Membranes

18 pages, 2170 KiB

Open AccessReview

Machine Learning in the Design and Performance Prediction of Organic Framework Membranes: Methodologies, Applications, and Industrial Prospects

by Tong Wu, Jiawei Zhang, Qinghao Yan, Jingxiang Wang and Hao Yang

Membranes 2025, 15(6), 178; https://doi.org/10.3390/membranes15060178 - 11 Jun 2025

Abstract

Organic framework membranes (OFMs) have emerged as transformative materials for separation technologies due to their tunable porosity, structural diversity, and stability, yet their design and optimization face challenges in navigating vast chemical spaces and complex performance trade-offs. This review highlights the pivotal role [...] Read more.

Organic framework membranes (OFMs) have emerged as transformative materials for separation technologies due to their tunable porosity, structural diversity, and stability, yet their design and optimization face challenges in navigating vast chemical spaces and complex performance trade-offs. This review highlights the pivotal role of machine learning (ML) in overcoming these limitations by integrating multi-source data, constructing quantitative structure–property relationships, and enabling the cross-scale optimization of OFMs. Methodologically, ML workflows—spanning data construction, feature engineering, and model optimization—accelerate candidate screening, inverse design, and mechanistic interpretation, as demonstrated in gas separations and nascent liquid-phase applications. Key findings reveal that ML identifies critical structural descriptors and environmental parameters, guiding the development of high-performance membranes that surpass traditional selectivity–permeability limits. Challenges persist in liquid separations due to dynamic operational complexities and data scarcity, while emerging frameworks offer untapped potential. The integration of interpretable ML, in situ characterization, and industrial scalability strategies is essential to transition OFMs from laboratory innovations to sustainable, adaptive separation systems. This review underscores ML’s transformative capacity to bridge computational insights with experimental validation, fostering next-generation membranes for carbon neutrality, water security, and energy-efficient industrial processes. Full article

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

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16 pages, 3318 KiB

Open AccessArticle

Nanofibrous Membranes Based on Collagen and Conductive Polymers with Perspective for Biological Applications

by Tonantzi Pérez-Moreno, Claudia D’Urso, Gabriel Trejo, Maria V. Contreras-Martínez, Omar Lozano, Gerardo J. García-Rivas, Luis G. Arriaga, Gabriel Luna-Barcenas and Janet Ledesma-García

Membranes 2025, 15(6), 177; https://doi.org/10.3390/membranes15060177 - 11 Jun 2025

Abstract

In this study, membranes of collagen–chitosan (C-Ch) in combination with conductive polymers (CPs) such as polyaniline (Pani) and polypyrrole (Ppy) were obtained by electrospinning using non-toxic solvents such as PBS and ethanol. The change in the morphology after swelling was observed by SEM, [...] Read more.

In this study, membranes of collagen–chitosan (C-Ch) in combination with conductive polymers (CPs) such as polyaniline (Pani) and polypyrrole (Ppy) were obtained by electrospinning using non-toxic solvents such as PBS and ethanol. The change in the morphology after swelling was observed by SEM, while an FTIR analysis showed specific interactions between C-Ch and CP. Mechanical tests showed that C-Ch/Ppy exhibited more elastic behavior and a better stress distribution compared to C-Ch/Pani. The diffusion of Na⁺ and Ca²⁺ ions through the membranes was evaluated and showed a greater resistance for Ca²⁺ in both membrane types. Preliminary biocompatibility testing with H9C2 cells showed a successful cell adhesion to the membranes. These results emphasize the potential of C-Ch/Pani composites for electrically active scaffolds and of C-Ch/PPy composites for applications in mechanically dynamic tissue-specific regeneration. Full article

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

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23 pages, 1533 KiB

Open AccessArticle

Oil and Water Recovery from Palm Oil Mill Effluent: A Comparative Study of PVDF and α-Al₂O₃ Ultrafiltration Membranes

by Saqr A. A. Al-Muraisy, Jiamin Wu, Mingliang Chen, Begüm Tanis, Sebastiaan G. J. Heijman, Shahrul bin Ismail, Jules B. van Lier and Ralph E. F. Lindeboom

Membranes 2025, 15(6), 176; https://doi.org/10.3390/membranes15060176 - 10 Jun 2025

Abstract

Recovering oil and water from palm oil mill effluent reduces environmental pollution and promotes sustainable practices. An effective method to achieve this is ultrafiltration (UF), which uses semi-permeable membranes to separate oil, solids, and other contaminants from wastewater under pressure. To assess the [...] Read more.

Recovering oil and water from palm oil mill effluent reduces environmental pollution and promotes sustainable practices. An effective method to achieve this is ultrafiltration (UF), which uses semi-permeable membranes to separate oil, solids, and other contaminants from wastewater under pressure. To assess the most effective recovery method, an experimental comparison was conducted between PVDF and α-Al₂O₃ UF membranes at constant permeate of 20–50 LMH for PVDF and 20–70 LMH for α-Al₂O₃ membranes. Both membranes achieved 99.8% chemical oxygen demand (COD) rejection, with oil concentration factor (F_o) of 186.8% and 253.0%, and water recovery (R_w) of 46.6% and 60.5%, respectively. The permeate water quality was superior to the Malaysian discharge standards, and the fat, oil, and grease (FOG) content was suitable for phase separation processes. The optimal permeate fluxes, with stable transmembrane pressures (TMP), were observed at 40 LMH (PVDF) and 60 LMH (α-Al₂O₃). Total resistance (R_t) values were 1.30 × 10¹² m⁻¹ (PVDF) and 1.59 × 10¹² m⁻¹ (α-Al₂O₃). The ratio of irreversible to total resistances (R_ir/R_t) was 0.02 (PVDF) and 0.06 (α-Al₂O₃), indicating minimal irreversible fouling. Overall, the α-Al₂O₃ membrane demonstrated superior performance in oil and water recovery with more stable operation compared to the PVDF membrane. UF membrane technology emerges as an efficient technique for recovering oil and water compared to conventional methods. 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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13 pages, 4682 KiB

Open AccessCommunication

Seven-Channel Polyethersulfone Hollow-Fiber Membrane Preparation with Vapor-Induced Phase Separation

by Xiaoyao Wang, Zhiyuan Hao, Rui Huang, Yajing Huang, Huiqun Zhang and Xiujuan Hao

Membranes 2025, 15(6), 175; https://doi.org/10.3390/membranes15060175 - 10 Jun 2025

Abstract

Polyethersulfone (PES) has been widely used to fabricate hollow-fiber ultrafiltration membranes due to its good oxidative, thermal, and hydrolytic stability. Typical PES hollow-fiber membranes with a single bore have limited strength and may break under uneven pressure and vibration during membrane backwashing. Multi-channel [...] Read more.

Polyethersulfone (PES) has been widely used to fabricate hollow-fiber ultrafiltration membranes due to its good oxidative, thermal, and hydrolytic stability. Typical PES hollow-fiber membranes with a single bore have limited strength and may break under uneven pressure and vibration during membrane backwashing. Multi-channel hollow-fiber membranes have stronger breaking force due to their larger cross-sectional area, but fabricating them remains challenging due to the difficulty in controlling the phase inversion process. This study uses the vapor-induced phase separation (VIPS) method to fabricate a seven-channel PES hollow-fiber membrane, and the air gap and air relative humidity can help in membrane morphology control. Moreover, carboxylic graphene quantum dots (CGQDs) are first used in ultrafiltration membranes to increase membrane porosity and hydrophilicity. We found that the membrane prepared with a 7.5% CGQD mass fraction, a 10 cm air gap, and 99% relative humidity had the highest flux and porosity; the membrane pore size distribution was concentrated at 72 nm, and the pure water flux could reach 464 L·m⁻² h⁻¹·bar⁻¹. In the long-term filtration performance test, the membrane can reject more than about 15% TOC and 84% turbidity at 50 L·m⁻² h⁻¹ flux, confirming its stability for water purification applications. Full article

(This article belongs to the Special Issue Membrane Technologies for Water Purification)

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12 pages, 7533 KiB

Open AccessArticle

Determining Accurate Pore Structures of Polypropylene Membrane for ECMO Using FE-SEM Under Optimized Conditions

by Makoto Fukuda, Yoshiaki Nishite, Eri Murata, Koki Namekawa, Tomohiro Mori, Tsutomu Tanaka and Kiyotaka Sakai

Membranes 2025, 15(6), 174; https://doi.org/10.3390/membranes15060174 - 9 Jun 2025

Abstract

Long-term ECMOs are expected to be put into practical use in order to prepare for the next emerging severe infectious diseases after the novel coronavirus pandemic in 2019–2023. While polypropylene (PP) and polymethylpentene (PMP) are currently the mainstream materials for the hollow fiber [...] Read more.

Long-term ECMOs are expected to be put into practical use in order to prepare for the next emerging severe infectious diseases after the novel coronavirus pandemic in 2019–2023. While polypropylene (PP) and polymethylpentene (PMP) are currently the mainstream materials for the hollow fiber membranes of ECMO, the PP membrane coated with a silicone layer on the outer surface has also been commercialized. In this study, we sought a method to accurately observe the detailed pore morphologies of the PP membrane by suppressing irreversible changes in the morphology in SEM observation, which is a general-purpose observation with higher resolution. As a result, the convex surface morphologies of the PP membrane, which was a non-conductive porous structure, were confirmed in detail by utilizing the lower secondary electron image (LEI) mode (FE-SEM, JSM-7610F, JEOL Ltd., Tokyo, Japan) at low acceleration voltage, low magnification, and long working distance, to minimize morphological alterations caused by osmium (Os) sputtering. On the other hand, although the sputter-coating on non-conductive samples is mandatory for imaging morphologies with SEM, the non-sputtering method is also worthwhile for porous and fragile structures such as this sample to minimize morphological alterations. Furthermore, we propose a method to confirm the morphology of the deep part of the sample by utilizing the secondary electron image (SEI) mode at an appropriate acceleration voltage and high magnification with higher resolution. Full article

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

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26 pages, 9435 KiB

Open AccessReview

Comprehensive Insights into the Cholesterol-Mediated Modulation of Membrane Function Through Molecular Dynamics Simulations

by Ehsaneh Khodadadi, Ehsan Khodadadi, Parth Chaturvedi and Mahmoud Moradi

Membranes 2025, 15(6), 173; https://doi.org/10.3390/membranes15060173 - 8 Jun 2025

Abstract

Cholesterol plays an essential role in biological membranes and is crucial for maintaining their stability and functionality. In addition to biological membranes, cholesterol is also used in various synthetic lipid-based structures such as liposomes, proteoliposomes, and nanodiscs. Cholesterol regulates membrane properties by influencing [...] Read more.

Cholesterol plays an essential role in biological membranes and is crucial for maintaining their stability and functionality. In addition to biological membranes, cholesterol is also used in various synthetic lipid-based structures such as liposomes, proteoliposomes, and nanodiscs. Cholesterol regulates membrane properties by influencing the density of lipids, phase separation into liquid-ordered (Lo) and liquid-disordered (Ld) areas, and stability of protein–membrane interactions. For planar bilayers, cholesterol thickens the membrane, decreases permeability, and brings lipids into well-ordered domains, thereby increasing membrane rigidity by condensing lipid packing, while maintaining lateral lipid mobility in disordered regions to preserve overall membrane fluidity. It modulates membrane curvature in curved bilayers and vesicles, and stabilizes low-curvature regions, which are important for structural integrity. In liposomes, cholesterol facilitates drug encapsulation and release by controlling bilayer flexibility and stability. In nanodiscs, cholesterol enhances structural integrity and protein compatibility, which enables the investigation of protein–lipid interactions under physiological conditions. In proteoliposomes, cholesterol regulates the conformational stability of embedded proteins that have implications for protein–lipid interaction. Developments in molecular dynamics (MD) techniques, from coarse-grained to all-atom simulations, have shown how cholesterol modulates lipid tail ordering, membrane curvature, and flip-flop behavior in response to concentration. Such simulations provide insights into the mechanisms underlying membrane-associated diseases, aiding in the design of efficient drug delivery systems. In this review, we combine results from MD simulations to provide a synoptic explanation of cholesterol’s complex function in regulating membrane behavior. This synthesis combines fundamental biophysical information with practical membrane engineering, underscoring cholesterol’s important role in membrane structure, dynamics, and performance, and paving the way for rational design of stable and functional lipid-based systems to be used in medicine. In this review, we gather evidence from MD simulations to provide an overview of cholesterol’s complex function regulating membrane behavior. This synthesis connects the fundamental biophysical science with practical membrane engineering, which highlights cholesterol’s important role in membrane structure, dynamics, and function and helps us rationally design stable and functional lipid-based systems for therapeutic purposes. Full article

(This article belongs to the Section Biological Membranes)

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19 pages, 13134 KiB

Open AccessArticle

Improving PFAS Rejection by Ultrafiltration Membranes via Polyelectrolyte Multilayer Coating

by Oruc Kaan Turk, Mehmet Cakmakci, Ismail Hakki Zengin, Dogan Karadag and Ebubekir Yuksel

Membranes 2025, 15(6), 172; https://doi.org/10.3390/membranes15060172 - 7 Jun 2025

Abstract

Per- and polyfluoroalkyl substances (PFASs), used since the 1940s, are persistent and carcinogenic pollutants. Water is a major exposure route; effective removal is essential. While nanofiltration (NF) and reverse osmosis (RO) are effective but costly, ultrafiltration (UF) membranes offer advantages such as lower [...] Read more.

Per- and polyfluoroalkyl substances (PFASs), used since the 1940s, are persistent and carcinogenic pollutants. Water is a major exposure route; effective removal is essential. While nanofiltration (NF) and reverse osmosis (RO) are effective but costly, ultrafiltration (UF) membranes offer advantages such as lower cost and higher flux, but their relatively large pore size makes them ineffective for PFAS compounds like perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Since PFAS removal depends on both pore size and surface properties, this study investigates the effect of polyelectrolyte multilayer coatings using poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) on the zeta potential of UF membranes. Pristine UF membranes showed limited performance (UP150: ~2% for both PFOS and PFOA; UP020: 34.4% PFOS, 24.1% PFOA), while coating significantly enhanced removal (coated UP150: 45.3% PFOS, 43.4% PFOA; coated UP020: 77.8% PFOS, 73.3% PFOA). The modified UF membranes achieved PFAS removal efficiencies significantly closer to NF membranes, though still below those of RO (e.g., BW30XLE: up to 91.0% PFOS, 88.3% PFOA; NP030: up to 81.0% PFOS, 79.3% PFOA). Findings emphasize the importance of membrane surface charge and suggest that modified UF membranes offer a promising, low-cost alternative for PFAS removal under low-pressure conditions. Full article

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

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Graphical abstract

14 pages, 2703 KiB

Open AccessArticle

Energy Efficient Forward Osmosis to Maximize Dewatering Rates

by Jongmin Jeon, Dongkeon Kim and Suhan Kim

Membranes 2025, 15(6), 171; https://doi.org/10.3390/membranes15060171 - 7 Jun 2025

Abstract

Forward osmosis (FO) is a membrane separation process driven by the osmotic pressure difference between a high-salinity draw solution (DS) and a low-salinity feed solution (FS). This pressure-free dewatering method is highly energy efficient, making it suitable for concentration and resource recovery. However, [...] Read more.

Forward osmosis (FO) is a membrane separation process driven by the osmotic pressure difference between a high-salinity draw solution (DS) and a low-salinity feed solution (FS). This pressure-free dewatering method is highly energy efficient, making it suitable for concentration and resource recovery. However, conventional FO systems using series-connected modules suffer from progressive DS dilution and FS concentration, leading to a reduction in the osmotic driving force and thereby limiting the overall performance. To address this issue, we propose a novel hybrid FO module configuration in which the FS flows in series while the DS is split and distributed in parallel across moules. This configuration was evaluated using an experimentally validated FO module model and RO simulation tools. Under seawater (600 mM NaCl) as DS and brackish water (10 mM NaCl) as FS, a conventional three-stage FO module achieved an enrichment ratio of 2.5 with an energy consumption of 0.151 kWh/m³. In contrast, the proposed draw solution split distribution (DSSD) achieved an enrichment ratio of 12.5 at a reduced energy consumption of 0.137 kWh/m³. In comparison, a reverse osmosis system consuming 0.58 kWh/m³ achieved a similar enrichment ratio of 12.3. These results demonstrate the high energy efficiency and dewatering capacity of the proposed FO configuration, highlighting its potential for industrial applications in food processing, beverage production, pharmaceuticals and agriculture. 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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20 pages, 2022 KiB

Open AccessArticle

Prediction of Expected Fouling Time During Transmembrane Transition in Reverse Osmosis Systems

by Jozsef Lakner and Gabor Lakner

Membranes 2025, 15(6), 170; https://doi.org/10.3390/membranes15060170 - 6 Jun 2025

Abstract

Membrane filtration, including reverse osmosis filtration, is widely applied in water treatment worldwide, offering solutions to a broad range of separation challenges. However, due to the porous structure of membranes, they are prone to fouling, which reduces their efficiency and can eventually render [...] Read more.

Membrane filtration, including reverse osmosis filtration, is widely applied in water treatment worldwide, offering solutions to a broad range of separation challenges. However, due to the porous structure of membranes, they are prone to fouling, which reduces their efficiency and can eventually render the membranes incapable of functioning. In such cases, a systemic intervention becomes necessary, highlighting the importance of accurately predicting the expected fouling time. Various approaches for estimating fouling processes and times are well documented in the literature. However, a common limitation of these methods is that they typically assume constant and well-defined operating parameters over time. Under such stable conditions, the process can be described deterministically, and the fouling time can be predicted using straightforward extrapolation techniques. However, in industrial practice, process conditions often fluctuate due to multiple influencing factors, making fouling time a variable quantity. Therefore, it can be more appropriately treated as a random variable characterized by a mean value and standard deviation. Rather than predicting a precise fouling time, it is more relevant to define a probabilistic interval within which the fouling is expected to occur with a specified confidence level (e.g., 95%). The associated maintenance scheduling can then be optimized based on economic criteria. The probability-based model presented herein defines this interval based on operational measurements, thereby providing users with a time window during which maintenance should be planned. From this point forward, the exact timing of interventions becomes a matter of technical feasibility and economic optimization. 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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17 pages, 3754 KiB

Open AccessArticle

Calcium Ion Mixing Modes Govern Membrane Fouling Mitigation During Membrane-Based Recovery of Extracellular Polymeric Substances

by Da-Qi Cao, Yi-Xuan Song, Yun-Feng Wu, Guri Yihuo and Jing-Yi Jin

Membranes 2025, 15(6), 169; https://doi.org/10.3390/membranes15060169 - 5 Jun 2025

Abstract

Recycling extracellular polymeric substances (EPSs) from excess sludge in wastewater treatment plants has garnered significant research attention. Membrane separation offers a promising approach for EPS concentration; however, membrane fouling remains a critical challenge. Previous studies demonstrate that Ca²⁺ addition effectively mitigates membrane [...] Read more.

Recycling extracellular polymeric substances (EPSs) from excess sludge in wastewater treatment plants has garnered significant research attention. Membrane separation offers a promising approach for EPS concentration; however, membrane fouling remains a critical challenge. Previous studies demonstrate that Ca²⁺ addition effectively mitigates membrane fouling. This study reveals that Ca²⁺ mixing modes govern membrane fouling in the dead-end ultrafiltration of both the practical EPS and model EPS [sodium algiante (SA)]. The interaction mechanisms between Ca²⁺ and the EPS under varied mixing conditions and their impact on filtration performance were systematically investigated. At a low Ca²⁺ concentration, the addition sequence critically influenced colloidal particle sizes formed via Ca²⁺-EPS interactions, altering the cake layer structure governing filtration resistance; these effects diminished at higher Ca²⁺ concentrations. In suspensions prepared by adding EPS to Ca²⁺ solution (EPS-Ca), a portion of the EPS became encapsulated within an EPS-Ca layer formed through Ca²⁺ EPS binding, reducing free EPS concentration and enlarging colloidal aggregates. This encapsulation reduced EPS-mediated membrane fouling, thereby lowering filtration resistance. Conversely, in suspensions prepared by adding Ca²⁺ to EPS solution (Ca-EPS), more complete Ca²⁺ EPS interactions formed a dense crosslinked structure with smaller colloids on membrane surfaces, intensifying fouling and resistance. Additionally, EPS-Ca exhibited higher compressibility than Ca-EPS, though both exhibited comparable filtration resistance under high-pressure conditions. These results offer critical insights into optimizing EPS ultrafiltration concentration to mitigate membrane fouling through Ca²⁺ addition strategies. Full article

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

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13 pages, 1147 KiB

Open AccessArticle

Exploring Nanofiltration for Transport of Small Molecular Species for Application in Artificial Kidney Devices to Treat End-Stage Kidney Disease

by Haley Duncan, Christopher Newton, Jamie Hestekin, Christa Hestekin and Ira Kurtz

Membranes 2025, 15(6), 168; https://doi.org/10.3390/membranes15060168 - 2 Jun 2025

Abstract

End-stage renal disease occurs when there is permanent loss of the kidney’s ability to filter toxins from the blood. Due to the limited number of transplants, dialysis is currently the most common treatment, but it significantly limits a patient’s lifestyle and has significant [...] Read more.

End-stage renal disease occurs when there is permanent loss of the kidney’s ability to filter toxins from the blood. Due to the limited number of transplants, dialysis is currently the most common treatment, but it significantly limits a patient’s lifestyle and has significant side effects. One solution is an artificial kidney, but significant challenges remain in its development. One challenge is the separation of glucose from urea. Nanofiltration is ideal for this separation; however, there is little understanding of the important parameters for this separation under physiological conditions. In this study, operating parameters (pressure and temperature) as well as feed conditions (increased glucose/salt) were explored for their effects on the separation of glucose from urea in six commercial membranes. The rejection of monovalent and divalent ions was also characterized. While increasing pressure increased flux, it had little effect on metabolite rejection, except for glucose, which increased above 20 psi. Increasing temperature led to a slight increase in flux and a slight decrease in the rejection of divalent ions. Glucose rejection was sensitive to feed conditions, while urea rejection was less affected. Divalent ions were rejected more strongly than monovalent ions and were also more affected by feed conditions. Full article

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

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26 pages, 1134 KiB

Open AccessReview

Nanomembranes as Eco-Friendly Instruments for Modern Food Processing, from Filtration to Packaging

by Simona Gavrilaș

Membranes 2025, 15(6), 167; https://doi.org/10.3390/membranes15060167 - 2 Jun 2025

Abstract

With the increasing demand for safe, high-quality, and sustainable food, nanomembranes have attracted significant interest as innovative solutions in food processing. They are extremely thin structures created from special materials that allow for the selective filtration of very small particles. In the food [...] Read more.

With the increasing demand for safe, high-quality, and sustainable food, nanomembranes have attracted significant interest as innovative solutions in food processing. They are extremely thin structures created from special materials that allow for the selective filtration of very small particles. In the food industry, such approaches are increasingly used for packaging and processing, as they can slow down food degradation and thus extend its shelf life. This article examines the potential of utilizing nanomembranes as ecological tools at various stages of the food chain, ranging from advanced filtration of food liquids to the development of smart and active packaging. This study reviews the recent research in the field, highlighting the applications developed and presenting targeted advantages and disadvantages. The developed applications primarily focus on extending the shelf life of products while also discussing their antioxidant and antibacterial attributes. By highlighting the latest applications and emerging research directions, this article underscores the pivotal role of nanomembranes in facilitating the transition to a modern, sustainable, and environmentally responsible food industry. However, current research faces several challenges. Most products are less biodegradable and, consequently, could harm the environment. Additionally, data on the long-term effects of these materials on human health, particularly when used in packaging that comes into direct contact with food, remain insufficient. Therefore, more sustainable solutions are needed, such as nanomembranes based on natural biopolymers. Further studies are required to assess their safety and real-world effectiveness under industrial conditions. Full article

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

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9 pages, 1752 KiB

Open AccessCommunication

A Fiberglass-Cloth-Reinforced Perfluorosulfonic Acid Membrane

by Zhutao Zhang, Yiru Dou, Wen Zhang, Li Xu and Yuxin Wang

Membranes 2025, 15(6), 166; https://doi.org/10.3390/membranes15060166 - 2 Jun 2025

Abstract

Perfluorosulfonic acid (PFSA) membranes have found broad-ranging applications, owing to their high ionic conductivity and excellent chemical stability. However, membranes with higher mechanical strength, lower area-specific resistance, reduced swelling, less gas crossover and more affordable costs are desirable. Herein, we report on the [...] Read more.

Perfluorosulfonic acid (PFSA) membranes have found broad-ranging applications, owing to their high ionic conductivity and excellent chemical stability. However, membranes with higher mechanical strength, lower area-specific resistance, reduced swelling, less gas crossover and more affordable costs are desirable. Herein, we report on the fabrication of a fiberglass-cloth-reinforced PFSA membrane using a simple solution cast method. The breaking strength of the reinforced membrane has the potential to reach 81 MPa, which is about 6 times and 2.5 times that of its non-reinforced counterpart and the commercial Nafion 117 (N117) membrane, respectively. The area swelling ratio of the reinforced membrane is lowered to merely 3%, which is only about 1/12 that of N117, in water at 100 °C. Despite ionic conduction being hindered by the fiberglass cloth, the reinforced PFSA membrane shows an area-specific resistance of only 0.069 Ω·cm², which is 58% lower than that of N117, under 80 °C and 100% humidity. This research provides a promising technological pathway for the development of high-performance ionic conductive membranes. Full article

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

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15 pages, 2234 KiB

Open AccessArticle

Moving Rubber Blade (MRB) for Fouling Control in Anaerobic Ceramic Membrane Bioreactors (AnCMBRs) Treating High-Strength Food Wastewater: Development and Long-Term Application

by Young-Jae Lee, Hyung-Soo Kim, Hyunsup Jang, Sung-Gwan Park, Ji-Yeon Kim, Sung-Jae Lee, Youngjin Kim, Moon-Hyun Hwang and Sangyoup Lee

Membranes 2025, 15(6), 165; https://doi.org/10.3390/membranes15060165 - 1 Jun 2025

Abstract

This study investigates membrane fouling control in a submerged anaerobic ceramic membrane bioreactor (AnCMBR) treating high-strength food wastewater (chemical oxygen demand (COD): 10–30 g/L). A hybrid strategy combining mechanical cleaning via a moving rubber blade (MRB) (termed anaerobic ceramic blade MBR (AnCBMBR)) with [...] Read more.

This study investigates membrane fouling control in a submerged anaerobic ceramic membrane bioreactor (AnCMBR) treating high-strength food wastewater (chemical oxygen demand (COD): 10–30 g/L). A hybrid strategy combining mechanical cleaning via a moving rubber blade (MRB) (termed anaerobic ceramic blade MBR (AnCBMBR)) with intermittent salt-assisted backwash (SAB) was tested to manage transmembrane pressure (TMP) and sustain treatment performance. During more than 300 days of field operation, MRB alone maintained stable TMP below 0.15 kg_f/cm² without backwashing, achieving more than 90% COD removal at a very short hydraulic retention time (HRT) of 1–2 days. Introducing intermittent SAB further stabilized operations and enhanced total phosphorus (T-P) removal by facilitating struvite formation through the interaction of MgCl₂ and phosphorus in the reactor. The AnCBMBR system demonstrated reliable, long-term fouling control and treatment efficiency, even under high organic loads, proving its viability for small-scale facilities managing concentrated food wastewater. This study advances practical strategies for sustainable anaerobic MBR operation under challenging industrial conditions. Full article

(This article belongs to the Special Issue Advanced Membranes and Membrane Technologies for Wastewater Treatment)

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15 pages, 2665 KiB

Open AccessArticle

Development of Thermo-Responsive and Salt-Adaptive Ultrafiltration Membranes Functionalized with PNIPAM-co-PDMAC Copolymer

by Lauran Mama, Johanne Pirkin-Benameur, Vincent Bouad, David Fournier, Patrice Woisel, Joël Lyskawa, Karim Aissou and Damien Quemener

Membranes 2025, 15(6), 164; https://doi.org/10.3390/membranes15060164 - 28 May 2025

Abstract

Access to clean water remains a critical global challenge, exacerbated by population growth, industrial activity, and climate change. In response, this study presents the development and characterization of thermo-responsive and salt-adaptive ultrafiltration membranes functionalized with a poly(N-isopropylacrylamide)–co-poly(dimethylacrylamide) (PNIPAM-co-PDMAC) copolymer. By combining the thermo-responsive [...] Read more.

Access to clean water remains a critical global challenge, exacerbated by population growth, industrial activity, and climate change. In response, this study presents the development and characterization of thermo-responsive and salt-adaptive ultrafiltration membranes functionalized with a poly(N-isopropylacrylamide)–co-poly(dimethylacrylamide) (PNIPAM-co-PDMAC) copolymer. By combining the thermo-responsive properties of PNIPAM with the hydrophilic characteristics of PDMAC, these membranes exhibit dual-stimuli responsiveness to temperature and ionic strength, allowing for precise control of permeability and fouling resistance. The experimental results demonstrated that the copolymer’s hydration state and dynamic pore size modulation are sensitive to changes in salinity and temperature, with sodium chloride (NaCl) significantly influencing the transition behavior. Preliminary fouling tests confirmed the antifouling capabilities of these membranes, with salt-triggered hydration transitions effectively reducing irreversible fouling and extending membrane durability. The membranes’ reversible properties and adaptability to dynamic operating conditions highlight their potential to enhance the efficiency and sustainability of water treatment processes. Future investigations will focus on scaling up the fabrication process and assessing the long-term stability of these membranes under real-world conditions. This study underscores the promise of smart membrane systems for advancing global water sustainability. Full article

(This article belongs to the Special Issue Advanced Fabrication Techniques and Applications for High-Performance Polymer Membranes)

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17 pages, 4450 KiB

Open AccessArticle

Location and Dynamics of Nymphaeol A in a Complex Membrane

by José Villalaín

Membranes 2025, 15(6), 163; https://doi.org/10.3390/membranes15060163 - 28 May 2025

Abstract

Nymphaeol A (NYA) is a tetrahydroxyflavanone anchored to a hydrophobic geranyl group, isolated from different sources and a component of propolis, a complex mixture produced by honeybees and used since ancient times as a healthy drug. This complex exhibits significant antioxidant, antifungal, antibacterial, [...] Read more.

Nymphaeol A (NYA) is a tetrahydroxyflavanone anchored to a hydrophobic geranyl group, isolated from different sources and a component of propolis, a complex mixture produced by honeybees and used since ancient times as a healthy drug. This complex exhibits significant antioxidant, antifungal, antibacterial, antiviral, anticancer and antimicrobial properties and NYA is one of its main components. NYA is a lipophilic molecule with two domains, one polar and one hydrophobic. NYA can be inserted into membranes, and its membrane properties depend not only on its location but also on the membrane’s lipid composition. This work uses molecular dynamics to obtain the dynamics, orientation, location and interactions of NYA in a complex biomembrane. This work shows that in an aqueous solution, NYA forms high-order aggregates where the molecules are joined together by the hydrophobic chain. In the presence of a membrane but initially located in the aqueous media, NYA is capable of inserting itself spontaneously into the membrane. Inside the membrane, NYA can be found in the monomeric form, as well as forming aggregates, tending to remain in its most extended conformation. NYA moves along the x-, y- and z-axes, with the movement along the z-axis larger than that of the membrane’s lipids. NYA forms an approximate angle of 35° perpendicular with respect to the membrane and is inserted between the phospholipid hydrocarbon chains, slightly increasing membrane fluidity. Furthermore, NYA prefers POPC and PSM but not POPE or CHOL. NYA’s location and movement within the membrane should be well-suited for its potent bioactivity. Full article

(This article belongs to the Special Issue Recent Advances in Biomembrane Models for Studying Interactions with Bio-/Molecules)

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46 pages, 4813 KiB

Open AccessReview

Overcoming the Limitations of Forward Osmosis and Membrane Distillation in Sustainable Hybrid Processes Managing the Water–Energy Nexus

by Muhammad Suleman, Basel Al-Rudainy and Frank Lipnizki

Membranes 2025, 15(6), 162; https://doi.org/10.3390/membranes15060162 - 26 May 2025

Abstract

Energy-efficient and cost-effective water desalination systems can significantly replenish freshwater reserves without further stressing limited energy resources. Currently, the majority of the desalination systems are operated by non-renewable energy sources such as fossil fuel power plants. The viability of any desalination process depends [...] Read more.

Energy-efficient and cost-effective water desalination systems can significantly replenish freshwater reserves without further stressing limited energy resources. Currently, the majority of the desalination systems are operated by non-renewable energy sources such as fossil fuel power plants. The viability of any desalination process depends primarily on the type and amount of energy it utilizes and on the product recovery. In recent years, membrane distillation (MD) and forward osmosis (FO) have drawn the attention of the scientific community because of FO’s low energy demand and the potential of MD operation with low-grade heat or a renewable source like geothermal, wind, or solar energy. Despite the numerous potential advantages of MD and FO, there are still some limitations that negatively affect their performance associated with the water–energy nexus. This critical review focuses on the hybrid forward osmosis–membrane distillation (FO-MD) processes, emphasizing energy demand and product quality. It starts with exploring the limitations of MD and FO as standalone processes and their performance. Based on this, the importance of combining these technologies into an FO-MD hybrid process and the resulting strengths of it will be demonstrated. The promising applications of this hybrid process and their advantages will be also explored. Furthermore, the performance of FO-MD processes will be compared with other hybrid processes like FO–nanofiltration (FO-NF) and FO–reverse osmosis (FO-RO). It will be outlined how the FO-MD hybrid process could outperform other hybrid processes when utilizing a low-grade heat source. In conclusion, it will be shown that the FO-MD hybrid process can offer a sustainable solution to address water scarcity and efficiently manage the water–energy nexus. Full article

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

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22 pages, 4021 KiB

Open AccessArticle

DPPC Membrane Under Lateral Compression and Stretching to Extreme Limits: Phase Transitions and Rupture

by Subhalaxmi Das, Nikos Ch. Karayiannis and Supriya Roy

Membranes 2025, 15(6), 161; https://doi.org/10.3390/membranes15060161 - 26 May 2025

Abstract

Dipalmitoylphosphatidylcholine (DPPC), is one of the key bilayer membranes of the phosphatidylcholine (PC) family which constitutes 40–50% of total cellular phospholipids in mammal cells. We investigate the behavior of an initially planar DPPC membrane under lateral pressures from −200 to 150 bar at [...] Read more.

Dipalmitoylphosphatidylcholine (DPPC), is one of the key bilayer membranes of the phosphatidylcholine (PC) family which constitutes 40–50% of total cellular phospholipids in mammal cells. We investigate the behavior of an initially planar DPPC membrane under lateral pressures from −200 to 150 bar at 323 K using microsecond-scale simulations. We identify, with very high precision, the pressure range for the occurrence of critical phenomena, mainly undulation and rupture. Notably, under compression, the membrane initially thickens, leading to a phase transition to an undulated state between 40 and 50 bar, as gauged by the sharp changes in the diverse structural metrics. Stretching induces systematic membrane thinning, with rupture becoming probable at −170 bar and certain at −200 bar. The reverse compression cycle shows pressure hysteresis with a 10-bar shift, while the reverse stretching cycle retraces the pathway. System size has a minimal impact on the observed trends. Under extreme mechanical stress, particularly near critical phenomena, simulation times on the order of microsecond are needed to accurately capture phase behavior and structural alterations. This work provides important insights into understanding membrane behavior under extreme conditions, which are relevant to numerous biological and technological applications. Full article

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

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22 pages, 5832 KiB

Open AccessArticle

Carbonized Dual-Layer Balsa Wood Membrane for Efficient Oil–Water Separation in Kitchen Applications

by Mamadou Souare, Changqing Dong, Xiaoying Hu, Junjiao Zhang, Juejie Xue and Quanjun Zheng

Membranes 2025, 15(6), 160; https://doi.org/10.3390/membranes15060160 - 24 May 2025

Abstract

Wood-based membranes have garnered increasing attention due to their structural advantages and durability in the efficient treatment of oily kitchen wastewater. However, conventional fabrication methods often rely on toxic chemicals or synthetic processes, generating secondary pollutants and suffering from fouling, which reduces performance [...] Read more.

Wood-based membranes have garnered increasing attention due to their structural advantages and durability in the efficient treatment of oily kitchen wastewater. However, conventional fabrication methods often rely on toxic chemicals or synthetic processes, generating secondary pollutants and suffering from fouling, which reduces performance and increases resource loss. In this study, an innovative bilayer membrane was developed from balsa wood by combining a hydrophilic longitudinal layer for water transport with a polydimethylsiloxane (PDMS)-impregnated carbonized transverse layer to enhance hydrophobicity, resulting in increased separation efficiency and a reduction in fouling by 98.38%. The results show a high permeation flux of 1176.86 Lm^–2 h^–1 and a separation efficiency of 98.60%, maintaining low fouling resistance (<3%) over 20 cycles. Mechanical tests revealed a tensile strength of 10.92 MPa and a fracture elongation of 10.42%, ensuring robust mechanical properties. Wettability measurements indicate a 144° contact angle and a 7° sliding angle with water on the carbonized side, and a 163.7° contact angle with oil underwater and a 5° sliding angle on the hydrophilic side, demonstrating excellent selective wettability. This study demonstrates the potential of carbonized wood-based membranes as a sustainable, effective alternative for large-scale wastewater treatment. Full article

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

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