Membranes

4 pages, 188 KB

Open AccessEditorial

Closing Editorial: Composition and Biophysical Properties of Lipid Membranes

by Mariana Ferreira

Membranes 2026, 16(4), 143; https://doi.org/10.3390/membranes16040143 - 7 Apr 2026

Biological membranes are essential structural and functional components of living systems, forming the boundaries that define cells and organelles while enabling selective transport, signalling, and energy transduction [...] Full article

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

25 pages, 1579 KB

Open AccessArticle

Modeling and Performance Analysis of a Hybrid Forward Osmosis–Membrane Distillation System for Seawater Desalination

by Zakaria Triki, Zineb Fergani, Hichem Tahraoui, Nassim Moula, Jie Zhang, Abdeltif Amrane, Farid Fadhilah and Amine Aymen Assadi

Membranes 2026, 16(4), 142; https://doi.org/10.3390/membranes16040142 - 2 Apr 2026

Abstract

Hybrid desalination systems that combine osmotic and thermal driving forces offer a promising route to improve water recovery and energy efficiency for high-salinity feedwaters where conventional processes face limitations. This study presents a comprehensive mathematical modeling framework and performance analysis of a hybrid [...] Read more.

Hybrid desalination systems that combine osmotic and thermal driving forces offer a promising route to improve water recovery and energy efficiency for high-salinity feedwaters where conventional processes face limitations. This study presents a comprehensive mathematical modeling framework and performance analysis of a hybrid forward osmosis–membrane distillation (FO-MD) system for seawater desalination. The novel contributions include: (1) a coupled heat, mass, and solute transport model that explicitly accounts for concentration polarization, temperature polarization, reverse salt flux, and their dynamic interactions through the draw solution loop; (2) a quantitative assessment of the synergistic regeneration effect, showing how MD maintains draw solution concentration and stabilizes FO performance over time; (3) systematic evaluation of parameter sensitivity to polarization effects; and (4) comparative energy analysis quantifying specific energy consumption relative to standalone processes. Model predictions were validated against published experimental data, showing good agreement for both FO and MD fluxes (R² > 0.94). The MD flux increased from approximately 2–3 LMH at 30 °C to 17 LMH at 50 °C, confirming vapor pressure enhancement. FO water flux increased significantly with draw solution concentration from 0.2 to 1.1 M due to higher osmotic pressure differences. Time-dependent simulations of the integrated FO-MD system showed that MD regeneration reduces draw solution dilution by 60% compared to standalone FO, maintaining FO flux approximately 43% higher after 6 h of operation. Sensitivity analysis revealed that FO predictions are moderately sensitive to mass transfer coefficients (6–9% flux change for 20% parameter variation), while MD shows lower sensitivity to heat transfer coefficients (3–5%). Energy analysis indicates that FO-MD hybridization reduces thermal energy consumption by 15–40% compared to standalone MD, with specific energy consumption of 382 kWh/m³ (40.2 kWh/m³ primary energy equivalent) when using low-grade heat. The obtained results demonstrate that FO-MD hybridization enhances water recovery and operational stability compared to standalone processes, supporting its potential for energy-efficient desalination of high-salinity brines and industrial wastewaters where low-grade heat is available. Full article

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15 pages, 1860 KB

Open AccessArticle

Effect of Glass Fibers on the Mechanical and Transport Properties of Polymer Inclusion Membranes Composed of Aliquat 336 and PVDF-HFP

by Lea Kukoc, Kalina Velikova, Sanja Perinovic-Jozic, Maja Biocic, Milen Gateshki, Spas D. Kolev and Tony G. Spassov

Membranes 2026, 16(4), 141; https://doi.org/10.3390/membranes16040141 - 1 Apr 2026

Abstract

Polymer inclusion membranes (PIMs) based on PVDF-HFP as the base polymer and Aliquat 336 as the carrier in a mass ratio of 6:4 with concentrations of embedded glass fibers up to 5 wt% were successfully fabricated. Their microstructure, as well as their mechanical [...] Read more.

Polymer inclusion membranes (PIMs) based on PVDF-HFP as the base polymer and Aliquat 336 as the carrier in a mass ratio of 6:4 with concentrations of embedded glass fibers up to 5 wt% were successfully fabricated. Their microstructure, as well as their mechanical and thermal properties, were characterized using scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), differential thermal analysis/thermogravimetric analysis (DTA/TGA), and tensile testing. Membrane performance and long-term stability in transporting thiocyanate ions were evaluated in a two-compartment transport cell. The results showed that the membranes retained their amorphous structure even with glass-fiber loadings of up to 5 wt%. The addition of glass fibers was found to primarily enhance the elastic modulus and tensile strength, while causing a moderate reduction in plasticity without negatively affecting membrane transport properties and long-term stability. Therefore, it was concluded that the incorporation of glass fibers could improve the suitability of PIMs for industrial applications. Full article

(This article belongs to the Special Issue Functionalized Membranes: New Trends in Preparation and Advanced Applications)

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13 pages, 21937 KB

Open AccessArticle

Hydrophobic Capillary Ceramic-Membrane Contactor for Recovering Ammonia from Sludge Hydrolysate

by Shiji Sun, Mengfei Liu, Dawei Gong, Kaiyun Fu, Xianfu Chen, Minghui Qiu and Ping Luo

Membranes 2026, 16(4), 140; https://doi.org/10.3390/membranes16040140 - 1 Apr 2026

Abstract

Efficient recovery of ammonia from sludge hydrolysate (SH) remains a challenging task. This study developed a superhydrophobic capillary ceramic-membrane contactors (MCs), which, by establishing a stable gas-phase mass transfer interface, provides a reliable guarantee for ammonia recovery under high-temperature, high-pH, and high-organic-load conditions. [...] Read more.

Efficient recovery of ammonia from sludge hydrolysate (SH) remains a challenging task. This study developed a superhydrophobic capillary ceramic-membrane contactors (MCs), which, by establishing a stable gas-phase mass transfer interface, provides a reliable guarantee for ammonia recovery under high-temperature, high-pH, and high-organic-load conditions. In a controllable simulation system, the system investigated the effects of key operational parameters such as pH, flow rate, and feed ammonia concentration on ammonia mass transfer behavior, and verified the feasibility of this MCs in efficient ammonia removal. Then, this membrane contactor was applied to the actual sludge hydrolysate (SH) system, and its anti-pollution effects, wetting stability, and adaptability to fluctuating conditions under long-term continuous operation were evaluated. The results showed that after operating for 10 h, the ammonia removal in the simulation system and the actual system reached 93.6% and 90.3%, respectively. During long-term operation, the ammonia recovery reached 90.3%. Meanwhile, the organic matter in SH was completely retained, and (NH₄)₂SO₄ was not contaminated by organic matter. Throughout the entire operation process, the contact angle of the membrane remained above 129.6°. This study provides a theoretical basis and practical reference for recovering ammonia using a hydrophobic capillary ceramic-membrane contactor in SH. Full article

(This article belongs to the Special Issue New Trends in Membrane Technologies for Removal of Hazardous Pollutants)

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34 pages, 8380 KB

Open AccessReview

Advances and Challenges in Aerobic Granular Sludge Membrane Bioreactors for Treating Sulfamethoxazole in Wastewater

by Qingyu Zhang, Bingjie Yan, Xinhao Sun, Zhengda Lin, Lu Liu, Haijuan Guo and Fang Ma

Membranes 2026, 16(4), 139; https://doi.org/10.3390/membranes16040139 - 1 Apr 2026

Abstract

Sulfamethoxazole (SMX) is one of the most frequently detected antibiotics in aquatic environments and is difficult to remove by conventional biological treatment because of its persistence, potential toxicity to microbial communities, and associated risk of antibiotic resistance selection. Aerobic granular sludge membrane bioreactors [...] Read more.

Sulfamethoxazole (SMX) is one of the most frequently detected antibiotics in aquatic environments and is difficult to remove by conventional biological treatment because of its persistence, potential toxicity to microbial communities, and associated risk of antibiotic resistance selection. Aerobic granular sludge membrane bioreactors (AGMBRs), which combine the compact and stratified structure of aerobic granular sludge with membrane-based solid–liquid separation, have emerged as a promising platform for SMX-contaminated wastewater treatment because they provide high biomass retention, decoupled sludge retention time (SRT) and hydraulic retention time (HRT), and stable effluent quality. This review systematically summarizes recent advances in AGMBRs for SMX removal, with emphasis on how operating parameters (e.g., dissolved oxygen, hydraulic retention time, organic loading rate, C/N ratio, and sludge retention time) and membrane-related factors (e.g., membrane flux, aeration-induced shear, membrane type, and pore size) affect treatment performance and process stability. The main SMX attenuation pathways in AGMBRs are discussed from three perspectives: sorption and partitioning within granules and extracellular polymeric substances (EPSs), microbial biodegradation and co-metabolism, and membrane retention that prolongs effective contact time and shapes microbial ecology. Particular attention is given to the dual role of EPS and soluble microbial products (SMPs), which contribute to granule stability and SMX tolerance but also accelerate membrane fouling through cake-layer formation, pore blocking, and transmembrane pressure increase. Current challenges include incomplete understanding of transformation products, ARG- and MGE-related risks, long-term fouling–biodegradation interactions, and the lack of pilot-scale validation. Future research should therefore focus on mechanism clarification, integrated control of removal and fouling, energy-efficient operation, and scale-up of AGMBRs for practical antibiotic wastewater treatment. Full article

(This article belongs to the Special Issue Membrane Materials for Gas Separation and Wastewater Treatment: Design, Performance and Application)

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24 pages, 6362 KB

Open AccessArticle

Effects of Alkaline Cleaning Agents on the Filtration Performance and Aging of Polyvinylidene Fluoride Membranes

by Marek Gryta and Piotr Woźniak

Membranes 2026, 16(4), 138; https://doi.org/10.3390/membranes16040138 - 1 Apr 2026

Abstract

Polyvinylidene fluoride (PVDF) membranes are used in ultrafiltration systems for car wash water reuse, where frequent alkaline cleaning is required to maintain operational flux rates. Although NaOH-induced degradation of virgin PVDF membranes has been reported, its relevance under real industrial conditions remains poorly [...] Read more.

Polyvinylidene fluoride (PVDF) membranes are used in ultrafiltration systems for car wash water reuse, where frequent alkaline cleaning is required to maintain operational flux rates. Although NaOH-induced degradation of virgin PVDF membranes has been reported, its relevance under real industrial conditions remains poorly understood. This study investigates the long-term exposure of tubular PVDF membranes to alkaline car wash detergents and evaluates how the resulting structural changes influence permeate quality. During several months of pilot-scale operation with synthetic car wash wastewater and daily alkaline cleaning (pH > 11.5), permeate fluxes remained stable at 50–70 LMH despite pronounced membrane aging. Structural analyses revealed enlarged pore size, increased water permeability and reduced dextran retention, while FTIR confirmed dehydrofluorination of the polymer matrix. Despite the extensive degradation of the membrane skin layer, permeate turbidity, dissolved organic carbon, and surfactant concentrations remained stable throughout the operation. This stability was attributed to the persistent fouling layer, which acted as an effective secondary separation barrier and compensated for the loss of intrinsic membrane selectivity. These findings demonstrate that substantial PVDF degradation does not necessarily compromise permeate quality in car wash ultrafiltration systems, highlighting the dominant role of fouling-controlled separation under long-term alkaline cleaning regimes. Full article

(This article belongs to the Special Issue Recent Advances in Polymeric Membranes—Preparation and Applications (2nd Edition))

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18 pages, 2382 KB

Open AccessArticle

Curcumin–Lipid Interactions in PEGylated vs. Conventional Liposomes: A Combined Fluorescence and EPR Study

by Namra Fatima, Andrzej Górecki and Anna Wiśniewska-Becker

Membranes 2026, 16(4), 137; https://doi.org/10.3390/membranes16040137 - 1 Apr 2026

Abstract

Curcumin, a natural polyphenol derived from Curcuma longa, is widely recognized for its therapeutic properties. However, its clinical utility is limited because of poor solubility, rapid degradation and hence low bioavailability. To overcome these issues, nanoformulation approaches, especially PEGylated liposomes, have been explored [...] Read more.

Curcumin, a natural polyphenol derived from Curcuma longa, is widely recognized for its therapeutic properties. However, its clinical utility is limited because of poor solubility, rapid degradation and hence low bioavailability. To overcome these issues, nanoformulation approaches, especially PEGylated liposomes, have been explored as advanced delivery systems. PEGylation, which involves attaching polyethylene glycol (PEG) to the liposomal surface, enhances circulation time by creating a steric shield that reduces protein interactions and clearance by the mononuclear phagocyte system (MPS). However, PEG can alter lipid membrane properties, which may in turn affect curcumin’s solubility and distribution within the liposomal bilayer, ultimately reducing its loading efficiency. To ensure that PEG-modified liposomes can be effectively loaded with curcumin, we investigated curcumin–membrane interactions in saturated (DMPC) and unsaturated (POPC) liposomes, both in the presence and absence of PEG. Based on dissociation constants (K_d) obtained from fluorescence spectroscopy measurements, we found that PEGylated DMPC liposomes exhibit the strongest binding affinity for curcumin. Fluorescence quenching experiments showed that curcumin adopts a transbilayer orientation in all membranes examined. Curcumin’s location within PEGylated and non-PEGylated liposomal membranes was further confirmed by examining its effects on membrane properties, including fluidity, polarity, and oxygen transport. These effects were investigated using electron paramagnetic resonance (EPR) spectroscopy with spin labels. The results indicate that PEG does not impose major changes on membrane properties. Curcumin, however, was found to reinforce the liposomal membranes, increase their polarity, and reduce oxygen availability. Overall, the findings suggest that liposomes, particularly those composed of PEGylated DMPC, are effective vehicles for curcumin delivery. Full article

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17 pages, 566 KB

Open AccessArticle

Life Cycle Assessment of Microplastic Fouling Mitigation Strategies in Membrane Filtration

by Rendra Hakim Hafyan, Vithushan Indrakumar, Judy Lee and Siddharth Gadkari

Membranes 2026, 16(4), 136; https://doi.org/10.3390/membranes16040136 - 1 Apr 2026

Abstract

While membrane technologies are critical for preventing microplastics (MPs) release into aquatic ecosystems, MPs-induced fouling remains a persistent bottleneck, necessitating energy-intensive cleaning strategies that introduce their own environmental burdens. This study presents a systematic life cycle assessment (LCA) of fouling mitigation strategies, rigorously [...] Read more.

While membrane technologies are critical for preventing microplastics (MPs) release into aquatic ecosystems, MPs-induced fouling remains a persistent bottleneck, necessitating energy-intensive cleaning strategies that introduce their own environmental burdens. This study presents a systematic life cycle assessment (LCA) of fouling mitigation strategies, rigorously comparing hydraulic forward flushing and nitrogen (N₂) gas scouring across both unmodified and plasma-modified (acrylic acid, cyclopropylamine, and hexamethyldisiloxane) polysulfone membranes. Results reveal a stark divergence between operational performance and environmental sustainability. Baseline operations and the hydraulic flushing of unmodified membranes have environmentally costly global warming potential (GWP) ~150 kg CO₂-eq/m³), driven primarily by high electricity consumption and frequent membrane replacement. Conversely, cyclopropylamine (CPAm) plasma-modified membranes emerging as the optimal strategy, reducing global warming potential to 68 kg CO₂-eq/m³ and cutting electricity demand by 44% through superior fouling resistance. Crucially, the study uncovers a significant trade-off regarding gas scouring: While it achieves the highest technical performance (minimal flux decline of 0.33% h⁻¹), the upstream burdens of N₂ supply increased environmental impacts by over 100% across all categories. These findings challenge the assumption that maximum fouling control equates to sustainability, suggesting that surface engineering via plasma modification, rather than aggressive physical cleaning, offers the most viable pathway for sustainable MPs remediation. Full article

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20 pages, 7533 KB

Open AccessArticle

A Novel Supported Polymer Inclusion Membrane Concept for Reagent-Efficient Membrane Design

by Nasim Khatir, Enriqueta Anticó and Clàudia Fontàs

Membranes 2026, 16(4), 135; https://doi.org/10.3390/membranes16040135 - 1 Apr 2026

Abstract

This work explores, for the first time, a novel strategy for the preparation of polymer inclusion membranes (PIMs) based on their deposition onto porous supporting substrates, introducing the concept of supported PIMs as a reagent-efficient alternative to conventional free-standing membranes. The approach aims [...] Read more.

This work explores, for the first time, a novel strategy for the preparation of polymer inclusion membranes (PIMs) based on their deposition onto porous supporting substrates, introducing the concept of supported PIMs as a reagent-efficient alternative to conventional free-standing membranes. The approach aims to improve the sustainability of PIM fabrication by significantly reducing the amount of polymer and extractant required while preserving membrane functionality. PIMs were prepared using the two most widely employed base polymers, cellulose triacetate (CTA) and poly(vinyl chloride) (PVC), with Aliquat 336 as extractant. The total reagent consumption was reduced to half of the conventional formulation for CTA-based membranes and to one quarter for PVC-based membranes. Two porous supports with contrasting physicochemical properties—a hydrophilic cellulose filter paper and a hydrophobic Durapore^® PVDF membrane—were investigated. The supported membranes were characterized by contact angle measurements, SEM, FTIR, and TGA, confirming the successful integration of the PIM phase onto the porous supports without chemical alteration. Arsenate (As(V)) transport, preconcentration, and membrane reusability were evaluated. CTA-based supported PIMs exhibited transport efficiencies of approximately 90–95%, comparable to free-standing PIMs, whereas PVC-based systems showed a stronger dependence on membrane loading. Notably, CTA-based Durapore^®–PIMs retained around 70% transport efficiency after three reuse cycles. These results demonstrate the feasibility of supported PIMs as a strategy for reducing membrane material consumption while preserving functional performance. Full article

(This article belongs to the Special Issue Functionalized Membranes: New Trends in Preparation and Advanced Applications)

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40 pages, 13676 KB

Open AccessReview

Interfacial Interactions of Nanoparticles and Molecular Nanostructures with Model Membrane Systems: Mechanisms, Methods, and Applications

by Konstantin Balashev

Membranes 2026, 16(4), 134; https://doi.org/10.3390/membranes16040134 - 1 Apr 2026

Abstract

This review surveys how nanoparticles and biomolecular nanosized structures interact with model membrane systems, and how these interfacial processes govern their performance in drug and gene delivery, antimicrobial strategies, biosensing, and nanotoxicology. The nanostructures covered include polymeric nanoparticles, lipid-based carriers, peptide nanostructures, dendrimers, [...] Read more.

This review surveys how nanoparticles and biomolecular nanosized structures interact with model membrane systems, and how these interfacial processes govern their performance in drug and gene delivery, antimicrobial strategies, biosensing, and nanotoxicology. The nanostructures covered include polymeric nanoparticles, lipid-based carriers, peptide nanostructures, dendrimers, and multifunctional hybrids. Model membranes span Langmuir monolayers, supported lipid bilayers, vesicles/liposomes across sizes, and emerging hybrid or asymmetric constructs that better approximate native complexity. Mechanistically, interactions follow recurrent routes—surface adsorption, bilayer insertion, pore formation, and lipid extraction/reorganization—regulated by particle size, morphology, charge, ligand architecture, and lipophilicity, in conjunction with membrane composition, phase state, curvature, and asymmetry. A multiscale toolkit links structure, mechanics, and dynamics: Langmuir troughs and Brewster Angle Microscopy map thermodynamics and mesoscale morphology; atomic force microscopy and quartz crystal microbalance with dissipation resolve nanoscale topography and viscoelasticity; fluorescence microscopy/spectroscopy reports on localization and packing; neutron and X-ray reflectometry quantify vertical structure; molecular dynamics provides atomistic pathways and design hypotheses. Historically, the field advanced from early monolayers and bilayers, through the fluid mosaic model, to raft microdomains and modern biomimetic systems, enabling increasingly realistic experiments. Key advances include cross-method integration linking experimental observations with image-based computational models; persistent debates concern the translation from simplified models to living membranes, the role of dynamic coronas, and scale/force-field limits in simulations. Future efforts should prioritize hybrid models incorporating proteins and asymmetric lipidomes, standardized reporting and reference systems, rigorous coupling of experiments with calibrated simulations and machine learning, and alignment with safety-by-design and regulatory expectations, thereby shifting interfacial measurements from descriptive observation to predictive design rules. Full article

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

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18 pages, 3676 KB

Open AccessArticle

Tailoring Copper Pillars to Prevent Physical Aging in Matrimid^® 5218 Carbon Molecular Sieve Membranes

by Whitney K. Cosey, Edson V. Perez, Kenneth J. Balkus, Jr., John P. Ferraris and Inga H. Musselman

Membranes 2026, 16(4), 133; https://doi.org/10.3390/membranes16040133 - 1 Apr 2026

Abstract

Carbon molecular sieve membranes (CMSMs) provide a means to greatly improve gas separations. CMSMs have a pore size distribution comprising micropores and ultramicropores which provide high flux and high selectivity, enabling them to outperform polymeric membranes. CMSMs, however, suffer from physical aging that [...] Read more.

Carbon molecular sieve membranes (CMSMs) provide a means to greatly improve gas separations. CMSMs have a pore size distribution comprising micropores and ultramicropores which provide high flux and high selectivity, enabling them to outperform polymeric membranes. CMSMs, however, suffer from physical aging that results from the collapse of the pores that severely reduces their gas permeability. Therefore, reducing physical aging of CMSMs is an important step in the development of these types of materials. In this work, a method for reducing physical aging through the incorporation of metal nanoparticles that serve as a structural scaffold for the membrane pore structure is presented. The pore structure in CMSMs is dependent upon the polymeric precursor, and thus the support system incorporated must be tailored. The copper nanoparticles were formed in situ from soluble, copper-based metal–organic polyhedra 18 (MOP-18) dispersed into Matrimid^® 5218, a low free volume polymer. The size (2 to 20 nm) and shape (sphere, rods) of the copper particles were refined by adjusting MOP-18 loading, pyrolysis temperature, and soaking time. The Cu-pillared Matrimid^® 5218 CMSMs from this work showed no decline in permeability or selectivity for methane (107 Barrer) and carbon dioxide (1785 Barrer) over a period of 21 d. The results suggest that tailored metal pillars can suppress physical aging in CMSMs, thereby enhancing their long-term stability and applicability in gas separations. Full article

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

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20 pages, 2526 KB

Open AccessArticle

Microalgae Harvesting Using Ceramic Membranes: Semi-Industrial Scale Study

by Stacy Ragueneau, Clémence Cordier, Adeline Lange, Laurent Torres and Philippe Moulin

Membranes 2026, 16(4), 132; https://doi.org/10.3390/membranes16040132 - 1 Apr 2026

Abstract

Microalgae, being able to produce a variety of bioactive compounds, represent a promising resource for numerous industrial applications. However, their large-scale production remains constrained by biological, technical and economic factors. Open ponds, which are predominantly employed on an industrial scale, yield lower levels [...] Read more.

Microalgae, being able to produce a variety of bioactive compounds, represent a promising resource for numerous industrial applications. However, their large-scale production remains constrained by biological, technical and economic factors. Open ponds, which are predominantly employed on an industrial scale, yield lower levels of algae in comparison to those obtained in closed reactors. Consequently, the processing of substantial volumes is necessitated during the harvesting process. This study explores the potential of microfiltration as an alternative to conventional harvesting processes to optimise yields and preserve biomass quality. The evaluation of various ceramic membranes, including new-generation prototypes, was conducted according to several operating parameters (flux, backwash mode, recirculation rate). The objective was to obtain microalgae concentrate while preserving cell integrity. Three species (Odontella aurita, Phaeodactylum tricornutum and Dunaliella salina) were considered for issues directly related to industrial cultivation such as seasonality, strain variability and the state of the culture at the time of harvest. An effective cleaning protocol was also developed, applicable to all the conditions tested. The ceramic membranes demonstrated a high degree of resistance to fouling, with their low tortuosity promoting effective backwashing. The membrane process resulted in a high level of cell recovery and volume concentration factors that were comparable to those achieved by conventional methods. In comparison with alternative concentration processes, it is also economically viable, thus confirming its potential as a robust and efficient alternative for industrial-scale microalgae harvesting. Full article

(This article belongs to the Special Issue Membranes Processes for Marine Environment)

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16 pages, 1622 KB

Open AccessReview

Mini Review on Nanomaterial-Driven Substrate Optimization of Polyamide Thin-Film Nanocomposite Membranes for FO, RO and NF Applications

by Shabin Mohammed, Ahmed Elmekawy, Ranwen Ou and Hanaa M. Hegab

Membranes 2026, 16(4), 131; https://doi.org/10.3390/membranes16040131 - 31 Mar 2026

Abstract

The rising demand for clean water has reinforced the importance of thin-film composite TFC polyamide membranes in desalination and wastewater treatment. While improvements often target the selective layer, these can sometimes reduce stability or selectivity. An alternative approach is to tailor the porous [...] Read more.

The rising demand for clean water has reinforced the importance of thin-film composite TFC polyamide membranes in desalination and wastewater treatment. While improvements often target the selective layer, these can sometimes reduce stability or selectivity. An alternative approach is to tailor the porous support, particularly through the incorporation of nanomaterials such as metal oxides, carbon-based nanomaterials, metal–organic frameworks (MOFs), zeolites, and cellulose-based materials, to improve overall membrane performance. The modification of membrane substrates through the incorporation of nanofillers has demonstrated notable advantages, including enhanced hydrophilicity, improved mechanical stability, and increased porosity. These improvements collectively contribute to higher permeability, reduced internal concentration polarization and enhanced separation performance in FO, NF, and RO applications. The review starts by clearly distinguishing substrate modification, in which nanomaterials are localized in the porous support, from interlayer modification, which involves constructing a distinct layer between the support and selective layer. This concise review highlights current developments in the nanomaterial-based support modification of polyamide TFC membranes; it summarizes nanomaterials selections, incorporation techniques, and resulting property changes. Current challenges and potential research opportunities are also discussed. Full article

(This article belongs to the Special Issue Advances in Modified Thin-Film Composite (TFC) Membranes: Innovations in Selective, Intermediate, and Support Structures)

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15 pages, 2559 KB

Open AccessArticle

Charge-Tunable Polyelectrolytes Enable High-Performance Layer-by-Layer Nanofiltration Membranes for Heavy Metal Ion Removal

by Fei Jiang, Wenyan Huang and Yifang Mi

Membranes 2026, 16(4), 130; https://doi.org/10.3390/membranes16040130 - 31 Mar 2026

Abstract

Wastewater contamination by toxic heavy metal ions poses a huge threat to ecosystem integrity and human health. Herein, we designed a polyelectrolyte (T-PEI) with a tunable positive charge property to construct a layer-by-layer (LBL) nanofiltration membrane for efficient heavy metal ion removal. The [...] Read more.

Wastewater contamination by toxic heavy metal ions poses a huge threat to ecosystem integrity and human health. Herein, we designed a polyelectrolyte (T-PEI) with a tunable positive charge property to construct a layer-by-layer (LBL) nanofiltration membrane for efficient heavy metal ion removal. The T-PEI was obtained via a Mannich reaction between polyethyleneimine (PEI) and tetrakis (hydroxymethyl) phosphonium chloride (THPC). The introduction of THPC imparted T-PEI with a strong and tunable positive charge, attributed to the quaternary phosphonium groups in THPC. Converting the weakly charged PEI into the strongly charged T-PEI allowed regulation of both T-PEI’s deposition behavior and the electrostatic interactions with sodium polystyrenesulfonate (PSS) during LBL assembly. As a result, after depositing only one bilayer, the positively charged PSS/T-PEI membrane achieved a pore size radius of 0.35 nm, meeting the typical criteria for nanofiltration membranes. Under the optimal preparation conditions, the resultant membranes exhibited a water flux of 38.1 L m⁻² h⁻¹ and high rejections to various heavy metal ions at low operation pressure, such as Cr³⁺ (99.8%), Ni²⁺ (96.1%), Cu²⁺ (92.5%), and Mn²⁺ (90.3%). Additionally, the membrane possessed robust operation stability, along with excellent antifouling/bacterial performance. After cyclic filtration of a lysozyme solution, the flux recovery ratio reached 94.7%. The membrane also exhibited effective bactericidal activity against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), with no visible microbial colonies observed. This work highlights the effectiveness of tailoring polyelectrolyte characteristics in enhancing the LBL membrane performance and presents a promising LBL nanofiltration membrane for heavy metal ion removal. Full article

(This article belongs to the Topic Sustainable Development of Clean Water and Sanitation)

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16 pages, 4897 KB

Open AccessArticle

Enhanced Properties of Collagen Nanofiber Scaffolds via Chitosan/Polypyrrole/Glutaraldehyde Double-Crosslinking

by Tonantzi Pérez-Moreno, Jesús Humberto Chávez-Meza, Jesús-Salvador Jaime-Ferrer, Gabriel Luna-Bárcenas, Luis G. Arriaga and Janet Ledesma-García

Membranes 2026, 16(4), 129; https://doi.org/10.3390/membranes16040129 - 31 Mar 2026

Abstract

To enhance the functionality of collagen (Coll)-based scaffolds, we developed a double-crosslinking strategy incorporating an electroconductive chitosan (Ch) and polypyrrole (Ppy) composite. Successful pre-crosslinking of Ch and Ppy was achieved using glutaraldehyde (GTA) at 100 µM. This facilitated imine linkage formation, confirmed by [...] Read more.

To enhance the functionality of collagen (Coll)-based scaffolds, we developed a double-crosslinking strategy incorporating an electroconductive chitosan (Ch) and polypyrrole (Ppy) composite. Successful pre-crosslinking of Ch and Ppy was achieved using glutaraldehyde (GTA) at 100 µM. This facilitated imine linkage formation, confirmed by FTIR, enabling synergistic integration with Coll and successful nanofiber scaffold fabrication via electrospinning. While increasing the Ch-Ppy-GTA ratio affected the spinning process and higher GTA concentrations compromised fiber homogeneity, all other measured properties generally improved with increasing ratios. Crucially, this methodology allowed the membranes to maintain their morphology and significantly extended their degradation profile up to 20–30 days in PBS medium at 37 °C. Furthermore, the scaffolds exhibited electroactivity characterized by pseudocapacitance in the presence of Na⁺ and Ca²⁺ ions. These findings demonstrate a robust, tunable method for creating electroactive and structurally stable nanofiber scaffolds suitable for advanced tissue engineering. Full article

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

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15 pages, 2714 KB

Open AccessArticle

SPPSU/SPES Membranes Reinforced with Electrospun PPSU Mats and Sulfone-Crosslinked: Toward Fluorine-Free Proton Exchange Materials

by Luca Pasquini, Murli Manohar, Riccardo Narducci, Emanuela Sgreccia, Maria Luisa Di Vona and Philippe Knauth

Membranes 2026, 16(4), 128; https://doi.org/10.3390/membranes16040128 - 31 Mar 2026

Abstract

Sulfonated aromatic polymers (SAPs) represent promising alternatives to perfluorinated ionomers for proton-exchange membrane fuel cells (PEMFCs), but their high hydrophilicity and limited chemical stability often require structural reinforcement and controlled cross-linking. In this study, composite membranes based on sulfonated poly(phenylsulfone) (SPPSU) and sulfonated [...] Read more.

Sulfonated aromatic polymers (SAPs) represent promising alternatives to perfluorinated ionomers for proton-exchange membrane fuel cells (PEMFCs), but their high hydrophilicity and limited chemical stability often require structural reinforcement and controlled cross-linking. In this study, composite membranes based on sulfonated poly(phenylsulfone) (SPPSU) and sulfonated poly(ethersulfone) (SPES) were fabricated with and without electrospun PPSU nanofiber mats and subsequently cross-linked through a solvent-induced sulfone-bridge formation at 180 °C. SPPSU/SPES blends (70/30, 50/50, 30/70) displayed good miscibility, while PPSU fibers improved dimensional stability and suppressed excessive swelling. Cross-linking strongly influenced membrane properties: intermediate treatment (20 h) enhanced mechanical strength and solvent resistance with limited loss of IEC, whereas extended treatment (30 h) produced highly stable, low-swelling networks. Despite lower IEC and water uptake, 30 h-treated membranes exhibited higher proton conductivity, attributed to reduced tortuosity and more continuous ionic pathways. Mechanical and hydration analyses identified SPPSU-50, SPPSU-70, and SPPSU-100 as the most balanced compositions. Proton mobility analysis revealed high membrane tortuosity, consistent with dense cross-linked structures reinforced by fibers. Overall, the combined use of SPPSU/SPES blending, PPSU nanofiber reinforcement, and sulfone-bridge cross-linking yields robust, water-insoluble membranes with improved electrochemical performance suitable for PEMFCs and other applications. Full article

(This article belongs to the Collection Feature Papers in Membrane Chemistry)

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20 pages, 1163 KB

Open AccessArticle

Optimal Operation for Electricity–Hydrogen Integrated Energy System Accounting for Dynamic Traits of Proton Exchange Membrane Electrolyzer

by Chengbo Mao, Chaoping Rao, Jitao Liang, Jiahao Wang, Peirong Ji and Yi Zheng

Membranes 2026, 16(4), 127; https://doi.org/10.3390/membranes16040127 - 31 Mar 2026

Abstract

The proton exchange membrane (PEM) electrolyzer is vital for converting surplus renewable energy (RE) into hydrogen, underpinning the efficient and stable operation of the electric–hydrogen system. However, frequent start–stop cycles and load variations accelerate the degradation of proton exchange membranes and catalyst layers, [...] Read more.

The proton exchange membrane (PEM) electrolyzer is vital for converting surplus renewable energy (RE) into hydrogen, underpinning the efficient and stable operation of the electric–hydrogen system. However, frequent start–stop cycles and load variations accelerate the degradation of proton exchange membranes and catalyst layers, incurring significant lifetime costs that existing studies ignore. To explore how the PEM electrolyzer’s dynamic traits impact system performance, we introduce an optimized operation approach for the electricity–hydrogen integrated energy system (IES) that incorporates these dynamic features and the novel Loss of Life Cost (LLC) model. Initially, to rectify the inadequacy in modeling the PEM electrolyzer within the current electricity–hydrogen IES operational framework, we integrate its dynamic characteristics based on electrochemical properties and establish a quantitative relationship between operational cycles and degradation costs. This enhanced model accurately reflects how operational conditions affect the electrolyzer’s hydrogen production efficiency and lifetime consumption, enabling precise performance simulation and economic assessment. This, in turn, promotes high-quality renewable energy utilization via hydrogen production while ensuring asset longevity, meeting the rising demand for hydrogen energy applications. Building on this, we further factor in constraints related to diverse energy conversion and safe operation within the electricity–hydrogen IES, as well as the operational limits of hydrogen fuel cells, various energy storage (ES) options, cogeneration units, and other pertinent equipment, aiming to minimize the system’s total daily costs (operational plus degradation costs). Consequently, we develop an optimization operation model for the electricity–hydrogen IES that accounts for the PEM electrolyzer’s dynamic characteristics and degradation economics. Finally, through simulation examples validated against published experimental data, we comprehensively analyze how the PEM electrolyzer’s dynamic traits influence system operation, confirming the effectiveness of our proposed model and methodology. Simulation findings reveal that, under varying electrolyzer capacities, ignoring the PEM electrolyzer’s dynamic characteristics can result in a deviation in system operating. Compared with the proposed method, it can reduce the equipment degradation speed by a maximum of 5.78 times. Full article

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

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27 pages, 2000 KB

Open AccessReview

Recent Advances in Polymer of Intrinsic Microporosity (PIM) Membranes for Ion Separation Applications

by Cuijing Liu, Jingyi Xu and Linbo Li

Membranes 2026, 16(4), 126; https://doi.org/10.3390/membranes16040126 - 31 Mar 2026

Abstract

Polymers of intrinsic microporosity (PIMs) represent a novel class of microporous materials tailored for membrane separation. Initially explored predominantly for gas separation, they have subsequently found widespread utility in organic solvent nanofiltration. In recent years, their applicability has been further extended to ion [...] Read more.

Polymers of intrinsic microporosity (PIMs) represent a novel class of microporous materials tailored for membrane separation. Initially explored predominantly for gas separation, they have subsequently found widespread utility in organic solvent nanofiltration. In recent years, their applicability has been further extended to ion separation. However, few comprehensive reviews have been dedicated to summarizing the advances of PIMs in this burgeoning field to date. This review provides a systematic overview of the recent progress in PIM membranes for ion separation. First, the structural features of PIMs employed in ion separation are summarized, with an emphasis on structure–performance correlations. Subsequently, their diverse applications in ion separation are elaborated in detail, encompassing ion resource recovery, water treatment, and electrochemical energy storage systems. Next, the current challenges facing the application of PIMs in ion separation are outlined, and finally, conclusions are provided. This review aims to provide insightful guidance for the development of high-performance PIM-based membranes in this rapidly evolving research area. Full article

(This article belongs to the Special Issue Current Studies in Functionalized Ion Separation Membrane Materials)

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28 pages, 759 KB

Open AccessReview

Advanced Membrane Technologies and Hybrid Treatment Systems for Sustainable Removal of Naturally Occurring Radioactive Materials from Industrial Wastewater

by Amal S. Al Saadi, Ismail Al-Yahmadi, Sharif H. Zein, Natarajan Rajamohan, Intisar K. Al-Busaidi, Nabila Al-Rashdi, Safa Al Habsi, Saada Al Shukaili, Ali Alawi and Rashid Al Mashrafi

Membranes 2026, 16(4), 125; https://doi.org/10.3390/membranes16040125 - 31 Mar 2026

Abstract

Naturally Occurring Radioactive Materials (NORMs) in industrial wastewater present significant environmental and public health challenges due to their persistence and radiotoxic effects. This comprehensive review analyzes 108 peer-reviewed publications from 2014 to 2025 on NORM treatment technologies for industrial wastewater. While previous reviews [...] Read more.

Naturally Occurring Radioactive Materials (NORMs) in industrial wastewater present significant environmental and public health challenges due to their persistence and radiotoxic effects. This comprehensive review analyzes 108 peer-reviewed publications from 2014 to 2025 on NORM treatment technologies for industrial wastewater. While previous reviews have focused on individual treatment methods or laboratory-scale studies, this work provides comparative performance analysis across multiple technologies under realistic industrial conditions, including high-salinity environments and competing ions. We emphasize membrane filtration, electrocoagulation (EC), ion exchange, and advanced oxidation processes, evaluating both their economic feasibility and environmental sustainability for practical industrial implementation. The review discusses the advantages and limitations of existing techniques, highlighting the need for integrated strategies that combine physical, chemical, and biological processes for enhanced remediation. Hybrid systems combining multiple technologies outperform individual approaches by 15–25% in removal efficiency. These advances are critical for ensuring safe water reuse and protecting water resources from radioactive contamination. Additionally, regulatory frameworks governing NORM management are examined, underscoring the importance of standardized disposal and treatment protocols. The review concludes by identifying research gaps and future directions. Priority areas include developing standardized treatment protocols and strengthening academia–industry collaboration to achieve scalable solutions aligned with UN Sustainable Development Goal 6. Full article

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