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Membranes
Volume 15
Issue 7
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Membranes, Volume 15, Issue 7 (July 2025) – 31 articles

Cover Story (view full-size image): Bio-sourced membranes are gaining recognition as environmentally friendly alternatives to petroleum-based options for wastewater treatment and food packaging. Polylactic acid (PLA) and poly(3-hydroxybutyrate) (PHB) are two biodegradable polymers derived from lignocellulosic waste. They possess suitable characteristics such as thermal resistance and mechanical strength, which make them potential candidates for replacing conventional plastics. This study highlights recent advancements in PLA and PHB, with a focus on their extraction from lignocellulosic biomass, their production, and their integration into membrane manufacturing. It also reviews their benefits and limitations, and explores future possibilities in water treatment, gas and oil–water separation, medical applications, drug-release control, and food packaging. View this paper
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14 pages, 6077 KB  
Article
Fabrication of Green PVDF/TiO2 Composite Membrane for Water Treatment
by Shuhang Lu and Dong Zou
Membranes 2025, 15(7), 218; https://doi.org/10.3390/membranes15070218 - 21 Jul 2025
Viewed by 671
Abstract
PVDF/TiO2 composite membranes show some potential to be used for water treatment as they combine the advantages of polymers and ceramics. However, conventional PVDF-based composite membranes are always fabricated by using conventional toxic solvents. Herein, PolarClean was used as a green solvent [...] Read more.
PVDF/TiO2 composite membranes show some potential to be used for water treatment as they combine the advantages of polymers and ceramics. However, conventional PVDF-based composite membranes are always fabricated by using conventional toxic solvents. Herein, PolarClean was used as a green solvent to fabricate PVDF/TiO2 composite membranes via the phase inversion method. In this process, Pluronic F127 was used as a dispersion agent to distribute TiO2 particles in the PVDF matrix and to serve as a pore former on the membrane surface. TiO2 particles were well distributed on the membrane surface and bulk. TiO2 particles in the PVDF matrix enhanced the mechanical strength and hydrophilic characteristics of the resulting composite membrane, facilitating water transport through the composite membranes and enhancing their water permeability. Membrane microstructures and mechanical strength of the composite membranes were finely tuned by varying the PVDF concentration, TiO2 concentration, and coagulation bath temperature. It was demonstrated that the resulting green PVDF/TiO2 composite membrane showed a high water permeance compared with those using conventional toxic solvents in terms of its small pore size. In addition, the particle rejection of green PVDF/TiO2 membrane showed a 99.9% rejection rate in all the filtration process, while those using NMP showed 91.1% after 30 min of filtration. The water flux was similar at 121 and 130 Lm−2h−1 for green and conventional solvents, respectively. This work provides important information for the future application of sustainable membranes. Full article
(This article belongs to the Special Issue New Trends in Membrane Technologies for Removal of Hazardous Pollutants)
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14 pages, 405 KB  
Review
A Mini Review of Reused End-of-Life Reverse Osmosis (EoL RO) Membranes
by Anissa Somrani, Kholoud Abohelal and Maxime Pontié
Membranes 2025, 15(7), 217; https://doi.org/10.3390/membranes15070217 - 21 Jul 2025
Viewed by 882
Abstract
As sensitive parts of the water treatment process, reverse osmosis (RO) membranes are the most important for desalination and wastewater treatment. But the performance of RO membranes deteriorates over time due to fouling, necessitating frequent replacements. One of the environmental challenges is the [...] Read more.
As sensitive parts of the water treatment process, reverse osmosis (RO) membranes are the most important for desalination and wastewater treatment. But the performance of RO membranes deteriorates over time due to fouling, necessitating frequent replacements. One of the environmental challenges is the disposal of End-of-Life (EoL) RO membranes, which are made of non-biodegradable polymers. The reuse of EoL membranes as a sustainable approach for waste saving and resource efficiency has recently attracted considerable attention. The present work provides a comprehensive overview of the strategies for reusing EoL RO membranes as sustainable alternatives to conventional disposal methods. Furthermore, the fundamental principles of RO technology, the primary types and impacts of membrane fouling, and advanced cleaning and regeneration techniques are discussed. The conversion of EoL membranes into nanofiltration (NF), ultrafiltration (UF), and forward osmosis (FO) membranes is also covered in this review, as well as their uses in brackish water desalination, dye/salt separation, groundwater treatment, and household wastewater reuse. Environmental and economic benefits, as well as technical, social, and regulatory challenges, are also discussed. Finally, the review highlights innovative approaches and future directions for incorporating EoL membrane reuse into circular economy models, outlining its potential to improve sustainability and reduce operational costs in water treatment systems. Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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14 pages, 3055 KB  
Article
High-Performance Thin Film Composite Nanofiltration (NF) Membrane Constructed on Modified Polyvinylidene Fluoride (PVDF) Substrate
by Junliang Dong, Qianzhi Sun, Xiaolin Feng and Ruijun Zhang
Membranes 2025, 15(7), 216; https://doi.org/10.3390/membranes15070216 - 20 Jul 2025
Viewed by 532
Abstract
The inherent hydrophobic nature of PVDF material renders it challenging to establish a stable aqueous hydration layer, thereby limiting its suitability as a substrate for the preparation of nanofiltration (NF) membranes. In this study, we developed a novel modification approach that effectively enhances [...] Read more.
The inherent hydrophobic nature of PVDF material renders it challenging to establish a stable aqueous hydration layer, thereby limiting its suitability as a substrate for the preparation of nanofiltration (NF) membranes. In this study, we developed a novel modification approach that effectively enhances the hydrophilicity of PVDF substrates through the incorporation of sulfonic acid-doped polyaniline (SPANI) and hyperbranched polyester (HPE) into the PVDF casting solution, followed by cross-linking with trimesoyl chloride (TMC). The introduction of SPANI and HPE, which contain reactive polar amino and hydroxyl groups, improved the hydrophilicity of the substrate, while the subsequent cross-linking with TMC effectively anchored these components within the substrate through the covalent linking between TMC and the reactive sites. Additionally, the hydrolysis of TMC yielded non-reactive carboxyl groups, which further enhanced the hydrophilicity of the substrate. As a result, the modified PVDF substrate exhibited improved hydrophilicity, facilitating the construction of an intact polyamide layer. In addition, the fabricated TFC NF membrane demonstrated excellent performance in the advanced treatment of tap water, achieving a total dissolved solid removal rate of 57.9% and a total organic carbon removal rate of 85.3%. This work provides a facile and effective route to modify PVDF substrates for NF membrane fabrication. 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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18 pages, 3346 KB  
Article
Influence of Membrane Salt Rejection Properties on Cake-Enhanced Concentration Polarization Effects During Colloidal Fouling of Nanofiltration Membranes
by Oranso Themba Mahlangu and Bhekie Brilliance Mamba
Membranes 2025, 15(7), 215; https://doi.org/10.3390/membranes15070215 - 19 Jul 2025
Viewed by 631
Abstract
The build-up of a fouling layer on the membrane surface is believed to deteriorate flux and salt rejection by hindering back-diffusion of rejected salts, a phenomenon called cake-enhanced concentration polarization (CECP). Nevertheless, CECP effects have not been linked to the salt rejection properties [...] Read more.
The build-up of a fouling layer on the membrane surface is believed to deteriorate flux and salt rejection by hindering back-diffusion of rejected salts, a phenomenon called cake-enhanced concentration polarization (CECP). Nevertheless, CECP effects have not been linked to the salt rejection properties of the membrane. Furthermore, the decline in salt rejection during fouling has not been related to the decreasing flux, to elucidate the effects of flux on solution rejection as described by the solution-diffusion (SD) model. Therefore, this work examined whether CECP is substantial in membranes with poor salt-rejection properties. Fouling was performed using sodium alginate, Al2O3, latex, and SiO2. The effects of fouling on salt rejection were studied using two nanofiltration (NF) membranes, namely NF270 membrane (46% NaCl rejection) and NF90 membrane (>97% NaCl rejection). The measured flux and salt rejection profiles were compared to those predicted by the CECP and SD models. Overall, the flux declined more (30–60%) for the NF90 membrane (contact angle: 50 ± 3°) compared to the NF270 membrane (10–55%, contact angle: 39 ± 2°) under similar hydrodynamic conditions. Moreover, fouling had more effects on NaCl rejection for the NF90 membrane (2–45% decline) compared to the NF270 membrane (10–30% decline). The decrease in NaCl rejection for the NF90 membrane was ascribed to CECP effects and declining flux. Contrary, CECP effects were less important for the NF270 membrane, and rejection declined due to reduction in flux as predicted by the SD model, indicating that CECP may not be predominant in membranes that poorly reject salts. 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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20 pages, 3162 KB  
Article
Study on Separation of Desulfurization Wastewater in Ship Exhaust Gas Cleaning System with Rotating Dynamic Filtration
by Shiyong Wang, Juan Wu, Yanlin Wu and Wenbo Dong
Membranes 2025, 15(7), 214; https://doi.org/10.3390/membranes15070214 - 18 Jul 2025
Viewed by 481
Abstract
Current treatment methods for desulfurization wastewater in the ship exhaust gas cleaning (EGC) system face several problems, including process complexity, unstable performance, large spatial requirements, and high energy consumption. This study investigates rotating dynamic filtration (RDF) as an efficient treatment approach through experimental [...] Read more.
Current treatment methods for desulfurization wastewater in the ship exhaust gas cleaning (EGC) system face several problems, including process complexity, unstable performance, large spatial requirements, and high energy consumption. This study investigates rotating dynamic filtration (RDF) as an efficient treatment approach through experimental testing, theoretical analysis, and pilot-scale validation. Flux increases with temperature and pressure but decreases with feed concentration, remaining unaffected by circulation flow. For a small membrane (152 mm), flux consistently increases with rotational speed across all pressures. For a large membrane (374 mm), flux increases with rotational speed at 300 kPa but firstly increases and then decreases at 100 kPa. Filtrate turbidity in all experiments complies with regulatory standards. Due to the unique hydrodynamic characteristics of RDF, back pressure reduces the effective transmembrane pressure, whereas shear force mitigates concentration polarization and cake layer formation. Separation performance is governed by the balance between these two forces. The specific energy consumption of RDF is only 10–30% that of cross-flow filtration (CFF). Under optimized pilot-scale conditions, the wastewater was concentrated 30-fold, with filtrate turbidity consistently below 2 NTU, outperforming CFF. Moreover, continuous operation proves more suitable for marine environments. Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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15 pages, 1745 KB  
Article
A Study on the Performance of Vacuum Membrane Distillation in Treating Acidic, Simulated, Low-Level Radioactive Liquid Waste
by Sifan Chen, Yan Xu, Yuyong Wu, Yizhou Lu, Zhan Weng, Yaoguang Tao, Jianghai Liu and Baihua Jiang
Membranes 2025, 15(7), 213; https://doi.org/10.3390/membranes15070213 - 18 Jul 2025
Viewed by 507
Abstract
This study systematically explored the performance of a vacuum membrane distillation (VMD) system equipped with polytetrafluoroethylene (PTFE) hollow fiber membranes for treating simulated, acidic, low-level radioactive liquid waste. By focusing on key operational parameters, including feed temperature, vacuum pressure, and flow velocity, an [...] Read more.
This study systematically explored the performance of a vacuum membrane distillation (VMD) system equipped with polytetrafluoroethylene (PTFE) hollow fiber membranes for treating simulated, acidic, low-level radioactive liquid waste. By focusing on key operational parameters, including feed temperature, vacuum pressure, and flow velocity, an orthogonal experiment was designed to obtain the optimal parameters. Considering the potential application scenarios, the following two factors were also studied: the initial nuclide concentrations (0.5, 5, and 50 mg·L−1) and tributyl phosphate (TBP) concentrations (0, 20, and 100 mg·L−1) in the feed solution. The results indicated that the optimal operational parameters for VMD were as follows: a feed temperature of 70 °C, a vacuum pressure of 90 kPa, and a flow rate of 500 L·h−1. Under these parameters, the VMD system demonstrated a maximum permeate flux of 0.9 L·m−2·h−1, achieving a nuclide rejection rate exceeding 99.9%, as well as a nitric acid rejection rate of 99.4%. A significant negative correlation was observed between permeate flux and nuclide concentrations at levels above 50 mg·L−1. The presence of TBP in the feed solution produced membrane fouling, leading to flux decline and a reduced separation efficiency, with severity increasing with TBP concentration. The VMD process simultaneously achieved nuclide rejection and nitric acid concentration in acidic radioactive wastewater, demonstrating strong potential for nuclear wastewater treatment. Full article
(This article belongs to the Topic Removing Challenging Pollutants from Wastewater: Effective Approaches)
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18 pages, 1422 KB  
Article
Potable Water Recovery for Space Habitation Systems Using Hybrid Life Support Systems: Biological Pretreatment Coupled with Reverse Osmosis for Humidity Condensate Recovery
by Sunday Adu, William Shane Walker and William Andrew Jackson
Membranes 2025, 15(7), 212; https://doi.org/10.3390/membranes15070212 - 16 Jul 2025
Viewed by 760
Abstract
The development of efficient and sustainable water recycling systems is essential for long-term human missions and the establishment of space habitats on the Moon, Mars, and beyond. Humidity condensate (HC) is a low-strength wastewater that is currently recycled on the International Space Station [...] Read more.
The development of efficient and sustainable water recycling systems is essential for long-term human missions and the establishment of space habitats on the Moon, Mars, and beyond. Humidity condensate (HC) is a low-strength wastewater that is currently recycled on the International Space Station (ISS). The main contaminants in HC are primarily low-molecular-weight organics and ammonia. This has caused operational issues due to microbial growth in the Water Process Assembly (WPA) storage tank as well as failure of downstream systems. In addition, treatment of this wastewater primarily uses adsorptive and exchange media, which must be continually resupplied and represent a significant life-cycle cost. This study demonstrates the integration of a membrane-aerated biological reactor (MABR) for pretreatment and storage of HC, followed by brackish water reverse osmosis (BWRO). Two system configurations were tested: (1) periodic MABR fluid was sent to batch RO operating at 90% water recovery with the RO concentrate sent to a separate waste tank; and (2) periodic MABR fluid was sent to batch RO operating at 90% recovery with the RO concentrate returned to the MABR (accumulating salinity in the MABR). With an external recycle tank (configuration 2), the system produced 2160 L (i.e., 1080 crew-days) of near potable water (dissolved organic carbon (DOC) < 10 mg/L, total nitrogen (TN) < 12 mg/L, total dissolved solids (TDS) < 30 mg/L) with a single membrane (weight of 260 g). When the MABR was used as the RO recycle tank (configuration 1), 1100 L of permeate could be produced on a single membrane; RO permeate quality was slightly better but generally similar to the first configuration even though no brine was wasted during the run. The results suggest that this hybrid system has the potential to significantly enhance the self-sufficiency of space habitats, supporting sustainable extraterrestrial human habitation, as well as reducing current operational problems on the ISS. These systems may also apply to extreme locations such as remote/isolated terrestrial locations, especially in arid and semi-arid regions. Full article
(This article belongs to the Special Issue Advanced Membranes and Membrane Technologies for Wastewater Treatment)
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21 pages, 4609 KB  
Review
Covalent Organic Framework Membranes for Ion Separation: A Review
by Yutong Lou, Zhanyong Wang, Wanbei Yang, Shuchen Lang, Jiaxing Fan, Qiaomei Ke, Rui Wang, Zhen Zhang, Wentao Chen and Jian Xue
Membranes 2025, 15(7), 211; https://doi.org/10.3390/membranes15070211 - 15 Jul 2025
Viewed by 1051
Abstract
Covalent organic framework (COF) membranes have garnered significant attention in ion separation due to their high surface area, tunable pore size, excellent stability, and diverse functional groups. Over the past decade, various synthesis methods, such as solvothermal synthesis, interfacial synthesis, microwave-assisted solvothermal synthesis, [...] Read more.
Covalent organic framework (COF) membranes have garnered significant attention in ion separation due to their high surface area, tunable pore size, excellent stability, and diverse functional groups. Over the past decade, various synthesis methods, such as solvothermal synthesis, interfacial synthesis, microwave-assisted solvothermal synthesis, and in situ growth, have been developed to fabricate COF membranes. COF membranes have demonstrated remarkable ion separation performance in different separation processes driven by pressure, electric field, and vapor pressure difference, showing great potential in a wide range of applications. Nevertheless, challenges in the synthesis and application of COF membranes still remain, requiring further research to fully realize their potential in ion separation. This review critically examines the development of COF membranes, from synthesis methods to ion separation applications. We evaluate the advantages and limitations of various synthesis techniques and systematically summarize COF membrane performance based on separation driving forces. Finally, we present a critical analysis of current challenges and offer perspectives on promising future research directions for advancing COF membrane technology in separation. Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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31 pages, 1834 KB  
Review
A Review of Polylactic Acid (PLA) and Poly(3-hydroxybutyrate) (PHB) as Bio-Sourced Polymers for Membrane Production Applications
by Lacrimioara Senila, Eniko Kovacs and Marin Senila
Membranes 2025, 15(7), 210; https://doi.org/10.3390/membranes15070210 - 14 Jul 2025
Viewed by 1372
Abstract
In recent years, membranes have found extensive applications, primarily in wastewater purification and food packaging. However, petroleum-based membranes can be detrimental to the environment. For this reason, extensive studies are being conducted to identify environmentally friendly substitutes for the materials used in membrane [...] Read more.
In recent years, membranes have found extensive applications, primarily in wastewater purification and food packaging. However, petroleum-based membranes can be detrimental to the environment. For this reason, extensive studies are being conducted to identify environmentally friendly substitutes for the materials used in membrane composition. Among these materials, polylactic acid (PLA) and poly(3-hydroxybutyrate) (PHB) are two bio-sourced and biodegradable polymers that can be derived from lignocellulosic waste. These polymers also possess suitable characteristics, such as thermal resistance and mechanical strength, which make them potential candidates for replacing conventional plastics. This study provides an overview of recent advances in the production of PLA and PHB, with a focus on their extraction from lignocellulosic biomass, as well as the recent applications of these two biodegradable polymers as sustainable materials in membrane manufacturing. The advantages and limitations of membranes produced from these materials are also summarized. Lastly, an analysis of future trends is provided concerning new sources, production possibilities, and potential applications in water treatment (mainly for metal ions separation), gas separation, oil–water separation, medical applications, drug release control, and food packaging. Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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26 pages, 38900 KB  
Article
A Set of Fluorescent Protein-Based Markers for Major Vesicle Coat Proteins in Yeast
by Xue-Fei Cui, Zheng-Tan Zhang, Jing Zhu, Li Cui and Zhiping Xie
Membranes 2025, 15(7), 209; https://doi.org/10.3390/membranes15070209 - 13 Jul 2025
Viewed by 576
Abstract
In eukaryotic cells, vesicle-mediated transport interconnects the endomembrane system. These vesicles are formed by coat proteins via deformation of donor membranes. Here, we constructed a set of fluorescent protein-based markers for major coat protein complexes in the yeast model system, and examined their [...] Read more.
In eukaryotic cells, vesicle-mediated transport interconnects the endomembrane system. These vesicles are formed by coat proteins via deformation of donor membranes. Here, we constructed a set of fluorescent protein-based markers for major coat protein complexes in the yeast model system, and examined their subcellular localization patterns. Our markers covered COPII, COPI, AP-1, AP-2, AP-3, and retromer complexes. Our live cell imaging demonstrates that COPII puncta were primarily associated with the endoplasmic reticulum (ER), and occasionally with early Golgi. COPI was present on both early Golgi and late Golgi/early endosomes. AP-1 puncta were present on late Golgi/early endosomes. AP-2 was present on plasma membrane (PM)-associated puncta, and around the bud neck. AP-3 puncta were present on late Golgi/early endosomes and on the surface of vacuoles. Retromer was present on the surface of vacuoles, late endosomes, and other perivacuolar puncta. Notably, more than half of AP-1 puncta and AP-3 puncta were not associated with the donor compartments where they are thought to be generated, implying that these were coated transport vesicles. This work provides a convenient tool set for the investigation of vesicular transport in yeast and live cell imaging evidence for the presence of certain coated transport vesicles. Full article
(This article belongs to the Section Biological Membranes)
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15 pages, 1466 KB  
Article
Effect of Tau Fragment and Membrane Interactions on Membrane Permeabilization and Peptide Aggregation
by Majedul Islam, Md Raza Ul Karim, Emily Argueta, Mohammed N. Selim, Ewa P. Wojcikiewicz and Deguo Du
Membranes 2025, 15(7), 208; https://doi.org/10.3390/membranes15070208 - 13 Jul 2025
Viewed by 1321
Abstract
Aggregation of tau protein is a hallmark feature of tauopathies such as Alzheimer’s disease. The microtubule-binding domain of tau plays a crucial role in the tau aggregation process. In this study, we investigated the dual effects of membrane interactions of tau298–317, [...] Read more.
Aggregation of tau protein is a hallmark feature of tauopathies such as Alzheimer’s disease. The microtubule-binding domain of tau plays a crucial role in the tau aggregation process. In this study, we investigated the dual effects of membrane interactions of tau298–317, a fragment peptide from the microtubule-binding domain, on peptide-induced membrane disruption and membrane-mediated peptide self-assembly. Our results show that neither wild-type tau298–317 nor its P301L or Ser305-phosphorylated mutants aggregate in the presence of zwitterionic POPC vesicles or cause lipid vesicle leakage, indicating weak peptide–membrane interactions. In contrast, tau298–317 strongly interacts with negatively charged POPG liposomes, leading to a rapid transition of the peptide conformation from random coils to α-helical intermediate conformation upon membrane adsorption, which may further promote peptide self-association to form oligomers and β-sheet-rich fibrillar structures. Tau298–317-induced rapid POPG membrane leakage indicates a synergistic process of the peptide self-assembly at the membrane interface and the aggregation-induced membrane disruption. Notably, phosphorylation at Ser305 disrupts favorable electrostatic interactions between the peptide and POPG membrane surface, thus preventing peptide aggregation and membrane leakage. In contrast, the P301L mutation significantly enhances membrane-mediated peptide aggregation and peptide-induced membrane disruption, likely due to alleviation of local conformational constraints and enhancement of local hydrophobicity, which facilitates fast conformational conversion to β-sheet structures. These findings provide mechanistic insights into the molecular mechanisms underlying membrane-mediated aggregation of crucial regions of tau and peptide-induced membrane damage, indicating potential strategies to prevent tau aggregation and membrane rupture by targeting critical electrostatic interactions between membranes and key local regions of tau. Full article
(This article belongs to the Section Biological Membranes)
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20 pages, 8459 KB  
Article
Membrane Processes for Remediating Water from Sugar Production By-Product Stream
by Amal El Gohary Ahmed, Christian Jordan, Eva Walcher, Selma Kuloglija, Reinhard Turetschek, Antonie Lozar, Daniela Tomasetig and Michael Harasek
Membranes 2025, 15(7), 207; https://doi.org/10.3390/membranes15070207 - 12 Jul 2025
Viewed by 720
Abstract
Sugar production generates wastewater rich in dissolved solids and organic matter, and improper disposal poses severe environmental risks, exacerbates water scarcity, and creates regulatory challenges. Conventional treatment methods, such as evaporation and chemical precipitation, are energy-intensive and often ineffective at removing fine particulates [...] Read more.
Sugar production generates wastewater rich in dissolved solids and organic matter, and improper disposal poses severe environmental risks, exacerbates water scarcity, and creates regulatory challenges. Conventional treatment methods, such as evaporation and chemical precipitation, are energy-intensive and often ineffective at removing fine particulates and dissolved impurities. This study evaluates membrane-based separation as a sustainable alternative for water reclamation and sugar recovery from sugar industry effluents, focusing on replacing evaporation with membrane processes, ensuring high permeate quality, and mitigating membrane fouling. Cross-flow filtration experiments were conducted on a lab-scale membrane system at 70 °C to suppress microbial growth, comparing direct reverse osmosis (RO) of the raw effluent to an integrated ultrafiltration (UF)–RO process. Direct RO resulted in rapid membrane fouling. A tight UF (5 kDa) pre-treatment before RO significantly mitigated fouling and improved performance, enabling 28% water recovery and 79% sugar recovery, maintaining permeate conductivity below 0.5 mS/cm, sustaining stable flux, and reducing membrane blocking. Additionally, the UF and RO membranes were tested via SEM, EDS, and FTIR to elucidate the fouling mechanisms. Full article
(This article belongs to the Special Issue Emerging Superwetting Membranes: New Advances in Water Treatment)
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8 pages, 4309 KB  
Communication
A Conceptual Approach to Reduce the Product Gas Crossover in Alkaline Electrolyzers
by Diogo Loureiro Martinho and Torsten Berning
Membranes 2025, 15(7), 206; https://doi.org/10.3390/membranes15070206 - 12 Jul 2025
Viewed by 703
Abstract
The crossover of the product gases hydrogen and oxygen in alkaline electrolyzer operation is a critical factor, severely limiting the operational window in terms of current density and pressure. In prior experiments, it was found that a large degree of oversaturation of the [...] Read more.
The crossover of the product gases hydrogen and oxygen in alkaline electrolyzer operation is a critical factor, severely limiting the operational window in terms of current density and pressure. In prior experiments, it was found that a large degree of oversaturation of the reaction products in the liquid electrolyte phase leads to high amounts of crossover. We are proposing to reduce this amount of oversaturation by introducing micro-cracks in the Zirfon diaphragm. These cracks are meant to induce the formation of hydrogen and oxygen bubbles on the respective sides, and thereby reduce the oversaturation and amount of crossover. In theory, the size of the bubble corresponds to the size of the cracks, and from our computational fluid dynamics simulations, we conclude that the bubbles should be as large as possible to minimize the ohmic resistance in the electrolyte phase. The results suggest that an increase in bubble diameter from 50 microns to 150 microns results in a 10% higher current density at a cell voltage of 2.1 V. Full article
(This article belongs to the Section Membrane Applications for Energy)
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22 pages, 892 KB  
Review
Membrane Technologies for Bioengineering Microalgae: Sustainable Applications in Biomass Production, Carbon Capture, and Industrial Wastewater Valorization
by Michele Greque Morais, Gabriel Martins Rosa, Luiza Moraes, Larissa Chivanski Lopes and Jorge Alberto Vieira Costa
Membranes 2025, 15(7), 205; https://doi.org/10.3390/membranes15070205 - 11 Jul 2025
Viewed by 795
Abstract
In accordance with growing environmental pressures and the demand for sustainable industrial practices, membrane technologies have emerged as key enablers for increasing efficiency, reducing emissions, and supporting circular processes across multiple sectors. This review focuses on the integration among microalgae-based systems, offering innovative [...] Read more.
In accordance with growing environmental pressures and the demand for sustainable industrial practices, membrane technologies have emerged as key enablers for increasing efficiency, reducing emissions, and supporting circular processes across multiple sectors. This review focuses on the integration among microalgae-based systems, offering innovative and sustainable solutions for biomass production, carbon capture, and industrial wastewater treatment. In cultivation, membrane photobioreactors (MPBRs) have demonstrated biomass productivity up to nine times greater than that of conventional systems and significant reductions in water (above 75%) and energy (approximately 0.75 kWh/m3) footprints. For carbon capture, hollow fiber membranes and hybrid configurations increase CO2 transfer rates by up to 300%, achieving utilization efficiencies above 85%. Coupling membrane systems with industrial effluents has enabled nutrient removal efficiencies of up to 97% for nitrogen and 93% for phosphorus, contributing to environmental remediation and resource recovery. This review also highlights recent innovations, such as self-forming dynamic membranes, magnetically induced vibration systems, antifouling surface modifications, and advanced control strategies that optimize process performance and energy use. These advancements position membrane-based microalgae systems as promising platforms for carbon-neutral biorefineries and sustainable industrial operations, particularly in the oil and gas, mining, and environmental technology sectors, which are aligned with global climate goals and the UN Sustainable Development Goals (SDGs). 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)
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13 pages, 1936 KB  
Article
Amyloid β 1-42 Can Form Ion Channels as Small as Gramicidin in Model Lipid Membranes
by Yue Xu, Irina Bukhteeva, Yurii Potsiluienko and Zoya Leonenko
Membranes 2025, 15(7), 204; https://doi.org/10.3390/membranes15070204 - 8 Jul 2025
Viewed by 966
Abstract
The amyloid-beta 1-42 (Aβ1-42) oligomers are the most cytotoxic species of the amyloid family and play a key role in the pathology of Alzheimer’s Disease (AD). They have been shown to damage cellular membranes, but the exact mechanism is complex and not well [...] Read more.
The amyloid-beta 1-42 (Aβ1-42) oligomers are the most cytotoxic species of the amyloid family and play a key role in the pathology of Alzheimer’s Disease (AD). They have been shown to damage cellular membranes, but the exact mechanism is complex and not well understood. Multiple routes of membrane damage have been proposed, including the formation of pores and ion channels. In this work, we study the membrane damage induced by Aβ1-42 oligomers using black lipid membrane (BLM) electrophysiology and compare their action with gramicidin, known to form ion channels. Our data show that Aβ1-42 oligomers can induce a variety of damage in the lipid membranes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and cholesterol (CHOL), including small ion channels, similar to the gramicidin channels, with an average inner diameter smaller than 5 Å. These channels have a short retaining time in lipid membranes, suggesting that they are highly dynamic. Our studies provide new insights into the mechanism of membrane damage caused by Aβ1-42 oligomers and extend the current perception of the Aβ channelopathy hypothesis. It provides a more in-depth understanding of the molecular mechanism by which small Aβ oligomers induce cytotoxicity by interacting with lipid membranes in AD. Full article
(This article belongs to the Collection Feature Papers in Membranes in Life Sciences)
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26 pages, 10819 KB  
Review
Recent Advances in Thermochemical Water Splitting for Hydrogen Production Using Mixed Ionic-Electronic Conducting Membrane Reactors
by Jingjun Li, Qing Yang, Jie Liu, Qiangchao Sun and Hongwei Cheng
Membranes 2025, 15(7), 203; https://doi.org/10.3390/membranes15070203 - 4 Jul 2025
Viewed by 1175
Abstract
Under the accelerating global energy restructuring and the deepening carbon neutrality strategy, hydrogen energy has emerged with increasing strategic value as a zero-carbon secondary energy carrier. Water electrolysis technology based on renewable energy is regarded as an ideal pathway for large-scale green hydrogen [...] Read more.
Under the accelerating global energy restructuring and the deepening carbon neutrality strategy, hydrogen energy has emerged with increasing strategic value as a zero-carbon secondary energy carrier. Water electrolysis technology based on renewable energy is regarded as an ideal pathway for large-scale green hydrogen production. However, polymer electrolyte membrane (PEM) conventional water electrolysis faces dual constraints in economic feasibility and scalability due to its high electrical energy consumption and reliance on noble metal catalysts. The mixed ionic-electronic conducting oxygen transport membrane (MIEC–OTM) reactor technology offers an innovative solution to this energy efficiency-cost paradox due to its thermo-electrochemical synergistic energy conversion mechanism and process integration. This not only overcomes the thermodynamic equilibrium limitations in traditional electrolysis but also reduces electrical energy demand by effectively coupling with medium- to high-temperature heat sources such as industrial waste heat and solar thermal energy. Therefore, this review, grounded in the physicochemical mechanisms of oxygen transport membrane reactors, systematically examines the influence of key factors, including membrane material design, catalytic interface optimization, and parameter synergy, on hydrogen production efficiency. Furthermore, it proposes a roadmap and breakthrough directions for industrial applications, focusing on enhancing intrinsic material stability, designing multi-field coupled reactors, and optimizing system energy efficiency. Full article
(This article belongs to the Section Membrane Applications for Energy)
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16 pages, 9013 KB  
Article
Hybrid Membranes Based on Track-Etched Membranes and Nanofiber Layer for Water–Oil Separation and Membrane Distillation of Low-Level Liquid Radioactive Wastes and Salt Solutions
by Arman B. Yeszhanov, Aigerim Kh. Shakayeva, Maxim V. Zdorovets, Daryn B. Borgekov, Artem L. Kozlovskiy, Pavel V. Kharkin, Dmitriy A. Zheltov, Marina V. Krasnopyorova, Olgun Güven and Ilya V. Korolkov
Membranes 2025, 15(7), 202; https://doi.org/10.3390/membranes15070202 - 4 Jul 2025
Viewed by 725
Abstract
In this work, hybrid membranes were fabricated by depositing polyvinyl chloride (PVC) fibers onto PET track-etched membranes (TeMs) using the electrospinning technique. The resulting structures exhibited enhanced hydrophobicity, with contact angles reaching 155°, making them suitable for applications in both water–oil mixture separation [...] Read more.
In this work, hybrid membranes were fabricated by depositing polyvinyl chloride (PVC) fibers onto PET track-etched membranes (TeMs) using the electrospinning technique. The resulting structures exhibited enhanced hydrophobicity, with contact angles reaching 155°, making them suitable for applications in both water–oil mixture separation and membrane distillation processes involving low-level liquid radioactive waste (LLLRW), saline solutions, and natural water sources. The use of hybrids of TeMs and nanofiber membranes has significantly increased productivity compared to TeMs only, while maintaining a high degree of purification. Permeate obtained after MD of LLLRW and river water was analyzed by conductometry and the atomic emission spectroscopy (for Sr, Cs, Al, Mo, Co, Sb, Ca, Fe, Mg, K, and Na). The activity of radioisotopes (for 124Sb, 65Zn, 60Co, 57Co, 137Cs, and 134Cs) was evaluated by gamma-ray spectroscopy. In most cases, the degree of rejection was between 95 and 100% with a water flux of up to 17.3 kg/m2·h. These membranes were also tested in the separation of cetane–water emulsion with productivity up to 47.3 L/m2·min at vacuum pressure of 700 mbar and 15.2 L/m2·min at vacuum pressure of 900 mbar. Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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17 pages, 5613 KB  
Article
Hierarchical Affinity Engineering in Amine-Functionalized Silica Membranes for Enhanced CO2 Separation: A Combined Experimental and Theoretical Study
by Zhenghua Guo, Qian Li, Kaidi Guo and Liang Yu
Membranes 2025, 15(7), 201; https://doi.org/10.3390/membranes15070201 - 2 Jul 2025
Viewed by 587
Abstract
Excessive carbon dioxide (CO2) emissions represent a critical challenge in mitigating global warming, necessitating advanced separation technologies for efficient carbon capture. Silica-based membranes have attracted significant attention due to their exceptional chemical, thermal, and mechanical stability under harsh operating conditions. In [...] Read more.
Excessive carbon dioxide (CO2) emissions represent a critical challenge in mitigating global warming, necessitating advanced separation technologies for efficient carbon capture. Silica-based membranes have attracted significant attention due to their exceptional chemical, thermal, and mechanical stability under harsh operating conditions. In this study, we introduce a novel layered hybrid membrane designed based on amine-functionalized silica precursors, where a distinct affinity gradient is engineered by incorporating two types of amine-functionalized materials. The top layer was composed of high-affinity amine species to maximize CO2 sorption, while a sublayer with milder affinity facilitated smooth CO2 diffusion, thereby establishing a continuous solubility gradient across the membrane. A dual approach, combining comprehensive experimental testing and rigorous theoretical modeling, was employed to elucidate the underlying CO2 transport mechanisms. Our results reveal that the hierarchical structure significantly enhances the intrinsic driving force for CO2 permeation, leading to superior separation performance compared to conventional homogeneous facilitated transport membranes. This study not only provides critical insights into the design principles of affinity gradient membranes but also demonstrates their potential for scalable, high-performance CO2 separation in industrial applications. Full article
(This article belongs to the Section Membrane Applications for Gas Separation)
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24 pages, 1083 KB  
Review
Membrane-Based CO2 Capture Across Industrial Sectors: Process Conditions, Case Studies, and Implementation Insights
by Jin Woo Park, Soyeon Heo, Jeong-Gu Yeo, Sunghoon Lee, Jin-Kuk Kim and Jung Hyun Lee
Membranes 2025, 15(7), 200; https://doi.org/10.3390/membranes15070200 - 2 Jul 2025
Viewed by 2075
Abstract
Membrane-based CO2 capture has emerged as a promising technology for industrial decarbonization, offering advantages in energy efficiency, modularity, and environmental performance. This review presents a comprehensive assessment of membrane processes applied across major emission-intensive sectors, including power generation, cement, steelmaking, and biogas [...] Read more.
Membrane-based CO2 capture has emerged as a promising technology for industrial decarbonization, offering advantages in energy efficiency, modularity, and environmental performance. This review presents a comprehensive assessment of membrane processes applied across major emission-intensive sectors, including power generation, cement, steelmaking, and biogas upgrading. Drawing from pilot-scale demonstrations and simulation-based studies, we evaluate how flue gas characteristics, such as CO2 concentration, pressure, temperature, and impurity composition, govern membrane selection, process design, and operational feasibility. Case studies highlight the technical viability of membrane systems under a wide range of industrial conditions, from low-CO2 NGCC flue gas to high-pressure syngas and CO2-rich cement emissions. Despite these advances, this review discusses the key remaining challenges for the commercialization of membrane-based CO2 capture and includes perspectives on process design and techno-economic evaluation. The insights compiled in this review are intended to support the design of application-specific membrane systems and guide future efforts toward scalable and economically viable CO2 capture across industrial sectors. Full article
(This article belongs to the Special Issue Novel Membranes for Carbon Capture and Conversion)
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28 pages, 3292 KB  
Article
Optimization of the Quality of Reclaimed Water from Urban Wastewater Treatment in Arid Region: A Zero Liquid Discharge Pilot Study Using Membrane and Thermal Technologies
by Maria Avramidi, Constantinos Loizou, Maria Kyriazi, Dimitris Malamis, Katerina Kalli, Angelos Hadjicharalambous and Constantina Kollia
Membranes 2025, 15(7), 199; https://doi.org/10.3390/membranes15070199 - 1 Jul 2025
Cited by 1 | Viewed by 925
Abstract
With water availability being one of the world’s major challenges, this study aims to propose a Zero Liquid Discharge (ZLD) system for treating saline effluents from an urban wastewater treatment plant (UWWTP), thereby supplementing into the existing water cycle. The system, which employs [...] Read more.
With water availability being one of the world’s major challenges, this study aims to propose a Zero Liquid Discharge (ZLD) system for treating saline effluents from an urban wastewater treatment plant (UWWTP), thereby supplementing into the existing water cycle. The system, which employs membrane (nanofiltration and reverse osmosis) and thermal technologies (multi-effect distillation evaporator and vacuum crystallizer), has been installed and operated in Cyprus at Larnaca’s WWTP, for the desalination of the tertiary treated water, producing high-quality reclaimed water. The nanofiltration (NF) unit at the plant operated with an inflow concentration ranging from 2500 to 3000 ppm. The performance of the installed NF90-4040 membranes was evaluated based on permeability and flux. Among two NF operation series, the second—operating at 75–85% recovery and 2500 mg/L TDS—showed improved membrane performance, with stable permeability (7.32 × 10−10 to 7.77 × 10−10 m·s−1·Pa−1) and flux (6.34 × 10−4 to 6.67 × 10−4 m/s). The optimal NF operating rate was 75% recovery, which achieved high divalent ion rejection (more than 99.5%). The reverse osmosis (RO) unit operated in a two-pass configuration, achieving water recoveries of 90–94% in the first pass and 76–84% in the second. This setup resulted in high rejection rates of approximately 99.99% for all major ions (Cl−, Na+, Ca2+, and Mg2+), reducing the permeate total dissolved solids (TDS) to below 35 mg/L. The installed multi-effect distillation (MED) unit operated under vacuum and under various inflow and steady-state conditions, achieving over 60% water recovery and producing high-quality distillate water (TDS < 12 mg/L). The vacuum crystallizer (VC) further concentrated the MED concentrate stream (MEDC) and the NF concentrate stream (NFC) flows, resulting in distilled water and recovered salts. The MEDC process produced salts with a purity of up to 81% NaCl., while the NFC stream produced mixed salts containing approximately 46% calcium salts (mainly as sulfates and chlorides), 13% magnesium salts (mainly as sulfates and chlorides), and 38% sodium salts. Overall, the ZLD system consumed 12 kWh/m3, with thermal units accounting for around 86% of this usage. The RO unit proved to be the most energy-efficient component, contributing 71% of the total water recovery. Full article
(This article belongs to the Special Issue Applications of Membrane Distillation in Water Treatment and Reuse)
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14 pages, 2508 KB  
Article
Enhancement of Efficiency in an Ex Situ Coprecipitation Method for Superparamagnetic Bacterial Cellulose Hybrid Materials
by Thaís Cavalcante de Souza, Italo José Batista Durval, Hugo Moraes Meira, Andréa Fernanda de Santana Costa, Eduardo Padrón Hernández, Attilio Converti, Glória Maria Vinhas and Leonie Asfora Sarubbo
Membranes 2025, 15(7), 198; https://doi.org/10.3390/membranes15070198 - 1 Jul 2025
Viewed by 572
Abstract
Superparamagnetic magnetite nanoparticles (Fe3O4) have garnered considerable interest due to their unique magnetic properties and potential for integration into multifunctional biomaterials. In particular, their incorporation into bacterial cellulose (BC) matrices offers a promising route for developing sustainable and high-performance [...] Read more.
Superparamagnetic magnetite nanoparticles (Fe3O4) have garnered considerable interest due to their unique magnetic properties and potential for integration into multifunctional biomaterials. In particular, their incorporation into bacterial cellulose (BC) matrices offers a promising route for developing sustainable and high-performance magnetic composites. Numerous studies have explored BC-magnetite systems; however, innovations combining ex situ coprecipitation synthesis within BC matrices, tailored reagent molar ratios, stirring protocols, and purification processes remain limited. This study aimed to optimize the ex situ coprecipitation method for synthesizing superparamagnetic magnetite nanoparticles embedded in BC membranes, focusing on enhancing particle stability and crystallinity. BC membranes containing varying concentrations of magnetite (40%, 50%, 60%, and 70%) were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). The resulting magnetic BC membranes demonstrated homogenous dispersion of nanoparticles, improved crystallite size (6.96 nm), and enhanced magnetic saturation (Ms) (50.4 emu/g), compared to previously reported methods. The adoption and synergistic optimization of synthesis parameters—unique to this study—conferred greater control over the physicochemical and magnetic properties of the composites. These findings position the optimized BC-magnetite nanocomposites as highly promising candidates for advanced applications, including electromagnetic interference (EMI) shielding, electronic devices, gas sensors, MRI contrast agents, and targeted drug delivery systems. Full article
(This article belongs to the Section Membrane Fabrication and Characterization)
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18 pages, 5149 KB  
Article
Construction of Transport Channels by HNTs@ZIF-67 Composites in a Mixed-Matrix Membrane for He/CH4 Separation
by Jiale Zhang, Huixin Dong, Fei Guo, Huijun Yi, Xiaobin Jiang, Gaohong He and Wu Xiao
Membranes 2025, 15(7), 197; https://doi.org/10.3390/membranes15070197 - 30 Jun 2025
Cited by 1 | Viewed by 528
Abstract
In this work, HNTs@ZIF-67 composites were synthesized using the in situ growth method and incorporated into 6FDA-TFMB to prepare mixed-matrix membranes (MMMs). Scanning electron microscope (SEM) and transmission electron microscope (TEM) proved that the HNTs@ZIF-67 composite not only retained the hollow structure of [...] Read more.
In this work, HNTs@ZIF-67 composites were synthesized using the in situ growth method and incorporated into 6FDA-TFMB to prepare mixed-matrix membranes (MMMs). Scanning electron microscope (SEM) and transmission electron microscope (TEM) proved that the HNTs@ZIF-67 composite not only retained the hollow structure of HNTs, but also formed a continuous ZIF-67 transport layer on the surface of HNTs. The results of gas permeability experiments showed that with the increase in HNTs@ZIF-67 incorporation, the He permeability and He/CH4 selectivity of MMMs showed a trend of increasing first and then decreasing. When the loading is 5 wt%, the He permeability and He/CH4 selectivity of MMMs reach 116 Barrer and 305, which are 22.11% and 79.41% higher than the pure 6FDA-TFMB membrane. The results of density functional theory (DFT) and Monte Carlo (MC) calculations reveal that He diffuses more easily inside ZIF-67, HNTs and 6FDA-TFMB than CH4, and ZIF-67 shows larger adsorption energy with He than HNTs and 6FDA-TFMB, indicating that He is easily adsorbed by ZIF-67 in MMMs. Based on experimental and molecular simulation results, the mechanism of HNTs@ZIF-67 improving the He/CH4 separation performance of MMMs was summarized. With the advantage of a smaller molecular kinetic diameter, He can diffuse through ZIF-67 on the tube orifice of HNTs@ZIF-67 and enter the HNTs’ hollow tube for rapid transmission. At the same time, He can also be rapidly transferred in the continuous ZIF-67 transport channel layer, which improves the He permeability and the He/CH4 selectivity of MMMs. Full article
(This article belongs to the Special Issue High-Performance Composite Membrane for Gas Separation and Capture)
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19 pages, 3826 KB  
Article
Highly Conductive PEO/PAN-Based SN-Containing Electrospun Membranes as Solid Polymer Electrolytes
by Anna Maria Kirchberger, Patrick Walke, Janio Venturini, Leo van Wüllen and Tom Nilges
Membranes 2025, 15(7), 196; https://doi.org/10.3390/membranes15070196 - 30 Jun 2025
Viewed by 739
Abstract
Solid polymer electrolytes (SPEs) have garnered significant attention due to their potential in all-solid-state batteries (ASSBs). However, adoption remains constrained by challenges such as low thermal stability and limited ionic conductivity. Here, we report on an electrospun (PAN/PEO)- conductive salt (LiBF4) [...] Read more.
Solid polymer electrolytes (SPEs) have garnered significant attention due to their potential in all-solid-state batteries (ASSBs). However, adoption remains constrained by challenges such as low thermal stability and limited ionic conductivity. Here, we report on an electrospun (PAN/PEO)- conductive salt (LiBF4) system, where the influence of varying polyacrylonitrile (PAN) and polyethylene oxide (PEO) ratios, along with different plasticizer concentrations, is evaluated. Notably, the 50:50 PAN/PEO sample exhibited the highest ionic conductivity, reaching 1∙10−2 S/cm at 55 °C. This system also balanced conductivity and processability. Succinonitrile (SN) significantly influenced the morphology and conductivity. Samples with increased SN content showed enhanced capacity in symmetrical cells, achieving ~140 mAs/cm2 for an 18:9:1 polymer (PAN/PEO):SN:conductive salt (LiBF4) composition. The enhanced lithium-ion conductivity of the electrospun blend is attributed to the deliberate use of an unmixable PAN–PEO system. Their immiscibility creates well-defined interfacial regions within fibers, acting as efficient lithium-ion pathways. These findings support electrospun polymer blends as promising candidates for high-performance SPEs for ASSB development. Full article
(This article belongs to the Special Issue Ion Conducting Membranes and Energy Storage)
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19 pages, 4963 KB  
Article
Fouling Mitigation of Silicon Carbide Membranes by Pre-Deposited Dynamic Membranes for the Separation of Oil-in-Water Emulsions
by Xin Wu, Minfeng Fang and Guanghui Li
Membranes 2025, 15(7), 195; https://doi.org/10.3390/membranes15070195 - 30 Jun 2025
Viewed by 568
Abstract
Membrane fouling poses a significant challenge in the widespread adoption and cost-effective operation of membrane technology. Among different strategies to mitigate fouling, dynamic membrane (DM) technology has emerged as a promising one for effective control and mitigation of membrane fouling. Silicon carbide (SiC) [...] Read more.
Membrane fouling poses a significant challenge in the widespread adoption and cost-effective operation of membrane technology. Among different strategies to mitigate fouling, dynamic membrane (DM) technology has emerged as a promising one for effective control and mitigation of membrane fouling. Silicon carbide (SiC) membranes have attracted considerable attention as membrane materials due to their remarkable advantages, yet membrane fouling is still inevitable in challenging separation tasks, such as oil-in-water (O/W) emulsion separation, and thus effective mitigation of membrane fouling is essential to maximize their economic viability. This study investigates the use of pre-deposited oxide DMs to mitigate the fouling of SiC membranes during the separation of O/W emulsions. Among five screened oxides (Fe2O3, SiO2, TiO2, ZrO2, Al2O3), SiO2 emerged as the most effective DM material due to its favorable combination of particle size, negative surface charge, hydrophilicity, and underwater oleophobicity, leading to minimized oil droplet adhesion via electrostatic repulsion to DM surfaces and enhanced antifouling performance. Parameter optimization in dead-end mode revealed a DM deposition amount of 300 g/m2, a transmembrane pressure (TMP) of 0.25 bar, and a backwashing pressure of 2 bar as ideal conditions, achieving stable oil rejection (~93%) and high pure water flux recovery ratios (FRR, >90%). Cross-flow filtration outperformed dead-end mode, maintaining normalized permeate fluxes of ~0.4–0.5 (cf. ~0.2 in dead-end) and slower FRR decline, attributed to reduced concentration polarization and enhanced DM stability under tangential flow. Optimal cross-flow conditions included a DM preparation time of 20 min, a TMP of 0.25 bar, and a flow velocity of 0.34 m/s. The results establish SiO2-based DMs as a cost-effective strategy to enhance SiC membrane longevity and efficiency in O/W emulsion separation. Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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14 pages, 2980 KB  
Communication
Simultaneously Promoting Proton Conductivity and Mechanical Stability of SPEEK Membrane by Incorporating Porous g–C3N4
by Xiaoyao Wang and Benbing Shi
Membranes 2025, 15(7), 194; https://doi.org/10.3390/membranes15070194 - 29 Jun 2025
Cited by 1 | Viewed by 613
Abstract
Proton exchange membranes are widely used in environmentally friendly applications such as fuel cells and electrochemical hydrogen compression. In these applications, an ideal proton exchange membrane should have both excellent proton conductivity and mechanical strength. Polymer proton exchange membranes, such as sulfonated poly(ether [...] Read more.
Proton exchange membranes are widely used in environmentally friendly applications such as fuel cells and electrochemical hydrogen compression. In these applications, an ideal proton exchange membrane should have both excellent proton conductivity and mechanical strength. Polymer proton exchange membranes, such as sulfonated poly(ether ether ketone) (SPEEK) membranes with high ion exchange capacity, can lead to higher proton conductivity. However, the ionic groups may reduce the interaction between polymer segments, lower the membrane’s mechanical strength, and even cause it to dissolve in water as the temperature exceeds 55 °C. The porous graphitic C3N4 (Pg–C3N4) nanosheet is an important two–dimensional polymeric carbon–based material and has a high content of –NH2 and –NH– groups, which can interact with the sulfonic acid groups in the sulfonated SPEEK polymer, form a more continuous proton transfer channel, and inhibit the movement of the polymer segment, leading to higher proton conductivity and mechanical strength. In this study, we found that a SPEEK membrane containing 3% Pg–C3N4 nanosheets achieves the optimized proton conductivity of 138 mS/cm (80 °C and 100% RH) and a mechanical strength of 74.1 MPa, improving both proton conductivity and mechanical strength by over 50% compared to the SPEEK membrane. Full article
(This article belongs to the Special Issue Advanced Membranes for Fuel Cells and Redox Flow Batteries)
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36 pages, 6029 KB  
Review
Research Progress of Computational Fluid Dynamics in Mixed Ionic–Electronic Conducting Oxygen-Permeable Membranes
by Jun Liu, Jing Zhao, Yulu Liu, Yongfan Zhu, Wanglin Zhou, Zhenbin Gu, Guangru Zhang and Zhengkun Liu
Membranes 2025, 15(7), 193; https://doi.org/10.3390/membranes15070193 - 27 Jun 2025
Viewed by 718
Abstract
Mixed ionic–electronic conducting (MIEC) oxygen-permeable membranes have emerged as a frontier in oxygen separation technology due to their high efficiency, low energy consumption, and broad application potential. In recent years, computational fluid dynamics (CFD) has become a pivotal tool in advancing MIEC membrane [...] Read more.
Mixed ionic–electronic conducting (MIEC) oxygen-permeable membranes have emerged as a frontier in oxygen separation technology due to their high efficiency, low energy consumption, and broad application potential. In recent years, computational fluid dynamics (CFD) has become a pivotal tool in advancing MIEC membrane technology, offering precise insights into the intricate mechanisms of oxygen permeation, heat transfer, and mass transfer through numerical simulations of coupled multiphysics phenomena. In this review, we comprehensively explore the application of CFD in MIEC membrane research, heat and mass transfer analysis, reactor design optimization, and the enhancement of membrane module performance. Additionally, we delve into how CFD, through multiscale modeling and parameter optimization, improves separation efficiency and facilitates practical engineering applications. We also highlight the challenges in current CFD research, such as high computational costs, parameter uncertainties, and model complexities, while discussing the potential of emerging technologies, such as machine learning, to enhance CFD modeling capabilities. This study underscores CFD’s critical role in bridging the fundamental research and industrial applications of MIEC membranes, providing theoretical guidance and practical insights for innovation in clean energy and sustainable technologies. Full article
(This article belongs to the Section Membrane Applications for Energy)
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14 pages, 4047 KB  
Article
Impact of Long-Term Alkaline Cleaning on Ultrafiltration Tubular PVDF Membrane Performances
by Marek Gryta and Piotr Woźniak
Membranes 2025, 15(7), 192; https://doi.org/10.3390/membranes15070192 - 27 Jun 2025
Viewed by 607
Abstract
The application of an ultrafiltration (UF) process with periodic membrane cleaning with the use of alkaline detergent solutions was proposed for the recovery of wash water from car wash effluent. In order to test the resistance of the membranes to the degradation caused [...] Read more.
The application of an ultrafiltration (UF) process with periodic membrane cleaning with the use of alkaline detergent solutions was proposed for the recovery of wash water from car wash effluent. In order to test the resistance of the membranes to the degradation caused by the cleaning solutions, a pilot plant study was carried out for almost two years. The installation included an industrial module with FP100 tubular membranes made of polyvinylidene fluoride (PVDF). The module was fed with synthetic effluent obtained by mixing foaming agents and hydrowax. To limit the fouling phenomenon, the membranes were cleaned cyclically with P3 Ultrasil 11 solution (pH = 11.7) or Insect solution (pH = 11.5). During plant shutdowns, the membrane module was maintained with a sodium metabisulphite solution. Changes in the permeate flux, turbidity, COD, and surfactant rejection were analysed during the study. Scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FTIR) analysis were used to determine the changes in the membrane structure. As a result of the repeated chemical cleaning, the pore size increased, resulting in a more than 50% increase in permeate flux. However, the quality of the recovered wash water did not deteriorate, as an additional separation layer was formed on the membrane surface due to the fouling phenomenon. Full article
(This article belongs to the Special Issue Recent Advances in Polymeric Membranes—Preparation and Applications)
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22 pages, 3169 KB  
Review
A Mini-Review on Electrocatalytic Self-Cleaning Membrane Materials for Sustainable Fouling Control
by Honghuan Yin and Zhonglong Yin
Membranes 2025, 15(7), 191; https://doi.org/10.3390/membranes15070191 - 25 Jun 2025
Viewed by 716
Abstract
Although membrane technology has been widely applied in water treatment, membrane fouling is an inevitable issue that has largely limited its application. Benefiting from the advantages of green power, easy integration and low chemical consumption, electrocatalytic membrane (ECM) technology received attention, using it [...] Read more.
Although membrane technology has been widely applied in water treatment, membrane fouling is an inevitable issue that has largely limited its application. Benefiting from the advantages of green power, easy integration and low chemical consumption, electrocatalytic membrane (ECM) technology received attention, using it to enable electrically driven self-cleaning performance recently, making it highly desirable for sustainable fouling control. In this work, we comprehensively summarized the conventional (e.g., carbonaceous materials, metal and metal oxide) and emerging (e.g., metal–organic framework and MXene) materials for the fabrication of an ECM. Then the fabrication methods and operating modes of an ECM were emphasized. Afterwards, the application of different ECM materials in membrane fouling control was highlighted and the corresponding mechanism was revealed. Based on existing research findings, we proposed the challenges and future prospects of ECM materials for practical application. This study provides enlightening knowledge into the development of ECM materials for sustainable fouling control. 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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27 pages, 9897 KB  
Article
Bi-Objective Optimization of Techno-Economic and Environmental Performance of CO2 Capture Strategy Involving Two-Stage Membrane-Based Separation with Recycling
by Nobuo Hara, Satoshi Taniguchi, Takehiro Yamaki, Thuy T.H. Nguyen and Sho Kataoka
Membranes 2025, 15(7), 190; https://doi.org/10.3390/membranes15070190 - 24 Jun 2025
Viewed by 647
Abstract
To effectively implement complex CO2 capture, utilization, and storage (CCUS) processes, it is essential to optimize their design by considering various factors. This research bi-objectively optimized a two-stage membrane-based separation process that includes recycling, concentrating on minimizing both costs and CO2 [...] Read more.
To effectively implement complex CO2 capture, utilization, and storage (CCUS) processes, it is essential to optimize their design by considering various factors. This research bi-objectively optimized a two-stage membrane-based separation process that includes recycling, concentrating on minimizing both costs and CO2 emissions. The implemented algorithm combined experimental design, machine learning, genetic algorithms, and Bayesian optimization. Under the constraints of a recovery rate of 0.9 and a produced CO2 purity of 0.95, six case studies were conducted on two types of membrane performance: the Robeson upper bound and a tenfold increase in permeability. The maximum value of α*(CO2/N2), used as a constraint, was adjusted to three levels: 50, 100, and 200. The analysis of the Pareto solutions and the relationship between each design variable and the final evaluation index indicates that electricity consumption significantly impacts operating costs and CO2 emissions. The results of the case studies quantitatively clarify that improving the α*(CO2/N2) results in a greater enhancement of process performance than increasing the membrane’s performance by increasing its permeability. Our bi-objective optimization analysis allowed us to effectively evaluate the membrane’s CO2 separation and individual CCUS processes. Full article
(This article belongs to the Special Issue Novel Membranes for Carbon Capture and Conversion)
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28 pages, 6673 KB  
Article
Valorization of Anaerobic Liquid Digestates Through Membrane Processing and Struvite Recovery—The Case of Dairy Effluents
by Anthoula C. Karanasiou, Charikleia K. Tsaridou, Dimitrios C. Sioutopoulos, Christos Tzioumaklis, Nikolaos Patsikas, Sotiris I. Patsios, Konstantinos V. Plakas and Anastasios J. Karabelas
Membranes 2025, 15(7), 189; https://doi.org/10.3390/membranes15070189 - 24 Jun 2025
Viewed by 743
Abstract
An integrated process scheme is developed for valorizing filtered liquid digestates (FLD) from an industrial anaerobic digestion (AD) plant treating dairy-processing effluents with relatively low nutrient concentrations. The process scheme involves FLD treatment by nanofiltration (NF) membranes, followed by struvite recovery from the [...] Read more.
An integrated process scheme is developed for valorizing filtered liquid digestates (FLD) from an industrial anaerobic digestion (AD) plant treating dairy-processing effluents with relatively low nutrient concentrations. The process scheme involves FLD treatment by nanofiltration (NF) membranes, followed by struvite recovery from the NF-retentate. An NF pilot unit (designed for this purpose) is combined with a state-of-the-art NF/RO process simulator. Validation of simulator results with pilot data enables reliable predictions required for scaling up NF systems. The NF permeate meets the standards for restricted irrigation and/or reuse. Considering the significant nutrient concentrations in the NF retentate (i.e., ~500 mg/L NH4-N, ~230 mg/L PO4-P), struvite recovery/precipitation is investigated, including determination of near-optimal processing conditions. Maximum removal of nutrients, through production of struvite-rich precipitate, is obtained at a molar ratio of NH4:Mg:PO4 = 1:1.5:1.5 and pH = 10 in the treated stream, attained through the addition of Κ2HPO4, ΜgCl2·6H2O, and NaOH. Furthermore, almost complete struvite precipitation is achieved within ~30 min, whereas precipitate/solid drying at modest/ambient temperature is appropriate to avoid struvite degradation. Under the aforementioned conditions, a significant amount of dry precipitate is obtained, i.e., ~12 g dry mass per L of treated retentate, including crystalline struvite. The approach taken and the obtained positive results provide a firm basis for further development of this integrated process scheme towards sustainable large-scale applications. Full article
(This article belongs to the Special Issue Membrane and Other Innovative Technologies for Water Purification: Design, Development, and Application)
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