Membranes

50 pages, 5008 KiB

Open AccessArticle

X-Ray Crystal and Cryo-Electron Microscopy Structure Analysis Unravels How the Unique Thylakoid Lipid Composition Is Utilized by Cytochrome b₆f for Driving Reversible Proteins’ Reorganization During State Transitions

by Radka Vladkova

Membranes 2025, 15(5), 143; https://doi.org/10.3390/membranes15050143 - 8 May 2025

Abstract

The rapid regulatory mechanism of light-induced state transitions (STs) in oxygenic photosynthesis is particularly appealing for membrane-based applications. This interest stems from the unique ability of the thylakoid membrane protein cytochrome b₆f (cytb₆f) to increase or decrease [...] Read more.

The rapid regulatory mechanism of light-induced state transitions (STs) in oxygenic photosynthesis is particularly appealing for membrane-based applications. This interest stems from the unique ability of the thylakoid membrane protein cytochrome b₆f (cytb₆f) to increase or decrease its hydrophobic thickness (d_P) in parallel with the reduction or oxidation of the PQ pool induced by changes in light quality. This property appears to be the long-sought biophysical driver behind the reorganizations of membrane proteins during STs. This study decisively advances the hydrophobic mismatch (HMM) model for cytb₆f-driven STs -by thoroughly analyzing thirteen X-ray crystal and eight cryo-electron microscopy cytb₆f structures. It uncovers the lipid nanoenvironments that cytb₆f, with different hydrophobic thicknesses, selectively attracts. Under optimal, stationary conditions for photosynthesis in low light, when there is hydrophobic matching between the hydrophobic thicknesses of cytb₆f d_P and that of the bulk thylakoid lipid phase d_L, d_P = d_L, cytb₆f predominantly binds to anionic lipids—several phosphatidylglycerol (PG) molecules and one sulfoquinovosyldiacylglycerol (SQDG) molecule. Upon the induction of the transition to State 2, when d_P increases and induces a positive HMM (d_P > d_L), the neutral, non-bilayer-forming lipid monogalactosyldiacylglycerol (MGDG) replaces some of the bound PGs. Upon the induction of the transition to State 1, when d_P decreases and induces a negative HMM (d_P < d_L), PGs and SQDG detach from their binding sites, and two neutral, bilayer-forming lipids such as digalactosyldiacylglycerol (DGDG) occupy two sites. Additionally, this research uncovers two lipid-mediated signaling pathways from Chla to the center of flexibility, the Phe/Tyr124^fg^-loop-suIV residue—one of which involves β-carotene. This study identifies two novel types of lipid raft-like nanodomains that are devoid of typical components, such as sphingomyelin and cholesterol. These findings firmly validate the HMM model and underscore the STs as the first recognized functional process that fully utilizes the unique and evolutionarily conserved composition of just four thylakoid lipid classes. This research contributes to our understanding of membrane dynamics in general and STs in particular. It introduces a novel and simple approach for reversible protein reorganization driven purely by biophysical mechanisms, with promising implications for various membrane-based applications. Full article

(This article belongs to the Special Issue Biological Membrane Dynamics and Reorganization Induced by Light Changes)

15 pages, 4044 KiB

Open AccessArticle

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

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

20 pages, 4427 KiB

Open AccessArticle

Separation and Characterization of Heterogeneity Among Various Sizes of Outer Membrane Vesicles Derived from the Probiotic Escherichia coli Nissle 1917

by Ning Li, Hongbo Xin and Keyu Deng

Membranes 2025, 15(5), 141; https://doi.org/10.3390/membranes15050141 - 5 May 2025

Abstract

Outer membrane vesicles (OMVs) are extracellular vesicles secreted by Gram-negative bacteria with diameters of 20–250 nm. OMVs contain various biologically active substances from their parent bacteria, such as proteins, lipids, and nucleic acids. Escherichia coli Nissle 1917 (EcN) is a Gram-negative probiotic that [...] Read more.

Outer membrane vesicles (OMVs) are extracellular vesicles secreted by Gram-negative bacteria with diameters of 20–250 nm. OMVs contain various biologically active substances from their parent bacteria, such as proteins, lipids, and nucleic acids. Escherichia coli Nissle 1917 (EcN) is a Gram-negative probiotic that resides in the human intestine. EcN-derived OMVs are pivotal in modulating intestinal immune responses. However, few studies have addressed the heterogeneity of EcN-derived OMVs in terms of size, significantly limiting the research on their clinical applications. Currently, there are a lack of feasible methods for obtaining EcN-derived OMVs of different sizes. To address this knowledge gap, we developed a membrane filtration method to isolate EcN-derived OMVs of varying sizes. In this study, we first used gradient filtration to isolate high-purity EcN-derived OMVs and conducted a proteomic analysis. Subsequently, we used membrane filtration to separate the EcN-derived OMVs by size. We successfully obtained EcN-derived OMVs of three specific sizes: <50 nm, 50–100 nm, and 100–300 nm. We then performed proteomic analyses of these EcN-derived OMVs and compared their protein profiles. Finally, we compared the ability of each EcN-derived OMV type to induce RAW264.7 macrophages to secrete the pro-inflammatory factor interleukin (IL)-1β and the anti-inflammatory factor IL-10. The EcN-derived OMVs contained 646 different proteins overall; those of different sizes contained different protein types. Among them, the EcN-derived OMVs in the <50 nm group contained significantly fewer proteins (262 different types in total) than those in the 50–100 nm (1603 types) and 100–300 nm (1568 types) groups. Furthermore, the <50 nm group had fewer membrane proteins (40) than the 50–100 nm (215) and 100–300 nm (209) groups. We also found that RAW264.7 macrophages secreted different concentrations of IL-1β and IL-10 following co-incubation with the three EcN-derived OMV types. The 50–100 nm EcN-derived OMV group showed a stronger effect in terms of inducing inflammatory cytokine secretion compared to the other two groups. This study provides direct experimental evidence that EcN-derived OMVs of different sizes exhibit heterogeneous properties. Full article

(This article belongs to the Special Issue Application of Membrane Materials in Bioseparation and Downstream Processing)

► Show Figures

Figure 1

16 pages, 546 KiB

Open AccessReview

Applications of Reverse Osmosis and Nanofiltration Membrane Process in Wine and Beer Industry

by Yogesh Kumar, Atul Khalangre, Rajat Suhag and Alfredo Cassano

Membranes 2025, 15(5), 140; https://doi.org/10.3390/membranes15050140 - 2 May 2025

Abstract

Reverse osmosis (RO) and nanofiltration (NF) membranes are traditionally employed in wine and beer production for concentration, clarification, and stabilization. Their applications now extend to dealcoholization, addressing rising demand for low-alcohol beverages. RO/NF selectively reduce ethanol while retaining volatile aromas and non-volatile flavors, [...] Read more.

Reverse osmosis (RO) and nanofiltration (NF) membranes are traditionally employed in wine and beer production for concentration, clarification, and stabilization. Their applications now extend to dealcoholization, addressing rising demand for low-alcohol beverages. RO/NF selectively reduce ethanol while retaining volatile aromas and non-volatile flavors, outperforming thermal methods that degrade sensory profiles. This review examines RO/NF roles in alcohol adjustment, sugar modification, and by-product recovery, emphasizing mechanisms and efficiency. Operational challenges such as membrane fouling (polysaccharides, polyphenols), selectivity–permeation flux trade-offs, and energy costs are assessed. By balancing tradition with innovation, RO/NF technologies offer transformative potential for meeting health and sustainability goals in beverage industries. However, gaps in standardization, sensory consistency, and cost-effectiveness necessitate targeted research to optimize industrial adoption and consumer acceptance. Full article

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

► Show Figures

Figure 1

14 pages, 1767 KiB

Open AccessArticle

Toluidine Blue for the Determination of Binding of Anionic Polysaccharides to Lipid Raft Domains by Absorption Spectroscopy

by Sandra Gębczyńska, Julia Gdowska, Agata Mikos, Iga Gawrońska, Teresa Janas, Aleksander Czogalla and Tadeusz Janas

Membranes 2025, 15(5), 139; https://doi.org/10.3390/membranes15050139 - 2 May 2025

Abstract

The complexes of negatively charged polysaccharides with lipid vesicles have been shown to have applications in medicine, bioremediation, water purification, and construction of nano-biosensors. This article presents research on the formation of these complexes based on the interactions between three types of liposomes, [...] Read more.

The complexes of negatively charged polysaccharides with lipid vesicles have been shown to have applications in medicine, bioremediation, water purification, and construction of nano-biosensors. This article presents research on the formation of these complexes based on the interactions between three types of liposomes, DOPC liposomes (which contain a lipid bilayer in the liquid-disordered (Ld) state), RAFT liposomes (which contain liquid-ordered (Lo) lipid raft domains surrounded by lipids in the Ld state) and SPH–CHL liposomes (which contain a lipid bilayer in the Lo state), and two selected anionic polysaccharides, polysialic acid (PSA) and polygalacturonic acid (PGA). The analysis was conducted using a toluidine blue (TB) probe and the absorption spectroscopy technique. In contrast to DOPC and SPH–CHL liposomes, binding of negatively charged PSA or PGA chains to RAFT liposomes induced a TB absorption maximum shift from 630 nm to 560 nm. The obtained results indicate that toluidine blue can be applied for monitoring the formation of these nano-complexes, and that the boundaries between Ld/Lo domains within membranes in RAFT liposomes can significantly enhance the binding affinity of negatively charged polysaccharides to the lipid bilayer surface. The observed metachromatic shift in TB absorption suggests that negatively charged PSA and PGA chains interact with the Ld/Lo boundaries within RAFT liposome membranes. Full article

(This article belongs to the Section Biological Membranes)

► Show Figures

Graphical abstract

29 pages, 3853 KiB

Open AccessReview

Membrane Technology for Valuable Resource Recovery from Palm Oil Mill Effluent (POME): A Review

by Que Nguyen Ho, Woei Jye Lau, Juhana Jaafar, Mohd Hafiz Dzarfan Othman and Naoko Yoshida

Membranes 2025, 15(5), 138; https://doi.org/10.3390/membranes15050138 - 2 May 2025

Abstract

Palm oil mill effluent (POME), a byproduct of palm oil processing, has substantial resource recovery potential. Its rich biodegradable content supports methane (CH₄) production via anaerobic digestion, enabling renewable energy generation. Additionally, the significant water content of POME can be reclaimed [...] Read more.

Palm oil mill effluent (POME), a byproduct of palm oil processing, has substantial resource recovery potential. Its rich biodegradable content supports methane (CH₄) production via anaerobic digestion, enabling renewable energy generation. Additionally, the significant water content of POME can be reclaimed for use in boiler feed, irrigation, and drinking water. However, selecting appropriate technologies to recover valuable resources from POME is challenging, particularly for the purification and upgrading of biogas. Membrane technologies offer an effective approach for transforming POME treatment from an energy-intensive process into a resource recovery system, supporting the decarbonization of palm oil production and advancing global sustainability objectives. This technique is cost-effective and ecofriendly for biogas purification and water reclamation. For biogas purification and upgrading, membrane systems offer the lowest capital and operational costs at 5.654 USD/m³, compared to other technologies, such as 6.249 USD/m³ for water scrubbers and 6.999 USD/m³ for chemical absorbers. This review primarily explores the potential of membranes for gas purification from POME and examines their integration with other processes to develop advanced systems, such as ultrasonicated membrane anaerobic systems and membrane anaerobic systems, to enhance biogas production. In addition, water reclamation from POME is discussed, with ultrafiltration membranes emerging as the most promising candidates. Proton exchange membranes, such as Nafion, are used extensively in microbial fuel cells to improve electricity generation, and this is also summarized. Finally, challenges and future perspectives are highlighted, emphasizing the broader potential of membrane technology in POME wastewater resource recovery. Full article

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

► Show Figures

Figure 1

14 pages, 4249 KiB

Open AccessArticle

Effect of Microfiltration Membrane Configuration in Microplastics Recovery from Wastewater Treatment Effluent

by Rubén Rodríguez-Alegre, Sergi Durán-Videra, Laura Pérez Megías, Montserrat Pérez-Moya, Julia García-Montaño, Carlos Andecochea Saiz and Xialei You

Membranes 2025, 15(5), 137; https://doi.org/10.3390/membranes15050137 (registering DOI) - 2 May 2025

Abstract

Water scarcity has driven the use of wastewater treatment plant (WWTP) effluents as reclaimed water, highlighting the need to overcome challenges such as the presence of emerging contaminants, particularly microplastics (MPs), which WWTPs are unable to effectively remove. Membrane-based processes, such as microfiltration, [...] Read more.

Water scarcity has driven the use of wastewater treatment plant (WWTP) effluents as reclaimed water, highlighting the need to overcome challenges such as the presence of emerging contaminants, particularly microplastics (MPs), which WWTPs are unable to effectively remove. Membrane-based processes, such as microfiltration, have demonstrated high efficiency in the removal of suspended solids, and their application for MP removal is currently under investigation. This study assesses the influence of microfiltration membrane spacer size (1 mil and 80 mil) and geometry—diamond and corrugated—on MP recovery performance, using synthetic wastewaters with varying MPs concentrations. The results indicate the superior performance of large corrugated and small diamond-shaped membranes, as both exhibited the highest and comparable permeate flux, with no MP retention within the membrane element. All microfiltration membranes achieved an 80% recovery of the influent as safe reclaimed water and demonstrated an MP recovery efficiency exceeding 99%, with 100% rejection for fragments and up to 98% rejection for fibres. Full article

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

► Show Figures

Figure 1

12 pages, 3895 KiB

Open AccessArticle

Electrodialysis Metathesis for the Production of Potassium Phosphate

by Shichang Xu, Zhen Zhang, Long Zhang, Lixin Xie and Wen Zhang

Membranes 2025, 15(5), 136; https://doi.org/10.3390/membranes15050136 - 1 May 2025

Abstract

Potassium phosphate (K₃PO₄) is a common inorganic compound with broad applications in agriculture and industry. Although the traditional thermal method of preparing K₃PO₄ by reacting phosphoric acid with potassium hydroxide can obtain high-quality products, it consumes [...] Read more.

Potassium phosphate (K₃PO₄) is a common inorganic compound with broad applications in agriculture and industry. Although the traditional thermal method of preparing K₃PO₄ by reacting phosphoric acid with potassium hydroxide can obtain high-quality products, it consumes a lot of energy and has high costs. This study explores the process of preparing K₃PO₄ by Electrodialysis metathesis (EDM). This process uses sodium phosphate (Na₃PO₄) and potassium chloride (KCl) as raw materials and can prepare K₃PO₄ continuously. Under the optimized conditions (operating voltage of 8 V, 0.35 mol/L Na₃PO₄ and 1.05 mol/L KCl in raw flow with the rate of 30 mL/min), the product purity of K₃PO₄ reaches more than 97%, the energy consumption is 1191 kW·h/t, and the cost is about 8314 CNY/ton. Compared with traditional methods, EDM has the advantages of low cost, simple operation, and high utilization rate. This study shows that EDM technology has significant potential in preparing K₃PO₄. Full article

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

► Show Figures

Figure 1

20 pages, 16840 KiB

Open AccessArticle

Hydrogen and Ammonia Co-Adsorption on M(1 1 1) and Pd₃M(1 1 1) (M = Pd, Ru, Ag, Au, Cu) Surfaces

by Didrik R. Småbråten, Marie D. Strømsheim and Thijs A. Peters

Membranes 2025, 15(5), 135; https://doi.org/10.3390/membranes15050135 - 1 May 2025

Abstract

Ammonia (NH₃) represents a promising zero-emission fuel in hydrogen fuel cells. Membrane reactors for NH₃ decomposition based on Pd-alloys have demonstrated high NH₃ conversion, high hydrogen diffusivity, and high hydrogen selectivity, which allows for the production of high-purity H [...] Read more.

Ammonia (NH₃) represents a promising zero-emission fuel in hydrogen fuel cells. Membrane reactors for NH₃ decomposition based on Pd-alloys have demonstrated high NH₃ conversion, high hydrogen diffusivity, and high hydrogen selectivity, which allows for the production of high-purity H₂ without the need for gas separation or purification. However, it is observed that Pd-alloy membranes are to a various degree prone to H₂ flux inhibition in the presence of NH₃. Hence, finding proper means to tailor the surface adsorption properties through, e.g., alloying is imperative to further improve the technology. In the current work, hydrogen and ammonia co-adsorption phenomena on M(1 1 1) and Pd₃M(1 1 1) (M = Pd, Ru, Ag, Au, Cu) surfaces are studied using density functional theory calculations. It is shown that the surface adsorption properties are strongly dependent on the surface composition, which can be linked to the corresponding electronic structure at the membrane surface. Full article

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

► Show Figures

Figure 1

13 pages, 3991 KiB

Open AccessArticle

Effect of Folded Structures on Interfacial Solar-Driven Seawater Desalination

by Shufang Zhu, Yuke Niu and Xu Yan

Membranes 2025, 15(5), 134; https://doi.org/10.3390/membranes15050134 - 1 May 2025

Abstract

Currently, solar-driven interface evaporation for seawater desalination is believed to be an effective way to overcome freshwater shortage. To improve the efficiency of solar-driven interfacial evaporators, designing the evaporator’s structure is essential. In this study, we proposed a folded structure solar-driven interfacial evaporator [...] Read more.

Currently, solar-driven interface evaporation for seawater desalination is believed to be an effective way to overcome freshwater shortage. To improve the efficiency of solar-driven interfacial evaporators, designing the evaporator’s structure is essential. In this study, we proposed a folded structure solar-driven interfacial evaporator with electrospun recycled PET/carbon nanotube fibrous membranes. The as-spun membranes were folded into 4, 8, and 16 petals. The results suggested that F@8 (fold with eight petals) had the best solar-driven evaporation performance, with a photothermal conversion efficiency of 90.59% and an evaporation rate of 1.31 kg·m⁻²·h⁻¹, due to its lower light projection area and greater light absorption. The evaporation performance remained stable after 10 cycles. In addition, the concentration of ions in the freshwater collected after desalination was 2~3 orders of magnitude lower than that before desalination. These results indicate that a properly designed folded structure can effectively enhance evaporators through changing the light projection area and absorption. This approach might provide an effective way to optimize the structure of interfacial solar-driven evaporators. Full article

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

► Show Figures

Figure 1

9 pages, 2749 KiB

Open AccessCommunication

Carbonation of Ammonium Diuranate Filtrate to Enhance Uranium Rejection by Nanofiltration

by Runci Wang, Zhongwei Yuan, Xiang Meng, Taihong Yan and Weifang Zheng

Membranes 2025, 15(5), 133; https://doi.org/10.3390/membranes15050133 - 1 May 2025

Abstract

A commercial polymeric nanofiltration membrane (NF270, DuPont) was employed for uranium removal from ammonium diuranate filtrate (ADUF). Carbonate supplementation through ammonium carbonate addition enhanced uranium rejection via formation of uranyl–carbonate coordination complexes. Systematic speciation analysis of uranium species in ADUF was conducted, coupled [...] Read more.

A commercial polymeric nanofiltration membrane (NF270, DuPont) was employed for uranium removal from ammonium diuranate filtrate (ADUF). Carbonate supplementation through ammonium carbonate addition enhanced uranium rejection via formation of uranyl–carbonate coordination complexes. Systematic speciation analysis of uranium species in ADUF was conducted, coupled with calculation of the concentration polarization modulus to optimize ammonium carbonate dosage. The experimental results demonstrated that with 680 mg/L ammonium carbonate addition, the permeate uranium concentration decreased from 1.2 mg/L to 0.64 mg/L. This study confirms the technical feasibility of ADUF carbonation pretreatment for improving uranium retention efficiency in nanofiltration processes, achieving 46.7% reduction in uranium permeation flux. Full article

(This article belongs to the Topic Removing Challenging Pollutants from Wastewater: Effective Approaches)

► Show Figures

Figure 1

32 pages, 1900 KiB

Open AccessReview

Development and Investigation of a New Polysulfone Dialyzer with Increased Membrane Hydrophilicity

by Adam M. Zawada, Bettina Griesshaber, Bertram Ottillinger, Ansgar Erlenkötter, Nathan Crook, Skyler Boyington, Manuela Stauss-Grabo, James P. Kennedy and Thomas Lang

Membranes 2025, 15(5), 132; https://doi.org/10.3390/membranes15050132 - 30 Apr 2025

Abstract

Innovation in dialysis care is fundamental to improve well-being and outcomes of patients with end-stage kidney disease. The dialyzer is the core element of dialysis treatments, as it largely defines which substances are removed from the patient’s body. Moreover, its large surface size [...] Read more.

Innovation in dialysis care is fundamental to improve well-being and outcomes of patients with end-stage kidney disease. The dialyzer is the core element of dialysis treatments, as it largely defines which substances are removed from the patient’s body. Moreover, its large surface size is the major place of interaction of the patient’s blood with artificial surfaces and thus may lead to undesired effects such as inflammation or coagulation. In the present article we summarize the development path for a new dialyzer, including in vitro and clinical evidence generation. We use the example of the novel FX CorAL dialyzer, which has recently entered European and US markets, to show which steps are needed to develop and characterize a new dialyzer. The FX CorAL dialyzer includes a new hydrophilic membrane, which features reduced protein adsorption, sustained performance, and an improved hemocompatibility profile, characterized in numerous in vitro and clinical studies. Safety evaluations revealed a favorable profile, with low incidences of adverse device effects. Insights gained from both in vitro and clinical studies contribute to the advancement of dialyzer development, ultimately leading to improved patient care. Full article

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

► Show Figures

Figure 1

2 pages, 634 KiB

Open AccessCorrection

Correction: Zahid et al. Fabrication and Characterization of Sulfonated Graphene Oxide-Doped Polymeric Membranes with Improved Anti-Biofouling Behavior. Membranes 2021, 11, 563

by Muhammad Zahid, Anum Rashid, Saba Akram, H. M. Fayzan Shakir, Zulfiqar Ahmad Rehan, Talha Javed, Rubab Shabbir and Mahmoud M. Hessien

Membranes 2025, 15(5), 131; https://doi.org/10.3390/membranes15050131 - 29 Apr 2025

Abstract

In the original publication [...] Full article

(This article belongs to the Special Issue Microfluidics and MEMS Technology for Membranes)

► Show Figures

Figure 5

16 pages, 4236 KiB

Open AccessArticle

Halloysite-Nanotube-Mediated High-Flux γ-Al₂O₃ Ultrafiltration Membranes for Semiconductor Wastewater Treatment

by Shining Geng, Dazhi Chen, Zhenghua Guo, Qian Li, Manyu Wen, Jiahui Wang, Kaidi Guo, Jing Wang, Yu Wang, Liang Yu, Xinglong Li and Xiaohu Li

Membranes 2025, 15(5), 130; https://doi.org/10.3390/membranes15050130 - 27 Apr 2025

Abstract

The wastewater from Chemical Mechanical Polishing (CMP) generated in the semiconductor industry contains a significant concentration of suspended particles and necessitates rigorous treatment to meet environmental standards. Ceramic ultrafiltration membranes offer significant advantages in treating such high-solid wastewater, including a high separation efficiency, [...] Read more.

The wastewater from Chemical Mechanical Polishing (CMP) generated in the semiconductor industry contains a significant concentration of suspended particles and necessitates rigorous treatment to meet environmental standards. Ceramic ultrafiltration membranes offer significant advantages in treating such high-solid wastewater, including a high separation efficiency, environmental friendliness, and straightforward cleaning and maintenance. However, the preparation of high-precision ceramic ultrafiltration membranes with a smaller pore size (usually <20 nm) is very complicated, requiring the repeated construction of transition layers, which not only increases the time and economic costs of manufacturing but also leads to an elevated transport resistance. In this work, halloysite nanotubes (HNTs), characterized by their high aspect ratio and lumen structure, were utilized to create a high-porosity transition layer using a spray-coating technique, onto which a γ-Al₂O₃ ultrafiltration selective layer was subsequently coated. Compared to the conventional α-Al₂O₃ transition multilayers, the HNTs-derived transition layer not only had an improved porosity but also had a reduced pore size. As such, this strategy tended to simplify the preparation process for the ceramic membranes while reducing the transport resistance. The resulting high-flux γ-Al₂O₃ ultrafiltration membranes were used for the high-efficiency treatment of CMP wastewater, and the fouling behaviors were investigated. As expected, the HNTs-mediated γ-Al₂O₃ ultrafiltration membranes exhibited excellent water flux (126 LMH) and high rejection (99.4%) of inorganic particles in different solvent systems. In addition, such membranes demonstrated good operation stability and regeneration performance, showing promise for their application in the high-efficiency treatment of CMP wastewater in the semiconductor industry. Full article

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

► Show Figures

Figure 1

13 pages, 2280 KiB

Open AccessArticle

The Enrichment of Acetic Acid Using an Integrated Reverse Osmosis–Electrodialysis Process

by Shichang Xu, Long Zhang, Zhen Zhang, Lixin Xie and Wen Zhang

Membranes 2025, 15(5), 129; https://doi.org/10.3390/membranes15050129 - 27 Apr 2025

Abstract

In this study, the integrated process of reverse osmosis (RO) and electrodialysis (ED) is developed to concentrate the dilute solution of acetic acid (HAc). The key parameters, such as RO pressure, ED voltage, and ED volume ratio, were systematically evaluated and the operation [...] Read more.

In this study, the integrated process of reverse osmosis (RO) and electrodialysis (ED) is developed to concentrate the dilute solution of acetic acid (HAc). The key parameters, such as RO pressure, ED voltage, and ED volume ratio, were systematically evaluated and the operation conditions of the processes were optimized. Under an operating pressure of 5 MPa, RO can enrich low-concentration HAc from 1.5 wt.% to 6.5% wt.% and the energy consumption is 0.37 kW·h·kg⁻¹. Next, RO-concentrated water was used as the ED feed and the first ED with a volume ratio of the concentrated to dilute chamber of 1:4 was carried out under the conditions of a flow rate of 30 L/h and an operating voltage of 12 V; the HAc concentration reached 12.50 wt.%. The second ED with a volume ratio of 1:5 made the final HAc concentration reach 19.02 wt.%. This study shows that using RO-concentrated water instead of initial water for the ED process can reduce water energy consumption and cost markedly, and the RO–ED integrated process can efficiently pre-enrich low-concentration HAc aqueous solution, and the enriched HAc concentration meets the requirements for the further distillation of HAc. Full article

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

► Show Figures

Figure 1

15 pages, 4108 KiB

Open AccessArticle

Improved CO₂/CH₄ Separation in Carbon Molecular Sieve Membranes via Copolymerization of Long-Chain Flexible Structures

by Yingxiu Wu, Haiyan Guo, Bingyu Zhao, Yuxiu Yu, Yaodong Liu and Shouchun Zhang

Membranes 2025, 15(5), 128; https://doi.org/10.3390/membranes15050128 - 27 Apr 2025

Abstract

Carbon molecular sieve (CMS) membranes demonstrate considerable advantages and significant potential in the separation of CO₂ and CH₄. Nevertheless, current research predominantly emphasizes the enhancement of CMS membranes through the incorporation of rigid structures and chain spatial stacking. The role [...] Read more.

Carbon molecular sieve (CMS) membranes demonstrate considerable advantages and significant potential in the separation of CO₂ and CH₄. Nevertheless, current research predominantly emphasizes the enhancement of CMS membranes through the incorporation of rigid structures and chain spatial stacking. The role of flexible structures in this context remains inadequately understood. To address this gap, we introduced long-chain polydimethylsiloxane (PDMS) and copolymerized it to synthesize polyimide that combines rigid and flexible frameworks. This approach enabled us to investigate the impact of flexible structures on the structure and properties of carbon membranes by varying the PDMS content. The findings indicated that flexible PDMS significantly influenced the thermal decomposition behavior of polyimide and facilitated in situ silicon doping within the carbon membranes, thereby modifying the pore characteristics of the carbon film. Specifically, with a 10% addition of PDMS, the CO₂ permeability of the CMS membrane reached 9556 Barrer, representing an enhancement of 103.9% and surpassing the 2019 upper bound for CO₂/CH₄ separation. Furthermore, the effect of pyrolysis temperature was also examined. Ultimately, this study offers a novel perspective on regulating the structural and performance characteristics of carbon membranes through the integration of long-chain flexible structures. Full article

(This article belongs to the Topic Membrane Separation Technology Research)

► Show Figures

Figure 1

18 pages, 5086 KiB

Open AccessArticle

Addressing Contaminants of Emerging Concern in Aquaculture: A Vacuum Membrane Distillation Approach

by Claudio Marcos Eugênio Malaghini, Jussara Garcez, Rodrigo Hoff, Alan Ambrosi and Katia Rezzadori

Membranes 2025, 15(5), 127; https://doi.org/10.3390/membranes15050127 - 24 Apr 2025

Abstract

The presence of contaminants of emerging concern (CECs) in agricultural and fisheries water has raised significant environmental and health concerns. Vacuum membrane distillation (VMD) has shown promise as an effective method for removing non-volatile contaminants, such as CECs, from water. This study presents [...] Read more.

The presence of contaminants of emerging concern (CECs) in agricultural and fisheries water has raised significant environmental and health concerns. Vacuum membrane distillation (VMD) has shown promise as an effective method for removing non-volatile contaminants, such as CECs, from water. This study presents a novel application of a bench-scale VMD unit to treat water from Lagoa da Conceição, Florianópolis, Brazil, using microporous membranes (0.22 µm) under the following optimized conditions: 75 °C, a flow rate of 24 L·h⁻¹, and a vacuum pressure of −640 mmHg. The system demonstrated remarkable performance in removing several key antimicrobials, including sulfamethoxazole, ciprofloxacin, azithromycin, and clindamycin (500 μg·L⁻¹), with rejection rates of 99.1%, 98%, 99.9%, and 99%, respectively, and an average flux of 7.08 L·m⁻²·h⁻¹. Additionally, the VMD unit achieved a substantial 99.98% salt rejection. Ecotoxicity tests revealed low toxicity for sulfamethoxazole, ciprofloxacin, and azithromycin but high toxicity for clindamycin, while human risk assessment indicated moderate-to-high risks for ciprofloxacin and clindamycin. The findings highlight the potential of VMD as an effective and sustainable technology for the removal of CECs and biocompounds, enhancing water safety and reducing environmental hazards. This study offers a promising solution for addressing water contamination on a broader scale. Full article

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

► Show Figures

Figure 1

14 pages, 2980 KiB

Open AccessArticle

Modeling of Power Generation and Acid Recovery in an Analogous Process of Reverse Electrodialysis

by Qiaolin Lang, Yang Liu, Gaojuan Guo, Fei Liu and Yang Zhang

Membranes 2025, 15(4), 126; https://doi.org/10.3390/membranes15040126 - 20 Apr 2025

Abstract

The feasibility of an analogous reverse electrodialysis (RED) process for power generation and acid recovery from acidic waste streams in the steel industry is investigated in this study. A comprehensive model was established to simulate the transport phenomena and power generation, which was [...] Read more.

The feasibility of an analogous reverse electrodialysis (RED) process for power generation and acid recovery from acidic waste streams in the steel industry is investigated in this study. A comprehensive model was established to simulate the transport phenomena and power generation, which was validated through experimental data. The simulated operation time was 3 h, during which an acid recovery rate of 41.7% was achieved, and the maximum output power density reached 30.37 μW·cm⁻². The results demonstrated a strong dependence of output power density on the acid concentration, with a linear relationship within the tested range of 1.0–3.0 mol·L⁻¹ HCl. An optimal flow rate range was identified that maximized power output, with the best value of 90 mL∙min⁻¹. The differences in energy harvesting between the traditional acid diffusion dialysis process and our analogous RED process were demonstrated via simulation. The importance of system electroneutrality in driving ion migration and forming ionic currents was crucial for effective power generation. The analogous RED process is a promising solution for efficient acid recovery and power generation from industrial acid waste, offering a sustainable treatment approach. Full article

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

► Show Figures

Figure 1

14 pages, 1678 KiB

Open AccessArticle

Water Recovery from Laundry Wastewater by Integrated Purification Systems

by Aleksandra Klimonda and Izabela Kowalska

Membranes 2025, 15(4), 125; https://doi.org/10.3390/membranes15040125 - 14 Apr 2025

Abstract

Integrated systems for water recovery from laundry wastewater were investigated to close the water cycle loop. The grey water from the washing cycle of cotton fabrics with a softening detergent was prefiltered, purified in a low-pressure membrane process, and further purified in a [...] Read more.

Integrated systems for water recovery from laundry wastewater were investigated to close the water cycle loop. The grey water from the washing cycle of cotton fabrics with a softening detergent was prefiltered, purified in a low-pressure membrane process, and further purified in a high-pressure membrane process or alternatively in an adsorption process. In all of the proposed systems, the recovered water was clarified and completely free of cationic surfactants. The system based on nanofiltration as the final stage of purification allows soft water, which promotes better cleaning results, reduces the consumption of detergents, and extends the lifetime of the devices involved. Adsorption on activated carbon effectively reduced the concentration of organic compounds, including fragrance compounds. Full article

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

► Show Figures

Figure 1

Journal Description

Membranes

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI