Membranes

21 pages, 846 KiB

Open AccessReview

Membrane Technologies for Sustainable Wastewater Treatment: Advances, Challenges, and Applications in Zero Liquid Discharge (ZLD) and Minimal Liquid Discharge (MLD) Systems

by Argyris Panagopoulos and Panagiotis Michailidis

Membranes 2025, 15(2), 64; https://doi.org/10.3390/membranes15020064 - 19 Feb 2025

Cited by 1 | Viewed by 1217

Abstract

As the demand for sustainable water and wastewater management continues to rise in both desalination and industrial sectors, there is been notable progress in developing Zero Liquid Discharge (ZLD) and Minimal Liquid Discharge (MLD) systems. Membrane technologies have become a key component of [...] Read more.

As the demand for sustainable water and wastewater management continues to rise in both desalination and industrial sectors, there is been notable progress in developing Zero Liquid Discharge (ZLD) and Minimal Liquid Discharge (MLD) systems. Membrane technologies have become a key component of these systems, providing effective solutions for removing contaminants and enabling the recovery of both water and valuable resources. This article explores recent advancements in the design and operation of ZLD and MLD systems, discussing their benefits, challenges, and how they fit into larger treatment processes. Emphasis is given to membrane-based processes, such as reverse osmosis (RO), membrane distillation (MD), and forward osmosis (FO), as well as hybrid configurations, and innovative membrane materials. These advancements are designed to address critical challenges like fouling, scaling, high energy demands, and high brine production. The article also explores exciting research directions aimed at enhancing the efficiency and durability of membrane technologies in ZLD and MLD systems, paving the way for new innovations in sustainable water management across various industries. Full article

(This article belongs to the Special Issue Green Membrane Technologies: Advancements in Materials and Energy Efficiency for Water Treatment)

► Show Figures

Figure 1

18 pages, 6100 KiB

Open AccessArticle

The Effect of Membrane Surface Hydrophobicity on the Performance and Water Production Cost of a Desalination Unit

by Sima Rabiei and Anthony H. J. Paterson

Membranes 2025, 15(2), 63; https://doi.org/10.3390/membranes15020063 - 14 Feb 2025

Viewed by 741

Abstract

Membrane pore wetting remains a significant challenge to achieving the stable operation and commercialization of membrane distillation processes. This study quantitatively assessed membrane surface hydrophobicity to investigate its impact on the performance and water production cost of an MD system. Membranes with a [...] Read more.

Membrane pore wetting remains a significant challenge to achieving the stable operation and commercialization of membrane distillation processes. This study quantitatively assessed membrane surface hydrophobicity to investigate its impact on the performance and water production cost of an MD system. Membranes with a similar pore wetting resistance but differing in surface hydrophobicity and pore diameter were examined. A direct contact membrane distillation unit was modeled, and the water flux results were compared with laboratory experiments to validate the model. The validated model was subsequently employed to simulate a seawater desalination plant with a designed capacity of 20 m³/day. The results demonstrated that membranes with a higher surface hydrophobicity and bigger pore sizes achieved higher water flux, increasing from 0.6 kg/m²·h to 2.5 kg/m²·h, and significantly reduced water production costs from NZD$13.5/m³ to $3.9/m³. This research highlights the importance of optimizing membrane surface properties and microstructures to advance MD applications. Full article

(This article belongs to the Special Issue Applications of Membrane Distillation in Water Treatment and Reuse)

► Show Figures

Figure 1

15 pages, 1533 KiB

Open AccessArticle

Recovering Ammonia as Ammonium Citrate and Ammonium Sulfate from Sludge Digestion Liquors Using Membrane Contactors in a Pilot Plant

by Ricardo Reyes Alva, Marius Mohr, Günter E. M. Tovar and Susanne Zibek

Membranes 2025, 15(2), 62; https://doi.org/10.3390/membranes15020062 - 13 Feb 2025

Viewed by 762

Abstract

Membrane contactors have proved to be effective for recovering ammonia from wastewater by absorbing it into a trapping solution. This study compares the performance of sulfuric acid and citric acid as trapping solutions in a pilot-scale plant for recovering ammonia from sludge digestion [...] Read more.

Membrane contactors have proved to be effective for recovering ammonia from wastewater by absorbing it into a trapping solution. This study compares the performance of sulfuric acid and citric acid as trapping solutions in a pilot-scale plant for recovering ammonia from sludge digestion liquors using membrane contactors in a liquid–liquid configuration operating at pH 10 and a temperature of 37 °C and using ultrafiltration (UF) technology as pretreatment. The performance of the process using sulfuric acid at a lower pH (9.5) and temperature (30 °C) was also studied, as well as the advantage of including a CO₂-stripping module in the process. The ammonia elimination efficiency was 88% and 86% when using sulfuric acid and citric acid, respectively. The nitrogen concentration of the produced ammonium sulfate and ammonium citrate reached 23.2 and 14.7 g NH₃-N·L⁻¹, respectively. The ammonia elimination efficiency when using sulfuric acid decreased to 49% when decreasing the pH to 9.5 and to 85% when decreasing the temperature to 31 °C. UF technology was able to reduce the concentration of suspended solids by 90% and the chemical oxygen demand by 37%. However, the UF membranes for the pretreatment and the membrane contactors for ammonia recovery had to be constantly cleaned with acid due to scaling, which significantly increased maintenance efforts. The CO₂-stripping module reduced the consumption of the caustic soda solution by 23% for increasing the pH level of the treated water. Finally, the specific energy consumption of the plant was 8 kWh·m⁻³. Full article

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

► Show Figures

Figure 1

15 pages, 1783 KiB

Open AccessArticle

Surface-Charge Characterization of Nanocomposite Cellulose Acetate/Silver Membranes and BSA Permeation Performance

by Ana Sofia Figueiredo, María Guadalupe Sánchez-Loredo, Maria Norberta de Pinho and Miguel Minhalma

Membranes 2025, 15(2), 61; https://doi.org/10.3390/membranes15020061 - 11 Feb 2025

Cited by 1 | Viewed by 910

Abstract

Membrane processes are a reality in a wide range of industrial applications, and efforts to continuously enhance their performance are being pursued. The major drawbacks encountered are related to the minimization of polarization concentration, fouling, and biofouling formation. In this study, silver nanoparticles [...] Read more.

Membrane processes are a reality in a wide range of industrial applications, and efforts to continuously enhance their performance are being pursued. The major drawbacks encountered are related to the minimization of polarization concentration, fouling, and biofouling formation. In this study, silver nanoparticles were added to the casting solutions of cellulose acetate membranes in order to obtain new hybrid membranes that present characteristics inherent to the silver nanoparticles, namely antibacterial behavior that leads to biofouling reduction. A systematic study was developed to assess the effect of ionic strength, membrane polymeric structure, and silver nanoparticle incorporation on the cellulose acetate (CA) membrane surface charge. Surface charge was quantified by streaming potential measurements and it was correlated with BSA permeation performance. CA membranes were prepared by the phase-inversion method using three casting-solution compositions, to obtain membranes with different polymeric structures (CA400-22, CA400-30, CA400-34). The nanocomposite CA/silver membranes (CA/Ag) were prepared through the incorporation of silver nanoparticles (0.1 and 0.4 wt% Ag) in the casting solutions of the membranes. To evaluate the electrolyte concentration effect on the membranes zeta potential and surface charge, two potassium chloride solutions of 1 mM and 5 mM were used, in the pH range between 4 and 9. The results show that the zeta-potential values of CA/Ag membranes were less negative when compared to the silver-free membranes, and almost independent of the silver content and the pH of the solution. The influence of the protein solution pH and the protein charge in the BSA solutions permeation was studied. The pH conditions that led to the lower permeate fluxes were observed at the isoelectric point of BSA, pH = 4.8. Full article

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

► Show Figures

Figure 1

15 pages, 2733 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 1217

Abstract

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

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

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

► Show Figures

Figure 1

12 pages, 4220 KiB

Open AccessArticle

Loose Polyester Nanofiltration Membrane Designed with Hydroxyl-Ammonium for Efficient Dye/Salt Separation

by Nan Ma, Guiliang Li, Yang Liu, Shenghua Zhou and Fu Liu

Membranes 2025, 15(2), 59; https://doi.org/10.3390/membranes15020059 - 10 Feb 2025

Cited by 1 | Viewed by 838

Abstract

Efficient dye/salt separation poses a great challenge to nanofiltration (NF) membrane technology in the desalting sector of the dye synthesis industry. In this study, we fabricated a novel loose polyester NF membrane via an interfacial polymerization method using “hydroxyl-ammonium” biquaternary diethanolamine (MDET) and [...] Read more.

Efficient dye/salt separation poses a great challenge to nanofiltration (NF) membrane technology in the desalting sector of the dye synthesis industry. In this study, we fabricated a novel loose polyester NF membrane via an interfacial polymerization method using “hydroxyl-ammonium” biquaternary diethanolamine (MDET) and trimesoyl chloride. The molecular design of MDET provides a loose crosslinking network, showing high rejection of dyes and the passage of monovalent salt/divalent salt ions in the dye solution, exhibiting exceptional filtration efficiency with high selectivity. Furthermore, the membrane exhibits excellent operational stability for over 100 h, demonstrating superior antifouling properties and high resistance to chlorine. This study provides new insights into the role of dyes and mono- and divalent ions in desalination processes related to the dye synthesis industry. Full article

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

► Show Figures

Figure 1

14 pages, 10244 KiB

Open AccessArticle

Hydrophobic Membrane Wettability: Effects of Salinity and Temperature

by Orhan Kaya

Membranes 2025, 15(2), 58; https://doi.org/10.3390/membranes15020058 - 9 Feb 2025

Viewed by 1171

Abstract

In this study, molecular dynamics (MD) simulations were used to investigate the effects of salinity (NaCl) and temperature (25 °C and 80 °C) on the wettability of droplets on a realistically modeled hydrophobic PTFE (polytetrafluoroethylene) surface. Droplet sizes of 20, 25, and 30 [...] Read more.

In this study, molecular dynamics (MD) simulations were used to investigate the effects of salinity (NaCl) and temperature (25 °C and 80 °C) on the wettability of droplets on a realistically modeled hydrophobic PTFE (polytetrafluoroethylene) surface. Droplet sizes of 20, 25, and 30 nm were analyzed using both pure water and 8.45% NaCl solutions. The results indicated that salinity increased the contact angles, strengthening the PTFE’s hydrophobicity by disrupting the water’s hydrogen bonding at the interface and reducing the spreading area. Higher temperatures also led to an increase in contact angles by decreasing water structuring, although this effect was less pronounced than that of salinity. Ion concentration analysis revealed that a significant number of ions migrated away from the PTFE surface, a phenomenon further clarified through radial distribution function (RDF) analysis. Full article

(This article belongs to the Collection Feature Papers in Membrane Surface and Interfaces)

► Show Figures

Figure 1

26 pages, 31738 KiB

Open AccessArticle

Bi-Objective Optimization of Techno-Economic and Environmental Performance for Membrane-Based CO₂ Capture via Single-Stage Membrane Separation

by Nobuo Hara, Satoshi Taniguchi, Takehiro Yamaki, Thuy T. H. Nguyen and Sho Kataoka

Membranes 2025, 15(2), 57; https://doi.org/10.3390/membranes15020057 - 9 Feb 2025

Cited by 1 | Viewed by 847

Abstract

Various factors need to be considered in process design optimization to implement the complex processes of CO₂ capture, utilization, and storage (CCUS). Here, bi-objective optimization of single-stage CO₂ membrane separation was performed for two evaluation indexes: cost and CO₂ emissions. [...] Read more.

Various factors need to be considered in process design optimization to implement the complex processes of CO₂ capture, utilization, and storage (CCUS). Here, bi-objective optimization of single-stage CO₂ membrane separation was performed for two evaluation indexes: cost and CO₂ emissions. During optimization, the process flow configuration was fixed, the membrane performance was set under the condition of the Robeson upper bound, and the membrane area and operating conditions were set as variables. Bi-objective optimization was performed using an original algorithm that combines the adaptive design of experiments, machine learning, a genetic algorithm, and Bayesian optimization. Five case studies with different product CO₂ purities in the constraint were analyzed. Pareto solutions were superior for case studies with lower product CO₂ purities. The set of Pareto solutions revealed opposite directions for optimization: either (1) increase the membrane area to reduce CO₂ emissions but increase costs or (2) increase power consumption and reduce costs but increase CO₂ emissions. The implemented bi-objective optimization approach is promising for evaluating the membrane CO₂ capture process and the individual processes of CCUS. Full article

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

► Show Figures

Figure 1

24 pages, 12218 KiB

Open AccessArticle

Application of Membrane Capacitive Deionization as Pretreatment Strategy for Enhancing Salinity Gradient Power Generation

by Seoyeon Lee, Juyoung Lee, Jaehyun Ju, Hyeongrak Cho, Yongjun Choi and Sangho Lee

Membranes 2025, 15(2), 56; https://doi.org/10.3390/membranes15020056 - 8 Feb 2025

Viewed by 923

Abstract

Salinity gradient power (SGP) technologies, including pressure-retarded osmosis (PRO) and reverse electrodialysis (RED), have the potential to be utilized for the purpose of harvesting energy from the difference in salinity between two water streams. One challenge associated with SGP is a reduction in [...] Read more.

Salinity gradient power (SGP) technologies, including pressure-retarded osmosis (PRO) and reverse electrodialysis (RED), have the potential to be utilized for the purpose of harvesting energy from the difference in salinity between two water streams. One challenge associated with SGP is a reduction in power density due to membrane fouling when impaired water is utilized as a low-salinity water stream. Accordingly, this study sought to explore the feasibility of membrane capacitive deionization (MCDI), a low-energy water treatment technique, as a novel pretreatment method for SGP. Laboratory-scale experiments were conducted to evaluate the impact of MCDI pretreatment on the performance of PRO and RED. The low-salinity water was obtained from a brackish water reverse osmosis (BWRO) plant, while the high-salinity water was a synthetic seawater desalination brine. The removal efficiency of organic and inorganic substances in brackish water reverse osmosis (BWRO) brine by MCDI was estimated, as well as theoretical energy consumption. The results demonstrated that MCDI attained removal efficiencies of up to 88.8% for organic substances and 78.8% for inorganic substances. This resulted in a notable enhancement in the lower density for both PRO and RED. The power density of PRO exhibited a notable enhancement, reaching 3.57 W/m² in comparison to 1.14 W/m² recorded for the BWRO brine. Conversely, the power density of RED increased from 1.47 W/m² to 2.05 W/m². Given that the energy consumption by MCDI is relatively low, it can be surmised that the MCDI pretreatment enhances the overall efficiency of both PRO and RED. However, to fully capitalize on the benefits of MCDI pretreatment, it is recommended that further process optimization be conducted. Full article

(This article belongs to the Special Issue Electrodialysis and Novel Electro-Membrane Processes)

► Show Figures

Figure 1

24 pages, 2060 KiB

Open AccessReview

Challenges and Opportunities of Choosing a Membrane for Electrochemical CO₂ Reduction

by Helene Rehberger, Mohammad Rezaei and Abdalaziz Aljabour

Membranes 2025, 15(2), 55; https://doi.org/10.3390/membranes15020055 - 8 Feb 2025

Cited by 1 | Viewed by 1097

Abstract

The urgent need to reduce greenhouse gas emissions, particularly carbon dioxide (CO₂), has led to intensive research into novel techniques for synthesizing valuable chemicals that address climate change. One technique that is becoming increasingly important is the electrochemical reduction of CO [...] Read more.

The urgent need to reduce greenhouse gas emissions, particularly carbon dioxide (CO₂), has led to intensive research into novel techniques for synthesizing valuable chemicals that address climate change. One technique that is becoming increasingly important is the electrochemical reduction of CO₂ to produce carbon monoxide (CO), an important feedstock for various industrial processes. This comprehensive review examines the latest developments in CO₂ electroreduction, focusing on mechanisms, catalysts, reaction pathways, and optimization strategies to enhance CO production efficiency. A particular emphasis is placed on the role of ion exchange membranes, including cation exchange membranes (CEMs), anion exchange membranes (AEMs), and bipolar membranes (BPMs). The review explores their advantages, disadvantages, and the current challenges associated with their implementation in CO₂ electroreduction systems. Through careful analysis of the current literature, this report aims to provide a comprehensive understanding of state-of-the-art methods and their potential impact on sustainable CO production, with a special focus on membrane technologies. Full article

(This article belongs to the Special Issue Innovative Membrane-Based Approaches to CO₂ Electroreduction: From Fundamentals to Applications)

► Show Figures

Figure 1

11 pages, 8815 KiB

Open AccessArticle

Preparation and Modification of Silicalite-2 Membranes

by Yin Yang, Juan Liu, Qi Zhou, Siqi Shao, Lingling Zou, Wenjun Yuan, Meihua Zhu, Xiangshu Chen and Hidetoshi Kita

Membranes 2025, 15(2), 54; https://doi.org/10.3390/membranes15020054 - 8 Feb 2025

Viewed by 681

Abstract

Silicalite-2 membranes were successfully prepared on tubular α-Al₂O₃ supports by secondary hydrothermal synthesis, and the pervaporation performance of the membrane was evaluated by separation of a 5 wt% ethanol/H₂O mixture at 60 °C. The effects of templating agent [...] Read more.

Silicalite-2 membranes were successfully prepared on tubular α-Al₂O₃ supports by secondary hydrothermal synthesis, and the pervaporation performance of the membrane was evaluated by separation of a 5 wt% ethanol/H₂O mixture at 60 °C. The effects of templating agent content, water–silicon ratio and crystallization time on the separation performance of Silicalite-2 membranes were investigated. When the TBAOH/SiO₂ and H₂O/SiO₂ molar ratios of the precursor synthesis solution were 0.2 and 120, a dense Silicalite-2 membrane could be prepared on the surface of the tubular α-Al₂O₃ support after 72 h. The silane coupling agent was utilized to treat the Silicalite-2 membranes, and the effects of silane coupling agent dosage on their properties were also explored. The pervaporation performance of the Silicalite-2 membrane was greatly improved with a 5.7 wt% trimethylchlorosilane (TMCS) solution and the flux and separation factor of the membrane reached 1.75 kg·m⁻²·h⁻¹ and 22 for separation of 5 wt% EtOH/H₂O at 60 °C, respectively. Full article

(This article belongs to the Special Issue Zeolite Membranes and Membrane Reactor for Liquid Separation and Catalytic Application: Synthesis and Applications)

► Show Figures

Figure 1

30 pages, 5563 KiB

Open AccessReview

Advances in Ceramic–Carbonate Dual-Phase Membrane Reactors for Direct CO₂ Separation and Utilization

by Xue Kang, Qing Yang, Jiajie Ma, Qiangchao Sun and Hongwei Cheng

Membranes 2025, 15(2), 53; https://doi.org/10.3390/membranes15020053 - 6 Feb 2025

Viewed by 1238

Abstract

Excessive (carbon dioxide) CO₂ emissions are a primary factor contributing to climate change. As one of the crucial technologies for alleviating CO₂ emissions, carbon capture and utilization (CCU) technology has attracted considerable global attention. Technologies for capturing CO₂ in extreme [...] Read more.

Excessive (carbon dioxide) CO₂ emissions are a primary factor contributing to climate change. As one of the crucial technologies for alleviating CO₂ emissions, carbon capture and utilization (CCU) technology has attracted considerable global attention. Technologies for capturing CO₂ in extreme circumstances are indispensable for regulating CO₂ levels in industrial processes. The unique separation characteristics of the ceramic–carbonate dual-phase (CCDP) membranes are increasingly employed for CO₂ separation at high temperatures due to their outstanding chemical, thermal durability, and mechanical strength. This paper presents an overview of CO₂ capture approaches and materials. It also elaborates on the research progress of three types of CCDP membranes with distinct permeation mechanisms, concentrating on their principles, materials, and structures. Additionally, several typical membrane reactors, such as the dry reforming of methane (DRM) and reverse water–gas shift (RWGS), are discussed to demonstrate how captured CO₂ can function as a soft oxidant, converting feedstocks into valuable products through oxidation pathways designed within a single reactor. Finally, the future challenges and prospects of high-temperature CCDP membrane technologies and their related reactors are proposed. Full article

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

► Show Figures

Figure 1

16 pages, 3495 KiB

Open AccessArticle

Phosphate Tailings and Clay-Based Ceramic Membranes: Tailoring Microstructure and Filtration Properties via Alkali Activation

by Amine El Azizi, Hanane El Harouachi, Dounia Ahoudi, Soundouss Maliki, Mohammed Mansori and Mohamed Loutou

Membranes 2025, 15(2), 52; https://doi.org/10.3390/membranes15020052 - 5 Feb 2025

Viewed by 946

Abstract

The increasing demand for sustainable water treatment technologies has driven the development of advanced ceramic membranes with tailored properties. This study explores the fabrication of ceramic membranes using phosphate tailings and clay lithologies as alternative raw materials, offering a sustainable and cost-effective approach [...] Read more.

The increasing demand for sustainable water treatment technologies has driven the development of advanced ceramic membranes with tailored properties. This study explores the fabrication of ceramic membranes using phosphate tailings and clay lithologies as alternative raw materials, offering a sustainable and cost-effective approach to membrane production. The focus is on tailoring membrane porosity through the deposition of multilayered alkali-activated coatings, leveraging geopolymerization chemistry to enhance structural and functional performance. The manufactured ceramic membranes were investigated using X-ray fluorescence spectrometry, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and a filtration test pilot. Results revealed the suitability of both phosphate tailing and the clay for membrane processing, while alkali activation effectively modulates the membrane’s porosity (from 1–10 μm to 0.1–1 μm) and mechanical strength (up to 20 MPa). Both tailored and untailored membranes demonstrated favorable performance. Key findings include the formation of a well-interconnected pore network and improved compressive strength, which resulted in sustained filtration performance under challenging operational conditions. The membranes demonstrated their suitability for environmental and industrial applications by achieving high efficiency in industrial effluent filtration tests. Full article

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

► Show Figures

Figure 1

29 pages, 6175 KiB

Open AccessReview

Endotoxin-Retentive Filters for the Online Preparation of Ultrapure Dialysis Fluid and Non-Pyrogenic Substitution Fluid: A Critical Review and Reference Guide

by Gerardo Catapano, Giuseppe Morrone, Lilio Hu, Gionata Fragomeni and Andrea Buscaroli

Membranes 2025, 15(2), 51; https://doi.org/10.3390/membranes15020051 - 5 Feb 2025

Viewed by 1085

Abstract

Poor water treatments and concentrates to prepare dialysis fluids favor bacterial growth-producing pyrogens (e.g., endotoxins) that may cross hemodialysis, particularly high-flux, membranes. This puts hemodialysis patients at risk of acute bacteremia, pyrogenic reactions, long-term complications, loss of residual renal function, and poor nutritional [...] Read more.

Poor water treatments and concentrates to prepare dialysis fluids favor bacterial growth-producing pyrogens (e.g., endotoxins) that may cross hemodialysis, particularly high-flux, membranes. This puts hemodialysis patients at risk of acute bacteremia, pyrogenic reactions, long-term complications, loss of residual renal function, and poor nutritional status. Consequently, regulatory bodies worldwide recommend using ultrapure dialysis fluid for routine hemodialysis. Requests are also growing for the online production of sterile non-pyrogenic substitution fluid from ultrapure dialysis fluid. This way, large volumes of infusion solution may be safely and economically produced, enabling more end-stage kidney disease patients to benefit from the greater capacity of hemodiafiltration to remove toxins than purely diffusive hemodialysis treatment. Ultrapure dialysis and substitution fluids are often produced upstream from hemodialyzers by online filtration of standard dialysis fluid through cascades of bacteria- and endotoxin-retentive filters (ETRFs). Commercial ETRFs differ for membranes, operation, performance, duration and maintenance protocols, connection to a dialysis machine, disinfection procedures, and replacement schedule. Although suboptimal ETRF choice may increase treatment costs, the difficulty in gathering comparative information on commercial ETRFs complicates their selection. To aid dialysis centers in selecting the most convenient and suitable ETRF for their needs, herein, relevant characteristics of commercial ETRFs are reported and critically reviewed for a quick yet effective comparison. Full article

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

► Show Figures

Figure 1

23 pages, 5879 KiB

Open AccessArticle

The Development and Analysis of a Preliminary Electrodialysis Process for the Purification of Complex Lithium Solutions for the Production of Li₂CO₃ and LiOH

by Alonso González, Geovanna Choque, Mario Grágeda and Svetlana Ushak

Membranes 2025, 15(2), 50; https://doi.org/10.3390/membranes15020050 - 5 Feb 2025

Viewed by 1467

Abstract

Direct lithium extraction (DLE) is emerging as a promising alternative to brine extraction although it requires further processing to obtain high-quality products suitable for various applications. This study focused on developing a process to concentrate and purify complex LiCl solutions obtained through direct [...] Read more.

Direct lithium extraction (DLE) is emerging as a promising alternative to brine extraction although it requires further processing to obtain high-quality products suitable for various applications. This study focused on developing a process to concentrate and purify complex LiCl solutions obtained through direct lithium extraction (DLE). Two different chemical compositions of complex LiCl solutions were used, dividing the study into three stages. In the first part, lithium was concentrated to 1% by mass by evaporation. In the second, electrodialysis was used to alkalinize the LiCl solution and remove magnesium and calcium impurities under different current densities. The best results obtained were magnesium and calcium removals of 99.8% and 98.0%, respectively, and lithium recoveries of 99% and 96%. In the third stage, the selectivity of two different commercial cationic membranes (Nafion 117 and Neosepta CMS) was evaluated to separate Li⁺, K⁺, and Na⁺ cations under different current densities and volumetric flow rates. The Neosepta CMS membrane demonstrated higher lithium recovery. This study evaluated the quality of the purified lithium-rich solution and its potential use both in the production of Li₂CO₃ as well as in the electrochemical production of LiOH. Full article

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

► Show Figures

Figure 1

24 pages, 7985 KiB

Open AccessArticle

CO₂ and O₂ Separation Dual-Phase Membranes for Diesel Heavy-Duty Vehicles Applications

by Eirini Zagoraiou, Luca Cappai, Anastasia Maria Moschovi, Gabriele Mulas and Iakovos Yakoumis

Membranes 2025, 15(2), 49; https://doi.org/10.3390/membranes15020049 - 5 Feb 2025

Viewed by 794

Abstract

Diesel-engine Heavy-Duty Vehicle (HDV) exhaust gas mixture contains pollutants including unburned hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matter. A catalyst-based emission control system is commonly used to eliminate the above pollutants. However, the excess of oxygen that exists in the exhaust gasses [...] Read more.

Diesel-engine Heavy-Duty Vehicle (HDV) exhaust gas mixture contains pollutants including unburned hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matter. A catalyst-based emission control system is commonly used to eliminate the above pollutants. However, the excess of oxygen that exists in the exhaust gasses of diesel engines hinders the efficient and selective reduction of nitrogen oxides over conventional catalytic converters. The AdBlue^® solution, which is currently used to eliminate nitrogen oxides, is based on ammonia. The latter is toxic in high concentrations. The aim of this work is to develop an Oxygen Reduction System (ORS) to remove oxygen from the exhaust gas of diesel engines, allowing the successful catalytic reduction of nitrogen oxides on a reduction catalyst without the need for ammonia. The ORS device consists of dense composite dual-phase membranes that allow the permeation of oxygen and carbon dioxide. Even though the oxygen concentration gradient across the membranes favors oxygen spontaneous diffusion from the atmosphere to the exhaust gas, the carbonate ion-based technology proposed herein utilizes the big difference in the concentration of carbon dioxide across the membrane to remove oxygen without any power consumption requirement. The results of this study are promising for the application of O₂ reduction in diesel HDVs. Full article

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

► Show Figures

Figure 1

16 pages, 2615 KiB

Open AccessArticle

Environment-Oriented Assessment of Hybrid Methods for Separation of N-Propanol–Water Mixtures: Combination of Distillation and Hydrophilic Pervaporation Processes

by Huyen Trang Do Thi and Andras Jozsef Toth

Membranes 2025, 15(2), 48; https://doi.org/10.3390/membranes15020048 - 5 Feb 2025

Viewed by 1014

Abstract

This study presents a novel approach to the dehydration of n-propanol using three hybrid methods—D + HPV, D + HPV + D, and D + HPV + D with heat integration—each combining distillation (D) and hydrophilic pervaporation (HPV) without the use of additional [...] Read more.

This study presents a novel approach to the dehydration of n-propanol using three hybrid methods—D + HPV, D + HPV + D, and D + HPV + D with heat integration—each combining distillation (D) and hydrophilic pervaporation (HPV) without the use of additional solvent agents, as in the most common separation method, extractive distillation. The optimization was performed using a ChemCAD process simulator, targeting 99.9 wt% purity for n-propanol and water. This is the first research to provide a comprehensive cost estimation and carbon footprint analysis for such configurations. Results show the D + HPV + D + HI method provides the best balance of energy efficiency, environmental sustainability, and economic feasibility. It reduced heat duties by 18.5% compared to D + HPV + D, achieved similar CO₂ emissions to D + HPV with better energy efficiency, and lowered the total annual cost by 37.9% compared to D + HPV. The findings establish D + HPV + D + HI as a promising technology for sustainable and cost-effective n-propanol dehydration. Full article

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

► Show Figures

Figure 1

13 pages, 2594 KiB

Open AccessArticle

Removal of Microplastics from Laundry Wastewater Using Coagulation and Membrane Combination: A Laboratory-Scale Study

by Thi Trang Luu, Dai Quyet Truong, Van Nam Nguyen, Sanghyun Jeong, Thi Thu Trang Nguyen, Van Manh Do, Saravanamuthu Vigneswaran and Tien Vinh Nguyen

Membranes 2025, 15(2), 47; https://doi.org/10.3390/membranes15020047 - 4 Feb 2025

Viewed by 947

Abstract

Microplastic (MP) pollution has recently emerged as a critical global environmental issue. Laundry wastewater is a significant contributor to MP pollution, containing high concentrations of MPs. Although coagulation has recently been widely applied to remove MPs from such wastewater, its efficiency remains poor, [...] Read more.

Microplastic (MP) pollution has recently emerged as a critical global environmental issue. Laundry wastewater is a significant contributor to MP pollution, containing high concentrations of MPs. Although coagulation has recently been widely applied to remove MPs from such wastewater, its efficiency remains poor, and the removal mechanisms are not yet fully elucidated. In this study, the occurrence and characteristics of MPs in raw domestic laundry wastewater were investigated. The coagulation process was combined with ultrafiltration (UF) membrane filtration to enhance MP removal. The results showed that the concentrations of MPs in laundry wastewater ranged from 9000 to 11,000 particles/L, with fibrous particles constituting the majority (42.6%) and polyester accounting for 68.2% of detected MPs. Using aluminium chloride and ferric chloride as coagulants, maximum removal efficiencies of 91.7 and 98.3% were achieved, respectively. Mechanistic analysis revealed that charge neutralization played a dominant role during coagulation. Fourier transform infrared spectroscopy further demonstrated the formation of new functional groups, substituted benzene rings, and the presence of Fe-O and Al-O bonds, indicating the interaction between MPs and coagulants. Furthermore, the UF membrane was used to remove fibrous MPs and MPs with low densities. These MPs had not been removed with pre-coagulation. The removal efficiency of these MPs reached 96 ± 2%, reducing their concentration to only 60 particles/L in the UF permeate. These findings highlight the synergistic potential of coagulation and UF membrane filtration for effective MP removal and provide a valuable reference for advancing wastewater treatment technologies targeting MP pollution. Full article

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

► Show Figures

Figure 1

16 pages, 5006 KiB

Open AccessArticle

Insights on Hydrogen Bond Network of Water in Phospholipid Membranes: An Infrared Study at Varying Hydration

by Valeria Conti Nibali, Caterina Branca, Ulderico Wanderlingh, Rosaria Verduci, Elisa Bonaccorso, Andrea Ciccolo and Giovanna D’Angelo

Membranes 2025, 15(2), 46; https://doi.org/10.3390/membranes15020046 - 4 Feb 2025

Viewed by 931

Abstract

Water in membrane interphases is vital for cellular biological functions, but despite its importance, the structure and function of biological water remain elusive. Here, by studying the OH stretching mode in partially hydrated lipid multilayers by FTIR measurements, relevant information on the water [...] Read more.

Water in membrane interphases is vital for cellular biological functions, but despite its importance, the structure and function of biological water remain elusive. Here, by studying the OH stretching mode in partially hydrated lipid multilayers by FTIR measurements, relevant information on the water structure near the surface with lipid membranes has been gathered. The water hydrogen bond network is highly perturbed in the first layers that are in contact with the lipid membrane, exhibiting strong deviations from tetrahedral symmetry and a significant number of defects, such as isolated water molecules and a large number of hydrogen-bonded water dimers in the interphase region. These findings support the hypothesis that water chains form in phospholipid membranes, and are involved in the proton transfer across lipid bilayers by phosphate groups of opposing lipids. Furthermore, we have determined that even at very low hydration levels, a small amount of water is embedded within the confined spaces of the hydrocarbon region of phospholipid bilayers, which could potentially contribute to the structural stability of the lipid membrane. Full article

(This article belongs to the Special Issue Composition and Biophysical Properties of Lipid Membranes)

► Show Figures

Figure 1

27 pages, 30466 KiB

Open AccessArticle

Electrospun Membranes Loaded with Melanin Derived from Pecan Nutshell (Carya illinoinensis) Residues for Skin-Care Applications

by Michell García-García, Jesús Salvador Jaime-Ferrer, Fernanda Nayeli Medrano-Lango, Elizabeth Quintana-Rodríguez, Tonatiu Campos-García, Erika Rodríguez-Sevilla and Domancar Orona-Tamayo

Membranes 2025, 15(2), 44; https://doi.org/10.3390/membranes15020044 - 3 Feb 2025

Viewed by 1711

Abstract

This study investigates the incorporation of melanin extracted from pecan nutshell residues into a polyacrylonitrile (PAN) matrix during the electrospinning of microfiber membranes. Melanin concentrations of 0.5, 2.0, and 5.0% w/w were incorporated to enhance the physicochemical and biological properties of [...] Read more.

This study investigates the incorporation of melanin extracted from pecan nutshell residues into a polyacrylonitrile (PAN) matrix during the electrospinning of microfiber membranes. Melanin concentrations of 0.5, 2.0, and 5.0% w/w were incorporated to enhance the physicochemical and biological properties of the fibers. The melanin-loaded PAN fibers exhibited significant antioxidant activity against DPPH and ABTS radicals, with scavenging rates ranging from 46.58% to 62.77% and 41.02% to 82.36%, respectively, while unmodified PAN fibers showed no activity. Furthermore, the melanin-loaded membranes demonstrated antimicrobial effects. The membranes also exhibited an important enzyme inhibition activity against collagenase (37%), hyaluronidase (22%), tyrosinase (36%), and elastase (33%). Molecular docking studies reveal different potential amino acids of the active sites of aging enzymes that interact strongly with melanin pigment, particularly collagenase, followed by hyaluronidase, tyrosinase, and elastase. These results suggest that the novel melanin-loaded PAN membranes possess promising bioactive properties with potential applications in different skin-care applications. Full article

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

► Show Figures

Figure 1

28 pages, 1935 KiB

Open AccessReview

Use of Membrane Techniques for Removal and Recovery of Nutrients from Liquid Fraction of Anaerobic Digestate

by Magdalena Zielińska and Katarzyna Bułkowska

Membranes 2025, 15(2), 45; https://doi.org/10.3390/membranes15020045 - 2 Feb 2025

Cited by 1 | Viewed by 1538

Abstract

This review focuses on the use of membrane techniques to recover nutrients from the liquid fraction of digestate (LFD) and emphasizes their role in promoting the principles of the circular economy. A range of membrane separation processes are examined, including microfiltration (MF), ultrafiltration [...] Read more.

This review focuses on the use of membrane techniques to recover nutrients from the liquid fraction of digestate (LFD) and emphasizes their role in promoting the principles of the circular economy. A range of membrane separation processes are examined, including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), membrane distillation (MD) and new tools and techniques such as membrane contactors (MCs) with gas-permeable membranes (GPMs) and electrodialysis (ED). Key aspects that are analyzed include the nutrient concentration efficiency, integration with biological processes and strategies to mitigate challenges such as fouling, high energy requirements and scalability. In addition, innovative hybrid systems and pretreatment techniques are examined for their potential to improve the recovery rates and sustainability. The review also addresses the economic and technical barriers to the full-scale application of these technologies and identifies future research directions, such as improving the membrane materials and reducing the energy consumption. The comprehensive assessment of these processes highlights their contribution to sustainable nutrient management and bio-based fertilizer production. Full article

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

► Show Figures

Figure 1

14 pages, 2658 KiB

Open AccessArticle

Integrated Purification Systems for the Removal of Disinfectants from Wastewater

by Aleksandra Klimonda and Izabela Kowalska

Membranes 2025, 15(2), 43; https://doi.org/10.3390/membranes15020043 - 2 Feb 2025

Viewed by 711

Abstract

The efficiency of integrated treatment systems for wastewater generated during the washing of disinfectant production lines was investigated. The high organic load (COD 2000 mg/L, TOC 850 mg/L) and 300 mg/L of toxic benzalkonium chloride (BAC) make wastewater an environmental hazard that requires [...] Read more.

The efficiency of integrated treatment systems for wastewater generated during the washing of disinfectant production lines was investigated. The high organic load (COD 2000 mg/L, TOC 850 mg/L) and 300 mg/L of toxic benzalkonium chloride (BAC) make wastewater an environmental hazard that requires advanced treatment. Initial tests on model BAC solutions (in concentrations corresponding to those found in wastewater), using nanofiltration and ultrafiltration membranes, resulted in up to 70% retention of BAC. To enhance purification, ion exchange and adsorption were introduced as post-membrane treatment steps. In the second part of the investigation, membrane modules characterized by the best separation properties were integrated together with macroporous cation-exchange resin and activated carbon into the purification system to treat wastewater. The research carried out showed that the purification of multicomponent wastewater is a complex task. Significantly lower BAC removal (30%) was achieved in membrane processes compared to the model solutions treatment. In integrated systems, the BAC concentration was reduced to 100 mg/L, TOC to 200 mg/L, and COD to 120 mg/L. Full article

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

► Show Figures

Figure 1

19 pages, 5898 KiB

Open AccessArticle

Preparation of Am-MSN/PVDF Mixed Matrix Membranes for Enhanced Removal of Reactive Black 5

by Jihao Zuo, Mengkang Lu, Jinting Cai, Ruopeng Lan, Xinjuan Zeng and Cailong Zhou

Membranes 2025, 15(2), 42; https://doi.org/10.3390/membranes15020042 - 1 Feb 2025

Viewed by 685

Abstract

The discharge of large volumes of textile dyeing wastewater, characterized by poor biodegradability and high toxicity, poses severe threats to the environment. In this study, polyvinylidene difluoride (PVDF) membranes were prepared using the nonsolvent-induced phase separation (NIPS) method, with porous amino-functionalized mesoporous silica [...] Read more.

The discharge of large volumes of textile dyeing wastewater, characterized by poor biodegradability and high toxicity, poses severe threats to the environment. In this study, polyvinylidene difluoride (PVDF) membranes were prepared using the nonsolvent-induced phase separation (NIPS) method, with porous amino-functionalized mesoporous silica nanoparticles (Am-MSNs) mixed into the casting solution to fabricate the Am-MSN/PVDF mixed matrix membranes. By varying the amount of Am-MSNs added, the microstructure and overall performance of the membranes were comprehensively analyzed. The results demonstrated that the addition of Am-MSNs significantly enhanced the hydrophilicity of the membranes. The high specific surface area and amino groups of Am-MSNs facilitated interactions with dye molecules, such as Reactive Black 5 (RB5), through hydrogen bonding, electrostatic attraction, and physical adsorption, resulting in a marked improvement in RB5 rejection rates. Static adsorption tests further validated the superior adsorption capacity of the Am-MSN/PVDF mixed matrix membranes for RB5. Additionally, the nanoscale mesoporous structure of Am-MSNs enhanced the mechanical strength of the membranes. The synergistic effects of the mesoporous structure and amino groups significantly increased the efficiency and stability of the Am-MSN/PVDF mixed matrix membranes in dye removal applications, providing an effective and sustainable solution for the treatment of dye-contaminated wastewater. Full article

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

► Show Figures

Figure 1

13 pages, 4564 KiB

Open AccessArticle

Silica-Nanocoated Membranes with Enhanced Stability and Antifouling Performance for Oil-Water Emulsion Separation

by Mengfan Zhu, Chengqian Huang and Yu Mao

Membranes 2025, 15(2), 41; https://doi.org/10.3390/membranes15020041 - 1 Feb 2025

Cited by 1 | Viewed by 655

Abstract

Despite the potential of glass fiber (GF) membranes for oil-water emulsion separations, efficient surface modification methods to enhance fouling resistance while preserving membrane performance and stability remain lacking. We report a silica nanocoating method to modify GF membranes through a vapor deposition method. [...] Read more.

Despite the potential of glass fiber (GF) membranes for oil-water emulsion separations, efficient surface modification methods to enhance fouling resistance while preserving membrane performance and stability remain lacking. We report a silica nanocoating method to modify GF membranes through a vapor deposition method. The high smoothness (<1 nm r.m.s.) and high conformality of the vapor-deposited silica nanocoatings enabled the preservation of membrane microstructure and permeability, which, combined with the enhanced surface hydrophilicity, led to an oil rejection rate exceeding 99% and more than a 40% improvement in permeate flux in oil-water emulsion separations. Furthermore, the silica nanocoatings provided the membranes with excellent wet strength and stability against organic solvents, strong acids, oxidants, boiling, and sonication. The silica-nanocoated membrane demonstrated enhanced fouling resistance, achieving flux recovery higher than 75% during repeated oil-water emulsion separations and bovine serum albumin and humic acid fouling tests. Full article

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

► Show Figures

Figure 1

12 pages, 1356 KiB

Open AccessArticle

Conformation and Membrane Topology of the N-Terminal Ectodomain of Influenza A M2 Protein

by Kyra C. Roeke and Kathleen P. Howard

Membranes 2025, 15(2), 40; https://doi.org/10.3390/membranes15020040 - 1 Feb 2025

Viewed by 718

Abstract

The N-terminal ectodomain of the influenza A M2 protein is a target for universal influenza vaccine development and novel antiviral strategies. Despite the significance of this domain, it is poorly understood and most structural studies of the M2 protein have disregarded the N-terminal [...] Read more.

The N-terminal ectodomain of the influenza A M2 protein is a target for universal influenza vaccine development and novel antiviral strategies. Despite the significance of this domain, it is poorly understood and most structural studies of the M2 protein have disregarded the N-terminal ectodomain in their analyses. Here, we report conformational properties and describe insights into the membrane topology of sites along the N-terminal ectodomain. Full-length M2 protein is embedded in lipid bilayer nanodiscs and studied using site-directed spin labeling electron paramagnetic resonance spectroscopy. Results are consistent with a turn in the middle of the ectodomain that changes in proximity to the membrane surface upon the addition of cholesterol or the antiviral drug rimantadine. Similarly to other domains of M2 protein, lineshape analysis suggests that the N-terminal ectodomain can adopt multiple conformations. Full article

(This article belongs to the Section Biological Membranes)

► Show Figures

Figure 1

16 pages, 4657 KiB

Open AccessArticle

Electrospun Collagen-Coated Nanofiber Membranes Functionalized with Silver Nanoparticles for Advanced Wound Healing Applications

by Martin Iurilli, Davide Porrelli, Gianluca Turco, Cristina Lagatolla, Alvise Camurri Piloni, Barbara Medagli, Vanessa Nicolin and Giovanni Papa

Membranes 2025, 15(2), 39; https://doi.org/10.3390/membranes15020039 - 1 Feb 2025

Viewed by 1234

Abstract

Complex wounds pose a significant healthcare challenge due to their susceptibility to infections and delayed healing. This study focuses on developing electrospun polycaprolactone (PCL) nanofiber membranes coated with Type I collagen derived from bovine skin and functionalized with silver nanoparticles (AgNPs) to address [...] Read more.

Complex wounds pose a significant healthcare challenge due to their susceptibility to infections and delayed healing. This study focuses on developing electrospun polycaprolactone (PCL) nanofiber membranes coated with Type I collagen derived from bovine skin and functionalized with silver nanoparticles (AgNPs) to address these issues. The collagen coating enhances biocompatibility, while AgNPs synthesized through chemical reduction with sodium citrate provide broad-spectrum antimicrobial properties. The physical properties of the membranes were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results showed the formation of nanofibers without defects and the uniform distribution of AgNPs. A swelling test and contact angle measurements confirmed that the membranes provided an optimal environment for wound healing. In vitro biological assays with murine 3T3 fibroblasts revealed statistically significant (p ≤ 0.05) differences in cell viability among the membranes at 24 h (p = 0.0002) and 72 h (p = 0.022), demonstrating the biocompatibility of collagen-coated membranes and the minimal cytotoxicity of AgNPs. Antibacterial efficacy was evaluated against Staphylococcus aureus (SA), Pseudomonas aeruginosa (PA), and Vancomycin-resistant Enterococcus (VRE), with the significant inhibition of biofilm formation observed for VRE (p = 0.006). Overall, this novel combination of collagen-coated electrospun PCL nanofibers with AgNPs offers a promising strategy for advanced wound dressings, providing antimicrobial benefits. Future in vivo studies are warranted to further validate its clinical and regenerative potential. Full article

(This article belongs to the Special Issue Recent Progress in Electrospun Membranes)

► Show Figures

Figure 1

20 pages, 8497 KiB

Open AccessArticle

Synthesis and Characterization of Cellulose Acetate—HBA/Poly Sulfone Blend for Water Treatment Applications

by Lamai Alsulaiman, Abir S. Abdel-Naby, Salha Alharthi, Bushra ALabdullatif, Abeer Al-Dossary, Wafa Al-Mughrabi and Yanallah Alqarni

Membranes 2025, 15(2), 38; https://doi.org/10.3390/membranes15020038 - 26 Jan 2025

Viewed by 1040

Abstract

Cellulose acetate (CA) was chemically modified with p–hydrazinobenzoic acid (HBA) for the fabrication of a CA–HBA polymeric membrane. The CA–HBA was characterized using NMR, UV-Vis, and EDX/SEM techniques. CA–HBA exhibited high hydrophilicity, as it included carboxylic groups as well as the hydroxyl group [...] Read more.

Cellulose acetate (CA) was chemically modified with p–hydrazinobenzoic acid (HBA) for the fabrication of a CA–HBA polymeric membrane. The CA–HBA was characterized using NMR, UV-Vis, and EDX/SEM techniques. CA–HBA exhibited high hydrophilicity, as it included carboxylic groups as well as the hydroxyl group of the CA glycosidic ring. The HBA moieties increased the hydrophilicity and the number of active sites inside the CA polymeric matrix, but they did not improve the thermal stability of the polymer, as shown by the thermogravimetry (TGA). Polysulfone (PSF) was blended with CA-HBA in various compositions to produce highly thermal and effective membranes for water treatment applications. The fabricated membranes (CA–HBA/PSF) (5:95) (10:90) (15:85) were found to exhibit high thermal stabilities. The CA–HBA/PSF 15:85 membrane exhibited the highest efficiency towards the removal of Cu (II) ions, while the 5:95 membrane exhibited the highest salt rejection (89%). Full article

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

► Show Figures

Graphical abstract

20 pages, 8145 KiB

Open AccessArticle

Assessing a Multilayered Hydrophilic–Electrocatalytic Forward Osmosis Membrane for Ammonia Electro-Oxidation

by Perla Cruz-Tato, Laura I. Penabad, César Lasalde, Alondra S. Rodríguez-Rolón and Eduardo Nicolau

Membranes 2025, 15(2), 37; https://doi.org/10.3390/membranes15020037 - 22 Jan 2025

Viewed by 1307

Abstract

Over the years, the ammonia concentration in water streams and the environment is increasing at an alarming rate. Many membrane-based processes have been studied to alleviate this concern via adsorption and filtration. On the other hand, ammonia electro-oxidation is an approach of particular [...] Read more.

Over the years, the ammonia concentration in water streams and the environment is increasing at an alarming rate. Many membrane-based processes have been studied to alleviate this concern via adsorption and filtration. On the other hand, ammonia electro-oxidation is an approach of particular interest owing to its energetic and environmental benefits. Thus, a plausible alternative to combine these two paths is by using an electroconductive membrane (ECM) to complete the ammonia oxidation reaction (AOR). This combination of processes has been studied very limitedly, and it can be an area for development. Herein, we developed a multilayered membrane with hydrophilic and electrocatalytic properties capable of completing the AOR. The porosity of carbon black (CB) particles was embedded in the polymeric support (CBES) and the active side was composed of a triple layer consisting of polyamide/CB/Pt nanoparticles (PA:CB:Pt). The CBES increased the membrane porosity, changed the pores morphology, and enhanced water permeability and electroconductivity. The deposition of each layer was monitored and corroborated physically, chemically, and electrochemically. The final membrane CBES:PA:VXC:Pt reached higher water flux than its PSF counterpart (3.9 ± 0.3 LMH), had a hydrophilic surface (water contact angle: 19.8 ± 0.4°), and achieved the AOR at −0.3 V vs. Ag/AgCl. Our results suggest that ECMs with conductive material in both membrane layers enhanced their electrical properties. Moreover, this study is proof-of-concept that the AOR can be succeeded by a polymeric FO-ECMs. Full article

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

► Show Figures

Figure 1

Journal Menu

Journal Browser

Membranes, Volume 15, Issue 2 (February 2025) – 28 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI