Membranes

22 pages, 3747 KB

Open AccessEditor’s ChoiceArticle

Recycled Polystyrene as a Sustainable Material for Hollow Fiber Membranes in Dye Filtration

by Mauricio Huhn-Ibarra, Libia Madai Itza-Uitzil, Marcial Yam-Cervantes, Abigail González-Díaz, Fernando José Zapata-Catzin, Javier Ivan Cauich-Cupul, Manuel Aguilar-Vega and Maria Ortencia González-Díaz

Membranes 2025, 15(10), 285; https://doi.org/10.3390/membranes15100285 - 23 Sep 2025

Viewed by 1139

Abstract

Expanded polystyrene (EPS) waste was chemically modified by sulfonation to obtain sulfonated EPS (sEPS), which was subsequently blended with virgin polyphenylsulfone (PPSU) at concentrations ranging from 10 to 50% to elaborate hollow fiber membranes for dye removal. The membranes were elaborated by non-solvent-induced [...] Read more.

Expanded polystyrene (EPS) waste was chemically modified by sulfonation to obtain sulfonated EPS (sEPS), which was subsequently blended with virgin polyphenylsulfone (PPSU) at concentrations ranging from 10 to 50% to elaborate hollow fiber membranes for dye removal. The membranes were elaborated by non-solvent-induced phase separation and characterized by scanning electron microscopy, mechanical properties, antifouling, water flux measurements, and dye rejection performance. Scanning electron microscopy images of PPSU/sEPS blends showed well-defined membrane cross-sections with no polymer segregation up to 30% recycled EPS content, indicating improved compatibility due to EPS sulfonation. The HFMs present mean pore radii ranging from 4.2 ± 0.5 to 11.1 ± 1.0 nm with porosity up to 80%. Water flux improved significantly from 3.1 to 21.2 L m⁻² h⁻¹ at 2 bar as sEPS content increased. Dye rejection performance was promising, with Reactive Black 5 rejection ranging from 77% to 99%. The 80/20s PPSU/sEPS membrane showed the highest Reactive Black 5 rejection at 98.3% and revealed a 70.3% rejection in a 24 h dye mixture test. Furthermore, the 70/30s displayed superior anti-fouling properties, achieving a 99.3% flux recovery ratio in a xanthan gum solution at 2 bar. This study demonstrates a novel approach to transform EPS waste into high-performance hollow fiber membrane with competitive antifouling and dye separation properties. Full article

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

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22 pages, 4596 KB

Open AccessEditor’s ChoiceReview

Microwave Synthesis in Zeolite and MOF Membranes

by Liangqing Li

Membranes 2025, 15(9), 275; https://doi.org/10.3390/membranes15090275 - 12 Sep 2025

Viewed by 1346

Abstract

Zeolites and metal–organic frameworks (MOFs) are crystalline porous materials characterized by highly ordered pore structures. Their fabrication into membranes has demonstrated significant potential for use in separation processes involving liquids or gases. Traditional methods for synthesizing these membranes often require prolonged reaction times [...] Read more.

Zeolites and metal–organic frameworks (MOFs) are crystalline porous materials characterized by highly ordered pore structures. Their fabrication into membranes has demonstrated significant potential for use in separation processes involving liquids or gases. Traditional methods for synthesizing these membranes often require prolonged reaction times and high energy input. In contrast, microwave heating technology has gained increasing attention as a more efficient approach for the synthesis of zeolite and MOF membranes, offering advantages such as rapid and uniform heating, enhanced energy efficiency, and greater environmental sustainability. This review focuses on fundamental research and laboratory-scale studies on the microwave-assisted synthesis of zeolite and MOF membranes. It begins by outlining the principles of microwave heating, emphasizing the mechanisms that enable accelerated heating. The discussion then highlights the key features and advantages of microwave synthesis in membrane fabrication, including reduced synthesis times, thinner membrane layers, suppression of impurities and undesired phases, and enhanced membrane density. Recent advancements in this area are also presented, particularly strategies for optimizing microwave heating processes, such as the use of single-mode microwave systems and precise control of heating rates. Notably, optimized microwave synthesis with controlled heating rates has been shown to reduce crystallization time by approximately 69%, decrease membrane thickness by nearly 70%, and improve pervaporation flux for acetic acid dehydration by more than 70%, compared with conventional microwave synthesis of mordenite membranes. Finally, the review summarizes and presents future perspectives aimed at promoting continued research and refinement of synthesis strategies in this promising area. Full article

(This article belongs to the Special Issue Design, Synthesis, and Application of Inorganic Membranes)

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40 pages, 4676 KB

Open AccessEditor’s ChoiceReview

Recent Developments in Polymer Inclusion Membranes: Advances in Selectivity, Structural Integrity, Environmental Applications and Sustainable Fabrication

by Anna Nowik-Zając and Vira Sabadash

Membranes 2025, 15(8), 249; https://doi.org/10.3390/membranes15080249 - 19 Aug 2025

Cited by 4 | Viewed by 3030

Abstract

Polymer inclusion membranes (PIMs) have undergone substantial advancements in their selectivity and efficiency, driven by their increasing deployment in separation processes, environmental remediation, and sensing applications. This review presents recent progress in the development of PIMs, focusing on strategies to enhance ion and [...] Read more.

Polymer inclusion membranes (PIMs) have undergone substantial advancements in their selectivity and efficiency, driven by their increasing deployment in separation processes, environmental remediation, and sensing applications. This review presents recent progress in the development of PIMs, focusing on strategies to enhance ion and molecule selectivity through the incorporation of novel carriers, including ionic liquids and task-specific extractants, as well as through polymer functionalization techniques. Improvements in mechanical and chemical stability, achieved via the utilization of high-performance polymers such as polyvinylidene fluoride (PVDF) and polyether ether ketone (PEEK), as well as cross-linking approaches, are critically analyzed. The expanded application of PIMs in the removal of heavy metals, organic micropollutants, and gas separation, particularly for carbon dioxide capture, is discussed with an emphasis on efficiency and operational robustness. The integration of PIMs with electrochemical and optical transduction platforms for sensor development is also reviewed, highlighting enhancements in sensitivity, selectivity, and response time. Furthermore, emerging trends towards the fabrication of sustainable PIMs using biodegradable polymers and green solvents are evaluated. Advances in scalable manufacturing techniques, including phase inversion and electrospinning, are addressed, outlining pathways for the industrial translation of PIM technologies. The review concludes by identifying current limitations and proposing future research directions necessary to fully exploit the potential of PIMs in industrial and environmental sectors. Full article

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

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52 pages, 2709 KB

Open AccessEditor’s ChoiceReview

Review of Hollow Fiber Membranes for Gas Separation: Exploring Fundamentals and Recent Advancements

by Valentina Grosso, Carmen Rizzuto, Elena Tocci, Alessio Fuoco, Mariagiulia Longo, Marcello Monteleone, Pegah Hajivand, Johannes C. Jansen and Elisa Esposito

Membranes 2025, 15(8), 246; https://doi.org/10.3390/membranes15080246 - 11 Aug 2025

Cited by 2 | Viewed by 5870

Abstract

Hollow fiber membranes have revolutionized various gas separation processes due to their unique characteristics such as high surface area, small system footprint, and high energy efficiency compared to flat sheet or spiral wound membranes. This review analyzes the current state of the art [...] Read more.

Hollow fiber membranes have revolutionized various gas separation processes due to their unique characteristics such as high surface area, small system footprint, and high energy efficiency compared to flat sheet or spiral wound membranes. This review analyzes the current state of the art of hollow fiber technology, exploring its diverse applications across various fields. Over the past ten years, research has primarily focused on improving hollow fiber fabrication techniques, including phase inversion, electrospinning, and 3D printing, highlighting their impact on membrane performance and selectivity. Furthermore, we discuss the challenges and future perspectives of hollow fiber technology, focusing on the development of novel materials and surface modifications to enhance membrane durability and efficiency. Finally, this review provides an overview of current gas separation techniques, spanning both conventional and next-generation methods, based on the foreseen field of exploitation of hollow fiber membranes. Full article

(This article belongs to the Special Issue Hollow Fiber Membranes for Gas and Vapor Separation: Fundamentals, State-of-the-Art, and Recent Advancements)

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14 pages, 2427 KB

Open AccessEditor’s ChoiceArticle

Enhanced Tangential Flow Filtration of Precipitated Proteins Using Screened Membrane Cassettes

by Zachary Badinger, Ali Behboudi and Andrew L. Zydney

Membranes 2025, 15(8), 245; https://doi.org/10.3390/membranes15080245 - 11 Aug 2025

Viewed by 2793

Abstract

Background: Recent advances in cell culture have led to significant increases in monoclonal antibody (mAb) titers, opening a new window of opportunity for developing a fully continuous downstream purification process based on the selective precipitation of the mAb from harvested cell culture fluid, [...] Read more.

Background: Recent advances in cell culture have led to significant increases in monoclonal antibody (mAb) titers, opening a new window of opportunity for developing a fully continuous downstream purification process based on the selective precipitation of the mAb from harvested cell culture fluid, with the precipitate dewatered and washed using single-pass tangential flow filtration (SPTFF) with microfiltration membranes. Methods: Experiments were performed with precipitates of human serum immunoglobulin G formed using ZnCl₂ and polyethylene glycol, both with and without added disodium malonate. SPTFF was conducted in both hollow fiber and screened cassette modules, with the critical flux identified using flux-stepping experiments. Results: Critical fluxes as high as 250 L/m²/h were obtained in the screened cassette, significantly higher than what was possible in hollow fiber modules. A two-stage system was designed that provided up to 85% conversion in a single pass. This system could be operated continuously for 24 h with 80% conversion at a filtrate flux of 144 L/m²/h without any significant fouling. Conclusions: The results demonstrate the potential of using screened membrane cassettes for the continuous/intensified processing of precipitated proteins like monoclonal antibodies. Full article

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

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24 pages, 2930 KB

Open AccessEditor’s ChoiceArticle

Improved Antimicrobial Properties of White Wastewater Protein Hydrolysate Through Electrodialysis with an Ultrafiltration Membrane (EDUF)

by Diala Damen, Jacinthe Thibodeau, Sami Gaaloul, Steve Labrie, Safia Hamoudi and Laurent Bazinet

Membranes 2025, 15(8), 238; https://doi.org/10.3390/membranes15080238 - 6 Aug 2025

Viewed by 1413

Abstract

This study investigated white wastewater (WW) as a potential source of antimicrobial peptides, employing hydrolysis with Pronase E followed by separation through electrodialysis with ultrafiltration membranes (EDUF) to increase the value of dairy components within a circular economy framework. The WW hydrolysate was [...] Read more.

This study investigated white wastewater (WW) as a potential source of antimicrobial peptides, employing hydrolysis with Pronase E followed by separation through electrodialysis with ultrafiltration membranes (EDUF) to increase the value of dairy components within a circular economy framework. The WW hydrolysate was divided into two key fractions: the cationic recovery compartment (CRC) and the anionic recovery compartment (ARC). The EDUF process effectively separated peptides, with peptide migration rates reaching 6.83 ± 0.59 g/m²·h for CRC and 6.19 ± 0.66 g/m²·h for ARC. Furthermore, relative energy consumption (REC) increased from 1.15 Wh/g to 2.05 Wh/g over three hours, in line with trends observed in recent studies on electrodialysis energy use. Although 29 peptides were statistically selected from the CRC (20) and ARC (9) compartments, no antibacterial activity was exhibited against Clostridium tyrobutyricum and Pseudomonas aeruginosa; however, antifungal activity was observed in the feed and ARC compartments. Peptides from the ARC demonstrated activity against Mucor racemosus (MIC = 0.156 mg/mL) and showed selective antifungal effects against Penicillium commune (MIC = 0.156 mg/mL). This innovative approach paves the way for improving the recovery of anionic peptides through further optimization of the EDUF process. Future perspectives include synthesizing selected peptides and evaluating their antifungal efficacy against these and other microbial strains, offering exciting potential for applications in food preservation and beyond. Full article

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

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38 pages, 9212 KB

Open AccessEditor’s ChoiceReview

Advanced Materials-Based Nanofiltration Membranes for Efficient Removal of Organic Micropollutants in Water and Wastewater Treatment

by Haochun Wei, Haibiao Nong, Li Chen and Shiyu Zhang

Membranes 2025, 15(8), 236; https://doi.org/10.3390/membranes15080236 - 5 Aug 2025

Cited by 4 | Viewed by 2494

Abstract

The increasing use of pharmaceutically active compounds (PhACs), endocrine-disrupting compounds (EDCs), and personal care products (PCPs) has led to the widespread presence of organic micropollutants (OMPs) in aquatic environments, posing a significant global challenge for environmental conservation. In recent years, advanced materials-based nanofiltration [...] Read more.

The increasing use of pharmaceutically active compounds (PhACs), endocrine-disrupting compounds (EDCs), and personal care products (PCPs) has led to the widespread presence of organic micropollutants (OMPs) in aquatic environments, posing a significant global challenge for environmental conservation. In recent years, advanced materials-based nanofiltration (NF) technologies have emerged as a promising solution for water and wastewater treatment. This review begins by examining the sources of OMPs, as well as the risk of OMPs. Subsequently, the key criteria of NF membranes for OMPs are discussed, with a focus on the roles of pore size, charge property, molecular interaction, and hydrophilicity in the separation performance. Against that background, this review summarizes and analyzes recent advancements in materials such as metal organic frameworks (MOFs), covalent organic frameworks (COFs), graphene oxide (GO), MXenes, hybrid materials, and environmentally friendly materials. It highlights the porous nature and structural diversity of organic framework materials, the advantage of inorganic layered materials in forming controllable nanochannels through stacking, the synergistic effects of hybrid materials, and the importance of green materials. Finally, the challenges related to the performance optimization, scalable fabrication, environmental sustainability, and complex separation of advanced materials-based membranes for OMP removal are discussed, along with future research directions and potential breakthroughs. Full article

(This article belongs to the Special Issue Design and Characterization of Nanofiltration Membranes for Water/Wastewater Treatment)

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14 pages, 6077 KB

Open AccessEditor’s ChoiceArticle

Fabrication of Green PVDF/TiO₂ Composite Membrane for Water Treatment

by Shuhang Lu and Dong Zou

Membranes 2025, 15(7), 218; https://doi.org/10.3390/membranes15070218 - 21 Jul 2025

Cited by 4 | Viewed by 1520

Abstract

PVDF/TiO₂ composite membranes show some potential to be used for water treatment as they combine the advantages of polymers and ceramics. However, conventional PVDF-based composite membranes are always fabricated by using conventional toxic solvents. Herein, PolarClean was used as a green solvent [...] Read more.

PVDF/TiO₂ composite membranes show some potential to be used for water treatment as they combine the advantages of polymers and ceramics. However, conventional PVDF-based composite membranes are always fabricated by using conventional toxic solvents. Herein, PolarClean was used as a green solvent to fabricate PVDF/TiO₂ composite membranes via the phase inversion method. In this process, Pluronic F127 was used as a dispersion agent to distribute TiO₂ particles in the PVDF matrix and to serve as a pore former on the membrane surface. TiO₂ particles were well distributed on the membrane surface and bulk. TiO₂ particles in the PVDF matrix enhanced the mechanical strength and hydrophilic characteristics of the resulting composite membrane, facilitating water transport through the composite membranes and enhancing their water permeability. Membrane microstructures and mechanical strength of the composite membranes were finely tuned by varying the PVDF concentration, TiO₂ concentration, and coagulation bath temperature. It was demonstrated that the resulting green PVDF/TiO₂ composite membrane showed a high water permeance compared with those using conventional toxic solvents in terms of its small pore size. In addition, the particle rejection of green PVDF/TiO₂ membrane showed a 99.9% rejection rate in all the filtration process, while those using NMP showed 91.1% after 30 min of filtration. The water flux was similar at 121 and 130 Lm⁻²h⁻¹ for green and conventional solvents, respectively. This work provides important information for the future application of sustainable membranes. Full article

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

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21 pages, 4609 KB

Open AccessEditor’s ChoiceReview

Covalent Organic Framework Membranes for Ion Separation: A Review

by Yutong Lou, Zhanyong Wang, Wanbei Yang, Shuchen Lang, Jiaxing Fan, Qiaomei Ke, Rui Wang, Zhen Zhang, Wentao Chen and Jian Xue

Membranes 2025, 15(7), 211; https://doi.org/10.3390/membranes15070211 - 15 Jul 2025

Viewed by 3369

Abstract

Covalent organic framework (COF) membranes have garnered significant attention in ion separation due to their high surface area, tunable pore size, excellent stability, and diverse functional groups. Over the past decade, various synthesis methods, such as solvothermal synthesis, interfacial synthesis, microwave-assisted solvothermal synthesis, [...] Read more.

Covalent organic framework (COF) membranes have garnered significant attention in ion separation due to their high surface area, tunable pore size, excellent stability, and diverse functional groups. Over the past decade, various synthesis methods, such as solvothermal synthesis, interfacial synthesis, microwave-assisted solvothermal synthesis, and in situ growth, have been developed to fabricate COF membranes. COF membranes have demonstrated remarkable ion separation performance in different separation processes driven by pressure, electric field, and vapor pressure difference, showing great potential in a wide range of applications. Nevertheless, challenges in the synthesis and application of COF membranes still remain, requiring further research to fully realize their potential in ion separation. This review critically examines the development of COF membranes, from synthesis methods to ion separation applications. We evaluate the advantages and limitations of various synthesis techniques and systematically summarize COF membrane performance based on separation driving forces. Finally, we present a critical analysis of current challenges and offer perspectives on promising future research directions for advancing COF membrane technology in separation. Full article

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

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24 pages, 1083 KB

Open AccessEditor’s ChoiceReview

Membrane-Based CO₂ Capture Across Industrial Sectors: Process Conditions, Case Studies, and Implementation Insights

by Jin Woo Park, Soyeon Heo, Jeong-Gu Yeo, Sunghoon Lee, Jin-Kuk Kim and Jung Hyun Lee

Membranes 2025, 15(7), 200; https://doi.org/10.3390/membranes15070200 - 2 Jul 2025

Cited by 5 | Viewed by 7601

Abstract

Membrane-based CO₂ capture has emerged as a promising technology for industrial decarbonization, offering advantages in energy efficiency, modularity, and environmental performance. This review presents a comprehensive assessment of membrane processes applied across major emission-intensive sectors, including power generation, cement, steelmaking, and biogas [...] Read more.

Membrane-based CO₂ capture has emerged as a promising technology for industrial decarbonization, offering advantages in energy efficiency, modularity, and environmental performance. This review presents a comprehensive assessment of membrane processes applied across major emission-intensive sectors, including power generation, cement, steelmaking, and biogas upgrading. Drawing from pilot-scale demonstrations and simulation-based studies, we evaluate how flue gas characteristics, such as CO₂ concentration, pressure, temperature, and impurity composition, govern membrane selection, process design, and operational feasibility. Case studies highlight the technical viability of membrane systems under a wide range of industrial conditions, from low-CO₂ NGCC flue gas to high-pressure syngas and CO₂-rich cement emissions. Despite these advances, this review discusses the key remaining challenges for the commercialization of membrane-based CO₂ capture and includes perspectives on process design and techno-economic evaluation. The insights compiled in this review are intended to support the design of application-specific membrane systems and guide future efforts toward scalable and economically viable CO₂ capture across industrial sectors. Full article

(This article belongs to the Special Issue Novel Membranes for Carbon Capture and Conversion)

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22 pages, 3169 KB

Open AccessEditor’s ChoiceReview

A Mini-Review on Electrocatalytic Self-Cleaning Membrane Materials for Sustainable Fouling Control

by Honghuan Yin and Zhonglong Yin

Membranes 2025, 15(7), 191; https://doi.org/10.3390/membranes15070191 - 25 Jun 2025

Cited by 1 | Viewed by 1573

Abstract

Although membrane technology has been widely applied in water treatment, membrane fouling is an inevitable issue that has largely limited its application. Benefiting from the advantages of green power, easy integration and low chemical consumption, electrocatalytic membrane (ECM) technology received attention, using it [...] Read more.

Although membrane technology has been widely applied in water treatment, membrane fouling is an inevitable issue that has largely limited its application. Benefiting from the advantages of green power, easy integration and low chemical consumption, electrocatalytic membrane (ECM) technology received attention, using it to enable electrically driven self-cleaning performance recently, making it highly desirable for sustainable fouling control. In this work, we comprehensively summarized the conventional (e.g., carbonaceous materials, metal and metal oxide) and emerging (e.g., metal–organic framework and MXene) materials for the fabrication of an ECM. Then the fabrication methods and operating modes of an ECM were emphasized. Afterwards, the application of different ECM materials in membrane fouling control was highlighted and the corresponding mechanism was revealed. Based on existing research findings, we proposed the challenges and future prospects of ECM materials for practical application. This study provides enlightening knowledge into the development of ECM materials for sustainable fouling control. Full article

(This article belongs to the Special Issue New Advances in Membrane Separation Technology for Water Pollution Control and Membrane Fouling Mitigation)

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11 pages, 1035 KB

Open AccessEditor’s ChoiceArticle

Electrodialysis Using Zero-Gap Electrodes Producing Concentrated Product Without Significant Solution Resistance Losses

by W. Henry Freer, Charles Perks, Charles Codner and Paul A. Kohl

Membranes 2025, 15(6), 186; https://doi.org/10.3390/membranes15060186 - 19 Jun 2025

Cited by 1 | Viewed by 1174

Abstract

Electrochemical separations use an ionic current to drive the flow of ions across an ion exchange membrane to produce dilute and concentrated streams. The economics of these systems is challenging because passing an ionic current through a dilute solution often requires a small [...] Read more.

Electrochemical separations use an ionic current to drive the flow of ions across an ion exchange membrane to produce dilute and concentrated streams. The economics of these systems is challenging because passing an ionic current through a dilute solution often requires a small cell gap to lower the ionic resistance and the use of a low current density to minimize the voltage drop across the dilute product stream. Lower salt concentration in the product stream improves the fraction of the salt recovered but increases the electricity cost due to high ohmic losses. The electricity cost is managed by lowering the current density which greatly increases the balance of the plant. The cell configuration demonstrated in this study eliminates the need to pass an ionic current through the diluted product stream. Ionic current passes only through the concentrated product stream, which allows use of high current density and smaller balance of the plant. The cell has three chambers with an anion and cation membrane separating the cathode and anode, respectively, from the concentrated product solution. The device uses zero-gap membrane electrode assemblies to improve the cell voltage and system performance. As ions concentrate in the center compartment, the solution resistance decreases, and the product is recovered with a lower voltage penalty compared to traditional electrodialysis. This lower voltage drop allows for faster feed flow rates and higher current density. Additionally, the larger cell gap for the product provides opportunities for systems with solids suspended in solution. It was found that the ion collection efficiency increased with current due to enhanced convective mass transfer in the feed streams. Full article

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

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35 pages, 16650 KB

Open AccessEditor’s ChoiceArticle

Membrane Charge Effects on Solute Transport in Nanofiltration: Experiments and Molecular Dynamics Simulations

by Suwei Liu, Zihao Foo, John H. Lienhard, Sinan Keten and Richard M. Lueptow

Membranes 2025, 15(6), 184; https://doi.org/10.3390/membranes15060184 - 18 Jun 2025

Cited by 1 | Viewed by 1719

Abstract

Polyamide membranes, such as nanofiltration (NF) membranes, are widely used for water purification. However, the mechanisms of solute transport and solute rejection due to solute charge interactions with the membrane remain unclear at the molecular level. Here, we use molecular dynamics simulations to [...] Read more.

Polyamide membranes, such as nanofiltration (NF) membranes, are widely used for water purification. However, the mechanisms of solute transport and solute rejection due to solute charge interactions with the membrane remain unclear at the molecular level. Here, we use molecular dynamics simulations to examine the transport of single-solute feeds through charged nanofiltration membranes with different membrane charge concentrations of

{COO}^{-}

and NH

{}_{2}^{+}

resulting from the deprotonation or protonation of polymeric end groups according to the pH level that the membrane experiences. The results show that

{Na}^{+}

and

{Cl}^{-}

solute ions are better rejected when the membrane has a higher concentration of negatively charged groups, corresponding to a higher pH, whereas

{CaCl}_{2}

is well rejected at all pH levels studied. These results are consistent with those of experiments performed at the same pH conditions as the simulation setup. Moreover, solute transport behavior depends on the membrane functional group distribution. When

{COO}^{-}

functional groups are concentrated at membrane feed surface, ion permeation into the membrane is reduced. Counter-ions tend to associate with charged functional groups while co-ions seem to pass by the charged groups more easily. In addition, steric effects play a role when ions of opposite charge cluster in pores of the membrane. This study reveals solute transport and rejection mechanisms related to membrane charge and provides insights into how membranes might be designed to achieve specific desired solute rejection. Full article

(This article belongs to the Special Issue Nanofiltration Membranes: Preparation, Structure and Separation Performance)

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12 pages, 7533 KB

Open AccessEditor’s ChoiceArticle

Determining Accurate Pore Structures of Polypropylene Membrane for ECMO Using FE-SEM Under Optimized Conditions

by Makoto Fukuda, Yoshiaki Nishite, Eri Murata, Koki Namekawa, Tomohiro Mori, Tsutomu Tanaka and Kiyotaka Sakai

Membranes 2025, 15(6), 174; https://doi.org/10.3390/membranes15060174 - 9 Jun 2025

Viewed by 1408

Abstract

Long-term ECMOs are expected to be put into practical use in order to prepare for the next emerging severe infectious diseases after the novel coronavirus pandemic in 2019–2023. While polypropylene (PP) and polymethylpentene (PMP) are currently the mainstream materials for the hollow fiber [...] Read more.

Long-term ECMOs are expected to be put into practical use in order to prepare for the next emerging severe infectious diseases after the novel coronavirus pandemic in 2019–2023. While polypropylene (PP) and polymethylpentene (PMP) are currently the mainstream materials for the hollow fiber membranes of ECMO, the PP membrane coated with a silicone layer on the outer surface has also been commercialized. In this study, we sought a method to accurately observe the detailed pore morphologies of the PP membrane by suppressing irreversible changes in the morphology in SEM observation, which is a general-purpose observation with higher resolution. As a result, the convex surface morphologies of the PP membrane, which was a non-conductive porous structure, were confirmed in detail by utilizing the lower secondary electron image (LEI) mode (FE-SEM, JSM-7610F, JEOL Ltd., Tokyo, Japan) at low acceleration voltage, low magnification, and long working distance, to minimize morphological alterations caused by osmium (Os) sputtering. On the other hand, although the sputter-coating on non-conductive samples is mandatory for imaging morphologies with SEM, the non-sputtering method is also worthwhile for porous and fragile structures such as this sample to minimize morphological alterations. Furthermore, we propose a method to confirm the morphology of the deep part of the sample by utilizing the secondary electron image (SEI) mode at an appropriate acceleration voltage and high magnification with higher resolution. Full article

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

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46 pages, 4813 KB

Open AccessEditor’s ChoiceReview

Overcoming the Limitations of Forward Osmosis and Membrane Distillation in Sustainable Hybrid Processes Managing the Water–Energy Nexus

by Muhammad Suleman, Basel Al-Rudainy and Frank Lipnizki

Membranes 2025, 15(6), 162; https://doi.org/10.3390/membranes15060162 - 26 May 2025

Cited by 4 | Viewed by 7423

Abstract

Energy-efficient and cost-effective water desalination systems can significantly replenish freshwater reserves without further stressing limited energy resources. Currently, the majority of the desalination systems are operated by non-renewable energy sources such as fossil fuel power plants. The viability of any desalination process depends [...] Read more.

Energy-efficient and cost-effective water desalination systems can significantly replenish freshwater reserves without further stressing limited energy resources. Currently, the majority of the desalination systems are operated by non-renewable energy sources such as fossil fuel power plants. The viability of any desalination process depends primarily on the type and amount of energy it utilizes and on the product recovery. In recent years, membrane distillation (MD) and forward osmosis (FO) have drawn the attention of the scientific community because of FO’s low energy demand and the potential of MD operation with low-grade heat or a renewable source like geothermal, wind, or solar energy. Despite the numerous potential advantages of MD and FO, there are still some limitations that negatively affect their performance associated with the water–energy nexus. This critical review focuses on the hybrid forward osmosis–membrane distillation (FO-MD) processes, emphasizing energy demand and product quality. It starts with exploring the limitations of MD and FO as standalone processes and their performance. Based on this, the importance of combining these technologies into an FO-MD hybrid process and the resulting strengths of it will be demonstrated. The promising applications of this hybrid process and their advantages will be also explored. Furthermore, the performance of FO-MD processes will be compared with other hybrid processes like FO–nanofiltration (FO-NF) and FO–reverse osmosis (FO-RO). It will be outlined how the FO-MD hybrid process could outperform other hybrid processes when utilizing a low-grade heat source. In conclusion, it will be shown that the FO-MD hybrid process can offer a sustainable solution to address water scarcity and efficiently manage the water–energy nexus. Full article

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

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12 pages, 2694 KB

Open AccessEditor’s ChoiceArticle

In-Situ Measurement of Gas Permeability for Membranes in Water Electrolysis

by Shuaimin Li, Chuan Song, Li Xu, Yuxin Wang and Wen Zhang

Membranes 2025, 15(5), 147; https://doi.org/10.3390/membranes15050147 - 13 May 2025

Viewed by 1679

Abstract

Water electrolysis (WE) is a green technology for producing hydrogen gas without the emission of carbon dioxide. The ideal membrane materials in WE should be capable of transporting ions quickly and have gas barrier properties in harsh work environments. However, currently, no desirable [...] Read more.

Water electrolysis (WE) is a green technology for producing hydrogen gas without the emission of carbon dioxide. The ideal membrane materials in WE should be capable of transporting ions quickly and have gas barrier properties in harsh work environments. However, currently, no desirable measurement method has been developed for evaluating the gas barrier behavior of the membranes. Hence, an in-situ electrochemical method is developed to measure the gas permeability of membranes in the actual electrolysis environment, with the supersaturated state of H₂ in the electrolyte and H₂ bubbles during the electrolysis process. Four membranes, including Zirfon (a state-of-the-art alkaline WE membrane), polyphenylene sulfide fabric (PPS, a commercial alkaline WE membrane), FAA-3-PK-75 (a commercial anion-exchange membrane), and BILP-PE (a home-made composite membrane) were employed as the standard samples to perform the electrochemical measurement under different current densities, temperatures, and electrolyte concentrations. The results show that an increase in electrolytic current density or temperature or a decrease in KOH concentration can increase the H₂ permeability of the membrane. The two porous membranes, Zirfon and PPS, are more affected by the current density and KOH concentration, while the dense FAA-3-PK-75 and BILP-PE membranes have a stronger ability to hinder H₂ permeation. Under the conditions of 80 °C, 30 wt.% KOH, 101 kPa, and 400 mA·cm⁻², the hydrogen permeability (×10¹⁰ L·cm·cm⁻²·s⁻¹) of Zirfon, PPS, FAA, and BILP-PE are 263, 367, 28.3, and 5.32, respectively. Full article

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

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15 pages, 4044 KB

Open AccessEditor’s ChoiceArticle

Development and Application of a Novel Ultrafiltration Membrane for Efficient Removal of Dibutyl Phthalate from Wastewater

by Qiang Zhou, Meiling Chen, Yushan Jiang, Linnan Zhang and Yanhong Wang

Membranes 2025, 15(5), 142; https://doi.org/10.3390/membranes15050142 - 7 May 2025

Cited by 1 | Viewed by 1520

Abstract

This study successfully developed a novel molecularly imprinted ultrafiltration membrane (MIUM) for energy-efficient and selective removal of dibutyl phthalate (DBP) from wastewater. Guided by Gaussian simulations, methacrylic acid (MAA) was identified as the optimal functional monomer, achieving the strongest binding energy (ΔE = [...] Read more.

This study successfully developed a novel molecularly imprinted ultrafiltration membrane (MIUM) for energy-efficient and selective removal of dibutyl phthalate (DBP) from wastewater. Guided by Gaussian simulations, methacrylic acid (MAA) was identified as the optimal functional monomer, achieving the strongest binding energy (ΔE = −0.0698 a.u.) with DBP at a 1:6 molar ratio, providing a foundation for precise cavity construction. DBP-imprinted polymers (MIPs) synthesized via bulk polymerization were integrated into polysulfone membranes through phase inversion. The optimized MIUM (81.27% polymer content) exhibited exceptional performance under low-pressure operation (0.2 MPa), with a water flux of 111.49 L·m²·h⁻¹ and 92.87% DBP rejection, representing a 43% energy saving compared to conventional nanofiber membranes requiring 0.4 MPa. Structural characterization confirmed synergistic effects between imprinted cavities and membrane transport properties as the key mechanism for efficient separation. Notably, MIUM demonstrated remarkable selectivity, achieving 91.57% retention for DBP while showing limited affinity for structurally analogous phthalates (e.g., diethyl/diisononyl phthalates). The membrane maintained > 70% retention after 10 elution cycles, highlighting robust reusability. These findings establish a paradigm for molecular simulation-guided design of selective membranes, offering an innovative solution for low-energy removal of endocrine disruptors. The work advances wastewater treatment technologies by balancing high permeability, targeted pollutant removal, and operational sustainability, with direct implications for mitigating environmental risks and improving water quality management. Full article

(This article belongs to the Special Issue Membrane Distillation and Other Membrane-Related Applications for Water Cleaning and Desalination)

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13 pages, 34194 KB

Open AccessEditor’s ChoiceArticle

Restricted Surface Diffusion of Cytochromes on Bioenergetic Membranes with Anionic Lipids

by Aaron Chan and Emad Tajkhorshid

Membranes 2025, 15(4), 124; https://doi.org/10.3390/membranes15040124 - 13 Apr 2025

Viewed by 1257

Abstract

Bioenergetic membranes of mitochondria, thylakoids, and chromatophores are primary sites of ATP production in living cells. These membranes contain an electron transport chain (ETC) in which electrons are shuttled between a series of redox proteins during the generation of ATP via oxidative phosphorylation. [...] Read more.

Bioenergetic membranes of mitochondria, thylakoids, and chromatophores are primary sites of ATP production in living cells. These membranes contain an electron transport chain (ETC) in which electrons are shuttled between a series of redox proteins during the generation of ATP via oxidative phosphorylation. The phospholipid composition of these membranes, which often include negative lipids, plays a role in determining the electrostatics of their surface owing to the spatial distribution of their charged head groups. Cardiolipin (CDL) is a phospholipid commonly associated with bioenergetic membranes and is also a significant contributor to the negative surface charge. Interactions between cytochromes and phospholipid head groups in the membrane can in principle affect the rate of its travel between ETC components, hence influencing the rate of ATP turnover. Here, we use molecular dynamic (MD) simulations that feature an accelerated membrane model, termed highly mobile membrane mimetic (HMMM), to study protein–lipid interactions during the diffusion of cytochrome c₂ between redox partners in a bioenergetic membrane. We observe a “skipping” mode of diffusion for cytochromes along with a bias for binding to anionic lipids, particularly with a strong preference for CDL. During diffusion, cytochrome c₂ maintains a relatively fixed tilt with respect to the membrane normal with wider fluctuations in its angle with respect to the plane of the membrane. The obtained results describing the behavior of cytochrome c₂ on a representative bioenergetic membrane have direct ramifications in shuttling motions of other similar electron-carrying elements in other bioenergetic membranes, which are composed of a significant amount of anionic lipids. The mode of surface-restricted diffusion reported here would modulate rapid electron transfer between the ETC complexes anchored in bioenergetic membranes by reducing the search space between them. Full article

(This article belongs to the Section Biological Membranes)

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25 pages, 6238 KB

Open AccessEditor’s ChoiceArticle

Effect of Ultrasound on Dissolution of Polymeric Blends and Phase Inversion in Flat Sheet and Hollow Fiber Membranes for Ultrafiltration Applications

by Gilberto Katmandú Méndez-Valdivia, María De Lourdes Ballinas-Casarrubias, Guillermo González-Sánchez, Hugo Valdés, Efigenia Montalvo-González, Martina Alejandra Chacón-López, Emmanuel Martínez-Montaño, Beatriz Torrestiana-Sánchez, Herenia Adilene Miramontes-Escobar and Rosa Isela Ortiz-Basurto

Membranes 2025, 15(4), 120; https://doi.org/10.3390/membranes15040120 - 10 Apr 2025

Viewed by 1775

Abstract

In seeking alternatives for reducing environmental damage, fabricating filtration membranes using biopolymers derived from agro-industrial residues, such as cellulose acetate (CA), partially dissolved with green solvents, represents an economical and sustainable option. However, dissolving CA in green solvents through mechanical agitation can take [...] Read more.

In seeking alternatives for reducing environmental damage, fabricating filtration membranes using biopolymers derived from agro-industrial residues, such as cellulose acetate (CA), partially dissolved with green solvents, represents an economical and sustainable option. However, dissolving CA in green solvents through mechanical agitation can take up to 48 h. An ultrasonic probe was proposed to accelerate mass transfer and polymer dissolution via pulsed interval cavitation. Additionally, ultrasound-assisted phase inversion (UAPI) on the external coagulation bath was assessed to determine its influence on the properties of flat sheet and hollow fiber membranes during phase inversion. Results indicated that the ultrasonic pulses reduced dissolution time by up to 98% without affecting viscosity (3.24 ± 0.06 Pa·s), thermal stability, or the rheological behavior of the polymeric blend. UAPI increased water permeability in flat sheet membranes by 26% while maintaining whey protein rejection above 90%. For hollow fiber membranes, UAPI (wavelength amplitude of 0 to 20%) improved permeability by 15.7% and reduced protein retention from 90% to 70%, with MWCO between 68 and 240 kDa. This report demonstrates the effectiveness of ultrasonic probes for decreasing the dissolution time of dope solution with green cosolvents and its potential to change the structure of polymeric membranes by ultrasound-assisted phase inversion. Full article

(This article belongs to the Special Issue Membrane Processes for Water Recovery in Food Processing Industries)

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26 pages, 1509 KB

Open AccessEditor’s ChoiceReview

The State of the Art on PVDF Membrane Preparation for Membrane Distillation and Membrane Crystallization: Towards the Use of Non-Toxic Solvents

by Aqsa Mansoor Khan, Francesca Russo, Francesca Macedonio, Alessandra Criscuoli, Efrem Curcio and Alberto Figoli

Membranes 2025, 15(4), 117; https://doi.org/10.3390/membranes15040117 - 8 Apr 2025

Cited by 3 | Viewed by 4072

Abstract

Most parts of the earth are covered with water, but only 0.3% of it is available to living beings. Industrial growth, fast urbanization, and poor water management have badly affected the water quality. In recent years, a transition has been seen from the [...] Read more.

Most parts of the earth are covered with water, but only 0.3% of it is available to living beings. Industrial growth, fast urbanization, and poor water management have badly affected the water quality. In recent years, a transition has been seen from the traditional (physical, chemical) wastewater treatment methods towards a greener, sustainable, and scalable membrane technology. Even though membrane technology offers a green pathway to address the wastewater treatment issue on a larger scale, the fabrication of polymeric membranes from toxic solvents is an obstacle in making it a fully green method. The concept of green chemistry has encouraged scientists to engage in research for new biodegradable and non-protic solvents to replace with already existing toxic ones. This review outlines the use of non-toxic solvents for the preparation of PVDF membranes and their application in membrane distillation and membrane crystallization. Full article

(This article belongs to the Topic New Advances in Membrane Technology and Its Contribution to Sustainability)

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15 pages, 4409 KB

Open AccessEditor’s ChoiceArticle

Uncovering Key Parameters in Perfluorosulfonic Acid (PFSA) Membrane Fuel Cells to Enhance Performance

by Valdecir A. Paganin, Alan M. P. Sakita, Thiago Lopes, Edson A. Ticianelli and Joelma Perez

Membranes 2025, 15(3), 65; https://doi.org/10.3390/membranes15030065 - 20 Feb 2025

Cited by 2 | Viewed by 1943

Abstract

The conversion of chemical energy to electricity in proton exchange membrane fuel cells (PEMFCs) is essential for replacing fossil fuel engines and achieving net-zero CO₂ emissions. In the pursuit of more efficient PEMFCs, certain often-overlooked parameters significantly influence cell performance by either [...] Read more.

The conversion of chemical energy to electricity in proton exchange membrane fuel cells (PEMFCs) is essential for replacing fossil fuel engines and achieving net-zero CO₂ emissions. In the pursuit of more efficient PEMFCs, certain often-overlooked parameters significantly influence cell performance by either weakening the interaction between the catalytic layer (CL) and the membrane or restricting gas access to the CL. This study examines the effects of cell tightening and hot-pressing conditions on three similar-thickness perfluorosulfonic acid (PFSA) membranes: Aquivion^®, Fumapem, and Nafion^®. The results reveal that the hot-pressing method employing higher pressure and a lower temperature (125C method) yields lower fuel cell performance compared to the method utilizing a higher temperature and lower pressure (145C method). Furthermore, incorporating cellulose paper as a pressure homogenizer in the MEA preparation setup significantly improved current density by approximately 2.5 times compared to the traditional assembly method. Cyclic voltammetry with Ar-feed in the cathode showed that all prepared MEAs exhibited a similar platinum surface area; however, MEAs pressed at higher temperatures displayed slightly lower hydrogen desorption charge values. The torque applied to the bolts does not show a consistent trend in fuel cell performance, but optimal torque values can enhance PEMFC performance under certain conditions. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes in Energy Conversion and Storage)

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15 pages, 2733 KB

Open AccessEditor’s ChoiceArticle

Seawater Membrane Distillation Coupled with Alkaline Water Electrolysis for Hydrogen Production: Parameter Influence and Techno-Economic Analysis

by Xiaonan Xu, Zhijie Zhao, Chunfeng Song, Li Xu and Wen Zhang

Membranes 2025, 15(2), 60; https://doi.org/10.3390/membranes15020060 - 11 Feb 2025

Cited by 5 | Viewed by 3113

Abstract

The production of green hydrogen requires renewable electricity and a supply of sustainable water. Due to global water scarcity, using seawater to produce green hydrogen is particularly important in areas where freshwater resources are scarce. This study establishes a system model to simulate [...] Read more.

The production of green hydrogen requires renewable electricity and a supply of sustainable water. Due to global water scarcity, using seawater to produce green hydrogen is particularly important in areas where freshwater resources are scarce. This study establishes a system model to simulate and optimize the integrated technology of seawater desalination by membrane distillation and hydrogen production by alkaline water electrolysis. Technical economics is also performed to evaluate the key factors affecting the economic benefits of the coupling system. The results show that an increase in electrolyzer power and energy efficiency will reduce the amount of pure water. An increase in the heat transfer efficiency of the membrane distillation can cause the breaking of water consumption and production equilibrium, requiring a higher electrolyzer power to consume the water produced by membrane distillation. The levelized costs of pure water and hydrogen are US$1.28 per tonne and $1.37/kg H₂, respectively. The most important factors affecting the production costs of pure water and hydrogen are electrolyzer power and energy efficiency. When the price of hydrogen rises, the project’s revenue increases significantly. The integrated system offers excellent energy efficiency compared to conventional desalination and hydrogen production processes, and advantages in terms of environmental protection and resource conservation. Full article

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

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14 pages, 6671 KB

Open AccessEditor’s ChoiceArticle

A STEDable BF₂-Azadipyrromethene Fluorophore for Nuclear Membrane and Associated Endoplasmic Reticulum Imaging

by Anaïs C. Bourgès, Massimiliano Garre, Dan Wu and Donal F. O’Shea

Membranes 2025, 15(1), 9; https://doi.org/10.3390/membranes15010009 - 1 Jan 2025

Cited by 1 | Viewed by 4311

Abstract

The endoplasmic reticulum and the internal nuclear compartments are intrinsically connected through the nuclear membrane, pores and lamina. High resolution imaging of each of these cellular features concurrently remains a significant challenge. To that end we have developed a new molecular nuclear membrane-endoplasmic [...] Read more.

The endoplasmic reticulum and the internal nuclear compartments are intrinsically connected through the nuclear membrane, pores and lamina. High resolution imaging of each of these cellular features concurrently remains a significant challenge. To that end we have developed a new molecular nuclear membrane-endoplasmic reticulum (NM-ER) staining fluorophore with emission maxima at 650 nm. NM-ER is compatible with fixed and live cell imaging and stimulated emission depletion microscopy (STED) showing significant improvement in resolution when compared to comparable confocal laser scanning microscopy. The imaging versatility of NM-ER was illustrated through its compatible use with other fluorophores for co-imaging with DNA, nuclear pores and lamina allowing cellular abnormalities to be identified. NM-ER alone, or in use with other nuclear region labels could be an important tool for the investigation of nuclear transport and associated cellular processes. Full article

(This article belongs to the Section Biological Membranes)

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14 pages, 3524 KB

Open AccessEditor’s ChoiceArticle

Enhanced Performance and Durability of Pore-Filling Membranes for Anion Exchange Membrane Water Electrolysis

by Minyoung Lee and Jin-Soo Park

Membranes 2024, 14(12), 269; https://doi.org/10.3390/membranes14120269 - 12 Dec 2024

Cited by 7 | Viewed by 2834

Abstract

Four distinct pore-filling anion exchange membranes (PFAEMs) were prepared, and their mechanical properties, ion conductivity, and performance in anion exchange membrane water electrolysis (AEMWE) were evaluated. The fabricated PFAEMs demonstrated exceptional tensile strength, which was approximately 14 times higher than that of the [...] Read more.

Four distinct pore-filling anion exchange membranes (PFAEMs) were prepared, and their mechanical properties, ion conductivity, and performance in anion exchange membrane water electrolysis (AEMWE) were evaluated. The fabricated PFAEMs demonstrated exceptional tensile strength, which was approximately 14 times higher than that of the commercial membrane, despite being nearly half as thin. Ion conductivity measurements revealed that acrylamide-based membranes outperformed benzyl-based ones, exhibiting 25% and 41% higher conductivity when using crosslinkers with two and three crosslinking sites, respectively. The AEMWE performance directly correlated with the hydrophilicity and ion exchange capacity (IEC) of the membranes. Specifically, AE_3C achieved the highest performance, supported by its superior IEC and ionic conductivity. Durability tests showed that AE_3C outlasted the commercial membrane, with a delayed voltage increase corresponding to its higher IEC, confirming the importance of increased ion-exchange functional groups in ensuring longevity. These results highlight the critical role of hydrophilic monomers and crosslinker structure in optimizing PFAEMs for enhanced performance and durability in AEMWE applications. Full article

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

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15 pages, 4739 KB

Open AccessEditor’s ChoiceArticle

Fouling and Chemical Cleaning Strategies for Submerged Ultrafiltration Membrane: Synchronized Bench-Scale, Full-Scale, and Engineering Tests

by Xiwang Zhu, Chengyue Fan, Yichen Fang, Wenqing Yu, Yawei Xie and Hongyuan Liu

Membranes 2024, 14(12), 251; https://doi.org/10.3390/membranes14120251 - 26 Nov 2024

Cited by 3 | Viewed by 3887

Abstract

This study investigated membrane fouling issues associated with the operation of a submerged ultrafiltration membrane in a drinking water treatment plant (DWTP) and optimized the associated chemical cleaning strategies. By analyzing the surface components of the membrane foulant and the compositions of the [...] Read more.

This study investigated membrane fouling issues associated with the operation of a submerged ultrafiltration membrane in a drinking water treatment plant (DWTP) and optimized the associated chemical cleaning strategies. By analyzing the surface components of the membrane foulant and the compositions of the membrane cleaning solution, the primary causes of membrane fouling were identified. Membrane fouling control strategies suitable for the DWTP were evaluated through chemical cleaning tests conducted for bench-scale, full-scale, and engineering cases. The results show that the membrane foulants were primarily composed of a mixture of inorganics and organics; the inorganics were mainly composed of Al and Si, while the organics were primarily humic acid (HA). Sodium citrate proved to be the most effective cleaning agent for inorganic fouling, which was mainly composed of Al, whereas sodium hypochlorite (NaClO) combined with sodium hydroxide (NaOH) showed the best removal efficiency for organic fouling, which predominantly consisted of HA and Si. However, sodium hypochlorite (NaClO) combined with sodium hydroxide (NaOH) showed the best removal efficiency for organic fouling and Si; organic fouling predominantly consisted of HA. Based on the bench-scale test results, flux recovery was verified in the full-scale system. Under a constant pressure of 30 kPa, the combined acid–alkali cleaning achieved the best flux recovery, restoring the flux from 22.8 L/(m²·h) to 66.75 L/(m²·h). In the engineering tests, combined acid–alkali cleaning yielded results consistent with those of the full-scale tests. In the practical engineering cleaning process, adopting a cleaning strategy of alkaline (NaClO + NaOH) cleaning followed by acidic (sodium citrate) cleaning can effectively solve the membrane fouling problem. Full article

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

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16 pages, 4896 KB

Open AccessEditor’s ChoiceArticle

Enhancing the Separation Performance of Chitosan Membranes Through the Blending with Deep Eutectic Solvents for the Pervaporation of Polar/Non-Polar Organic Mixtures

by Francesco Galiano, Asma Msahel, Francesca Russo, Natalia Rovella, Alfonso Policicchio, Sofiane Ben Hamouda, Amor Hafiane, Roberto Castro-Muñoz and Alberto Figoli

Membranes 2024, 14(11), 237; https://doi.org/10.3390/membranes14110237 - 11 Nov 2024

Cited by 13 | Viewed by 2824

Abstract

This study explores the development of chitosan-based membranes blended with three distinct deep eutectic solvents (DESs) for the pervaporation separation of methanol and methyl tert-butyl ether. DESs were selected for their eco-friendly properties and their potential to enhance membrane performance. The chitosan [...] Read more.

This study explores the development of chitosan-based membranes blended with three distinct deep eutectic solvents (DESs) for the pervaporation separation of methanol and methyl tert-butyl ether. DESs were selected for their eco-friendly properties and their potential to enhance membrane performance. The chitosan (CS) membranes, both crosslinked and non-crosslinked, were characterized in terms of morphology, chemical composition, wettability, mechanical resistance, and solvent uptake. Pervaporation tests revealed that incorporating DESs significantly enhanced the membranes’ selective permeability toward methanol, with up to a threefold increase in separation efficiency compared to pristine CS membranes. The membranes demonstrated a strong dependence on feed temperature, with higher temperatures improving permeation flux but reducing separation factor. Crosslinking with glutaraldehyde further increased membrane selectivity by reducing free volume into the polymer matrix. These findings underscore the potential of DESs as green additives for improving the performance of biopolymer membranes, making them promising candidates for efficient and eco-friendly organic–organic separations. Full article

(This article belongs to the Special Issue Membranes for Energy and the Environment)

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13 pages, 5627 KB

Open AccessEditor’s ChoiceArticle

Organic Solvent Nanofiltration Membrane with In Situ Constructed Covalent Organic Frameworks as Separation Layer

by Fangyi Xu, Shuxin Zhao, Junjie Song, Yu Peng and Baowei Su

Membranes 2024, 14(11), 234; https://doi.org/10.3390/membranes14110234 - 8 Nov 2024

Cited by 3 | Viewed by 2264

Abstract

Organic solvent nanofiltration (OSN) technology is advantageous for separating mixtures of organic solutions owing to its low energy consumption and environmental friendliness. Covalent organic frameworks (COFs) are good candidates for enhancing the efficiency of solvent transport and ensuring precise molecular sieving of OSN [...] Read more.

Organic solvent nanofiltration (OSN) technology is advantageous for separating mixtures of organic solutions owing to its low energy consumption and environmental friendliness. Covalent organic frameworks (COFs) are good candidates for enhancing the efficiency of solvent transport and ensuring precise molecular sieving of OSN membranes. In this study, p-phenylenediamine (Pa) and 1,3,5-trimethoxybenzene (Tp) are used to construct, in situ, a TpPa COF skin layer via interfacial polymerization (IP) on a polyimide substrate surface. After subsequent crosslinking and activation steps, a kind of TpPa/polyimide (PI) OSN membrane is obtained. Under optimized fabrications, this OSN membrane exhibits an ethanol permeance of 58.0 LMH/MPa, a fast green FCF (FGF) rejection of 96.2%, as well as a pure n-hexane permeance of 102.0 LMH/MPa. Furthermore, the TpPa/PI OSN membrane exhibits good solvent resistance, which makes it suitable for the separation, purification, and concentration of organic solvents. Full article

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

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16 pages, 48253 KB

Open AccessEditor’s ChoiceArticle

Enhancing CO₂/N₂ and CO₂/CH₄ Separation Properties of PES/SAPO-34 Membranes Using Choline Chloride-Based Deep Eutectic Solvents as Additives

by Jonathan S. Cardoso, Zhi Lin, Paulo Brito and Licínio M. Gando-Ferreira

Membranes 2024, 14(11), 230; https://doi.org/10.3390/membranes14110230 - 5 Nov 2024

Cited by 3 | Viewed by 2408

Abstract

CO₂ separation is an important environmental method mainly used in reducing CO₂ emissions to mitigate anthropogenic climate change. The use of mixed-matrix membranes (MMMs) arrives as a possible answer, combining the high selectivity of inorganic membranes with high permeability of organic [...] Read more.

CO₂ separation is an important environmental method mainly used in reducing CO₂ emissions to mitigate anthropogenic climate change. The use of mixed-matrix membranes (MMMs) arrives as a possible answer, combining the high selectivity of inorganic membranes with high permeability of organic membranes. However, the combination of these materials is challenging due to their opposing nature, leading to poor interactions between polymeric matrix and inorganic fillers. Many additives have been tested to reduce interfacial voids, some of which showed potential in dealing with compatibility problems, but most of them lack further studies and optimization. Deep eutectic solvents (DESs) have emerged as IL substitutes since they are cheaper and environmentally friendly. Choline chloride-based deep eutectic solvents were studied as additives in polyethersulfone (PES)/SAPO-34 membranes to improve CO₂ permeability and CO₂/N₂ and CO₂/CH₄ selectivity. SAPO-34 crystals of 150 nm with a high surface area and microporosity were synthesized using dry-gel methodology. The PES/SAPO-34 membranes were optimized following previous work and used in a defined composition, using 5 or 10 w/w% of DES during membrane preparation. All MMMs were characterized by their ideal gas permeability using N₂ and CO₂ pure gasses. Selected membranes were also tested using CH₄ pure gas. The results presented that 5 w/w%, in polymer mass, of ChCl–glycerol presented the best result over the synthesized membranes. An increase of 200% in CO₂ permeability maintains the CO₂/N₂ selectivity for the non-modified PES/SAPO-34 membrane. A CO₂/CH₄ selectivity of 89.7 was obtained in PES/SAPO-34/ChCl-glycerol membranes containing 5 w/w% of this DES, which is an outstanding ideal separation performance for MMMs when compared to other results in the literature. FTIR analysis reiterates the presence of glycerol in the membranes prepared. Dynamic Mechanical Thermal Analysis (DMTA) shows that the addition of 5 w/w% of DES does not impact the membrane flexibility or polymer structure. However, in concentrations higher than 10 w/w%, the inclusion of DES could lead to high membrane rigidification without impacting the overall thermal resistance. SEM analysis of DES-enhanced membranes presented asymmetric final membranes and reaffirmed the results obtained in DMTA about rigidified structures and lower zeolite–polymer interaction with higher concentrations of DES. Full article

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

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12 pages, 2800 KB

Open AccessEditor’s ChoiceReview

Perspectives and State of the Art of Membrane Separation Technology as a Key Element in the Development of Hydrogen Economy

by M. Olga Guerrero-Pérez

Membranes 2024, 14(11), 228; https://doi.org/10.3390/membranes14110228 - 30 Oct 2024

Cited by 5 | Viewed by 4223

Abstract

Due to the objectives established by the European Union and other countries, hydrogen production will be a key technology in the coming decades. There are several starting materials and procedures for its production. All methods have advantages and disadvantages, and the improvements in [...] Read more.

Due to the objectives established by the European Union and other countries, hydrogen production will be a key technology in the coming decades. There are several starting materials and procedures for its production. All methods have advantages and disadvantages, and the improvements in their performance and decreases in operational costs will be decisive in determining which of them is implemented. For all cases, including for the storage and transport of hydrogen, membranes determine the performance of the process, as well as the operational costs. The present contribution summarizes the most recent membrane technologies for the main methods of hydrogen production, including the challenges to overcome in each case. Full article

(This article belongs to the Special Issue A Commemorative Special Issue in Honor of Dr. Moises Carreon)

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19 pages, 8621 KB

Open AccessEditor’s ChoiceArticle

The Application of TiO₂/ZrO₂-Modified Nanocomposite PES Membrane for Improved Permeability of Textile Dye in Water

by Sibukiso Thobani Nhlengethwa, Charmaine Sesethu Tshangana, Bhekie Brilliance Mamba and Adolph Anga Muleja

Membranes 2024, 14(10), 222; https://doi.org/10.3390/membranes14100222 - 21 Oct 2024

Cited by 5 | Viewed by 2359

Abstract

This study investigates the modification of polyethersulfone (PES) membranes with 1 wt% titanium dioxide (TiO₂), zirconium dioxide (ZrO₂) and a nanocomposite of TiO₂/ZrO₂. The aim was to efficiently remove Rhodamine B (RhB) from water using [...] Read more.

This study investigates the modification of polyethersulfone (PES) membranes with 1 wt% titanium dioxide (TiO₂), zirconium dioxide (ZrO₂) and a nanocomposite of TiO₂/ZrO₂. The aim was to efficiently remove Rhodamine B (RhB) from water using a threefold approach of adsorption, filtration and photodegradation. Among the modified membranes (TiO₂, ZrO₂ and TiO₂/ZrO₂), the TiO₂/ZrO₂-PES nanocomposite membrane showed a better performance in rejection of RhB than other membranes with the rejection efficiency of 96.5%. The TiO₂/ZrO₂-PES membrane was found to possess a thicker selective layer and reduced mean pore radius, which contributed to its improved rejection. The TiO₂/ZrO₂ nanocomposite membrane also showed high bulk porosity and a slightly lower contact angle of 69.88° compared to pristine PES with a value of 73°, indicating an improvement in hydrophilicity. Additionally, the TiO₂/ZrO₂-PES nanocomposite membrane demonstrated a relatively lower surface roughness (Sa) of 8.53 nm, which offers the membrane antifouling properties. The TiO₂/ZrO₂-PES membrane showed flux recovery ratio (FRR), total fouling (R_t), reversible fouling (R_r) and irreversible fouling (R_ir) of 48.0%, 88.7%, 36,8% and 52.9%, respectively. For the photocatalytic degradation performance, the removal efficiency of RhB followed this order TiO₂ > TiO₂/ZrO₂ > ZrO₂ (87.6%, 85.7%, 67.8%). The tensile strength and elongation were found to be compromised with the addition of nanoparticles and nanocomposites. This indicates the necessity to further modify and optimise membrane fabrication to achieve improved mechanical strength of the membranes. At low pressure, the overall findings suggest that the TiO₂/ZrO₂ nanocomposite has the potential to offer significant improvements in membrane performance (water flux) compared to other modifications. Full article

(This article belongs to the Special Issue Prospects for Nanocomposite Membrane Applications)

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83 pages, 5867 KB

Open AccessEditor’s ChoiceReview

Fouling of Reverse Osmosis (RO) and Nanofiltration (NF) Membranes by Low Molecular Weight Organic Compounds (LMWOCs), Part 1: Fundamentals and Mechanism

by Yasushi Maeda

Membranes 2024, 14(10), 221; https://doi.org/10.3390/membranes14100221 - 17 Oct 2024

Cited by 12 | Viewed by 11783

Abstract

Reverse osmosis (RO) and nanofiltration (NF) are ubiquitous technologies in modern water treatment, finding applications across various sectors. However, the availability of high-quality water suitable for RO/NF feed is diminishing due to droughts caused by global warming, increasing demand, and water pollution. As [...] Read more.

Reverse osmosis (RO) and nanofiltration (NF) are ubiquitous technologies in modern water treatment, finding applications across various sectors. However, the availability of high-quality water suitable for RO/NF feed is diminishing due to droughts caused by global warming, increasing demand, and water pollution. As concerns grow over the depletion of precious freshwater resources, a global movement is gaining momentum to utilize previously overlooked or challenging water sources, collectively known as “marginal water”. Fouling is a serious concern when treating marginal water. In RO/NF, biofouling, organic and colloidal fouling, and scaling are particularly problematic. Of these, organic fouling, along with biofouling, has been considered difficult to manage. The major organic foulants studied are natural organic matter (NOM) for surface water and groundwater and effluent organic matter (EfOM) for municipal wastewater reuse. Polymeric substances such as sodium alginate, humic acid, and proteins have been used as model substances of EfOM. Fouling by low molecular weight organic compounds (LMWOCs) such as surfactants, phenolics, and plasticizers is known, but there have been few comprehensive reports. This review aims to shed light on fouling behavior by LMWOCs and its mechanism. LMWOC foulants reported so far are summarized, and the role of LMWOCs is also outlined for other polymeric membranes, e.g., UF, gas separation membranes, etc. Regarding the mechanism of fouling, it is explained that the fouling is caused by the strong interaction between LMWOC and the membrane, which causes the water permeation to be hindered by LMWOCs adsorbed on the membrane surface (surface fouling) and sorbed inside the membrane pores (internal fouling). Adsorption amounts and flow loss caused by the LMWOC fouling were well correlated with the octanol-water partition coefficient (log P). In part 2, countermeasures to solve this problem and applications using the LMWOCs will be outlined. Full article

(This article belongs to the Collection Featured Reviews in Membrane Science)

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21 pages, 3811 KB

Open AccessEditor’s ChoiceReview

The Influence of Cholesterol on Membrane Targeted Bioactive Peptides: Modulating Peptide Activity Through Changes in Bilayer Biophysical Properties

by Juan M. Giraldo-Lorza, Chad Leidy and Marcela Manrique-Moreno

Membranes 2024, 14(10), 220; https://doi.org/10.3390/membranes14100220 - 17 Oct 2024

Cited by 6 | Viewed by 6416

Abstract

Cholesterol is a biological molecule that is essential for cellular life. It has unique features in terms of molecular structure and function, and plays an important role in determining the structure and properties of cell membranes. One of the most recognized functions of [...] Read more.

Cholesterol is a biological molecule that is essential for cellular life. It has unique features in terms of molecular structure and function, and plays an important role in determining the structure and properties of cell membranes. One of the most recognized functions of cholesterol is its ability to increase the level of lipid packing and rigidity of biological membranes while maintaining high levels of lateral mobility of the bulk lipids, which is necessary to sustain biochemical signaling events. There is increased interest in designing bioactive peptides that can act as effective antimicrobial agents without causing harm to human cells. For this reason, it becomes relevant to understand how cholesterol can affect the interaction between bioactive peptides and lipid membranes, in particular by modulating the peptides’ ability to penetrate and disrupt the membranes through these changes in membrane rigidity. Here we discuss cholesterol and its role in modulating lipid bilayer properties and discuss recent evidence showing how cholesterol modulates bioactive peptides to different degrees. Full article

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

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20 pages, 8512 KB

Open AccessEditor’s ChoiceArticle

Computational Fluid Dynamics Modelling of Hydrogen Production via Water Splitting in Oxygen Membrane Reactors

by Kai Bittner, Nikolaos Margaritis, Falk Schulze-Küppers, Jörg Wolters and Ghaleb Natour

Membranes 2024, 14(10), 219; https://doi.org/10.3390/membranes14100219 - 17 Oct 2024

Cited by 4 | Viewed by 3063

Abstract

The utilization of oxygen transport membranes enables the production of high-purity hydrogen by the thermal decomposition of water below 1000 °C. This process is based on a chemical potential gradient across the membrane, which is usually achieved by introducing a reducing gas. Computational [...] Read more.

The utilization of oxygen transport membranes enables the production of high-purity hydrogen by the thermal decomposition of water below 1000 °C. This process is based on a chemical potential gradient across the membrane, which is usually achieved by introducing a reducing gas. Computational fluid dynamics (CFD) can be used to model reactors based on this concept. In this study, a modelling approach for water splitting is presented in which oxygen transport through the membrane acts as the rate-determining process for the overall reaction. This transport step is implemented in the CFD simulation. Both gas compartments are modelled in the simulations. Hydrogen and methane are used as reducing gases. The model is validated using experimental data from the literature and compared with a simplified perfect mixing modelling approach. Although the main focus of this work is to propose an approach to implement the water splitting in CFD simulations, a simulation study was conducted to exemplify how CFD modelling can be utilized in design optimization. Simplified 2-dimensional and rotational symmetric reactor geometries were compared. This study shows that a parallel overflow of the membrane in an elongated reactor is advantageous, as this reduces the back diffusion of the reaction products, which increases the mean driving force for oxygen transport through the membrane. Full article

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

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35 pages, 26525 KB

Open AccessEditor’s ChoiceReview

Efficient Removal of PFASs Using Photocatalysis, Membrane Separation and Photocatalytic Membrane Reactors

by Nonhle Siphelele Neliswa Mabaso, Charmaine Sesethu Tshangana and Adolph Anga Muleja

Membranes 2024, 14(10), 217; https://doi.org/10.3390/membranes14100217 - 14 Oct 2024

Cited by 11 | Viewed by 6290

Abstract

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are persistent compounds characterized by stable C−F bonds giving them high thermal and chemical stability. Numerous studies have highlighted the presence of PFASs in the environment, surface waters and animals and humans. Exposure to these chemicals has been [...] Read more.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are persistent compounds characterized by stable C−F bonds giving them high thermal and chemical stability. Numerous studies have highlighted the presence of PFASs in the environment, surface waters and animals and humans. Exposure to these chemicals has been found to cause various health effects and has necessitated the need to develop methods to remove them from the environment. To date, the use of photocatalytic degradation and membrane separation to remove PFASs from water has been widely studied; however, these methods have drawbacks hindering them from being applied at full scale, including the recovery of the photocatalyst, uneven light distribution and membrane fouling. Therefore, to overcome some of these challenges, there has been research involving the coupling of photocatalysis and membrane separation to form photocatalytic membrane reactors which facilitate in the recovery of the photocatalyst, ensuring even light distribution and mitigating fouling. This review not only highlights recent advancements in the removal of PFASs using photocatalysis and membrane separation but also provides comprehensive information on the integration of photocatalysis and membrane separation to form photocatalytic membrane reactors. It emphasizes the performance of immobilized and slurry systems in PFAS removal while also addressing the associated challenges and offering recommendations for improvement. Factors influencing the performance of these methods will be comprehensively discussed, as well as the nanomaterials used for each technology. Additionally, knowledge gaps regarding the removal of PFASs using integrated photocatalytic membrane systems will be addressed, along with a comprehensive discussion on how these technologies can be applied in real-world applications. Full article

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

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26 pages, 9055 KB

Open AccessEditor’s ChoiceArticle

The Efficiency of Polyester-Polysulfone Membranes, Coated with Crosslinked PVA Layers, in the Water Desalination by Pervaporation

by Izabela Gortat, Jerzy J. Chruściel, Joanna Marszałek, Renata Żyłła and Paweł Wawrzyniak

Membranes 2024, 14(10), 213; https://doi.org/10.3390/membranes14100213 - 7 Oct 2024

Cited by 1 | Viewed by 3342

Abstract

Composite polymer membranes were obtained using the so-called dry phase inversion and were used for desalination of diluted saline water solutions by pervaporation (PV) method. The tests used a two-layer backing, porous, ultrafiltration commercial membrane (PS20), which consisted of a supporting polyester layer [...] Read more.

Composite polymer membranes were obtained using the so-called dry phase inversion and were used for desalination of diluted saline water solutions by pervaporation (PV) method. The tests used a two-layer backing, porous, ultrafiltration commercial membrane (PS20), which consisted of a supporting polyester layer and an active polysulfone layer. The active layer of PV membranes was obtained in an aqueous environment, in the presence of a surfactant, by cross-linking a 5 wt.% aqueous solution of polyvinyl alcohol (PVA)—using various amounts of cross-linking substances: 50 wt.% aqueous solutions of glutaraldehyde (GA) or citric acid (CA) or a 40 wt.% aqueous solution of glyoxal. An ethylene glycol oligomer (PEG 200) was also used to prepare active layers on PV membranes. Witch its help a chemically cross-linked hydrogel with PVA and cross-linking reagents (CA or GA) was formed and used as an active layer. The manufactured PV membranes (PVA/PSf/PES) were used in the desalination of water with a salinity of 35‰, which corresponds to the average salinity of oceans. The pervaporation method was used to examine the efficiency (productivity and selectivity) of the desalination process. The PV was carried at a temperature of 60 °C and a feed flow rate of 60 dm³/h while the membrane area was 0.005 m². The following characteristic parameters of the membranes were determined: thickness, hydrophilicity (based on contact angle measurements), density, degree of swelling and cross-linking density and compared with the analogous properties of the initial PS20 backing membrane. The physical microstructure of the cross-section of the membranes was analyzed using scanning electron microscopy (SEM) method. Full article

(This article belongs to the Special Issue Membrane Processes in a Circular Economy: Opportunities and Challenges)

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18 pages, 9413 KB

Open AccessEditor’s ChoiceArticle

Performance and Enhanced Efficiency Induced by Cold Plasma on SAPO-34 Membranes for CO₂ and CH₄ Mixtures

by Fnu Gorky, Vashanti Storr, Grace Jones, Apolo Nambo, Jacek B. Jasinski and Maria L. Carreon

Membranes 2024, 14(8), 178; https://doi.org/10.3390/membranes14080178 - 20 Aug 2024

Cited by 4 | Viewed by 3767

Abstract

In this study, we investigate the influence of cold-plasma-induced enhanced performance and efficiency of SAPO-34 membranes in the separation of CO₂ and CH₄ mixtures. Placing the herein presented research in a broader context, we aim to address the question of whether [...] Read more.

In this study, we investigate the influence of cold-plasma-induced enhanced performance and efficiency of SAPO-34 membranes in the separation of CO₂ and CH₄ mixtures. Placing the herein presented research in a broader context, we aim to address the question of whether cold plasma can significantly impact the membrane performance. We subjected SAPO-34 membranes to plasma mild disturbances and analyzed their performance in separating CO₂ and CH₄. Our findings reveal a notable enhancement in membrane efficiency and sustained performance when exposed to cold plasma. The pulsed plasma separation displayed improved structural integrity, and the experimental results indicated that the linear structure of CO₂ facilitates the distortion of electron clouds in response to the electric field, a property known as polarizability, which aids in effective separation. Plausible mechanistic insight indicated that the intermolecular forces facilitated an integral role in SAPO-34 membranes exhibiting strong electrostatic interactions. In conclusion, our research highlights the potential of cold plasma as a promising technique for improving the performance of SAPO-34 membranes in gas mixtures at atmospheric pressures, providing valuable insights for optimizing membrane technology in carbon capture and gas separation applications. Full article

(This article belongs to the Special Issue A Commemorative Special Issue in Honor of Dr. Moises Carreon)

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20 pages, 4099 KB

Open AccessEditor’s ChoiceArticle

Treatment of Synthetic Wastewater Containing Polystyrene (PS) Nanoplastics by Membrane Bioreactor (MBR): Study of the Effects on Microbial Community and Membrane Fouling

by Anamary Pompa-Pernía, Serena Molina, Laura Cherta, Lorena Martínez-García and Junkal Landaburu-Aguirre

Membranes 2024, 14(8), 174; https://doi.org/10.3390/membranes14080174 - 9 Aug 2024

Cited by 4 | Viewed by 3869

Abstract

The persistent presence of micro- and nanoplastics (MNPs) in aquatic environments, particularly via effluents from wastewater treatment plants (WWTPs), poses significant ecological risks. This study investigated the removal efficiency of polystyrene nanoplastics (PS-NPs) using a lab-scale aerobic membrane bioreactor (aMBR) equipped with different [...] Read more.

The persistent presence of micro- and nanoplastics (MNPs) in aquatic environments, particularly via effluents from wastewater treatment plants (WWTPs), poses significant ecological risks. This study investigated the removal efficiency of polystyrene nanoplastics (PS-NPs) using a lab-scale aerobic membrane bioreactor (aMBR) equipped with different membrane types: microfiltration (MF), commercial ultrafiltration (c-UF), and recycled ultrafiltration (r-UF) membranes. Performance was assessed using synthetic urban wastewater spiked with PS-NPs, focusing on membrane efficiency, fouling behavior, and microbial community shifts. All aMBR systems achieved high organic matter removal, exceeding a 97% COD reduction in both the control and PS-exposed reactors. While low concentrations of PS-NPs did not significantly impact the sludge settleability or soluble microbial products initially, a higher accumulation increased the carbohydrate concentrations, indicating a protective bacterial response. The microbial community composition also adapted over time under polystyrene stress. All membrane types exhibited substantial NP removal; however, the presence of nano-sized PS particles negatively affected the membrane performance, enhancing the fouling phenomena and increasing transmembrane pressure. Despite this, the r-UF membrane demonstrated comparable efficiency to c-UF, suggesting its potential for sustainable applications. Advanced characterization techniques including pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) were employed for NP detection and quantification. Full article

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

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16 pages, 5680 KB

Open AccessEditor’s ChoiceArticle

Mixed-Matrix Organo-Silica–Hydrotalcite Membrane for CO₂ Separation Part 1: Synthesis and Analytical Description

by Lucas Bünger, Krassimir Garbev, Angela Ullrich, Peter Stemmermann and Dieter Stapf

Membranes 2024, 14(8), 170; https://doi.org/10.3390/membranes14080170 - 6 Aug 2024

Cited by 2 | Viewed by 2637

Abstract

Hydrotalcite exhibits the capability to adsorb CO₂ at elevated temperatures. High surface area and favorable coating properties are essential to harness its potential for practical applications. Stable alcohol-based dispersions are needed for thin film applications of mixed membranes containing hydrotalcite. Currently, producing [...] Read more.

Hydrotalcite exhibits the capability to adsorb CO₂ at elevated temperatures. High surface area and favorable coating properties are essential to harness its potential for practical applications. Stable alcohol-based dispersions are needed for thin film applications of mixed membranes containing hydrotalcite. Currently, producing such dispersions without the need for delamination and dispersing agents is a challenging task. This work introduces, for the first time, a manufacturing approach to overcoming the drawbacks mentioned above. It includes a synthesis of hydrotalcite nanoparticles, followed by agent-free delamination of their layers and final dispersion into alcohol without dispersing agents. Further, the hydrotalcite-derived sorption agent is dispersed in a matrix based on organo-silica gels derived from 1,2-bis(triethoxysilyl)ethane (BTESE). The analytical results indicate that the interconnection between hydrotalcite and BTESE-derived gel occurs via forming a strong hydrogen bonding system between the interlayer species (OH groups, CO₃²⁻) of hydrotalcite and oxygen and silanol active gel centers. These findings lay the foundation for applications involving incorporating hydrotalcite-like compounds into silica matrices, ultimately enabling the development of materials with exceptional mass transfer properties. In part 2 of this study, the gas separation performance of the organo-silica and the hydrotalcite-like materials and their combined form will be investigated. Full article

(This article belongs to the Special Issue Advanced Membrane Materials for CO₂ Capture and Separation)

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23 pages, 18244 KB

Open AccessEditor’s ChoiceArticle

Removal of Microplastics in a Hybrid Treatment Process of Ceramic Microfiltration and Photocatalyst-Mounted PES Spheres with Air Backwashing

by Minjoo Song and Jin Yong Park

Membranes 2024, 14(8), 169; https://doi.org/10.3390/membranes14080169 - 31 Jul 2024

Cited by 3 | Viewed by 3068

Abstract

Microplastics (MPs), which are defined as plastics with a size of less than 5 mm, cannot be treated completely in wastewater treatment plants (WWTPs) and discharged to a water body because they are too small in size. It has been reported that MPs [...] Read more.

Microplastics (MPs), which are defined as plastics with a size of less than 5 mm, cannot be treated completely in wastewater treatment plants (WWTPs) and discharged to a water body because they are too small in size. It has been reported that MPs can have adverse effects on human beings and water ecosystems. There is a need to combine existing drinking water treatment plants (DWTPs) and WWTPs with the traditional treatment process and technology with high removal efficiency of MPs or to develop a new technology to separate MPs from water and wastewater. In this study, the effects of MPs (polyethylene (PE), 125 μm) and organic matter (humic acid) were researched in a hybrid treatment process of ceramic microfiltration (MF) and photocatalyst (TiO₂)-mounted polyether sulfone (PES) spheres with air backwashing. The roles of the MF, photooxidation, and adsorption of PES spheres were confirmed in a single MF process (MF), an MF process with UV irradiation (MF+UV), MF and PES sphere adsorption without UV irradiation (MF+PES), and a hybrid process incorporating MF and PES spheres with UV irradiation (MF+PES+UV). The impact of the air backwashing cycle (filtration time, FT) on filtration characteristics and treatment efficiencies in the hybrid process was studied. In the MF process, membrane fouling increased with increasing organic matter (HA, humic acid). The treatment efficiency of MPs increased; however, that of dissolved organic matter (DOM) decreased with increasing HA. As MPs increased, the membrane fouling decreased; however, total filtration volume (V_T) remained almost constant. The treatment efficiency of MPs increased a little, and that of DOM showed a dropping trend. In the hybrid process, the membrane fouling was controlled via the adsorption and UV photooxidation of the PES spheres, and the DOM treatment efficiency increased by combining processes from MF to MF+PES+UV. The optimal FT was 10 min at BT 10 s in this hybrid process. The results could be applied to separate MPs effectively in DWTPs/WWTPs. Full article

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

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15 pages, 2271 KB

Open AccessEditor’s ChoiceArticle

Lipid-Based Catalysis Demonstrated by Bilayer-Enabled Ester Hydrolysis

by Shu Liu, Kiran Kumar, Tracey Bell, Ayyalusamy Ramamoorthy, David Van Winkle and Steven Lenhert

Membranes 2024, 14(8), 168; https://doi.org/10.3390/membranes14080168 - 30 Jul 2024

Viewed by 3407

Abstract

Lipids have not traditionally been considered likely candidates for catalyzing reactions in biological systems. However, there is significant evidence that aggregates of amphiphilic compounds are capable of catalyzing reactions in synthetic organic chemistry. Here, we demonstrate the potential for the hydrophobic region of [...] Read more.

Lipids have not traditionally been considered likely candidates for catalyzing reactions in biological systems. However, there is significant evidence that aggregates of amphiphilic compounds are capable of catalyzing reactions in synthetic organic chemistry. Here, we demonstrate the potential for the hydrophobic region of a lipid bilayer to provide an environment suitable for catalysis by means of a lipid aggregate capable of speeding up a chemical reaction. By bringing organic molecules into the nonpolar or hydrophobic region of a lipid bilayer, reactions can be catalyzed by individual or collections of small, nonpolar, or amphiphilic molecules. We demonstrate this concept by the ester hydrolysis of calcein-AM to produce a fluorescent product, which is a widely used assay for esterase activity in cells. The reaction was first carried out in a two-phase octanol–water system, with the organic phase containing the cationic amphiphiles cetyltrimethylammonium bromide (CTAB) or octadecylamine. The octanol phase was then replaced with phospholipid vesicles in water, where the reaction was also found to be carried out. The reaction was monitored using quantitative fluorescence, which revealed catalytic turnover numbers on a scale of

10^{- 7}

to

10^{- 8}

s⁻¹ for each system, which is much slower than enzymatic catalysis. The reaction product was characterized by ¹H-NMR measurements, which were consistent with ester hydrolysis. The implications of thinking about lipids and lipid aggregates as catalytic entities are discussed in the context of biochemistry, pharmacology, and synthetic biology. Full article

(This article belongs to the Special Issue Structural, Dynamical, and Functional Implications of Membrane Compositional Heterogeneity)

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15 pages, 4602 KB

Open AccessEditor’s ChoiceArticle

Influence of Feed Composition on the Separation Factor during Nanofiltration of Organic Acids

by Gustavo Tottoli, Sylvain Galier and Hélène Roux-de Balmann

Membranes 2024, 14(8), 166; https://doi.org/10.3390/membranes14080166 - 28 Jul 2024

Cited by 4 | Viewed by 2269

Abstract

In this study, nanofiltration experiments using synthetic solutions containing acetate, butyrate, and lactate are carried out to assess the impact of the feed composition, i.e., feed concentration and feed proportions, on the separation factor of couples of solutes in binary and ternary solutions. [...] Read more.

In this study, nanofiltration experiments using synthetic solutions containing acetate, butyrate, and lactate are carried out to assess the impact of the feed composition, i.e., feed concentration and feed proportions, on the separation factor of couples of solutes in binary and ternary solutions. In binary solutions, no influence of the solute proportions in the feed was pointed out, whatever the couple of solutes. The separation factor of acetate/butyrate and acetate/lactate was found to decrease with increasing feed concentration, while that of lactate/butyrate remained constant. The separation factors of acetate/lactate and lactate/butyrate were identical in ternary solutions compared to binary ones, showing no impact of the addition of the third solute. In ternary solutions, the presence of lactate decreased the separation factor of acetate/butyrate, but this decrease was not influenced by the proportion of lactate. Full article

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

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30 pages, 3847 KB

Open AccessEditor’s ChoiceReview

Carbon-Based Nanocomposite Membranes for Membrane Distillation: Progress, Problems and Future Prospects

by Chhabilal Regmi, Yuwaraj K. Kshetri and S. Ranil Wickramasinghe

Membranes 2024, 14(7), 160; https://doi.org/10.3390/membranes14070160 - 20 Jul 2024

Cited by 11 | Viewed by 4472

Abstract

The development of an ideal membrane for membrane distillation (MD) is of the utmost importance. Enhancing the efficiency of MD by adding nanoparticles to or onto a membrane’s surface has drawn considerable attention from the scientific community. It is crucial to thoroughly examine [...] Read more.

The development of an ideal membrane for membrane distillation (MD) is of the utmost importance. Enhancing the efficiency of MD by adding nanoparticles to or onto a membrane’s surface has drawn considerable attention from the scientific community. It is crucial to thoroughly examine state-of-the-art nanomaterials-enabled MD membranes with desirable properties, as they greatly enhance the efficiency and reliability of the MD process. This, in turn, opens up opportunities for achieving a sustainable water–energy–environment nexus. By introducing carbon-based nanomaterials into the membrane’s structure, the membrane gains excellent separation abilities, resistance to various feed waters, and a longer lifespan. Additionally, the use of carbon-based nanomaterials in MD has led to improved membrane performance characteristics such as increased permeability and a reduced fouling propensity. These nanomaterials have also enabled novel membrane capabilities like in situ foulant degradation and localized heat generation. Therefore, this review offers an overview of how the utilization of different carbon-based nanomaterials in membrane synthesis impacts the membrane characteristics, particularly the liquid entry pressure (LEP), hydrophobicity, porosity, and membrane permeability, as well as reduced fouling, thereby advancing the MD technology for water treatment processes. Furthermore, this review also discusses the development, challenges, and research opportunities that arise from these findings. Full article

(This article belongs to the Special Issue Membrane and Other Innovative Technologies for Water Purification: Design, Development, and Application)

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10 pages, 610 KB

Open AccessEditor’s ChoiceReview

Electrophysiological Insights into Antibiotic Translocation and Resistance: The Impact of Outer Membrane Proteins

by Ishan Ghai

Membranes 2024, 14(7), 161; https://doi.org/10.3390/membranes14070161 - 20 Jul 2024

Cited by 11 | Viewed by 3939

Abstract

The alarming rise of antibiotic resistance in Gram-negative bacteria has emerged as a major global health challenge. A key factor contributing to this crisis is the low permeability of the bacterial outer membrane, which acts as a barrier that prevents antibiotics from entering [...] Read more.

The alarming rise of antibiotic resistance in Gram-negative bacteria has emerged as a major global health challenge. A key factor contributing to this crisis is the low permeability of the bacterial outer membrane, which acts as a barrier that prevents antibiotics from entering the cell. Protein channels embedded in this outer membrane selectively regulate the influx of hydrophilic compounds, including antibiotics. To combat antibiotic resistance, understanding the molecular mechanisms governing antibiotic permeability through bacterial membrane channels is crucial. This knowledge is key towards elucidating their roles in studing antibiotic resistance. By compiling and analysing the flux data from multiple electrophysiological reversal potential experimental studies, which involves measuring zero-current potentials and the corresponding single-channel conductance, we can calculate the flux of charged antibiotics/compounds across different Gram-negative bacterial outer membrane channels. Through this comprehensive synthesis, this review aims to advance our understanding and stimulate discussions about the physicochemical factors influencing the flux of antibiotics through bacterial membrane protein channels, ultimately enhancing our knowledge in this area. Full article

(This article belongs to the Section Biological Membrane Composition and Structures)

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33 pages, 7458 KB

Open AccessEditor’s ChoiceArticle

Performance and Environmental Assessment of Biochar-Based Membranes Synthesized from Traditional and Eco-Friendly Solvents

by Abelline Fionah, Isaac Oluk, Laura Brady, Diana M. Byrne and Isabel C. Escobar

Membranes 2024, 14(7), 153; https://doi.org/10.3390/membranes14070153 - 11 Jul 2024

Cited by 10 | Viewed by 4234

Abstract

Water contamination resulting from coal spills is one of the largest environmental problems affecting communities in the Appalachia Region of the United States. This coal slurry contains potentially toxic substances, such as hydrocarbons, heavy metals, and coal cleaning chemicals, and its leakage into [...] Read more.

Water contamination resulting from coal spills is one of the largest environmental problems affecting communities in the Appalachia Region of the United States. This coal slurry contains potentially toxic substances, such as hydrocarbons, heavy metals, and coal cleaning chemicals, and its leakage into water bodies (lakes, rivers, and aquifers) can lead to adverse health effects not only for freshwater bodies and plant life but also for humans. This study focused on two major experiments. The first experiment involved the use of biochar to create a biochar–polysulfone (BC-PSf) flat-sheet multifunctional membrane to remove organic contaminants, and the other major experiment compared eco-friendly (gamma-valerolactone—GVL; Rhodiasolv^® PolarClean—PC) and petroleum-derived solvents (i.e., N-methyl-pyrrolidone—NMP) in the fabrication of the biochar–polysulfone membranes. The resulting membranes were tested for their efficiency in removing both positively and negatively charged organic contaminants from the collected water at varying pH values. A comparative life cycle assessment (LCA) with accompanying uncertainty and sensitivity analyses was carried out to understand the global environmental impacts of incorporating biochar, NMP, GVL, and PC in the synthesis of PSf/NMP, BC-PSf/NMP, PSf/GVL, BC-PSf/GVL, PSf/PC, and BC-PSf/PC membranes at a set surface area of 1000 m². The results showed that the addition of biochar to the membrane matrix increased the surface area of the membranes and improved both their adsorptive and mechanical properties. The membranes with biochar incorporated in their matrix showed a higher potential for contaminant removal than those without biochar. The environmental impacts normalized to the BC-PSf/GVL membrane showed that the addition of biochar increased global warming impacts, eutrophication, and respiratory impacts by over 100% in all the membrane configurations with biochar. The environmental impacts were highly sensitive to biochar addition (Spearman’s coefficient > 0.8). The BC/PSf membrane with Rhodiasolv^® PolarClean had the lowest associated global environmental impacts among all the membranes with biochar. Ultimately, this study highlighted potential tradeoffs between functional performance and global environmental impacts regarding choices for membrane fabrication. Full article

(This article belongs to the Collection Polymeric Membranes: Science, Materials and Applications)

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13 pages, 7170 KB

Open AccessEditor’s ChoiceArticle

Application of Recycled Ultrafiltration Membranes in an Aerobic Membrane Bioreactor (aMBR): A Validation Study

by Laura Rodríguez-Sáez, Junkal Landaburu-Aguirre, Eloy García-Calvo and Serena Molina

Membranes 2024, 14(7), 149; https://doi.org/10.3390/membranes14070149 - 5 Jul 2024

Viewed by 2553

Abstract

A validation study using recycled ultrafiltration membranes (r-UF) on an aerobic membrane bioreactor (aMBR) was conducted for the first time. Four different polyethersulfone (PES) membranes were tested using synthetic urban wastewater (COD 0.4–0.5 g/L) during two experimental periods: (i) recycled ultrafiltration membrane (r-UF) [...] Read more.

A validation study using recycled ultrafiltration membranes (r-UF) on an aerobic membrane bioreactor (aMBR) was conducted for the first time. Four different polyethersulfone (PES) membranes were tested using synthetic urban wastewater (COD 0.4–0.5 g/L) during two experimental periods: (i) recycled ultrafiltration membrane (r-UF) and commercial UF membrane (molecular weight cut-off (MWCO) 150 kDa) (c-150 kDa); (ii) r-UF membrane modified by dip-coating using catechol (CA) and polyethyleneimine (PEI) (mr-UF) and c-20 kDa membrane. Permeability, fouling behavior, and permeate quality were evaluated. Extensive membrane characterization was conducted using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray (EDX), and confocal laser scanning microscopy (CLSM). Permeate quality for r-UF and mr-UF membranes was excellent and comparable to that obtained using commercial membranes under similar conditions. Additionally, r-UF and mr-UF membranes presented a steadier performance time. Additionally, r-UF membrane demonstrated less tendency to be fouled (R_f, m⁻¹) r-UF 7.92 ± 0.57 × 10¹²; mr-UF 9.90 ± 0.14 × 10¹², c-150 kDa 1.56 ± 0.07 × 10¹³ and c-20 kDa 1.25 ± 0.50 × 10¹³. The r-UF membrane showed an excellent antibiofouling character. Therefore, r-UF membranes can be successfully implemented for wastewater treatment in aMBR, being a sustainable and cost-effective alternative to commercial membranes that can contribute to overcome membrane fouling and membrane replacement issues. Full article

(This article belongs to the Special Issue Advanced Membranes and Membrane Technologies for Wastewater Treatment)

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15 pages, 2173 KB

Open AccessEditor’s ChoiceArticle

Efficient Isolation of Outer Membrane Vesicles (OMVs) Secreted by Gram-Negative Bacteria via a Novel Gradient Filtration Method

by Ning Li, Minghui Wu, Lu Wang, Mengyu Tang, Hongbo Xin and Keyu Deng

Membranes 2024, 14(6), 135; https://doi.org/10.3390/membranes14060135 - 6 Jun 2024

Cited by 10 | Viewed by 5447

Abstract

Bacterial extracellular vesicles (bEVs) secreted by Gram-negative bacteria are referred to as outer membrane vesicles (OMVs) because they originate in the outer membrane. OMVs are membrane-coated vesicles 20–250 nm in size. They contain lipopolysaccharide (LPS), peptidoglycan, proteins, lipids, nucleic acids, and other substances [...] Read more.

Bacterial extracellular vesicles (bEVs) secreted by Gram-negative bacteria are referred to as outer membrane vesicles (OMVs) because they originate in the outer membrane. OMVs are membrane-coated vesicles 20–250 nm in size. They contain lipopolysaccharide (LPS), peptidoglycan, proteins, lipids, nucleic acids, and other substances derived from their parent bacteria and participate in the transmission of information to host cells. OMVs have broad prospects in terms of potential application in the fields of adjuvants, vaccines, and drug delivery vehicles. Currently, there remains a lack of efficient and convenient methods to isolate OMVs, which greatly limits OMV-related research. In this study, we developed a fast, convenient, and low-cost gradient filtration method to separate OMVs that can achieve industrial-scale production while maintaining the biological activity of the isolated OMVs. We compared the gradient filtration method with traditional ultracentrifugation to isolate OMVs from probiotic Escherichia coli Nissle 1917 (EcN) bacteria. Then, we used RAW264.7 macrophages as an in vitro model to study the influence on the immune function of EcN-derived OMVs obtained through the gradient filtration method. Our results indicated that EcN-derived OMVs were efficiently isolated using our gradient filtration method. The level of OMV enrichment obtained via our gradient filtration method was about twice as efficient as that achieved through traditional ultracentrifugation. The EcN-derived OMVs enriched through the gradient filtration method were successfully taken up by RAW264.7 macrophages and induced them to secrete pro-inflammatory cytokines such as tumor necrosis factor α (TNF-α) and interleukins (ILs) 6 and 1β, as well as anti-inflammatory cytokine IL-10. Furthermore, EcN-derived OMVs induced more anti-inflammatory response (i.e., IL-10) than pro-inflammatory response (i.e., TNF-α, IL-6, and IL-1β). These results were consistent with those reported in the literature. The related literature reported that EcN-derived OMVs obtained through ultracentrifugation could induce stronger anti-inflammatory responses than pro-inflammatory responses in RAW264.7 macrophages. Our simple and novel separation method may therefore have promising prospects in terms of applications involving the study of OMVs. Full article

(This article belongs to the Special Issue Design and Characterization of Membranes for Biomedical Applications)

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18 pages, 3171 KB

Open AccessEditor’s ChoiceReview

A Short Review of Advances in MOF Glass Membranes for Gas Adsorption and Separation

by Zichen Li, Yumei Wang, Jianxin Zhang, Shiqi Cheng and Yue Sun

Membranes 2024, 14(5), 99; https://doi.org/10.3390/membranes14050099 - 25 Apr 2024

Cited by 17 | Viewed by 7779

Abstract

The phenomenon of melting in metal–organic frameworks (MOFs) has recently garnered attention. Crystalline MOF materials can be transformed into an amorphous glassy state through melt-quenching treatment. The resulting MOF glass structure eliminates grain boundaries and retains short-range order while exhibiting long-range disorder. Based [...] Read more.

The phenomenon of melting in metal–organic frameworks (MOFs) has recently garnered attention. Crystalline MOF materials can be transformed into an amorphous glassy state through melt-quenching treatment. The resulting MOF glass structure eliminates grain boundaries and retains short-range order while exhibiting long-range disorder. Based on these properties, it emerges as a promising candidate for high-performance separation membranes. MOF glass membranes exhibit permanent and accessible porosity, allowing for selective adsorption of different gas species. This review summarizes the melting mechanism of MOFs and explores the impact of ligands and metal ions on glassy MOFs. Additionally, it presents an analysis of the diverse classes of MOF glass composites, outlining their structures and properties, which are conducive to gas adsorption and separation. The absence of inter-crystalline defects in the structures, coupled with their distinctive mechanical properties, renders them highly promising for industrial gas separation applications. Furthermore, this review provides a summary of recent research on MOF glass composite membranes for gas adsorption and separation. It also addresses the challenges associated with membrane production and suggests future research directions. Full article

(This article belongs to the Special Issue Recent Advances of Metal–Organic Framework Membranes for Separation Process)

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24 pages, 2757 KB

Open AccessEditor’s ChoiceReview

Recent Advances and Challenges in Anion Exchange Membranes Development/Application for Water Electrolysis: A Review

by Lu Liu, Hongyang Ma, Madani Khan and Benjamin S. Hsiao

Membranes 2024, 14(4), 85; https://doi.org/10.3390/membranes14040085 - 5 Apr 2024

Cited by 51 | Viewed by 18238

Abstract

In recent years, anion exchange membranes (AEMs) have aroused widespread interest in hydrogen production via water electrolysis using renewable energy sources. The two current commercial low-temperature water electrolysis technologies used are alkaline water electrolysis (AWE) and proton exchange membrane (PEM) water electrolysis. The [...] Read more.

In recent years, anion exchange membranes (AEMs) have aroused widespread interest in hydrogen production via water electrolysis using renewable energy sources. The two current commercial low-temperature water electrolysis technologies used are alkaline water electrolysis (AWE) and proton exchange membrane (PEM) water electrolysis. The AWE technology exhibited the advantages of high stability and increased cost-effectiveness with low hydrogen production efficiency. In contrast, PEM water electrolysis exhibited high hydrogen efficiency with low stability and cost-effectiveness, respectively. Unfortunately, the major challenges that AEMs, as well as the corresponding ion transportation membranes, including alkaline hydrogen separator and proton exchange membranes, still face are hydrogen production efficiency, long-term stability, and cost-effectiveness under working conditions, which exhibited critical issues that need to be addressed as a top priority. This review comprehensively presented research progress on AEMs in recent years, providing a thorough understanding of academic studies and industrial applications. It focused on analyzing the chemical structure of polymers and the performance of AEMs and established the relationship between the structure and efficiency of the membranes. This review aimed to identify approaches for improving AEM ion conductivity and alkaline stability. Additionally, future research directions for the commercialization of anion exchange membranes were discussed based on the analysis and assessment of the current applications of AEMs in patents. Full article

(This article belongs to the Collection Feature Papers in Membrane Processing and Engineering)

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17 pages, 2949 KB

Open AccessEditor’s ChoiceArticle

Hydrophilic Modification of Dialysis Membranes Sustains Middle Molecule Removal and Filtration Characteristics

by Adam M. Zawada, Karlee Emal, Eva Förster, Saeedeh Saremi, Dirk Delinski, Lukas Theis, Florian Küng, Wenhao Xie, Joanie Werner, Manuela Stauss-Grabo, Matthias Faust, Skyler Boyington and James P. Kennedy

Membranes 2024, 14(4), 83; https://doi.org/10.3390/membranes14040083 - 3 Apr 2024

Cited by 4 | Viewed by 5250

Abstract

While efficient removal of uremic toxins and accumulated water is pivotal for the well-being of dialysis patients, protein adsorption to the dialyzer membrane reduces the performance of a dialyzer. Hydrophilic membrane modification with polyvinylpyrrolidone (PVP) has been shown to reduce protein adsorption and [...] Read more.

While efficient removal of uremic toxins and accumulated water is pivotal for the well-being of dialysis patients, protein adsorption to the dialyzer membrane reduces the performance of a dialyzer. Hydrophilic membrane modification with polyvinylpyrrolidone (PVP) has been shown to reduce protein adsorption and to stabilize membrane permeability. In this study we compared middle molecule clearance and filtration performance of nine polysulfone-, polyethersulfone-, and cellulose-based dialyzers over time. Protein adsorption was simulated in recirculation experiments, while β2-microglobulin clearance as well as transmembrane pressure (TMP) and filtrate flow were determined over time. The results of this study showed that β2-microglobulin clearance (−7.2 mL/min/m²) and filtrate flow (−54.4 mL/min) decreased strongly during the first 30 min and slowly afterwards (−0.7 mL/min/m² and −6.8 mL/min, respectively, for the next 30 min); the TMP increase (+37.2 mmHg and +8.6 mmHg, respectively) showed comparable kinetics. Across all tested dialyzers, the dialyzer with a hydrophilic modified membrane (FX CorAL) had the highest β2-microglobulin clearance after protein fouling and the most stable filtration characteristics. In conclusion, hydrophilic membrane modification with PVP stabilizes the removal capacity of middle molecules and filtration performance over time. Such dialyzers may have benefits during hemodiafiltration treatments which aim to achieve high exchange volumes. Full article

(This article belongs to the Topic Nephrology and Dialysis: From Bench to Bedside)

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19 pages, 5158 KB

Open AccessEditor’s ChoiceArticle

Experimental Investigation on the Energy and Exergy Efficiency of the Vacuum Membrane Distillation System with Its Various Configurations

by Abdullah Najib, Turki Mana, Emad Ali, Hany Al-Ansary, Fahad Awjah Almehmadi and Mansour Alhoshan

Membranes 2024, 14(2), 54; https://doi.org/10.3390/membranes14020054 - 13 Feb 2024

Cited by 2 | Viewed by 2949

Abstract

This paper addresses a retrofitting vacuum membrane distillation (VMD) setup to reduce the accumulated pressure inside the permeated side. This modification is necessary to extend the operation of the VMD to extreme operation conditions of higher hot water temperatures. This modification, denoted as [...] Read more.

This paper addresses a retrofitting vacuum membrane distillation (VMD) setup to reduce the accumulated pressure inside the permeated side. This modification is necessary to extend the operation of the VMD to extreme operation conditions of higher hot water temperatures. This modification, denoted as a hybrid configuration, proposes the injection of a cold water stream into the VMD cell without mixing it with the permeate. Energy and exergy efficiency analyses were performed to assess the effectiveness of the hybrid configuration. The performance of the modified system indicated an improvement in terms of permeate flux (J), the gain output ratio (GOR), and the utilitarian exergetic efficiency (η_ex,u), which reach up to two and three times that of the base configuration of the VMD system. However, the exergetic efficiency (η_ex) of the hybrid system showed marginal improvement compared to the base case over the tested range of hot water temperatures. This is because the enhanced vapor production is penalized by excess energy consumption. Moreover, the highest exergy destruction percentages occurred in the operational components (e.g., heater and chillers) which fall in the range of 19.0–68.9%. The exergy destruction percentage in the original components (e.g., the VMD cell and condenser) did not exceed 8.3%. Furthermore, this study indicated that the hybrid configuration requires additional tuning and optimization to perform efficiently over wide operating conditions. Full article

(This article belongs to the Special Issue Applications of Membrane Processes in Desalination, Wastewater Treatment and Resource Recovery)

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