Membranes

20 pages, 2876 KiB

Open AccessEditor’s ChoiceArticle

Nitrate Removal by Donnan Dialysis and Anion-Exchange Membrane Bioreactor Using Upcycled End-of-Life Reverse Osmosis Membranes

by Amaia Lejarazu-Larrañaga, Juan M. Ortiz, Serena Molina, Sylwin Pawlowski, Claudia F. Galinha, Vanessa Otero, Eloy García-Calvo, Svetlozar Velizarov and João G. Crespo

Membranes 2022, 12(2), 101; https://doi.org/10.3390/membranes12020101 - 18 Jan 2022

Cited by 18 | Viewed by 4997

Abstract

This work explores the application of Reverse Osmosis (RO) upcycled membranes, as Anion Exchange Membranes (AEMs) in Donnan Dialysis (DD) and related processes, such as the Ion Exchange Membrane Bioreactor (IEMB), for the removal of nitrate from contaminated water, to meet drinking water [...] Read more.

This work explores the application of Reverse Osmosis (RO) upcycled membranes, as Anion Exchange Membranes (AEMs) in Donnan Dialysis (DD) and related processes, such as the Ion Exchange Membrane Bioreactor (IEMB), for the removal of nitrate from contaminated water, to meet drinking water standards. Such upcycled membranes might be manufactured at a lower price than commercial AEMs, while their utilization reinforces the commitment to a circular economy transition. In an effort to gain a better understanding of such AEMs, confocal µ-Raman spectroscopy was employed, to assess the distribution of the ion-exchange sites through the thickness of the prepared membranes, and 2D fluorescence spectroscopy, to evaluate alterations in the membranes caused by fouling and chemical cleaning The best performing membrane reached a 56% average nitrate removal within 24 h in the DD and IEMB systems, with the latter furthermore allowing for simultaneous elimination of the pollutant by biological denitrification, thus avoiding its discharge into the environment. Overall, this work validates the technical feasibility of using RO upcycled AEMs in DD and IEMB processes for nitrate removal. This membrane recycling concept might also find applications for the removal and/or recovery of other target negatively charged species. Full article

(This article belongs to the Special Issue State-of-the-Art Membrane Science and Technology in the Iberian Peninsula 2021-2022)

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12 pages, 1934 KiB

Open AccessEditor’s ChoiceArticle

Phosphorus Recovery by Adsorption from the Membrane Permeate of an Anaerobic Membrane Bioreactor Digesting Waste-Activated Sludge

by Akira Hafuka and Katsuki Kimura

Membranes 2022, 12(1), 99; https://doi.org/10.3390/membranes12010099 - 17 Jan 2022

Cited by 2 | Viewed by 3223

Abstract

The recovery of phosphorus (P) from waste activated sludge (WAS) is a promising approach for sustainable resource management. During the anaerobic digestion of WAS, orthophosphate is released, and this P species is favorable for adsorption recovery. In the present study, an anerobic membrane [...] Read more.

The recovery of phosphorus (P) from waste activated sludge (WAS) is a promising approach for sustainable resource management. During the anaerobic digestion of WAS, orthophosphate is released, and this P species is favorable for adsorption recovery. In the present study, an anerobic membrane bioreactor (AnMBR) with a P-adsorption column was developed to generate biogas from WAS and to recover P from membrane permeate simultaneously. The effects of the hydraulic retention time (HRT) and solid retention time (SRT) of the AnMBR on P solubilization were investigated. As a result, the maximum P solubilization was 21% when the HRT and SRT were 45 days and 100 days, respectively. Orthophosphate in the membrane permeate was adsorbed and recovered using a mesoporous material called zirconium sulfate–surfactant micelle mesostructure (ZS) in the column. The adsorbed P could be desorbed from the ZS with a NaOH solution, and P was recovered as a concentrated solution by a factor of 25. When the HRT was 19 days, the biogas yield and biogas production rate were 0.26 L/g-VS_input and 0.123 L/L/d, respectively. The average methane content in the biogas was 80%. The developed membrane-based process may be effective for resource recovery from WAS. Full article

(This article belongs to the Special Issue Honorary Issue for Professor Anthony Fane)

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16 pages, 3304 KiB

Open AccessEditor’s ChoiceArticle

Phosphatidylserine Exposed Lipid Bilayer Models for Understanding Cancer Cell Selectivity of Natural Compounds: A Molecular Dynamics Simulation Study

by Navaneethan Radhakrishnan, Sunil C. Kaul, Renu Wadhwa and Durai Sundar

Membranes 2022, 12(1), 64; https://doi.org/10.3390/membranes12010064 - 1 Jan 2022

Cited by 7 | Viewed by 5805

Abstract

Development of drugs that are selectively toxic to cancer cells and safe to normal cells is crucial in cancer treatment. Evaluation of membrane permeability is a key metric for successful drug development. In this study, we have used in silico molecular models of [...] Read more.

Development of drugs that are selectively toxic to cancer cells and safe to normal cells is crucial in cancer treatment. Evaluation of membrane permeability is a key metric for successful drug development. In this study, we have used in silico molecular models of lipid bilayers to explore the effect of phosphatidylserine (PS) exposure in cancer cells on membrane permeation of natural compounds Withaferin A (Wi-A), Withanone (Wi-N), Caffeic Acid Phenethyl Ester (CAPE) and Artepillin C (ARC). Molecular dynamics simulations were performed to compute permeability coefficients. The results indicated that the exposure of PS in cancer cell membranes facilitated the permeation of Wi-A, Wi-N and CAPE through a cancer cell membrane when compared to a normal cell membrane. In the case of ARC, PS exposure did not have a notable influence on its permeability coefficient. The presented data demonstrated the potential of PS exposure-based models for studying cancer cell selectivity of drugs. Full article

(This article belongs to the Special Issue Modeling and Simulation of Lipid Membranes)

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11 pages, 1760 KiB

Open AccessEditor’s ChoiceArticle

Water Recovery from Bioreactor Mixed Liquors Using Forward Osmosis with Polyelectrolyte Draw Solutions

by Calen R. Raulerson, Sudeep C. Popat and Scott M. Husson

Membranes 2022, 12(1), 61; https://doi.org/10.3390/membranes12010061 - 31 Dec 2021

Cited by 4 | Viewed by 2634

Abstract

This paper reports on the use of forward osmosis (FO) with polyelectrolyte draw solutions to recover water from bioreactor mixed liquors. The work was motivated by the need for new regenerative water purification technologies to enable long-duration space missions. Osmotic membrane bioreactors may [...] Read more.

This paper reports on the use of forward osmosis (FO) with polyelectrolyte draw solutions to recover water from bioreactor mixed liquors. The work was motivated by the need for new regenerative water purification technologies to enable long-duration space missions. Osmotic membrane bioreactors may be an option for water and nutrient recovery in space if they can attain high water flux and reverse solute flux selectivity (RSFS), which quantifies the mass of permeated water per mass of draw solute that has diffused from the draw solution into a bioreactor. Water flux was measured in a direct flow system using wastewater from a municipal wastewater treatment plant and draw solutions prepared with two polyelectrolytes at different concentrations. The direct flow tests displayed a high initial flux (>10 L/m²/h) that decreased rapidly as solids accumulated on the feed side of the membrane. A test with deionized water as the feed revealed a small mass of polyelectrolyte crossover from the draw solution to the feed, yielding an RSFS of 80. Crossflow filtration experiments demonstrated that steady state flux above 2 L/m²·h could be maintained for 70 h following an initial flux decline due to the formation of a foulant cake layer. This study established that FO could be feasible for regenerative water purification from bioreactors. By utilizing a polyelectrolyte draw solute with high RSFS, we expect to overcome the need for draw solute replenishment. This would be a major step towards sustainable operation in long-duration space missions. Full article

(This article belongs to the Special Issue Forward Osmosis - Membrane Developments and Applications)

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28 pages, 2642 KiB

Open AccessEditor’s ChoiceReview

A Review on the Design and Performance of Enzyme-Aided Catalysis of Carbon Dioxide in Membrane, Electrochemical Cell and Photocatalytic Reactors

by Fatin Nasreen Ahmad Rizal Lim, Fauziah Marpani, Victoria Eliz Anak Dilol, Syazana Mohamad Pauzi, Nur Hidayati Othman, Nur Hashimah Alias, Nik Raikhan Nik Him, Jianquan Luo and Norazah Abd Rahman

Membranes 2022, 12(1), 28; https://doi.org/10.3390/membranes12010028 - 27 Dec 2021

Cited by 9 | Viewed by 4729

Abstract

Multi-enzyme cascade catalysis involved three types of dehydrogenase enzymes, namely, formate dehydrogenase (FDH), formaldehyde dehydrogenase (FaldDH), alcohol dehydrogenase (ADH), and an equimolar electron donor, nicotinamide adenine dinucleotide (NADH), assisting the reaction is an interesting pathway to reduce thermodynamically stable molecules of CO₂ [...] Read more.

Multi-enzyme cascade catalysis involved three types of dehydrogenase enzymes, namely, formate dehydrogenase (FDH), formaldehyde dehydrogenase (FaldDH), alcohol dehydrogenase (ADH), and an equimolar electron donor, nicotinamide adenine dinucleotide (NADH), assisting the reaction is an interesting pathway to reduce thermodynamically stable molecules of CO₂ from the atmosphere. The biocatalytic sequence is interesting because it operates under mild reaction conditions (low temperature and pressure) and all the enzymes are highly selective, which allows the reaction to produce three basic chemicals (formic acid, formaldehyde, and methanol) in just one pot. There are various challenges, however, in applying the enzymatic conversion of CO₂, namely, to obtain high productivity, increase reusability of the enzymes and cofactors, and to design a simple, facile, and efficient reactor setup that will sustain the multi-enzymatic cascade catalysis. This review reports on enzyme-aided reactor systems that support the reduction of CO₂ to methanol. Such systems include enzyme membrane reactors, electrochemical cells, and photocatalytic reactor systems. Existing reactor setups are described, product yields and biocatalytic productivities are evaluated, and effective enzyme immobilization methods are discussed. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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14 pages, 2383 KiB

Open AccessEditor’s ChoiceArticle

Optimization of Aquaporin Loading for Performance Enhancement of Aquaporin-Based Biomimetic Thin-Film Composite Membranes

by Yang Zhao, Xuesong Li, Jing Wei, Jaume Torres, Anthony G. Fane, Rong Wang and Chuyang Y. Tang

Membranes 2022, 12(1), 32; https://doi.org/10.3390/membranes12010032 - 27 Dec 2021

Cited by 10 | Viewed by 3827

Abstract

The aquaporin-based biomimetic thin-film composite membrane (ABM-TFC) has demonstrated superior separation performance and achieved successful commercialization. The larger-scale production of the ABM membrane requires an appropriate balance between the performance and manufacturing cost. This study has systematically investigated the effects of proteoliposome concentration, [...] Read more.

The aquaporin-based biomimetic thin-film composite membrane (ABM-TFC) has demonstrated superior separation performance and achieved successful commercialization. The larger-scale production of the ABM membrane requires an appropriate balance between the performance and manufacturing cost. This study has systematically investigated the effects of proteoliposome concentration, protein-to-lipid ratio, as well as the additive on the separation performance of ABM for the purpose of finding the optimal preparation conditions for the ABM from the perspective of industrial production. Although increasing the proteoliposome concentration or protein-to-lipid ratio within a certain range could significantly enhance the water permeability of ABMs by increasing the loading of aquaporins in the selective layer, the enhancement effect was marginal or even compromised beyond an optimal point. Alternatively, adding cholesterol in the proteoliposome could further enhance the water flux of the ABM membrane, with minor effects on the salt rejection. The optimized ABM not only achieved a nearly doubled water flux with unchanged salt rejection compared to the control, but also demonstrated satisfactory filtration stability within a wide range of operation temperatures. This study provides a practical strategy for the optimization of ABM-TFC membranes to fit within the scheme of industrial-scale production. Full article

(This article belongs to the Special Issue Honorary Issue for Professor Anthony Fane)

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14 pages, 3897 KiB

Open AccessEditor’s ChoiceArticle

A Systematic Study of Ammonia Recovery from Anaerobic Digestate Using Membrane-Based Separation

by Fanny Rivera, Raúl Muñoz, Pedro Prádanos, Antonio Hernández and Laura Palacio

Membranes 2022, 12(1), 19; https://doi.org/10.3390/membranes12010019 - 24 Dec 2021

Cited by 19 | Viewed by 4830

Abstract

Ammonia recovery from synthetic and real anaerobic digestates was accomplished using hydrophobic flat sheet membranes operated with H₂SO₄ solutions to convert ammonia into ammonium sulphate. The influence of the membrane material, flow rate (0.007, 0.015, 0.030 and 0.045 m³ [...] Read more.

Ammonia recovery from synthetic and real anaerobic digestates was accomplished using hydrophobic flat sheet membranes operated with H₂SO₄ solutions to convert ammonia into ammonium sulphate. The influence of the membrane material, flow rate (0.007, 0.015, 0.030 and 0.045 m³ h⁻¹) and pH (7.6, 8.9, 10 and 11) of the digestate on ammonia recovery was investigated. The process was carried out with a flat sheet configuration at a temperature of 35 °C and with a 1 M, or 0.005 M, H₂SO₄ solution on the other side of the membrane. Polytetrafluoroethylene membranes with a nominal pore radius of 0.22 µm provided ammonia recoveries from synthetic and real digestates of 84.6% ± 1.0% and 71.6% ± 0.3%, respectively, for a membrane area of 8.6 × 10⁻⁴ m² and a reservoir volume of 0.5 L, in 3.5 h with a 1 M H₂SO₄ solution and a recirculation flow on the feed side of the membrane of 0.030 m³ h⁻¹. NH₃ recovery followed first order kinetics and was faster at higher pHs of the H₂SO₄ solution and recirculation flow rate on the membrane feed side. Fouling resulted in changes in membrane surface morphology and pore size, which were confirmed by Atomic Force Microscopy and Air Displacement Porometry. Full article

(This article belongs to the Special Issue Emerging Membrane Technologies for Environmental Sustainability: Fundamentals and Applications)

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13 pages, 6114 KiB

Open AccessEditor’s ChoiceArticle

Modeling Asymmetry of a Current–Voltage Curve of a Novel MF-4SC/PTMSP Bilayer Membrane

by Anatoly N. Filippov, Natalia A. Kononenko, Natalia V. Loza and Daria A. Petrova

Membranes 2022, 12(1), 22; https://doi.org/10.3390/membranes12010022 - 24 Dec 2021

Cited by 4 | Viewed by 3264

Abstract

A novel bilayer cation-exchange membrane—consisting of a thick layer of a pristine perfluorinated membrane MF-4SC (Russian equivalent of Nafion^®-117) and a thinner layer (1 μm) of the membrane, on a base of glassy polymer of internal microporosity poly(1-trimethylsilyl-1-propyne) (PTMSP)—was prepared and [...] Read more.

A novel bilayer cation-exchange membrane—consisting of a thick layer of a pristine perfluorinated membrane MF-4SC (Russian equivalent of Nafion^®-117) and a thinner layer (1 μm) of the membrane, on a base of glassy polymer of internal microporosity poly(1-trimethylsilyl-1-propyne) (PTMSP)—was prepared and characterized. Using the physicochemical characteristics of one-layer membranes MF-4SC and PTMSP in 0.05 M HCl and NaCl solutions, the asymmetric current–voltage curves (CVC) of the bilayer composite were described with good accuracy up to the overlimiting regime, based on the “fine-porous membrane” model. The MF-4SC/PTMSP bilayer composite has a significant asymmetry of CVC that is promising for using it in electromembrane devices, such as membrane detectors, sensors, and diodes. Full article

(This article belongs to the Special Issue A Commemorative Issue in Honor of Victor Starov: Influence of Surface Forces on Membrane Separations)

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24 pages, 56152 KiB

Open AccessEditor’s ChoiceArticle

Novel Mixed Matrix Membranes Based on Polymer of Intrinsic Microporosity PIM-1 Modified with Metal-Organic Frameworks for Removal of Heavy Metal Ions and Food Dyes by Nanofiltration

by Anna Kuzminova, Mariia Dmitrenko, Andrey Zolotarev, Aleksandra Korniak, Daria Poloneeva, Artem Selyutin, Alexei Emeline, Alexey Yushkin, Andrew Foster, Peter Budd and Sergey Ermakov

Membranes 2022, 12(1), 14; https://doi.org/10.3390/membranes12010014 - 23 Dec 2021

Cited by 24 | Viewed by 5341

Abstract

Nowadays, nanofiltration is widely used for water treatment due to its advantages, such as energy-saving, sustainability, high efficiency, and compact equipment. In the present work, novel nanofiltration membranes based on the polymer of intrinsic microporosity PIM-1 modified by metal-organic frameworks (MOFs)—MIL-140A and MIL-125—were [...] Read more.

Nowadays, nanofiltration is widely used for water treatment due to its advantages, such as energy-saving, sustainability, high efficiency, and compact equipment. In the present work, novel nanofiltration membranes based on the polymer of intrinsic microporosity PIM-1 modified by metal-organic frameworks (MOFs)—MIL-140A and MIL-125—were developed to increase nanofiltration efficiency for the removal of heavy metal ions and dyes. The structural and physicochemical properties of the developed PIM-1 and PIM-1/MOFs membranes were studied by the spectroscopic technique (FTIR), microscopic methods (SEM and AFM), and contact angle measurement. Transport properties of the developed PIM-1 and PIM-1/MOFs membranes were evaluated in the nanofiltration of the model and real mixtures containing food dyes and heavy metal ions. It was found that the introduction of MOFs (MIL-140A and MIL-125) led to an increase in membrane permeability. It was demonstrated that the membranes could be used to remove and concentrate the food dyes and heavy metal ions from model and real mixtures. Full article

(This article belongs to the Collection Polymeric Membranes: Science, Materials and Applications)

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20 pages, 6629 KiB

Open AccessEditor’s ChoiceArticle

Coupling Bulk Phase Separation of Disordered Proteins to Membrane Domain Formation in Molecular Simulations on a Bespoke Compute Fabric

by Julian C. Shillcock, David B. Thomas, Jonathan R. Beaumont, Graeme M. Bragg, Mark L. Vousden and Andrew D. Brown

Membranes 2022, 12(1), 17; https://doi.org/10.3390/membranes12010017 - 23 Dec 2021

Cited by 8 | Viewed by 5019

Abstract

Phospholipid membranes surround the cell and its internal organelles, and their multicomponent nature allows the formation of domains that are important in cellular signalling, the immune system, and bacterial infection. Cytoplasmic compartments are also created by the phase separation of intrinsically disordered proteins [...] Read more.

Phospholipid membranes surround the cell and its internal organelles, and their multicomponent nature allows the formation of domains that are important in cellular signalling, the immune system, and bacterial infection. Cytoplasmic compartments are also created by the phase separation of intrinsically disordered proteins into biomolecular condensates. The ubiquity of lipid membranes and protein condensates raises the question of how three-dimensional droplets might interact with two-dimensional domains, and whether this coupling has physiological or pathological importance. Here, we explore the equilibrium morphologies of a dilute phase of a model disordered protein interacting with an ideal-mixing, two-component lipid membrane using coarse-grained molecular simulations. We find that the proteins can wet the membrane with and without domain formation, and form phase separated droplets bound to membrane domains. Results from much larger simulations performed on a novel non-von-Neumann compute architecture called POETS, which greatly accelerates their execution compared to conventional hardware, confirm the observations. Reducing the wall clock time for such simulations requires new architectures and computational techniques. We demonstrate here an inter-disciplinary approach that uses real-world biophysical questions to drive the development of new computing hardware and simulation algorithms. Full article

(This article belongs to the Special Issue Membrane Biological Function in Health and Disease)

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16 pages, 4231 KiB

Open AccessEditor’s ChoiceArticle

The Preparation of High-Performance and Stable MXene Nanofiltration Membranes with MXene Embedded in the Organic Phase

by Qiang Xue and Kaisong Zhang

Membranes 2022, 12(1), 2; https://doi.org/10.3390/membranes12010002 - 21 Dec 2021

Cited by 18 | Viewed by 4823

Abstract

Nanomaterials embedded in nanofiltration membranes have become a promising modification technology to improve separation performance. As a novel representation of two-dimensional (2D) nanomaterials, MXene has nice features with a strong negative charge and excellent hydrophilicity. Our previous research showed that MXene nanosheets were [...] Read more.

Nanomaterials embedded in nanofiltration membranes have become a promising modification technology to improve separation performance. As a novel representation of two-dimensional (2D) nanomaterials, MXene has nice features with a strong negative charge and excellent hydrophilicity. Our previous research showed that MXene nanosheets were added in the aqueous phase, which enhanced the permeselectivity of the membrane and achieved persistent desalination performance. Embedding the nanomaterials into the polyamide layer through the organic phase can locate the nanomaterials on the upper surface of the polyamide layer, and also prevent the water layer around the hydrophilic nanomaterials from hindering the interfacial polymerization reaction. We supposed that if MXene nanosheets were added in the organic phase, MXene nanosheets would have more negative contact sites on the membrane surface and the crosslinking degree would increase. In this study, MXene were dispersed in the organic phase with the help of ultrasound, then MXene nanocomposite nanofiltration membranes were achieved. The prepared MXene membranes obtained enhanced negative charge and lower effective pore size. In the 28-day persistent desalination test, the Na₂SO₄ rejection of MXene membrane could reach 98.6%, which showed higher rejection compared with MXene embedded in aqueous phase. The results of a long-time water immersion test showed that MXene membrane could still maintain a high salt rejection after being soaked in water for up to 105 days, which indicated MXene on the membrane surface was stable. Besides MXene membrane showed high rejection for high-concentration brine and good mono/divalent salt separation performance in mono/divalent mixed salt solutions. As a part of the study of MXene in nanofiltration membranes, we hoped this research could provide a theoretical guidance for future research in screening different addition methods and different properties. Full article

(This article belongs to the Special Issue Novel Membranes for Desalination)

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23 pages, 4508 KiB

Open AccessEditor’s ChoiceArticle

Enhancing Absorption Performance of CO₂ by Amine Solution through the Spiral Wired Channel in Concentric Circular Membrane Contactors

by Chii-Dong Ho, Hsuan Chang, Guan-Hong Lin and Thiam Leng Chew

Membranes 2022, 12(1), 4; https://doi.org/10.3390/membranes12010004 - 21 Dec 2021

Cited by 5 | Viewed by 3302

Abstract

The CO₂ absorption rate by using a Monoethanolamide (MEA) solution through the spiral wired channel in concentric circular membrane contactors under both concurrent-flow and countercurrent-flow operations was investigated experimentally and theoretically. The one-dimensional mathematical modeling equation developed for predicting the absorption rate [...] Read more.

The CO₂ absorption rate by using a Monoethanolamide (MEA) solution through the spiral wired channel in concentric circular membrane contactors under both concurrent-flow and countercurrent-flow operations was investigated experimentally and theoretically. The one-dimensional mathematical modeling equation developed for predicting the absorption rate and concentration distributions was solved numerically using the fourth Runge–Kutta method under various absorbent flow rate, CO₂ feed flow rate and inlet CO₂ concentration in the gas feed. An economical viewpoint of the spiral wired module was examined by assessing both absorption flux improvement and power consumption increment. Meanwhile, the correlated average Sherwood number to predict the mass-transfer coefficient of the CO₂ absorption mechanisms in a concentric circular membrane contactor with the spiral wired annulus channel is also obtained in a generalized and simplified expression. The theoretical predictions of absorption flux improvement were validated by experimental results in good agreements. The amine solution flowing through the annulus of a concentric circular tube, which was inserted in a tight-fitting spiral wire in a small annular spacing, could enhance the CO₂ absorption flux improvement due to reduction of the concentration polarization effect. A larger concentration polarization coefficient (CPC) was achieved in the countercurrent-flow operations than that in concurrent-flow operations for various operations conditions and spiral-wire pitches. The absorption flux improvement for inserting spiral wire in the concentric circular module could provide the maximum relative increment up to 46.45%. Full article

(This article belongs to the Special Issue Membrane Separation Techniques: Advances, Challenges, and Future Avenues)

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13 pages, 5077 KiB

Open AccessEditor’s ChoiceArticle

Nanofibrous Membrane with Encapsulated Glucose Oxidase for Self-Sustained Antimicrobial Applications

by Fernaldy Leonarta and Cheng-Kang Lee

Membranes 2021, 11(12), 997; https://doi.org/10.3390/membranes11120997 - 20 Dec 2021

Cited by 10 | Viewed by 3806

Abstract

Polyvinyl alcohol (PVA) nanofibrous membrane, consisting of separately encapsulated glucose oxidase (GOx) and glucose (Glu) nanofibers, was prepared via simultaneously electrospinning PVA/GOx and PVA/Glu dopes. The as-prepared pristine membrane could self-sustainably generate hydrogen peroxide (H₂O₂) only in contact with [...] Read more.

Polyvinyl alcohol (PVA) nanofibrous membrane, consisting of separately encapsulated glucose oxidase (GOx) and glucose (Glu) nanofibers, was prepared via simultaneously electrospinning PVA/GOx and PVA/Glu dopes. The as-prepared pristine membrane could self-sustainably generate hydrogen peroxide (H₂O₂) only in contact with an aqueous solution. The H₂O₂ production level was well maintained even after storing the dry membrane at room temperature for 7 days. Cross-linking the membrane via reaction with glutaraldehyde (GA) vapor could not only prevent the nanofibrous membrane from dissolving in water but also prolonged the release of H₂O₂. The sustained release of H₂O₂ from the membrane achieved antimicrobial capability equivalent to that of 1% H₂O₂ against both Escherichia coli and Staphylococcus aureus. Gram(+) S. aureus cells were more susceptible to H₂O₂ than Gram(−) E. coli and >99% of S. aureus were killed after 1 h incubation with the membrane. Pristine and GA-crosslinked nanofibrous membrane with in situ production of H₂O₂ were self-sterilized in which no microorganism contamination on the membrane could be detected after 2 weeks incubation on an agar plate. The GOx/Glu membrane may find potential application as versatile antimicrobial materials in the field of biomedicine, in the food and health industries, and especially challenges related to wound healing in diabetic patients. Full article

(This article belongs to the Collection Polymeric Membranes: Science, Materials and Applications)

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16 pages, 6362 KiB

Open AccessEditor’s ChoiceArticle

Hollow-Fiber RO Membranes Fabricated via Adsorption of Low-Charge Poly(vinyl alcohol) Copolymers

by Takashi Ohkame, Kazushi Minegishi, Hideki Sugihara, Keizo Nakagawa, Takuji Shintani, Hideto Matsuyama and Tomohisa Yoshioka

Membranes 2021, 11(12), 981; https://doi.org/10.3390/membranes11120981 - 15 Dec 2021

Cited by 4 | Viewed by 3523

Abstract

We report a new type of alkaline-stable hollow-fiber reverse osmosis (RO) membrane with an outside-in configuration that was established via adsorption of positively charged poly(vinyl alcohol) copolymers containing a small amount of quaternary ammonium moieties. Anionic sulfonated poly(arylene ether sulfone nitrile) hollow-fiber membranes [...] Read more.

We report a new type of alkaline-stable hollow-fiber reverse osmosis (RO) membrane with an outside-in configuration that was established via adsorption of positively charged poly(vinyl alcohol) copolymers containing a small amount of quaternary ammonium moieties. Anionic sulfonated poly(arylene ether sulfone nitrile) hollow-fiber membranes were utilized as a substrate upon which the cationic copolymer layer was self-organized via electrostatic interaction. While the adsorption of the low-charge copolymer on the membrane support proceeded in a Layer-by-Layer (LbL) fashion, it was found that the adsorbed amount by one immersion step was enough to form a defect-free separation layer with a thickness of around 20 nm after cross-linking of vinyl alcohol units with glutaraldehyde. The resultant hollow-fiber membrane showed excellent desalination performances (NaCl rejection of 98.3% at 5 bar and 1500 mg/L), which is comparable with commercial low-pressure polyamide RO membranes, as well as good alkaline resistance. The separation performance could be restored by repeating the LbL treatment after alkaline degradation. Such features of LbL membranes may contribute to extending RO membrane lifetimes. Full article

(This article belongs to the Special Issue State-of-the-Art Membrane Science and Technology in Japan 2021, 2022)

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31 pages, 5256 KiB

Open AccessEditor’s ChoiceArticle

Membrane Domain Localization and Interaction of the Prion-Family Proteins, Prion and Shadoo with Calnexin

by Divya Teja Dondapati, Pradeep Reddy Cingaram, Ferhan Ayaydin, Antal Nyeste, Andor Kanyó, Ervin Welker and Elfrieda Fodor

Membranes 2021, 11(12), 978; https://doi.org/10.3390/membranes11120978 - 13 Dec 2021

Cited by 1 | Viewed by 4426

Abstract

The cellular prion protein (PrP^C) is renowned for its infectious conformational isoform PrP^Sc, capable of templating subsequent conversions of healthy PrP^Cs and thus triggering the group of incurable diseases known as transmissible spongiform encephalopathies. Besides this mechanism [...] Read more.

The cellular prion protein (PrP^C) is renowned for its infectious conformational isoform PrP^Sc, capable of templating subsequent conversions of healthy PrP^Cs and thus triggering the group of incurable diseases known as transmissible spongiform encephalopathies. Besides this mechanism not being fully uncovered, the protein’s physiological role is also elusive. PrP^C and its newest, less understood paralog Shadoo are glycosylphosphatidylinositol-anchored proteins highly expressed in the central nervous system. While they share some attributes and neuroprotective actions, opposing roles have also been reported for the two; however, the amount of data about their exact functions is lacking. Protein–protein interactions and membrane microdomain localizations are key determinants of protein function. Accurate identification of these functions for a membrane protein, however, can become biased due to interactions occurring during sample processing. To avoid such artifacts, we apply a non-detergent-based membrane-fractionation approach to study the prion protein and Shadoo. We show that the two proteins occupy similarly raft and non-raft membrane fractions when expressed in N2a cells and that both proteins pull down the chaperone calnexin in both rafts and non-rafts. These indicate their possible binding to calnexin in both types of membrane domains, which might be a necessary requisite to aid the inherently unstable native conformation during their lifetime. Full article

(This article belongs to the Special Issue Membrane Domains Organization and Interactions)

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21 pages, 6568 KiB

Open AccessEditor’s ChoiceArticle

Distillate Flux Enhancement of Direct Contact Membrane Distillation Modules with Inserting Cross-Diagonal Carbon-Fiber Spacers

by Chii-Dong Ho, Luke Chen, Jun-Wei Lim, Po-Hung Lin and Pin-Tsen Lu

Membranes 2021, 11(12), 973; https://doi.org/10.3390/membranes11120973 - 9 Dec 2021

Cited by 9 | Viewed by 3119

Abstract

A new design of direct-contact membrane distillation (DCMD) modules with cross-diagonal carbon-fiber spacers of various hydrodynamic angles in flow channels to promote turbulence intensity was proposed to enhance pure water productivity. Attempts to reduce the temperature polarization coefficient were achieved by inserting cross-diagonal [...] Read more.

A new design of direct-contact membrane distillation (DCMD) modules with cross-diagonal carbon-fiber spacers of various hydrodynamic angles in flow channels to promote turbulence intensity was proposed to enhance pure water productivity. Attempts to reduce the temperature polarization coefficient were achieved by inserting cross-diagonal carbon-fiber spacers in channels, which create wakes and eddies in both heat and mass transfer behaviors to enhance the permeate flux enhancement. A simplified equation was formulated to obtain the theoretical predictions of heat transfer coefficients in the current DCMD device. The permeate fluxes and temperature distributions of both hot and cold feed streams are represented graphically with the inlet volumetric flow rate and inlet temperature of the hot saline feed stream as parameters. The higher distillate flux of countercurrent-flow operations for saline water desalination was accomplished as compared to the concurrent-flow operations of various hydrodynamic angles. The results show that the agreement between the theoretical predictions and experimental results is reasonably good. The effects of countercurrent-flow operations and inserting carbon fiber spacers have confirmed technical feasibility and device performance enhancement of up to 45%. The influences of operating and design parameters on the pure water productivity with the expense of energy consumption are also discussed. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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11 pages, 3940 KiB

Open AccessEditor’s ChoiceArticle

Effect of Nanopatterning on Concentration Polarization during Nanofiltration

by Lauren M. Ward, Barbara G. Fickling and Steven T. Weinman

Membranes 2021, 11(12), 961; https://doi.org/10.3390/membranes11120961 - 7 Dec 2021

Cited by 18 | Viewed by 4671

Abstract

Membranes used for desalination still face challenges during operation. One of these challenges is the buildup of salt ions at the membrane surface. This is known as concentration polarization, and it has a negative effect on membrane water permeance and salt rejection. In [...] Read more.

Membranes used for desalination still face challenges during operation. One of these challenges is the buildup of salt ions at the membrane surface. This is known as concentration polarization, and it has a negative effect on membrane water permeance and salt rejection. In an attempt to decrease concentration polarization, a line-and-groove nanopattern was applied to a nanofiltration (NF) membrane. Aqueous sodium sulfate (Na₂SO₄) solutions were used to test the rejection and permeance of both pristine and patterned membranes. It was found that the nanopatterns did not reduce but increased the concentration polarization at the membrane surface. Based on these studies, different pattern shapes and sizes should be investigated to gain a fundamental understanding of the influence of pattern size and shape on concentration polarization. Full article

(This article belongs to the Collection Polymeric Membranes: Science, Materials and Applications)

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22 pages, 5179 KiB

Open AccessEditor’s ChoiceArticle

Membrane Distillation: Pre-Treatment Effects on Fouling Dynamics

by Paula G. Santos, Cíntia M. Scherer, Adriano G. Fisch and Marco Antônio S. Rodrigues

Membranes 2021, 11(12), 958; https://doi.org/10.3390/membranes11120958 - 3 Dec 2021

Cited by 9 | Viewed by 2965

Abstract

In the research reported in this paper, membrane distillation was employed to recover water from a concentrated saline petrochemical effluent. According to the results, the use of membrane distillation is technically feasible when pre-treatments are employed to mitigate fouling. A mathematical model was [...] Read more.

In the research reported in this paper, membrane distillation was employed to recover water from a concentrated saline petrochemical effluent. According to the results, the use of membrane distillation is technically feasible when pre-treatments are employed to mitigate fouling. A mathematical model was used to evaluate the fouling mechanism, showing that the deposition of particulate and precipitated material occurred in all tests; however, the fouling dynamic depends on the pre-treatment employed (filtration, or filtration associated with a pH adjustment). The deposit layer formed by particles is not cohesive, allowing its entrainment to the bulk flow. The precipitate fouling showed a minimal tendency to entrainment. Also, precipitate fouling served as a coupling agent among adjacent particles, increasing the fouling layer cohesion. Full article

(This article belongs to the Special Issue Water Treatment Process)

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20 pages, 4921 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Catalysts and Membranes for MCH Dehydrogenation: A Mini Review

by Durga Acharya, Derrick Ng and Zongli Xie

Membranes 2021, 11(12), 955; https://doi.org/10.3390/membranes11120955 - 1 Dec 2021

Cited by 29 | Viewed by 6636

Abstract

Methylcyclohexane (MCH), one of the liquid organic hydrogen carriers (LOHCs), offers a convenient way to store, transport, and supply hydrogen. Some features of MCH such as its liquid state at ambient temperature and pressure, large hydrogen storage capacity, its well-known catalytic endothermic dehydrogenation [...] Read more.

Methylcyclohexane (MCH), one of the liquid organic hydrogen carriers (LOHCs), offers a convenient way to store, transport, and supply hydrogen. Some features of MCH such as its liquid state at ambient temperature and pressure, large hydrogen storage capacity, its well-known catalytic endothermic dehydrogenation reaction and ease at which its dehydrogenated counterpart (toluene) can be hydrogenated back to MCH and make it one of the serious contenders for the development of hydrogen storage and transportation system of the future. In addition to advances on catalysts for MCH dehydrogenation and inorganic membrane for selective and efficient separation of hydrogen, there are increasing research interests on catalytic membrane reactors (CMR) that combine a catalyst and hydrogen separation membrane together in a compact system for improved efficiency because of the shift of the equilibrium dehydrogenation reaction forwarded by the continuous removal of hydrogen from the reaction mixture. Development of efficient CMRs can serve as an important step toward commercially viable hydrogen production systems. The recently demonstrated commercial MCH-TOL based hydrogen storage plant, international transportation network and compact hydrogen producing plants by Chiyoda and some other companies serves as initial successful steps toward the development of full-fledged operation of manufacturing, transportation and storage of zero carbon emission hydrogen in the future. There have been initiatives by industries in the development of compact on-board dehydrogenation plants to fuel hydrogen-powered locomotives. This review mainly focuses on recent advances in different technical aspects of catalytic dehydrogenation of MCH and some significant achievements in the commercial development of MCH-TOL based hydrogen storage, transportation and supply systems, along with the challenges and future prospects. Full article

(This article belongs to the Collection Featured Reviews in Membrane Science)

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19 pages, 1063 KiB

Open AccessEditor’s ChoiceReview

A Brief Introduction to Some Aspects of the Fluid–Mosaic Model of Cell Membrane Structure and Its Importance in Membrane Lipid Replacement

by Garth L. Nicolson and Gonzalo Ferreira de Mattos

Membranes 2021, 11(12), 947; https://doi.org/10.3390/membranes11120947 - 29 Nov 2021

Cited by 27 | Viewed by 12091

Abstract

Early cell membrane models placed most proteins external to lipid bilayers in trimolecular structures or as modular lipoprotein units. These thermodynamically untenable structures did not allow lipid lateral movements independent of membrane proteins. The Fluid–Mosaic Membrane Model accounted for these and other properties, [...] Read more.

Early cell membrane models placed most proteins external to lipid bilayers in trimolecular structures or as modular lipoprotein units. These thermodynamically untenable structures did not allow lipid lateral movements independent of membrane proteins. The Fluid–Mosaic Membrane Model accounted for these and other properties, such as membrane asymmetry, variable lateral mobilities of membrane components and their associations with dynamic complexes. Integral membrane proteins can transform into globular structures that are intercalated to various degrees into a heterogeneous lipid bilayer matrix. This simplified version of cell membrane structure was never proposed as the ultimate biomembrane description, but it provided a basic nanometer scale framework for membrane organization. Subsequently, the structures associated with membranes were considered, including peripheral membrane proteins, and cytoskeletal and extracellular matrix components that restricted lateral mobility. In addition, lipid–lipid and lipid–protein membrane domains, essential for cellular signaling, were proposed and eventually discovered. The presence of specialized membrane domains significantly reduced the extent of the fluid lipid matrix, so membranes have become more mosaic with some fluid areas over time. However, the fluid regions of membranes are very important in lipid transport and exchange. Various lipid globules, droplets, vesicles and other membranes can fuse to incorporate new lipids or expel damaged lipids from membranes, or they can be internalized in endosomes that eventually fuse with other internal vesicles and membranes. They can also be externalized in a reverse process and released as extracellular vesicles and exosomes. In this Special Issue, the use of membrane phospholipids to modify cellular membranes in order to modulate clinically relevant host properties is considered. Full article

(This article belongs to the Special Issue Advances in Membrane Lipid Replacement and Therapy)

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20 pages, 5199 KiB

Open AccessEditor’s ChoiceArticle

Upgrading Biogas from Small Agricultural Sources into Biomethane by Membrane Separation

by Aleksandra Janusz-Cygan, Jolanta Jaschik and Marek Tańczyk

Membranes 2021, 11(12), 938; https://doi.org/10.3390/membranes11120938 - 27 Nov 2021

Cited by 10 | Viewed by 3606

Abstract

The agriculture sector in Poland could provide 7.8 billion m³ of biogas per year, but this potential would be from dispersed plants of a low capacity. In the current study, a membrane process was investigated for the upgrading biogas to biomethane that [...] Read more.

The agriculture sector in Poland could provide 7.8 billion m³ of biogas per year, but this potential would be from dispersed plants of a low capacity. In the current study, a membrane process was investigated for the upgrading biogas to biomethane that conforms to the requirements for grid gas in Poland. It was assumed that such a process is based on membranes made from modified polysulfone or polyimide, available in the market in Air Products PRISM PA1020 and UBE UMS-A5 modules, respectively. The case study has served an agricultural biogas plant in southern Poland, which provides the stream of 5 m³ (STP) h⁻¹ of biogas with a composition of CH₄ (52 vol.%), CO₂ (46.3 vol.%), N₂ (1.6 vol.%) and O₂ (0.1 vol.%), after a pretreatment. It was theoretically shown that this is possible to obtain the biomethane stream of at least 96 vol.% of CH₄ purity, with the concentration of the other biogas components below their respective thresholds, as required in Poland for gas fuel “E”, with methane recovery of up to 87.5% and 71.6% for polyimide and polysulfone membranes, respectively. The energetic efficiency of the separation process is comparable for both membrane materials, as expressed by power excess index, which reaches up to 51.3 kW_th kW_el⁻¹ (polyimide) and 40.7 kW_th kW_el⁻¹ (polysulfone). In turn, the membrane productivity was significantly higher in the case of the polyimide membrane (up to 38.3 kW_th m⁻²) than those based on the polysulfone one (up to 3.13 kW_th m⁻²). Full article

(This article belongs to the Special Issue State-of-the-Art Membrane Science and Technology in Poland 2021-2022)

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15 pages, 3039 KiB

Open AccessEditor’s ChoiceArticle

Zwitterionic Polysulfone Copolymer/Polysulfone Blended Ultrafiltration Membranes with Excellent Thermostability and Antifouling Properties

by Dalong Li, Changlu Gao, Xinyue Wang, Gang Wu, Jinghua Yin, Yudong Huang and Xiuhua Sun

Membranes 2021, 11(12), 932; https://doi.org/10.3390/membranes11120932 - 26 Nov 2021

Cited by 7 | Viewed by 2788

Abstract

Membrane fouling has been one of the most important challenges in membrane separation operations. In this study, we report a facile strategy to prepare antifouling polysulfone (PSf) UF membranes by blending amphiphilic zwitterion polysulfone-co-sulfobetaine polysulfone (PSf-co-SBPSf) copolymer. The copolymer chemical structure was characterized [...] Read more.

Membrane fouling has been one of the most important challenges in membrane separation operations. In this study, we report a facile strategy to prepare antifouling polysulfone (PSf) UF membranes by blending amphiphilic zwitterion polysulfone-co-sulfobetaine polysulfone (PSf-co-SBPSf) copolymer. The copolymer chemical structure was characterized by ¹HNMR spectroscopy. The PSf/PSf-co-SBPSf blend membranes with various zwitterionic SBPSf segment contents exhibited better surface hydrophilicity and excellent antifouling ability compared to PSf and PSf/PEG membranes. The significant increase of both porosity and water permeance indicates that the PSf-co-SBPSf has a pore-forming effect. The pure water flux and flux recovery ratio of the PSf/PSf-co-SBPSf blend membranes were both remarked to improve 286.43 L/m²h and 92.26%, while bovine serum albumin (BSA) rejection remained at a high level (97.66%). More importantly, the water flux and BSA rejection see minimal variance after heat treatment, indicating excellent thermostability. Overall, the PSf/PSf-co-SBPSf blend membranes achieved a comprehensive performance of sustainable hydrophilic, high permeation flux, and remarkable antifouling ability, thus becoming a promising candidate in high-temperature separation application. Full article

(This article belongs to the Special Issue Membrane Fouling Control in Water Treatment)

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10 pages, 3743 KiB

Open AccessEditor’s ChoiceArticle

Development of Pure Silica CHA Membranes for CO₂ Separation

by Gabriel Gama da Silva Figueiredo, Daishi Takayama, Katsunori Ishii, Mikihiro Nomura, Takamasa Onoki, Takuya Okuno, Hiromasa Tawarayama and Shinji Ishikawa

Membranes 2021, 11(12), 926; https://doi.org/10.3390/membranes11120926 - 25 Nov 2021

Cited by 7 | Viewed by 3695

Abstract

Thin pure-silica chabazite (Si-CHA) membranes have been synthesized by using a secondary growth method on a porous silica substrate. A CO₂ permeance of 2.62 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ with a CO₂/CH₄ permeance ratio [...] Read more.

Thin pure-silica chabazite (Si-CHA) membranes have been synthesized by using a secondary growth method on a porous silica substrate. A CO₂ permeance of 2.62 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ with a CO₂/CH₄ permeance ratio of 62 was obtained through a Si-CHA membrane crystallized for 8 h using a parent gel of H₂O/SiO₂ ratio of 4.6. The CO₂ permeance through the Si-CHA membrane on a porous silica substrate was twice as high as that through the membrane synthesized on a porous alumina substrate, which displayed a similar zeolite layer thickness. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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15 pages, 3112 KiB

Open AccessEditor’s ChoiceArticle

Membranes for the Gas/Liquid Phase Separation at Elevated Temperatures: Characterization of the Liquid Entry Pressure

by Sara Claramunt, Florian Völker, Uta Gerhards, Manfred Kraut and Roland Dittmeyer

Membranes 2021, 11(12), 907; https://doi.org/10.3390/membranes11120907 - 23 Nov 2021

Cited by 6 | Viewed by 2591

Abstract

Hydrophobic membranes were characterized at elevated temperatures. Pressure was applied at the feed and permeate side to ensure liquid phase conditions. Within this scope, the applicability of different polymeric and ceramic membranes in terms of liquid entry pressure was studied using water. The [...] Read more.

Hydrophobic membranes were characterized at elevated temperatures. Pressure was applied at the feed and permeate side to ensure liquid phase conditions. Within this scope, the applicability of different polymeric and ceramic membranes in terms of liquid entry pressure was studied using water. The Visual Method and the Pressure Step Method were applied for the experimental investigation. The results show the Pressure Step Method to be an early detection method. The tests at higher pressure and temperature conditions using the Pressure Step Method revealed the temperature as being the main factor affecting the liquid entry pressure. Novel LEP data up to 120 °C and 2.5 bar were obtained, which broadens the application range of hydrophobic membranes. Full article

(This article belongs to the Special Issue Recent Advances in Membrane Distillation)

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17 pages, 2584 KiB

Open AccessEditor’s ChoiceArticle

O-GlcNAcylation Inhibits Endocytosis of Amyloid Precursor Protein by Decreasing Its Localization in Lipid Raft Microdomains

by Oh-Hoon Kwon, Yoon Young Cho, Jung Hee Lee and Sungkwon Chung

Membranes 2021, 11(12), 909; https://doi.org/10.3390/membranes11120909 - 23 Nov 2021

Cited by 5 | Viewed by 2767

Abstract

Like protein phosphorylation, O-GlcNAcylation is a common post-translational protein modification. We already reported that O-GlcNAcylation of amyloid precursor protein (APP) in response to insulin signaling reduces neurotoxic amyloid-β (Aβ) production via inhibition of APP endocytosis. Internalized APP is delivered to endosomes and lysosomes [...] Read more.

Like protein phosphorylation, O-GlcNAcylation is a common post-translational protein modification. We already reported that O-GlcNAcylation of amyloid precursor protein (APP) in response to insulin signaling reduces neurotoxic amyloid-β (Aβ) production via inhibition of APP endocytosis. Internalized APP is delivered to endosomes and lysosomes where Aβ is produced. However, the molecular mechanism involved in the effect of APP O-GlcNAcylation on APP trafficking remains unknown. To investigate the relationship between APP O-GlcNAcylation and APP endocytosis, we tested the effects of insulin on neuroblastoma SH-SY5Y cells overexpressing APP and BACE1, and cultured rat hippocampal neurons. The present study showed that APP O-GlcNAcylation translocated APP from lipid raft to non-raft microdomains in the plasma membrane by using immunocytochemistry and discontinuous sucrose gradients method. By using the biotinylation method, we also found that APP preferentially underwent endocytosis from lipid rafts and that the amount of internalized APP from lipid rafts was specifically reduced by O-GlcNAcylation. These results indicate that O-GlcNAcylation can regulate lipid raft-dependent APP endocytosis via translocation of APP into non-raft microdomains. Our findings showed a new functional role of O-GlcNAcylation for the regulation of APP trafficking, offering new mechanistic insight for Aβ production. Full article

(This article belongs to the Special Issue Membrane Domains Organization and Interactions)

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16 pages, 3767 KiB

Open AccessEditor’s ChoiceArticle

Anion Exchange Membranes Based on Imidazoline Quaternized Polystyrene Copolymers for Fuel Cell Applications

by Li-Cheng Jheng, Chung-Yen Hsu and Hong-Yi Yeh

Membranes 2021, 11(11), 901; https://doi.org/10.3390/membranes11110901 - 22 Nov 2021

Cited by 16 | Viewed by 3694

Abstract

Imidazoline is a five-membered heterocycle derived by the partial reduction of one double bond of the imidazole ring. This work prepared new anion exchange membranes (AEMs) based on imidazoline quaternized polystyrene copolymers bearing N-b-hydroxyethyl oleyl imidazolinium pendent groups to evaluate the application potential [...] Read more.

Imidazoline is a five-membered heterocycle derived by the partial reduction of one double bond of the imidazole ring. This work prepared new anion exchange membranes (AEMs) based on imidazoline quaternized polystyrene copolymers bearing N-b-hydroxyethyl oleyl imidazolinium pendent groups to evaluate the application potential for anion exchange membrane fuel cells (AEMFCs). For comparison, an imidazole quaternized polystyrene copolymer was also synthesized. The polymer chemical structure was confirmed by FTIR, NMR, and TGA. In addition, the essential properties of membranes, including ion exchange capacity (IEC), water uptake, and hydroxide conductivity, were measured. The alkaline stabilities of imidazolium-based and imidazolinium-based AEMs were compared by means of the changes in the TGA thermograms, FTIR spectra, and hydroxide conductivity during the alkaline treatment in 1 M KOH at 60 °C for 144 h. The results showed that the imidazolinium-based AEMs exhibited relatively lower hydroxide conductivity (5.77 mS/cm at 70 °C) but much better alkaline stability compared with the imidazolium-based AEM. The imidazolinium-based AEM (PSVBImn-50) retained 92% of its hydroxide conductivity after the alkaline treatment. Besides, the fuel cell performance of the imidazolium-based and imidazolinium-based AEMs was examined by single-cell tests. Full article

(This article belongs to the Special Issue Membranes in Electrochemistry Applications)

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23 pages, 1249 KiB

Open AccessEditor’s ChoiceReview

State-of-the-Art Ceramic Membranes for Oily Wastewater Treatment: Modification and Application

by Mingliang Chen, Sebastiaan G. J. Heijman and Luuk C. Rietveld

Membranes 2021, 11(11), 888; https://doi.org/10.3390/membranes11110888 - 19 Nov 2021

Cited by 58 | Viewed by 8484

Abstract

Membrane filtration is considered to be one of the most promising methods for oily wastewater treatment. Because of their hydrophilic surface, ceramic membranes show less fouling compared with their polymeric counterparts. Membrane fouling, however, is an inevitable phenomenon in the filtration process, leading [...] Read more.

Membrane filtration is considered to be one of the most promising methods for oily wastewater treatment. Because of their hydrophilic surface, ceramic membranes show less fouling compared with their polymeric counterparts. Membrane fouling, however, is an inevitable phenomenon in the filtration process, leading to higher energy consumption and a shorter lifetime of the membrane. It is therefore important to improve the fouling resistance of the ceramic membranes in oily wastewater treatment. In this review, we first focus on the various methods used for ceramic membrane modification, aiming for application in oily wastewater. Then, the performance of the modified ceramic membranes is discussed and compared. We found that, besides the traditional sol-gel and dip-coating methods, atomic layer deposition is promising for ceramic membrane modification in terms of the control of layer thickness, and pore size tuning. Enhanced surface hydrophilicity and surface charge are two of the most used strategies to improve the performance of ceramic membranes for oily wastewater treatment. Nano-sized metal oxides such as TiO₂, ZrO₂ and Fe₂O₃ and graphene oxide are considered to be the potential candidates for ceramic membrane modification for flux enhancement and fouling alleviation. The passive antifouling ceramic membranes, e.g., photocatalytic and electrified ceramic membranes, have shown some potential in fouling control, oil rejection and flux enhancement, but have their limitations. Full article

(This article belongs to the Special Issue Membrane Filtration for Water Reclamation)

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34 pages, 3444 KiB

Open AccessEditor’s ChoiceReview

Advances and Applications of Hollow Fiber Nanofiltration Membranes: A Review

by Tim Sewerin, Maria G. Elshof, Sonia Matencio, Marcel Boerrigter, Jimmy Yu and Joris de Grooth

Membranes 2021, 11(11), 890; https://doi.org/10.3390/membranes11110890 - 19 Nov 2021

Cited by 43 | Viewed by 13049

Abstract

Hollow fiber nanofiltration (NF) membranes have gained increased attention in recent years, partly driven by the availability of alternatives to polyamide-based dense separation layers. Moreover, the global market for NF has been growing steadily in recent years and is expected to grow even [...] Read more.

Hollow fiber nanofiltration (NF) membranes have gained increased attention in recent years, partly driven by the availability of alternatives to polyamide-based dense separation layers. Moreover, the global market for NF has been growing steadily in recent years and is expected to grow even faster. Compared to the traditional spiral-wound configuration, the hollow fiber geometry provides advantages such as low fouling tendencies and effective hydraulic cleaning possibilities. The alternatives to polyamide layers are typically chemically more stable and thus allow operation and cleaning at more extreme conditions. Therefore, these new NF membranes are of interest for use in a variety of applications. In this review, we provide an overview of the applications and emerging opportunities for these membranes. Next to municipal wastewater and drinking water processes, we have put special focus on industrial applications where hollow fiber NF membranes are employed under more strenuous conditions or used to recover specific resources or solutes. Full article

(This article belongs to the Special Issue New Phenomenological Findings in Nanofiltration)

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18 pages, 3383 KiB

Open AccessEditor’s ChoiceArticle

Extracellular Vesicles Tropism: A Comparative Study between Passive Innate Tropism and the Active Engineered Targeting Capability of Lymphocyte-Derived EVs

by Tania Limongi, Francesca Susa, Bianca Dumontel, Luisa Racca, Michela Perrone Donnorso, Doriana Debellis and Valentina Cauda

Membranes 2021, 11(11), 886; https://doi.org/10.3390/membranes11110886 - 18 Nov 2021

Cited by 17 | Viewed by 4623

Abstract

Cellular communications take place thanks to a well-connected network of chemical–physical signals, biomolecules, growth factors, and vesicular messengers that travel inside or between cells. A deep knowledge of the extracellular vesicle (EV) system allows for a better understanding of the whole series of [...] Read more.

Cellular communications take place thanks to a well-connected network of chemical–physical signals, biomolecules, growth factors, and vesicular messengers that travel inside or between cells. A deep knowledge of the extracellular vesicle (EV) system allows for a better understanding of the whole series of phenomena responsible for cell proliferation and death. To this purpose, here, a thorough immuno-phenotypic characterization of B-cell EV membranes is presented. Furthermore, the cellular membrane of B lymphocytes, Burkitt lymphoma, and human myeloid leukemic cells were characterized through cytofluorimetry assays and fluorescent microscopy analysis. Through cytotoxicity and internalization tests, the tropism of B lymphocyte-derived EVs was investigated toward the parental cell line and two different cancer cell lines. In this study, an innate capability of passive targeting of the native EVs was distinguished from the active targeting capability of monoclonal antibody-engineered EVs, able to selectively drive the vesicles, enhancing their internalization into the target cancer cells. In particular, the specific targeting ability of anti-CD20 engineered EVs towards Daudi cells, highly expressing CD20 marker on their cell membrane, was proved, while almost no internalization events were observed in HL60 cells, since they did not express an appreciable amount of the CD20 marker on their plasma membranes. Full article

(This article belongs to the Special Issue Shedding New Light on the Cell Biology and Medicine of Extracellular Vesicles)

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33 pages, 3332 KiB

Open AccessEditor’s ChoiceReview

Preparation, Performance and Challenges of Catalyst Layer for Proton Exchange Membrane Fuel Cell

by Meng Xie, Tiankuo Chu, Tiantian Wang, Kechuang Wan, Daijun Yang, Bing Li, Pingwen Ming and Cunman Zhang

Membranes 2021, 11(11), 879; https://doi.org/10.3390/membranes11110879 - 15 Nov 2021

Cited by 55 | Viewed by 14451

Abstract

In this paper, the composition, function and structure of the catalyst layer (CL) of a proton exchange membrane fuel cell (PEMFC) are summarized. The hydrogen reduction reaction (HOR) and oxygen reduction reaction (ORR) processes and their mechanisms and the main interfaces of CL [...] Read more.

In this paper, the composition, function and structure of the catalyst layer (CL) of a proton exchange membrane fuel cell (PEMFC) are summarized. The hydrogen reduction reaction (HOR) and oxygen reduction reaction (ORR) processes and their mechanisms and the main interfaces of CL (PEM|CL and CL|MPL) are described briefly. The process of mass transfer (hydrogen, oxygen and water), proton and electron transfer in MEA are described in detail, including their influencing factors. The failure mechanism of CL (Pt particles, CL crack, CL flooding, etc.) and the degradation mechanism of the main components in CL are studied. On the basis of the existing problems, a structure optimization strategy for a high-performance CL is proposed. The commonly used preparation processes of CL are introduced. Based on the classical drying theory, the drying process of a wet CL is explained. Finally, the research direction and future challenges of CL are pointed out, hoping to provide a new perspective for the design and selection of CL materials and preparation equipment. Full article

(This article belongs to the Special Issue Membrane Electrode Assembly (MEA))

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14 pages, 2099 KiB

Open AccessEditor’s ChoiceArticle

Pilot Plant for the Capture of Ammonia from the Atmosphere of Pig and Poultry Farms Using Gas-Permeable Membrane Technology

by María Soto-Herranz, Mercedes Sánchez-Báscones, Juan Manuel Antolín-Rodríguez and Pablo Martín-Ramos

Membranes 2021, 11(11), 859; https://doi.org/10.3390/membranes11110859 - 7 Nov 2021

Cited by 12 | Viewed by 4011

Abstract

Gas-permeable membrane (GPM) technology is a possible solution to reduce ammonia (NH₃) emissions from livestock housing. This paper presents the results obtained with an NH₃-capture prototype based on the use of expanded polytetrafluoroethylene (ePTFE) membranes in real conditions in [...] Read more.

Gas-permeable membrane (GPM) technology is a possible solution to reduce ammonia (NH₃) emissions from livestock housing. This paper presents the results obtained with an NH₃-capture prototype based on the use of expanded polytetrafluoroethylene (ePTFE) membranes in real conditions in a gestating sow house and a free-range laying hen house, comparing them with the results obtained in controlled laboratory conditions for the same type of waste. The NH₃ present in the air of the livestock housing was captured by reaction with an acidic solution flowing inside the membranes. The periods of continuous operation of the pilot plant were 232 days at the pig farm and 256 days at the poultry farm. The NH₃ recovery rate at the end of those periods was 2.3 and 0.4 g TAN·m⁻²·d⁻¹ in the pig and the poultry farms, respectively. The limiting factor for the capture process was the NH₃ concentration in the air, with the highest recovery occurring in the most concentrated atmosphere. Differences in NH₃ capture were observed between seasons and farms, with capture efficiencies of 1.62 and 0.33 g·m⁻²·d⁻¹ in summer and 3.85 and 1.20 g·m⁻²·d⁻¹ in winter for pig and poultry farms, respectively. The observed differences were mainly due to the higher ventilation frequency in the summer months, which resulted in a lower NH₃ concentration inside the houses compared to the winter months. This is especially important when considering the real applicability of this technology. The results obtained suggest that GPM technology holds promise for limiting NH₃ emissions from livestock housing with NH₃ ambient concentrations close to 20 ppm or as part of manure storage facilities, given that it allows for recovery of nitrogen in a stable and concentrated solution, which can be used as a fertilizer. Full article

(This article belongs to the Special Issue From Novel Material Concept to Scalable Membrane Product for Gas Separation)

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18 pages, 3833 KiB

Open AccessEditor’s ChoiceReview

Fluorescence Approaches for Characterizing Ion Channels in Synthetic Bilayers

by Md. Sirajul Islam, James P. Gaston and Matthew A. B. Baker

Membranes 2021, 11(11), 857; https://doi.org/10.3390/membranes11110857 - 4 Nov 2021

Cited by 5 | Viewed by 6783

Abstract

Ion channels are membrane proteins that play important roles in a wide range of fundamental cellular processes. Studying membrane proteins at a molecular level becomes challenging in complex cellular environments. Instead, many studies focus on the isolation and reconstitution of the membrane proteins [...] Read more.

Ion channels are membrane proteins that play important roles in a wide range of fundamental cellular processes. Studying membrane proteins at a molecular level becomes challenging in complex cellular environments. Instead, many studies focus on the isolation and reconstitution of the membrane proteins into model lipid membranes. Such simpler, in vitro, systems offer the advantage of control over the membrane and protein composition and the lipid environment. Rhodopsin and rhodopsin-like ion channels are widely studied due to their light-interacting properties and are a natural candidate for investigation with fluorescence methods. Here we review techniques for synthesizing liposomes and for reconstituting membrane proteins into lipid bilayers. We then summarize fluorescence assays which can be used to verify the functionality of reconstituted membrane proteins in synthetic liposomes. Full article

(This article belongs to the Special Issue Lipid Regulation of Ion Channels and Transporters)

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14 pages, 2110 KiB

Open AccessEditor’s ChoiceArticle

Cryo-EM Structure of Mechanosensitive Channel YnaI Using SMA2000: Challenges and Opportunities

by Claudio Catalano, Danya Ben-Hail, Weihua Qiu, Paul Blount, Amedee des Georges and Youzhong Guo

Membranes 2021, 11(11), 849; https://doi.org/10.3390/membranes11110849 - 31 Oct 2021

Cited by 13 | Viewed by 4245

Abstract

Mechanosensitive channels respond to mechanical forces exerted on the cell membrane and play vital roles in regulating the chemical equilibrium within cells and their environment. High-resolution structural information is required to understand the gating mechanisms of mechanosensitive channels. Protein-lipid interactions are essential for [...] Read more.

Mechanosensitive channels respond to mechanical forces exerted on the cell membrane and play vital roles in regulating the chemical equilibrium within cells and their environment. High-resolution structural information is required to understand the gating mechanisms of mechanosensitive channels. Protein-lipid interactions are essential for the structural and functional integrity of mechanosensitive channels, but detergents cannot maintain the crucial native lipid environment for purified mechanosensitive channels. Recently, detergent-free systems have emerged as alternatives for membrane protein structural biology. This report shows that while membrane-active polymer, SMA2000, could retain some native cell membrane lipids on the transmembrane domain of the mechanosensitive-like YnaI channel, the complete structure of the transmembrane domain of YnaI was not resolved. This reveals a significant limitation of SMA2000 or similar membrane-active copolymers. This limitation may come from the heterogeneity of the polymers and nonspecific interactions between the polymers and the relatively large hydrophobic pockets within the transmembrane domain of YnaI. However, this limitation offers development opportunities for detergent-free technology for challenging membrane proteins. Full article

(This article belongs to the Special Issue The Structure, Dynamics and Function of Membrane Proteins)

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36 pages, 15520 KiB

Open AccessEditor’s ChoiceReview

A Critical Review on Electric Field-Assisted Membrane Processes: Implications for Fouling Control, Water Recovery, and Future Prospects

by Yuxiang Shen and Appala Raju Badireddy

Membranes 2021, 11(11), 820; https://doi.org/10.3390/membranes11110820 - 27 Oct 2021

Cited by 19 | Viewed by 5137

Abstract

Electrofiltration, an electric field-assisted membrane process, has been a research topic of growing popularity due to its ability to improve membrane performance by providing in situ antifouling conditions in a membrane system. The number of reports on electrofiltration have increased exponentially over the [...] Read more.

Electrofiltration, an electric field-assisted membrane process, has been a research topic of growing popularity due to its ability to improve membrane performance by providing in situ antifouling conditions in a membrane system. The number of reports on electrofiltration have increased exponentially over the past two decades. These reports explored many innovations, such as novel configurations of an electric field, engineered membrane materials, and interesting designs of foulant compositions and membrane modules. Recent electrofiltration literature focused mainly on compiling results without a comprehensive comparative analysis across different works. The main objective of this critical review is to, first, organize, compare and contrast the results across various electrofiltration studies; second, discuss various types of mechanisms that could be incorporated into electrofiltration and their effect on membrane system performance; third, characterize electrofiltration phenomenon; fourth, interpret the effects of various operational conditions on the performance of electrofiltration; fifth, evaluate the state-of-the-art knowledge associated with modeling efforts in electrofiltration; sixth, discuss the energy costs related to the implementation of electrofiltration; and finally, identify the current knowledge gaps that hinder the transition of the lab-scale observations to industry-scale electrofiltration as well as the future prospects of electrofiltration. Full article

(This article belongs to the Topic Water Reclamation and Reuse)

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16 pages, 3877 KiB

Open AccessEditor’s ChoiceArticle

Bicomponent PLA Nanofiber Nonwovens as Highly Efficient Filtration Media for Particulate Pollutants and Pathogens

by Danyang Gao, Renhai Zhao, Xue Yang, Fuxing Chen and Xin Ning

Membranes 2021, 11(11), 819; https://doi.org/10.3390/membranes11110819 - 27 Oct 2021

Cited by 21 | Viewed by 3934

Abstract

Herein, a novel form of bicomponent nanofiber membrane containing stereo-complex polylactic acid (SC-PLA) was successfully produced by the side-by-side electrospinning of Poly (L-lactic acid) (PLLA) and Poly (D-lactic acid) (PDLA). We demonstrate that through these environmentally sustainable materials, highly efficient nanofiber assemblies for [...] Read more.

Herein, a novel form of bicomponent nanofiber membrane containing stereo-complex polylactic acid (SC-PLA) was successfully produced by the side-by-side electrospinning of Poly (L-lactic acid) (PLLA) and Poly (D-lactic acid) (PDLA). We demonstrate that through these environmentally sustainable materials, highly efficient nanofiber assemblies for filtration can be constructed at very low basis weight. The physical and morphological structure, crystalline structure, hydrophobicity, porous structure, and filtration performance of the fibrous membranes were thoroughly characterized. It was shown that the fabricated polylactic acid (PLA) side-by-side fiber membrane had the advantages of excellent hydrophobicity, small average pore size, high porosity, high filtration efficiency, low pressure drop as well as superior air permeability. At the very low basis weight of 1.1 g/m², the filtration efficiency and pressure drop of the prepared side-by-side membrane reached 96.2% and 30 Pa, respectively. Overall, this biomass-based, biodegradable filtration material has the potential to replace the fossil fuel-based polypropylene commercial meltblown materials for the design and development in filtration, separation, biomedical, personal protection and other fields. Full article

(This article belongs to the Special Issue Electrospun Nanofiber Membranes: From Synthesis to Applications)

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21 pages, 4718 KiB

Open AccessEditor’s ChoiceArticle

Novel Cellulose Acetate-Based Monophasic Hybrid Membranes for Improved Blood Purification Devices: Characterization under Dynamic Conditions

by Adriana Janeca, Flávia S. C. Rodrigues, Maria Clara Gonçalves and Mónica Faria

Membranes 2021, 11(11), 825; https://doi.org/10.3390/membranes11110825 - 27 Oct 2021

Cited by 14 | Viewed by 4438

Abstract

A novel cellulose acetate-based monophasic hybrid skinned amine-functionalized CA-SiO₂-(CH₂)₃NH₂ membrane was synthesized using an innovative method which combines the phase inversion and sol-gel techniques. Morphological characterization was performed by scanning electron microscopy (SEM), and the chemical [...] Read more.

A novel cellulose acetate-based monophasic hybrid skinned amine-functionalized CA-SiO₂-(CH₂)₃NH₂ membrane was synthesized using an innovative method which combines the phase inversion and sol-gel techniques. Morphological characterization was performed by scanning electron microscopy (SEM), and the chemical composition was analyzed by Fourier transform infrared spectroscopy in attenuated total reflection mode (ATR-FTIR). The characterization of the monophasic hybrid CA-SiO₂-(CH₂)₃NH₂ membrane in terms of permeation properties was carried out in an in-house-built single hemodialysis membrane module (SHDMM) under dynamic conditions. Permeation experiments were performed to determine the hydraulic permeability (Lp), molecular weight cut-off (MWCO) and the rejection coefficients to urea, creatinine, uric acid, and albumin. SEM confirmed the existence of a very thin (<1 µm) top dense layer and a much thicker bottom porous surface, and ATR-FTIR showed the main bands belonging to the CA-based membranes. Permeation studies revealed that the Lp and MWCO of the CA-SiO₂-(CH₂)₃NH₂ membrane were 66.61 kg·h⁻¹·m⁻²·bar⁻¹ and 24.5 kDa, respectively, and that the Lp was 1.8 times higher compared to a pure CA membrane. Furthermore, the CA-SiO₂-(CH₂)₃NH₂ membrane fully permeated urea, creatinine, and uric acid while completely retaining albumin. Long-term filtration studies of albumin solutions indicated that fouling does not occur at the surface of the CA-SiO₂-(CH₂)₃NH₂ membrane. Full article

(This article belongs to the Special Issue State-of-the-Art Membrane Science and Technology in the Iberian Peninsula 2021-2022)

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30 pages, 5108 KiB

Open AccessEditor’s ChoiceReview

A Review on Ion-Exchange Membranes Fouling during Electrodialysis Process in Food Industry, Part 2: Influence on Transport Properties and Electrochemical Characteristics, Cleaning and Its Consequences

by Natalia Pismenskaya, Myriam Bdiri, Veronika Sarapulova, Anton Kozmai, Julie Fouilloux, Lassaad Baklouti, Christian Larchet, Estelle Renard and Lasâad Dammak

Membranes 2021, 11(11), 811; https://doi.org/10.3390/membranes11110811 - 25 Oct 2021

Cited by 33 | Viewed by 6501

Abstract

Ion-exchange membranes (IEMs) are increasingly used in dialysis and electrodialysis processes for the extraction, fractionation and concentration of valuable components, as well as reagent-free control of liquid media pH in the food industry. Fouling of IEMs is specific compared to that observed in [...] Read more.

Ion-exchange membranes (IEMs) are increasingly used in dialysis and electrodialysis processes for the extraction, fractionation and concentration of valuable components, as well as reagent-free control of liquid media pH in the food industry. Fouling of IEMs is specific compared to that observed in the case of reverse or direct osmosis, ultrafiltration, microfiltration, and other membrane processes. This specificity is determined by the high concentration of fixed groups in IEMs, as well as by the phenomena inherent only in electromembrane processes, i.e., induced by an electric field. This review analyzes modern scientific publications on the effect of foulants (mainly typical for the dairy, wine and fruit juice industries) on the structural, transport, mass transfer, and electrochemical characteristics of cation-exchange and anion-exchange membranes. The relationship between the nature of the foulant and the structure, physicochemical, transport properties and behavior of ion-exchange membranes in an electric field is analyzed using experimental data (ion exchange capacity, water content, conductivity, diffusion permeability, limiting current density, water splitting, electroconvection, etc.) and modern mathematical models. The implications of traditional chemical cleaning are taken into account in this analysis and modern non-destructive membrane cleaning methods are discussed. Finally, challenges for the near future were identified. Full article

(This article belongs to the Special Issue In-Depth on the Fouling and Antifouling of Ion-Exchange Membranes)

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17 pages, 5790 KiB

Open AccessEditor’s ChoiceArticle

A Facile Method to Control Pore Structure of PVDF/SiO₂ Composite Membranes for Efficient Oil/Water Purification

by Qianqian Xu, Yuchao Chen, Tonghu Xiao and Xing Yang

Membranes 2021, 11(11), 803; https://doi.org/10.3390/membranes11110803 - 22 Oct 2021

Cited by 24 | Viewed by 3579

Abstract

The use of poly(vinylidene fluoride) (PVDF) microfiltration (MF) membranes to purify oily water has received much attention. However, it is challenging to obtain high-performance PVDF microfiltration membranes due to severe surface fouling and rapid decline of permeability. This study explored a new approach [...] Read more.

The use of poly(vinylidene fluoride) (PVDF) microfiltration (MF) membranes to purify oily water has received much attention. However, it is challenging to obtain high-performance PVDF microfiltration membranes due to severe surface fouling and rapid decline of permeability. This study explored a new approach to fabricate high-performance PVDF/silica (SiO₂) composite membrane via the use of a polymer solution featuring lower critical solution temperature (LCST) characteristics and the non-solvent thermally induced phase separation method (NTIPS). Coupling with morphological observations, the membrane formation kinetics were analyzed in depth to understand the synergistic effect between the LCST solution properties and fabrication conditions in NTIPS. Utilizing such a synergistic effect, the transition from finger-like macrovoid pores to bi-continuous highly connected pores could be flexibly tuned by increasing the PVDF concentration and the weight ratio of SiO₂/PVDF in the dope solution and by raising the coagulation temperature to above the LCST of the solution. The filtration experiments with surfactant-stabilized oil-water emulsion showed that the permeation flux of the PVDF/SiO₂ composite membranes was higher than 318 L·m⁻²·h⁻¹·bar⁻¹ and the rejection above 99.2%. It was also shown that the PVDF/SiO₂ composite membranes, especially those fabricated above the LCST, demonstrated better hydrophilicity, which resulted in significant enhancement in the anti-fouling properties for oil/water emulsion separation. Compared to the benchmark pure PVDF membrane in oily water purification, the optimal composite membrane T70 was demonstrated via the 3-cycle filtration experiments with a significantly improved flux recovery ratio (F_rr) and minimal reduced irreversible fouling (R_ir). Overall, with the developed method in this work, facile procedure to tune the membrane morphology and pore structure was demonstrated, resulting in high performance composite membranes suitable for oil/water emulsion separation. Full article

(This article belongs to the Special Issue Nanostructured Membranes II)

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22 pages, 6221 KiB

Open AccessEditor’s ChoiceArticle

Prediction of Membrane Failure in a Water Purification Plant Using Nonhomogeneous Poisson Process Models

by Takashi Hashimoto and Satoshi Takizawa

Membranes 2021, 11(11), 800; https://doi.org/10.3390/membranes11110800 - 20 Oct 2021

Cited by 4 | Viewed by 2902

Abstract

The prediction of membrane failure in full-scale water purification plants is an important but difficult task. Although previous studies employed accelerated laboratory-scale tests of membrane failure, it is not possible to reproduce the complex operational conditions of full-scale plants. Therefore, we aimed to [...] Read more.

The prediction of membrane failure in full-scale water purification plants is an important but difficult task. Although previous studies employed accelerated laboratory-scale tests of membrane failure, it is not possible to reproduce the complex operational conditions of full-scale plants. Therefore, we aimed to develop prediction models of membrane failure using actual membrane failure data. Because membrane filtration systems are repairable systems, nonhomogeneous Poisson process (NHPP) models, i.e., power law and log-linear models, were employed; the model parameters were estimated using the membrane failure data from a full-scale plant operated for 13 years. Both models were able to predict cumulative failures for forthcoming years; nonetheless, the power law model showed higher stability and narrower confidence intervals than the log-linear model. By integrating two membrane replacement criteria, namely deterioration of filtrate water quality and reduction of membrane permeability, it was possible to predict the time to replace all the membranes on a water purification plant. Finally, the NHPP models coupled with a nonparametric bootstrap method provided a method to select membrane modules for earlier replacement than others. Although the criteria for membrane replacement may vary among membrane filtration plants, the NHPP models presented in this study could be applied to any other plant with membrane failure data. Full article

(This article belongs to the Special Issue Water and Wastewater Treatment Technologies with Membrane Filtration)

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11 pages, 1795 KiB

Open AccessEditor’s ChoiceArticle

Biphenyl-Based Covalent Triazine Framework/Matrimid^® Mixed-Matrix Membranes for CO₂/CH₄ Separation

by Stefanie Bügel, Quang-Dien Hoang, Alex Spieß, Yangyang Sun, Shanghua Xing and Christoph Janiak

Membranes 2021, 11(10), 795; https://doi.org/10.3390/membranes11100795 - 19 Oct 2021

Cited by 10 | Viewed by 3735

Abstract

Processes, such as biogas upgrading and natural gas sweetening, make CO₂/CH₄ separation an environmentally relevant and current topic. One way to overcome this separation issue is the application of membranes. An increase in separation efficiency can be achieved by applying [...] Read more.

Processes, such as biogas upgrading and natural gas sweetening, make CO₂/CH₄ separation an environmentally relevant and current topic. One way to overcome this separation issue is the application of membranes. An increase in separation efficiency can be achieved by applying mixed-matrix membranes, in which filler materials are introduced into polymer matrices. In this work, we report the covalent triazine framework CTF-biphenyl as filler material in a matrix of the glassy polyimide Matrimid^®. MMMs with 8, 16, and 24 wt% of the filler material are applied for CO₂/CH₄ mixed-gas separation measurements. With a CTF-biphenyl loading of only 16 wt%, the CO₂ permeability is more than doubled compared to the pure polymer membrane, while maintaining the high CO₂/CH₄ selectivity of Matrimid^®. Full article

(This article belongs to the Special Issue Mixed-Matrix Membranes and Polymeric Membranes)

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21 pages, 6819 KiB

Open AccessEditor’s ChoiceArticle

An Experimental Performance Study of a Catalytic Membrane Reactor for Ethanol Steam Reforming over a Metal Honeycomb Catalyst

by Nikita Eremeev, Alexey Krasnov, Yuliya Bespalko, Ludmilla Bobrova, Oleg Smorygo and Vladislav Sadykov

Membranes 2021, 11(10), 790; https://doi.org/10.3390/membranes11100790 - 18 Oct 2021

Cited by 13 | Viewed by 3125

Abstract

The present study deals with the combination of ethanol steam reforming over a monolithic catalyst and hydrogen separation by membrane in a lab-scale catalytic membrane reactor (CMR). The catalyst was comprised of honeycomb thin-walled Fechralloy substrate loaded with Ni + Ru/Pr_0.35Ce [...] Read more.

The present study deals with the combination of ethanol steam reforming over a monolithic catalyst and hydrogen separation by membrane in a lab-scale catalytic membrane reactor (CMR). The catalyst was comprised of honeycomb thin-walled Fechralloy substrate loaded with Ni + Ru/Pr_0.35Ce_0.35Zr_0.35O₂ active component. The asymmetric supported membrane consisted of a thin Ni-Cu alloy–Nd tungstate nanocomposite dense permselective layer deposited on a hierarchically structured asymmetric support. It has been shown that the monolithic catalyst-assisted CMR is capable of increasing the driving potential for hydrogen permeation through the same membrane as compared with that of the packed bed catalyst by increasing the retentate hydrogen concentration. Important operating parameters responsible for the low carbon deposition rate as well as the amount of hydrogen produced from 1 mol of ethanol, such as the temperature range of 700–900 °C, the water/ethanol molar ratio of 4 in the feed, have been determined. Regarding the choice of the reagent concentration (ethanol and steam in Ar), its magnitude may directly interfere with the effectiveness of the reaction-separation process in the CMR. Full article

(This article belongs to the Special Issue Novel Supported Membranes for Syngas Generation and Hydrogen Separation)

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17 pages, 7345 KiB

Open AccessEditor’s ChoiceReview

Recent Developments in Nanoporous Graphene Membranes for Organic Solvent Nanofiltration: A Short Review

by Yoon-Tae Nam, Jun-Hyeok Kang, Jae-Dong Jang, Jun-Hyuk Bae, Hee-Tae Jung and Dae-Woo Kim

Membranes 2021, 11(10), 793; https://doi.org/10.3390/membranes11100793 - 18 Oct 2021

Cited by 10 | Viewed by 5656

Abstract

Graphene-based membranes are promising candidates for efficient organic solvent nanofiltration (OSN) processes because of their unique structural characteristics, such as mechanical/chemical stability and precise molecular sieving. Recently, to improve organic solvent permeance and selectivity, nanopores have been fabricated on graphene planes via chemical [...] Read more.

Graphene-based membranes are promising candidates for efficient organic solvent nanofiltration (OSN) processes because of their unique structural characteristics, such as mechanical/chemical stability and precise molecular sieving. Recently, to improve organic solvent permeance and selectivity, nanopores have been fabricated on graphene planes via chemical and physical methods. The nanopores serve as an additional channel for facilitating ultrafast solvent permeation while filtering organic molecules by size exclusion. This review summarizes the recent developments in nanoporous graphene (NG)-based membranes for OSN applications. The membranes are categorized depending on the membrane structure: single-layer NG, multilayer NG, and graphene-based composite membranes hybridized with other porous materials. Techniques for nanopore generation on graphene, as well as the challenges faced and the perspectives required for the commercialization of NG membranes, are also discussed. Full article

(This article belongs to the Special Issue Advancements of 2D Materials-Based Membranes)

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18 pages, 50625 KiB

Open AccessEditor’s ChoiceArticle

Fabrication of Polyelectrolyte Membranes of Pectin Graft-Copolymers with PVA and Their Composites with Phosphomolybdic Acid for Drug Delivery, Toxic Metal Ion Removal, and Fuel Cell Applications

by Raagala Vijitha, Nagella Sivagangi Reddy, Kasula Nagaraja, Tiruchuru J. Sudha Vani, Marlia M. Hanafiah, Katta Venkateswarlu, Sivarama Krishna Lakkaboyana, Kummari S. V. Krishna Rao and Kummara Madhususdana Rao

Membranes 2021, 11(10), 792; https://doi.org/10.3390/membranes11100792 - 18 Oct 2021

Cited by 17 | Viewed by 3885

Abstract

In this study, a simple method for the fabrication of highly diffusive, adsorptive and conductive eco-friendly polyelectrolyte membranes (PEMs) with sulfonate functionalized pectin and poly(vinyl alcohol)(PVA) was established. The graft-copolymers were synthesized by employing the use of potassium persulfate as a free radical [...] Read more.

In this study, a simple method for the fabrication of highly diffusive, adsorptive and conductive eco-friendly polyelectrolyte membranes (PEMs) with sulfonate functionalized pectin and poly(vinyl alcohol)(PVA) was established. The graft-copolymers were synthesized by employing the use of potassium persulfate as a free radical initiator from pectin (PC), a carbohydrate polymer with 2-acrylamido-2-methyl-1-propanesulphonic acid (AMPS) and sodium 4-vinylbenzene sulphonate (SVBS). The PEMs were fabricated from the blends of pectin graft-copolymers (PC-g-AMPS and PC-g-SVBS) and PVA by using a solution casting method, followed by chemical crosslinking with glutaraldehyde. The composite PEMs were fabricated by mixing phosphomolybdic acid with the aforementioned blends. The PEMs were successfully characterized by FTIR, XRD, SEM, and EDAX studies. They were assessed for the controlled release of an anti-cancer drug (5-fluorouracil) and the removal of toxic metal ions (Cu²⁺) from aqueous media. Furthermore, the composite PEMs were evaluated for fuel cell application. The 5-fluorouracil release capacity of the PEMs was found to be 93% and 99.1% at 300 min in a phosphate buffer solution (pH = 7.4). The highest Cu²⁺ removal was observed at 206.7 and 190.1 mg/g. The phosphomolybdic acid-embedded PEMs showed superior methanol permeability, i.e., 6.83 × 10⁻⁵, and 5.94 × 10^−5, compared to the pristine PEMs. Furthermore, the same trend was observed for the proton conductivities, i.e., 13.77 × 10⁻³, and 18.6 × 10⁻³ S/cm at 30 °C. Full article

(This article belongs to the Special Issue Development of Novel Composite Membranes in Water/Wastewater Treatment)

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37 pages, 32302 KiB

Open AccessEditor’s ChoiceReview

A Review on Ion-Exchange Membrane Fouling during the Electrodialysis Process in the Food Industry, Part 1: Types, Effects, Characterization Methods, Fouling Mechanisms and Interactions

by Lasâad Dammak, Julie Fouilloux, Myriam Bdiri, Christian Larchet, Estelle Renard, Lassaad Baklouti, Veronika Sarapulova, Anton Kozmai and Natalia Pismenskaya

Membranes 2021, 11(10), 789; https://doi.org/10.3390/membranes11100789 - 16 Oct 2021

Cited by 55 | Viewed by 7904

Abstract

Electrodialysis (ED) was first established for water desalination and is still highly recommended in this field for its high water recovery, long lifetime and acceptable electricity consumption. Today, thanks to technological progress in ED processes and the emergence of new ion-exchange membranes (IEMs), [...] Read more.

Electrodialysis (ED) was first established for water desalination and is still highly recommended in this field for its high water recovery, long lifetime and acceptable electricity consumption. Today, thanks to technological progress in ED processes and the emergence of new ion-exchange membranes (IEMs), ED has been extended to many other applications in the food industry. This expansion of uses has also generated several problems such as IEMs’ lifetime limitation due to different ageing phenomena (because of organic and/or mineral compounds). The current commercial IEMs show excellent performance in ED processes; however, organic foulants such as proteins, surfactants, polyphenols or other natural organic matters can adhere on their surface (especially when using anion-exchange membranes: AEMs) forming a colloid layer or can infiltrate the membrane matrix, which leads to the increase in electrical resistance, resulting in higher energy consumption, lower water recovery, loss of membrane permselectivity and current efficiency as well as lifetime limitation. If these aspects are not sufficiently controlled and mastered, the use and the efficiency of ED processes will be limited since, it will no longer be competitive or profitable compared to other separation methods. In this work we reviewed a significant amount of recent scientific publications, research and reviews studying the phenomena of IEM fouling during the ED process in food industry with a special focus on the last decade. We first classified the different types of fouling according to the most commonly used classifications. Then, the fouling effects, the characterization methods and techniques as well as the different fouling mechanisms and interactions as well as their influence on IEM matrix and fixed groups were presented, analyzed, discussed and illustrated. Full article

(This article belongs to the Special Issue In-Depth on the Fouling and Antifouling of Ion-Exchange Membranes)

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22 pages, 7156 KiB

Open AccessEditor’s ChoiceArticle

Assessment of Sieverts Law Assumptions and ‘n’ Values in Palladium Membranes: Experimental and Theoretical Analyses

by Abdulrahman Alraeesi and Tracy Gardner

Membranes 2021, 11(10), 778; https://doi.org/10.3390/membranes11100778 - 12 Oct 2021

Cited by 16 | Viewed by 8815

Abstract

Palladium and palladium alloy membranes are superior materials for hydrogen purification, removal, or reaction processes. Sieverts’ Law suggests that the flux of hydrogen through such membranes is proportional to the difference between the feed and permeate side partial pressures, each raised to the [...] Read more.

Palladium and palladium alloy membranes are superior materials for hydrogen purification, removal, or reaction processes. Sieverts’ Law suggests that the flux of hydrogen through such membranes is proportional to the difference between the feed and permeate side partial pressures, each raised to the 0.5 power (n = 0.5). Sieverts’ Law is widely applied in analyzing the steady state hydrogen permeation through Pd-based membranes, even in some cases where the assumptions made in deriving Sieverts’ Law do not apply. Often permeation data are fit to the model allowing the pressure exponent (n) to vary. This study experimentally assessed the validity of Sieverts’ Law as hydrogen was separated from other gases and theoretically modelled the effects of pressure and temperature on the assumptions and hence the accuracy of the 0.5-power law even with pure hydrogen feed. Hydrogen fluxes through Pd and Pd-Ag alloy foils from feed mixtures (5–83% helium in hydrogen; 473–573 K; with and without a sweep gas) were measured to study the effect of concentration polarization (CP) on hydrogen permeance and the applicability of Sieverts’ Law under such conditions. Concentration polarization was found to dominate hydrogen transport under some experimental conditions, particularly when feed concentrations of hydrogen were low. All mixture feed experiments showed deviation from Sieverts’ Law. For example, the hydrogen flux through Pd foil was found to be proportional to the partial pressure difference (n ≈ 1) rather than being proportional to the difference in the square root of the partial pressures (n = 0.5), as suggested by Sieverts’ Law, indicating the high degree of concentration polarization. A theoretical model accounting for Langmuir adsorption with temperature dependent adsorption equilibrium coefficient was made and used to assess the effect of varying feed pressure from 1–136 atm at fixed temperature, and of varying temperature from 298 to 1273 K at fixed pressure. Adsorption effects, which dominate at high pressure and at low temperature, result in pressure exponents (n) values less than 0.5. With better understanding of the transport steps, a qualitative analysis of literature (n) values of 0.5, 0.5 < n < 1, and n > 1, was conducted suggesting the role of each condition or step on the hydrogen transport based on the empirically fit exponent value. Full article

(This article belongs to the Special Issue Modeling and Simulation of Industrial and Environmental Processes with Membranes)

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18 pages, 1375 KiB

Open AccessEditor’s ChoiceArticle

Optimization of Energy Efficiency, Operation Costs, Carbon Footprint and Ecological Footprint with Reverse Osmosis Membranes in Seawater Desalination Plants

by Federico Leon, Alejandro Ramos and Sebastian O. Perez-Baez

Membranes 2021, 11(10), 781; https://doi.org/10.3390/membranes11100781 - 12 Oct 2021

Cited by 21 | Viewed by 5102

Abstract

This article shows the optimization of the reverse osmosis process in seawater desalination plants, taking the example of the Canary Islands, where there are more than 320 units of different sizes, both private and public. The objective is to improve the energy efficiency [...] Read more.

This article shows the optimization of the reverse osmosis process in seawater desalination plants, taking the example of the Canary Islands, where there are more than 320 units of different sizes, both private and public. The objective is to improve the energy efficiency of the system in order to save on operation costs as well as reduce the carbon and ecological footprints. Reverse osmosis membranes with higher surface area have lower energy consumption, as well as energy recovery systems to recover the brine pressure and introduce it in the system. Accounting for the operation, maintenance and handling of the membranes is also important in energy savings, in order to improve the energy efficiency. The energy consumption depends on the permeate water quality required and the model of the reverse osmosis membrane installed in the seawater desalination plant, as it is shown in this study. Full article

(This article belongs to the Special Issue Theoretical and Experimental Investigation of the Mass and Heat Transfers in Membrane Separation Processes)

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17 pages, 3178 KiB

Open AccessEditor’s ChoiceArticle

Improved CO₂/CH₄ Separation Properties of Cellulose Triacetate Mixed–Matrix Membranes with CeO₂@GO Hybrid Fillers

by Chhabilal Regmi, Saeed Ashtiani, Zdeněk Sofer and Karel Friess

Membranes 2021, 11(10), 777; https://doi.org/10.3390/membranes11100777 - 11 Oct 2021

Cited by 15 | Viewed by 3252

Abstract

The study of the effects associated with the compatibility of the components of the hybrid filler with polymer matrix, which ultimately decide on achieving mixed matrix membranes (MMMs) with better gas separation properties, is essential. Herein, a facile solution casting process of simple [...] Read more.

The study of the effects associated with the compatibility of the components of the hybrid filler with polymer matrix, which ultimately decide on achieving mixed matrix membranes (MMMs) with better gas separation properties, is essential. Herein, a facile solution casting process of simple incorporating CeO₂@GO hybrid inorganic filler material is implemented. Significant improvements in material and physico-chemical properties of the synthesized membranes were observed by SEM, XRD, TGA, and stress-strain measurements. Usage of graphene oxide (GO) with polar groups on the surface enabled forming bonds with ceria (CeO₂) nanoparticles and CTA polymer and provided the homogeneous dispersion of the nanofillers in the hybrid MMMs. Moreover, increasing GO loading concentration enhanced both gas permeation in MMMs and CO₂ gas uptakes. The best performance was achieved by the membrane containing 7 wt.% of GO with CO₂ permeability of 10.14 Barrer and CO₂/CH₄ selectivity 50.7. This increase in selectivity is almost fifteen folds higher than the CTA-CeO₂ membrane sample, suggesting the detrimental effect of GO for enhancing the selectivity property of the MMMs. Hence, a favorable synergistic effect of CeO₂@GO hybrid fillers on gas separation performance is observed, propounding the efficient and feasible strategy of using hybrid fillers in the membrane for the potential biogas upgrading process. Full article

(This article belongs to the Special Issue From Novel Material Concept to Scalable Membrane Product for Gas Separation)

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10 pages, 1893 KiB

Open AccessEditor’s ChoiceArticle

A Study to Enhance the Nitrate-Nitrogen Removal Rate without Dismantling the NF Module by Building a PFSA Ionomer-Coated NF Module

by In-Kee Park, Jian Hou, Jaehan Yun, Hee-Dae Lee and Chang-Hyun Lee

Membranes 2021, 11(10), 769; https://doi.org/10.3390/membranes11100769 - 9 Oct 2021

Cited by 4 | Viewed by 3004

Abstract

Water resource pollution by nitrate-nitrogen, mainly caused by anthropogenic causes, induces eutrophication of water resources, and indicates the degree of organic pollution. Therefore, this study devised a method for coating PFSA ionomer with excellent chemical resistance without disassembling the module to improve the [...] Read more.

Water resource pollution by nitrate-nitrogen, mainly caused by anthropogenic causes, induces eutrophication of water resources, and indicates the degree of organic pollution. Therefore, this study devised a method for coating PFSA ionomer with excellent chemical resistance without disassembling the module to improve the removal rate of nitrate-nitrogen in water by using a cyclic coating method on a commercially available nanofiltration membrane (NF membrane) module. Nafion was prepared as a supercritical fluid dispersion using a high-temperature and high-pressure reactor, and the particle size and the degree of dispersion of the dispersion were analyzed by DLS. The crystallinity was confirmed through XRD by drying the dispersion in the liquid state. After the dispersion was prepared as a membrane according to the heat treatment conditions, the characteristics according to the particle size were analyzed by tensile strength and TEM. The nitrate-nitrogen removal rate of the NF membrane module coated with the dispersion was increased by 93% compared to that before coating. Therefore, the result showed that the cycle coating method devised in this study could efficiently coat the already commercialized module and improve performance. Full article

(This article belongs to the Special Issue Recent Membrane Research and Development in Korea)

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23 pages, 3036 KiB

Open AccessEditor’s ChoiceArticle

Impact of Chlorinated-Assisted Backwash and Air Backwash on Ultrafiltration Fouling Management for Urban Wastewater Tertiary Treatment

by Jiaqi Yang, Mathias Monnot, Lionel Ercolei and Philippe Moulin

Membranes 2021, 11(10), 733; https://doi.org/10.3390/membranes11100733 - 27 Sep 2021

Cited by 5 | Viewed by 3022

Abstract

To improve membrane fouling management, the NaClO-assisted backwash has been developed to improve permeability maintenance and reduce the need for intensive chemical cleanings. This study is aimed to focus on the efficiency of NaClO-assisted backwash in real UF pilot scale and with periodic [...] Read more.

To improve membrane fouling management, the NaClO-assisted backwash has been developed to improve permeability maintenance and reduce the need for intensive chemical cleanings. This study is aimed to focus on the efficiency of NaClO-assisted backwash in real UF pilot scale and with periodic classic backwash (CB) and air backwash (AB). The impacts on hydraulic filtration performance, physicochemical properties of membrane material under different addition frequencies of NaClO, and the performance of chlorinated CB and AB will be discussed. In result, 10 mg Cl₂ L⁻¹ NaClO addition in backwash water is confirmed to greatly improve the overall filtration performance and backwash cleaning efficiency. One condition stands out from the other due to better control of irreversible fouling, less NaClO consumption in 10 years prediction, sustainable and adaptable filtration performance, and less potential damage on the physicochemical properties of the membrane. Additionally, it can be inferred from this experiment that frequent contact with NaClO induced some degradation on the PES-made UF membrane surface properties. To retain the best state of UF membrane on anti-fouling and qualified production, the optimized condition with more frequent NaClO contact was not suggested for long-term filtration. Full article

(This article belongs to the Special Issue Troubleshooting of Membrane Processes in Real Operation)

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22 pages, 5307 KiB

Open AccessEditor’s ChoiceArticle

Experimental Study of a Heat Pump for Simultaneous Cooling and Desalination by Membrane Distillation

by Ahmadou Tidiane Diaby, Paul Byrne, Patrick Loulergue, Ousmane Sow and Thierry Maré

Membranes 2021, 11(10), 725; https://doi.org/10.3390/membranes11100725 - 23 Sep 2021

Cited by 11 | Viewed by 3519

Abstract

Heat pump systems can simultaneously produce cooling energy for space cooling in hotels, office and residential buildings and heat for desalination using membrane distillation (MD). The MD technique uses a heat input at a temperature compatible with the levels of heat pump condensers [...] Read more.

Heat pump systems can simultaneously produce cooling energy for space cooling in hotels, office and residential buildings and heat for desalination using membrane distillation (MD). The MD technique uses a heat input at a temperature compatible with the levels of heat pump condensers (<60 °C). A heat pump prototype coupled with an air-gap membrane distillation unit was constructed and tested. This paper presents the experimental study on a lab-scale prototype and details the two operating modes “continuous” and “controlled” simulating an air conditioning system and a food storage, respectively. The experimental results enable to analyze the performance of the prototype and the physical phenomena involved. Finally, the study shows that this system could be a promising solution to help supplying freshwater to people in hot regions of the world. Full article

(This article belongs to the Special Issue Advanced Membrane Processes in Water Treatment)

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