Membranes

19 pages, 10490 KB

Open AccessArticle

Promotion Effect of Steam on Hydrogen and Oxygen Separation in Electrochemical Membrane Reactor: Investigation Under the Aromatization Reaction Temperature Window

by Lihui Wang, Shao Zhang, Mingming Wang, Zhigang Wang and Xiaoyao Tan

Membranes 2026, 16(8), 260; https://doi.org/10.3390/membranes16080260 - 31 Jul 2026

Abstract

Methane aromatization mainly proceeds at 650–750 °C. Simultaneous separation of hydrogen and oxygen can boost conversion efficiency and mitigate catalyst coking, yet most non-electrochemical membrane reactors fail to achieve synchronous hydrogen–oxygen separation within this temperature range. Accordingly, an electrochemical membrane reactor is adopted [...] Read more.

Methane aromatization mainly proceeds at 650–750 °C. Simultaneous separation of hydrogen and oxygen can boost conversion efficiency and mitigate catalyst coking, yet most non-electrochemical membrane reactors fail to achieve synchronous hydrogen–oxygen separation within this temperature range. Accordingly, an electrochemical membrane reactor is adopted in this work, and steam is introduced to improve gas separation efficiency. BZCY hollow fiber membranes with mixed proton and oxygen ion conductivity are selected as the research material, and the influences of three distinct steam feeding modes (anode side only, cathode side only, simultaneous feeding on both sides) on H₂ and O₂ permeation and separation are systematically investigated. Experimental results reveal that steam humidification significantly enhances the permeation fluxes of hydrogen and oxygen. Notably, such promotional effect strongly depends on the steam feeding location. At 700 °C and 1.5 V, the hydrogen permeation flux increases to 1.469 mL⋅min⁻¹⋅cm⁻², in sharp contrast to 0.189 mL⋅min⁻¹⋅cm⁻² under dry atmosphere. Meanwhile, the oxygen permeation flux reaches 0.824 mL⋅min⁻¹⋅cm⁻² at 700 °C with steam, which is approximately four times that under dry conditions. This study verifies the intrinsic H₂ and O₂ permeation capability of electrochemical membrane reactors and the remarkable promotion effect originating from steam, facilitating further practical applications of such membrane reactors in methane aromatization. Full article

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

► Show Figures

Figure 1

19 pages, 1775 KB

Open AccessArticle

Numerical Study of Concentration Polarization in Electrodialysis for High-Salinity Solution Concentration in Air-Conditioning Systems

by Bo Sun and Ning Lyu

Membranes 2026, 16(8), 259; https://doi.org/10.3390/membranes16080259 - 29 Jul 2026

Abstract

Concentration polarization is a common phenomenon in membrane separation processes and generally impairs mass transfer efficiency. Electrodialysis (ED) is considered a promising technology for concentrating high-salinity solutions used in air-conditioning systems; however, concentration polarization under high-concentration operating conditions remains insufficiently understood. In this [...] Read more.

Concentration polarization is a common phenomenon in membrane separation processes and generally impairs mass transfer efficiency. Electrodialysis (ED) is considered a promising technology for concentrating high-salinity solutions used in air-conditioning systems; however, concentration polarization under high-concentration operating conditions remains insufficiently understood. In this study, a numerical framework combining a simplified model and a coupled transport model was developed to characterize concentration distributions within an ED concentrate channel. The effects of flow velocity, current density, and feed concentration on concentration profiles were systematically investigated. The results show that transmembrane water transport plays an important role in concentration polarization, and neglecting this effect leads to significant overestimation of ion concentration near the membrane surface. Although ion concentration increases markedly in the vicinity of the ion-exchange membranes, it remains nearly constant in the bulk region along the flow direction. Based on this non-uniform concentration distribution, a conceptual ED configuration with separated flow channels was proposed and evaluated. The results indicate that selectively extracting the enriched boundary-layer region can enhance the outlet concentration of the product stream, whereas increasing the intermediate channel width reduces volumetric yield, revealing a clear trade-off between concentration enhancement and production capacity. Full article

(This article belongs to the Special Issue Membranes for Electrochemical Energy and Related Systems)

► Show Figures

Figure 1

30 pages, 6127 KB

Open AccessReview

MBenes for Advanced Water Treatment and Desalination Membranes: A Bibliometric, Materials Engineering, and Future Perspectives Review

by Asam Amin Almulla and Fikri T. Dweiri

Membranes 2026, 16(8), 258; https://doi.org/10.3390/membranes16080258 - 28 Jul 2026

Abstract

Water scarcity and rising demand for safe water continue to motivate the development of improved treatment and desalination membranes. MBenes are an emerging family of two-dimensional transition-metal borides derived from layered MAB phases. Material-level experiments and computational studies indicate potentially useful electronic, structural, [...] Read more.

Water scarcity and rising demand for safe water continue to motivate the development of improved treatment and desalination membranes. MBenes are an emerging family of two-dimensional transition-metal borides derived from layered MAB phases. Material-level experiments and computational studies indicate potentially useful electronic, structural, and surface properties; however, direct evidence for MBene membranes remains limited. This review combines an author-generated bibliometric analysis of 279 Scopus-indexed records, retrieved on 14 April 2026, with a critical assessment of MBene synthesis, properties, and prospective membrane applications. Evidence from graphene, graphene oxide, transition-metal dichalcogenides, and MXenes is treated as analogous evidence rather than direct validation of MBene membrane performance. The analysis shows that MBene research is concentrated mainly in synthesis, computational modeling, catalysis, and energy storage, whereas experimentally validated water-treatment and desalination membranes are scarce. Priorities include reproducible MBene synthesis, controlled membrane fabrication, standardized performance testing, long-term stability and leaching assessment, and pilot-scale and techno-economic evaluation. Full article

(This article belongs to the Special Issue Advanced Membrane Technologies for Hypersaline Wastewater, Groundwater, and Seawater Desalination)

► Show Figures

Figure 1

20 pages, 2338 KB

Open AccessArticle

Auditable Clean-in-Place Decision Support from Routine SWRO SCADA: Selecting Differential-Pressure Recovery and Falsifying a Per-CIP-Reset Trigger

by Yi Hsiang Su, Fan Cheng Meng and Pieh Yu Chang

Membranes 2026, 16(8), 257; https://doi.org/10.3390/membranes16080257 - 28 Jul 2026

Abstract

Reverse osmosis (RO) desalination operators time membrane clean-in-place (CIP) by non-site-calibrated vendor thresholds. We present an auditable workflow that converts these thresholds into plant-calibrated decision support. It pre-specifies the recovery target and analysis unit, compares candidate signals with a five-test label-free battery, and [...] Read more.

Reverse osmosis (RO) desalination operators time membrane clean-in-place (CIP) by non-site-calibrated vendor thresholds. We present an auditable workflow that converts these thresholds into plant-calibrated decision support. It pre-specifies the recovery target and analysis unit, compares candidate signals with a five-test label-free battery, and reports composite weights only when identifiable. Using ≈two years of routine 10 min SCADA from one three-train island seawater RO plant (≈600 m³ d⁻¹), the battery selects normalised feed channel differential pressure (DP_norm) for site-specific cleaning-recovery review. On the false discovery rate (FDR)-effective unit (n = 14 campaigns), recovery is marginal and not FDR-significant (mid-p Benjamini–Hochberg q ≈ 0.141); DP_norm is therefore an operator-review signal, not an autonomous or FDR-confirmed trigger. The same battery invalidates a per-CIP-reset net driving pressure trigger as a clip-floor regression-to-the-mean artefact; it collapses under the pre-specified matched placebo and is reproduced by a fake-date null, a finding that is bounded to this plant and estimand, and not causal proof of a unique mechanism. The DP_norm of ≥1.20 review point is an exploratory, in-sample heuristic selected partly against the endogenous operator log, and its indexed economic comparison inherits that limitation. An identifiability-gated Bayesian power prior leaves the four-weight composite non-identifiable on this single-regime plant, pinning only the near-zero salt passage weight. The contribution is a bounded, estimand-based workflow that supports audit without replacing operators or the safety envelope. Full article

(This article belongs to the Special Issue New Challenges in Membrane Technology for Desalination)

► Show Figures

Graphical abstract

22 pages, 4002 KB

Open AccessArticle

Hybrid Response Surface–Particle Swarm Optimisation of Donnan Dialysis Processes for Aluminium Recovery from Water Treatment Sludge

by James Darmey, Sudesh Rathilal, Emmanuel Kweinor Tetteh and Julius Cudjoe Ahiekpor

Membranes 2026, 16(8), 256; https://doi.org/10.3390/membranes16080256 - 27 Jul 2026

Abstract

Sustainable recovery of aluminium from water treatment plant sludge (WTPS) offers a promising route for resource valorisation and waste reduction. In this study, Donnan dialysis (DD) is evaluated as a separation technique for recovering aluminium from a synthetic hydroxide-based feed simulating WTPS. A [...] Read more.

Sustainable recovery of aluminium from water treatment plant sludge (WTPS) offers a promising route for resource valorisation and waste reduction. In this study, Donnan dialysis (DD) is evaluated as a separation technique for recovering aluminium from a synthetic hydroxide-based feed simulating WTPS. A Box–Behnken design coupled with response surface methodology (BBD–RSM) was employed to model and quantify the effects of key operating parameters, namely feed pH, flow rate, initial aluminium concentration, runtime, and sweep solution concentration. Particle Swarm Optimisation (PSO) was integrated with the RSM framework to enhance global optimisation. The PSO approach predicted a maximum aluminium recovery of 99.1% under optimal conditions (pH 4.74, flow rate 98.60%, feed concentration 1313.3 ppm, runtime 21.5 h, and sweep concentration 0.25 M). Experimental validation yielded a recovery efficiency of 90.4%, corresponding to a deviation of 9.2% at a 95% confidence level with R² = 0.9632 and predicted R² = 0.9072. The results demonstrate that DD is an effective and scalable approach for recovering aluminium from hydroxide-rich sludge matrices, while PSO provides a robust optimisation strategy to address the nonlinearities inherent in membrane-based separation processes. This hybrid modelling framework advances process optimisation methodologies and supports the development of sustainable sludge-to-resource technologies in water treatment systems. Full article

► Show Figures

Figure 1

23 pages, 9422 KB

Open AccessReview

Research Status of Metal–Organic Frameworks in Field of Membrane Distillation

by Shuhua Ma, Quanxing Liao, Shiai Xu, Guanglan Che, Haoyi Chen and Juan Li

Membranes 2026, 16(8), 255; https://doi.org/10.3390/membranes16080255 - 27 Jul 2026

Abstract

Membrane distillation (MD) technology has become an effective solution to freshwater scarcity due to its low energy consumption, high separation efficiency, and ability to handle highly concentrated saline wastewater. Nevertheless, issues such as membrane wetting, membrane fouling, and low membrane flux severely limit [...] Read more.

Membrane distillation (MD) technology has become an effective solution to freshwater scarcity due to its low energy consumption, high separation efficiency, and ability to handle highly concentrated saline wastewater. Nevertheless, issues such as membrane wetting, membrane fouling, and low membrane flux severely limit its large-scale application. Composite membranes prepared using metal–organic framework (MOF) materials as fillers have become a research hotspot due to their advantages, such as permeable microporous channels, customizable pore structures, and modifiable active sites. These properties enable them to effectively reduce temperature polarization and concentration polarization phenomena. This article describes the characteristics of MOF materials and their current applications in the field of MD, with a comparative analysis of the applicability of MOF polycrystalline membranes and MOF composite membranes in MD, and discusses the working principle of MOFs in enhancing the performance of MD. Finally, the problems and challenges associated with the use of MOFs in MD applications are analyzed. This study aims to provide theoretical guidance for the application of MOF materials in the field of MD seawater desalination. Full article

(This article belongs to the Special Issue Metal-Organic Framework-Based Membranes for Applications in Molecular Separation)

► Show Figures

Figure 1

23 pages, 5096 KB

Open AccessArticle

Tuning the Permeability–Selectivity Trade-Off in Activated Carbon/PES Mixed Matrix Membranes via Compaction and Vapor-Induced Phase Separation

by Asseghaf Bintang Ramadhani, Jason Nathanael Thionardo, Muhammad Mirza Rahardianto, Annas Zakky Firmansyah, Kartika Nur ‘Anisa’, Chandrawati Putri Wulandari, Muslim Mahardika, Yudan Whulanza, Ario Sunar Baskoro, Thanongsak Thepsonthi, Nor Hasrul Akhmal Ngadiman and Gunawan Setia Prihandana

Membranes 2026, 16(8), 254; https://doi.org/10.3390/membranes16080254 - 25 Jul 2026

Abstract

This study investigates the synergistic effects of compaction pressure and vapor-induced phase separation (VIPS) on the morphological, mechanical, and initial filtration properties of activated carbon/polyethersulfone composite block membranes. Membranes were fabricated using varying compaction pressures (5 and 10 kg/cm²) and VIPS [...] Read more.

This study investigates the synergistic effects of compaction pressure and vapor-induced phase separation (VIPS) on the morphological, mechanical, and initial filtration properties of activated carbon/polyethersulfone composite block membranes. Membranes were fabricated using varying compaction pressures (5 and 10 kg/cm²) and VIPS exposure times (0 and 10 min) prior to direct non-solvent-induced phase separation (NIPS). Surface wettability analysis revealed that the optimized 50 wt.% activated carbon configurations were superhydrophilic (0° water contact angle), exhibiting instantaneous fluid absorption driven by strong capillary forces within the highly hygroscopic matrix. Morphological and gravimetric evaluations demonstrated that minimizing compaction (5 kg/cm²) and bypassing VIPS generated large macrovoids, resulting in the highest bulk internal porosity (61.05%) and maximum continuous gravity-driven water flux. Conversely, incorporating a 10-min VIPS exposure shifted the internal structure toward an interconnected sponge-like network. This structural transformation yielded the highest bovine serum albumin (BSA) rejection rate (12.97%) when paired with low pressure, as the network extended fluid residence time and maximized exposure to the activated carbon adsorption sites. Applying high compaction pressure (10 kg/cm²) to VIPS-treated membranes induced excessive polymer encapsulation of the active particles, significantly reducing separation efficiency while concurrently maximizing initial uniaxial tensile strength. Ultimately, these findings establish a foundational and highly tunable framework, demonstrating that calibrating mechanical compression alongside phase inversion dynamics balances permeability, adsorptive selectivity, and inter-particle binding cohesion for composite block membranes. Full article

(This article belongs to the Special Issue Design and Formation of Polymer Composite Membrane Material)

► Show Figures

Figure 1

20 pages, 10183 KB

Open AccessArticle

Separation of Taurine and Sodium Sulfate from Simulated Mother Liquor by Electrodialysis and Process Optimization

by Huiting Zhu, Douyan Cao and Jigang Zhao

Membranes 2026, 16(8), 253; https://doi.org/10.3390/membranes16080253 - 23 Jul 2026

Abstract

To address the high energy demand and product losses associated with separating taurine from sodium sulfate (Na₂SO₄) in the ethylene oxide route to taurine, electrodialytic desalination of a simulated taurine/Na₂SO₄ mother liquor was investigated. The effects [...] Read more.

To address the high energy demand and product losses associated with separating taurine from sodium sulfate (Na₂SO₄) in the ethylene oxide route to taurine, electrodialytic desalination of a simulated taurine/Na₂SO₄ mother liquor was investigated. The effects of applied voltage, circulation flow rate, and initial feed concentration on the desalination rate, product purity, taurine recovery, current efficiency, specific energy consumption, and membrane productivity were evaluated. Ion-transport behavior was further examined using COMSOL Multiphysics^® 6.3. At 14 V, a circulation flow rate of 200 L/h, and initial taurine and Na₂SO₄ concentrations of 100 and 68 g/L, respectively, the process achieved a taurine purity of 99.8% and a recovery of 98.9%. The specific electrical energy consumption of the electrodialysis unit was 0.56 kWh/kg Na₂SO₄, and the membrane productivity was 0.49 kg Na₂SO₄/(m²·h). One of the key findings of this work is that the low-salt stage plays a dominant role in process economics. This observation led to a simple endpoint-control strategy. The ED operation is stopped when the Na₂SO₄ concentration in the dilute compartment drops to about 2 g/L. This avoids prolonged operation under inefficient conditions and reduces ED energy consumption by 16.5%. Within the binary simulated system and the defined cost boundary, the proposed process provided a higher taurine recovery and a lower estimated separation cost than the conventional crystallization route. These results demonstrate the laboratory-scale feasibility of electrodialysis for desalting simulated taurine mother liquor. Full article

(This article belongs to the Special Issue Electrodialysis and Novel Electro-Membrane Processes)

► Show Figures

Figure 1

14 pages, 5852 KB

Open AccessArticle

Functional In Vitro Expression of the Succinate–Acetate Transporter SatP and an Initial Screening Strategy

by Yuelang Yao, Bernhard Schuster, Karola Vorauer-Uhl and Diethard Mattanovich

Membranes 2026, 16(8), 252; https://doi.org/10.3390/membranes16080252 - 23 Jul 2026

Abstract

In vitro protein expression has gained considerable attention due to its experimental flexibility and time efficiency. This method employs essential transcriptional components and is particularly advantageous for expressing proteins that are challenging to produce in living systems, such as membrane or toxic proteins. [...] Read more.

In vitro protein expression has gained considerable attention due to its experimental flexibility and time efficiency. This method employs essential transcriptional components and is particularly advantageous for expressing proteins that are challenging to produce in living systems, such as membrane or toxic proteins. Membrane acetate transporters regulate cellular acetate levels and are important for microbial engineering in industrial fermentation processes. In this study, the succinate–acetate transporter protein SatP from Escherichia coli was functionally expressed utilizing a cell-free system and subsequently characterized through single-channel recordings. Beyond confirming its transport activities, we identified malate and fumarate as additional potential substrates of SatP. The successful in vitro expression of SatP lays the foundation for cell-free screening of acetate transporters. We then further investigated a preliminary screening assay and proposed a potential strategy for the rapid expression and functional characterization of acetate transport proteins. Because acetate accumulation can inhibit microbial growth and reduce fermentation efficiency, a better understanding of SatP-mediated acetate transport may facilitate the engineering of microbial strains with enhanced acetate tolerance and improved product yields. This knowledge provides a foundation for the rational optimization of industrial fermentation processes. Full article

(This article belongs to the Section Biological Membranes)

► Show Figures

Graphical abstract

22 pages, 6627 KB

Open AccessArticle

Membrane-Based Decolourisation and Purification of Starch Hydrolysates: A Systematic UF–NF Screening Study

by Camila Cabeza, Amal El Gohary Ahmed and Michael Harasek

Membranes 2026, 16(7), 251; https://doi.org/10.3390/membranes16070251 - 22 Jul 2026

Abstract

Membrane-based processes offer promising sustainable alternatives for the decolourisation and purification of starch hydrolysates, yet membrane selection and operating conditions remain the most critical challenges. This study systematically evaluates the performance of polymeric ultrafiltration (UF) and nanofiltration (NF) membranes for starch hydrolysate syrup [...] Read more.

Membrane-based processes offer promising sustainable alternatives for the decolourisation and purification of starch hydrolysates, yet membrane selection and operating conditions remain the most critical challenges. This study systematically evaluates the performance of polymeric ultrafiltration (UF) and nanofiltration (NF) membranes for starch hydrolysate syrup treatment. Experiments were conducted in a lab-scale cross-flow filtration system using five UF and three NF flat-sheet polymeric membranes under varying temperatures, transmembrane pressures, and feed concentrations. Separation performance was assessed through colour removal, sugar recovery, permeate flux, and alongside indicators of fouling behaviour. UF membranes with molecular weight cut-offs of 100, 70, and 5 kDa exhibited the most favourable performance at 60 °C and 8 bar, achieving partial colour removal (18–32%) with high permeate fluxes (84–130 kg·m⁻²·h⁻¹) and limited sugar losses (0.7–19.9%). NF membranes showed significantly higher colour rejection (32–100%) but were associated with substantial sugar losses (up to 96%), limiting their applicability for selective decolourisation; however, their high sugar retention capacity suggests potential for product concentration and the removal of low-molecular-weight impurities. Overall, UF represents a suitable approach for partial colour removal in starch hydrolysates, while NF may be better suited for product concentration and the removal of low-molecular-weight impurities, as well as auxiliary applications such as water recovery. These findings provide a systematic basis for membrane selection and process optimisation in industrial starch hydrolysate purification. Full article

(This article belongs to the Special Issue Application of Membrane Technologies in Food Processing)

► Show Figures

Figure 1

17 pages, 5757 KB

Open AccessArticle

Fabrication of Ordered Mesoporous Silica/Polyethersulfone Mixed-Matrix Membranes for Improved Removal of Middle-Molecule Toxins Within Hemodialysis

by Rongrong Ji, Peiyan Shi, Ting Dong, Wenjie Hou and Kangjian Tang

Membranes 2026, 16(7), 250; https://doi.org/10.3390/membranes16070250 - 21 Jul 2026

Abstract

As the core component of an artificial kidney, a hemodialysis membrane can remove metabolic wastes and excess fluid from the blood while retaining essential proteins. Despite their essential role in blood purification, current hemodialysis membranes still show limited efficiency in clearing middle-molecule uremic [...] Read more.

As the core component of an artificial kidney, a hemodialysis membrane can remove metabolic wastes and excess fluid from the blood while retaining essential proteins. Despite their essential role in blood purification, current hemodialysis membranes still show limited efficiency in clearing middle-molecule uremic toxins, especially β₂-microglobulin. Ordered mesoporous silica (SBA-15) was used as an inorganic pore-regulating additive to construct ordered mesoporous silica/polyethersulfone (PES) mixed-matrix membranes for separation applications. The incorporation of SBA-15 may help form additional effective transport pathways in the PES membrane by regulating pore formation, increasing membrane hydrophilicity, and improving apparent pore connectivity, thereby reducing the apparent transport resistance of middle-molecule solutes. As a result, the composite membranes achieved improved dialysis performance while maintaining high BSA retention. The SBA-15 loading was systematically optimized. Relative to the pristine PES membrane, the 7 wt.% SBA-15 membrane reduced the water contact angle from 65.1° to 49.0° and increased lysozyme reduction from 40.9% to 55.2%, with pure water permeability reaching 261.5 L m⁻² h⁻¹ bar⁻¹ and bovine serum albumin (BSA) retention remaining above 90%. These results suggest that SBA-15 may regulate the pore structure of PES membranes and improve apparent pore connectivity, thereby facilitating middle-molecule solute transport while maintaining high BSA retention. Full article

► Show Figures

Figure 1

11 pages, 5293 KB

Open AccessArticle

Identification and Characterization of a Phenyl(trifluoro-methyl)-pyrimidine Positive Allosteric Modulator of the Secretin Receptor

by Kaleeckal G. Harikumar, Daniela G. Dengler, Leire Borrega Roman, Robert Ardecky, Eduard A. Sergienko and Laurence J. Miller

Membranes 2026, 16(7), 249; https://doi.org/10.3390/membranes16070249 - 21 Jul 2026

Abstract

G protein-coupled receptors (GPCRs) are among the most common drug targets, with numerous agonists and antagonists approved for clinical use. More recently, it has been appreciated that drugs can also modulate the action of natural agonists of these receptors, thus providing unique clinical [...] Read more.

G protein-coupled receptors (GPCRs) are among the most common drug targets, with numerous agonists and antagonists approved for clinical use. More recently, it has been appreciated that drugs can also modulate the action of natural agonists of these receptors, thus providing unique clinical advantages. Here, we describe the identification and characterization of a small molecule positive allosteric modulator (PAM) of secretin action at the class B G protein-coupled secretin receptor. This phenyl(trifluoromethyl)-pyrimidine can occupy the secretin receptor without stimulating its internalization, yet priming it to enhance both the potency and efficacy of the action of natural secretin. This is also shown to exhibit its effects on cells expressing low numbers of these receptors, without enhancing the effects of other structurally related hormones acting at other class B GPCRs. The mechanism responsible for this PAM effect is the slowing of the off-rate of receptor-bound secretin. This compound can serve as a lead to the development of other drugs that enhance the action of natural endogenous secretin and can be utilized to explore the potential therapeutic utility of such compounds. Full article

(This article belongs to the Section Biological Membranes)

► Show Figures

Figure 1

13 pages, 1395 KB

Open AccessArticle

Selective Separation of Inorganic and Organic Carbonates in Aqueous Solutions by Reverse Osmosis (RO) and Nanofiltration (NF) Membranes

by Rahma Al Busaidi, Budoor Al Umairi, Zulfiqar Ahmad Rehan and Mohammed Al-Abri

Membranes 2026, 16(7), 248; https://doi.org/10.3390/membranes16070248 - 20 Jul 2026

Abstract

This study presents a systematic comparison of commercial reverse osmosis (RO) and nanofiltration (NF) membranes for the separation of inorganic and organic carbonates from aqueous solutions, providing insight into the roles of membrane pore structure and surface charge in governing separation mechanisms. Membrane [...] Read more.

This study presents a systematic comparison of commercial reverse osmosis (RO) and nanofiltration (NF) membranes for the separation of inorganic and organic carbonates from aqueous solutions, providing insight into the roles of membrane pore structure and surface charge in governing separation mechanisms. Membrane molecular weight cut-off (MWCO), zeta potential, and thermal stability were characterized and correlated with separation performance. The RO membrane exhibited a lower MWCO and a more negative surface charge than the NF membrane, resulting in superior rejection of both inorganic and organic carbonates. For inorganic carbonates, rejection increased with pH owing to enhanced carbonate ionization and stronger electrostatic repulsion, reaching 91–98% for the RO membrane compared with 60–95% for the NF membrane. In contrast, the rejection of neutral organic carbonates was governed primarily by steric exclusion, with the RO membrane achieving approximately 80% rejection, whereas the NF membrane exhibited negligible removal. These findings demonstrate the combined influence of membrane pore size and surface charge on carbonate separation and provide practical guidance for selecting commercial membranes for efficient carbonate removal in water treatment applications. Full article

► Show Figures

Figure 1

18 pages, 3519 KB

Open AccessArticle

Experimental Design–Guided Optimization of Pervaporative Dehydration of an Esterification Mixture

by Fatimatou Toure Lo, Magalie Claeys-Bruno, Philippe Moulin and Emilie Carretier

Membranes 2026, 16(7), 247; https://doi.org/10.3390/membranes16070247 - 18 Jul 2026

Abstract

This study investigates the pervaporation dehydration of a quaternary esterification mixture containing water, 2-ethylhexyl acrylate, 2-ethylhexanol, and propionic acid using a pilot-scale HybSi membrane (BTESE on Al₂O₃). A design of experiments was implemented to evaluate the influence of mixture [...] Read more.

This study investigates the pervaporation dehydration of a quaternary esterification mixture containing water, 2-ethylhexyl acrylate, 2-ethylhexanol, and propionic acid using a pilot-scale HybSi membrane (BTESE on Al₂O₃). A design of experiments was implemented to evaluate the influence of mixture composition on water content in the retentate, permeation flux, and water removal efficiency. Descriptive analysis revealed that the initial water content is the dominant factor governing both permeation flux and dehydration performance, whereas acid, alcohol, and ester have secondary but interactive effects. Reduced cubic polynomial models including linear, binary, and ternary interactions were developed, showing good agreement with experimental data. Ternary diagrams highlighted composition regions where molecular interactions significantly affect separation performance. Multi-response optimization based on desirability functions identified optimal operating conditions at high initial water content (1.146 wt.%), yielding a permeation flux of 0.144 kg·m⁻²·h⁻¹, a final water content close to the industrial target (0.2 wt.%), and a water removal efficiency of 86%. Experimental validation confirmed the reliability of the predictive model. The results provide insights into composition–performance relationships and demonstrate the suitability of BTESE membranes for low-water-content esterification systems. Full article

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

► Show Figures

Figure 1

17 pages, 3262 KB

Open AccessArticle

Numerical Solution of the Problem of Relaxation Filtration of a Suspension Through a Radial Filter at a Constant Flow Velocity

by Volodymyr Brazhenko, Bakhtiyor Kh. Khuzhayorov, Usmonali Saydullaev, Jamol Makhmudov and Iroda Beknazarova

Membranes 2026, 16(7), 246; https://doi.org/10.3390/membranes16070246 - 17 Jul 2026

Abstract

This paper investigates the relaxation filtration of a suspension through a radial filter surface under conditions of constant flow velocity. A mathematical model for relaxation cake growth is formulated based on the liquid-phase continuity equation, Darcy’s relaxation law, and constitutive relations for both [...] Read more.

This paper investigates the relaxation filtration of a suspension through a radial filter surface under conditions of constant flow velocity. A mathematical model for relaxation cake growth is formulated based on the liquid-phase continuity equation, Darcy’s relaxation law, and constitutive relations for both compressive and liquid pressures. The resulting governing equation is a nonlinear partial differential equation for the compressive pressure, complemented by a Stefan condition that characterizes the motion of the cake–slurry interface. The moving-boundary problem is solved numerically using a finite difference method employing a coordinate-based front-tracking technique combined with iterative procedures. The numerical results demonstrate the influence of relaxation effects on cake formation. Increasing the relaxation time slows the compaction process, thereby maintaining higher porosity and promoting accelerated growth of the cake layer thickness. Full article

► Show Figures

Figure 1

54 pages, 1165 KB

Open AccessReview

Proton-Exchange Membranes with Stabilized Conductivity

by Andrey A. Nechitailov, Anna Krasnova, Angelina G. Kastsova and Nadezhda V. Glebova

Membranes 2026, 16(7), 245; https://doi.org/10.3390/membranes16070245 - 17 Jul 2026

Abstract

Proton-exchange membranes are crucial for water electrolyzers and fuel cells, but their performance declines under low humidity due to dehydration. Existing reviews mainly list experimental results without analyzing the mechanisms of proton conductivity stabilization. This review systematically summarizes approaches to enhance moisture-independent proton [...] Read more.

Proton-exchange membranes are crucial for water electrolyzers and fuel cells, but their performance declines under low humidity due to dehydration. Existing reviews mainly list experimental results without analyzing the mechanisms of proton conductivity stabilization. This review systematically summarizes approaches to enhance moisture-independent proton conductivity and evaluates their prospects. Key factors governing conductivity include microstructure, sulfonic group concentration, and hydration level. Stability under dry conditions depends on water retention and thermal resistance. Main strategies involve hybrid composite membranes, ionomer structure control via pre-treatments, and novel proton-conducting polymers. Promising directions include oriented channel structures, MOFs, and graphene-based materials. The stabilization mechanism relies on retaining water through hydrophilic additives that form stable hydrates, enabling proton transport even under harsh conditions (up to 120 °C and 50% RH, per US DOE targets). Among Nafion alternatives, sulfonated aromatic polymers and phosphoric-acid-doped polybenzimidazole demonstrate good performance at elevated temperatures (100–200 °C), though durability remains a challenge for the latter. Despite ongoing research, Nafion-based composites still offer one of the best overall balances of conductivity, stability, and processability. A significant research gap persists: long-term membrane performance is poorly studied, and many additives degrade over time or block proton transport sites due to ion exchange with metal cations. Full article

(This article belongs to the Special Issue Advanced Membranes for Hydrogen Energy Systems: Fuel Cells and Electrolyzers)

► Show Figures

Graphical abstract

22 pages, 5014 KB

Open AccessReview

Progress on Physical Processes for Boiler Feedwater Deoxygenation

by Binglin Li, Andong Jian, Jiayu Lu and Jiaxi Lv

Membranes 2026, 16(7), 244; https://doi.org/10.3390/membranes16070244 - 17 Jul 2026

Abstract

With the expansion of thermal power units and higher operating parameters, oxygen corrosion in boiler feedwater has become increasingly serious. Traditional methods such as thermal, stripping, and vacuum deaeration are mature but limited by energy consumption, system complexity, and adaptability. In contrast, membrane [...] Read more.

With the expansion of thermal power units and higher operating parameters, oxygen corrosion in boiler feedwater has become increasingly serious. Traditional methods such as thermal, stripping, and vacuum deaeration are mature but limited by energy consumption, system complexity, and adaptability. In contrast, membrane deaeration has emerged as a promising alternative due to its energy efficiency, compact design, and superior adaptability. Recent advances in membrane materials and module configurations have enabled efficient dissolved oxygen removal to ppb levels under mild operating conditions. This review summarizes the mechanisms, equipment, and application features of conventional methods, and outlines progress in membrane deaeration regarding mass transfer, module design, and process integration. Future development will focus on multi-technology coupling, mass transfer intensification, and intelligent control to achieve ppb-level oxygen removal. Full article

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

► Show Figures

Figure 1

15 pages, 7469 KB

Open AccessArticle

Boosting Capacitive Deionization Performance via Bimetallic Synergistic Engineering of Electrospun Co/N-Doped Porous Carbon Nanofibers

by Xinyue Ma, Yuan Li, Kuo Meng, Chengbo Kou, Binling Li, Zhonglei Zhu, Haojie Li, Zhihan Deng, Runze Yang, Hupeng Zhou, Xin Wang, Lang Luo, Fuming Chen, Chengding Gu, Yuxiao Zhang and Lu Guo

Membranes 2026, 16(7), 243; https://doi.org/10.3390/membranes16070243 - 17 Jul 2026

Abstract

Capacitive deionization (CDI) is an environmentally advantageous desalination technology that is particularly suitable for the treatment of low- to medium-concentration saline water. Among different electrode materials, carbon materials are widely used due to their good electrical conductivity and high specific surface area, while [...] Read more.

Capacitive deionization (CDI) is an environmentally advantageous desalination technology that is particularly suitable for the treatment of low- to medium-concentration saline water. Among different electrode materials, carbon materials are widely used due to their good electrical conductivity and high specific surface area, while they suffer from limited ion adsorption capacity. In this study, a cobalt/nitrogen-doped porous carbon fiber composite with Zn-induced porosity (CoNG@V@CNF), where “V” stands for “volatile pore-forming agent”, has been successfully prepared via electrospinning combined with a high-temperature carbonization process. The introduction of trace Co nanoparticles enhances the stability of porous graphene. In addition, N doping contributes to improved wettability and electronic conductivity, and the carbon fiber structure constructs a three-dimensional conductive network, providing fast channels for ion transport. Electrochemical tests show that the specific capacitance of CoNG@V@CNF reaches 252.76 F g⁻¹, demonstrating its superior charge storage capability. Furthermore, this study achieved a high salt adsorption capacity of 58.28 mg g⁻¹ and a competitive desalination rate performance of 1.94 mg g⁻¹ min⁻¹. After 40 cycles of testing, the salt adsorption capacity (SAC) remains at 56.72 mg g⁻¹, demonstrating its high stability during multiple charging and discharging processes. This work provides a new design strategy for developing high-performance CDI electrode materials. Full article

(This article belongs to the Special Issue Nanocomposite Membranes for Electrolysis, Fuel Cells, Batteries, and Desalination)

► Show Figures

Figure 1

17 pages, 3031 KB

Open AccessArticle

Bench-Scale Evaluation of Hydraulic Performance and Rejection of Bisphenol-A and Estradiol by Different Nanofiltration Membranes as a Post-Treatment Step at the Lago Norte WTP—Brasília/DF, Brazil

by Bianca Campos Gonçalves, Cristina Celia Silveira Brandão and Sara Regina Morais Kollar

Membranes 2026, 16(7), 242; https://doi.org/10.3390/membranes16070242 - 17 Jul 2026

Abstract

Emerging micropollutants in drinking water sources represents a growing challenge for water treatment systems. Bisphenol-A (BPA) and 17β-estradiol (E2) are endocrine disruptors widely detected in aquatic matrices that are not efficiently removed by conventional treatment. This study evaluated, at the bench scale, operational [...] Read more.

Emerging micropollutants in drinking water sources represents a growing challenge for water treatment systems. Bisphenol-A (BPA) and 17β-estradiol (E2) are endocrine disruptors widely detected in aquatic matrices that are not efficiently removed by conventional treatment. This study evaluated, at the bench scale, operational performance and rejection of BPA and E2 by three nanofiltration membranes—NFM1, NFM2 and NFM3—operating at 8 bar and using ultrafiltered water from the Lago Norte Water Treatment Plant (WTP), Brasília/DF, Brazil, spiked with both compounds at 150–250 µg/L, as the feed matrix. Hydraulic parameters, such as permeate flux and water permeability, were assessed alongside rejection. NFM1 exhibited the highest permeate fluxes (136.1 and 171.7 L/h·m²); however, it showed the lowest rejection (E2: 57–73%; BPA: 28–60%). The NFM2 membrane showed intermediate rejection behavior (E2: 86–89%; BPA: 67–91%) but presented the lowest permeate flux (51.2 to 63.3 L/h·m²). The NFM3 membrane presented the highest rejection and greatest operational stability (E2: 90–95%; BPA: 95–97%), with a permeate flux of 59.1 to 67.0 L/h·m². Size exclusion was the predominant removal mechanism, though adsorption also contributed during the initial hours of operation. The results confirm a trade-off between permeate production and contaminant rejection, with no single membrane outperforming all others across all criteria. Full article

(This article belongs to the Special Issue Nanofiltration Membranes for Organic Pollutants Removal)

► Show Figures

Figure 1

Journal Description

Membranes

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI