Membranes

18 pages, 11223 KB

Open AccessArticle

Water Purification Efficiency and Membrane Fouling Behavior of Ceramic Membrane-Nanofiltration in Treating Water Treatment Plant Production Wastewater

by Yawei Xie, Zewei Liu, Jiayi Yu, Zizhang Shan, Hongyuan Liu and Yan Zhang

Membranes 2025, 15(12), 387; https://doi.org/10.3390/membranes15120387 - 18 Dec 2025

Viewed by 485

Abstract

To mitigate the risks associated with production wastewater from water treatment plants, this study evaluated the effectiveness of nanofiltration (NF) and a hybrid ceramic membrane–nanofiltration (CM–NF) process in removing natural organic matter (NOM) and Ca²⁺. A comprehensive analysis of changes in [...] Read more.

To mitigate the risks associated with production wastewater from water treatment plants, this study evaluated the effectiveness of nanofiltration (NF) and a hybrid ceramic membrane–nanofiltration (CM–NF) process in removing natural organic matter (NOM) and Ca²⁺. A comprehensive analysis of changes in specific flux and fouling resistance of the NF membrane, combined with scanning electron microscopy (SEM) observations, provided deeper insight into membrane fouling behavior. The results show that the CM–NF process achieved average removal rates of 95.60% for DOC, 98.55% for UV₂₅₄, 34.50% for conductivity, and 50.71% for Ca²⁺. These values represent improvements of 4.70%, 1.40%, 16.37%, and 10.36%, respectively, compared to the standalone NF process. Furthermore, CM pretreatment consistently optimized the performance of the nanofiltration system. After continuous operation, the average specific membrane flux of the CM–NF system reached 0.715, 0.67, and 0.61 under varying pollutant concentrations—increases of 10.9%, 19.6%, and 17.3% over the standalone NF system—confirming a significant improvement in permeate flux. Under continuous operation, the average degree of irreversible fouling was markedly reduced across different pollutant concentrations—decreasing from 9.2%, 17.6%, and 23.6% for the standalone NF system to 8.9%, 15.6%, and 10.9% for the CM–NF system, which clearly demonstrates the efficacy of CM pretreatment in controlling irreversible fouling. SEM observations further corroborated that CM pretreatment effectively alleviated fouling on the NF membrane surface. Additionally, higher Ca²⁺ concentrations were found to contribute to reduced membrane fouling and enhance flux performance. Full article

► Show Figures

Figure 1

17 pages, 2683 KB

Open AccessArticle

Polysulfone/Graphene Oxide Mixed Matrix Membranes for Improved CO₂/CH₄ Separation

by Mustafa Alsaady, Sharjeel Waqas, Mohammed A. Almarshoud, Khuram Maqsood, Aymn Abdulrahman and Yuying Yan

Membranes 2025, 15(12), 386; https://doi.org/10.3390/membranes15120386 - 18 Dec 2025

Viewed by 377

Abstract

This research focuses on developing and optimizing mixed matrix membranes (MMMs) by incorporating graphene oxide (GO) into a polysulfone (PSF) matrix to enhance the separation performance of CO₂ and CH₄. The morphology and gas separation performance of the MMMs were [...] Read more.

This research focuses on developing and optimizing mixed matrix membranes (MMMs) by incorporating graphene oxide (GO) into a polysulfone (PSF) matrix to enhance the separation performance of CO₂ and CH₄. The morphology and gas separation performance of the MMMs were systematically characterized. The incorporation of GO enhanced gas permeation and CO₂/CH₄ selectivity, as evaluated using a gas permeation setup. Notably, the PSF/GO-0.3 wt.% membrane exhibited superior performance, achieving a CO₂ permeability of 21.63 Barrer, among the highest reported for PSF-based MMMs. Additionally, the membrane demonstrated a CO₂/CH₄ selectivity of 14.32, highlighting its effectiveness in distinguishing between the two gases, which is essential for carbon capture and natural gas decontamination applications. The uniform distribution of GO within the polymer matrix contributed to the membrane’s enhanced performance. Furthermore, the MMMs exhibited outstanding resistance to CO₂ plasticization, with the PSF/GO-0.3 wt.% membrane maintaining its performance at pressures up to 10 bar, a significant improvement over the pristine PSF membrane, which failed at 4 bar. The improved plasticization resistance is ascribed to the reinforcing effect of GO, which stabilizes the polymer matrix, minimizing CO₂-induced swelling. The PSF/GO-0.3 wt.% membrane exhibited exceptional CO₂ permeability, selectivity, and plasticization resistance, making it a viable alternative for industrial gas separation applications and outperforming previously reported PSF-based MMMs. Full article

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

► Show Figures

Figure 1

16 pages, 3034 KB

Open AccessArticle

Synthesis and CO₂/N₂ Separation Performance Analysis of Mixed Matrix Membrane (MMM) Based on Different Bimetallic Metal–Organic Frameworks (Ni-Cu-MOF-74, Ni-Co-MOF-74, and Ni-Zn-MOF-74)

by Shoaib Ahsan, Muhammad Ahsan, Tayyaba Noor, Sarah Farrukh and Humais Roafi

Membranes 2025, 15(12), 385; https://doi.org/10.3390/membranes15120385 - 18 Dec 2025

Viewed by 453

Abstract

Polydimethylsiloxane (PDMS) is commonly used in gas-separation studies because of its high CO₂ permeability and stable mechanical properties. In this work, mixed matrix membranes (MMMs) were prepared by incorporating the bimetallic MOFs Ni-Cu-MOF-74, Ni-Co-MOF-74, and Ni-Zn-MOF-74 into a PDMS matrix. The membranes [...] Read more.

Polydimethylsiloxane (PDMS) is commonly used in gas-separation studies because of its high CO₂ permeability and stable mechanical properties. In this work, mixed matrix membranes (MMMs) were prepared by incorporating the bimetallic MOFs Ni-Cu-MOF-74, Ni-Co-MOF-74, and Ni-Zn-MOF-74 into a PDMS matrix. The membranes were fabricated by solution casting and characterized by SEM, XRD, FT-IR, and BET analyses, which confirmed uniform filler dispersion and the successful incorporation of the MOF-74 structures. Single-gas permeation tests showed clear performance improvements with MOF loading. The best results were obtained for the membrane containing 1 wt.% Ni-Cu-MOF-74, which reached a CO₂ permeability of 3188.25 Barrer and a CO₂/N₂ selectivity of 35.10. The improvement is attributed to the accessible metal sites and high surface area provided by the MOF-74 framework, which enhanced adsorption–diffusion pathways for CO₂ transport. These results show that PDMS/MOF-74 mixed-matrix membranes are effective for CO₂/N₂ separation, with Ni-Cu-MOF-74 achieving the highest performance. Full article

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

► Show Figures

Figure 1

16 pages, 5463 KB

Open AccessArticle

Preparation of Cu-MnO₂/GO/PVDF Catalytic Membranes via Phase Inversion Method and Application for Separation Removal of Dyes

by Fei Wang, Xinyu Hou, Runze He, Jiachen Song, Yifan Xie, Zhaohui Yang and Xiao Liu

Membranes 2025, 15(12), 384; https://doi.org/10.3390/membranes15120384 - 18 Dec 2025

Viewed by 323

Abstract

To address the issues of hydrophobicity, easy fouling, and limited application of polyvinylidene fluoride (PVDF) membranes in water treatment processes, this study prepared Cu-MnO₂/GO/PVDF catalytic membranes via the immersion precipitation phase inversion method. Graphene oxide (GO) was incorporated to facilitate the [...] Read more.

To address the issues of hydrophobicity, easy fouling, and limited application of polyvinylidene fluoride (PVDF) membranes in water treatment processes, this study prepared Cu-MnO₂/GO/PVDF catalytic membranes via the immersion precipitation phase inversion method. Graphene oxide (GO) was incorporated to facilitate the construction of good water channels, while copper-doped manganese dioxide (Cu-MnO₂) was added to enhance catalytic activity. The structure, morphology, and performance of the membranes were characterized comprehensively. Results showed that Cu-MnO₂ was well interspersed between GO sheets, thereby increasing membrane surface roughness, effective filtration area, and hydrophilicity. The best catalytic membrane CM-5 exhibited the highest pure water flux (1391.20 L·m⁻²·h⁻¹) and methyl blue (MBE) rejection rate (98.06%), and it also displayed excellent reusability and stability. EPR tests confirmed the generation of HO· and HOO· in the Fenton-like system, which mediated dye degradation. The Cu-MnO₂/GO/PVDF catalytic membrane demonstrated excellent hydrophilicity, antifouling properties, and catalytic efficiency, thus providing a viable solution for dye wastewater treatment. Full article

► Show Figures

Figure 1

30 pages, 3804 KB

Open AccessArticle

Evidence Supporting the Hydrophobic-Mismatch Model for Cytochrome b₆f-Driven State Transitions in the Cyanobacterium Synechocystis Species PCC 6803

by Terezia Kovacs, Laszlo Kovacs, Mihaly Kis, Michito Tsuyama, Sindhujaa Vajravel, Eva Herman, Nia Petrova, Anelia Dobrikova, Tomas Zakar, Svetla Todinova, Sashka Krumova, Zoltan Gombos and Radka Vladkova

Membranes 2025, 15(12), 383; https://doi.org/10.3390/membranes15120383 - 17 Dec 2025

Viewed by 296

Abstract

While there is a consensus that the cytochrome b₆f complex (cytb₆f) in algae and plants is involved in the regulatory mechanism of oxygenic photosynthesis known as light-induced state transitions (STs), no such consensus exists for cyanobacteria. Here, [...] Read more.

While there is a consensus that the cytochrome b₆f complex (cytb₆f) in algae and plants is involved in the regulatory mechanism of oxygenic photosynthesis known as light-induced state transitions (STs), no such consensus exists for cyanobacteria. Here, we provide the first direct functional evidence for cytb₆f using single-point mutation data. We introduced a PetD-Phe124Ala substitution in the cyanobacterium Synechocystis sp. PCC 6803 to test the key predictions of the hydrophobic-mismatch (HMM) model for cytb₆f-driven STs in all oxygenic photosynthetic species. These predictions concern the role of the Phe/Tyr124^fg^-loop-PetD and the extent and kinetic characteristics of STs. The effects of PetD-F124A mutation on STs were monitored using 77K and Pulse-Amplitude-Modulated (PAM) fluorescence. For comparison, we employed a phycobilisome (PBS)-less Synechocystis mutant and wild-type (WT) strain, as well as the stn7 mutant and WT of Arabidopsis plant. The PetD-F124A mutation reduced the extent of STs and selectively affected the two-exponential kinetics components of the transitions. Under State 1 conditions, the mutant exhibited ~60% less energetic decoupling of PBS from photosystem I (PSI) compared to the WT. It is explainable by the HMM model with the inability of the PetD-F124A mutant, during the induction phase of the State 2→State 1 transition to adopt the cytb₆f conformation with minimal hydrophobic thickness. PAM-derived parameters indicated that PSII electron transport function is not inhibited, and no detectable effect on cyclic electron transport around PSI was observed under low-light conditions. Circular dichroism and differential scanning calorimetry confirmed that both the PSI trimer/monomer ratio and the structural integrity of the PBSs are preserved in the mutant. The compensatory response to the mutation includes decreased PSI content and an increase in PBS rod size. In conclusion, (1) cytb₆f is involved in cyanobacterial STs; (2) evidence is provided supporting the HMM model; (3) the electron transfer and signal transduction functions of cytb₆f are separated into distinct domains; and (4) the signaling pathway regulating STs and pigment-protein composition in Synechocystis involves PetD-Phe124. Full article

(This article belongs to the Section Biological Membranes)

► Show Figures

Figure 1

22 pages, 5738 KB

Open AccessReview

Probing Membrane Structure of Lipid Nanomedicines Using Solution Small-Angle X-Ray Scattering: Applications and Prospects

by Ke-Meng Li, Panqi Song, Xiao-Peng He and Na Li

Membranes 2025, 15(12), 382; https://doi.org/10.3390/membranes15120382 - 16 Dec 2025

Viewed by 632

Abstract

Lipid-based nanomedicines are already widely used in antitumor therapy and gene delivery. However, their complex structural features demand advanced mesoscopic structural characterization tools for effective research and development (R&D) and quality control. Synchrotron small-angle X-ray scattering (SAXS) is a powerful, non-invasive technique for [...] Read more.

Lipid-based nanomedicines are already widely used in antitumor therapy and gene delivery. However, their complex structural features demand advanced mesoscopic structural characterization tools for effective research and development (R&D) and quality control. Synchrotron small-angle X-ray scattering (SAXS) is a powerful, non-invasive technique for probing nanoscale membrane organizations, monitoring in situ dynamic membrane assembly, and exploring the interactions of components in lipid-based drug delivery systems, including liposomes, lipoplexes, lipid nanoparticles (LNPs), and lyotropic liquid crystals (LLCs). Recent advances in high-flux synchrotron facilities, high-frequency detectors, and automated SAXS data processing pipelines permit a detailed structural characterization of lamellarity, bilayer spacing, internal phases, core–shell morphology, as well as “pump-probe” dynamic process studies for lipid nanomedicines. Though major challenges remain in sample polydispersity and model fitting, the advances in time-resolved synchrotron SAXS, high-throughput automation, and artificial intelligence (AI)-assisted modeling are rapidly reducing this barrier. This review summarizes SAXS methodology and introduces representative case studies in the field of lipid nanomedicines. The performance of BioSAXS beamline BL19U2 in the Shanghai synchrotron radiation facility (SSRF) and prospects of AI-guided drug screening at BL19U2 are highlighted to advance intelligent R&D and quality control for lipid nanomedicines. Full article

(This article belongs to the Special Issue Interfacial Interactions of Nanoparticles and Molecular Nanostructures with Model Membrane Systems)

► Show Figures

Graphical abstract

10 pages, 778 KB

Open AccessPerspective

Hypoxia as a Central Regulator of Plasma Membrane Phosphohydrolase Enzymes: Possible Roles in Extracellular Phosphate Generation and Adenosine Metabolism

by Pedro Henrique Silva de Oliveira, Beatriz Bereda Silva-Freitas, José Roberto Meyer-Fernandes and Marco Antonio Lacerda-Abreu

Membranes 2025, 15(12), 381; https://doi.org/10.3390/membranes15120381 - 15 Dec 2025

Viewed by 459

Abstract

This article presents a conceptual perspective proposing that hypoxia acts as a unifying regulator of plasma membrane phosphohydrolases. We propose that oxygen sensing at the cell surface integrates adenosine and phosphate metabolism to sustain tumour adaptation. Within the oxygen- and nutrient-deprived tumour microenvironment, [...] Read more.

This article presents a conceptual perspective proposing that hypoxia acts as a unifying regulator of plasma membrane phosphohydrolases. We propose that oxygen sensing at the cell surface integrates adenosine and phosphate metabolism to sustain tumour adaptation. Within the oxygen- and nutrient-deprived tumour microenvironment, inorganic phosphate (Pi) and adenosine function as metabolic substrates and signalling mediators that promote cell proliferation, survival, and immune evasion. Stabilisation of hypoxia-inducible factor-1α (HIF-1α) enhances the expression and catalytic activity of specific phosphohydrolases, notably the ectonucleotidases CD39 (NTPDase1) and CD73 (ecto-5′-nucleotidase), which drive adenosine accumulation and immunosuppression. Conversely, the activity of transmembrane prostatic acid phosphatase (TM-PAP), responsible for hydrolysing phosphate esters such as p-nitrophenylphosphate (pNPP) and AMP, is inhibited under hypoxia through oxidative and kinase-dependent mechanisms. Collectively, these mechanisms characterise the plasma membrane as a dynamic metabolic interface, where oxygen sensing coordinates adenosine and phosphate turnover, thereby promoting tumour adaptation across hypoxic environments. We propose that hypoxia orchestrates a dual regulatory loop connecting adenosine accumulation and phosphate turnover at the tumour cell surface, providing a conceptual basis for future mechanistic studies. Full article

► Show Figures

Figure 1

23 pages, 2846 KB

Open AccessArticle

Exploring the Potentials of Membrane Gas Separation for CO Concentration After Plasma Catalytic CO₂ Splitting

by Daria Miroshnichenko, Evgenia Grushevenko, Maxim Shalygin, Dmitry Matveev, Ilya Borisov, Anton Maximov and Stepan Bazhenov

Membranes 2025, 15(12), 380; https://doi.org/10.3390/membranes15120380 - 13 Dec 2025

Viewed by 525

Abstract

Today, reducing carbon footprints requires the development of technologies to utilize CO₂, particularly by converting it into valuable chemical products. One approach is plasma-catalytic CO₂ splitting into CO and O₂. The task of separating such a ternary mixture [...] Read more.

Today, reducing carbon footprints requires the development of technologies to utilize CO₂, particularly by converting it into valuable chemical products. One approach is plasma-catalytic CO₂ splitting into CO and O₂. The task of separating such a ternary mixture is nontrivial and requires the development of an efficient method. In this paper, we have developed a comprehensive scheme for the separation of a CO₂/CO/O₂ mixture using membrane technology. The novelty of this work lies in the development of a complete scheme for separating the products of plasma-chemical decomposition of CO₂ to produce a CO concentrate. The calculations utilized the principle of a reasonable balance between the recovery rate and the energy consumption of the separation process. This scheme allows production of a CO stream with a purity of 99%. To achieve this goal, we have proposed the sequential use of CO₂-selective membranes based on polysiloxane with oligoethyleneoxide side groups (M-PEG), followed by polysulfone (PSF) hollow-fiber membranes to separate CO and O₂. For these membranes, we measured the CO permeability for the first time and obtained the selectivity for CO₂/CO and O₂/CO. The potential of membrane separation was demonstrated through a three-stage process, which includes recycling of the CO removal stream and concentration after CO₂ plasmolysis. This process was calculated to yield a highly pure CO stream containing 99 mol% with a recovery rate of 47.9–69.4%. The specific energy consumption for the separation process was 30.31–0.83 kWh per 1 m³ of feed mixture, and the required membrane area was between 0.1 m² for M-PEG and 42.5–107 m² for PSF, respectively. Full article

(This article belongs to the Special Issue Recent Developments in Membrane Technologies for Efficient Gas Separation: Innovations and Applications)

► Show Figures

Graphical abstract

18 pages, 3661 KB

Open AccessArticle

Effects of Metal Foam Insertion on the Performance of a Vacuum Membrane Distillation Unit

by Nizar Loussif and Jamel Orfi

Membranes 2025, 15(12), 379; https://doi.org/10.3390/membranes15120379 - 13 Dec 2025

Viewed by 341

Abstract

The present study investigates the use of aluminum foam to enhance pure water production using a Vacuum Membrane Distillation (VMD) desalination unit. Numerical simulations were conducted for a conventional VMD and three VMD configurations with different metal foam thickness-to-channel-width ratios of h/b = [...] Read more.

The present study investigates the use of aluminum foam to enhance pure water production using a Vacuum Membrane Distillation (VMD) desalination unit. Numerical simulations were conducted for a conventional VMD and three VMD configurations with different metal foam thickness-to-channel-width ratios of h/b = (0.5, 0.75, 1). The effects of operational parameters on different VMD setups were presented and discussed. Additionally, the effects of flow rates on temperature polarization, average Nusselt number, and pressure drop were presented and discussed. The performance evaluation criterion (PEC), an indicator of the system’s global performance encompassing the heat transfer enhancement and the related pressure loss, has also been used and analyzed. Outcomes demonstrate improvements in water production with the increase in inlet velocity and temperature, while applied vacuum pressure and inlet concentration increments showed opposite behavior for all studied VMD setups. Permeate flux and temperature polarization were enhanced with metal foam insertion, and the case h = b presents the highest permeate flux and pressure drop. PEC demonstrates values superior to unity for all studied cases, with higher values for lower flow rates. Fully filled metal foam insertion is recommended for lower flow rates, while partially filled metal foam (h = 0.5b) is suggested for higher ones. Full article

(This article belongs to the Special Issue Membrane Distillation: Module Design and Application Performance)

► Show Figures

Figure 1

17 pages, 2370 KB

Open AccessArticle

Study on Specific Energy Consumption of Rotating Dynamic Filtration for Ship EGC Desulfurization Wastewater Treatment

by Shiyong Wang, Baohua Yang, Juan Wu, Yanlin Wu and Wenbo Dong

Membranes 2025, 15(12), 378; https://doi.org/10.3390/membranes15120378 - 9 Dec 2025

Viewed by 364

Abstract

In recent decades, rotating dynamic filtration (RDF) has attracted considerable attention due to its high efficiency and low energy consumption. While most studies have focused on separation behavior and membrane fouling, energy consumption in RDF has received limited attention. This study investigates the [...] Read more.

In recent decades, rotating dynamic filtration (RDF) has attracted considerable attention due to its high efficiency and low energy consumption. While most studies have focused on separation behavior and membrane fouling, energy consumption in RDF has received limited attention. This study investigates the specific energy consumption (SEC) of the RDF process for ship exhaust gas cleaning (EGC) desulfurization wastewater treatment and proposes an optimization method based on both energy consumption and equipment cost. The total SEC increases with rotational velocity, circulation flow, feed concentration, and membrane size but decreases with temperature and remains unaffected by the number of membrane elements. In RDF, the total SEC is only 9.05–19.29% of that in tubular cross-flow filtration (CFF) at equivalent shear force ranging from 3.86 Pa to 121.14 Pa. Operating energy and investment costs are primarily determined by the number of membrane elements and the rotational velocity. According to the economic analysis, the lowest treatment cost for EGC wastewater is CNY 6.09 per cubic meter for a 5 m³·h⁻¹ capacity, using 84 membrane elements (374 mm, 0.2 µm) at a rotational velocity of 200 rpm, an operating pressure of 200 kPa, and a temperature of 40 °C. Full article

► Show Figures

Figure 1

23 pages, 3500 KB

Open AccessReview

Recent Advances in Advanced Membrane Materials for Natural Gas Purification: A Review of Material Design and Separation Mechanisms

by Qijie Fan, Rui Xiao, Cheng Yang, Meixuan Xin, Xia Zheng and Guangyong Zeng

Membranes 2025, 15(12), 377; https://doi.org/10.3390/membranes15120377 - 9 Dec 2025

Cited by 1 | Viewed by 856

Abstract

Natural gas plays a pivotal role in the global energy landscape under the dual challenges of energy transition and climate change. However, the impurities present within natural gas pose several disadvantages, including corrosion of transportation pipelines, toxicity, hydrate formation, and a reduction in [...] Read more.

Natural gas plays a pivotal role in the global energy landscape under the dual challenges of energy transition and climate change. However, the impurities present within natural gas pose several disadvantages, including corrosion of transportation pipelines, toxicity, hydrate formation, and a reduction in the fuel’s calorific value. Membrane separation technology has been recognized as an ideal approach for natural gas purification owing to its advantages of low energy consumption, operational simplicity, and excellent separation performance. This review summarizes recent progress in the development of advanced membrane materials, including polymer bulk membranes, two-dimensional (2D) nanosheet membranes, mixed-matrix membranes (MMMs), surface-modified membranes, and carbon molecular sieve membranes (CMSMs). The fundamental separation mechanisms—such as solution-diffusion, molecular sieving, adsorption-selectivity, and competitive sorption and surface diffusion—are analyzed in detail. Moreover, the critical scientific questions and technological challenges in this field are discussed in depth. Finally, future research perspectives are proposed to guide the rational design and practical application of high-performance membranes for natural gas separation. Full article

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

► Show Figures

Figure 1

22 pages, 1697 KB

Open AccessReview

Advances in Reference Membranes for Potentiometric Sensing Applications

by Martyna Drużyńska, Nikola Lenar and Beata Paczosa-Bator

Membranes 2025, 15(12), 376; https://doi.org/10.3390/membranes15120376 - 6 Dec 2025

Viewed by 705

Abstract

Accurate potentiometric sensing critically depends on the stability and reproducibility of the reference electrode potential. Conventional liquid-filled Ag/AgCl or calomel electrodes, though well-established, are poorly compatible with miniaturized, portable, or long-term in situ sensing devices due to electrolyte leakage, junction potential instability, and [...] Read more.

Accurate potentiometric sensing critically depends on the stability and reproducibility of the reference electrode potential. Conventional liquid-filled Ag/AgCl or calomel electrodes, though well-established, are poorly compatible with miniaturized, portable, or long-term in situ sensing devices due to electrolyte leakage, junction potential instability, and maintenance requirements. Recent advances in solid-state and membrane-based reference electrodes offer a promising alternative by eliminating the liquid junction while maintaining stable and well-defined potential. This review summarizes the advancements in polymer-based and composite reference membranes, focusing on material strategies, stabilization mechanisms, and integration approaches. Emphasis is placed on ionic-liquid-doped membranes, conducting polymers, lipophilic salts, and carbon nanomaterials as functional components enhancing interfacial stability and charge transfer. The performances of various architectures, solid-contact, liquid-junction-free, and quasi-reference systems, are compared in terms of potential drift, matrix resistance, biocompatibility, and manufacturability. Furthermore, recent developments in printed, microfluidic, and wearable potentiometric platforms demonstrate how reference membrane innovations enable reliable operation in compact, low-cost, and flexible analytical systems. The review outlines current trends, challenges, and future directions toward universal, miniaturized, and leak-free reference electrodes suitable for innovative sensing technologies. Full article

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

► Show Figures

Figure 1

24 pages, 5297 KB

Open AccessArticle

A Hybrid CFD Platform for Colloidal Fouling Prediction in Electrodialysis

by Francesco Volpe, Giuseppe Battaglia, Andrea Cipollina, Giorgio Micale and Alessandro Tamburini

Membranes 2025, 15(12), 375; https://doi.org/10.3390/membranes15120375 - 6 Dec 2025

Viewed by 490

Abstract

Fouling phenomena are among the main issues in membrane processes, worsening unit performance and membrane properties. So far, few modelling approaches have been proposed to predict colloidal fouling in electromembrane-based technologies. This work presents an original simulation platform that couples computational fluid dynamics [...] Read more.

Fouling phenomena are among the main issues in membrane processes, worsening unit performance and membrane properties. So far, few modelling approaches have been proposed to predict colloidal fouling in electromembrane-based technologies. This work presents an original simulation platform that couples computational fluid dynamics (CFD) simulations with electrodialysis (ED) and colloidal fouling models to investigate the impact of colloidal deposition at the channel and unit scales of ED systems. Fluid dynamics, salt transport and fouling layer growth were all addressed. The model was calibrated and validated with colloidal fouling data from the literature. The regions more susceptible to fouling growth were identified. Polarization phenomena, as well as the increase in pressure losses and electrical resistance over time, were evaluated. Full article

(This article belongs to the Special Issue Electrodialysis and Reverse Electrodialysis in Ion-Exchange Membrane Systems)

► Show Figures

Graphical abstract

12 pages, 3120 KB

Open AccessArticle

A Camphorsulfonic Acid-Grafted Polybenzimidazole Ion Selectivity Membrane for Vanadium Redox Flow Battery

by Yujie Guo, Bo Pang, Fujun Cui, Tingxu Fang, Li Tian, Liu Yang, Zeyu Chen and Xuemei Wu

Membranes 2025, 15(12), 374; https://doi.org/10.3390/membranes15120374 - 5 Dec 2025

Viewed by 409

Abstract

The design of the chemical structure of ion-conductive membranes is critical to enhance proton/vanadium ion selectivity and the performance of vanadium redox flow batteries (VRFBs). Herein, camphorsulfonic acid is proposed as a novel proton-conductive group and grafted on polybenzimidazole (PBICa). The pendant sulfonic [...] Read more.

The design of the chemical structure of ion-conductive membranes is critical to enhance proton/vanadium ion selectivity and the performance of vanadium redox flow batteries (VRFBs). Herein, camphorsulfonic acid is proposed as a novel proton-conductive group and grafted on polybenzimidazole (PBICa). The pendant sulfonic acid group on the end of the grafted side chains is flexible to promote the aggregation of ionic clusters at even a relatively low ion-exchange capacity (IEC) of 2.14 mmol g⁻¹. The formation of these high-quality clusters underscores the remarkable efficacy of this structural strategy in driving nanoscale phase separation, which is a prerequisite for creating efficient proton-conducting pathways. The bulky and non-coplanar architecture of the camphorsulfonic acid group helps to increase the proportion of free volume compared with the conventional sulfonated polybenzimidazole, which not only promotes water uptake to facilitate proton transport but also exerts a sieving effect to effectively block vanadium ion permeation. The well-formed ionic clusters, together with the expanded free volume architecture, endow the membrane with both high proton conductivity (30.5 mS cm⁻¹) and low vanadium ion permeability (0.15 × 10⁻⁷ cm² s⁻¹), achieving excellent proton/vanadium ion selectivity of 9.85 × 10⁹ mS s cm⁻³, which is about 5.6-fold that of a Nafion 212 membrane. Operating at 200 mA cm⁻², the PBICa-based VRFB achieves an energy efficiency of 78.4% and a discharge capacity decay rate of 0.32% per cycle, outperforming the Nafion 212-based battery (EE of 76.9%, capacity decay of 0.79% per cycle). Full article

(This article belongs to the Special Issue Advanced Membranes for Fuel Cells and Redox Flow Batteries)

► Show Figures

Figure 1

15 pages, 9628 KB

Open AccessArticle

Curvature-Induced Membrane Remodeling by the Cell-Penetrating Peptide Pep-1

by Yasith Indigahawela Gamage and Jianjun Pan

Membranes 2025, 15(12), 373; https://doi.org/10.3390/membranes15120373 - 3 Dec 2025

Viewed by 566

Abstract

The cell-penetrating peptide Pep-1 interacts with lipid membranes through combined electrostatic and hydrophobic forces, yet the structural details of its membrane remodeling activity remain unclear. Using atomic force microscopy (AFM), we examined how Pep-1 perturbs supported lipid bilayers of varying composition and geometry. [...] Read more.

The cell-penetrating peptide Pep-1 interacts with lipid membranes through combined electrostatic and hydrophobic forces, yet the structural details of its membrane remodeling activity remain unclear. Using atomic force microscopy (AFM), we examined how Pep-1 perturbs supported lipid bilayers of varying composition and geometry. In zwitterionic POPC bilayer patches, Pep-1 preferentially targeted patch boundaries, where lipid packing is less constrained, leading to edge erosion and detergent-like disintegration. Incorporation of anionic POPS enhanced peptide binding and localized disruption, giving rise to elevated annular rims, holes, and peptide–lipid aggregates. In cholesterol-containing POPC bilayer patches, Pep-1 induced extensive surface reorganization marked by protruded, ridge-like features, consistent with lipid redistribution and curvature generation. In continuous POPC/POPS bilayers lacking free edges, Pep-1 formed discrete, flower-like protrusions that coalesced into an interconnected network of thickened peptide-rich domains. These findings reveal composition-dependent remodeling pathways in which Pep-1 destabilizes, reorganizes, or curves membranes according to their mechanical and electrostatic properties, providing new insight into peptide–membrane interactions relevant to cell-penetrating peptide translocation. Full article

(This article belongs to the Special Issue Membranes: Where Chemistry and Physics Converge for Biology)

► Show Figures

Figure 1

18 pages, 3501 KB

Open AccessArticle

High-Performance Zeolite Membranes and Natural Gas Upgrading

by Margarita Kuznetsova, Christophe Castel, Bernardetta Addis, Veronica Piccialli and Eric Favre

Membranes 2025, 15(12), 372; https://doi.org/10.3390/membranes15120372 - 3 Dec 2025

Viewed by 590

Abstract

Natural gas is currently increasingly used in an energy transition framework and systematically requires upgrading processes in order to respect pipeline specifications. Carbon dioxide, and in some case hydrogen sulfide removal, is the major target of the purification step and can be achieved [...] Read more.

Natural gas is currently increasingly used in an energy transition framework and systematically requires upgrading processes in order to respect pipeline specifications. Carbon dioxide, and in some case hydrogen sulfide removal, is the major target of the purification step and can be achieved thanks to gas liquid absorption with chemical solvents or membrane separation. A systematic comparison of the cheap, currently used polymeric membranes and an expensive, high-performance zeolite material is reported on a natural gas upgrading case study (CH₄/CO₂ mixture), thanks to a dedicated process synthesis and optimization code (MIND). The zeolite membrane is shown to offer a simple, cost-effective one-stage process, while polymeric materials require more expensive classical two-stage processes. In a second step the impact of concentration polarization is more specifically investigated, through a process simulation study. The zeolite membrane remains the simplest, best cost-effective and most interesting process (one stage without compression, expander or vacuum pump). Full article

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

► Show Figures

Figure 1

23 pages, 5008 KB

Open AccessArticle

Analysis of Fouling in Hollow Fiber Membrane Distillation Modules for Desalination Brine Reduction

by Hyeongrak Cho, Seoyeon Lee, Yongjun Choi, Sangho Lee and Seung-Hyun Kim

Membranes 2025, 15(12), 371; https://doi.org/10.3390/membranes15120371 - 2 Dec 2025

Viewed by 526

Abstract

Membrane distillation (MD) is a promising technology for reducing the volume of high-salinity brines generated from desalination plants, yet limited knowledge exists regarding its fouling behavior under long-term operation. In this study, fouling was investigated through the autopsy of a hollow fiber MD [...] Read more.

Membrane distillation (MD) is a promising technology for reducing the volume of high-salinity brines generated from desalination plants, yet limited knowledge exists regarding its fouling behavior under long-term operation. In this study, fouling was investigated through the autopsy of a hollow fiber MD module operated for 120 days in a direct contact membrane distillation (DCMD) configuration using real desalination brine. Despite stable salt rejection exceeding 99%, a gradual decline in flux and permeability was observed, indicating progressive fouling and partial wetting. Post-operation analyses, including SEM, EDS, ICP-OES, and FT-IR, revealed that the dominant foulants were inorganic scales, particularly calcium carbonate (CaCO₃), with minor contributions from suspended particles (SiO₂, Fe) and organic matter. Fouling was more severe in the inlet and inner regions of the module due to intensified temperature and concentration polarization, which promoted supersaturation and scale deposition. These combined effects led to a reduction in membrane hydrophobicity and liquid entry pressure, ultimately accelerating partial wetting and performance deterioration. The findings provide valuable insights into the spatial fouling behavior and mechanisms in MD systems, highlighting the importance of hydrodynamic optimization and fouling mitigation strategies for long-term brine concentration applications. Full article

(This article belongs to the Special Issue Membrane Distillation: Module Design and Application Performance)

► Show Figures

Figure 1

13 pages, 1460 KB

Open AccessArticle

Numerical Assessment of Elliptical Pore Orientation and Eccentricity Effects on Charge Transport in Anisotropic Functional Membranes

by Carlos Pacheco, Alfonso Navarro, Enrique Escobedo and Romeli Barbosa

Membranes 2025, 15(12), 370; https://doi.org/10.3390/membranes15120370 - 2 Dec 2025

Viewed by 431

Abstract

The transport efficiency of anisotropic functional membranes is largely dictated by the geometry and orientation of their internal pores. In this study, a numerical finite-volume framework was developed to evaluate how elliptical pore eccentricity (

ε c c

) and orientation influence charge [...] Read more.

The transport efficiency of anisotropic functional membranes is largely dictated by the geometry and orientation of their internal pores. In this study, a numerical finite-volume framework was developed to evaluate how elliptical pore eccentricity (

ε c c

) and orientation influence charge transport and effective conductivity (

e_{k}

) within two-dimensional porous membrane microstructures. Canonical stochastic domains with controlled porosity were generated, considering parallel and perpendicular aligned configurations of the major pore axis relative to the imposed potential gradient. Results demonstrated a strong orientation dependence: under perpendicular alignment, the effective conductivity decreased by up to 70% as εcc increased from 0.5 to 0.999, while parallel alignment maintained at

e_{k}

> 0.8 even for highly elongated pores. The aspect ratio

(b / a)

was identified as a secondary geometric modulator producing opposite conductivity trends depending on orientation. Through isotropy-error analysis, a critical morphological threshold at

ε c c

≈ 0.9 was found, indicating the onset of structural anisotropy and loss of isotropic transport. These results establish a quantitative structure–property relationship linking pore geometry to macroscopic transport performance. The proposed stochastic FVM-based approach provides a generalizable and computationally efficient tool for the design and optimization of anisotropic porous membranes used in electrochemical and energy-conversion devices. Full article

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

► Show Figures

Figure 1

13 pages, 7084 KB

Open AccessArticle

Quantitative Analysis of Protein Fouling in Virus Removal Filtration Membranes Through Electron Tomography

by Mohammad A. Afzal, Kaitlyn P. Brickey, Enrique D. Gomez and Andrew L. Zydney

Membranes 2025, 15(12), 369; https://doi.org/10.3390/membranes15120369 - 2 Dec 2025

Viewed by 436

Abstract

Protein fouling can significantly reduce the filtrate flux, capacity, and virus retention during processing of plasma- or mammalian cell-derived biopharmaceuticals through virus removal filters. We use focused ion beam (FIB) milling and scanning electron microscopy (SEM) to directly evaluate changes in 3D pore [...] Read more.

Protein fouling can significantly reduce the filtrate flux, capacity, and virus retention during processing of plasma- or mammalian cell-derived biopharmaceuticals through virus removal filters. We use focused ion beam (FIB) milling and scanning electron microscopy (SEM) to directly evaluate changes in 3D pore structure in a Viresolve^® Pro membrane due to fouling by human serum immunoglobulin G. Protein fouling causes a significant reduction in the membrane porosity, which decreases by approximately 40% in the size-selective region near the exit of the highly asymmetric Viresolve^® Pro membrane after the filter is fouled to 90% flux decline. There is a corresponding reduction in the number of small pores by more than a factor of two. Model simulations of flow and particle transport in the protein-fouled membrane are in good agreement with independent experimental measurements of the permeability and location of particle capture. Simulations show an upstream shift in the location of nanoparticle capture (away from the filter exit) by about 0.4 µm for the membrane fouled to 90% flux decline. This is due to pore constriction from protein deposition, highlighting how fouling redistributes flow paths within the membrane. These results demonstrate the capability of using FIB-SEM to directly evaluate the effects of protein fouling on the 3D pore structure in virus removal filters, providing important insights into how protein fouling alters the performance of these highly selective membranes. Full article

► Show Figures

Graphical abstract

17 pages, 1560 KB

Open AccessReview

Biological Breakthroughs and Drug Discovery Revolution via Cryo-Electron Microscopy of Membrane Proteins

by Vitor Hugo Balasco Serrão

Membranes 2025, 15(12), 368; https://doi.org/10.3390/membranes15120368 - 1 Dec 2025

Viewed by 1456

Abstract

The application of cryo-electron microscopy (cryo-EM) in membrane protein structural biology has catalyzed unprecedented advances in our understanding of fundamental biological processes and transformed drug discovery paradigms. This review briefly describes the biological achievements enabled using cryo-EM techniques, including single particle analysis (SPA), [...] Read more.

The application of cryo-electron microscopy (cryo-EM) in membrane protein structural biology has catalyzed unprecedented advances in our understanding of fundamental biological processes and transformed drug discovery paradigms. This review briefly describes the biological achievements enabled using cryo-EM techniques, including single particle analysis (SPA), micro-electron diffraction (microED), and subtomogram averaging (STA), in elucidating the structures and functions of membrane proteins, ion channels, transporters, and viral glycoproteins. We highlight how these structural insights have revealed druggable sites, enabled structure-based drug design, and provided mechanistic understanding of disease processes. Key biological targets include G protein-coupled receptors (GPCRs), ion channels implicated in neurological disorders, respiratory chain complexes, viral entry machinery, and membrane transporters. The integration of cryo-EM with computational drug design has already yielded clinical candidates and approved therapeutics, marking a new era in membrane protein pharmacology. Full article

(This article belongs to the Special Issue Biomolecular Interactions with Cell and Model Membranes: Integrating Biophysical Experiments and Computational Simulations)

► Show Figures

Figure 1

32 pages, 2576 KB

Open AccessArticle

Advancing Solvent Dehydration with Innovative HybSi^® AR Membranes: Economic and Environmental Benefits of Pervaporation

by Mohammed Nazeer Khan, Elmar Boorsma, Pieter Vandezande, Ilse Lammerink, Rob de Lange, Anita Buekenhoudt and Miet Van Dael

Membranes 2025, 15(12), 367; https://doi.org/10.3390/membranes15120367 - 1 Dec 2025

Viewed by 686

Abstract

A techno-economic and environmental evaluation of dehydrating five industrially relevant solvents (isopropanol, acetonitrile, tetrahydrofuran, acetic acid, and n-methyl-2-pyrrolidone) using pervaporation-based processes was performed and compared to their respective traditional distillation processes. A standalone pervaporation and two hybrid processes (i.e., distillation-pervaporation and distillation-pervaporation-distillation) employing [...] Read more.

A techno-economic and environmental evaluation of dehydrating five industrially relevant solvents (isopropanol, acetonitrile, tetrahydrofuran, acetic acid, and n-methyl-2-pyrrolidone) using pervaporation-based processes was performed and compared to their respective traditional distillation processes. A standalone pervaporation and two hybrid processes (i.e., distillation-pervaporation and distillation-pervaporation-distillation) employing HybSi^® AR membranes were simulated in Aspen Plus, where the pervaporation module was modeled as a separator block that followed the experimental data. The experiments were performed at a vacuum pressure of 20 mbar and a temperature of 130 °C. The performance was compared based on several technical, economic, and environmental measures, of which key metrics are the levelized cost of separation (LCOS) and CO₂ footprint reduction. From the economic perspective, the pervaporation-based processes are much more economical than the distillation processes for isopropanol (up to 42% reduction in LCOS) and acetonitrile (up to 39% reduction in LCOS), while their economic performance is similar to the benchmark process in the case of tetrahydrofuran (only up to 4% reduction in LCOS). For acetic acid (9% higher LCOS) and n-methyl-2-pyrrolidone (124% higher LCOS), the pervaporation-based processes do not perform better than the distillation processes under the current technical and economic considerations. However, a sensitivity analysis showed the potential to make the pervaporation-based processes more economical by improving the permeate flux and membrane module cost. On the other hand, the pervaporation-based processes are much more environmentally friendly for all the solvents studied compared to their respective benchmark processes. The reduction in CO₂ footprint is in the order of 86%, 82%, 73%, 82%, and 65%, respectively, for the aforementioned solvents. Full article

(This article belongs to the Special Issue Sustainable Advances in Oil & Gas, Mining, and Environmental Technologies: Innovations in Membrane and Porous Material Technologies)

► Show Figures

Figure 1

20 pages, 2337 KB

Open AccessArticle

The Evaluation of Ammonium Sulphate as a Potential Draw Solute in a Hybrid FO-RO Process to Concentrate Nutrients (NPK) from a Simulated Liquid Digestate—Part I: Deionized Water as a Feed Solution

by Marsa Tolouei, Roshan Abraham, Niloofar Abdehagh, Majid Sartaj and Boguslaw Kruczek

Membranes 2025, 15(12), 366; https://doi.org/10.3390/membranes15120366 - 1 Dec 2025

Viewed by 399

Abstract

The ultimate objective of this research is to concentrate nutrients—nitrogen (N), phosphorus (P), and potassium (K)—and produce process water from a chemically pretreated liquid digestate using an FO-RO hybrid process. However, in this manuscript, we assessed the suitability of (NH₄)₂ [...] Read more.

The ultimate objective of this research is to concentrate nutrients—nitrogen (N), phosphorus (P), and potassium (K)—and produce process water from a chemically pretreated liquid digestate using an FO-RO hybrid process. However, in this manuscript, we assessed the suitability of (NH₄)₂SO₄ and NaCl as draw solutes in a series of FO experiments employing a commercial CTA membrane and DI water as the feed solution. We also examined the regeneration of (NH₄)₂SO₄ in a series of RO experiments at various feed concentrations and pressures using a commercial polyamide (PA) thin-film composite (TFC) membrane, ACM4. Additionally, the RO experiments enabled the experimental determination of the osmotic pressure of (NH₄)₂SO₄ at various feed concentrations, which is crucial for designing the FO part of the hybrid process. The CTA membrane exhibited a significantly greater selectivity for (NH₄)₂SO₄ than for NaCl at any osmotic pressure. The RO experiments demonstrated the possibility of reconcentrating (NH₄)₂SO₄ to 0.5 mol/L, with a corresponding water flux of 60 L h⁻¹ m⁻² at 40 bars. The experimentally determined osmotic pressures were lower than those predicted by van’t Hoff’s equation but were consistent with those reported in the literature using an indirect hygrometric method. Full article

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

► Show Figures

Figure 1

15 pages, 1659 KB

Open AccessArticle

Simple Analytical Approximations for Donnan Ion Partitioning in Permeable Ion-Exchange Membranes Under Reverse Electrodialysis Conditions

by Antonio Ángel Moya

Membranes 2025, 15(12), 365; https://doi.org/10.3390/membranes15120365 - 1 Dec 2025

Viewed by 534

Abstract

Reverse electrodialysis (RED) is a relatively recent technology for renewable energy harvesting from the interaction of river and seawater. This paper revisits the thermodynamic equilibrium governing the ionic transport processes through ion-exchange membranes (IEMs) under RED conditions and theoretically derives approximate analytical expressions [...] Read more.

Reverse electrodialysis (RED) is a relatively recent technology for renewable energy harvesting from the interaction of river and seawater. This paper revisits the thermodynamic equilibrium governing the ionic transport processes through ion-exchange membranes (IEMs) under RED conditions and theoretically derives approximate analytical expressions for the ionic concentrations at the inner boundaries of a permeable membrane with well-stirred baths. The equation for the Donnan ion partitioning at the membrane–solution interface, which is based on the equality of the electrochemical potential in the two phases, is analysed for binary salts with symmetric (1:1) and asymmetric (2:1) electrolytes, by considering bathing solutions with the equivalent concentrations 0.02 M in the dilute bath, and 0.5, 1, and 1.5 M in the concentrate one. Simple approximate analytical expressions exhibiting the evolution with the membrane fixed-charge concentration of the counter-ionic concentrations at the inner boundaries of the membrane, the concentration gradients inside the membrane, the total Donnan electric potential, and the ionic partitioning coefficients have been derived. The approximate generalised expressions for a general z₁:z₂ binary electrolyte are also presented for the first time. Full article

(This article belongs to the Special Issue Electrodialysis and Reverse Electrodialysis in Ion-Exchange Membrane Systems)

► Show Figures

Figure 1

21 pages, 4383 KB

Open AccessReview

The Advent of MXene-Based Synthetics and Modification Approaches for Advanced Applications in Wastewater Treatment

by Isha Soni, Monika Ahuja, Pratik Kumar Jagtap, Vinay Chauhan, Savan K. Raj and Prem P. Sharma

Membranes 2025, 15(12), 364; https://doi.org/10.3390/membranes15120364 - 30 Nov 2025

Viewed by 598

Abstract

MXenes, members of two-dimensional materials, were discovered in 2011 for the first time. MXenes are famous nowadays for their attractive and unique properties such as hydrophilicity, surface area, and catalytic activity for various industrial applications. This review comprehensively focused on composite membranes with [...] Read more.

MXenes, members of two-dimensional materials, were discovered in 2011 for the first time. MXenes are famous nowadays for their attractive and unique properties such as hydrophilicity, surface area, and catalytic activity for various industrial applications. This review comprehensively focused on composite membranes with MXenes that can be directly deployed for water purification. Moreover, this review will also give significant insight into new synthetic approaches for MXene-based composite membranes. A review of the utilization of MXene-based composite membranes in modern separation techniques such as nanofiltration, ultrafiltration, and forward osmosis has also been summarized. Finally, the current issues and future perspectives on applying two-dimensional materials for water treatment are elaborately discussed. Full article

(This article belongs to the Special Issue Sustainable Advances in Oil & Gas, Mining, and Environmental Technologies: Innovations in Membrane and Porous Material Technologies)

► Show Figures

Figure 1

12 pages, 1873 KB

Open AccessArticle

Effects of Surface Modification on the Electrodialysis Performance of Anion-Exchange Membranes

by Zhijuan Zhao, Qiang Dai, Shichun Feng and Jianhua Yang

Membranes 2025, 15(12), 363; https://doi.org/10.3390/membranes15120363 - 30 Nov 2025

Viewed by 392

Abstract

A commercial anion-exchange membrane was modified via the electrodeposition of different water-soluble polymers to study the effects of surface modification on electrodialysis performance. X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy analyses showed that the different polymers were successfully electrodeposited [...] Read more.

A commercial anion-exchange membrane was modified via the electrodeposition of different water-soluble polymers to study the effects of surface modification on electrodialysis performance. X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy analyses showed that the different polymers were successfully electrodeposited on the membrane surface. The surface morphology and electrical resistance of the modified AEMs were almost unchanged. Contact angle and zeta potential measurements indicated differences in the surface hydrophilicity and surface charge density of the modified AEMs. The electrodialysis performance of the pristine AEM declined significantly in the presence of the foulant. In contrast, the electrodialysis performance of the AEMs modified with poly (vinylsulfonic acid, sodium salt) showed almost no decline and exhibited the best antifouling property in the presence of the foulant, followed by those modified with poly (sodium acrylate) and poly (vinyl alcohol). The results indicated that an increase in surface negative charge density and surface hydrophilicity increased the resistance of the modified AEMs to the foulant and improved their electrodialysis performance. Full article

► Show Figures

Figure 1

17 pages, 4225 KB

Open AccessArticle

Bead-Like Pt/C-Ionomer Porous Nanofibrous Networks Toward Advanced Electrochemical Reaction Management for Direct Methanol Fuel Cells

by Ruili Sun, Dongming Zhu, Nan Wu, Yi Li, Ting Chen and Shaorong Wang

Membranes 2025, 15(12), 362; https://doi.org/10.3390/membranes15120362 - 29 Nov 2025

Viewed by 437

Abstract

Efficient management for electrochemical reactions within Pt/C electrodes, specifically the oxygen reduction reaction (ORR) and methanol oxidation reactions (MOR), is critical to the performance and long-life stability of direct methanol fuel cells (DMFCs). Optimizing the hierarchical macro/mesoscale structures of Pt/C electrodes plays a [...] Read more.

Efficient management for electrochemical reactions within Pt/C electrodes, specifically the oxygen reduction reaction (ORR) and methanol oxidation reactions (MOR), is critical to the performance and long-life stability of direct methanol fuel cells (DMFCs). Optimizing the hierarchical macro/mesoscale structures of Pt/C electrodes plays a decisive role in regulating the mass transport pathways and electrochemical reactions. In this work, bead-like Pt/C-ionomer hybrid porous nanofibrous networks are constructed via electrospinning. Ascribing to the hierarchical architecture consisting of continuous nanofibers and bead-like Pt/C-ionomer fibrous networks, the hybrid porous nanofibrous electrode exhibits a 55% increase in maximum mass power density in comparison to the conventional Pt/C electrode. Such enhancement is attributed to excellent ORR activity enabled by efficient triple-phase reaction regions, coupled with superior MOR tolerance resulting from restricted methanol transport from the hybrid porous nanofibrous electrode to triple-phase reaction regions. Full article

► Show Figures

Graphical abstract

18 pages, 4953 KB

Open AccessReview

Research Progress on the Application of Biomass Fibers in Lithium-Ion Battery Separators

by Chi Chen, Boqiao Li and Chong Zhao

Membranes 2025, 15(12), 361; https://doi.org/10.3390/membranes15120361 - 28 Nov 2025

Viewed by 574

Abstract

The separator is a key component of lithium-ion batteries, and its properties play a crucial role in the performance of such batteries. However, the most widely used polyolefin separators are not only made from non-renewable resources such as petroleum, but also have poor [...] Read more.

The separator is a key component of lithium-ion batteries, and its properties play a crucial role in the performance of such batteries. However, the most widely used polyolefin separators are not only made from non-renewable resources such as petroleum, but also have poor wettability to electrolytes, and their low melting points may cause short circuits or even explosions. Therefore, advanced separators that meet the increasing requirements of such batteries are urgently needed. Compared to polyolefin separators, renewable biomass fiber-based separators have better compatibility with electrolytes, higher thermal stability, and are naturally abundant. Their use is not only in line with sustainable development, but it also lowers their material cost. Therefore, biomass fiber-based separators are considered a promising candidate for replacing polyolefin separators for lithium-ion batteries in the future. In this article, studies on the preparation and application of biomass fiber-based separators in lithium-ion batteries in recent years are reviewed, looking forward to their future development, with the aim of providing a reference for researchers. Full article

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

► Show Figures

Figure 1

19 pages, 4493 KB

Open AccessArticle

Effect of VTMS-Modified TiO₂ Nanoparticles on CO₂ Separation Performance of Polysulfone-Based Mixed Matrix Membranes

by Mustafa Alsaady, Muhammad Faisal Usman, Hafiz Abdul Mannan, Mohamed Amine Ben Ali, Aymn Abdulrahman, Anas Ahmed and Suhaib Umer Ilyas

Membranes 2025, 15(12), 360; https://doi.org/10.3390/membranes15120360 - 28 Nov 2025

Viewed by 448

Abstract

Polysulfone (PSF), despite its excellent thermal and mechanical stability, exhibits moderate gas separation performance and poor compatibility with inorganic fillers, resulting in interfacial voids and structural defects. This study addressed these limitations by incorporating vinyltrimethoxysilane (VTMS)-functionalized TiO₂ nanoparticles into PSF matrix to [...] Read more.

Polysulfone (PSF), despite its excellent thermal and mechanical stability, exhibits moderate gas separation performance and poor compatibility with inorganic fillers, resulting in interfacial voids and structural defects. This study addressed these limitations by incorporating vinyltrimethoxysilane (VTMS)-functionalized TiO₂ nanoparticles into PSF matrix to develop mixed matrix membranes (MMMs) for selective CO₂/N₂ separation. Membranes with 1–5 wt.% VTMS@TiO₂ loadings were fabricated via solution casting, and their gas separation performance was systematically evaluated. VTMS modification enhanced the dispersion and interfacial adhesion of TiO₂ within the PSF matrix, as confirmed by SEM, FTIR, XRD, and TGA analyses. The 4 wt.% VTMS@TiO₂ loaded membrane showed optimal performance, with a CO₂ permeability of 8.48 barrer and a CO₂/N₂ selectivity of 26.50 due to stronger polymer–filler interactions and enhanced CO₂ affinity by VTMS functional groups. This membrane has shown stable transport behavior and favorable CO₂ selectivity as confirmed by pressure- and temperature-dependent permeation studies. Robeson plot analysis showed that the optimized membrane approached the upper bound, demonstrating a significant improvement over pure PSF. The study confirmed that VTMS-functionalized TiO₂ enhanced both permeability and selectivity through improved filler dispersion, interfacial integrity, and CO₂ affinity. Full article

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

► Show Figures

Figure 1

15 pages, 5082 KB

Open AccessArticle

Optimized Ultrafiltration Membrane Based on Acrylic Fiber Waste for Organic Compounds Removal from Wastewater

by Ahmed A. Bhran, Eman S. Mansor, Heba Abdallah and Abdelrahman G. Gadallah

Membranes 2025, 15(12), 359; https://doi.org/10.3390/membranes15120359 - 28 Nov 2025

Viewed by 481

Abstract

This study reports the development of an optimized tight ultrafiltration (UF) membrane prepared from recycled acrylic fiber (polyacrylonitrile, PAN) waste for the efficient removal of organic pollutants from water. Membranes were fabricated using different concentrations of acrylic fiber waste to examine the influence [...] Read more.

This study reports the development of an optimized tight ultrafiltration (UF) membrane prepared from recycled acrylic fiber (polyacrylonitrile, PAN) waste for the efficient removal of organic pollutants from water. Membranes were fabricated using different concentrations of acrylic fiber waste to examine the influence of polymer content on their morphology and performance. The prepared membranes were characterized using scanning electron microscopy (SEM), porosity measurements, contact angle analysis, and mechanical strength testing to evaluate their structural and physicochemical properties. Among the tested formulations, membrane M4, containing 22.5 wt.% acrylic fiber waste, shows the most balanced performance, high mechanical integrity, and good surface hydrophilicity, with a contact angle of about 52° and porosity of 27%. The optimized M4 membrane demonstrates excellent pure water flux of 65 LMH. M4 achieves a flux recovery ratio (FRR) above 80%. Its performance was further evaluated for the removal of humic acid (HA) and paracetamol as a model of organic contaminants. The results also demonstrate strong chemical stability under acidic and basic conditions, highlighting the potential of recycled acrylic fiber waste as a sustainable polymer source for high-performance tight UF membranes. This approach offers an environmentally friendly and cost-effective solution for water purification and pharmaceutical contaminant removal. Full article

(This article belongs to the Special Issue Advances in Porous Membrane and Its Applications)

► Show Figures

Figure 1

20 pages, 2980 KB

Open AccessArticle

Pharmaceuticals, Pesticides, and Poly- and Perfluoroalkyl Substances at Surface Water Occurrence Levels—Impact of Compound Specific Physicochemical Properties on Nanofiltration and Reverse Osmosis Processes

by Jelena Šurlan, Claudia F. Galinha, Nikola Maravić, Carla Brazinha, Igor Antić, Jelena Živančev, Nataša Đurišić-Mladenović, Zita Šereš and João G. Crespo

Membranes 2025, 15(12), 358; https://doi.org/10.3390/membranes15120358 - 27 Nov 2025

Cited by 1 | Viewed by 767

Abstract

Pharmaceutically active compounds (PhACs), pesticides, and poly- and perfluoroalkyl substances (PFAS) are increasingly detected in surface waters at trace concentrations, raising concerns for both aquatic systems and, consequently, human health. Conventional solutions are insufficient to achieve complete removal at trace compound concentrations, highlighting [...] Read more.

Pharmaceutically active compounds (PhACs), pesticides, and poly- and perfluoroalkyl substances (PFAS) are increasingly detected in surface waters at trace concentrations, raising concerns for both aquatic systems and, consequently, human health. Conventional solutions are insufficient to achieve complete removal at trace compound concentrations, highlighting the need for advanced separation technologies. This study aims to comprehensively analyze rejection and removal mechanisms of selected PhACs, pesticides, and PFAS present in water solutions at reported environmentally relevant concentrations (300 ng L⁻¹), using two nanofiltration (NF) and one reverse osmosis (RO) polyamide membrane. PhACs, pesticides, and PFAS were selected to cover a broad range of physicochemical properties, specifically molecular mass (MM), dissociation constant (pKa), and octanol–water partition coefficient (logK_o/w). Rejection values ranged from 42.1% (acetaminophen) to apparent 100% (for multiple compounds), depending on water pH, solute properties, and membrane characteristics. Size exclusion and electrostatic interactions were identified as the primary removal mechanisms, with hydrophobic interactions having a lower impact, particularly for carbamazepine, bezafibrate, and perfluorooctane sulfonic acid (PFOS). Addition of sodium chloride (3 g L⁻¹) decreased rejection of most negatively charged compounds due to suppression of membrane surface charge, although clarithromycin and ofloxacin exhibited improved rejection. Presented results provide fundamental insight into compound-specific membrane rejection and highlight the importance of membrane–solute interactions under environmentally realistic conditions. The results support further optimization of NF and RO for targeted compound rejection and provide a baseline for data-driven membrane process modeling. Full article

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

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Membranes, Volume 15, Issue 12 (December 2025) – 42 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI