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Adsorption of Myelin Basic Protein on Model Myelin Membranes Reveals Weakening of van der Waals Interactions in a Lipid Ratio-Dependent Manner
Improved Antimicrobial Properties of White Wastewater Protein Hydrolysate Through Electrodialysis with an Ultrafiltration Membrane (EDUF)
Review of Hollow Fiber Membranes for Gas Separation: Exploring Fundamentals and Recent Advancements
Amyloid β 1-42 Can Form Ion Channels as Small as Gramicidin in Model Lipid Membranes
Valorization of Anaerobic Liquid Digestates Through Membrane Processing and Struvite Recovery—The Case of Dairy Effluents

Journal Description

Membranes

Membranes is an international, peer-reviewed, open access journal, published monthly online by MDPI, covers the broad aspects of the science and technology of both biological and non-biological membranes. European Membrane Society (EMS), Membrane Society of Australasia (MSA) and Polish Membrane Society (PTMem) are affiliated with Membranes and their members receive discounts on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Ei Compendex, PubMed, PMC, CAPlus / SciFinder, Inspec, and other databases.
Journal Rank: JCR - Q2 (Polymer Science) / CiteScore - Q1 (Chemical Engineering (miscellaneous))
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 17 days after submission; acceptance to publication is undertaken in 3.5 days (median values for papers published in this journal in the first half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 3.6 (2024); 5-Year Impact Factor: 3.9 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2077-0375

Latest Articles

12 pages, 892 KB

Open AccessArticle

Membrane Technology for the Valorization of Wood Vinegar from Grape Pomace Pyrolysis

by Alexandre Giacobbo, Amanda de Sampaio Callegari, Mateus Torres Nazari, Valdecir Ferrari, Tania Maria Basegio, Carlos Pérez Bergmann, Marco Antônio Siqueira Rodrigues, Maria Norberta de Pinho and Andréa Moura Bernardes

Membranes 2025, 15(11), 335; https://doi.org/10.3390/membranes15110335 - 5 Nov 2025

The valorization of wood vinegar from biomass pyrolysis has been a significant research subject in recent years, but further studies to reduce its phytotoxicity and improve agricultural applications are still needed. This study investigates the application of ultrafiltration and nanofiltration membranes in treating [...] Read more.

The valorization of wood vinegar from biomass pyrolysis has been a significant research subject in recent years, but further studies to reduce its phytotoxicity and improve agricultural applications are still needed. This study investigates the application of ultrafiltration and nanofiltration membranes in treating the wood vinegar from grape pomace pyrolysis, aiming to valorize it. Wood vinegar treated with nanofiltration (NF270 membrane) and diluted 100 times acted as a root growth inducer in cucumber seeds, achieving a germination index of 145%. This interesting result suggests that nanofiltration is emerging as a promising technology for enhancing the value of wood vinegar, while also promoting sustainability and the circular economy in the agro-industrial sector. Full article

(This article belongs to the Special Issue Advanced Membrane Technologies for the Treatment of Industrial Wastewater and Emerging Contaminants: Challenges and Innovations)

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16 pages, 5579 KB

Open AccessArticle

Microscopic Exploration of Water Permeation and Ion Rejection for Edge Amine-Functionalized GO Nanoslits

by Yinfeng Pei, Wenjin Li and Xiaoning Yang

Membranes 2025, 15(11), 334; https://doi.org/10.3390/membranes15110334 - 4 Nov 2025

Layered graphene oxide (GO) has emerged as an ideal membrane structure for water desalination. In GO-stacked structures, the slit gaps between GO nanosheets can serve as critical pathways for molecule permeation. Exploring the permeation mechanisms of functionalized GO nanoslits is critical for improving [...] Read more.

Layered graphene oxide (GO) has emerged as an ideal membrane structure for water desalination. In GO-stacked structures, the slit gaps between GO nanosheets can serve as critical pathways for molecule permeation. Exploring the permeation mechanisms of functionalized GO nanoslits is critical for improving the separation performance. Herein, molecular simulations were performed to investigate the water permeation and ion rejection for six types of ionic solutions by considering edge-amino functionalized GO (NGO) slit membranes. The NGO slit exhibits higher ion retention while maintaining reasonable water permeability. Edge amine groups can interact strongly with water molecules and immobilize ions, thus enhancing ion rejection. The thermodynamic free energy for ion passing was simulated to explain the unique ion rejection mechanism of amine-functionalized GO slits. The thermodynamic barrier for ion rejection can be considered as the delicate combination of the ion dehydration effect and the slit-generated attraction. The ion dehydration accounts for a repulsive contribution, which is the controlling portion in governing the free-energy profile. Overall, our work is important and valuable for the development and design of new-type layered GO membranes. Full article

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

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19 pages, 9109 KB

Open AccessArticle

High Current Induction for the Effective Bending in Ionic Polymer Metal Composite

by Hirohisa Tamagawa, Rintaro Fujiwara and Iori Kojima

Membranes 2025, 15(11), 333; https://doi.org/10.3390/membranes15110333 - 3 Nov 2025

Ionic Polymer–Metal Composites (IPMCs) are promising electroactive polymers for artificial muscles, as their bending motion depends on the induced current—greater current leads to greater bending. While conventional IPMCs use cation exchange membranes, this study explores IPMCs containing both immobile positive and negative charges, [...] Read more.

Ionic Polymer–Metal Composites (IPMCs) are promising electroactive polymers for artificial muscles, as their bending motion depends on the induced current—greater current leads to greater bending. While conventional IPMCs use cation exchange membranes, this study explores IPMCs containing both immobile positive and negative charges, resembling real muscle tissue. Considering that an IPMC consists of an ion-exchange membrane sandwiched between two thin metal coatings serving as electrodes, we found that (i) improving the contact between the metal coating (electrode) and the ion exchange membrane is an effective way to enhance current induction. Achieving tight electrode membrane contact can drastically increase the induced current by up to four orders of magnitude, and even samples that previously showed no current induction can exhibit measurable current after improvement. (ii) Doping with mobile ions is another well-known method of enhancing IPMC current. However, we found that simply introducing dopants into the IPMC body is not effective; the choice of dopant is crucial. In this work, we identified silver ions as effective dopants for enhancing current induction. Considering that real muscles consume oxygen for activation, we also attempted to supply oxygen to the IPMC surface. We confirmed that (iii) supplying oxygen to the IPMC surface is another effective means of enhancing current induction, which in turn resulted in a significant improvement in IPMC bending performance. Full article

(This article belongs to the Section Membrane Applications for Other Areas)

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31 pages, 2913 KB

Open AccessReview

Mitigation Techniques of Membranes’ Biofouling in Bioelectrochemical Cells (BEC Cells): Recent Advances

by Shatha Alyazouri, Muhammad Tawalbeh and Amani Al-Othman

Membranes 2025, 15(11), 332; https://doi.org/10.3390/membranes15110332 - 1 Nov 2025

Biofouling remains a critical challenge in bioelectrochemical cells (BECs), hindering their efficiency and performance. This research article reviews advances in biofouling mitigation techniques within BEC systems during the period from 2019 to 2025, focusing on membrane modifications and electro-assisted membrane technologies. Through comprehensive [...] Read more.

Biofouling remains a critical challenge in bioelectrochemical cells (BECs), hindering their efficiency and performance. This research article reviews advances in biofouling mitigation techniques within BEC systems during the period from 2019 to 2025, focusing on membrane modifications and electro-assisted membrane technologies. Through comprehensive analysis, it is revealed that Nafion alternatives, including ceramic membranes and recycled nonwoven fabrics like polypropylene, have emerged as significant contenders due to their combination of low cost and high performance. Additionally, the incorporation of silver, zeolite, and graphene oxide onto membranes has demonstrated efficacy in mitigating biofouling under laboratory conditions. Furthermore, the application of direct current electric fields has shown potential as a chemical-free preventative measure against biofouling in BECs. However, challenges related to long-term stability, scalability, and cost-effectiveness must be addressed for widespread adoption. Full article

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

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13 pages, 3161 KB

Open AccessArticle

Optimizing Pretreatment Parameters for Enhanced Phosphorus Recovery from High-Phosphorus Wastewater via Nanofiltration

by Guodong Wu, Lu Wang, Bing Qin, Fanbin Meng, Yonghu He, Xin Wang, Jing Bai, Jingpeng Zhang and Yuanhao Wang

Membranes 2025, 15(11), 331; https://doi.org/10.3390/membranes15110331 - 31 Oct 2025

The effects of pretreatment pH value, operating pressure, and concentration factors on the performance of nanofiltration membrane concentration and the recovery of phosphorus-containing wastewater were systematically studied. A novel pretreatment strategy using solid sodium hydroxide was developed to adjust the feed solution pH, [...] Read more.

The effects of pretreatment pH value, operating pressure, and concentration factors on the performance of nanofiltration membrane concentration and the recovery of phosphorus-containing wastewater were systematically studied. A novel pretreatment strategy using solid sodium hydroxide was developed to adjust the feed solution pH, achieving optimal solid removal and minimized conductivity at pH = 5. Unlike conventional calcium-based methods, this approach avoids excessive chemical sludge formation and mitigates membrane scaling, enhancing system stability. Experimental results demonstrate that both phosphorus rejection and desalination efficiency are significantly influenced by feed solution pH, operating pressure, and concentration ratio. While increasing pH and pressure improve total phosphorus (TP) rejection and desalination rates, these benefits are accompanied by reduced membrane flux due to elevated osmotic pressure and intensified concentration polarization. The membrane exhibited optimal performance at a feed pH of 5 and an operating pressure of 3 MPa, with sustained flux and enhanced separation efficiency. Under these conditions, when the wastewater was concentrated fivefold at 25 °C, the TP rejection rate and desalination efficiency reached 92.9% and 91.8%, respectively. Full article

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15 pages, 2918 KB

Open AccessArticle

Fouling Mitigation of PVDF Membrane Induced by Sodium Dodecyl Sulfate (SDS)-TiO₂ Micelles

by Jie Zhang, Shiying Bo, Chunhua Wang, Zicong Jian, Yuehuan Chu, Si Qiu, Hongyan Chen, Qiancheng Xiong, Xiaofang Yang, Zicheng Xiao and Guocong Liu

Membranes 2025, 15(11), 330; https://doi.org/10.3390/membranes15110330 - 30 Oct 2025

As a favorable hydrophilic additive for antifouling modification of polyvinylidene fluoride (PVDF) membrane, titanium dioxide (TiO₂) nanoparticles have been applied for years. Sodium dodecyl sulfonate (SDS), a representative anionic surfactant, has been proven to benefit the dispersion of nano-TiO₂ via [...] Read more.

As a favorable hydrophilic additive for antifouling modification of polyvinylidene fluoride (PVDF) membrane, titanium dioxide (TiO₂) nanoparticles have been applied for years. Sodium dodecyl sulfonate (SDS), a representative anionic surfactant, has been proven to benefit the dispersion of nano-TiO₂ via an electro-spatial stabilizing mechanism. In this study, various proportionally SDS-functionalized TiO₂ nanoparticles were adopted to modify PVDF membrane. Dispersion and stability of SDS-functionalized TiO₂ nanoparticles in casting solutions were evaluated by multiple light scattering technology. The properties and antifouling performance of PVDF/SDS-TiO₂ composite membranes were assessed. The uniformity of surface pores as well as structures on cross-section morphologies was modified. The finger-like structure of PVDF/SDS-TiO₂ composite membrane was adequately developed at the SDS/TiO₂ mass ratio of 1:1. The improved antifouling performance was corroborated by the increasing free energy of cohesion and adhesion as well as the interaction energy barrier between membrane surfaces and approaching foulants assessed by classic extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory, the low flux decline during bovine serum albumin (BSA) solution filtration process, and the high critical flux (38 L/(m²·h·kPa)) in membrane bioreactor. This study exploits a promising way to modify PVDF membrane applicable to the wastewater treatment field. Full article

(This article belongs to the Special Issue Membrane Fouling Control: Mechanism, Properties, and Applications)

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24 pages, 815 KB

Open AccessReview

Recent Advances in Polymeric Membrane Integration for Organic Solvent Mixtures Separation: Mini-Review

by Abdellah Halloub and Wojciech Kujawski

Membranes 2025, 15(11), 329; https://doi.org/10.3390/membranes15110329 - 30 Oct 2025

Membrane technology offers considerable potential for enhancing or partially replacing conventional separation techniques, which could eventually lead to substantial energy savings. This review focuses on recent advancements in membrane separation technologies including organic solvent pervaporation (OSPV), organic solvent reverse osmosis (OSRO), organic solvent [...] Read more.

Membrane technology offers considerable potential for enhancing or partially replacing conventional separation techniques, which could eventually lead to substantial energy savings. This review focuses on recent advancements in membrane separation technologies including organic solvent pervaporation (OSPV), organic solvent reverse osmosis (OSRO), organic solvent nanofiltration (OSN), and organic solvent ultrafiltration (OSUF) that are increasingly vital in the pharmaceutical, biochemical, and petrochemical industries. Although hybrid and inorganic membranes exhibit promising performance, polymeric membranes provide advantages in scalability and processability. The development of materials capable of operating under demanding conditions that include exposure to organic solvents, high temperatures, extreme pH levels, and oxidative environments remains critical. Here, we examine recent innovations in membrane materials and their integration into organic solvent systems. Key challenges, including material swelling, fouling, and scaling, are discussed, along with recent strategies to address these issues. Finally, we identify emerging research directions that could drive further progress in membrane technology for organic media applications. Full article

(This article belongs to the Collection Featured Reviews in Membrane Science)

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16 pages, 3822 KB

Open AccessArticle

Ergothioneine Thione Spontaneously Binds to and Detaches from the Membrane Interphase

by José Villalaín

Membranes 2025, 15(11), 328; https://doi.org/10.3390/membranes15110328 - 29 Oct 2025

Ergothioneine is a potent non-toxic and very stable antioxidant which is synthesized by fungi, algae, and bacteria but not animals or higher plants. Ergothioneine has been widely used in cosmetics; dietary supplements; and medicine to treat diabetes, cancer, as well as cardiovascular, neurodegenerative, [...] Read more.

Ergothioneine is a potent non-toxic and very stable antioxidant which is synthesized by fungi, algae, and bacteria but not animals or higher plants. Ergothioneine has been widely used in cosmetics; dietary supplements; and medicine to treat diabetes, cancer, as well as cardiovascular, neurodegenerative, and liver diseases. Ergothioneine presents two tautomeric forms: thione, the majoritarian and more stable form (ERGO), and thiol (ERGT). Ergothioneine cannot cross cell membranes, and human cells rely on a specific transporter, OCTN1, to transport ingested ERGO to different parts of the body. Ergothioneine is very hydrophilic, and it is supposed to act at the water level but not at the membrane one. In this work, I studied the interaction of ERGO and ERGT with a complex biomembrane using molecular dynamics (MD). MD suggests that ERGO, but not ERGT, inserts spontaneously into the membrane interphase and can move from the membrane interphase to the water phase and vice versa, and no oligomerization was observed. Furthermore, ERGO, when inserted in the membrane, does not alter the hydrocarbon chain order. Therefore, ERGO (the thione form of ergothioneine), but not ERGT (the thiol form), might act at both the water and membrane interphase levels. Full article

(This article belongs to the Section Biological Membranes)

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12 pages, 2322 KB

Open AccessArticle

Engineering Thermal Cross-Linking in Nanofiltration Membranes for Efficient Nicotine Extraction from Tobacco Extract

by He Du, Xinyuan Wang, Baodan Na, Yajun Ye, Yuemei Qiao, Linda Li, Ye Tian, Xiaoping Ning, Zhigang Wang, Xingquan Zhao and Chen Chen

Membranes 2025, 15(11), 327; https://doi.org/10.3390/membranes15110327 - 28 Oct 2025

Tobacco extract contains numerous valuable components, among which nicotine possesses significant potential for high-value applications despite its well-known health risks. However, the efficient extraction of nicotine is challenging due to the complex composition of tobacco extracts and the limitations of conventional separation techniques. [...] Read more.

Tobacco extract contains numerous valuable components, among which nicotine possesses significant potential for high-value applications despite its well-known health risks. However, the efficient extraction of nicotine is challenging due to the complex composition of tobacco extracts and the limitations of conventional separation techniques. In this work, an integrally asymmetric nanofiltration membrane was developed via thermal cross-linking for highly efficient nicotine separation. A poly(aryl ether ketone) (PEK)-based ultrafiltration membrane was first prepared via non-solvent induced phase separation (NIPS), followed by controlled thermal cross-linking to tailor the membrane pore size toward the molecular weight of nicotine. To mitigate pore collapse and enhance flux, TiO₂ nanoparticles were incorporated in situ through a sol–gel method. The resulting thermally cross-linked membrane exhibited a molecular weight cut-off of ~180 Da, a nicotine rejection rate of 93.2%, and a permeation flux of 143 L/(m²·h)—representing a 259% increase over the control membrane. Moreover, the thermally cross-linked membranes demonstrated exceptional chemical stability in various organic solvents and extreme pH conditions. This work offers a feasible and sustainable strategy for fabric high-performance nanofiltration membranes for the targeted extraction of bioactive molecules from complex plant extracts. Full article

(This article belongs to the Special Issue Applications of Membrane Filtration and Separation)

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12 pages, 2457 KB

Open AccessArticle

Enhancing Yellow Pea Protein Extraction and Purification Through Ultrafiltration

by Muhammad Nurdarwis Bin Anuar and Jian Zuo

Membranes 2025, 15(11), 326; https://doi.org/10.3390/membranes15110326 - 28 Oct 2025

The growing demand for sustainable, high-quality plant-based proteins has increased the need for efficient extraction and purification methods for yellow pea protein (Pisum sativum L.). Conventional techniques, such as isoelectric precipitation (IEP) and wet fractionation, often result in moderate protein recovery (50–70%), [...] Read more.

The growing demand for sustainable, high-quality plant-based proteins has increased the need for efficient extraction and purification methods for yellow pea protein (Pisum sativum L.). Conventional techniques, such as isoelectric precipitation (IEP) and wet fractionation, often result in moderate protein recovery (50–70%), reduced functionality, and high water consumption. This study evaluates ultrafiltration (UF) as a mild, membrane-based alternative for yellow pea protein extraction. Under optimized conditions, UF achieved protein recovery above 85% while maintaining high solubility (>90%) and emulsification capacity. Additionally, incorporating water recycling into the UF process reduced total water use by up to 60%. These results demonstrate that UF offers a more efficient and environmentally sustainable approach for producing functional yellow pea protein compared with traditional methods. Full article

(This article belongs to the Special Issue Membrane Applications for Molecular Purification)

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15 pages, 1477 KB

Open AccessArticle

Microwave-Assisted Syntheses of 1-Acetyl 2-Methylbenzimidazole Sodium Bisulfate pH-Responsive Ionic Draw Solute for Forward Osmosis Applications

by Ahmed A. Bhran, Abdelrahman G. Gadallah, Hanaa M. Ali, Sahar S. Ali, Hanaa Gadallah and Rania Sabry

Membranes 2025, 15(11), 325; https://doi.org/10.3390/membranes15110325 - 26 Oct 2025

This work is related to the development of a highly efficient pH-responsive ionic draw solute for forward osmosis applications utilizing microwave-assisted fast heating. This solute is classified as an ionic compound, a sodium salt originating from imidazole, with the scientific acronym 1-acetyl-2-methylbenzimidazole sodium [...] Read more.

This work is related to the development of a highly efficient pH-responsive ionic draw solute for forward osmosis applications utilizing microwave-assisted fast heating. This solute is classified as an ionic compound, a sodium salt originating from imidazole, with the scientific acronym 1-acetyl-2-methylbenzimidazole sodium bisulfate (AMBIM-Na). The synthesized compound was analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as additional physical characteristics. The baseline performance was initially evaluated at various molar concentrations against distilled water as the feed solution (FS). The results indicated that the produced solute exhibits elevated osmotic pressure, resulting in a water flux of up to 130 LMH for a 1 M concentration, coupled with the absence of reverse salt flux. The synthesized AMBIM-Na at a concentration of 1 M was utilized as a draw solution (DS) against synthetic brackish water. The water flux declined progressively with the increase in FS concentration, decreasing from 130 LMH with distilled water to 99, 70, and 41 LMH at NaCl concentrations of 5, 10, and 15 g/L, respectively. The regeneration of the draw solute was assessed using pH adjustment, revealing that 100% regeneration occurs by reducing the pH to 2. Full article

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13 pages, 7189 KB

Open AccessCommunication

Comparative Study on Structural and Transport Properties of SSC and LSC PFSA Ionomers in PEMFCs with Coexistence of O₂ and N₂: Molecular Dynamics Simulation Approach

by Guanghua Wei, Jingjing Huang, Lina Yu, Jinghao Zhou, Jiabin You, Zhu Ling, Shenrong Ye and Junliang Zhang

Membranes 2025, 15(11), 324; https://doi.org/10.3390/membranes15110324 - 22 Oct 2025

Efficient O₂ transport through the ionomer film in cathode catalyst layers (CCLs) is a critical factor for the output performance of proton exchange membrane fuel cells (PEMFCs), yet the molecular mechanisms of gas transport in ionomers remain elusive. Herein, molecular dynamics (MDs) [...] Read more.

Efficient O₂ transport through the ionomer film in cathode catalyst layers (CCLs) is a critical factor for the output performance of proton exchange membrane fuel cells (PEMFCs), yet the molecular mechanisms of gas transport in ionomers remain elusive. Herein, molecular dynamics (MDs) simulations are employed to investigate short-side-chain (SSC) and long-side-chain (LSC) perfluorosulfonic acid (PFSA) ionomers on Pt/C surfaces with the coexistence of O₂/N₂. The results reveal that the side-chain structures significantly modulate the ionomer nanostructures and gas transport. SSC ionomers form compact hydrophobic domains and more interconnected hydrophilic–hydrophobic interfaces, thereby facilitating more efficient O₂ transport pathways than LSC ionomers, particularly at low hydration (λ = 3). At high hydration (λ = 11), swelling of water domains attenuates these structural disparities and becomes the dominant factor governing gas transport. In addition, O₂ diffusion consistently exceeds that of N₂, while the diffusion coefficients of O₂, N₂ and H₃O⁺ become larger at high hydration. Collectively, these findings demonstrate the structural advantages of SSC ionomers in facilitating coupled oxygen and proton transport, offering molecular-level insights to inform the rational design of high-performance PEMFCs. Full article

(This article belongs to the Special Issue Design and Characterization of Proton Exchange Membrane Fuel Cells (PEMFCs))

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16 pages, 2823 KB

Open AccessArticle

Evaluation of End-of-Life Reverse Osmotic Membrane for High-Retention Anaerobic Membrane Bioreactor

by Oriol Morató Torras, Hiren D. Raval, Bianca Zappulla-Sabio, Ignasi Rodriguez-Roda, Hèctor Monclús and Gaetan Blandin

Membranes 2025, 15(11), 323; https://doi.org/10.3390/membranes15110323 - 22 Oct 2025

Following on from a circular economy in water, membrane technologies can play a role in resource recovery and high-quality water production but should also consider membrane industry circularity. Anaerobic membrane bioreactors (AnMBRs) are being used for advanced wastewater treatment, and their applications are [...] Read more.

Following on from a circular economy in water, membrane technologies can play a role in resource recovery and high-quality water production but should also consider membrane industry circularity. Anaerobic membrane bioreactors (AnMBRs) are being used for advanced wastewater treatment, and their applications are growing due to advantages like lower sludge volume, better permeate quality, and the generation of biogas. High-Rejection (HR) AnMBRs retain a higher fraction of dissolved and particulate components to further promote resource recovery and obtain improved effluent quality. With the development of membrane technologies, end-of-life (EOL) membrane recycling is emerging for various applications. The feasibility of transforming EOL Reverse Osmosis (RO) membranes into ultrafiltration (UF)- and nanofiltration (NF)-like membranes and applying these membranes to submerged HR-AnMBR applications was evaluated. A small pilot AnMBR with granular biomass was operated with EOL RO membranes converted to submerged UF- and NF-like membranes and compared to commercial microfiltration (MF) membranes. UF- and NF-like plates were constructed, characterized, and introduced step-by-step into the AnMBR by the substitution of MF plates. A chemical oxygen demand (COD) removal study showed that while 77% removal of COD was possible with MF membranes, improved COD removal (i.e., 81.40% and 88.39%) was achieved using UF-like and NF-like membranes, respectively. Because of the higher retention of salts of the NF-like membrane, the salinity in the membrane bioreactor increased from 1300 to 1680 µS·cm⁻¹ but stabilized quickly and without a negative impact on system performance. Even without cleaning, minimal fouling and flux decline were observed for all tested configurations thanks to the use of granular biomass and low permeation flux. Permeate flux in the case of the NF-like membrane was slightly lower due to the required higher pressure. The present study demonstrated that the EOL-RO membranes may find applications in HR-AnMBRs to achieve superior permeate quality and move toward circular membrane processes. Full article

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12 pages, 3136 KB

Open AccessArticle

Preparation of Polysilsesquioxane-Based RO Membranes with Urea Units for Water Desalination

by Joji Ohshita, Katsuhiro Horata, Toshiki Kaneko, Yohei Adachi and Masakoto Kanezashi

Membranes 2025, 15(10), 322; https://doi.org/10.3390/membranes15100322 - 20 Oct 2025

Seawater and brackish water desalination using membranes is anticipated to offer a simple and effective solution to the global water shortage, and polysilsesquioxane (PSQ) is expected to be the base material for robust reverse osmosis (RO) membranes for water desalination. Hydroxyethylurea-containing PSQ-based RO [...] Read more.

Seawater and brackish water desalination using membranes is anticipated to offer a simple and effective solution to the global water shortage, and polysilsesquioxane (PSQ) is expected to be the base material for robust reverse osmosis (RO) membranes for water desalination. Hydroxyethylurea-containing PSQ-based RO membranes for water desalination have recently been developed via a sol–gel process. Although these membranes showed high performance, achieving a water permeability of 1.86 × 10⁻¹² m³ m⁻²s⁻¹Pa⁻¹ and an NaCl rejection of 95.9%, the membranes showed limited chlorine resistance and processibility and moderate heat resistance. In this study, three new urea-containing monomers were designed and prepared for RO membrane preparation. The copolymerization of these urea-containing monomer with bis(triethoxysilylpropyl)amine resulted in performance comparable to that of hydroxyethylurea-containing PSQ membranes. The present urea-containing PSQ membranes exhibited enhanced chlorine resistance, with only 1–3% decreases in NaCl rejection, even after 10,000 ppm h exposure to chlorine, together with 3–19% increases in water permeability. Additionally, the presently prepared urea-containing PSQ membranes exhibited improved processability. This study provides a new molecular design for robust and high-performance RO membranes that can be prepared through a simple sol–gel process. Full article

(This article belongs to the Special Issue Membrane-Based Technology for Drinking Water Treatment)

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14 pages, 1370 KB

Open AccessArticle

Mitigating Wetting and Scaling in Air Gap Membrane Distillation Crystallization via SiO₂ Seeding

by Stefanie Flatscher, Mark W. Hlawitschka, Wolfgang M. Samhaber, Florian Hell and Josef Lahnsteiner

Membranes 2025, 15(10), 321; https://doi.org/10.3390/membranes15100321 - 17 Oct 2025

Membrane distillation crystallization (MDCr) is an approach for treating hypersaline wastewaters and enabling zero-liquid-discharge (ZLD) systems. However, its performance is often inhibited by concentration polarization, scaling, and membrane wetting. Heterogeneous seeding has been proposed to shift crystallization into the bulk phase, yet its [...] Read more.

Membrane distillation crystallization (MDCr) is an approach for treating hypersaline wastewaters and enabling zero-liquid-discharge (ZLD) systems. However, its performance is often inhibited by concentration polarization, scaling, and membrane wetting. Heterogeneous seeding has been proposed to shift crystallization into the bulk phase, yet its quantitative influence on flux stability, wetting resistance, and crystal growth remains poorly understood. This study investigates air-gap MDCr (AGMDCr) of 300 g L⁻¹ NaCl using polypropylene (PP) and polytetrafluoroethylene (PTFE) membranes under seeded and unseeded conditions. Introducing 0.1 g L⁻¹ SiO₂ seeds (30–60 µm) enhanced steady-state permeate flux by 41% and maintained salt rejection ≥ 99.99%, indicating effective suppression of wetting. Seeding shifted the crystal size distribution from fine (mean 50.6 µm, unseeded) to coarse (230–340 µm), consistent with reduced primary nucleation and preferential growth on seed surfaces. At 0.6 g L⁻¹, the flux decreased relative to 0.1–0.3 g L⁻¹, consistent with near-wall solids holdup and hindered transport at high seeding concentration. The PTFE membrane exhibited a 47% higher flux than PP, primarily due to its reduced thermal resistance and optimized module geometry at the same flow rate. These results demonstrate that appropriately sized and dosed SiO₂ seeding effectively stabilizes flux and suppresses wetting in MDCr. Full article

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

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17 pages, 2301 KB

Open AccessArticle

Capacitive Coulometric Readout of Polyaniline Membrane-Based pH Sensors in Combination with Cyclic Voltammetry and Electrochemical Impedance Spectroscopy

by Tingting Han, Tao Song, Dongxue Han and Li Niu

Membranes 2025, 15(10), 320; https://doi.org/10.3390/membranes15100320 - 17 Oct 2025

In this study, a polyaniline (PANI)-based solid-contact pH sensor was fabricated, and its amperometric and coulometric response was investigated both without and in series with capacitors (10 and 47 µF). The conducting polymer PANI membrane was electropolymerized on the electrode surface to serve [...] Read more.

In this study, a polyaniline (PANI)-based solid-contact pH sensor was fabricated, and its amperometric and coulometric response was investigated both without and in series with capacitors (10 and 47 µF). The conducting polymer PANI membrane was electropolymerized on the electrode surface to serve as an ion-to-electron transducer. The amperometric and coulometric performance of the PANI-based sensor in series with a capacitor (10 µF) was reduced to the order of seconds, and the cumulated charge Q was standardized, significantly minimizing the influence of applied potential. Electrochemical impedance spectroscopy, constant potential coulometry, and cyclic voltammetry demonstrated that a larger low-frequency capacitance corresponds to a greater cumulated charge, reflecting the doping level of the electropolymerized PANI membrane. The growth of the PANI membrane, represented by charge Q, increased exponentially with the number of polymerization cycles, following a power-law relationship with exponents (α) of 2.14 (1–25 cycles) and 2.97 (30–100 cycles), consistent with a transition from a layered (10 cycles) to a porous morphology (50 cycles). Furthermore, a linear dependence of cumulated charge Q on pH was observed, demonstrating that capacitive coulometric readout offers a promising and practical approach for wearable ion sensors. Full article

(This article belongs to the Special Issue Ion-Selective Electrodes and Membrane-Based Ion Sensing Devices: Materials, Mechanisms, and Applications)

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12 pages, 368 KB

Open AccessArticle

Formation of Multispheres and Myelin Based on Multiple Solutions of Membrane Shape Equation

by Tao Xu and Zhong-Can Ou-Yang

Membranes 2025, 15(10), 319; https://doi.org/10.3390/membranes15100319 - 16 Oct 2025

In this work, we construct a multiple solutions theory based on a membrane shape equation. The membrane shape of a vesicle or a red blood cell is determined using the Zhongcan–Helfrich shape equation. These spherical solutions, which have an identical radius

r_{s}

[...] Read more.

In this work, we construct a multiple solutions theory based on a membrane shape equation. The membrane shape of a vesicle or a red blood cell is determined using the Zhongcan–Helfrich shape equation. These spherical solutions, which have an identical radius

r_{s}

but different center positions, can be described by the same equation:

ϕ - ρ / r_{s} = 0

. A degeneracy for the spherical solutions exists, leading to multisphere solutions with the same radius. Therefore, there can be multiple solutions for the sphere equilibrium shape equation, and these need to satisfy a quadratic equation. The quadratic equation has a maximum of two roots. We also find that the multiple solutions should be in a line to undergo rotational symmetry. We use the quadratic equation to compute the sphere radius, together with a membrane surface constraint condition, to obtain the number of small spheres. We ensure matching with the energy constraint condition to determine the stability of the full solutions. The method is then extended into the myelin formation of red blood cells. Our numerical calculations show excellent agreement with the experimental results and enable the comprehensive investigation of cell fission and fusion phenomena. Additionally, we have predicted the existence of the bifurcation phenomenon in membrane growth and proposed a control strategy. Full article

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

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32 pages, 4620 KB

Open AccessArticle

Unveiling the Potential of Solar-Powered Multistage Hollow Fiber WGMD: A Transient Performance Evaluation

by Mohamed O. Elbessomy, Kareem W. Farghaly, Osama A. Elsamni, Samy M. Elsherbiny, Ahmed Rezk and Mahmoud B. Elsheniti

Membranes 2025, 15(10), 318; https://doi.org/10.3390/membranes15100318 - 16 Oct 2025

Solar-energy-driven membrane distillation provides a sustainable pathway to mitigate freshwater scarcity by utilizing an abundant renewable heat source. This study develops a two-dimensional axisymmetric computational fluid dynamics (CFD) model to simulate the transient performance of a hollow fiber water gap membrane distillation (HF-WGMD) [...] Read more.

Solar-energy-driven membrane distillation provides a sustainable pathway to mitigate freshwater scarcity by utilizing an abundant renewable heat source. This study develops a two-dimensional axisymmetric computational fluid dynamics (CFD) model to simulate the transient performance of a hollow fiber water gap membrane distillation (HF-WGMD) module integrated with flat-plate solar collectors (FPCs). A lumped-parameter transient FPC model is coupled with the CFD framework to predict feed water temperature under time-varying solar irradiation, evaluated across four representative days in a Mediterranean city. The model is validated against experimental data, showing strong agreement. A comprehensive parametric analysis reveals that increasing the collector area from 10 to 50 m² enhances the average water flux by a factor of 6.4, reaching 10.9 kg/(m²h), while other parameters such as collector width, tube number and working fluid flow rate exert comparatively minor effects. The module flux strongly correlates with solar intensity, achieving a maximum instantaneous value of 18.4 kg/(m²h) with 35 m² collectors. Multistage HF-WGMD configurations are further investigated, demonstrating substantial reductions in solar energy demand due to internal thermal recovery by the cooling stream. A 40-stage system operating with only 10 m² of solar collectors achieves an average specific thermal energy consumption of 424 kWh/m³, while the overall solar desalination efficiency improves dramatically from 2.6% for a single-stage system with 50 m² collectors to 57.5% for the multistage configuration. The proposed system achieves a maximum freshwater productivity of 51.5 kg/day, highlighting the viability and optimization potential of solar-driven HF-WGMD desalination. Full article

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22 pages, 1293 KB

Open AccessReview

Single-Molecule Imaging and Super-Resolution Microscopy of Lipid Domains in Cell Membranes Using Lipid-Binding Proteins and Fluorophore-Conjugated Lipid Analogs

by Toshiki Mori and Kenichi G. N. Suzuki

Membranes 2025, 15(10), 317; https://doi.org/10.3390/membranes15100317 - 16 Oct 2025

Lipids are spatiotemporally organized in cell membranes, where they play indispensable roles in regulating diverse biological processes. Their distribution and dynamics are intricately coupled to signal transduction, membrane trafficking, and host–pathogen interactions. The past decade has seen substantial progress in the development of [...] Read more.

Lipids are spatiotemporally organized in cell membranes, where they play indispensable roles in regulating diverse biological processes. Their distribution and dynamics are intricately coupled to signal transduction, membrane trafficking, and host–pathogen interactions. The past decade has seen substantial progress in the development of lipid probes and imaging techniques, which have greatly advanced our understanding of lipid-mediated regulation in living cells. Chemically optimized lipid analogs conjugated with hydrophilic fluorophores have enabled the faithful visualization of raftophilic lipids, such as sphingomyelin, gangliosides, and cholesterol, while minimizing artifacts. In parallel, genetically encoded lipid sensors derived from lipid-binding protein domains have been established. These sensors selectively report the localization and dynamics of diverse lipid species, including phosphoinositides, cholesterol, sphingomyelin, and phosphatidylserine, in their native contexts. Combined with state-of-the-art advanced microscopy approaches, including ultrafast single-molecule imaging and super-resolution microscopy, these probes facilitate high-resolution and quantitative analyses of lipid organization. This review summarizes recent advances in both synthetic lipid probes and genetically encoded lipid sensors, emphasizing their applications in mechanistic studies of membrane biology. We further discuss current challenges and future directions toward the comprehensive and minimally perturbative visualization of lipids. Full article

(This article belongs to the Section Biological Membranes)

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12 pages, 2292 KB

Open AccessArticle

PDMS Mixed Matrix Membrane with Confined Mass Transfer Structure: The Effect of COFs with Different Porous Structures and Chemical Properties in the Pervaperation Process

by Yuan Zhai, Zimeng Zheng, Xinhao Cui, Kun Jiang, Ao Sheng and Heyun Wang

Membranes 2025, 15(10), 316; https://doi.org/10.3390/membranes15100316 - 15 Oct 2025

In this study, hydrophilic covalent organic framework (COF) nanosheets with triazine structures and hydrophobic COF nanosheets with fluorinated imine skeletons were designed to enhance the membrane separation process for ethanol pervaporation. The mass transfer of ethanol–water mixtures within the confined structures of COF [...] Read more.

In this study, hydrophilic covalent organic framework (COF) nanosheets with triazine structures and hydrophobic COF nanosheets with fluorinated imine skeletons were designed to enhance the membrane separation process for ethanol pervaporation. The mass transfer of ethanol–water mixtures within the confined structures of COF nanosheets was investigated through experimental characterization and computational simulations, establishing a quantitative relationship between mass transfer performance and the pore size/chemical properties of COF nanosheets. These COF nanosheets were employed to optimize the confined architecture of mixed matrix membranes (MMMs), effectively regulating the critical parameters of MMMs and improving their separation performance. Through systematic investigation of formation mechanisms and modulation principles, we revealed the correlation between confined structural parameters and membrane separation efficiency. This work develops methodologies and foundational theories to overcome the permeability-selectivity trade-off effect, providing theoretical guidance for designing novel membrane materials with ethanol-permelective COF-based MMMs. Full article

(This article belongs to the Section Membrane Fabrication and Characterization)

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