Membranes

24 pages, 2278 KiB

Open AccessArticle

Performance Analysis of Silica Fluidized Bed Membrane Reactor for Hydrogen Production as a Green Process Using CFD Modelling

by Maryam Barmaki, Elham Jalilnejad, Kamran Ghasemzadeh and Adolfo Iulianelli

Membranes 2025, 15(8), 248; https://doi.org/10.3390/membranes15080248 - 18 Aug 2025

Abstract

The main aim of this study deals with the potential evaluation of a fluidized bed membrane reactor (FBMR) for hydrogen production as a clean fuel carrier via methanol steam reforming reaction, comparing its performance with other reactors including packed bed membrane reactors (PBMR), [...] Read more.

The main aim of this study deals with the potential evaluation of a fluidized bed membrane reactor (FBMR) for hydrogen production as a clean fuel carrier via methanol steam reforming reaction, comparing its performance with other reactors including packed bed membrane reactors (PBMR), fluidized bed reactors (FBR), and packed bed reactors (PBR). For this purpose, a two-dimensional, axisymmetric numerical model was developed using computational fluid dynamics (CFD) to simulate the reactor performances. Model accuracy was validated by comparing the simulation results for PBMR and PB with experimental data, showing an accurate agreement within them. The model was then employed to examine the effects of key operating parameters, including reaction temperature, pressure, steam-to-methanol molar ratio, and gas volumetric space velocity, on reactor performance in terms of methanol conversion, hydrogen yield, hydrogen recovery, and selectivity. At 573 K, 1 bar, a feed molar ratio of 3/1, and a space velocity of 9000 h⁻¹, the PBMR reached the best results in terms of methanol conversion, hydrogen yield, hydrogen recovery, and hydrogen selectivity, such as 67.6%, 69.5%, 14.9%, and 97.1%, respectively. On the other hand, the FBMR demonstrated superior performance with respect to the latter reaching a methanol conversion of 98.3%, hydrogen yield of 95.8%, hydrogen recovery of 74.5%, and hydrogen selectivity of 97.4%. These findings indicate that the FBMR offers significantly better performance than the other reactor types studied in this work, making it a highly efficient method for hydrogen production through methanol steam reforming, and a promising pathway for clean energy generation. Full article

(This article belongs to the Special Issue Membranes and Membrane Reactors for Gas Purification and Production: Towards More Sustainable Processes)

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17 pages, 2122 KiB

Open AccessArticle

Membrane Stress Enhances Specific PQS–Lipid Interactions That Drive Bacterial Outer Membrane Vesicle Biogenesis

by Citrupa Gopal, Hasan Al Tarify, Emad Pirhadi, Eliza G. O’Brien, Anuradha Dagar, Xin Yong and Jeffrey W. Schertzer

Membranes 2025, 15(8), 247; https://doi.org/10.3390/membranes15080247 - 13 Aug 2025

Abstract

Gram-negative bacteria use outer membrane vesicles (OMVs) for toxin trafficking, immune interference, horizontal gene transfer, antibiotic protection, and cell–cell communication. Despite their direct contribution to many pathogenesis-related behaviors, our understanding of how OMVs are produced remains surprisingly incomplete. The Bilayer Couple model describes [...] Read more.

Gram-negative bacteria use outer membrane vesicles (OMVs) for toxin trafficking, immune interference, horizontal gene transfer, antibiotic protection, and cell–cell communication. Despite their direct contribution to many pathogenesis-related behaviors, our understanding of how OMVs are produced remains surprisingly incomplete. The Bilayer Couple model describes the induction of OMV formation resulting from the preferential accumulation of small molecules in the outer leaflet of the membrane, resulting in leaflet expansion and membrane bending. Previous work has highlighted the importance of the structure of the Pseudomonas Quinolone Signal (PQS) in driving OMV formation, but the nature of interactions with membrane lipids remains unclear. Our recent in silico analysis suggested that a new interaction, between the PQS ring nitrogen and Lipid A, is critical for PQS function. Here, we used chemical analogs to interrogate the importance of specific PQS functional groups in its ability to stimulate OMV biogenesis. We demonstrated that OMV induction requires the presence of all PQS functional groups together. Further modeling uncovered that PQS prefers interaction with the outer leaflet of the membrane, consistent with its unique ability to drive OMV biogenesis. This was explained by much greater hydrogen bond formation between PQS and Lipid A. Interestingly, the preference of PQS for the outer leaflet coincided with that leaflet becoming crowded. Thus, the initial insertion of PQS into the outer leaflet would be expected to encourage local accumulation of more PQS to drive the induction of membrane curvature and subsequent OMV formation. Full article

(This article belongs to the Section Biological Membranes)

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52 pages, 2709 KiB

Open AccessReview

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

Abstract

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

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

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

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14 pages, 2427 KiB

Open AccessArticle

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

Abstract

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

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

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

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27 pages, 3538 KiB

Open AccessArticle

Novel Dual-Layer Zwitterionic Modification of Electrospun Nanofibrous Membrane for Produced Water Treatment and Reclamation

by Sunith B. Madduri and Raghava R. Kommalapati

Membranes 2025, 15(8), 244; https://doi.org/10.3390/membranes15080244 - 10 Aug 2025

Abstract

Produced water, a byproduct of oil and gas extraction, poses significant environmental challenges due to its complex composition and high salinity. Conventional treatment technologies often struggle to achieve efficient contaminant removal while maintaining long-term operational stability. Membrane-based separation processes, particularly forward osmosis (FO), [...] Read more.

Produced water, a byproduct of oil and gas extraction, poses significant environmental challenges due to its complex composition and high salinity. Conventional treatment technologies often struggle to achieve efficient contaminant removal while maintaining long-term operational stability. Membrane-based separation processes, particularly forward osmosis (FO), offer a promising alternative due to their low hydraulic pressure requirements, high selectivity, and ability to mitigate fouling and scaling effects. This study fabricated and evaluated a novel dual-layer zwitterion-modified electrospun nanofibrous membrane for enhanced produced water (PW) treatment. The dual-layer design consists of a highly porous electrospun nanofibrous support layer for improved permeability and mechanical strength, coupled with a zwitterionic-modified selective layer to enhance antifouling properties and selective contaminant rejection. The zwitterionic surface modification imparts superior hydration capacity, reducing organic and biological fouling while improving water transport efficiency. The membranes are characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD), contact angle and tensile strength measurements, and nuclear magnetic resonance (NMR) spectroscopy to assess their morphological, structural, and chemical properties. The performance evaluations demonstrated significantly higher water flux (up to 16.05 L m⁻² h⁻¹ for SPW (synthetic produced water) and 6.00 L m⁻² h⁻¹ for PW using NaBr) and excellent solid rejection (up to 96.02% for SPW and 88.90% for PW), reduced concentration polarization, and superior antifouling performance compared to conventional FO membranes. Experimental results from bench-scale trials demonstrate that this advanced membrane technology offers enhanced water recovery and contaminant removal efficiency, making it a viable solution for industrial-scale PW treatment and reuse. The findings underscore the potential of next-generation dual-layer FO membranes in promoting sustainable water resource management within the oil and gas sector while minimizing environmental impact. Full article

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

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23 pages, 2957 KiB

Open AccessArticle

Comparing Constant and Transient Membrane Transport Parameters for Use in Wave Desalination Models

by Kurban A. Sitterley, Zachary Binger and Dale Scott Jenne

Membranes 2025, 15(8), 243; https://doi.org/10.3390/membranes15080243 - 9 Aug 2025

Abstract

Directly pressurizing seawater for desalination with reverse osmosis membranes via wave motion is a promising and sustainable method for producing freshwater in coastal regions. However, such a system could result in significant pressure fluctuations and a departure from conventional steady-state desalination operations. This [...] Read more.

Directly pressurizing seawater for desalination with reverse osmosis membranes via wave motion is a promising and sustainable method for producing freshwater in coastal regions. However, such a system could result in significant pressure fluctuations and a departure from conventional steady-state desalination operations. This study sought to assess if membrane transport parameters (apparent water and salt permeability) should be modeled as transient or constant in solution–diffusion-based modeling efforts of dynamically operated desalination systems, such as those coupled to wave power. Two approaches were used to model membrane transport parameters: one considered each parameter to be a function of the net driving pressure of the system, and the other assumed they were constant across all conditions. A pilot-scale system was used to conduct steady-state and controlled ramping experiments. Data from steady-state experiments were used to calculate transient and constant transport parameters. Parameter combinations were used in a simulation model to predict water flux and effective permeate salinity, and simulation outcomes were compared against experimental ramping results. The transient relationships for both water and salt permeability produced the most accurate results for water flux and comparable results for effective permeate salinity. Development of such relationships would be unique to a specific system but could be valuable in modeling wave-driven desalination systems across the wide range of operating conditions they experience. Full article

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

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22 pages, 2004 KiB

Open AccessArticle

Environmental Sustainability Assessment of a Filtration–Diafiltration Strategy for Recovering Savory Compounds from Mussel Cooking Water

by Erasmo Cadena, Jo Dewulf, David San Martin, Jone Ibarruri, Bruno Iñarra and Monica Gutierrez

Membranes 2025, 15(8), 242; https://doi.org/10.3390/membranes15080242 - 8 Aug 2025

Abstract

Global seafood production and consumption have increased in recent years, leading to a significant rise in side streams. Process waters are often disposed as wastewater, causing difficulties for industries in meeting the discharge standards. This is particularly relevant to the mussel processing industry, [...] Read more.

Global seafood production and consumption have increased in recent years, leading to a significant rise in side streams. Process waters are often disposed as wastewater, causing difficulties for industries in meeting the discharge standards. This is particularly relevant to the mussel processing industry, where one-third of the raw material ends up as high-organic content effluent. This study aims to optimize a nanofiltration–diafiltration (NF–DF) strategy to recover valuable savory compounds from mussel cooking water, to reduce the effluent organic pollution, and to evaluate its environmental sustainability using Life Cycle Assessment. Pilot trials lead to a configuration, combining a volumetric concentration factor of 10 in NF and 20 in DF, which achieved enhanced protein concentration (1.5-fold), amino acid concentration (5.2-fold), and COD removal (98.2%). The environmental assessment highlighted electricity consumption during NF and DF as the primary environmental hotspot, resulting in a carbon footprint of 0.12 kg CO₂ eq. kg⁻¹ of savory compounds and water use of 0.65 m³ deprived kg⁻¹. Prospective scenarios projected that ongoing energy system transitions could significantly reduce climate change and acidification impacts by over 75% by 2050. The proposed NF–DF strategy enhances resource efficiency and sustainability in seafood processing by recovering high-value compounds and facilitating water reuse. Full article

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

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20 pages, 2833 KiB

Open AccessReview

Separation Principles and Strategies for an Oil–Water Separation Membrane with Special Wettability

by Xiaoying Hu, Tong Xing, Huiyu Wu, Kunyu Wei, Mamadou Souare and Changqing Dong

Membranes 2025, 15(8), 241; https://doi.org/10.3390/membranes15080241 - 8 Aug 2025

Abstract

Although numerous reviews have discussed the research progress in “filtration-type” oil–water membrane separation with special wettability, they predominantly focus on the types of membrane separation and preparation methods, without providing an in-depth analysis of the separation principles and strategies. This paper is different [...] Read more.

Although numerous reviews have discussed the research progress in “filtration-type” oil–water membrane separation with special wettability, they predominantly focus on the types of membrane separation and preparation methods, without providing an in-depth analysis of the separation principles and strategies. This paper is different from the previous reviews focusing on the types and preparation methods of membrane separation, mainly as regards membrane surface adsorption, liquid through the pores, and liquid extraction from the pores of the three key nodes in order to analyze the impact of membrane block wettability on the oil–water separation effect of the independent influence. Accordingly, we summed up the membrane separation principle and design strategy to guide modular wettability design during membrane fabrication, thereby enhancing membrane wettability. The modular wettability design approach can provide guidance during the membrane development phase, offering potential solutions to extend membrane lifespan and address issues of surface fouling and pore clogging while enhancing mass transfer efficiency during operation. Full article

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

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33 pages, 8038 KiB

Open AccessArticle

Antifouling and Desalination Enhancement of Forward Osmosis-Based Thin Film Composite Membranes via Functionalized Multiwalled Carbon Nanotubes Mixed Matrix Polyethersulfone Substrate

by Hamza E. Almansouri, Mohamed Edokali, Mazrul N. Abu Seman, Ellora Priscille Ndia Ntone, Che Ku Mohammad Faizal Che Ku Yahya and Abdul Wahab Mohammad

Membranes 2025, 15(8), 240; https://doi.org/10.3390/membranes15080240 - 8 Aug 2025

Abstract

The growing scarcity of freshwater worldwide has increased interest in forward osmosis (FO) membranes as a promising solution for water desalination and wastewater treatment. This study investigates the enhancement of thin-film composite (TFC) FO membranes via the incorporation of carboxyl-functionalized multiwalled carbon nanotubes [...] Read more.

The growing scarcity of freshwater worldwide has increased interest in forward osmosis (FO) membranes as a promising solution for water desalination and wastewater treatment. This study investigates the enhancement of thin-film composite (TFC) FO membranes via the incorporation of carboxyl-functionalized multiwalled carbon nanotubes (COOH-MWCNTs) into the polyethersulfone (PES) support layer. The membranes were fabricated using a combination of phase inversion and interfacial polymerization techniques, with COOH-MWCNTs incorporated into the membrane support layers at different concentrations (0–0.75 wt.%). Comprehensive characterization was carried out using various analytical methods and mechanical testing to evaluate the physicochemical and structural properties of the membranes. The modified membranes demonstrated improved hydrophilicity, enhanced mechanical and thermal stability, and improved surface charge properties. Performance tests using a 1 M NaCl draw solution showed that the optimized membrane (0.5 wt.% COOH-MWCNTs) attained a 161% enhancement in water flux (7.48 LMH) compared to the unmodified membrane (2.86 LMH), while also reducing internal concentration polarization (ICP). The antifouling properties were also significantly improved, with a flux recovery rate of 91.92%, attributed to enhanced electrostatic repulsion as well as surface and microstructural modifications. Despite a moderate rise in reverse solute flux, the specific reverse solute flux (J_s/J_w) remained within acceptable limits. These findings highlight the potential of COOH-MWCNT-modified membranes in enhancing FO desalination performance, offering a promising option for next-generation water purification technologies. Full article

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

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20 pages, 2614 KiB

Open AccessArticle

Porphyrin-Modified Polyethersulfone Ultrafiltration Membranes for Enhanced Bacterial Inactivation and Filtration Performance

by Funeka Matebese, Nonkululeko Malomane, Meladi L. Motloutsi, Richard M. Moutloali and Muthumuni Managa

Membranes 2025, 15(8), 239; https://doi.org/10.3390/membranes15080239 - 6 Aug 2025

Abstract

Municipal wastewaters pose a severe risk to the environment and human health when discharged untreated. This is due to their high content of pathogens, such as viruses and bacteria, which can cause diseases like cholera. Herein, the research and development of porphyrin-modified polyethersulfone [...] Read more.

Municipal wastewaters pose a severe risk to the environment and human health when discharged untreated. This is due to their high content of pathogens, such as viruses and bacteria, which can cause diseases like cholera. Herein, the research and development of porphyrin-modified polyethersulfone (PES) ultrafiltration (UF) membranes was conducted to improve bacterial inactivation in complex municipal wastewater and enhance the fouling resistance and filtration performance. The synthesis and fabrication of porphyrin nanofillers and the resultant membrane characteristics were studied. The incorporation of porphyrin-based nanofillers improved the membrane’s hydrophilicity, morphology, and flux (247 Lm⁻² h⁻¹), with the membrane contact angle (CA) decreasing from 90° to ranging between 58° and 50°. The membrane performance was monitored for its flux, antifouling properties, reusability potential, municipal wastewater, and humic acid. The modified membranes demonstrated an effective application in wastewater treatment, achieving notable antibacterial activity, particularly under light exposure. The In-BP@SW/PES membrane demonstrated effective antimicrobial photodynamic effects against both Gram-positive S. aureus and Gram-negative E. coli. It achieved at least a 3-log reduction in bacterial viability, meeting Food and Drug Administration (FDA) standards for efficient antimicrobial materials. Among the variants tested, membranes modified with In-PB@SW nanofillers exhibited superior antifouling properties with flux recovery ratios (FRRs) of 78.9% for the humic acid (HA) solution and 85% for the municipal wastewater (MWW), suggesting a strong potential for long-term filtration use. These results highlight the promise of porphyrin-functionalized membranes as multifunctional tools in advanced water treatment technologies. Full article

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

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24 pages, 2930 KiB

Open AccessArticle

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

Abstract

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

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

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

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15 pages, 2632 KiB

Open AccessArticle

Treatment of Dairy Wastewater Retentate After Microfiltration: Evaluation of the Performance of the System Based on Activated Sludge and Activated Carbon

by Maciej Życki, Wioletta Barszcz and Monika Łożyńska

Membranes 2025, 15(8), 237; https://doi.org/10.3390/membranes15080237 - 6 Aug 2025

Abstract

The dairy industry generates significant amounts of wastewater, including microfiltration (MF) retentate, a byproduct thickened with organic and inorganic pollutants. This study focuses on the treatment of two times concentrated MF retentate using a hybrid system based on biological treatment in a sequential [...] Read more.

The dairy industry generates significant amounts of wastewater, including microfiltration (MF) retentate, a byproduct thickened with organic and inorganic pollutants. This study focuses on the treatment of two times concentrated MF retentate using a hybrid system based on biological treatment in a sequential batch reactor (SBR) and adsorption on activated carbon. The first stage involved cross-flow microfiltration using a 0.2 µm PVDF membrane at 0.5 bar, resulting in reductions of 99% in turbidity and 79% in chemical oxygen demand (COD), as well as a partial reduction in conductivity. The second stage involved 24-h biological treatment in a sequential batch reactor (SBR) with activated sludge (activated sludge index: 80 cm³/g, MLSS 2500 mg/dm³), resulting in further reductions in COD (62%) and TOC (30%), as well as the removal of 46% of total phosphorus (TP) and 35% of total nitrogen (TN). In the third stage, the decantate underwent adsorption in a column containing powdered activated carbon (PAC; 1 g; S_(BET) = 969 m² g⁻¹), reducing the concentrations of key indicators to the following levels: COD 84%, TOC 70%, TN 77%, TP 87% and suspended solids 97%. Total pollutant retention ranged from 24.6% to 97.0%. These results confirm that the MF–SBR–PAC system is an effective, compact solution that significantly reduces the load of organic and biogenic pollutants in MF retentates, paving the way for their reuse or safe discharge into the environment. Full article

(This article belongs to the Special Issue Towards the Circular Economy—Membrane Processes for the Recovery of Water and Nutrients from Wastewater (2nd Edition))

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38 pages, 9212 KiB

Open AccessReview

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

Abstract

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

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

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

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22 pages, 5293 KiB

Open AccessArticle

Membrane Distillation for Water Desalination: Assessing the Influence of Operating Conditions on the Performance of Serial and Parallel Connection Configurations

by Lebea N. Nthunya and Bhekie B. Mamba

Membranes 2025, 15(8), 235; https://doi.org/10.3390/membranes15080235 - 4 Aug 2025

Abstract

Though the pursuit of sustainable desalination processes with high water recovery has intensified the research interest in membrane distillation (MD), the influence of module connection configuration on performance stability remains poorly explored. The current study provided a comprehensive multiparameter assessment of hollow fibre [...] Read more.

Though the pursuit of sustainable desalination processes with high water recovery has intensified the research interest in membrane distillation (MD), the influence of module connection configuration on performance stability remains poorly explored. The current study provided a comprehensive multiparameter assessment of hollow fibre membrane modules connected in parallel and series in direct contact membrane distillation (DCMD) for the first time. The configurations were evaluated under varying process parameters such as temperature (50–70 °C), flow rates (22.1–32.3 mL·s⁻¹), magnesium concentration as scalant (1.0–4.0 g·L⁻¹), and flow direction (co-current and counter-current), assessing their influence on temperature gradients (∆T), flux and pH stability, salt rejection, and crystallisation. Interestingly, the parallel module configuration maintained high operational stability with uniform flux and temperature differences (∆T) even at high recovery factors (>75%). On one hand, the serial configuration experienced fluctuating ∆T caused by thermal and concentration polarisation, causing an early crystallisation (abrupt drop in feed conductivity). Intensified polarisation effects with accelerated crystallisation increased the membrane risk of wetting, particularly at high recovery factors. Despite these changes, the salt rejection remained relatively high (99.9%) for both configurations across all tested conditions. The findings revealed that acidification trends caused by MgSO₄ were configuration-dependent, where the parallel setup-controlled rate of pH collapse. This study presented a novel framework connecting membrane module architecture to mass and heat transfer phenomena, providing a transformative DCMD module configuration design in water desalination. These findings not only provide the critical knowledge gaps in DCMD module configurations but also inform optimisation of MD water desalination to achieve high recovery and stable operation conditions under realistic brine composition. Full article

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

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13 pages, 2939 KiB

Open AccessReview

A Review of Maricultural Wastewater Treatment Using an MBR: Insights into the Mechanism of Membrane Fouling Mitigation Through a Microalgal–Bacterial Symbiotic and Microbial Ecological Network

by Yijun You, Shuyu Zhao, Binghan Xie, Zhipeng Li, Weijia Gong, Guoyu Zhang, Qinghao Li, Xiangqian Zhao, Zhaofeng Xin, Jinkang Wu, Yuanyuan Gao and Han Xiang

Membranes 2025, 15(8), 234; https://doi.org/10.3390/membranes15080234 - 1 Aug 2025

Abstract

Membrane bioreactors (MBRs) have been utilized for maricultural wastewater treatment, where high-salinity stress results in dramatic membrane fouling in the actual process. A microalgal–bacterial symbiotic system (MBSS) offers advantages for photosynthetic oxygen production, dynamically regulating the structure of extracellular polymeric substances (EPSs) and [...] Read more.

Membrane bioreactors (MBRs) have been utilized for maricultural wastewater treatment, where high-salinity stress results in dramatic membrane fouling in the actual process. A microalgal–bacterial symbiotic system (MBSS) offers advantages for photosynthetic oxygen production, dynamically regulating the structure of extracellular polymeric substances (EPSs) and improving the salinity tolerance of bacteria and algae. This study centered on the mechanisms of membrane fouling mitigation via the microalgal–bacterial interactions in the MBSS, including improving the pollutant removal, optimizing the system parameters, and controlling the gel layer formation. Moreover, the contribution of electrochemistry to decreasing the inhibitory effects of high-salinity stress was investigated in the MBSS. Furthermore, patterns of shifts in microbial communities and the impacts have been explored using metagenomic technology. Finally, this review aims to offer new insights for membrane fouling mitigation in actual maricultural wastewater treatment. Full article

(This article belongs to the Special Issue Emerging Superwetting Membranes: New Advances in Water Treatment)

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12 pages, 3890 KiB

Open AccessArticle

Visualization of Film Formation Process of Copolyesteramide Containing Phthalazine Moieties During Interfacial Polymerization

by Zeyuan Liu, Hailong Li, Qian Liu, Zhaoqi Wang, Danhui Wang, Peiqi Xu, Xigao Jian and Shouhai Zhang

Membranes 2025, 15(8), 233; https://doi.org/10.3390/membranes15080233 - 1 Aug 2025

Abstract

Interfacial polymerization (IP) has been widely utilized to synthesize composite membranes. However, precise control of this reaction remains a challenge due to the complexity of the IP process. Herein, an optical three-dimensional microscope was used to directly observe the IP process. To construct [...] Read more.

Interfacial polymerization (IP) has been widely utilized to synthesize composite membranes. However, precise control of this reaction remains a challenge due to the complexity of the IP process. Herein, an optical three-dimensional microscope was used to directly observe the IP process. To construct copolyesteramide containing phthalazine moiety films, rigid monomer 4-(4′-hydroxyphenyl)-2,3-phthalazin-1-one (DHPZ) and flexible monomer piperazine (PIP) were used as aqueous phase monomers, and trimesoyl chloride (TMC) served as the organic phase monomer. Multilayer cellular structures were observed for the copolyesteramide films during the IP process. The effects of multiple factors including the ratio between flexible and rigid monomers, co-solvents, and the addition of phase transfer catalysts on the film growth and the morphologies were investigated. This research aims to deepen our understanding of the IP process, especially for the principles which govern polymer film growth and morphology, to promote new methodologies for regulating interfacial polymerization in composite membrane preparation. Full article

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

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15 pages, 4578 KiB

Open AccessArticle

Improving Balance Between Oxygen Permeability and Stability of Ba_0.5Sr_0.5Co_0.8Fe_0.2O₃₋_δ Through High-Entropy Design

by Yongfan Zhu, Meng Wu, Guangru Zhang, Zhengkun Liu and Gongping Liu

Membranes 2025, 15(8), 232; https://doi.org/10.3390/membranes15080232 - 1 Aug 2025

Abstract

Currently, the trade-off between oxygen permeation flux and structural stability in conventional perovskite oxides restricts the practical application of oxygen permeable membranes. In this study, a high-entropy design was applied to the B-site of BSCF matrix materials, resulting in the successful synthesis of [...] Read more.

Currently, the trade-off between oxygen permeation flux and structural stability in conventional perovskite oxides restricts the practical application of oxygen permeable membranes. In this study, a high-entropy design was applied to the B-site of BSCF matrix materials, resulting in the successful synthesis of a high-entropy perovskite, Ba_0.5Sr_0.5Co_0.71Fe_0.2Ta_0.03Ni_0.03Zr_0.03O_3−δ. The crystal structure, microstructure, and elemental composition of the material were systematically characterized and analyzed. Theoretical analysis and experimental characterization confirm that the material exhibits a stable single-phase high-entropy perovskite oxide structure. Under He as the sweep gas, the membrane achieved an oxygen permeation flux of 1.28 mL·cm⁻²·min⁻¹ and operated stably for over 100 h (1 mm thick, 900 °C). In a 20% CO₂/He atmosphere, the flux remained above 0.92 mL·cm⁻²·min⁻¹ for over 100 h, demonstrating good CO₂ tolerance. Notably, when the sweep gas is returned to the pure He atmosphere, the oxygen permeation flux fully recovers to 1.28 mL·cm⁻²·min⁻¹, with no evidence of leakage. These findings indicate that the proposed B-site doping strategy can break the trade-off between oxygen permeability and structural stability in conventional perovskite membranes. This advancement supports the industrialization of oxygen permeable membranes and offers valuable theoretical guidance for the design of high-performance perovskite materials. Full article

(This article belongs to the Special Issue Membrane Separation and Water Treatment: Modeling and Application, 2nd Edition)

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15 pages, 2424 KiB

Open AccessArticle

Cyanuric Chloride with the s-Triazine Ring Fabricated by Interfacial Polymerization for Acid-Resistant Nanofiltration

by Zhuangzhuang Tian, Yun Yin, Jiandong Wang, Xiuling Ao, Daijun Liu, Yang Jin, Jun Li and Jianjun Chen

Membranes 2025, 15(8), 231; https://doi.org/10.3390/membranes15080231 - 1 Aug 2025

Abstract

Nanofiltration (NF) is considered a competitive purification method for acidic stream treatments. However, conventional thin-film composite NF membranes degrade under acid exposures, limiting their applications in industrial acid treatment. For example, wet-process phosphoric acid contains impurities of multivalent metal ions, but NF membrane [...] Read more.

Nanofiltration (NF) is considered a competitive purification method for acidic stream treatments. However, conventional thin-film composite NF membranes degrade under acid exposures, limiting their applications in industrial acid treatment. For example, wet-process phosphoric acid contains impurities of multivalent metal ions, but NF membrane technologies for impurity removal under harsh conditions are still immature. In this work, we develop a novel strategy of acid-resistant nanofiltration membranes based on interfacial polymerization (IP) of polyethyleneimine (PEI) and cyanuric chloride (CC) with the s-triazine ring. The IP process was optimized by orthogonal experiments to obtain positively charged PEI-CC membranes with a molecular weight cut-off (MWCO) of 337 Da. We further applied it to the approximate industrial phosphoric acid purification condition. In the tests using a mixed solution containing 20 wt% P₂O₅, 2 g/L Fe³⁺, 2 g/L Al³⁺, and 2 g/L Mg²⁺ at 0.7 MPa and 25 °C, the NF membrane achieved 56% rejection of Fe, Al, and Mg and over 97% permeation of phosphorus. In addition, the PEI-CC membrane exhibited excellent acid resistance in the 48 h dynamic acid permeation experiment. The simple fabrication procedure of PEI-CC membrane has excellent acid resistance and great potential for industrial applications. Full article

(This article belongs to the Special Issue Nanofiltration Membranes for Precise Separation)

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18 pages, 2393 KiB

Open AccessArticle

Phosphate Transport Through Homogeneous and Heterogeneous Anion-Exchange Membranes: A Chronopotentiometric Study for Electrodialytic Applications

by Kayo Santana-Barros, Manuel César Martí-Calatayud, Svetlozar Velizarov and Valentín Pérez-Herranz

Membranes 2025, 15(8), 230; https://doi.org/10.3390/membranes15080230 - 31 Jul 2025

Abstract

This study investigates the behavior of phosphate ion transport through two structurally distinct anion-exchange membranes—AMV (homogeneous) and HC-A (heterogeneous)—in an electrodialysis system under both static and stirred conditions at varying pH levels. Chronopotentiometric and current–voltage analyses were used to investigate the influence of [...] Read more.

This study investigates the behavior of phosphate ion transport through two structurally distinct anion-exchange membranes—AMV (homogeneous) and HC-A (heterogeneous)—in an electrodialysis system under both static and stirred conditions at varying pH levels. Chronopotentiometric and current–voltage analyses were used to investigate the influence of pH and hydrodynamics on ion transport. Under underlimiting (ohmic) conditions, the AMV membrane exhibited simultaneous transport of H₂PO₄⁻ and HPO₄²⁻ ions at neutral and mildly alkaline pH, while such behavior was not verified at acidic pH and in all cases for the HC-A membrane. Under overlimiting current conditions, AMV favored electroconvection at low pH and exhibited significant water dissociation at high pH, leading to local pH shifts and chemical equilibrium displacement at the membrane–solution interface. In contrast, the HC-A membrane operated predominantly under strong electroconvective regimes, regardless of the pH value, without evidence of water dissociation or equilibrium change phenomena. Stirring significantly impacted the electrochemical responses: it altered the chronopotentiogram profiles through the emergence of intense oscillations in membrane potential drop at overlimiting currents and modified the current–voltage behavior by increasing the limiting current density, reducing electrical resistance, and compressing the plateau region that separates ohmic and overlimiting regimes. Additionally, both membranes showed signs of NH₃ formation at the anodic-side interface under pH 7–8, associated with increased electrical resistance. These findings reveal distinct ionic transport characteristics and hydrodynamic sensitivities of the membranes, thus providing valuable insights for optimizing phosphate recovery via electrodialysis. Full article

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

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