Membranes

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

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)

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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)

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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)

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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

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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)

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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

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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)

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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

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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)

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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)

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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)

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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)

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20 pages, 1798 KB

Open AccessArticle

A Pseudoenzymatic Regulatory Role of the Noncatalytic Subunit of the Neurotoxin Vipoxin at Arachidonic-Acid-Containing Membrane Interfaces

by Svetla Petrova, Kristina Mircheva, Evgenia Sotirovska, Nikolay Alexandrov Grozev, Kirilka Stefanova Mladenova, Pavel Videv, Jordan Doumanov and Konstantin Balashev

Membranes 2026, 16(7), 241; https://doi.org/10.3390/membranes16070241 - 16 Jul 2026

Abstract

Secreted phospholipases A₂ (sPLA₂s) act at lipid interfaces where enzymatic turnover is strongly influenced by membrane packing and interfacial physicochemical conditions. Vipoxin, a heterodimeric neurotoxin from Vipera ammodytes meridionalis, is one such complex, comprising a catalytically active sPLA₂ [...] Read more.

Secreted phospholipases A₂ (sPLA₂s) act at lipid interfaces where enzymatic turnover is strongly influenced by membrane packing and interfacial physicochemical conditions. Vipoxin, a heterodimeric neurotoxin from Vipera ammodytes meridionalis, is one such complex, comprising a catalytically active sPLA₂ subunit (VBC) and a catalytically impaired homolog, VAC, suggesting a pseudoenzymatic regulatory role. Using SAPC Langmuir monolayers as a model of arachidonic-acid-containing membranes, we monitored the compensated monolayer area change,

Δ A (t)

, under barostatic conditions as an integrated readout of the interfacial behavior of Vipoxin and its isolated subunits. The responses revealed pronounced modulation by surface pressure and by the acidic acetate versus basic Tris-HCl subphase environment: VBC retained high catalytic competence under both conditions, whereas Vipoxin displayed greater environmental sensitivity, consistent with VAC-dependent modulation of enzyme–membrane coupling. VAC, although lacking canonical catalytic activity, produced measurable interfacial effects under acidic conditions and high lateral pressure. Analysis using the interfacial quality parameter

Q_{m}

demonstrated that VAC modifies the pressure dependence of the heterodimer and stabilizes interfacial accommodation of VBC. These findings indicate that VAC functions as a pseudoenzymatic regulatory subunit whose role emerges from dynamic coupling between enzymatic activity and lipid interfacial organization. Full article

(This article belongs to the Special Issue Nanoscale Interactions at the Bio-Interface: From Model Membranes to Biomedical Applications)

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6 pages, 185 KB

Open AccessEditorial

Membrane Distillation: Module Design and Application Performance

by Lebea N. Nthunya and Bhekie B. Mamba

Membranes 2026, 16(7), 240; https://doi.org/10.3390/membranes16070240 - 16 Jul 2026

Abstract

Membrane distillation (MD) has emerged as a thermal process used in desalination, wastewater treatment, and resource recovery. It has demonstrated high salt rejection, but process scale-up is affected by unstable process performance caused by membrane fouling and scaling, limitations of heat and mass [...] Read more.

Membrane distillation (MD) has emerged as a thermal process used in desalination, wastewater treatment, and resource recovery. It has demonstrated high salt rejection, but process scale-up is affected by unstable process performance caused by membrane fouling and scaling, limitations of heat and mass transfer, and module design challenges. The research outputs presented here assess membrane module design and configurations, hydrodynamic optimization, understanding of membrane fouling, and its control in long-term and intermittent process operation. Furthermore, the integration of crystallization, resource recovery from wastewater, and techno-economic feasibility are also elucidated. The collective findings showed that optimization of the modules, process operating conditions, and the integration of crystallization could improve MD performance stability and resource recovery. Beyond crystallization, MD has demonstrated the ability to recover nutrients from anaerobic digestate, suggesting process expansion directions. These findings provide insights into the key requirements for MD implementation at an industrial scale. Full article

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

35 pages, 11009 KB

Open AccessArticle

Machine Learning–Driven Surrogate Modeling and Operating-Point Selection for a Microfluidic Diffusion-Membrane Platform for Transdermal Drug Delivery

by Tara Torabi, Mahsa Jafar Harasy, Jafar Tahmoresnezhad, Samira Malekmohammadi, Adolfo Iulianelli and Kamran Ghasemzadeh

Membranes 2026, 16(7), 239; https://doi.org/10.3390/membranes16070239 - 15 Jul 2026

Abstract

Microfluidic diffusion systems provide a powerful in vitro platform for evaluating transdermal drug delivery (TDD), yet their predictive capability is often constrained by limited experimental datasets and nonlinear transport behavior across membrane—device configurations. This study integrates machine learning (ML) with microfluidic experimentation to [...] Read more.

Microfluidic diffusion systems provide a powerful in vitro platform for evaluating transdermal drug delivery (TDD), yet their predictive capability is often constrained by limited experimental datasets and nonlinear transport behavior across membrane—device configurations. This study integrates machine learning (ML) with microfluidic experimentation to develop accurate and generalizable surrogate models for cumulative drug permeation under different hydrodynamic and membrane conditions. This work presents an ML-augmented microfluidic TDD framework for predicting cumulative drug permeation from small experimental datasets. Caffeine cream permeation was examined across twelve device—membrane configurations (sMDC, mMDC, and LiveBox2 paired with PET, CA, rat skin, and alginate) at three perfusion flow rates. For each configuration, SVR, MLP, RFR, GBR, XGB, and KNN models were trained and cross-validated using only 33 experimental measurements. SVR showed the strongest overall performance among the evaluated models, achieving test R² values typically above 0.97 and RMSE values of <1–3 µg/cm², accurately capturing the nonlinear time-flow-cumulative mass behavior of TDD profiles. A domain-bounded Gaussian-noise augmentation strategy was used to increase local sampling density while keeping augmented values within the experimentally observed time and cumulative-mass ranges. Polynomial equations were obtained from the predictions of SVR to capture the interaction between inputs and outputs. The trained SVR surrogates were then used for automated steady-state identification and surrogate-based operating-point selection, revealing the dependence of the selected flow rate on membrane permeability and device geometry. Alginate consistently delivered the highest steady-state cumulative mass across all systems (up to ~448 µg/cm²), establishing it as the most efficient TDD membrane among those evaluated. Finally, compact third-degree polynomial equations were derived from the SVR predictions, enabling explicit analytical prediction and rapid design-space exploration. Overall, these ML-derived models and analytical equations provide a fast, low-cost tool for predictive design, enabling rapid microfluidic system evaluation and operating-condition selection, and significantly accelerating the development and screening of next-generation TDD platforms. Full article

(This article belongs to the Special Issue Membrane Carriers for Drug Delivery Purposes)

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24 pages, 2096 KB

Open AccessReview

External Microplastic Filters for Washing Machines: Advances, Technical Challenges, and Biofouling Mitigation

by Hyeri Song, Yeo Min Kim, Da Hyun Yoo, Sun Ae Kim and Chanhyuk Park

Membranes 2026, 16(7), 238; https://doi.org/10.3390/membranes16070238 - 13 Jul 2026

Abstract

Laundry-derived microplastic fibers are major source of environmental microplastic pollution. Because conventional wastewater treatment processes cannot completely remove fibrous microplastics, washing machine-mounted filters have been developed as a promising source-control approach for the reduction in microfiber emissions. This review thus summarizes recent advances [...] Read more.

Laundry-derived microplastic fibers are major source of environmental microplastic pollution. Because conventional wastewater treatment processes cannot completely remove fibrous microplastics, washing machine-mounted filters have been developed as a promising source-control approach for the reduction in microfiber emissions. This review thus summarizes recent advances in external filtration systems and membrane-based technologies for laundry wastewater treatment. The characteristics of laundry wastewater, microfiber release behavior, and recent regulatory trends are discussed together with the performance of commercially available filtration systems. The applicability of advanced membrane materials, including ceramic membranes, for high-efficiency microfiber separation is also highlighted. Particular attention is given to the microbial contamination and biofouling of microplastic filters, which can affect their filtration efficiency, operational stability, and household hygiene. This review also discusses the potential reuse of captured microplastics for membrane fabrication as a sustainable pathway for waste valorization and circular resource utilization. Finally, current limitations and future perspectives for the development of efficient, hygienic, and sustainable laundry microplastic filtration technologies are discussed. Full article

(This article belongs to the Special Issue Ceramic Membranes for Wastewater and Water Reuse (2nd Edition))

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39 pages, 740 KB

Open AccessReview

From Atomic Channels to Deployable Membranes: A Design-Oriented Framework for Graphene Oxide Transport, Functionalization, and Scalability

by Awad Alzebair, Didem Aydin, İlkay Hilal Gübbük and Mustafa Ersoz

Membranes 2026, 16(7), 237; https://doi.org/10.3390/membranes16070237 - 10 Jul 2026

Abstract

Graphene oxide (GO) membranes present a compelling alternative to the permeability-selectivity trade-off inherent in conventional polymer membranes. However, the incomplete mechanistic understanding and the absence of scalable, defect-controlled fabrication processes continue to hinder their practical deployment. This review synthesizes and integrates transport mechanisms, [...] Read more.

Graphene oxide (GO) membranes present a compelling alternative to the permeability-selectivity trade-off inherent in conventional polymer membranes. However, the incomplete mechanistic understanding and the absence of scalable, defect-controlled fabrication processes continue to hinder their practical deployment. This review synthesizes and integrates transport mechanisms, computational modeling, fabrication, and translational constraints across graphene-based membrane architectures into a comprehensive design-oriented framework. Five key aspects of this synthesis are highlighted. Firstly, the available evidence supports a three-regime transport model, which unifies viscous near-frictionless flow, activated molecular hopping, and solution–diffusion. This reframes selectivity as a tunable function of the C/O ratio and interlayer chemistry. Secondly, a quantitative parity analysis of literature data reveals that classical molecular dynamics tends to overestimate GO laminate water permeance by a representative factor of approximately 3–8× across the matched comparisons examined. This discrepancy can be corrected using a tortuosity–porosity factor derived from wet-state XRD. Machine-learning force fields (GAP, MACE), while still in an early stage of development with limited reported applications, narrow the residual discrepancy to within 1.5–2× in the studies reviewed. Thirdly, a tiered computational roadmap identifies nuclear quantum effects as critical for proton-transport applications but unresolved for water permeance in GO laminate geometry. Fourthly, performance across water nanofiltration, gas separation, ion recovery, and osmotic energy harvesting is benchmarked against commercial references, with explicit caveats regarding the heterogeneity of testing conditions across cited studies, alongside a technology readiness assessment. Lastly, a standardized 500-h hydraulic stability protocol is proposed to facilitate cross-laboratory comparison. Collectively, this synthesis provides a structured, albeit not exhaustively validated, basis for the discussion of next-generation membrane design. Full article

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

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22 pages, 8569 KB

Open AccessArticle

Humic Acid Recovery from Leachate Nanofiltration Concentrate Using Halloysite Nanotube-Coated Tubular Ceramic Ultrafiltration Membrane

by Sultan Akarçay Demir, Gamze Varank, Derya Y. Koseoglu-Imer, Gülay Arslan Cene, Emine Can-Güven, Senem Yazici Guvenc and Oruc Kaan Turk

Membranes 2026, 16(7), 236; https://doi.org/10.3390/membranes16070236 - 10 Jul 2026

Abstract

Landfill wastewater is a serious environmental problem and represents a high-concentration source of valuable organic compounds such as humic acids (HAs). The nanofiltration (NF) concentrate generated during treatment poses an even more significant environmental challenge, and the recovery of these substances is compatible [...] Read more.

Landfill wastewater is a serious environmental problem and represents a high-concentration source of valuable organic compounds such as humic acids (HAs). The nanofiltration (NF) concentrate generated during treatment poses an even more significant environmental challenge, and the recovery of these substances is compatible with circular economy principles but requires innovative, pollution-resistant separation technologies. This study presents a novel hybrid approach for HA recovery by integrating naturally occurring clay minerals, such as halloysite nanotubes (HNTs), as a dynamic coating layer onto tube-shaped ceramic ultrafiltration membranes. The research was conducted in two stages: batch adsorption–desorption experiments followed by membrane integration. In the first stage, the batch adsorption studies showed that HA adsorption by HNTs followed the Freundlich isotherm model. The maximum HA adsorption capacity for HNTs increased with increasing initial concentration. In desorption studies, recovery rates of 74.6% were achieved with 1.5 N sodium hydroxide (NaOH) and 67.5% with 1.5 N potassium hydroxide (KOH). In membrane studies, the optimum HNT coating concentration was determined as 0.05 g/L. While an average removal efficiency of 85.3% was obtained in synthetic HA filtration, the desorption efficiency after regeneration was around 35–37%. In experiments with real NF concentrate, HA removal efficiencies ranged from 19 to 64% for concentrations of 5, 10, and 20 mg/L, with the highest desorption efficiency (59.3%) obtained in the 10 mg/L NF concentrate. The results reveal that the complex structure and competing components in the real wastewater matrix limit the removal and recovery performance compared to synthetic solutions. Full article

(This article belongs to the Special Issue Membrane Materials and Technologies for Sustainable Water Treatment)

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28 pages, 1751 KB

Open AccessArticle

Short-Term Laboratory Assessment of Coagulation-Assisted Ceramic Membrane Filtration and Reverse Osmosis Polishing of High-Strength Brewery Wastewater

by Agnieszka Urbanowska, Izabela Polowczyk, Mateusz Kruszelnicki, Przemysław Seruga and Natalia Matura

Membranes 2026, 16(7), 235; https://doi.org/10.3390/membranes16070235 - 8 Jul 2026

Abstract

Brewery wastewater is a high-strength industrial effluent containing substantial organic, suspended, and colloidal fractions and therefore requires multistage treatment. This study evaluated sedimentation, prefiltration, coagulation, ceramic membrane filtration, and reverse osmosis (RO) polishing for improving the quality of actual brewery wastewater under short-term [...] Read more.

Brewery wastewater is a high-strength industrial effluent containing substantial organic, suspended, and colloidal fractions and therefore requires multistage treatment. This study evaluated sedimentation, prefiltration, coagulation, ceramic membrane filtration, and reverse osmosis (RO) polishing for improving the quality of actual brewery wastewater under short-term laboratory conditions. The acidic wastewater had chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), and dissolved organic carbon (DOC) values of 48,230 mg O₂/L, 34,160 mg O₂/L, and 6492 mg C/L, respectively. Three configurations were investigated: mechanical treatment; PIX 113 coagulation followed by ceramic microfiltration (MF), ultrafiltration (UF), or fine UF; and an integrated UF-RO system. Performance was assessed using contaminant removal, relative permeate flux (J/J₀), particle size analysis, dynamic light scattering, and zeta potential. Sedimentation and prefiltration provided limited treatment, whereas coagulation effectively destabilized colloids; a PIX 113 dosage of 2 mL/L was selected as a favorable compromise among the tested dosages. Among the ceramic membrane-based trains, the train ending with the 1 kDa membrane produced the highest-quality permeate, with overall COD, BOD₅, and DOC removals of 78.2%, 88.7%, and 49.8%, respectively. The tested sedimentation–prefiltration–coagulation-50 kDa UF-RO train achieved the highest overall removals: 97.9% COD, 98.6% BOD₅, and 94.0% DOC. The overall removals of chloride and nitrate ions in this train were 92.5% and 68.5%, respectively. The results indicate that coagulation-assisted ceramic membrane filtration followed by RO can substantially improve permeate quality. The novelty of the work lies in linking coagulation-assisted ceramic membrane filtration and RO polishing with particle-size and electrokinetic characterization, thereby clarifying the role of each treatment barrier and identifying an effective laboratory-scale train for upgrading high-strength brewery wastewater. Full article

(This article belongs to the Special Issue Selected Papers from Water, Wastewater, Waste—Infrastructure and Technology Conference 2026)

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