Membranes

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)

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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)

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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)

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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)

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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)

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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)

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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)

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13 pages, 34194 KiB

Open AccessArticle

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

Abstract

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

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

(This article belongs to the Section Biological Membranes)

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16 pages, 2914 KiB

Open AccessArticle

Electrochemical Characterization and Simulation of Ion Transport in Anion Exchange Membranes for Water Treatment Applications

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

Membranes 2025, 15(4), 123; https://doi.org/10.3390/membranes15040123 - 13 Apr 2025

Abstract

This study presents a comprehensive electrochemical characterization and simulation of anion exchange membranes (AEMs) for water treatment applications, focusing on ion transport behavior. Experimental techniques, including chronopotentiometry, current–voltage (I–V) curve measurements, and electrochemical impedance spectroscopy (EIS), were employed to investigate the kinetics and [...] Read more.

This study presents a comprehensive electrochemical characterization and simulation of anion exchange membranes (AEMs) for water treatment applications, focusing on ion transport behavior. Experimental techniques, including chronopotentiometry, current–voltage (I–V) curve measurements, and electrochemical impedance spectroscopy (EIS), were employed to investigate the kinetics and dynamics of ion transport at the membrane interface. The results were validated and further explored through finite element method (FEM) simulations using COMSOL Multiphysics. The study revealed key insights into the role of membrane resistance, ion diffusion, and capacitive effects on overall membrane performance. Parametric analyses of electrolyte layer thickness, bulk solution concentration, and membrane porosity provided guidelines for optimizing membrane design. The findings highlight the importance of considering these factors in enhancing the efficiency and applicability of AEMs in water treatment processes. Future work will focus on refining simulation models and exploring advanced materials to further improve membrane performance. Full article

(This article belongs to the Special Issue Research on Electrodialytic Processes)

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10 pages, 2413 KiB

Open AccessArticle

A Comparison Between Calcium and Strontium Transport by the (Ca²⁺ + Mg²⁺)ATPase of the Basolateral Plasma Membrane of Renal Proximal Convoluted Tubules

by José Roberto Meyer-Fernandes, Mauro Sola-Penna and Adalberto Vieyra

Membranes 2025, 15(4), 122; https://doi.org/10.3390/membranes15040122 - 12 Apr 2025

Abstract

In this work, the utilization of calcium and strontium by the (Ca²⁺ + Mg²⁺)ATPase of the basolateral plasma membrane of renal proximal convoluted tubules were compared. [⁹⁰Sr]Sr²⁺ and [⁴⁵Ca]Ca²⁺ uptake by vesicles derived from [...] Read more.

In this work, the utilization of calcium and strontium by the (Ca²⁺ + Mg²⁺)ATPase of the basolateral plasma membrane of renal proximal convoluted tubules were compared. [⁹⁰Sr]Sr²⁺ and [⁴⁵Ca]Ca²⁺ uptake by vesicles derived from this membrane were strictly dependent on ATP and Mg²⁺, and no other nucleotide was able to support the transport. Each cation inhibited the uptake of the other one in a purely competitive fashion (the same Vmax; increased K_0.5), without causing a significant change in the influx rate. These results indicate that both cations bind at the same transport site on the enzyme, facing the cytosolic surface of the cell. The K_0.5 for Sr²⁺ obtained for (Sr²⁺ + Mg²⁺)ATPase activity was 13.1 ± 0.2 µM and for Sr²⁺ uptake was 13.4 ± 0.1 µM. They were higher than K_0.5 for Ca²⁺ obtained for (Ca²⁺ + Mg²⁺)ATPase activity (0.42 ± 0.03 µM) and for Ca²⁺ uptake (0.28 ± 0.02 µM). It is postulated that the lower ATPase affinity for Sr²⁺ is associated with greater steric difficulties for the occupation by this cation of the binding and transport sites, as a consequence of its greater crystal ionic radius (1.13 Å for Sr²⁺ against 0.99 Å for Ca²⁺). Full article

(This article belongs to the Section Biological Membranes)

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17 pages, 3054 KiB

Open AccessArticle

Efficient Separation of a Novel Microbial Chassis, Vibrio natriegens, from High-Salt Culture Broth Using Ceramic Ultrafiltration Membranes

by Stefan Schwarz, Rong Fan, Mehrdad Ebrahimi and Peter Czermak

Membranes 2025, 15(4), 121; https://doi.org/10.3390/membranes15040121 - 11 Apr 2025

Abstract

Vibrio natriegens is widely used as a production host for biotechnological processes due to its superior maximum glucose consumption rate, high growth rate, and abundant ribosomes. Most bioprocesses also need a scalable biomass separation step. This can be achieved by cross-flow filtration with [...] Read more.

Vibrio natriegens is widely used as a production host for biotechnological processes due to its superior maximum glucose consumption rate, high growth rate, and abundant ribosomes. Most bioprocesses also need a scalable biomass separation step. This can be achieved by cross-flow filtration with ceramic membranes, although the membrane pores are susceptible to fouling. However, the fouling characteristics of V. natriegens culture broth have not been investigated in detail. We therefore characterized membrane fouling during the separation of V. natriegens biomass from culture broth using a cross-flow filtration plant with ceramic membranes. The resistance in series model was used to quantify the fouling-induced resistance caused by the different components of the culture broth. The total fouling resistance was 4.1·10⁹ ± 0.6·10⁹ m⁻¹ for the culture broth and 5.4·10⁹ ± 0.7·10⁹ m⁻¹ for the summed broth components. Reversible resistance accounted for 86% and 81% of these totals, respectively. We then applied Hermia’s adapted filtration laws to determine the dominant fouling mechanism induced by the different broth components. In a further step, we established a setup to determine the compressibility index of the cells during cross-flow filtration, resulting in an estimated value of 0.55 ± 0.04. These results will facilitate the design of economic filtration plants and will help to establish V. natriegens as a production host for large-scale industrial processes. Full article

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

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25 pages, 6238 KiB

Open AccessArticle

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

Abstract

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

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

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

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14 pages, 3423 KiB

Open AccessArticle

Changes in Tubular PVDF Membrane Performance During Initial Period of Pilot Plant Operation

by Marek Gryta and Wirginia Tomczak

Membranes 2025, 15(4), 119; https://doi.org/10.3390/membranes15040119 - 9 Apr 2025

Abstract

Ultrafiltration (UF) is increasingly used in the food industry and for wastewater treatment and water reuse. Knowledge of the membrane properties that stabilise during the initial period of module operation in an industrial plant is essential for design purposes. This paper presents the [...] Read more.

Ultrafiltration (UF) is increasingly used in the food industry and for wastewater treatment and water reuse. Knowledge of the membrane properties that stabilise during the initial period of module operation in an industrial plant is essential for design purposes. This paper presents the experimental tests carried out using a pilot plant with an industrial PCI B1 membrane module. The module was equipped with tubular FP100 (100 kDa) polyvinylidene fluoride (PVDF) membranes used to separate carwash wastewater. The effect of membrane compaction during the first few days of the process on changes in permeate flux and dextran (40–500 kDa) separation rate was investigated. The effect of fouling, membrane washing with P3 Ultrasill 11 solution (pH = 12) and maintenance with sodium metabisulfite solution on the stabilisation of the technological performance of the plant was determined. 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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13 pages, 3927 KiB

Open AccessArticle

Effects of Latent Solvent Content on Tuning the Nanofiltration Performance of Nanofibrous Composite Membranes

by Xu-Dong Cao, Yu-Xuan Shao, Qian Wang, Tian-Dan Lu and Jing Zhong

Membranes 2025, 15(4), 118; https://doi.org/10.3390/membranes15040118 - 8 Apr 2025

Abstract

This study aims to optimize the application of electrospun nanofibrous substrates in thin-film composite (TFC) nanofiltration (NF) membranes for enhanced liquid separation efficiency by employing a method of effective welding between fibers using latent solvents. Polyacrylonitrile (PAN) nanofiber substrates were fabricated via electrospinning, [...] Read more.

This study aims to optimize the application of electrospun nanofibrous substrates in thin-film composite (TFC) nanofiltration (NF) membranes for enhanced liquid separation efficiency by employing a method of effective welding between fibers using latent solvents. Polyacrylonitrile (PAN) nanofiber substrates were fabricated via electrospinning, and a dense polyamide selective layer was formed on their surface through interfacial polymerization (IP). The investigation focused on the effects of different solvent systems, particularly the role of dimethyl sulfoxide (DMSO) as a latent solvent, on the nanostructure and final membrane performance. The results indicate that increasing the DMSO content can enhance the greenness of the fabrication process, the substrate hydrophilicity, and the mechanical strength, while also influencing the thickness and morphology of the polyamide layer. At a DMSO rate of 30%, the composite membrane achieves optimal pure water permeability and high rejection rates; when the DMSO content exceeds 40%, structural inhomogeneity in the substrate membrane leads to an increase in defects, significantly deteriorating membrane performance. These findings provide theoretical insights and technical guidance for the application of electrospinning technology in designing efficient and stable NF membranes. Full article

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

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26 pages, 1509 KiB

Open AccessReview

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

Abstract

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

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

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

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16 pages, 2720 KiB

Open AccessArticle

Ultrapure Water Production by a Saline Industrial Effluent Treatment

by Adriana Hernández Miraflores, Karina Hernández Gómez, Claudia Muro, María Claudia Delgado Hernández, Vianney Díaz Blancas, Jesús Álvarez Sánchez and German Eduardo Devora Isordia

Membranes 2025, 15(4), 116; https://doi.org/10.3390/membranes15040116 - 7 Apr 2025

Abstract

A membrane system was applied for ultrapure water production from the treatment of saline effluent from the canned food industry. The industrial effluent presented a high saline concentration, including sodium chloride, calcium carbonate, calcium sulfates, and magnesium. The effluent was treated using a [...] Read more.

A membrane system was applied for ultrapure water production from the treatment of saline effluent from the canned food industry. The industrial effluent presented a high saline concentration, including sodium chloride, calcium carbonate, calcium sulfates, and magnesium. The effluent was treated using a system of reverse osmosis (RO) and a post-treatment process consisting of ion exchange resins (IEXRs). The RO was accompanied by the addition of a hexametaphosphate dose (2, 6, and 10 mg/L) as an antiscalant to avoid the RO membrane scaling by minerals. In turn, IEXRs were used for water deionization to produce ultrapure water with a reduced concentration of monovalent ions. The antiscalant dose was 6 mg/L, producing clean water from RO permeates with an efficiency of 65–70%. The brine from RO was projected for its reuse in food industry processes. The clean water quality from RO showed 20% total dissolved solids (TDS) removal (equivalent to salts). The antiscalant inhibited the formation of calcium salt incrustation > 200 mg/L, showing low fouling. In turn, anionic resins removed 99.8% of chloride ions, whereas the monovalent salts were removed by a mix of cationic–anionic resin, producing ultrapure water with electrical conductivity < 3.3 µS/cm. The cost of ultrapure water production was 2.62 USD/m³. Full article

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

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17 pages, 6225 KiB

Open AccessArticle

RF Sputtering of Gold Nanoparticles in Liquid and Direct Transfer to Nafion Membrane for PEM Water Electrolysis

by Chandrakanth Reddy Chandraiahgari, Gloria Gottardi, Giorgio Speranza, Beatrice Muzzi, Domenico Dalessandro, Andrea Pedrielli, Victor Micheli, Ruben Bartali, Nadhira Bensaada Laidani and Matteo Testi

Membranes 2025, 15(4), 115; https://doi.org/10.3390/membranes15040115 - 7 Apr 2025

Abstract

Sputtering onto liquids is rapidly gaining attention for the green and controlled dry synthesis of ultrapure catalysts nanomaterials. In this study, we present a clean and single-step method for the synthesis of gold nanoparticles directly in polyethylene glycol (PEG) liquid using radio frequency [...] Read more.

Sputtering onto liquids is rapidly gaining attention for the green and controlled dry synthesis of ultrapure catalysts nanomaterials. In this study, we present a clean and single-step method for the synthesis of gold nanoparticles directly in polyethylene glycol (PEG) liquid using radio frequency (RF) magnetron sputtering and by subsequently transferring them to Nafion ionomer, fabricating a catalyst-coated membrane (CCM), an essential component of the proton exchange membrane water electrolyzer (PEMWE). The samples were systematically characterized at different stages of process development. The innovative transfer process resulted in a monodispersed homogeneous distribution of catalyst particles inside CCM while retaining their nascent nanoscale topography. The chemical analysis confirmed the complete removal of the trapped PEG through the process optimization. The electrochemical catalytic activity of the optimized CCM was verified, and the hydrogen evolution reaction (HER) in acidic media appeared outstanding, a vital step in water electrolysis toward H₂ production. Therefore, this first study highlights the advantages of RF sputtering in liquid for nanoparticle synthesis and its direct application in preparing CCM, paving the way for the development of innovative membrane preparation techniques for water electrolysis. Full article

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

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11 pages, 5466 KiB

Open AccessArticle

Electrocatalytic PANI-Encapsulated Aluminum Silicate/Ceramic Membranes for Efficient and Energy-Saving Removal of 4-Chlorophenol in Wastewater

by Shuo Wang, Tianhao Huang, Haoran Ma, Zihan Liu, Houbing Xia, Zhiqiang Sun, Jun Ma and Ying Zhao

Membranes 2025, 15(4), 114; https://doi.org/10.3390/membranes15040114 - 7 Apr 2025

Abstract

The removal of chlorinated organic pollutants from wastewater is a critical environmental challenge, as traditional methods for treating toxic pollutants like phenol and chlorophenols often suffer from high energy consumption and long treatment times, limiting their practical use. Electrocatalytic filtration has emerged as [...] Read more.

The removal of chlorinated organic pollutants from wastewater is a critical environmental challenge, as traditional methods for treating toxic pollutants like phenol and chlorophenols often suffer from high energy consumption and long treatment times, limiting their practical use. Electrocatalytic filtration has emerged as a promising alternative, but efficient, energy-saving electrocatalytic membranes for pollutants like 4-chlorophenol (4-CP) are still underexplored. A new type of electrocatalytic coupling membrane catalyst, ASP/CM (PANI-encapsulated aluminum silicate/ceramic membrane), was prepared using inexpensive silicate and polyaniline as the base materials, with in situ polymerization combined with co-focus magnetron sputtering. Under optimal conditions (25 mA/cm², 10 mM Na₂SO₄, 1.0 mL·min⁻¹ flow rate, and 50 μM 4-CP concentration), the membrane achieved about 95.1% removal of 4-CP and the degradation rate after five cycles was higher than 85%. In addition, O₂^•− and •OH are important active species in the electrocatalytic degradation of 4-CP. The 4-CP electrocatalytic membrane filtration process is a dual process of cathode reduction dechlorination and anodic oxidation. This work offers new insights into developing next-generation electrocatalytic membranes and expands the practical applications of electrocatalytic filtration systems. Full article

(This article belongs to the Special Issue Membrane Catalytic Oxidation in Water Treatment)

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19 pages, 2820 KiB

Open AccessArticle

Process Simulation of High-Pressure Nanofiltration (HPNF) for Membrane Brine Concentration (MBC): A Pilot-Scale Case Study

by Abdallatif Satti Abdalrhman, Sangho Lee, Seungwon Ihm, Eslam S. B. Alwaznani, Christopher M. Fellows and Sheng Li

Membranes 2025, 15(4), 113; https://doi.org/10.3390/membranes15040113 - 4 Apr 2025

Abstract

The growing demand for sustainable water management solutions has prompted the development of membrane brine concentration (MBC) technologies, particularly in the context of desalination and minimum liquid discharge (MLD) applications. This study presents a simple model of high-pressure nanofiltration (HPNF) for MBC. The [...] Read more.

The growing demand for sustainable water management solutions has prompted the development of membrane brine concentration (MBC) technologies, particularly in the context of desalination and minimum liquid discharge (MLD) applications. This study presents a simple model of high-pressure nanofiltration (HPNF) for MBC. The model integrates reverse osmosis (RO) transport equations with mass balance equations, thereby enabling acceptable predictions of water flux and total dissolved solids (TDS) concentration. Considering the limitations of the pilot plant data, the model showed reasonable accuracy in predicting flux and TDS, with R² values above 0.99. The simulation results demonstrated that an increase in feed flow rate improves flux but raises specific energy consumption (SEC) and reduces recovery. In contrast, an increase in feed pressure results in an increased recovery and brine concentration. Increasing feed TDS decreases flux, recovery, and final brine TDS and increases SEC. Response surface methodology (RSM) was employed to optimize process performance across multiple criteria, optimizing flux, SEC, recovery, and final brine concentration. The optimal feed flow rate and pressure vary depending on the criteria in the improvement scenarios, underscoring the importance of systematic process improvement. Full article

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

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Membranes

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