane lipids, particularly phosphatidylserine, indicating that its mechanism likely involves electrostatic attraction to negatively charged lipids characteristic of cancer cell membranes. Such biophysical insights are vital for understanding how membrane-active peptides could be harnessed in future cancer therapies. Full article

(This article belongs to the Collection Feature Papers in Membranes in Life Sciences)

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16 pages, 1337 KB

Open AccessArticle

Dynamic Imaging of Lipid Order and Heterogeneous Microviscosity in Mitochondrial Membranes of Potato Tubers Under Abiotic Stress

by Vadim N. Nurminsky, Svetlana I. Shamanova, Olga I. Grabelnych, Natalia V. Ozolina, Yuguang Wang and Alla I. Perfileva

Membranes 2025, 15(10), 302; https://doi.org/10.3390/membranes15100302 - 6 Oct 2025

Viewed by 296

Abstract

Microviscosity and lipid order are the main parameters characterizing the phase states of the membrane. Variations in microviscosity and lipid composition in a living cell may indicate serious disturbances, including various kinds of stress. In this work, the effect of hyperosmotic stress on [...] Read more.

Microviscosity and lipid order are the main parameters characterizing the phase states of the membrane. Variations in microviscosity and lipid composition in a living cell may indicate serious disturbances, including various kinds of stress. In this work, the effect of hyperosmotic stress on the microviscosity of mitochondrial membranes was investigated, using potato (Solanum tuberosum L.) tuber mitochondria. The microviscosity of mitochondrial membranes isolated from check and stressed (9 days at 34–36 °C) tubers was estimated by determining the generalized polarization (GP) values using a Laurdan fluorescent probe in confocal microscopy studies. It was revealed that the GP distribution in mitochondria isolated from stressed tubers contained new component-characterizing membrane domains with an increased lipid order compared to the rest of the membrane. We have mapped the microviscosity of mitochondrial membranes for the first time and observed the dynamics of the membrane microviscosity of an individual mitochondrion. The hyperosmotic stress significantly influences the functional state of potato mitochondria, decreasing the substrate oxidation rate and respiratory control coefficient but increasing MitoTracker Orange fluorescence. Under hyperosmotic stress, the microviscosity of mitochondrial membranes changes, and membrane domains with increased lipid order are formed. The revealed changes open up prospects for further research on the participation of raft-like microdomains of mitochondria in plant resistance to stress factors. Full article

(This article belongs to the Special Issue Composition and Biophysical Properties of Lipid Membranes)

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23 pages, 6589 KB

Open AccessArticle

Assessment and Discussion of the Steady-State Determination in Zeolite Composite Membranes for Multi-Component Diffusion

by Katarzyna Bizon, Dominika Boroń and Bolesław Tabiś

Membranes 2025, 15(10), 301; https://doi.org/10.3390/membranes15100301 - 2 Oct 2025

Viewed by 247

Abstract

A versatile, clear, and accurate method for determining the steady states of multi-component diffusion through composite membranes is presented in this study. This method can be used for simulating and designing membranes with any support orientation with respect to the zeolite film. In [...] Read more.

A versatile, clear, and accurate method for determining the steady states of multi-component diffusion through composite membranes is presented in this study. This method can be used for simulating and designing membranes with any support orientation with respect to the zeolite film. In the mathematical model of the membrane, it was assumed that mass transport in the zeolite layer occurs by surface diffusion in accordance with the generalized Maxwell–Stefan model. Diffusion in the macroporous support was described by the dusty gas model (DGM). An alternative model of diffusion in the zeolite was proposed to the universally accepted model, which uses a matrix of thermodynamic factors Γ. Thus, the difficulty of analytically determining this matrix for more complex adsorption equilibria was eliminated. This article is dedicated to methodological and cognitive aspects. The practical features of the method are illustrated using two gas mixtures as examples, namely {H₂, CO₂} and {H₂, n-C₄H₁₀}. The roles of zeolite and support in the separation of these mixtures are discussed. It was demonstrated under what circumstances the presence of the support can be neglected in the steady-state analysis of the membrane. The effect of the alternative application of the dusty gas model or viscous flow only in the microporous support was discussed. Full article

(This article belongs to the Special Issue Composite Membranes for Gas and Vapor Separation)

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47 pages, 5360 KB

Open AccessReview

Current Progress in Advanced Functional Membranes for Water-Pollutant Removal: A Critical Review

by Manseeb M. Mannaf, Md. Mahbubur Rahman, Sonkorson Talukder Sabuj, Niladri Talukder and Eon Soo Lee

Membranes 2025, 15(10), 300; https://doi.org/10.3390/membranes15100300 - 2 Oct 2025

Viewed by 908

Abstract

As water pollution from dyes, pharmaceuticals, heavy metals, and other emerging contaminants continues to rise at an alarming rate, ensuring access to clean and safe water has become a pressing global challenge. Conventional water treatment methods, though widely used, often fall short in [...] Read more.

As water pollution from dyes, pharmaceuticals, heavy metals, and other emerging contaminants continues to rise at an alarming rate, ensuring access to clean and safe water has become a pressing global challenge. Conventional water treatment methods, though widely used, often fall short in effectively addressing these complex pollutants. In response, researchers have turned to Advanced Functional Membranes (AFMs) as promising alternatives, owing to their customizable structures and enhanced performance. Among the most explored AFMs are those based on metal–organic frameworks (MOFs), carbon nanotubes (CNTs), and electro–catalytic systems, each offering unique advantages such as high permeability, selective pollutant removal, and compatibility with advanced oxidation processes (AOPs). Notably, hybrid systems combining AFMs with electrochemical or photocatalytic technologies have demonstrated remarkable efficiency in laboratory settings. However, translating these successes to real-world applications remains a challenge due to issues related to cost, scalability, and long-term stability. This review explores the recent progress in AFM development, particularly MOF-based, CNT-based, and electro-Fenton (EF)-based membranes, highlighting their material aspects, pollutant filtration mechanisms, benefits, and limitations. It also offers insights into how these next-generation materials can contribute to more sustainable, practical, and economically viable water purification solutions in the near future. Full article

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15 pages, 1246 KB

Open AccessArticle

Removal of Aggregates During Bispecific Antibody Purification Using Hydrophobic Interaction Chromatography

by Puya Zhao, Yue Qi and Kai Gao

Membranes 2025, 15(10), 299; https://doi.org/10.3390/membranes15100299 - 1 Oct 2025

Viewed by 450

Abstract

In the production of recombinant antibody/Fc-fusion proteins using mammalian cells, many aggregates often form alongside the target proteins, particularly with bispecific antibodies. To ensure the safety of biological products, it is essential to control the amount of aggregates within a specific range. A [...] Read more.

In the production of recombinant antibody/Fc-fusion proteins using mammalian cells, many aggregates often form alongside the target proteins, particularly with bispecific antibodies. To ensure the safety of biological products, it is essential to control the amount of aggregates within a specific range. A traditional downstream process typically involves using Protein A (ProA) resin to capture the target antibody, followed by two polishing steps to ensure purity; for instance, using an anion exchange chromatography (AEX) in flow-through mode and a cation exchange chromatography (CEX) in binding–elution mode. In this study, we choose a Dual Action Fab (DAF), which can bind two antigens and is prone to aggregation when expression in CHO (Chinese Hamster Ovary) cells. We introduce hydrophobic interaction membrane chromatography (HIMC) operating in flow-through mode, which enhances production efficiency while reducing costs and the risks associated with column packing. We evaluated the impact of the operating buffer system, as well as the pH and conductivity of the loading samples, on aggregate removal using HIMC. Additionally, we investigated the mechanism of aggregate binding and found that loading conditions had a limited impact on this process. Overall, our findings indicate that employing HIMC can achieve a 20% reduction in aggregate levels. These results demonstrate that HIMC in flow-through mode is an effective and robust approach for reducing aggregates during antibody purification. Full article

(This article belongs to the Special Issue Application of Membrane Materials in Bioseparation and Downstream Processing)

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28 pages, 7157 KB

Open AccessArticle

Development and Characterization of Sawdust-Based Ceramic Membranes for Textile Effluent Treatment

by Ana Vitória Santos Marques, Antusia dos Santos Barbosa, Larissa Fernandes Maia, Meiry Gláucia Freire Rodrigues, Tellys Lins Almeida Barbosa and Carlos Bruno Barreto Luna

Membranes 2025, 15(10), 298; https://doi.org/10.3390/membranes15100298 - 1 Oct 2025

Cited by 1 | Viewed by 484

Abstract

Membranes were assessed on a bench scale for their performance in methylene blue dye separation. The sawdust, along with Brazilian clay and kaolin, were mixed and compacted by uniaxial pressing and sintered at 650 °C. The membranes were characterized by several techniques, including [...] Read more.

Membranes were assessed on a bench scale for their performance in methylene blue dye separation. The sawdust, along with Brazilian clay and kaolin, were mixed and compacted by uniaxial pressing and sintered at 650 °C. The membranes were characterized by several techniques, including X-ray diffraction, scanning electron microscopy, porosity, mechanical strength, water uptake, and membrane hydrodynamic permeability. The results demonstrated that the incorporation of sawdust not only altered the pore morphology but also significantly improved water permeation and dye removal efficiency. The ceramic membrane had an average pore diameter of 0.346–0.622 µm and porosities ranging from 40.85 to 42.96%. The membranes were applied to the microfiltration of synthetic effluent containing methylene blue (MB) and, additionally, subjected to investigation of their adsorptive capacity. All membrane variants showed high hydrophilicity (contact angles < 60°) and achieved MB rejection efficiencies higher than 96%, demonstrating their efficiency in treating dye-contaminated effluents. Batch adsorption using ceramic membranes (M0–M3) removed 34.0–41.2% of methylene blue. Adsorption behavior fitted both Langmuir and Freundlich models, indicating mixed mono- and multilayer mechanisms. FTIR confirmed electrostatic interactions, hydrogen bonding, and possible π–π interactions in dye retention. Full article

(This article belongs to the Special Issue Preparation, Characterization, and Application of Advanced Separation Membrane Materials)

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17 pages, 3387 KB

Open AccessArticle

Comprehensive Investigation of Iron Salt Effects on Membrane Bioreactor from Perspective of Controlling Iron Leakage

by Qiaoying Wang, Bingbing Zhang, Jicheng Sun, Wenjia Zheng, Jie Zhang and Zhichao Wu

Membranes 2025, 15(10), 297; https://doi.org/10.3390/membranes15100297 - 30 Sep 2025

Viewed by 285

Abstract

Although adding iron salts can improve phosphorus removal in membrane bioreactor (MBR) processes, overdosing iron salts may result in excessive iron concentrations in the effluent and pose risks of surface water contamination. In this study, an optimized iron salt dosing method was proposed [...] Read more.

Although adding iron salts can improve phosphorus removal in membrane bioreactor (MBR) processes, overdosing iron salts may result in excessive iron concentrations in the effluent and pose risks of surface water contamination. In this study, an optimized iron salt dosing method was proposed to comprehensively investigate its effects on the performance of MBRs and the control of iron leakage. The results showed that batch dosing of solid iron salts (Fe₂(SO₄)₃) into the influent or activated sludge maintained an effluent Fe³⁺ concentration below 1.0 mg/L and a total phosphorus (TP) concentration below 0.30 mg/L. Long-term operation of the MBR (under conditions of HRT = 4.3 h, SRT = 20 d, and MLSS = 12 g/L) showed that batch dosing of solid iron salts led to an increase in the effluent ammonia–nitrogen (NH₃-N) concentration, and the nitrification effect was restored after supplementing the alkalinity. Iron salts increased the TP removal rate by approximately 40% while inhibiting the biological phosphorus removal capacity. The average Fe³⁺ concentration in the membrane effluent (0.23 ± 0.11 mg/L) met China’s Environmental Quality Standard for Surface Water (GB3838-2002). This study demonstrates that batch dosing of solid iron salts effectively controls iron concentration in the MBR effluent while preventing secondary pollution. The mechanisms of the impact of iron salts on MBR performance provide crucial theoretical and technical support for MBR process optimization. Full article

(This article belongs to the Special Issue Membrane Distillation and Other Membrane-Related Applications for Water Cleaning and Desalination)

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15 pages, 10073 KB

Open AccessArticle

Defect Engineering in Fluorinated Metal–Organic Frameworks Within Mixed-Matrix Membranes for Enhanced CO₂ Separation

by Benxing Li, Lei Wang, Yizheng Tao, Rujing Hou and Yichang Pan

Membranes 2025, 15(10), 296; https://doi.org/10.3390/membranes15100296 - 30 Sep 2025

Viewed by 332

Abstract

Developing highly permeable and selective membranes for energy-efficient CO₂/CH₄ separation remains challenging. Mixed-matrix membranes (MMMs) integrating polymer matrices with metal–organic frameworks (MOFs) offer significant potential. However, rational filler–matrix matching presents substantial difficulties, constraining separation performance. In this work, defects were [...] Read more.

Developing highly permeable and selective membranes for energy-efficient CO₂/CH₄ separation remains challenging. Mixed-matrix membranes (MMMs) integrating polymer matrices with metal–organic frameworks (MOFs) offer significant potential. However, rational filler–matrix matching presents substantial difficulties, constraining separation performance. In this work, defects were engineered within fluorinated MOF ZU-61 through the partial replacement of 4,4′-bipyridine linkers with pyridine modulators, producing high-porosity HP-ZU-61 nanoparticles exhibiting a 267% BET surface area enhancement (992.9 m² g⁻¹) over low-porosity ZU-61 (LP-ZU-61) (372.2 m² g⁻¹). The HP-ZU-61/6FDA-DAM MMMs (30 wt.%) demonstrated homogeneous filler dispersion and pre-served crystallinity, achieving a CO₂ permeability of 1626 barrer and CO₂/CH₄ selectivity (33), surpassing the 2008 Robeson upper bound. Solution-diffusion modeling indicated ligand deficiencies generated accelerated diffusion pathways, while defect-induced unsaturated metal sites functioned as strong CO₂ adsorption centers that maintained solubility selectivity. This study establishes defect engineering in fluorinated MOF-based MMMs as a practical strategy to concurrently overcome the permeability–selectivity trade-off for efficient CO₂ capture. Full article

(This article belongs to the Special Issue Functional Composite Membranes: Properties and Applications)

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35 pages, 4858 KB

Open AccessArticle

An Algae Cultivator Coupled with a Hybrid Photosynthetic–Air-Cathode Microbial Fuel Cell with Ceramic Membrane Interface

by Chikashi Sato, Ghazaleh Alikaram, Oluwafemi Oladipupo Kolajo, John Dudgeon, Rebecca Hazard, Wilgince Apollon and Sathish-Kumar Kamaraj

Membranes 2025, 15(10), 295; https://doi.org/10.3390/membranes15100295 - 30 Sep 2025

Viewed by 368

Abstract

Microalgae are promising candidates for renewable biofuel production and nutrient-rich animal feed. Cultivating microalgae using wastewater can lower production costs but often results in biomass contamination and increases downstream processing requirements. This study presents a novel system that integrates an algae cultivator (AC) [...] Read more.

Microalgae are promising candidates for renewable biofuel production and nutrient-rich animal feed. Cultivating microalgae using wastewater can lower production costs but often results in biomass contamination and increases downstream processing requirements. This study presents a novel system that integrates an algae cultivator (AC) with a single-chamber microbial fuel cell (MFC) equipped with photosynthetic and air-cathode functionalities, separated by a ceramic membrane. The system enables the generation of electricity and production of clean microalgae biomass concurrently, in both light and dark conditions, utilizing wastewater as a nutrient source and renewable energy. The MFC chamber was filled with simulated potato processing wastewater, while the AC chamber contained microalgae Chlorella vulgaris in a growth medium. The ceramic membrane allowed nutrient diffusion while preventing direct contact between algae and wastewater. This design effectively supported algal growth and produced uncontaminated, harvestable biomass. At the same time, larger particulates and undesirable substances were retained in the MFC. The system can be operated with synergy between the MFC and AC systems, reducing operational and pretreatment costs. Overall, this hybrid design highlights a sustainable pathway for integrating electricity generation, nutrient recovery, and algae-based biofuel feedstock production, with improved economic feasibility due to high-quality biomass cultivation and the ability to operate continuously under variable lighting conditions. Full article

(This article belongs to the Special Issue Design, Synthesis, and Application of Inorganic Membranes)

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24 pages, 5442 KB

Open AccessArticle

Electro-Spun Waste Polystyrene/Steel Slag Composite Membrane for Water Desalination: Modelling and Photothermal Activity Evaluation

by Salma Tarek Ghaly, Usama Nour Eldemerdash and Ahmed H. El-Shazly

Membranes 2025, 15(10), 294; https://doi.org/10.3390/membranes15100294 - 28 Sep 2025

Viewed by 936

Abstract

Plastic waste and industrial residues like steel slag pose significant environmental challenges, with limited recycling solutions. This study investigates a sustainable approach by repurposing waste polystyrene and steel slag into composite membranes via electrospinning for membrane distillation applications. Steel slag incorporation enhanced membrane [...] Read more.

Plastic waste and industrial residues like steel slag pose significant environmental challenges, with limited recycling solutions. This study investigates a sustainable approach by repurposing waste polystyrene and steel slag into composite membranes via electrospinning for membrane distillation applications. Steel slag incorporation enhanced membrane porosity, hydrophobicity, and thermal stability, with process optimization performed through response surface methodology by varying slag content (0–10 wt%), voltage (15–30 kV), and feed rate (0.18–10 mL·h⁻¹). Optimized membranes achieved a reduced fiber diameter (1.172 µm), high porosity (82.3%), and superior hydrophobicity (contact angle 102.2°). Mechanical performance improved with a 12% increase in tensile strength and a threefold rise in liquid entry pressure over pure polystyrene membranes, indicating greater durability and wetting resistance. In direct contact membrane distillation, water flux improved by 15% while maintaining salt rejection above 98%. Under photothermal membrane distillation, evaporation rates rose by 69% and solar-to-thermal conversion efficiency by 60% compared to standard PVDF membranes. These results demonstrate the feasibility of transforming waste materials into high-performance, durable membranes, offering a scalable and eco-friendly solution for sustainable desalination. Full article

(This article belongs to the Section Membrane Applications for Water Treatment)

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26 pages, 1865 KB

Open AccessReview

Composite Membranes Based on MXene and Nanocellulose for Water Purification: Structure, Efficiency, and Future Prospects

by Madina Suleimenova, Aidana Tabynbayeva, Kainaubek Toshtay and Zhandos Tauanov

Membranes 2025, 15(10), 293; https://doi.org/10.3390/membranes15100293 - 26 Sep 2025

Viewed by 670

Abstract

The development of efficient and environmentally sustainable membrane materials is essential for advancing water purification technologies. This review examines composite membranes that combine the properties of MXene and nanocellulose, focusing on their structural features, functional characteristics, and potential advantages in water treatment applications. [...] Read more.

The development of efficient and environmentally sustainable membrane materials is essential for advancing water purification technologies. This review examines composite membranes that combine the properties of MXene and nanocellulose, focusing on their structural features, functional characteristics, and potential advantages in water treatment applications. Nanocellulose provides a biodegradable, renewable matrix with abundant surface functional groups, while MXene offers high hydrophilicity, electrical conductivity, and adsorption capacity. Based on a critical evaluation of published studies, the review outlines various fabrication strategies, discusses key factors affecting membrane performance—including morphology, surface modification, and interfacial interactions—and highlights the synergistic effects between the two components. The article systematizes current approaches to designing MXene/nanocellulose membranes and establishes a foundation for future scientific and technological development in this field. Full article

(This article belongs to the Section Membrane Applications for Water Treatment)

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20 pages, 3339 KB

Open AccessArticle

Green and Sustainable Clay Ceramic Membrane Preparation and Application to Textile Wastewater Treatment for Color Removal

by Jamila Bahrouni, Afef Attia, Fatima Zohra Elberrichi, Lasâad Dammak, Lassaad Baklouti, Mohamed-Ali Ben Aissa, Raja Ben Amar and Andre Deratani

Membranes 2025, 15(10), 292; https://doi.org/10.3390/membranes15100292 - 26 Sep 2025

Viewed by 488

Abstract

Ceramic membrane technology plays an important role in water and wastewater treatment. Strategic sourcing of various natural mineral resources has contributed to developing low-cost ceramic membranes. The combination with calcination of inorganic and organic wastes from domestic and agricultural activities results in fully [...] Read more.

Ceramic membrane technology plays an important role in water and wastewater treatment. Strategic sourcing of various natural mineral resources has contributed to developing low-cost ceramic membranes. The combination with calcination of inorganic and organic wastes from domestic and agricultural activities results in fully sustainable ceramic membrane materials. In this work, ceramic membranes were developed using 96% clay, 2% almond shells and 2% lime. Sintering at 900, 950, and 1000 °C enabled the production of membranes (MK-900, MK-950, and MK-1000) in a clean, simple, and cost-effective manner. The average pore diameter and porosity decreased slightly from 44 to 42 nm and from about 30% to 26% with increasing sintering temperature, while the flexural strength increased from 25 to 40 MPa. The pure water permeability was 68 and 59 L·m⁻²·h⁻¹·bar⁻¹ for MK-900 and MK-950, respectively. Effective color (as Indigo blue) removal of 78% and 92% was observed for MK-900 and MK-950, respectively. More than 90% of the initial permeability was recovered after three cycles of dye filtration using water backwashing at each stage, indicating good fouling resistance of the prepared membranes. Full article

(This article belongs to the Special Issue Green Membrane Technologies: Advancements in Materials and Energy Efficiency for Water Treatment)

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22 pages, 3810 KB

Open AccessArticle

Nanofibrous Polymer Filters for Removal of Metal Oxide Nanoparticles from Industrial Processes

by Andrzej Krupa, Arkadiusz Tomasz Sobczyk and Anatol Jaworek

Membranes 2025, 15(10), 291; https://doi.org/10.3390/membranes15100291 - 25 Sep 2025

Viewed by 320

Abstract

Filtration of submicron particles and nanoparticles is an important problem in nano-industry and in air conditioning and ventilation systems. The presence of submicron particles comprising fungal spores, bacteria, viruses, microplastic, and tobacco-smoke tar in ambient air is a severe problem in air conditioning [...] Read more.

Filtration of submicron particles and nanoparticles is an important problem in nano-industry and in air conditioning and ventilation systems. The presence of submicron particles comprising fungal spores, bacteria, viruses, microplastic, and tobacco-smoke tar in ambient air is a severe problem in air conditioning systems. Many nanotechnology material processes used for catalyst, solar cells, gas sensors, energy storage devices, anti-corrosion and hydrophobic surface coating, optical glasses, ceramics, nanocomposite membranes, textiles, and cosmetics production also generate various types of nanoparticles, which can retain in a conveying gas released into the atmosphere. Particles in this size range are particularly difficult to remove from the air by conventional methods, e.g., electrostatic precipitators, conventional filters, or cyclones. For these reasons, nanofibrous filters produced by electrospinning were developed to remove fine particles from the post-processing gases. The physical basis of electrospinning used for nanofilters production is an employment of electrical forces to create a tangential stress on the surface of a viscous liquid jet, usually a polymer solution, flowing out from a capillary nozzle. The paper presents results for investigation of the filtration process of metal oxide nanoparticles: TiO₂, MgO, and Al₂O₃ by electrospun nanofibrous filter. The filter was produced from polyvinylidene fluoride (PVDF). The concentration of polymer dissolved in dimethylacetamide (DMAC) and acetone mixture was 15 wt.%. The flow rate of polymer solution was 1 mL/h. The nanoparticle aerosol was produced by the atomization of a suspension of these nanoparticles in a solvent (methanol) using an aerosol generator. The experimental results presented in this paper show that nanofilters made of PVDF with surface density of 13 g/m² have a high filtration efficiency for nano- and microparticles, larger than 90%. The gas flow rate through the channel was set to 960 and 670 l/min. The novelty of this paper was the investigation of air filtration from various types of nanoparticles produced by different nanotechnology processes by nanofibrous filters and studies of the morphology of nanoparticle deposited onto the nanofibers. Full article

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15 pages, 2647 KB

Open AccessArticle

6FDA-Based Co-Polyimide Membranes Incorporating Modulated MOF-808s for Olefin/Paraffin Gas Separations

by Harun Kulak, Lore Hannes and Ivo F. J. Vankelecom

Membranes 2025, 15(10), 290; https://doi.org/10.3390/membranes15100290 - 25 Sep 2025

Viewed by 546

Abstract

MOF-808 was synthesized using different (perfluoro)carboxylic acid modulators, including acetic acid (AA), butyric acid (BA), trifluoroacetic acid (TFAA) and heptafluorobutyric acid (HFBA). These samples were incorporated into co-polyimide 6FDA-DAM:DABA (6FDD), and the performance of the resulting MMMs was assessed for C₂ and [...] Read more.

MOF-808 was synthesized using different (perfluoro)carboxylic acid modulators, including acetic acid (AA), butyric acid (BA), trifluoroacetic acid (TFAA) and heptafluorobutyric acid (HFBA). These samples were incorporated into co-polyimide 6FDA-DAM:DABA (6FDD), and the performance of the resulting MMMs was assessed for C₂ and C₃ olefin/paraffin separation. Enhanced permeability was observed for both C₂H₄/C₂H₆ and C₃H₆/C₃H₈ mixtures thanks to the introduced porosity upon filler incorporation in all cases. Due to the large pore size of MOF-808, diffusion-selective permeation through the polymer phase of the MMMs determined the eventual selectivity for C2 gases, leading to separation factors similar to that of the unfilled 6FDD membrane. For C₃H₆/C₃H₈ separation, the incorporation of fluorinated MOFs significantly improved separation performance, unlike their non-fluorinated counterparts. The unfilled 6FDD membrane exhibited a C₃H₆/C₃H₈ separation factor of 7.4 with a C₃H₆ permeability of 22 Barrer, while the incorporation of MOF-808-TFAA and MOF-808-HFBA led to C₃H₆/C₃H₈ separation factors of 13.1 and 13.5 with corresponding improved C₃H₆ permeabilities of 42 Barrer and 33 Barrer, respectively. Considering that these MMMs showed C₃H₆ permeabilities similar to those of MMMs containing their non-fluorinated MOF counterparts that exhibited no enhancement in membrane selectivity, the improved C₃H₆/C₃H₈ separation factor was attributed to the preferential adsorption of C₃H₈ over C3H6 on the fluorinated MOFs, acting as a trap for C₃H₈ and reducing its diffusivity. These results highlight the significance of matching the permeation characteristics of the selected polymer-filler pair on MMM performance for different gas pairs. Full article

(This article belongs to the Section Membrane Applications for Gas Separation)

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17 pages, 6943 KB

Open AccessArticle

Flux and Fouling Behavior of Graphene Oxide-Polyphenylsulfone Ultrafiltration Membranes Incorporating ZIF-67/ZIF-8 Fillers

by Azile Nqombolo, Thollwana Andretta Makhetha, Richard Motlhaletsi Moutloali and Philiswa Nosizo Nomngongo

Membranes 2025, 15(10), 289; https://doi.org/10.3390/membranes15100289 - 25 Sep 2025

Viewed by 511

Abstract

Wider adoption of membrane technology is hindered by fouling and flux/rejection challenges. Recent practice in mitigating these is to incorporate hydrophilic and porous fillers. Herein the addition of hydrophilic graphene oxide (GO) in conjunction with porous mixed ZIFs (ZIF-67/ZIF-8) crystallites were used as [...] Read more.

Wider adoption of membrane technology is hindered by fouling and flux/rejection challenges. Recent practice in mitigating these is to incorporate hydrophilic and porous fillers. Herein the addition of hydrophilic graphene oxide (GO) in conjunction with porous mixed ZIFs (ZIF-67/ZIF-8) crystallites were used as inorganic fillers in the preparation of polyphenylenesulfone (PPSU) ultrafiltration (UF) membranes. The morphology of the resultant composite membranes was assessed using atomic force microscopy (AFM) and scanning electron microscopy (SEM) whilst surface hydrophilicity through water contact angle. The pure water flux (PWF) and membrane permeability were found to increase with increasing filler content. This was attributed to the combined hydrophilicity of GO and porous structure of the ZIF materials because of increasing alternative water pathways in the membrane matrix with increasing filler content. Furthermore, the increase in the ZIF component led to increasing bovine serum albumin (BSA) fouling resistance as demonstrated by increasing fouling recovery ratio (FRR). The dye rejection was due to a combination of electrostatic interaction between the fillers and the dyes as well as size exclusion. The chemical interactions between the ZIFs and the dyes resulted in slightly different rejection profiles for the smaller dyes, the cationic methylene blue being rejected less efficiently than the anionic methyl orange, potentially leading to their separation. The larger anionic dye, Congo red was rejected predominately through size exclusion. Full article

(This article belongs to the Special Issue Design, Preparation and Application of Nanocomposite Membranes)

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17 pages, 38922 KB

Open AccessArticle

A New Method for Preparing Cross-Sections of Polymer Composite Membranes for TEM Characterization by Substrate Stripping and Double-Orientation Embedding

by Hongyun Ren, Zixing Zhang, Yi Li, Shulan Liu and Xian Zhang

Membranes 2025, 15(10), 288; https://doi.org/10.3390/membranes15100288 - 24 Sep 2025

Viewed by 477

Abstract

Membrane technology plays a vital role in environmental protection, chemical industry, and pharmaceuticals, where understanding the “structure-property” relationship of composite membranes through transmission electron microscopy (TEM) is crucial. Conventional ultramicrotomy methods for preparing ultra-thin sections of polymer composite membranes often result in significant [...] Read more.

Membrane technology plays a vital role in environmental protection, chemical industry, and pharmaceuticals, where understanding the “structure-property” relationship of composite membranes through transmission electron microscopy (TEM) is crucial. Conventional ultramicrotomy methods for preparing ultra-thin sections of polymer composite membranes often result in significant damage and non-uniform thickness due to interference from non-woven substrates. In this study, we developed an innovative substrate stripping and double-orientation embedding technique that overcomes these limitations. A special embedding device was designed to facilitate the preparation of polymeric membrane cross-sections for TEM analysis. The device incorporates dual functionality, enabling both non-woven substrate detachment and bidirectional alignment of functional membrane layers. TEM characterization showed that the ultra-thin sections of membrane cross-sections prepared using the improved method were damage-free (0% damage rate), had uniform thickness, and showed distinct structural clarity. This method addressed three major challenges: (i) substrate-induced section damage, (ii) orientation deviation, and (iii) interlayer separation. This advancement provides researchers with a reliable tool for accurate cross-sectional analysis of composite membranes, facilitating deeper insights into membrane microstructure-performance relationships. Full article

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15 pages, 42656 KB

Open AccessArticle

Glutaraldehyde Cross-Linked MXene-Nanocellulose Membrane for Efficient Dye/Salt Separation

by Yu Zhang and Ming Qiu

Membranes 2025, 15(10), 287; https://doi.org/10.3390/membranes15100287 - 24 Sep 2025

Viewed by 456

Abstract

This study proposes a novel approach for preparing a laminated carbides and nitrides (MXene) membrane with loose nanochannels by intercalating cellulose nanocrystal (CNC) and cross-linking with glutaraldehyde. The interlayer spacing of the MXene membrane can be expanded by one-dimensional CNC, while cross-linking with [...] Read more.

This study proposes a novel approach for preparing a laminated carbides and nitrides (MXene) membrane with loose nanochannels by intercalating cellulose nanocrystal (CNC) and cross-linking with glutaraldehyde. The interlayer spacing of the MXene membrane can be expanded by one-dimensional CNC, while cross-linking with glutaraldehyde enhances the stability of the membrane. The optimized membrane displays a high water permeate flux of 96.8 L m⁻² h⁻¹ (2.1 times higher than MXene membrane) and good selectivity (methyl blue rejection rate: ~99.6%; NaCl rejection rate: <5.0%). This strategy provides a universal way to prepare high-performance two-dimensional membranes. Full article

(This article belongs to the Section Membrane Applications for Water Treatment)

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18 pages, 5588 KB

Open AccessArticle

Double-Crosslinked H-PAN/MoS₂/PEI Composite Nanofiltration Membrane for Ethanol Systems: Fabrication and Dye Separation Performance

by Yixin Zhang, Chunli Liu, Lei Zhu, Xin Zhou, Miaona Wang and Yongqian Shen

Membranes 2025, 15(10), 286; https://doi.org/10.3390/membranes15100286 - 23 Sep 2025

Viewed by 443

Abstract

Organic solvent nanofiltration (OSN) is a promising technology for solute removal from organic media, yet developing membranes with stable separation performance remains challenging. This study presents a solvent-resistant double-crosslinked nanofiltration membrane fabricated via a two-step strategy: preparation of the membrane by the polyion [...] Read more.

Organic solvent nanofiltration (OSN) is a promising technology for solute removal from organic media, yet developing membranes with stable separation performance remains challenging. This study presents a solvent-resistant double-crosslinked nanofiltration membrane fabricated via a two-step strategy: preparation of the membrane by the polyion complexion reaction-assisted non-solvent-induced phase inversion (PIC-assisted NIPS) method and then post-crosslinking with hydrothermal treatment followed by quaternization with 1,3,5-tris(bromomethyl)benzene (TBB). To enhance solvent stability, molybdenum sulfide (MoS₂) nanosheets were incorporated into a hydrolyzed polyacrylonitrile (H-PAN) substrate. The H-PAN/MoS₂/PEI base membrane was fabricated by PIC-assisted NIPS with a polyethylenimine (PEI) aqueous solution as the coagulation bath. The membrane subsequently underwent dual crosslinking comprising hydrothermal treatment and 1,3,5-tris(bromomethyl)benzene (TBB)-mediated quaternization crosslinking, ultimately yielding the H-PAN/MoS₂/PEI (Ther.+TBB QCL) composite membrane. These crosslinking procedures reduced the membrane’s separation skin layer thickness from 64 nm (uncrosslinked) to 41 nm. The resultant membrane effectively separated dyes from ethanol, achieving a rejection rate of 97.0 ± 0.9% for anionic dyes (e.g., Congo Red) and a permeance flux of 23.6 ± 0.2 L·m⁻²·h⁻¹·bar⁻¹ at 0.4 MPa. Furthermore, after 30 days of immersion in ethanol at 25 °C, its flux decay rate was markedly lower than that of a non-crosslinked control membrane. The enhanced separation performance and stability are attributed to the thermal crosslinking promoting amide bond formation and the TBB crosslinking introducing quaternary ammonium groups. This double-crosslinking strategy offers a promising approach for preparing high-performance OSN membranes. Full article

(This article belongs to the Special Issue Nanofiltration Membranes: Preparation, Structure and Separation Performance)

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22 pages, 3747 KB

Open AccessArticle

Recycled Polystyrene as a Sustainable Material for Hollow Fiber Membranes in Dye Filtration

by Mauricio Huhn-Ibarra, Libia Madai Itza-Uitzil, Marcial Yam-Cervantes, Abigail González-Díaz, Fernando José Zapata-Catzin, Javier Ivan Cauich-Cupul, Manuel Aguilar-Vega and Maria Ortencia González-Díaz

Membranes 2025, 15(10), 285; https://doi.org/10.3390/membranes15100285 - 23 Sep 2025

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Abstract

Expanded polystyrene (EPS) waste was chemically modified by sulfonation to obtain sulfonated EPS (sEPS), which was subsequently blended with virgin polyphenylsulfone (PPSU) at concentrations ranging from 10 to 50% to elaborate hollow fiber membranes for dye removal. The membranes were elaborated by non-solvent-induced [...] Read more.

Expanded polystyrene (EPS) waste was chemically modified by sulfonation to obtain sulfonated EPS (sEPS), which was subsequently blended with virgin polyphenylsulfone (PPSU) at concentrations ranging from 10 to 50% to elaborate hollow fiber membranes for dye removal. The membranes were elaborated by non-solvent-induced phase separation and characterized by scanning electron microscopy, mechanical properties, antifouling, water flux measurements, and dye rejection performance. Scanning electron microscopy images of PPSU/sEPS blends showed well-defined membrane cross-sections with no polymer segregation up to 30% recycled EPS content, indicating improved compatibility due to EPS sulfonation. The HFMs present mean pore radii ranging from 4.2 ± 0.5 to 11.1 ± 1.0 nm with porosity up to 80%. Water flux improved significantly from 3.1 to 21.2 L m⁻² h⁻¹ at 2 bar as sEPS content increased. Dye rejection performance was promising, with Reactive Black 5 rejection ranging from 77% to 99%. The 80/20s PPSU/sEPS membrane showed the highest Reactive Black 5 rejection at 98.3% and revealed a 70.3% rejection in a 24 h dye mixture test. Furthermore, the 70/30s displayed superior anti-fouling properties, achieving a 99.3% flux recovery ratio in a xanthan gum solution at 2 bar. This study demonstrates a novel approach to transform EPS waste into high-performance hollow fiber membrane with competitive antifouling and dye separation properties. Full article

(This article belongs to the Special Issue Recent Advances in Polymeric Membranes—Preparation and Applications (2nd Edition))

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Membranes, Volume 15, Issue 10 (October 2025) – 29 articles

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