Membranes

4 pages, 185 KB

Open AccessEditorial

Green Membrane Technologies: Advancements in Materials and Energy Efficiency for Water Treatment

by Jehad A. Kharraz

Membranes 2026, 16(5), 168; https://doi.org/10.3390/membranes16050168 - 4 May 2026

The growing global water crisis continues to place unprecedented pressure on water treatment technologies to deliver higher efficiency, lower energy consumption, and reduced environmental impacts [...] Full article

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

18 pages, 2812 KB

Open AccessArticle

A Metal Importer and Exporter Interact Differently in the Chloroplast and Cell Membrane

by Karnelia Paul, Biswajit Ray, Chinmay Saha, Anupam Roy, Sohini Basu and Anindita Seal

Membranes 2026, 16(5), 167; https://doi.org/10.3390/membranes16050167 - 2 May 2026

Abstract

Metal homeostasis, which coordinates the influx and efflux of essential elements such as iron (Fe) and manganese (Mn) in chloroplasts, is essential for optimum photosynthesis, especially in metal-accumulating plants. Brassica juncea (Indian mustard) is a metal-tolerant species with a strong metal accumulation capacity, [...] Read more.

Metal homeostasis, which coordinates the influx and efflux of essential elements such as iron (Fe) and manganese (Mn) in chloroplasts, is essential for optimum photosynthesis, especially in metal-accumulating plants. Brassica juncea (Indian mustard) is a metal-tolerant species with a strong metal accumulation capacity, making it a suitable model for studying transition metal homeostasis. In this study, we identified two efflux transporters, BjYSL6.1 and BjYSL6.4, that localize in the endomembrane system of Schizosaccharomyces pombe and interact with the chloroplast Mn influx transporter BjNRAMP4.1 at the plasma membrane and within the chloroplasts. Bimolecular fluorescence complementation and split-ubiquitin yeast two-hybrid assays confirmed specific protein–protein interactions among these transporters, as well as with the membrane-bound thioredoxin BjHCF164, a known regulator of photosynthetic electron transport. Gene expression studies revealed that BjNRAMP4.1 and BjYSL6 isoforms are inversely regulated under Fe and Mn stress conditions, with BjNRAMP4.1 being strongly induced under deficiency, whereas BjYSL6.1 and BjYSL6.4 are downregulated. These findings suggest that a coordinated network involving BjNRAMP4.1, BjYSL6s, and BjHCF164 modulates metal influx and efflux at the chloroplast and plasma membrane interfaces, thereby maintaining metal homeostasis, which is critical for photosynthetic efficiency in B. juncea. Full article

(This article belongs to the Special Issue Membrane Interaction Between Lipids, Proteins and Peptides, 2nd Edition)

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23 pages, 4915 KB

Open AccessArticle

New Oxicam Derivatives—Studies of Membrane Interactions, Cytotoxicity, Cyclooxygenase Inhibition and Molecular Docking

by Jadwiga Maniewska, Katarzyna Gębczak, Łucja Cwynar-Zając, Żaneta Czyżnikowska and Berenika M. Szczęśniak-Sięga

Membranes 2026, 16(5), 166; https://doi.org/10.3390/membranes16050166 - 1 May 2026

Abstract

Oxicam derivatives, a class of nonsteroidal anti-inflammatory drugs (NSAIDs), are important scaffolds for developing biologically active compounds. In this study, arylpiperazine oxicam derivatives (PR24–PR50) were examined for membrane interactions, cytotoxic activity, cyclooxygenase inhibition, and potential binding to COX-2 protein. Membrane interactions were examined [...] Read more.

Oxicam derivatives, a class of nonsteroidal anti-inflammatory drugs (NSAIDs), are important scaffolds for developing biologically active compounds. In this study, arylpiperazine oxicam derivatives (PR24–PR50) were examined for membrane interactions, cytotoxic activity, cyclooxygenase inhibition, and potential binding to COX-2 protein. Membrane interactions were examined using differential scanning calorimetry (DSC) in phospholipid bilayers formed from 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). All compounds altered the thermotropic properties of the lipid bilayer, showing concentration-dependent decreases in phase transition temperature, indicating incorporation to bilayer and partial disruption of lipid organization. Cytotoxicity, assessed using the MTT assay in breast cancer (MCF-7, MCF-7/DX), colorectal cancer (LOVO, LOVO/DX), and normal V79 cell lines, showed moderate effects, particularly against colorectal cancer cells. Cyclooxygenase inhibition was rather weak, with IC₅₀ values in the high micromolar range, indicating limited anti-inflammatory potential compared with reference COX inhibitors, although docking studies suggested possible interactions with the COX-2 active site. The obtained results indicate that the biological activity of the arylpiperazine oxicam derivatives is primarily associated with cytotoxicity and membrane effects rather than COX inhibition. These limitations should be considered in the design of future membrane-targeted bioactive compounds. Full article

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

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19 pages, 2463 KB

Open AccessArticle

Leveraging Electrical Network Models for Solving Fick’s Second Law of Diffusion in Membrane Gas Permeation

by Zheng Cao, Boguslaw Kruczek and Jules Thibault

Membranes 2026, 16(5), 165; https://doi.org/10.3390/membranes16050165 - 1 May 2026

Abstract

The permeation of gases through membranes is a fundamental process with wide-ranging applications, from gas separation and fuel cell technology to respiratory physiology. Governed by Fick’s second law of diffusion, the mathematical modelling of such transport processes often becomes analytically and computationally challenging, [...] Read more.

The permeation of gases through membranes is a fundamental process with wide-ranging applications, from gas separation and fuel cell technology to respiratory physiology. Governed by Fick’s second law of diffusion, the mathematical modelling of such transport processes often becomes analytically and computationally challenging, especially in heterogeneous, mixed matrix, or multilayered systems. To navigate these complexities, this study revisits and expands upon the use of electrical analogies as an intuitive and powerful modelling approach rooted in mid-20th-century analog computing. By leveraging the mathematical equivalence between diffusion and electrical conduction, we construct an equivalent electrical network that mirrors the transient behaviour of gas permeation across membranes. In this framework, concentration gradients are represented as voltage differences, diffusive fluxes as electrical currents, and diffusional resistances as circuit resistances. While traditional applications of electrical analogies have largely focused on steady-state phenomena, our approach enables dynamic analysis, offering conceptual clarity and computational efficiency. This methodology not only simplifies the solution of Fick’s second law but also reinforces the enduring relevance of analogical thinking in modern engineering practice. Comparative results demonstrate that the equivalent electrical circuit closely aligns with both analytical and finite difference solutions, validating its effectiveness and accuracy. Full article

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

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22 pages, 3282 KB

Open AccessArticle

A Technical Feasibility Study of the Recovery of Used Lubricant Oil Using Ceramic Ultrafiltration Membranes

by Madina Mohamed, Pieter Vandezande and Anita Buekenhoudt

Membranes 2026, 16(5), 164; https://doi.org/10.3390/membranes16050164 - 1 May 2026

Abstract

This laboratory-scale experimental study investigated the purification level of used lubricant oil (ULO) filtration using a large variety of ceramic UF membranes, allowing for treatment at high temperatures unreachable for polymeric membranes. Varying pore sizes (5 nm, 10 nm, 30 nm, and 100 [...] Read more.

This laboratory-scale experimental study investigated the purification level of used lubricant oil (ULO) filtration using a large variety of ceramic UF membranes, allowing for treatment at high temperatures unreachable for polymeric membranes. Varying pore sizes (5 nm, 10 nm, 30 nm, and 100 nm) were included as well as a range of materials (Al₂O₃, TiO₂, and ZrO₂). Moreover, four different grafting techniques were applied to alter the surface chemistry of the native membranes from hydrophilic to more hydrophobic or oleophilic, intending to further increase UF flux and/or retention. Benchmark native 10 nm TiO₂ membranes shows a stable flux of 7 to 9 kg/h·m² at 110 °C, strong (metal) impurity removal, and unexpected high water retention. All other membranes tested show fluxes that never exceed the ones for the 10 nm benchmark membranes, elucidating that surface chemistry does not help to improve the flux. In general, membrane performance is very similar for all membranes, except for flux and water retention. Systematically, high-flux membranes show high water retention, while very-low-flux membranes preferentially pass water. The variation in flux and water retention as a function of membrane pore size (before grafting) shows that surface chemistry only plays a role when the effective pore size becomes small. The study results allow for the selection of the best membranes for initial ULO treatment. 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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22 pages, 3582 KB

Open AccessArticle

High Desalination Performance of Polyamide Composite Reverse Osmosis Membranes Based on Integrated Diamine Monomers

by Caiyun Liu, Chen Chen, Wencai Zhang, Hongyang Ma, Shyam Venkateswaran and Benjamin S. Hsiao

Membranes 2026, 16(5), 163; https://doi.org/10.3390/membranes16050163 - 30 Apr 2026

Abstract

Polyamide thin-film composite reverse osmosis membranes were fabricated through interfacial polymerization (IP), wherein trimesoyl chloride (TMC) and isomeric diamine monomers including o-phenylenediamine (OPD), m-phenylenediamine (MPD), p-phenylenediamine (PPD), and methyl-substituted monomers such as 2,3-diaminotoluene (MOPD), 2,4-diaminotoluene (MMPD), 2,5-diaminotoluene (MPPD), and 2,6-diaminotoluene [...] Read more.

Polyamide thin-film composite reverse osmosis membranes were fabricated through interfacial polymerization (IP), wherein trimesoyl chloride (TMC) and isomeric diamine monomers including o-phenylenediamine (OPD), m-phenylenediamine (MPD), p-phenylenediamine (PPD), and methyl-substituted monomers such as 2,3-diaminotoluene (MOPD), 2,4-diaminotoluene (MMPD), 2,5-diaminotoluene (MPPD), and 2,6-diaminotoluene (2,6-MMPD) were employed. The membranes with high permeation flux and rejection ratio were eventually applied in the desalination of brackish water. The regional effects of the amino and methyl substituent on the desalination performance of the RO membranes in terms of permeation flux and rejection ratio were investigated extensively. A molecular dynamics simulation based on the configuration of monomers was performed to theoretically explore the effects of amino and methyl groups of the monomer on the packing density of the aromatic molecular structure and, consequently, on the desalination performance of the corresponding RO membranes. The RO membranes with integrated monomers exhibited two times higher permeation flux than that of a pristine RO membrane while remaining the high rejection ratio. Moreover, a long-term desalination performance of the RO membrane was also demonstrated, where two times higher permeation flux than that of conventional and commercial RO membranes was achieved, while the rejection ratio was maintained at 97.6% which was comparable with that of the commercial RO membranes. Full article

(This article belongs to the Special Issue Advances in Reverse Osmosis Membrane Research Through Computer Simulation)

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25 pages, 6334 KB

Open AccessArticle

Effects of Hydraulic Diameters on CO₂ Absorption in Flat-Plate Membrane Contactors with Inserted S-Ribbed Carbon Fiber Turbulence Promoters

by Chii-Dong Ho, Ping-Cheng Hsieh, Thiam Leng Chew and Jyun-Jhe Li

Membranes 2026, 16(5), 162; https://doi.org/10.3390/membranes16050162 - 30 Apr 2026

Abstract

One-dimensional mass transfer resistance-in-series framework was developed theoretically and validated experimentally using a flat-plate polytetrafluoroethylene/polypropylene (PTFE/PP) membrane module to predict CO₂ absorption fluxes and concentration distributions. The decline in CO₂ absorption efficiency along the membrane module is primarily attributed to increased [...] Read more.

One-dimensional mass transfer resistance-in-series framework was developed theoretically and validated experimentally using a flat-plate polytetrafluoroethylene/polypropylene (PTFE/PP) membrane module to predict CO₂ absorption fluxes and concentration distributions. The decline in CO₂ absorption efficiency along the membrane module is primarily attributed to increased concentration polarization resistance and a reduced driving force concentration gradient. To alleviate these limitations, carbon fiber promoters were strategically embedded to suppress concentration polarization, reduce the mass transfer resistances, and enhance turbulence intensity. In the present study, device performance was further improved by implementing properly ascending or descending hydraulic equivalent widths along the absorbent feed channel. Under the descending configuration, an absorption flux enhancement of up to 44.94% was achieved relative to an empty-channel module (i.e., without S-ribbed carbon fiber inserts). Theoretical formulations were established to predict absorption fluxes under varying monoethanolamine (MEA) volumetric flow rates, CO₂/N₂ mixture flow rates, and inlet CO₂ feed concentrations. The model predictions showed good agreement with experimental results obtained using MEA solutions under both ascending and descending hydraulic width operations, demonstrating effective mitigation of polarization effects and enhanced absorption flux along the absorbent feed channel. An economic assessment of the S-ribbed carbon fiber module was conducted by evaluating the trade-off between absorption flux enhancement and incremental power consumption. The results indicate that the proposed design provides a practical and economically viable approach for improving the performance of membrane-based CO₂ capture technologies. In addition, an enhanced Sherwood number correlation, expressed in a simplified form, was developed and employed to estimate the mass transfer coefficients of CO₂ membrane absorption modules incorporating S-ribbed carbon fiber promoters. Full article

(This article belongs to the Special Issue Advanced Membrane Technologies for Gas Capture and Clean Energy: Multiscale Insights and Applications)

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28 pages, 6932 KB

Open AccessArticle

Comparative Evaluation of QQ Media Materials for MBR Applications: An Environmental Footprint Approach in Urban Wastewater Treatment Plants

by Semanur Korkusuz-Soylu, Rabia Ardic-Demirbilekli, Merve Yilmaz, Ismail Koyuncu and Borte Kose-Mutlu

Membranes 2026, 16(5), 161; https://doi.org/10.3390/membranes16050161 - 30 Apr 2026

Abstract

Urban wastewater treatment plants face increasing challenges in mitigating environmental impacts while achieving high treatment efficiency. This study explores the optimization of quorum-quenching (QQ) media materials for scalable membrane bioreactor (MBR) applications, focusing on their potential to reduce operational footprints and enhance sustainability. [...] Read more.

Urban wastewater treatment plants face increasing challenges in mitigating environmental impacts while achieving high treatment efficiency. This study explores the optimization of quorum-quenching (QQ) media materials for scalable membrane bioreactor (MBR) applications, focusing on their potential to reduce operational footprints and enhance sustainability. Six immobilization media were evaluated—sodium alginate (SA), polyvinyl alcohol (PVA) beads (P), magnetic beads (M), chitosan magnetic beads (CM), polymer-coated beads (PS), and flat media (SAP)—using a multi-criteria decision analysis (MCDA) framework. Key parameters, including porosity, mechanical strength, quorum-quenching activity, and durability in sludge, were quantitatively weighted according to their operational significance. SA demonstrated the most balanced performance, exhibiting superior durability and cost-effectiveness, whereas SAP showed potential in applications prioritizing high porosity and enhanced QQ activity. The incorporation of QQ media led to a significant reduction in membrane fouling, chemical consumption, and energy consumption in pilot-scale MBR systems. Ecological footprint assessment revealed a 15% reduction in indirect blue water footprints and a 20% decrease in Scope 2 carbon emissions, attributable to reduced operational energy demands. These findings highlight the efficacy of QQ media in improving MBR performance and advancing system-level sustainability. Overall, this study highlights the critical importance of material engineering and ecological footprint integration in the development of next-generation urban wastewater treatment technologies. Full article

(This article belongs to the Special Issue Membrane Fouling and Antifouling Strategies for Water and Wastewater Treatment)

16 pages, 609 KB

Open AccessArticle

Validation of Analytical Results for Counter-Current Flow in Square Channels Separated by a Membrane in a Hemodialysis Module Using Experimental Module Results

by Akram Abdullah and Rathinam Panneer Selvam

Membranes 2026, 16(5), 160; https://doi.org/10.3390/membranes16050160 - 30 Apr 2026

Abstract

Counter-current flow in channels separated by a membrane has been studied by several scientists and researchers. The current study aims to analytically simulate and describe the distribution of pressure, volumetric flow rate, and velocity in square channels separated by a membrane. Consequently, the [...] Read more.

Counter-current flow in channels separated by a membrane has been studied by several scientists and researchers. The current study aims to analytically simulate and describe the distribution of pressure, volumetric flow rate, and velocity in square channels separated by a membrane. Consequently, the study was conducted using one-dimensional (1D) analytical solutions to achieve several objectives: avoiding the execution of experimental tests, reducing the effort required for expensive and time-consuming module design, and enabling easy observation of variations in pressure, volumetric flow rate, and velocity. The 1D analytical solution directly simulates flow in square channels separated by a membrane by solving the continuity equation and Darcy’s law, through which pressure, volumetric flow rate, and velocity are calculated. Experimental results were used to validate the 1D analytical solutions. The results of the current study indicate that pressure decreases from the inlet to the outlet of the channel, while the horizontal velocity decreases from the inlet to the midpoint of the channel length and then increases toward the outlet. The 1D analytical solutions show acceptable accuracy when compared with experimental results. Consequently, these solutions can be used to explore and illustrate the distributions of pressure, volumetric flow rate, and velocity in square channels separated by a membrane, enabling the evaluation of hemodialysis prototype module performance and efficiency prior to fabrication. Full article

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

20 pages, 1031 KB

Open AccessArticle

Genistein and Resveratrol: Inhibitors of Kv1.3 Channels in Cancer Cells

by Andrzej Teisseyre, Anna Uryga, Kamila Środa-Pomianek and Anna Palko-Labuz

Membranes 2026, 16(5), 159; https://doi.org/10.3390/membranes16050159 - 30 Apr 2026

Abstract

Background: Genistein and resveratrol are bioactive compounds isolated from plants, recognized for their diverse biological activities including anti-cancer properties. Both compounds are also known as modulators of various types of ion channels, including voltage-gated potassium channels, Kv1.3. These channels are widely expressed in [...] Read more.

Background: Genistein and resveratrol are bioactive compounds isolated from plants, recognized for their diverse biological activities including anti-cancer properties. Both compounds are also known as modulators of various types of ion channels, including voltage-gated potassium channels, Kv1.3. These channels are widely expressed in normal and cancer tissues. Their activity is crucial in regulating cell proliferation and apoptosis in cells that express Kv1.3 channels. The potential clinical application of channel inhibitors may extend to treating cancers characterized by an overexpression of these channels. Methods: This study investigates the inhibitory effects of genistein and resveratrol on Kv1.3 channels expressed in the cancer cell line Jurkat T by applying a whole-cell patch clamp. Results: Applying both compounds at concentrations ranging from 3 μM to 90 μM leads to a dose-dependent inhibition of channel activity, reducing it to approximately 50% of the control level. This inhibitory effect was reversible and associated with a significant reduction in the activation rate. When combined with simvastatin, the inhibitory effect exhibited synergy; however, it was additive when co-applied with mevastatin. Conclusions: The channel inhibition may putatively be linked to the anti-cancer activities of these compounds on Kv1.3 channel-expressing cancer cells, especially when co-applied with the statins. Full article

(This article belongs to the Special Issue Recent Advances in Biomembrane Models for Studying Interactions with Bio-/Molecules (2nd Edition))

14 pages, 1265 KB

Open AccessArticle

Fabrication of Dual-Phase Mixed Conductor Four-Channel Hollow Fiber Membrane for Hydrogen Separation

by Doudou Jia, Haonan Wang, Zhengkun Liu, Guangru Zhang and Wanqin Jin

Membranes 2026, 16(5), 158; https://doi.org/10.3390/membranes16050158 - 30 Apr 2026

Abstract

Perovskite mixed proton–electron hydrogen-permeable membranes have been widely applied in the field of membrane separation due to their 100% selectivity for hydrogen separation. La_5.5WO_11.25-δ-La_0.87Sr_0.13CrO_3-δ (LWO-LSF) four-channel hollow fiber membranes were prepared by the phase [...] Read more.

Perovskite mixed proton–electron hydrogen-permeable membranes have been widely applied in the field of membrane separation due to their 100% selectivity for hydrogen separation. La_5.5WO_11.25-δ-La_0.87Sr_0.13CrO_3-δ (LWO-LSF) four-channel hollow fiber membranes were prepared by the phase inversion and sintering technique using a one-step thermal processing (OSTP) approach. The effects of temperature, feed gas concentration, sweep gas flow, permeation mode, and water vapor on hydrogen flux were systematically investigated. At 900 °C, the hydrogen permeation flux of 50% H₂/N₂ feed from the shell side to the lumen side was 0.613 mL·min⁻¹·cm⁻², which was 62.59% higher than that from the lumen side to the shell side. The enhanced hydrogen permeation performance is attributed to the lower gas mass transfer resistance under shell-side feeding. Under humidified conditions on the sweep side, the hydrogen flux increased by an additional 3.42%. The presence of water vapor increased the number of proton carriers, effectively enhancing proton–electron-coupled transport and thereby increasing the hydrogen permeation flux. Full article

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

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18 pages, 6411 KB

Open AccessArticle

Ceramic TiO₂ Membrane Modification by Coal Fly Ash (CFA) Particles

by Saidulla Faizullayev, Akbota Adilbekova, Joanna Kujawa and Wojciech Kujawski

Membranes 2026, 16(5), 157; https://doi.org/10.3390/membranes16050157 - 29 Apr 2026

Abstract

Сommercial TiO₂ ceramic membranes were modified using a slip-casting method with coal fly ash (CFA) obtained from a thermal power plant, Almaty, Kazakhstan. The aim was to enhance membrane surface properties for improved oil-in-water emulsion separation while maintaining structural integrity. Suspension of [...] Read more.

Сommercial TiO₂ ceramic membranes were modified using a slip-casting method with coal fly ash (CFA) obtained from a thermal power plant, Almaty, Kazakhstan. The aim was to enhance membrane surface properties for improved oil-in-water emulsion separation while maintaining structural integrity. Suspension of CFA, stabilized with N-dodecylpyridinium chloride (DPC) and polyvinyl alcohol (PVA), was applied as a coating layer on the TiO₂ surface and subsequently sintered under controlled conditions. The resulting membranes were characterized by SEM-EDX (scanning electron microscopy with energy-dispersive X-ray), Raman spectroscopy, contact angle measurements, and zeta potential analysis. The modified membranes exhibited increased hydrophilicity, as indicated by a reduction in water contact angle (WCA) from 43.6 ± 2° to approximately 0°, and a decrease in the underoil contact angle of water (UOCA) from 147.6 ± 2° to 87 ± 2°. Raman spectroscopy confirmed that the TiO₂ structure remained predominantly rutile, with no additional crystalline phases detected from CFA. Despite the improved wettability, pure water and oil-in-water emulsion fluxes decreased slightly, while filtrates displayed smaller oil droplet sizes, indicating enhanced emulsion stability after passage through the modified surface. These findings demonstrate that CFA-modified TiO₂ membranes can serve as a sustainable and cost-effective approach for treating emulsified wastewater, utilizing industrial waste to improve performance without compromising mechanical robustness. Full article

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

13 pages, 3254 KB

Open AccessArticle

Potentiometric Solid-Contact K⁺ Ion-Selective Electrodes Based on the KMnFe(CN)₆ Transducer

by Huali Deng, Zhanhao Liu, Li Niu and Shiyu Gan

Membranes 2026, 16(5), 156; https://doi.org/10.3390/membranes16050156 - 29 Apr 2026

Abstract

Solid-contact ion-selective electrodes (SC-ISEs) are typically constructed using ion-selective membrane (ISM)-based configurations. However, such structures often suffer from water-layer formation and the weak mechanical stability of the ISM. Herein, we report an ISM-free K⁺-SC-ISE based on a Prussian blue analogue transducer, [...] Read more.

Solid-contact ion-selective electrodes (SC-ISEs) are typically constructed using ion-selective membrane (ISM)-based configurations. However, such structures often suffer from water-layer formation and the weak mechanical stability of the ISM. Herein, we report an ISM-free K⁺-SC-ISE based on a Prussian blue analogue transducer, KMnFe(CN)₆, eliminating the need for a conventional ionophore-based ISM layer. KMnFe(CN)₆ was synthesized via a one-step citrate-assisted co-precipitation method. The material functions as a bifunctional transducer, in which the open framework structure with ion-transport channels enables selective K⁺ recognition, while the redox-active Mn centers facilitate ion-to-electron transduction. The fabricated KMnFe(CN)₆-based K⁺ sensor exhibits a near-Nernstian response with a sensitivity of 52.3 ± 1.0 mV dec⁻¹ and a rapid response time of 25 s. The linear range and limit of detection were determined to 10⁻⁴ to 10⁻¹ M and 5.8 × 10⁻⁵ M, respectively. The sensor also demonstrates selectivity to representative interfering ions, with log K_ij of −2.39 ± 0.12 (Na⁺), −2.86 ± 0.09 (Li⁺), −3.06 ± 0.09 (Ca²⁺), −2.74 ± 0.12 (Mg²⁺) and −0.95 ± 0.08 (NH₄⁺). By eliminating the ISM layer, the water-layer effect is effectively avoided, resulting in excellent long-term stability with a potential drift of 57.2 ± 6.1 μV h⁻¹ over 7 days. The sensor was further applied to the analysis of K⁺ in real lake water samples, where the measured concentration showed good agreement with ion chromatography results. This work provides an ISM-free SC-ISE strategy for ion analysis in water environments. Full article

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

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19 pages, 3141 KB

Open AccessArticle

Development of a Zero-Stagnant-Water Purification System Based on Smart Series–Parallel Control of Dual RO Membranes

by Mei Ma, Bin Huang, Lingling Mei, Kan Huang, Ke Xing and Lida Liao

Membranes 2026, 16(5), 155; https://doi.org/10.3390/membranes16050155 - 23 Apr 2026

Abstract

Intermittently operated, tankless reverse osmosis (RO) systems are widely used in decentralized and point-of-use applications, yet water stagnation during idle periods remains a critical challenge, leading to degraded water quality, accelerated fouling, and performance loss. This study presents an experimentally validated engineering solution [...] Read more.

Intermittently operated, tankless reverse osmosis (RO) systems are widely used in decentralized and point-of-use applications, yet water stagnation during idle periods remains a critical challenge, leading to degraded water quality, accelerated fouling, and performance loss. This study presents an experimentally validated engineering solution that eliminates stagnant water in intermittently operated RO systems. A dual-membrane RO configuration with flexible series–parallel switching was developed, enabling membranes to alternate between production and flushing modes. An adaptive control strategy, integrated into the system hardware, regulates membrane switching and flushing based on real-time feed-water quality. The proposed configuration and control framework was evaluated under representative intermittent operating conditions. Experimental results show that the zero-stagnant-water strategy effectively prevents residual water accumulation during shutdown and maintains stable permeate quality, with total dissolved solids consistently below 10 mg/L. Long-term testing further demonstrates reduced membrane fouling and slower performance degradation compared with conventional fixed-operation schemes, resulting in enhanced desalination efficiency and operational stability. Owing to its modular design and simple control logic, the proposed approach is readily transferable to decentralized and point-of-use membrane water treatment systems requiring reliable, high-quality water under intermittent operation. Full article

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

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33 pages, 4610 KB

Open AccessArticle

A Robust Numerical Framework for Hollow-Fiber Membrane Module Simulation and Solver Performance Analysis

by Diego Queiroz Faria de Menezes, Marília Caroline Cavalcante de Sá, Nayher Andres Clavijo Vallejo, Thainá Menezes de Melo, Luiz Felipe de Oliveira Campos, Thiago Koichi Anzai and José Carlos Costa da Silva Pinto

Membranes 2026, 16(4), 154; https://doi.org/10.3390/membranes16040154 - 21 Apr 2026

Abstract

Robust numerical frameworks are essential for the simulation, design, monitoring, and control of membrane-based separation units, particularly under highly nonlinear and industrially relevant operating conditions. In this context, a comprehensive phenomenological and numerical framework is proposed for the simulation of hollow-fiber membrane modules, [...] Read more.

Robust numerical frameworks are essential for the simulation, design, monitoring, and control of membrane-based separation units, particularly under highly nonlinear and industrially relevant operating conditions. In this context, a comprehensive phenomenological and numerical framework is proposed for the simulation of hollow-fiber membrane modules, incorporating coupled mass, momentum (through pressure drop), and energy transport equations. The governing equations are discretized using a rigorous orthogonal collocation formulation, and the performances of two numerical solution strategies are systematically investigated for the first time to allow the in-line and real-time implementation of the model: a steady-state approach based on the Newton–Raphson method with careful treatment of initial estimates, and a pseudotransient formulation. Particularly, an original and consistent numerical treatment is introduced for the energy balance at boundaries where the permeate flow vanishes, enabling the stable incorporation of thermal effects and Joule–Thomson phenomena. The results clearly show that the steady-state Newton–Raphson approach provides the best overall performance in terms of computational efficiency, numerical robustness, and accuracy when physically consistent initial profiles are employed. In particular, the combination of a linear initial guess and a numerical mesh constituted of four collocation points yielded the most favorable balance between convergence speed, numerical robustness, and accuracy for the base-case sensitivity analysis. For monitoring-oriented applications, the numerical choice should be weighted primarily toward computational performance once physical consistency and convergence criteria are satisfied, rather than toward maximum mesh-refinement accuracy. In this context, small differences in internal-fiber profiles can be compensated through real-time permeance estimation and are negligible when compared with measurement uncertainty in real industrial processes. Under extreme operating conditions involving low concentrations, low flow rates, and highly permeable species, the pseudotransient formulation proved to be a reliable auxiliary strategy, enabling robust convergence when suitable initial guesses were not readily available. The proposed framework is validated against experimental data from the literature and subjected to extensive convergence and sensitivity analyses, providing a reliable basis for simulation and for assessing computational feasibility in in-line and real-time monitoring-oriented applications. A full demonstration of digital-twin integration, online parameter updating, reduced-order coupling, and closed-loop control is beyond the scope of the present study and will be addressed in future work. Full article

(This article belongs to the Special Issue Multiscale Modeling and Data-Driven Approaches for Advancing Membrane Separation Processes)

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31 pages, 1480 KB

Open AccessReview

Removal of Contaminants of Emerging Concern from Wastewater Using Photocatalytic Membranes: Current Status and Challenges

by Nelson Kipchumba, Innocentia G. Mkhize, Benton Otieno, Hilary L. Rutto and Seteno K. Ntwampe

Membranes 2026, 16(4), 153; https://doi.org/10.3390/membranes16040153 - 21 Apr 2026

Abstract

The increasing presence of contaminants of emerging concern (CECs) in surface and groundwater is a global concern due to their toxicity, persistence, and bioaccumulation, which lead to undesired effects. Conventional wastewater treatment processes are unable to remove these CECs, necessitating advanced treatment strategies [...] Read more.

The increasing presence of contaminants of emerging concern (CECs) in surface and groundwater is a global concern due to their toxicity, persistence, and bioaccumulation, which lead to undesired effects. Conventional wastewater treatment processes are unable to remove these CECs, necessitating advanced treatment strategies to remove them effectively. Among advanced strategies, photocatalytic membrane treatment has attracted considerable interest among researchers. This review critically examines the fundamental principles governing the performance of photocatalytic membranes. It identifies significant challenges, including photocatalyst leaching, light accessibility, intermediates’ toxicity, and scalability of synthesis and immobilisation techniques. It explains why these factors significantly hinder long-term stability, scalability, and practical deployment of photocatalytic membrane systems and provides potential solutions. Through gap analysis, the review has identified rigorous techno-economic analysis, real-world wastewater validation, and systematic toxicity assessment of degradation intermediates as areas of further study. These targeted actions provide clear pathways to enhance the viability, safety, and commercial readiness of photocatalytic membrane systems. Full article

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

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20 pages, 5883 KB

Open AccessArticle

Transport and Separation Characteristics of PVDF-Based Nanocomposite Membranes in Membrane Distillation

by Syed Farzan Ali Shah, Naif A. Darwish, Nabil Abdel Jabbar, Sameer Al-Asheh, Muhammad Qasim and Farouq S. Mjalli

Membranes 2026, 16(4), 152; https://doi.org/10.3390/membranes16040152 - 21 Apr 2026

Abstract

Water scarcity has increased the need for efficient treatment technologies such as membrane distillation (MD). PMD performance depends strongly on membrane fabrication parameters, particularly polymer concentration and nanoparticle incorporation, which control key transport and separation properties. This study considers fabrication of membranes using [...] Read more.

Water scarcity has increased the need for efficient treatment technologies such as membrane distillation (MD). PMD performance depends strongly on membrane fabrication parameters, particularly polymer concentration and nanoparticle incorporation, which control key transport and separation properties. This study considers fabrication of membranes using different concentrations of polyvinylidene fluoride (PVDF) with the incorporation of different types of nanoparticles to determine the optimum membrane formulation for membrane distillation applications. The results demonstrate that both PVDF concentration and nanoparticle type play a critical role in membrane performance in terms of permeate flux and salt rejection. Among the nanoparticles studied in this work, carbon nanotubes (CNTs) exhibited the most significant enhancement, leading to a substantial increase in water vapor flux while maintaining excellent separation efficiency. The optimized CNT incorporated membrane achieved approximately 99% salt rejection, with superior flux performance, indicating its strong potential for high-efficiency desalination and water treatment using membrane distillation. Full article

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16 pages, 5757 KB

Open AccessArticle

Preparation of a Novel Nanofiltration Membrane and Study of Its Process for Removing Divalent Ions from Xinjiang Oilfield Wastewater

by Zongneng Zheng, Di Liu, Jiahang Wan, Jianping Li, Kun Zhang, Yanxin Li, Haiyi Yang and Junwei Hou

Membranes 2026, 16(4), 151; https://doi.org/10.3390/membranes16040151 - 17 Apr 2026

Abstract

The produced water from the No. 1 Oil Production Plant of Xinjiang Oilfield is rich in divalent ions, including Ca²⁺, Mg²⁺, and SO₄²⁻, leading to extremely high scaling tendency that fails to meet the reinjection standard. [...] Read more.

The produced water from the No. 1 Oil Production Plant of Xinjiang Oilfield is rich in divalent ions, including Ca²⁺, Mg²⁺, and SO₄²⁻, leading to extremely high scaling tendency that fails to meet the reinjection standard. Therefore, highly efficient water softening technology is urgently required for such wastewater treatment. In this study, a novel negatively charged nanofiltration (NF) membrane was fabricated via interfacial polymerization using 2-carboxypiperazine and trimesoyl chloride as monomers. The membrane was systematically characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR), and its rejection performance was investigated under various conditions. Results show that the maximum rejection rates of the NF membrane reached 99% for SO₄²⁻, 81% for Ca²⁺, and 94% for Mg²⁺, respectively. With increasing ion concentration, the removal efficiencies of Ca²⁺ and Mg²⁺ decreased, while that of SO₄²⁻ increased slightly. Higher operating pressure significantly enhanced both ion removal and membrane flux, which was mainly attributed to the synergistic effects of Donnan electrostatic exclusion, membrane surface adsorption, and mass transfer resistance. When applied to treat real produced water from the No. 1 Oil Production Plant, the membrane achieved 100% removal of SO₄²⁻, and 91% and 95% removal of Ca²⁺ and Mg²⁺, respectively. The scaling tendency of the treated effluent was completely eliminated. This work provides theoretical and technical support for the engineering application of nanofiltration technology in oilfield wastewater treatment. Full article

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

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2 pages, 142 KB

Open AccessEditorial

Membranes and Membrane Reactors for Gas Purification and Production: Towards More Sustainable Processes

by Pasquale Francesco Zito

Membranes 2026, 16(4), 150; https://doi.org/10.3390/membranes16040150 - 17 Apr 2026

Abstract

The use of membranes for gas purification and production is becoming increasingly common as a valid alternative to the conventional technologies (i [...] Full article

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

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