Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
9.4
4.2
Journals
Membranes
Editor’s Choice
share announcement

Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

Order results
Result details
Results per page
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
28 pages, 3722 KB  
Review
Membrane Separation for Rare Earth Elements (A Review)
by Aaron T. Ben-Elijah, Tammy M. Lutz-Rechtin, S. Ranil Wickramasinghe and Xiaoyu Wang
Membranes 2026, 16(2), 69; https://doi.org/10.3390/membranes16020069 - 19 Feb 2026
Cited by 8 | Viewed by 3102
Abstract
Rare earth elements (REEs) are increasingly critical for advanced technologies like high-tech electronic devices, electric vehicles, catalysts, and supercapacitors. However, separating and purifying the REEs is challenging due to their similar physicochemical properties, such as ionic sizes and oxidation states. Traditional methods like [...] Read more.
Rare earth elements (REEs) are increasingly critical for advanced technologies like high-tech electronic devices, electric vehicles, catalysts, and supercapacitors. However, separating and purifying the REEs is challenging due to their similar physicochemical properties, such as ionic sizes and oxidation states. Traditional methods like solvent extraction require extensive use of organic solvents, involving multiple stages that generate large volumes of acidic liquid wastes. This article introduces membrane separation technologies as a more efficient approach that minimizes waste generation and offers higher selectivity and recovery rates in a single step. Membrane separation methods utilize free energy gradients and differences in ionic size or material affinity to selectively reject or allow ion adsorption and diffusion through the membrane pores. In this review paper, we critically evaluate recent advancements in the development and implementation of membrane-based systems and focus on exploring different membrane materials for REE separation, including polymer inclusion membranes, ion-imprinted membranes, nanofiltration membranes, electrodialysis membranes, metal-organic frameworks, and supported liquid membranes. The advantages, potential challenges, and technical issues with implementing these technologies are discussed, and possible areas for improvement and insights for further research are presented. Full article
(This article belongs to the Special Issue Application of Membrane-Based Modern Solutions in Separation Techniques for the Recovery of Metal Ions and Critical Resources)
►▼ Show Figures

Figure 1

37 pages, 3442 KB  
Review
Direct Contact Membrane Distillation: A Critical Review of Transmembrane Heat and Mass Transfer Models
by Nunzio Cancilla, Andrea Cipollina, Luigi Gurreri and Michele Ciofalo
Membranes 2026, 16(2), 64; https://doi.org/10.3390/membranes16020064 - 2 Feb 2026
Cited by 2 | Viewed by 2375
Abstract
The present review summarizes a vast body of literature on the subject of Membrane Distillation (MD), with a special emphasis on the existing results and correlations for the transmembrane transport of heat and mass. The issue of saltwater physical properties is also discussed [...] Read more.
The present review summarizes a vast body of literature on the subject of Membrane Distillation (MD), with a special emphasis on the existing results and correlations for the transmembrane transport of heat and mass. The issue of saltwater physical properties is also discussed in depth, whereas the advective transport of heat and salt concentration in the feed and permeate compartments is only briefly mentioned but is beyond the scope of this review. The paper does not aim to provide a complete treatment of the subject of MD, which can be found in other publications. Rather, it suggests the data and correlations most suitable for the range of operating conditions typically expected in actual units implementing Direct Contact Membrane Distillation (DCMD), including hollow fiber designs, with a view to assist model development. The focus is on MD for water desalination, although some results may apply well to other fields. Full article
(This article belongs to the Special Issue Membrane Distillation and Other Membrane-Related Applications for Water Cleaning and Desalination)
►▼ Show Figures

Figure 1

15 pages, 1595 KB  
Article
Influence of Module Design and Concentration Polarization on Pore Size Determination for Nanofiltration Membranes
by Henrik Schröter and Udo Kragl
Membranes 2026, 16(2), 60; https://doi.org/10.3390/membranes16020060 - 2 Feb 2026
Cited by 2 | Viewed by 1055
Abstract
Nanofiltration is an important part of pressure-driven membrane separation processes. A comprehensive understanding of the interplay between module hydrodynamics, concentration polarization, and solute rejection is essential for predicting NF performance and for scaling up processes. For two different membrane modules, the characterization and [...] Read more.
Nanofiltration is an important part of pressure-driven membrane separation processes. A comprehensive understanding of the interplay between module hydrodynamics, concentration polarization, and solute rejection is essential for predicting NF performance and for scaling up processes. For two different membrane modules, the characterization and determination of concentration polarization as well as pore-size determination according to the Donnan steric pore model are described. The results show that an optimized channel design allows for a more reliable determination of true retention rates without concentration polarization. Differences between observed retention rates and intrinsic retention rates considering mass transfer coefficients can be neglected. These results are obtained at significantly lower cross-flow rates, allowing for better applicability at the lab scale. Full article
(This article belongs to the Section Membrane Fabrication and Characterization)
►▼ Show Figures

Graphical abstract

24 pages, 2252 KB  
Review
Structural Design and Performance Optimization of Proton Exchange Membranes for Water Electrolysis: A Review
by Yi Chen, Hongyang Ma and Benjamin S. Hsiao
Membranes 2026, 16(2), 54; https://doi.org/10.3390/membranes16020054 - 31 Jan 2026
Cited by 5 | Viewed by 2784
Abstract
The trade-off between the ionic conductivity and the stability of the proton exchange membrane (PEM) is a major concern in the development of PEM water electrolysis (PEMWE). This review focuses on the design and fabrication of homogeneous and composite PEMs for water electrolysis [...] Read more.
The trade-off between the ionic conductivity and the stability of the proton exchange membrane (PEM) is a major concern in the development of PEM water electrolysis (PEMWE). This review focuses on the design and fabrication of homogeneous and composite PEMs for water electrolysis and establishes the structure–performance relationships between the membrane chemical/physical structures and their efficiency metrics—specifically, proton conductivity, hydrogen permeability, and chemical and mechanical stability. A special focus is placed on the fundamental connection between the microstructure and performance of membrane materials. At the molecular level, we systematically illustrate the design principles for main chains, side chains, and sulfonate groups, covering both fluorinated PEMs (encompassing perfluorinated and partially fluorinated membranes) and non-fluorinated PEMs (including aromatic polymers with heteroatom backbones and all-carbon backbones). At the macroscopic level, the review provides an in-depth exploration of two primary modification strategies: creating composites with organic polymers and with inorganic nanofillers. In summary, this review elucidates how these composite approaches leverage material synergies to improve the membrane’s mechanical integrity, proton conduction efficiency, and chemical resistance and offers a theoretical framework for the rational design of next-generation, high-performance PEMs to advance the commercialization of PEMWE technology. Full article
►▼ Show Figures

Graphical abstract

21 pages, 5659 KB  
Article
Development of High-Performance Catalytic Ceramic Membrane Microchannel Reactor for Carbon Dioxide Conversion to Methanol
by Aubaid Ullah, Nur Awanis Hashim, Mohamad Fairus Rabuni, Mohd Usman Mohd Junaidi, Ammar Ahmed, Mustapha Grema Mohammed and Muhammed Sahal Siddique
Membranes 2026, 16(1), 45; https://doi.org/10.3390/membranes16010045 - 17 Jan 2026
Viewed by 1677
Abstract
Conversion of carbon dioxide (CO2) to methanol in a traditional reactor (TR) with catalytic packed bed faces the challenge of lower reactant conversion due to thermodynamic limitations. On the contrary, membrane reactors selectively remove reaction products, enhancing the conversion, but it [...] Read more.
Conversion of carbon dioxide (CO2) to methanol in a traditional reactor (TR) with catalytic packed bed faces the challenge of lower reactant conversion due to thermodynamic limitations. On the contrary, membrane reactors selectively remove reaction products, enhancing the conversion, but it is still limited, and existing designs face challenges of structural integrity and scale-up complications. Therefore, for the first time, a ceramic membrane microchannel reactor (CMMR) system was developed with 500 µm deep microchannels, incorporated with catalytic membrane for CO2 conversion to methanol. Computational fluid dynamic (CFD) simulations confirmed the uniform flow distribution among the microchannels. A catalytic LTA zeolite membrane was synthesized with thin layer (~45 µm) of Cu-ZnO-Al2O3 catalyst coating and tested at a temperature of 220 °C and 3.0 MPa pressure. The results showed a significantly higher CO2 conversion of 82%, which is approximately 10 times higher than TR and 3 times higher than equilibrium conversion while 1.5 times higher than conventional tubular membrane reactor. Additionally, methanol selectivity and yield were achieved as 51.6% and 42.3%, respectively. The research outputs showed potential of replacing the current industrial process of methanol synthesis, addressing the Sustainable Development Goals of SDG-7, 9, and 13 for clean energy, industry innovation, and climate action, respectively. Full article
(This article belongs to the Special Issue Ceramic Membranes: Preparation, Modification and Multidisciplinary Applications)
►▼ Show Figures

Figure 1

14 pages, 3013 KB  
Article
Silicalite Nanosheet Laminated Membranes: Effects of Layered Structure on the Performance in Pervaporation Desalination
by Xinhui Sun, Yukta Sharma, Landysh Iskhakova, Zishu Cao and Junhang Dong
Membranes 2026, 16(1), 32; https://doi.org/10.3390/membranes16010032 - 4 Jan 2026
Cited by 1 | Viewed by 1110
Abstract
Silicalite nanosheet (SN) laminated membranes are promising for pervaporation (PV) desalination of concentrated brines for water purification and critical material concentration and recovery. However, scaling up the SN-based membranes is limited by inefficient synthesis of monodispersed open-pore SN single crystals (SNS). Here, we [...] Read more.
Silicalite nanosheet (SN) laminated membranes are promising for pervaporation (PV) desalination of concentrated brines for water purification and critical material concentration and recovery. However, scaling up the SN-based membranes is limited by inefficient synthesis of monodispersed open-pore SN single crystals (SNS). Here, we report a scalable approach to fabricate multilayered silicalite nanosheet plate (SNP) laminated membranes on porous alumina and PVDF substrates and demonstrate their excellent PV desalination performance for simulated brines containing lithium and high total dissolved salts (TDS). At 73 ± 3 °C, the SNP laminated membrane on alumina support achieved a remarkable water flux (Jw) of nearly 20 L/m2·h, significantly outperforming the alumina-supported SNS laminated membrane (Jw = 9.56 L/m2·h), while both provided near-complete salt rejection (ri ~99.9%) when operating with vacuum pressure on the permeate side. The PVDF-supported SNS and SNP laminated membranes exhibited excellent Jw (14.0 L/m2·h) and near-complete ri (>99.9%), surpassing the alumina-support SNP laminated membranes when operating by air sweep on the permeate side. However, the ri of the PVDF-supported membranes was found to decline when operating with vacuum pressure on the permeate side that was apparently caused by minimal liquid permeation through the inter-SNP spaces driven by the transmembrane pressure. With scalable SNP production, SNP-A membranes show potential for PV desalination of high-TDS solutions, especially in harsh environments unsuitable for polymer membranes. Full article
(This article belongs to the Special Issue Advanced Membrane Technologies for the Treatment of Industrial Wastewater and Emerging Contaminants: Challenges and Innovations)
►▼ Show Figures

Figure 1

19 pages, 3824 KB  
Article
Development of Chitosan Polymer Membranes with Potential Use in Filtration Processes
by Ana Luisa Aguilar-Ruiz, Tomás Jesús Madera-Santana, Reyna G. Sánchez-Duarte, Yedidia Villegas-Peralta, Ana Alejandra Aguilar-Ruiz and Víctor Manuel Orozco-Carmona
Membranes 2026, 16(1), 31; https://doi.org/10.3390/membranes16010031 - 4 Jan 2026
Cited by 1 | Viewed by 1849
Abstract
Polymeric membranes based on chitosan (Cs) were extracted from shrimp shells and evaluated. These membranes were modified using polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and glycerol (Gly) and crosslinked with glutaraldehyde (GA) to examine their suitability for water filtration processes. The Cs exhibited high [...] Read more.
Polymeric membranes based on chitosan (Cs) were extracted from shrimp shells and evaluated. These membranes were modified using polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and glycerol (Gly) and crosslinked with glutaraldehyde (GA) to examine their suitability for water filtration processes. The Cs exhibited high purity, a total nitrogen content of 6.49%, and an average molecular weight of 456 kDa, all of which are suitable for membrane formation. Four membranes (Cs-GA, B2: Cs-PEG, B5: Cs-PEG-PVP, and B7: Cs-Gly) were characterized by means of FTIR, SEM, AFM, thickness, contact angle, tensile testing, TGA, DSC, and filtration with distilled water at 4.83 bar. B2 and B5 showed thicknesses of 207 and 190 μm and contact angles of 56.7° and 58.9°, lower than that of Cs-GA (89.4°). In filtration, B2 achieved a flux of 2222.70 LMH, a permeance of 460.19 LMH·bar−1, and a hydraulic resistance of 8.79 × 1011 m−1, while Cs-GA, B5, and B7 exhibited fluxes of 24.10, 40.43, and 24.77 LMH, respectively, permeances of 9.75, 8.37, and 5.13 LMH·bar−1, and hydraulic resistances of 4.15 × 1013, 4.83 × 1013, and 7.89 × 1013 m−1, in the same order. Overall, membranes B2 and B5 are recognized as the most promising for water filtration under pressured operating conditions. Full article
(This article belongs to the Special Issue Recent Advances in Polymeric Membranes—Preparation and Applications (2nd Edition))
►▼ Show Figures

Figure 1

19 pages, 8676 KB  
Article
Towards a Circular Economy in Electroless Pore-Plated Pd/PSS Composite Membranes: Pd Recovery and Porous Support Reuse
by Alejandro J. Santos-Carballes, David Alique, Raúl Sanz, Arturo J. Vizcaíno and José A. Calles
Membranes 2026, 16(1), 28; https://doi.org/10.3390/membranes16010028 - 4 Jan 2026
Viewed by 933
Abstract
The recycling of a planar composite Pd membrane over a porous stainless-steel support modified with a CeO2 interlayer (Pd/CeO2/PSS) was investigated using a leaching-based recycling strategy to recover palladium while maintaining the support’s structural integrity. The membrane was prepared by [...] Read more.
The recycling of a planar composite Pd membrane over a porous stainless-steel support modified with a CeO2 interlayer (Pd/CeO2/PSS) was investigated using a leaching-based recycling strategy to recover palladium while maintaining the support’s structural integrity. The membrane was prepared by a continuous flowing electroless pore-plating method (cf-ELP-PP) previously developed by our group. A series of experiments was conducted to evaluate the effect of leaching conditions—temperature, acid concentration, and duration—on Pd extraction and support preservation. Nitric acid (HNO3) was used as the leaching agent, and the condition of 30 vol.% HNO3 at 35 °C for 24 h was found to enable complete Pd recovery with limited dissolution of metals from the support. The regenerated supports exhibited an Fe-Cr oxide layer and part of the CeO2 interface, allowing the elimination of cleaning and calcination steps in the membrane reprocessing workflow. A new Pd-CeO2 interfacial layer was applied, followed by Pd redeposition via cf-ELP-PP. The resulting recycled membrane exhibited a homogeneous and defect-free Pd layer, with hydrogen permeation performance comparable to that of membranes fabricated on fresh supports. These results demonstrate that Pd membranes can be successfully fabricated on recycled 316L stainless-steel substrates, supporting the viability of this approach for material reuse in membrane technology. Full article
(This article belongs to the Special Issue Membrane Technologies in Hydrogen Separation and Purification)
►▼ Show Figures

Figure 1

16 pages, 5762 KB  
Article
Evaluation of Flat Sheet UF PES Membranes Modified with a Polymerized Coating of Bicontinuous Microemulsion for Wastewater Treatment: Insights from Laboratory MBR Experiments
by Sneha De, Tran Ly Quynh, Francesco Galiano, Raffaella Mancuso, Bartolo Gabriele, Jan Hoinkis and Alberto Figoli
Membranes 2026, 16(1), 24; https://doi.org/10.3390/membranes16010024 - 2 Jan 2026
Viewed by 1212
Abstract
The study investigates the performance of polyethersulfone (PES) ultrafiltration (UF) membranes modified with a coating of polymerizable bicontinuous microemulsion (PBM) for membrane bioreactor (MBR) applications. Two types of PBM-modified PES membranes—casting-coated and spray-coated—were compared with a commercial PES membrane. A laboratory side-stream MBR [...] Read more.
The study investigates the performance of polyethersulfone (PES) ultrafiltration (UF) membranes modified with a coating of polymerizable bicontinuous microemulsion (PBM) for membrane bioreactor (MBR) applications. Two types of PBM-modified PES membranes—casting-coated and spray-coated—were compared with a commercial PES membrane. A laboratory side-stream MBR (ssMBR) was employed to treat model wastewater (MW) with activated sludge under aerobic conditions. The fouling propensity of the membranes in ssMBR was evaluated through the implementation of two protocols: (i) flux-step test to treat low-strength domestic model wastewater (DMW) and (ii) constant flux test to treat high-strength olive mill model wastewater (OMW). The findings indicated that both the commercial PES and PBM spray-coated PES membranes started to critically foul at 36 L m−2 h−1. The PBM spray-coated membranes showed enhanced fouling resistance in comparison to the PBM casting-coated membranes. The deposition of the biofouling layer was the thinnest on PBM spray-coated membranes, which can be attributed to the low surface charge and high hydrophilicity of the modified membrane surface. In contrast, deposition of a thicker fouling layer was found on the commercial PES membrane, which can be attributed to the relatively higher surface charge promoting organic adsorption. A comparison of the fouling trends exhibited by commercial PES and PBM spray-coated membranes in OMW treatment revealed that they have similar fouling tendencies. However, a notable distinction emerged when the PBM spray-coated membrane was observed to demonstrate a lower fouling propensity accompanied by comparatively thinner fouling layers. The results demonstrate that the PBM spray-coated membranes have enhanced fouling resistance and filtration efficacy in MBRs treating wastewater with diverse strengths, thereby affirming their potential for application in wastewater treatment systems. Full article
(This article belongs to the Special Issue Advanced Membrane Technologies for the Treatment of Industrial Wastewater and Emerging Contaminants: Challenges and Innovations)
►▼ Show Figures

Figure 1

19 pages, 4005 KB  
Review
Efficient Separation of Per- and Polyfluoroalkyl Substances (PFAS) by Organic Framework Membranes: Advances, Mechanisms, and Challenges
by Jiawei Zhang, Baosheng Zhao and Hao Yang
Membranes 2026, 16(1), 19; https://doi.org/10.3390/membranes16010019 - 1 Jan 2026
Cited by 2 | Viewed by 2332
Abstract
Per- and polyfluoroalkyl substances (PFAS) represent a class of highly persistent environmental contaminants with exceptional chemical stability. Efficient removal of PFAS from water poses a significant challenge for the chemical industry and constitutes a critical requirement for sustainable environmental development. Membrane technology has [...] Read more.
Per- and polyfluoroalkyl substances (PFAS) represent a class of highly persistent environmental contaminants with exceptional chemical stability. Efficient removal of PFAS from water poses a significant challenge for the chemical industry and constitutes a critical requirement for sustainable environmental development. Membrane technology has demonstrated considerable potential in water treatment due to its low energy consumption and environmentally friendly characteristics. This review comprehensively summarizes recent advances in emerging metal–organic framework (MOF)-, covalent organic framework (COF)-, and hydrogen-bonded organic framework (HOF)-based membranes for highly efficient separation and catalytic degradation of PFAS. We provide a detailed analysis of design strategies for various organic framework membranes (OFMs) and their synergistic separation mechanisms, including size exclusion, electrostatic interactions, adsorption, as well as catalytic degradation based on advanced oxidation processes. Furthermore, we systematically evaluate the performance and applicability of these membranes in practical aquatic environments. Finally, this review outlines future directions toward developing integrated “separation-degradation” membrane processes for practical applications by discussing current challenges concerning material stability, manufacturing costs, and long-term operational efficiency. This review aims to provide theoretical guidance and technical insights for developing next-generation high-performance membranes for PFAS removal. Full article
(This article belongs to the Special Issue Preparation, Characterization, and Application of Advanced Separation Membrane Materials)
►▼ Show Figures

Graphical abstract

24 pages, 5297 KB  
Article
A Hybrid CFD Platform for Colloidal Fouling Prediction in Electrodialysis
by Francesco Volpe, Giuseppe Battaglia, Andrea Cipollina, Giorgio Micale and Alessandro Tamburini
Membranes 2025, 15(12), 375; https://doi.org/10.3390/membranes15120375 - 6 Dec 2025
Viewed by 1184
Abstract
Fouling phenomena are among the main issues in membrane processes, worsening unit performance and membrane properties. So far, few modelling approaches have been proposed to predict colloidal fouling in electromembrane-based technologies. This work presents an original simulation platform that couples computational fluid dynamics [...] Read more.
Fouling phenomena are among the main issues in membrane processes, worsening unit performance and membrane properties. So far, few modelling approaches have been proposed to predict colloidal fouling in electromembrane-based technologies. This work presents an original simulation platform that couples computational fluid dynamics (CFD) simulations with electrodialysis (ED) and colloidal fouling models to investigate the impact of colloidal deposition at the channel and unit scales of ED systems. Fluid dynamics, salt transport and fouling layer growth were all addressed. The model was calibrated and validated with colloidal fouling data from the literature. The regions more susceptible to fouling growth were identified. Polarization phenomena, as well as the increase in pressure losses and electrical resistance over time, were evaluated. Full article
(This article belongs to the Special Issue Electrodialysis and Reverse Electrodialysis in Ion-Exchange Membrane Systems)
►▼ Show Figures

Graphical abstract

13 pages, 1460 KB  
Article
Numerical Assessment of Elliptical Pore Orientation and Eccentricity Effects on Charge Transport in Anisotropic Functional Membranes
by Carlos Pacheco, Alfonso Navarro, Enrique Escobedo and Romeli Barbosa
Membranes 2025, 15(12), 370; https://doi.org/10.3390/membranes15120370 - 2 Dec 2025
Cited by 1 | Viewed by 936
Abstract
The transport efficiency of anisotropic functional membranes is largely dictated by the geometry and orientation of their internal pores. In this study, a numerical finite-volume framework was developed to evaluate how elliptical pore eccentricity (εcc) and orientation influence charge [...] Read more.
The transport efficiency of anisotropic functional membranes is largely dictated by the geometry and orientation of their internal pores. In this study, a numerical finite-volume framework was developed to evaluate how elliptical pore eccentricity (εcc) and orientation influence charge transport and effective conductivity (ek) within two-dimensional porous membrane microstructures. Canonical stochastic domains with controlled porosity were generated, considering parallel and perpendicular aligned configurations of the major pore axis relative to the imposed potential gradient. Results demonstrated a strong orientation dependence: under perpendicular alignment, the effective conductivity decreased by up to 70% as εcc increased from 0.5 to 0.999, while parallel alignment maintained at ek > 0.8 even for highly elongated pores. The aspect ratio (b/a) was identified as a secondary geometric modulator producing opposite conductivity trends depending on orientation. Through isotropy-error analysis, a critical morphological threshold at εcc ≈ 0.9 was found, indicating the onset of structural anisotropy and loss of isotropic transport. These results establish a quantitative structure–property relationship linking pore geometry to macroscopic transport performance. The proposed stochastic FVM-based approach provides a generalizable and computationally efficient tool for the design and optimization of anisotropic porous membranes used in electrochemical and energy-conversion devices. Full article
(This article belongs to the Section Membrane Fabrication and Characterization)
►▼ Show Figures

Figure 1

17 pages, 1560 KB  
Review
Biological Breakthroughs and Drug Discovery Revolution via Cryo-Electron Microscopy of Membrane Proteins
by Vitor Hugo Balasco Serrão
Membranes 2025, 15(12), 368; https://doi.org/10.3390/membranes15120368 - 1 Dec 2025
Cited by 1 | Viewed by 3723
Abstract
The application of cryo-electron microscopy (cryo-EM) in membrane protein structural biology has catalyzed unprecedented advances in our understanding of fundamental biological processes and transformed drug discovery paradigms. This review briefly describes the biological achievements enabled using cryo-EM techniques, including single particle analysis (SPA), [...] Read more.
The application of cryo-electron microscopy (cryo-EM) in membrane protein structural biology has catalyzed unprecedented advances in our understanding of fundamental biological processes and transformed drug discovery paradigms. This review briefly describes the biological achievements enabled using cryo-EM techniques, including single particle analysis (SPA), micro-electron diffraction (microED), and subtomogram averaging (STA), in elucidating the structures and functions of membrane proteins, ion channels, transporters, and viral glycoproteins. We highlight how these structural insights have revealed druggable sites, enabled structure-based drug design, and provided mechanistic understanding of disease processes. Key biological targets include G protein-coupled receptors (GPCRs), ion channels implicated in neurological disorders, respiratory chain complexes, viral entry machinery, and membrane transporters. The integration of cryo-EM with computational drug design has already yielded clinical candidates and approved therapeutics, marking a new era in membrane protein pharmacology. Full article
(This article belongs to the Special Issue Biomolecular Interactions with Cell and Model Membranes: Integrating Biophysical Experiments and Computational Simulations)
►▼ Show Figures

Figure 1

21 pages, 8827 KB  
Article
Effect of Seed Size on Pervaporation Performances Through FAU Zeolite Membrane
by Alvin Rahmad Widyanto and Mikihiro Nomura
Membranes 2025, 15(12), 355; https://doi.org/10.3390/membranes15120355 - 25 Nov 2025
Cited by 2 | Viewed by 1558
Abstract
Pervaporation is a compelling alternative to azeotrope-breaking and solvent dehydration due to lower energy demand and strong selectivity compared with distillation. FAU-type zeolite membranes combine large pore openings and hydrophilic frameworks with robust chemical stability, enabling water-selective separations from alcohols such as isopropanol [...] Read more.
Pervaporation is a compelling alternative to azeotrope-breaking and solvent dehydration due to lower energy demand and strong selectivity compared with distillation. FAU-type zeolite membranes combine large pore openings and hydrophilic frameworks with robust chemical stability, enabling water-selective separations from alcohols such as isopropanol and ethanol. Despite numerous synthesis routes, the role of seed crystal size in secondary growth, controlling nucleation density, intergrowth, and defect formation remains insufficiently quantified for FAU membranes under identical growth conditions. Here, FAU layers were fabricated on α-Al2O3 supports via secondary growth with varying seed sizes in the nanometer-to-micrometer range (72 nm to 6 μm). Zeolite crystal phase purity and morphology of membranes were assessed by XRD and SEM, with pervaporation of IPA/water 80 wt% at 75 °C quantified flux, separation factor, and permeance. We show that smaller seeds (95.51 nm) increase nucleation density, yielding thinner, more intergrown FAU layers with a higher separation factor but a modest trade-off in flux. Full article
(This article belongs to the Special Issue Advances in Zeolite Membranes for Energy and Environmental Sustainability)
►▼ Show Figures

Figure 1

24 pages, 5623 KB  
Review
Nanocellulose–Graphene Derivative Composite Membranes: Recent Advances, Functional Mechanisms, and Water Purification Applications
by Hui Zhang, Shuyuan Lin, Yating Pan, Xin Wang, Hanzhou Zhang, Shuhan Liu, Zhen Li and Ning Wei
Membranes 2025, 15(12), 347; https://doi.org/10.3390/membranes15120347 - 21 Nov 2025
Cited by 5 | Viewed by 2098
Abstract
Nanocellulose–graphene derivative (NC–GD) composite membranes have attracted increasing attention as sustainable separation materials with high specific surface area, mechanical strength, and controllable interfacial chemistry. This review contextualizes the development of NC–GD composite membranes within advanced membrane technologies and summarizes recent progress in their [...] Read more.
Nanocellulose–graphene derivative (NC–GD) composite membranes have attracted increasing attention as sustainable separation materials with high specific surface area, mechanical strength, and controllable interfacial chemistry. This review contextualizes the development of NC–GD composite membranes within advanced membrane technologies and summarizes recent progress in their structural design, interfacial mechanisms, and water purification applications. The synthesis and assembly of nanocellulose and graphene derivatives are analyzed, focusing on how surface functionalization regulates interfacial compatibility and transport pathways. Comparative evaluation of fabrication approaches—including vacuum filtration, layer-by-layer assembly, and solution casting—highlights their influence on structural uniformity and permeability. Key findings indicate that hydrogen bonding, electrostatic coupling, and π–π interactions govern the layer stability of composite membranes and the synergistic formation of nanochannels (by NC and GDs), thereby enabling efficient water permeation, selective separation, and fouling resistance. Overall, NC–GD membranes exhibit outstanding performance in heavy metal adsorption, dye removal, oil–water separation, and antibacterial treatment, representing a promising platform for next-generation sustainable water purification systems. Full article
(This article belongs to the Special Issue Advanced Membrane Technologies for the Treatment of Industrial Wastewater and Emerging Contaminants: Challenges and Innovations)
►▼ Show Figures

Figure 1

16 pages, 5579 KB  
Article
Microscopic Exploration of Water Permeation and Ion Rejection for Edge Amine-Functionalized GO Nanoslits
by Yinfeng Pei, Wenjin Li and Xiaoning Yang
Membranes 2025, 15(11), 334; https://doi.org/10.3390/membranes15110334 - 4 Nov 2025
Cited by 1 | Viewed by 1344
Abstract
Layered graphene oxide (GO) has emerged as an ideal membrane structure for water desalination. In GO-stacked structures, the slit gaps between GO nanosheets can serve as critical pathways for molecule permeation. Exploring the permeation mechanisms of functionalized GO nanoslits is critical for improving [...] Read more.
Layered graphene oxide (GO) has emerged as an ideal membrane structure for water desalination. In GO-stacked structures, the slit gaps between GO nanosheets can serve as critical pathways for molecule permeation. Exploring the permeation mechanisms of functionalized GO nanoslits is critical for improving the separation performance. Herein, molecular simulations were performed to investigate the water permeation and ion rejection for six types of ionic solutions by considering edge-amino functionalized GO (NGO) slit membranes. The NGO slit exhibits higher ion retention while maintaining reasonable water permeability. Edge amine groups can interact strongly with water molecules and immobilize ions, thus enhancing ion rejection. The thermodynamic free energy for ion passing was simulated to explain the unique ion rejection mechanism of amine-functionalized GO slits. The thermodynamic barrier for ion rejection can be considered as the delicate combination of the ion dehydration effect and the slit-generated attraction. The ion dehydration accounts for a repulsive contribution, which is the controlling portion in governing the free-energy profile. Overall, our work is important and valuable for the development and design of new-type layered GO membranes. Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
►▼ Show Figures

Figure 1

24 pages, 815 KB  
Review
Recent Advances in Polymeric Membrane Integration for Organic Solvent Mixtures Separation: Mini-Review
by Abdellah Halloub and Wojciech Kujawski
Membranes 2025, 15(11), 329; https://doi.org/10.3390/membranes15110329 - 30 Oct 2025
Cited by 5 | Viewed by 3463
Abstract
Membrane technology offers considerable potential for enhancing or partially replacing conventional separation techniques, which could eventually lead to substantial energy savings. This review focuses on recent advancements in membrane separation technologies including organic solvent pervaporation (OSPV), organic solvent reverse osmosis (OSRO), organic solvent [...] Read more.
Membrane technology offers considerable potential for enhancing or partially replacing conventional separation techniques, which could eventually lead to substantial energy savings. This review focuses on recent advancements in membrane separation technologies including organic solvent pervaporation (OSPV), organic solvent reverse osmosis (OSRO), organic solvent nanofiltration (OSN), and organic solvent ultrafiltration (OSUF) that are increasingly vital in the pharmaceutical, biochemical, and petrochemical industries. Although hybrid and inorganic membranes exhibit promising performance, polymeric membranes provide advantages in scalability and processability. The development of materials capable of operating under demanding conditions that include exposure to organic solvents, high temperatures, extreme pH levels, and oxidative environments remains critical. Here, we examine recent innovations in membrane materials and their integration into organic solvent systems. Key challenges, including material swelling, fouling, and scaling, are discussed, along with recent strategies to address these issues. Finally, we identify emerging research directions that could drive further progress in membrane technology for organic media applications. Full article
(This article belongs to the Collection Featured Reviews in Membrane Science)
►▼ Show Figures

Figure 1

22 pages, 1293 KB  
Review
Single-Molecule Imaging and Super-Resolution Microscopy of Lipid Domains in Cell Membranes Using Lipid-Binding Proteins and Fluorophore-Conjugated Lipid Analogs
by Toshiki Mori and Kenichi G. N. Suzuki
Membranes 2025, 15(10), 317; https://doi.org/10.3390/membranes15100317 - 16 Oct 2025
Viewed by 3297
Abstract
Lipids are spatiotemporally organized in cell membranes, where they play indispensable roles in regulating diverse biological processes. Their distribution and dynamics are intricately coupled to signal transduction, membrane trafficking, and host–pathogen interactions. The past decade has seen substantial progress in the development of [...] Read more.
Lipids are spatiotemporally organized in cell membranes, where they play indispensable roles in regulating diverse biological processes. Their distribution and dynamics are intricately coupled to signal transduction, membrane trafficking, and host–pathogen interactions. The past decade has seen substantial progress in the development of lipid probes and imaging techniques, which have greatly advanced our understanding of lipid-mediated regulation in living cells. Chemically optimized lipid analogs conjugated with hydrophilic fluorophores have enabled the faithful visualization of raftophilic lipids, such as sphingomyelin, gangliosides, and cholesterol, while minimizing artifacts. In parallel, genetically encoded lipid sensors derived from lipid-binding protein domains have been established. These sensors selectively report the localization and dynamics of diverse lipid species, including phosphoinositides, cholesterol, sphingomyelin, and phosphatidylserine, in their native contexts. Combined with state-of-the-art advanced microscopy approaches, including ultrafast single-molecule imaging and super-resolution microscopy, these probes facilitate high-resolution and quantitative analyses of lipid organization. This review summarizes recent advances in both synthetic lipid probes and genetically encoded lipid sensors, emphasizing their applications in mechanistic studies of membrane biology. We further discuss current challenges and future directions toward the comprehensive and minimally perturbative visualization of lipids. Full article
(This article belongs to the Section Biological Membranes)
►▼ Show Figures

Figure 1

13 pages, 1099 KB  
Article
Photochemical Methods to Study the Radical-Induced Degradation of Anion-Exchange Membranes
by Panna Solyom, Thomas Nauser and Tamas Nemeth
Membranes 2025, 15(10), 305; https://doi.org/10.3390/membranes15100305 - 7 Oct 2025
Cited by 1 | Viewed by 1990
Abstract
We adapted two photochemical methods to generate radicals and assess their impact on anion exchange membrane stability, independent of base-induced degradation. Through the exposure of aqueous solutions of potassium nitrite or suspensions of TiO2 to UV light at 365 nm, we generated [...] Read more.
We adapted two photochemical methods to generate radicals and assess their impact on anion exchange membrane stability, independent of base-induced degradation. Through the exposure of aqueous solutions of potassium nitrite or suspensions of TiO2 to UV light at 365 nm, we generated hydroxyl radicals or a combination of hydroxyl and superoxide radicals. The methods’ applicability to anion exchange membranes (AEMs) is demonstrated on three commercial AEMs: PiperION-40, FM-FAA-3-PK-75, and PNB-R45. Changes in ion-exchange capacity, along with FT-IR and NMR analyses, revealed significant degradation in thinner, non-reinforced membranes, while thicker and reinforced membranes showed greater resistance. We attribute this to the limited penetration depth of highly reactive radicals into the membrane. Both methods are practical and inexpensive tools for benchmarking AEM stability against radical attack. Full article
(This article belongs to the Section Membrane Applications for Energy)
►▼ Show Figures

Figure 1

21 pages, 5920 KB  
Article
Enhanced CO2 Separation Performance of Mixed Matrix Membranes with Pebax and Amino-Functionalized Carbon Nitride Nanosheets
by Mengran Hua, Qinqin Sun, Na Li, Mingchao Zhu, Yongze Lu, Zhaoxia Hu and Shouwen Chen
Membranes 2025, 15(10), 306; https://doi.org/10.3390/membranes15100306 - 7 Oct 2025
Cited by 5 | Viewed by 1924
Abstract
Highly permeable and selective membranes are crucial for energy-efficient gas separation. Two-dimensional (2D) graphitic carbon nitride (g-C3N4) has attracted significant attention due to its unique structural characteristics, including ultra-thin thickness, inherent surface porosity, and abundant amine groups. However, the [...] Read more.
Highly permeable and selective membranes are crucial for energy-efficient gas separation. Two-dimensional (2D) graphitic carbon nitride (g-C3N4) has attracted significant attention due to its unique structural characteristics, including ultra-thin thickness, inherent surface porosity, and abundant amine groups. However, the interfacial defects caused by poor compatibility between g-C3N4 and polymers deteriorate the separation performance of membrane materials. In this study, amino-functionalized g-C3N4 nanosheets (CN@PEI) was prepared by a post-synthesis method, then blended with the polymer Pebax to fabricate Pebax/CN@PEI mixed matrix membranes (MMMs). Compared to g-C3N4, MMMs with CN@PEI loading of 20 wt% as nanofiller exhibited a CO2 permeance of 241 Barrer as well as the CO2/CH4 and CO2/N2 selectivity of 39.7 and 61.2, respectively, at the feed gas pressure of 2 bar, which approaches the 2008 Robeson upper bound and exceeded the 1991 Robeson upper bound. The Pebax/CN@PEI (20) membrane showed robust stability performance over 70 h continuous gas permeability testing, and no significant decline was observed. SEM characterization revealed a uniform dispersion of CN@PEI throughout the Pebax matrix, demonstrating excellent interfacial compatibility between the components. The increased free volume fraction, enhanced solubility, and higher diffusion coefficient demonstrated that the incorporation of CN@PEI nanosheets introduced more CO2-philic amino groups and disrupted the chain packing of the Pebax matrix, thereby creating additional diffusion channels and facilitating CO2 transport. Full article
(This article belongs to the Special Issue Novel Membranes for Carbon Capture and Conversion)
►▼ Show Figures

Figure 1

22 pages, 3747 KB  
Article
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
Cited by 1 | Viewed by 1958
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))
►▼ Show Figures

Figure 1

22 pages, 4596 KB  
Review
Microwave Synthesis in Zeolite and MOF Membranes
by Liangqing Li
Membranes 2025, 15(9), 275; https://doi.org/10.3390/membranes15090275 - 12 Sep 2025
Cited by 3 | Viewed by 2675
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)
►▼ Show Figures

Figure 1

40 pages, 4676 KB  
Review
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 16 | Viewed by 5922
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)
►▼ Show Figures

Figure 1

52 pages, 2709 KB  
Review
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 6 | Viewed by 9791
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)
►▼ Show Figures

Figure 1

14 pages, 2427 KB  
Article
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
Cited by 1 | Viewed by 4287
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)
►▼ Show Figures

Figure 1

24 pages, 2930 KB  
Article
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
Cited by 3 | Viewed by 2220
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)
►▼ Show Figures

Graphical abstract

38 pages, 9212 KB  
Review
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 17 | Viewed by 4594
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)
►▼ Show Figures

Graphical abstract

14 pages, 6077 KB  
Article
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 9 | Viewed by 2396
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)
►▼ Show Figures

Figure 1

21 pages, 4609 KB  
Review
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
Cited by 7 | Viewed by 5386
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)
►▼ Show Figures

Figure 1

24 pages, 1083 KB  
Review
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 22 | Viewed by 12743
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)
►▼ Show Figures

Figure 1

22 pages, 3169 KB  
Review
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 5 | Viewed by 2639
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)
►▼ Show Figures

Graphical abstract

11 pages, 1035 KB  
Article
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 2 | Viewed by 2012
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)
►▼ Show Figures

Figure 1

35 pages, 16650 KB  
Article
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 9 | Viewed by 3023
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 CaCl2 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)
►▼ Show Figures

Figure 1

12 pages, 7533 KB  
Article
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
Cited by 1 | Viewed by 2063
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)
►▼ Show Figures

Figure 1

46 pages, 4813 KB  
Review
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 13 | Viewed by 9844
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)
►▼ Show Figures

Graphical abstract

12 pages, 2694 KB  
Article
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
Cited by 3 | Viewed by 2537
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)
►▼ Show Figures

Figure 1

15 pages, 4044 KB  
Article
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 4 | Viewed by 2012
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)
►▼ Show Figures

Figure 1

13 pages, 34194 KB  
Article
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
Cited by 1 | Viewed by 1902
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)
►▼ Show Figures

Figure 1

25 pages, 6238 KB  
Article
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
Cited by 1 | Viewed by 2923
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)
►▼ Show Figures

Figure 1

26 pages, 1509 KB  
Review
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 10 | Viewed by 6266
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)
►▼ Show Figures

Figure 1

15 pages, 4409 KB  
Article
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 4 | Viewed by 3013
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)
►▼ Show Figures

Figure 1

15 pages, 2733 KB  
Article
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 15 | Viewed by 4760
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)
►▼ Show Figures

Figure 1

14 pages, 6671 KB  
Article
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 2 | Viewed by 5155
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)
►▼ Show Figures

Figure 1

14 pages, 3524 KB  
Article
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 9 | Viewed by 3810
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)
►▼ Show Figures

Figure 1

15 pages, 4739 KB  
Article
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 7 | Viewed by 5461
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)
►▼ Show Figures

Figure 1

16 pages, 4896 KB  
Article
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 18 | Viewed by 3637
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)
►▼ Show Figures

Figure 1

13 pages, 5627 KB  
Article
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 7 | Viewed by 2981
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)
►▼ Show Figures

Figure 1

16 pages, 48253 KB  
Article
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 5 | Viewed by 3049
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)
►▼ Show Figures

Figure 1

12 pages, 2800 KB  
Review
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 9 | Viewed by 5090
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)
►▼ Show Figures

Figure 1

19 pages, 8621 KB  
Article
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 13 | Viewed by 2917
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 (Rt), reversible fouling (Rr) and irreversible fouling (Rir) 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)
►▼ Show Figures

Figure 1

Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying article 1-50 on page 1 of 8.
Go to page     1 2 3 4 5 chevron_right last_page
Back to TopTop