Membranes

35 pages, 29822 KB

Open AccessEditor’s ChoiceReview

Green Approaches for Sustainable Development of Liquid Separation Membrane

by Wei Jie Lee, Pei Sean Goh, Woei Jye Lau, Ahmad Fauzi Ismail and Nidal Hilal

Membranes 2021, 11(4), 235; https://doi.org/10.3390/membranes11040235 - 25 Mar 2021

Cited by 32 | Viewed by 8717

Water constitutes one of the basic necessities of life. Around 71% of the Earth is covered by water, however, not all of it is readily available as fresh water for daily consumption. Fresh water scarcity is a chronic issue which poses a threat [...] Read more.

Water constitutes one of the basic necessities of life. Around 71% of the Earth is covered by water, however, not all of it is readily available as fresh water for daily consumption. Fresh water scarcity is a chronic issue which poses a threat to all living things on Earth. Seawater, as a natural resource abundantly available all around the world, is a potential water source to fulfil the increasing water demand. Climate-independent seawater desalination has been touted as a crucial alternative to provide fresh water. While the membrane-based desalination process continues to dominate the global desalination market, the currently employed membrane fabrication materials and processes inevitably bring adverse impacts to the environment. This review aims to elucidate and provide a comprehensive outlook of the recent efforts based on greener approaches used for desalination membrane fabrication, which paves the way towards achieving sustainable and eco-friendly processes. Membrane fabrication using green chemistry effectively minimizes the generation of hazardous compounds during membrane preparation. The future trends and recommendations which could potentially be beneficial for researchers in this field are also highlighted. Full article

(This article belongs to the Collection New Challenges in Membranes for Water and Wastewater Application)

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17 pages, 1838 KB

Open AccessEditor’s ChoiceReview

Physiological Basis of Extracorporeal Membrane Oxygenation and Extracorporeal Carbon Dioxide Removal in Respiratory Failure

by Barbara Ficial, Francesco Vasques, Joe Zhang, Stephen Whebell, Michael Slattery, Tomas Lamas, Kathleen Daly, Nicola Agnew and Luigi Camporota

Membranes 2021, 11(3), 225; https://doi.org/10.3390/membranes11030225 - 22 Mar 2021

Cited by 34 | Viewed by 15556

Abstract

Extracorporeal life support (ECLS) for severe respiratory failure has seen an exponential growth in recent years. Extracorporeal membrane oxygenation (ECMO) and extracorporeal CO₂ removal (ECCO₂R) represent two modalities that can provide full or partial support of the native lung function, [...] Read more.

Extracorporeal life support (ECLS) for severe respiratory failure has seen an exponential growth in recent years. Extracorporeal membrane oxygenation (ECMO) and extracorporeal CO₂ removal (ECCO₂R) represent two modalities that can provide full or partial support of the native lung function, when mechanical ventilation is either unable to achieve sufficient gas exchange to meet metabolic demands, or when its intensity is considered injurious. While the use of ECMO has defined indications in clinical practice, ECCO₂R remains a promising technique, whose safety and efficacy are still being investigated. Understanding the physiological principles of gas exchange during respiratory ECLS and the interactions with native gas exchange and haemodynamics are essential for the safe applications of these techniques in clinical practice. In this review, we will present the physiological basis of gas exchange in ECMO and ECCO₂R, and the implications of their interaction with native lung function. We will also discuss the rationale for their use in clinical practice, their current advances, and future directions. Full article

(This article belongs to the Special Issue Advances in Extracorporeal Membrane Oxygenation)

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54 pages, 12920 KB

Open AccessEditor’s ChoiceReview

Polymer Membranes for All-Vanadium Redox Flow Batteries: A Review

by Dennis Düerkop, Hartmut Widdecke, Carsten Schilde, Ulrich Kunz and Achim Schmiemann

Membranes 2021, 11(3), 214; https://doi.org/10.3390/membranes11030214 - 18 Mar 2021

Cited by 63 | Viewed by 15981

Abstract

Redox flow batteries such as the all-vanadium redox flow battery (VRFB) are a technical solution for storing fluctuating renewable energies on a large scale. The optimization of cells regarding performance, cycle stability as well as cost reduction are the main areas of research [...] Read more.

Redox flow batteries such as the all-vanadium redox flow battery (VRFB) are a technical solution for storing fluctuating renewable energies on a large scale. The optimization of cells regarding performance, cycle stability as well as cost reduction are the main areas of research which aim to enable more environmentally friendly energy conversion, especially for stationary applications. As a critical component of the electrochemical cell, the membrane influences battery performance, cycle stability, initial investment and maintenance costs. This review provides an overview about flow-battery targeted membranes in the past years (1995–2020). More than 200 membrane samples are sorted into fluoro-carbons, hydro-carbons or N-heterocycles according to the basic polymer used. Furthermore, the common description in membrane technology regarding the membrane structure is applied, whereby the samples are categorized as dense homogeneous, dense heterogeneous, symmetrical or asymmetrically porous. Moreover, these properties as well as the efficiencies achieved from VRFB cycling tests are discussed, e.g., membrane samples of fluoro-carbons, hydro-carbons and N-heterocycles as a function of current density. Membrane properties taken into consideration include membrane thickness, ion-exchange capacity, water uptake and vanadium-ion diffusion. The data on cycle stability and costs of commercial membranes, as well as membrane developments, are compared. Overall, this investigation shows that dense anion-exchange membranes (AEM) and N-heterocycle-based membranes, especially poly(benzimidazole) (PBI) membranes, are suitable for VRFB requiring low self-discharge. Symmetric and asymmetric porous membranes, as well as cation-exchange membranes (CEM) enable VRFB operation at high current densities. Amphoteric ion-exchange membranes (AIEM) and dense heterogeneous CEM are the choice for operation mode with the highest energy efficiency. Full article

(This article belongs to the Special Issue Membrane Surface Modification and Functionalization)

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13 pages, 9126 KB

Open AccessEditor’s ChoiceArticle

Substrate-Independent, Regenerable Anti-Biofouling Coating for Polymeric Membranes

by Juan Zhang, Guang Wang, Jianhua Zhang, Zhiguang Xu, Yan Zhao, Yichao Wang, Fenghua She, Stephen Gray and Lingxue Kong

Membranes 2021, 11(3), 205; https://doi.org/10.3390/membranes11030205 - 13 Mar 2021

Cited by 9 | Viewed by 3479

Abstract

Biofouling is a common but significant issue in the membrane process as it reduces permeate flux, increases energy costs, and shortens the life span of membranes. As an effective antibacterial agent, a small amount of silver nanoparticles (AgNPs) immobilized on membrane surfaces will [...] Read more.

Biofouling is a common but significant issue in the membrane process as it reduces permeate flux, increases energy costs, and shortens the life span of membranes. As an effective antibacterial agent, a small amount of silver nanoparticles (AgNPs) immobilized on membrane surfaces will alleviate the membrane from biofouling. However, loading AgNPs on the membrane surface remains a challenge due to the low loading efficiency or the lack of bonding stability between AgNPs and the membrane surface. In this study, a substrate-independent method is reported to immobilize silver nanoparticles on polymeric membrane surfaces by firstly modifying the membrane surface with functional groups and then forming silver nanoparticles in situ. The obtained membranes had good anti-biofouling properties as demonstrated from disk diffusion and anti-biofouling tests. The silver nanoparticles were stably immobilized on the membrane surfaces and easily regenerated. This method is applicable to various polymeric micro-, ultra-, nano-filtration and reverse osmosis (RO) membranes. Full article

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

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12 pages, 4619 KB

Open AccessEditor’s ChoiceArticle

Trastuzumab Modulates the Protein Cargo of Extracellular Vesicles Released by ERBB2⁺ Breast Cancer Cells

by Silvia Marconi, Sara Santamaria, Martina Bartolucci, Sara Stigliani, Cinzia Aiello, Maria Cristina Gagliani, Grazia Bellese, Andrea Petretto, Katia Cortese and Patrizio Castagnola

Membranes 2021, 11(3), 199; https://doi.org/10.3390/membranes11030199 - 12 Mar 2021

Cited by 9 | Viewed by 3769

Abstract

Cancers overexpressing the ERBB2 oncogene are aggressive and associated with a poor prognosis. Trastuzumab is an ERBB2 specific recombinant antibody employed for the treatment of these diseases since it blocks ERBB2 signaling causing growth arrest and survival inhibition. While the effects of Trastuzumab [...] Read more.

Cancers overexpressing the ERBB2 oncogene are aggressive and associated with a poor prognosis. Trastuzumab is an ERBB2 specific recombinant antibody employed for the treatment of these diseases since it blocks ERBB2 signaling causing growth arrest and survival inhibition. While the effects of Trastuzumab on ERBB2 cancer cells are well known, those on the extracellular vesicles (EVs) released from these cells are scarce. This study focused on ERBB2⁺ breast cancer cells and aimed to establish what type of EVs they release and whether Trastuzumab affects their morphology and molecular composition. To these aims, we performed immunoelectron microscopy, immunoblot, and high-resolution mass spectrometry analyses on EVs purified by differential centrifugation of culture supernatant. Here, we show that EVs released from ERBB2⁺ breast cancer cells are polymorphic in size and appearance and that ERBB2 is preferentially associated with large (120 nm) EVs. Moreover, we report that Trastuzumab (Tz) induces the expression of a specific glycosylated 50 kDa isoform of the CD63 tetraspanin and modulates the expression of 51 EVs proteins, including TOP1. Because these proteins are functionally associated with organelle organization, cytokinesis, and response to lipids, we suggest that Tz may influence these cellular processes in target cells at distant sites via modified EVs. Full article

(This article belongs to the Collection Feature Papers in Membranes in Life Sciences)

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16 pages, 12788 KB

Open AccessEditor’s ChoiceArticle

Interactions of Linear Analogues of Battacin with Negatively Charged Lipid Membranes

by Kinga Burdach, Dagmara Tymecka, Aneta Urban, Robert Lasek, Dariusz Bartosik and Slawomir Sek

Membranes 2021, 11(3), 192; https://doi.org/10.3390/membranes11030192 - 10 Mar 2021

Cited by 9 | Viewed by 3248

Abstract

The increasing resistance of bacteria to available antibiotics has stimulated the search for new antimicrobial compounds with less specific mechanisms of action. These include the ability to disrupt the structure of the cell membrane, which in turn leads to its damage. In this [...] Read more.

The increasing resistance of bacteria to available antibiotics has stimulated the search for new antimicrobial compounds with less specific mechanisms of action. These include the ability to disrupt the structure of the cell membrane, which in turn leads to its damage. In this context, amphiphilic lipopeptides belong to the class of the compounds which may fulfill this requirement. In this paper, we describe two linear analogues of battacin with modified acyl chains to tune the balance between the hydrophilic and hydrophobic portion of lipopeptides. We demonstrate that both compounds display antimicrobial activity with the lowest values of minimum inhibitory concentrations found for Gram-positive pathogens. Therefore, their mechanism of action was evaluated on a molecular level using model lipid films mimicking the membrane of Gram-positive bacteria. The surface pressure measurements revealed that both lipopeptides show ability to bind and incorporate into the lipid monolayers, resulting in decreased ordering of lipids and membrane fluidization. Atomic force microscopy (AFM) imaging demonstrated that the exposure of the model bilayers to lipopeptides leads to a transition from the ordered gel phase to disordered liquid crystalline phase. This observation was confirmed by attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) results, which revealed that lipopeptide action causes a substantial increase in the average tilt angle of lipid acyl chains with respect to the surface normal to compensate for lipopeptide insertion into the membrane. Moreover, the peptide moieties in both molecules do not adopt any well-defined secondary structure upon binding with the lipid membrane. It was also observed that a small difference in the structure of a lipophilic chain, altering the balance between hydrophobic and hydrophilic portion of the molecules, results in different insertion depth of the active compounds. Full article

(This article belongs to the Special Issue Dynamics of Drug Delivery to Model and Cell Membranes)

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16 pages, 6074 KB

Open AccessEditor’s ChoiceReview

Thin-Film Composite Nanofiltration Membranes for Non-Polar Solvents

by Seungmin Lee, Taewon Kang, Jong Young Lee, Jiyu Park, Seoung Ho Choi, Jin-Yeong Yu, Serin Ok and Sang-Hee Park

Membranes 2021, 11(3), 184; https://doi.org/10.3390/membranes11030184 - 9 Mar 2021

Cited by 27 | Viewed by 6939

Abstract

Organic solvent nanofiltration (OSN) has been recognized as an eco-friendly separation system owing to its excellent cost and energy saving efficiency, easy scale-up in the narrow area and mild operation conditions. Membrane properties are the key part in terms of determining the separation [...] Read more.

Organic solvent nanofiltration (OSN) has been recognized as an eco-friendly separation system owing to its excellent cost and energy saving efficiency, easy scale-up in the narrow area and mild operation conditions. Membrane properties are the key part in terms of determining the separation efficiency in the OSN system. In this review paper, the recently reported OSN thin-film composite (TFC) membranes were investigated to understand insight of membrane materials and performance. Especially, we highlighted the representative study concepts and materials of the selective layer of OSN TFC membranes for non-polar solvents. The proper choice of monomers and additives for the selective layer forms much more interconnected voids and the enhanced microporosity, which can improve membrane performance of the OSN TFC membrane with reducing the transport resistance. Therefore, this review paper could be an important bridge to connect with the next-generation OSN TFC membranes for non-polar solvents. Full article

(This article belongs to the Special Issue Polymer Membranes and beyond for Sustainable Separations: From Synthesis, Characterization to Applications)

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20 pages, 5392 KB

Open AccessEditor’s ChoiceArticle

Batch Reverse Osmosis Desalination Modeling under a Time-Dependent Pressure Profile

by Abdeljalil Chougradi, François Zaviska, Ahmed Abed, Jérôme Harmand, Jamal-Eddine Jellal and Marc Heran

Membranes 2021, 11(3), 173; https://doi.org/10.3390/membranes11030173 - 28 Feb 2021

Cited by 22 | Viewed by 5938

Abstract

As world demand for clean water increases, reverse osmosis (RO) desalination has emerged as an attractive solution. Continuous RO is the most used desalination technology today. However, a new generation of configurations, working in unsteady-state feed concentration and pressure, have gained more attention [...] Read more.

As world demand for clean water increases, reverse osmosis (RO) desalination has emerged as an attractive solution. Continuous RO is the most used desalination technology today. However, a new generation of configurations, working in unsteady-state feed concentration and pressure, have gained more attention recently, including the batch RO process. Our work presents a mathematical modeling for batch RO that offers the possibility of monitoring all variables of the process, including specific energy consumption, as a function of time and the recovery ratio. Validation is achieved by comparison with data from the experimental set-up and an existing model in the literature. Energetic comparison with continuous RO processes confirms that batch RO can be more energy efficient than can continuous RO, especially at a higher recovery ratio. It used, at recovery, 31% less energy for seawater and 19% less energy for brackish water. Modeling also proves that the batch RO process does not have to function under constant flux to deliver good energetic performance. In fact, under a linear pressure profile, batch RO can still deliver better energetic performance than can a continuous configuration. The parameters analysis shows that salinity, pump and energy recovery devices efficiencies are directly linked to the energy demand. While increasing feed volume has a limited effect after a certain volume due to dilution, it also shows, interestingly, a recovery ratio interval in which feed volume does not affect specific energy consumption. Full article

(This article belongs to the Special Issue Composite Conducting Membranes: Preparation, Properties, and Applications)

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13 pages, 5504 KB

Open AccessEditor’s ChoiceArticle

Effect of ZnO Nanoparticle Content on the Structural and Ionic Transport Parameters of Polyvinyl Alcohol Based Proton-Conducting Polymer Electrolyte Membranes

by Omed Gh. Abdullah, Yahya A. K. Salman, Dana A. Tahir, Gelas M. Jamal, Hawzhin T. Ahmed, Azhin H. Mohamad and Auday K. Azawy

Membranes 2021, 11(3), 163; https://doi.org/10.3390/membranes11030163 - 26 Feb 2021

Cited by 35 | Viewed by 3891

Abstract

Proton conducting nanocomposite solid polymer electrolytes (NSPEs) based on polyvinyl alcohol/ammonium nitrate (PVA/NH₄NO₃) and different contents of zinc oxide nanoparticles (ZnO-NPs) have been prepared using the casting solution method. The XRD analysis revealed that the sample with 2 wt.% [...] Read more.

Proton conducting nanocomposite solid polymer electrolytes (NSPEs) based on polyvinyl alcohol/ammonium nitrate (PVA/NH₄NO₃) and different contents of zinc oxide nanoparticles (ZnO-NPs) have been prepared using the casting solution method. The XRD analysis revealed that the sample with 2 wt.% ZnO-NPs has a high amorphous content. The ionic conductivity analysis for the prepared membranes has been carried out over a wide range of frequencies at varying temperatures. Impedance analysis shows that sample with 2 wt.% ZnO-NPs has a smaller bulk resistance compared to that of undoped polymer electrolyte. A small amount of ZnO-NPs was found to enhance the proton-conduction significantly; the highest obtainable room-temperature ionic conductivity was 4.71 × 10⁻⁴ S/cm. The effect of ZnO-NP content on the transport parameters of the prepared proton-conducting NSPEs was investigated using the Rice–Roth model; the results reveal that the increase in ionic conductivity is due to an increment in the number of proton ions and their mobility. Full article

(This article belongs to the Section Polymeric Membranes)

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17 pages, 1498 KB

Open AccessEditor’s ChoiceReview

Membrane Protein Stabilization Strategies for Structural and Functional Studies

by Ekaitz Errasti-Murugarren, Paola Bartoccioni and Manuel Palacín

Membranes 2021, 11(2), 155; https://doi.org/10.3390/membranes11020155 - 22 Feb 2021

Cited by 30 | Viewed by 8116

Abstract

Accounting for nearly two-thirds of known druggable targets, membrane proteins are highly relevant for cell physiology and pharmacology. In this regard, the structural determination of pharmacologically relevant targets would facilitate the intelligent design of new drugs. The structural biology of membrane proteins is [...] Read more.

Accounting for nearly two-thirds of known druggable targets, membrane proteins are highly relevant for cell physiology and pharmacology. In this regard, the structural determination of pharmacologically relevant targets would facilitate the intelligent design of new drugs. The structural biology of membrane proteins is a field experiencing significant growth as a result of the development of new strategies for structure determination. However, membrane protein preparation for structural studies continues to be a limiting step in many cases due to the inherent instability of these molecules in non-native membrane environments. This review describes the approaches that have been developed to improve membrane protein stability. Membrane protein mutagenesis, detergent selection, lipid membrane mimics, antibodies, and ligands are described in this review as approaches to facilitate the production of purified and stable membrane proteins of interest for structural and functional studies. Full article

(This article belongs to the Special Issue Experimental and Computational Methods for Membrane Protein Design)

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16 pages, 4337 KB

Open AccessFeature PaperEditor’s ChoiceArticle

PLGA Multiplex Membrane Platform for Disease Modelling and Testing of Therapeutic Compounds

by Antonella Piscioneri, Sabrina Morelli, Enrico Drioli and Loredana De Bartolo

Membranes 2021, 11(2), 112; https://doi.org/10.3390/membranes11020112 - 5 Feb 2021

Cited by 7 | Viewed by 2446

Abstract

A proper validation of an engineered brain microenvironment requires a trade of between the complexity of a cellular construct within the in vitro platform and the simple implementation of the investigational tool. The present work aims to accomplish this challenging balance by setting [...] Read more.

A proper validation of an engineered brain microenvironment requires a trade of between the complexity of a cellular construct within the in vitro platform and the simple implementation of the investigational tool. The present work aims to accomplish this challenging balance by setting up an innovative membrane platform that represents a good compromise between a proper mimicked brain tissue analogue combined with an easily accessible and implemented membrane system. Another key aspect of the in vitro modelling disease is the identification of a precise phenotypic onset as a definite hallmark of the pathology that needs to be recapitulated within the implemented membrane system. On the basis of these assumptions, we propose a multiplex membrane system in which the recapitulation of specific neuro-pathological onsets related to Alzheimer’s disease pathologies, namely oxidative stress and β-amyloid_1–42 toxicity, allowed us to test the neuroprotective effects of trans-crocetin on damaged neurons. The proposed multiplex membrane platform is therefore quite a versatile tool that allows the integration of neuronal pathological events in combination with the testing of new molecules. The present paper explores the use of this alternative methodology, which, relying on membrane technology approach, allows us to study the basic physiological and pathological behaviour of differentiated neuronal cells, as well as their changing behaviour, in response to new potential therapeutic treatment. Full article

(This article belongs to the Special Issue Membrane Systems for Tissue Engineering 2020)

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16 pages, 4533 KB

Open AccessEditor’s ChoiceArticle

Block Copolymer-Based Magnetic Mixed Matrix Membranes—Effect of Magnetic Field on Protein Permeation and Membrane Fouling

by Lakshmeesha Upadhyaya, Mona Semsarilar, Damien Quemener, Rodrigo Fernández-Pacheco, Gema Martinez, Isabel M. Coelhoso, Suzana P. Nunes, João G. Crespo, Reyes Mallada and Carla A. M. Portugal

Membranes 2021, 11(2), 105; https://doi.org/10.3390/membranes11020105 - 2 Feb 2021

Cited by 19 | Viewed by 3758

Abstract

In this study, we report the impact of the magnetic field on protein permeability through magnetic-responsive, block copolymer, nanocomposite membranes with hydrophilic and hydrophobic characters. The hydrophilic nanocomposite membranes were composed of spherical polymeric nanoparticles (NPs) synthesized through polymerization-induced self-assembly (PISA) with iron [...] Read more.

In this study, we report the impact of the magnetic field on protein permeability through magnetic-responsive, block copolymer, nanocomposite membranes with hydrophilic and hydrophobic characters. The hydrophilic nanocomposite membranes were composed of spherical polymeric nanoparticles (NPs) synthesized through polymerization-induced self-assembly (PISA) with iron oxide NPs coated with quaternized poly(2-dimethylamino)ethyl methacrylate. The hydrophobic nanocomposite membranes were prepared via nonsolvent-induced phase separation (NIPS) containing poly (methacrylic acid) and meso-2,3-dimercaptosuccinic acid-coated superparamagnetic nanoparticles (SPNPs). The permeation experiments were carried out using bovine serum albumin (BSA) as the model solute, in the absence of the magnetic field and under permanent and cyclic magnetic field conditions OFF/ON (strategy 1) and ON/OFF (strategy 2). It was observed that the magnetic field led to a lower reduction in the permeate fluxes of magnetic-responsive membranes during BSA permeation, regardless of the magnetic field strategy used, than that obtained in the absence of the magnetic field. Nevertheless, a comparative analysis of the effect caused by the two cyclic magnetic field strategies showed that strategy 2 allowed for a lower reduction of the original permeate fluxes during BSA permeation and higher protein sieving coefficients. Overall, these novel magneto-responsive block copolymer nanocomposite membranes proved to be competent in mitigating biofouling phenomena in bioseparation processes. Full article

(This article belongs to the Special Issue Membrane and Membrane Bioreactors Applied to Health and Life Sciences)

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14 pages, 2545 KB

Open AccessEditor’s ChoiceArticle

Effect of Membrane Properties on the Carbonation of Anion Exchange Membrane Fuel Cells

by Yiwei Zheng, Lyzmarie Nicole Irizarry Colón, Noor Ul Hassan, Eric R. Williams, Morgan Stefik, Jacob M. LaManna, Daniel S. Hussey and William E. Mustain

Membranes 2021, 11(2), 102; https://doi.org/10.3390/membranes11020102 - 31 Jan 2021

Cited by 23 | Viewed by 4899

Abstract

Anion exchange membrane fuel cells (AEMFC) are potentially very low-cost replacements for proton exchange membrane fuel cells. However, AEMFCs suffer from one very serious drawback: significant performance loss when CO₂ is present in the reacting oxidant gas (e.g., air) due to carbonation. [...] Read more.

Anion exchange membrane fuel cells (AEMFC) are potentially very low-cost replacements for proton exchange membrane fuel cells. However, AEMFCs suffer from one very serious drawback: significant performance loss when CO₂ is present in the reacting oxidant gas (e.g., air) due to carbonation. Although the chemical mechanisms for how carbonation leads to voltage loss in operating AEMFCs are known, the way those mechanisms are affected by the properties of the anion exchange membrane (AEM) has not been elucidated. Therefore, this work studies AEMFC carbonation using numerous high-functioning AEMs from the literature and it was found that the ionic conductivity of the AEM plays the most critical role in the CO₂-related voltage loss from carbonation, with the degree of AEM crystallinity playing a minor role. In short, higher conductivity—resulting either from a reduction in the membrane thickness or a change in the polymer chemistry—results in faster CO₂ migration and emission from the anode side. Although this does lead to a lower overall degree of carbonation in the polymer, it also increases CO₂-related voltage loss. Additionally, an operando neutron imaging cell is used to show that as AEMFCs become increasingly carbonated their water content is reduced, which further drives down cell performance. Full article

(This article belongs to the Special Issue Anion Exchange Membrane Fuel Cells and Electrolyzers)

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55 pages, 6736 KB

Open AccessEditor’s ChoiceReview

A Review on Ionic Liquid Gas Separation Membranes

by Karel Friess, Pavel Izák, Magda Kárászová, Mariia Pasichnyk, Marek Lanč, Daria Nikolaeva, Patricia Luis and Johannes Carolus Jansen

Membranes 2021, 11(2), 97; https://doi.org/10.3390/membranes11020097 - 30 Jan 2021

Cited by 141 | Viewed by 18105

Abstract

Ionic liquids have attracted the attention of the industry and research community as versatile solvents with unique properties, such as ionic conductivity, low volatility, high solubility of gases and vapors, thermal stability, and the possibility to combine anions and cations to yield an [...] Read more.

Ionic liquids have attracted the attention of the industry and research community as versatile solvents with unique properties, such as ionic conductivity, low volatility, high solubility of gases and vapors, thermal stability, and the possibility to combine anions and cations to yield an almost endless list of different structures. These features open perspectives for numerous applications, such as the reaction medium for chemical synthesis, electrolytes for batteries, solvent for gas sorption processes, and also membranes for gas separation. In the search for better-performing membrane materials and membranes for gas and vapor separation, ionic liquids have been investigated extensively in the last decade and a half. This review gives a complete overview of the main developments in the field of ionic liquid membranes since their first introduction. It covers all different materials, membrane types, their preparation, pure and mixed gas transport properties, and examples of potential gas separation applications. Special systems will also be discussed, including facilitated transport membranes and mixed matrix membranes. The main strengths and weaknesses of the different membrane types will be discussed, subdividing them into supported ionic liquid membranes (SILMs), poly(ionic liquids) or polymerized ionic liquids (PILs), polymer/ionic liquid blends (physically or chemically cross-linked ‘ion-gels’), and PIL/IL blends. Since membrane processes are advancing as an energy-efficient alternative to traditional separation processes, having shown promising results for complex new separation challenges like carbon capture as well, they may be the key to developing a more sustainable future society. In this light, this review presents the state-of-the-art of ionic liquid membranes, to analyze their potential in the gas separation processes of the future. Full article

(This article belongs to the Special Issue Highly-Efficient Membrane Gas Separation Materials: From Synthesis to Applications)

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15 pages, 1561 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Ultrafiltration Fractionation of Bovine Hemoglobin Hydrolysates: Prediction of Separation Performances for Optimal Enrichment in Antimicrobial Peptide

by Sophie Beaubier, Rémi Przybylski, Alice Bodin, Naïma Nedjar, Pascal Dhulster and Romain Kapel

Membranes 2021, 11(2), 73; https://doi.org/10.3390/membranes11020073 - 20 Jan 2021

Cited by 13 | Viewed by 3061

Abstract

Hydrolysis of bovine hemoglobin (bHb), the main constituent of bovine cruor by-product, releases a natural antimicrobial peptide (NKT) which could present a major interest for food safety. To enrich this, tangential ultrafiltration can be implemented, but ultrafiltration conditions are mainly empirically established. In [...] Read more.

Hydrolysis of bovine hemoglobin (bHb), the main constituent of bovine cruor by-product, releases a natural antimicrobial peptide (NKT) which could present a major interest for food safety. To enrich this, tangential ultrafiltration can be implemented, but ultrafiltration conditions are mainly empirically established. In this context, the application of a simulation method for predicting the NKT yield and enrichment was investigated. Ultrafiltration performances were studied for decolored bHb hydrolysates at different degrees of hydrolysis (DH; 3%, 5%, 10% and 18%) and colored hydrolysates (3% and 5% DH) with 1 and 3 kg·mol⁻¹ regenerated cellulose membranes. The simulation method helped to identify the most promising hydrolysate (in terms of NKT enrichment, yield and productivity) as the 3% DH colored hydrolysate, and UF conditions (volumetric reduction factor of 5 and 3 with 1 and 3 kg·mol⁻¹ membrane, respectively) for higher antimicrobial recovery. A maximal enrichment factor of about 29 and NKT purity of 70% in permeate were observed. The results showed that the antimicrobial activity was in relation with the process selectivity and NKT purity. Finally, this reliable method, applied for predicting the ultrafiltration performances to enrich peptides of interest, is part of a global approach to rationally valorize protein resources from various by-products. Full article

(This article belongs to the Special Issue Membrane Technologies for Sustainable Biofood Production Lines)

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15 pages, 2342 KB

Open AccessEditor’s ChoiceArticle

Measuring Biofouling Potential in SWRO Plants with a Flow-Cytometry-Based Bacterial Growth Potential Method

by Nirajan Dhakal, Sergio G. Salinas-Rodriguez, Joshua Ampah, Jan C. Schippers and Maria D. Kennedy

Membranes 2021, 11(2), 76; https://doi.org/10.3390/membranes11020076 - 20 Jan 2021

Cited by 16 | Viewed by 4705

Abstract

Measuring the bacterial growth potential of seawater reverse osmosis (SWRO) feed water is an issue that is receiving growing attention. This study developed and demonstrated the applicability of the flow-cytometry (FCM)-based bacterial growth potential (BGP) method to assess the biofouling potential in SWRO [...] Read more.

Measuring the bacterial growth potential of seawater reverse osmosis (SWRO) feed water is an issue that is receiving growing attention. This study developed and demonstrated the applicability of the flow-cytometry (FCM)-based bacterial growth potential (BGP) method to assess the biofouling potential in SWRO systems using natural microbial consortium. This method is relatively fast (2–3 days) compared to conventional bioassays. The effect of the potential introduction of nutrients during measurement has been studied thoroughly to achieve the lowest measure value of about 45,000 cells/mL, which is equivalent to about (10 µg-C glucose/L). The BGP method was applied in two full-scale SWRO plants that included (i) dissolved air flotation (DAF) and ultra-filtration (UF); (ii) dual-media filtration (DMF) and cartridge filter (CF), which were compared with the cleaning frequency of the plants. A significant reduction (54%) in BGP was observed through DAF–UF as pre-treatment (with 0.5 mg Fe³⁺/L), while there was a 40% reduction by DMF–CF (with 0.8 mg Fe³⁺/L). In terms of the absolute number, the SWRO feed water after DAF–UF supports 1.5 × 10⁶ cells/mL, which is 1.25 times higher than after DMF–CF. This corresponds to the higher cleaning-in-place (CIP) frequency of SWRO with DAF–UF compared to DMF–CF as pre-treatment, indicating that the BGP method has an added value in monitoring the biofouling potential in SWRO systems. Full article

(This article belongs to the Special Issue Seawater Reverse Osmosis Desalination)

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42 pages, 10984 KB

Open AccessEditor’s ChoiceReview

Strategies in Forward Osmosis Membrane Substrate Fabrication and Modification: A Review

by Nur Diyana Suzaimi, Pei Sean Goh, Ahmad Fauzi Ismail, Stanley Chinedu Mamah, Nik Ahmad Nizam Nik Malek, Jun Wei Lim, Kar Chun Wong and Nidal Hilal

Membranes 2020, 10(11), 332; https://doi.org/10.3390/membranes10110332 - 7 Nov 2020

Cited by 55 | Viewed by 22008

Abstract

Forward osmosis (FO) has been recognized as the preferred alternative membrane-based separation technology for conventional water treatment technologies due to its high energy efficiency and promising separation performances. FO has been widely explored in the fields of wastewater treatment, desalination, food industry and [...] Read more.

Forward osmosis (FO) has been recognized as the preferred alternative membrane-based separation technology for conventional water treatment technologies due to its high energy efficiency and promising separation performances. FO has been widely explored in the fields of wastewater treatment, desalination, food industry and bio-products, and energy generation. The substrate of the typically used FO thin film composite membranes serves as a support for selective layer formation and can significantly affect the structural and physicochemical properties of the resultant selective layer. This signifies the importance of substrate exploration to fine-tune proper fabrication and modification in obtaining optimized substrate structure with regards to thickness, tortuosity, and porosity on the two sides. The ultimate goal of substrate modification is to obtain a thin and highly selective membrane with enhanced hydrophilicity, antifouling propensity, as well as long duration stability. This review focuses on the various strategies used for FO membrane substrate fabrication and modification. An overview of FO membranes is first presented. The extant strategies applied in FO membrane substrate fabrications and modifications in addition to efforts made to mitigate membrane fouling are extensively reviewed. Lastly, the future perspective regarding the strategies on different FO substrate layers in water treatment are highlighted. Full article

(This article belongs to the Special Issue Advances in Nanocomposite Membranes)

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18 pages, 25159 KB

Open AccessFeature PaperEditor’s ChoiceReview

Urine Treatment on the International Space Station: Current Practice and Novel Approaches

by Federico Volpin, Umakant Badeti, Chen Wang, Jiaxi Jiang, Jörg Vogel, Stefano Freguia, Dena Fam, Jaeweon Cho, Sherub Phuntsho and Ho Kyong Shon

Membranes 2020, 10(11), 327; https://doi.org/10.3390/membranes10110327 - 2 Nov 2020

Cited by 53 | Viewed by 11551

Abstract

A reliable, robust, and resilient water recovery system is of paramount importance on board the International Space Station (ISS). Such a system must be able to treat all sources of water, thereby reducing resupply costs and allowing for longer-term space missions. As such, [...] Read more.

A reliable, robust, and resilient water recovery system is of paramount importance on board the International Space Station (ISS). Such a system must be able to treat all sources of water, thereby reducing resupply costs and allowing for longer-term space missions. As such, technologies able to dewater urine in microgravity have been investigated by different space agencies. However, despite over 50 years of research and advancements on water extraction from human urine, the Urine Processing Assembly (UPA) and the Water Processor Assembly (WPA) now operating on the ISS still achieve suboptimal water recovery rates and require periodic consumables resupply. Additionally, urine brine from the treatment is collected for disposal and not yet reused. These factors, combined with the need for a life support system capable of tolerating even dormant periods of up to one year, make the research in this field ever more critical. As such, in the last decade, extensive research was conducted on the adaptation of existing or emerging technologies for the ISS context. In virtue of having a strong chemical resistance, small footprint, tuneable selectivity and versatility, novel membrane-based processes have been in focus for treating human urine. Their hybridisation with thermal and biological processes as well as the combination with new nanomaterials have been particularly investigated. This article critically reviews the UPA and WPA processes currently in operation on the ISS, summarising the research directions and needs, highlighted by major space agencies, necessary for allowing life support for missions outside the Low Earth Orbit (LEO). Additionally, it reviews the technologies recently proposed to improve the performance of the system as well as new concepts to allow for the valorisation of the nutrients in urine or the brine after urine dewatering. Full article

(This article belongs to the Special Issue Membranes for Water, Gas and Ion Separation)

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15 pages, 4574 KB

Open AccessEditor’s ChoiceArticle

Graphene Oxide-Based Membranes for Water Purification Applications: Effect of Plasma Treatment on the Adhesion and Stability of the Synthesized Membranes

by Omer Alnoor, Tahar Laoui, Ahmed Ibrahim, Feras Kafiah, Ghaith Nadhreen, Sultan Akhtar and Zafarullah Khan

Membranes 2020, 10(10), 292; https://doi.org/10.3390/membranes10100292 - 17 Oct 2020

Cited by 25 | Viewed by 6880

Abstract

The adhesion enhancement of graphene oxide (GO) and reduced graphene oxide (rGO) layer in the underlying polyethersulfone (PES) microfiltration membrane is a crucial step towards developing a high-performance membrane for water purification applications. In the present study, we modified the surface of a [...] Read more.

The adhesion enhancement of graphene oxide (GO) and reduced graphene oxide (rGO) layer in the underlying polyethersulfone (PES) microfiltration membrane is a crucial step towards developing a high-performance membrane for water purification applications. In the present study, we modified the surface of a PES microfiltration membrane with plasma treatment (PT) carried out at different times (2, 10, and 20 min). We studied the effect of PT on the adhesion, stability, and performance of the synthesized GO/rGO-PES membranes. The membranes’ surface morphology and chemistry were characterized using atomic force microscopy, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. The membrane performance was evaluated by conducting a diffusion test for potassium chloride (KCl) ions through the synthesized membranes. The results revealed that the 2 min PT enhanced the adhesion and stability of the deposited GO/rGO layer when compared to the other plasma-treated membranes. This was associated with an increase in the KCl ion rejection from ~27% to 57%. Surface morphology analysis at a high magnification was performed for the synthesized membranes before and after the diffusion test. Although the membrane’s rejection was improved, the analysis revealed that the GO layers suffered from micro/nano cracks, which negatively affected the membrane’s overall performance. The use of the rGO layer, however, helped in minimizing the GO cracks and enhanced the KCl ion rejection to approximately 94%. Upon increasing the number of rGO deposition cycles from three to five, the performance of the developed rGO-PES membrane was further improved, as confirmed by the increase in its ion rejection to ~99%. Full article

(This article belongs to the Special Issue Advances in Nanocomposite Membranes)

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40 pages, 1800 KB

Open AccessFeature PaperEditor’s ChoiceReview

Forward Osmosis as Concentration Process: Review of Opportunities and Challenges

by Gaetan Blandin, Federico Ferrari, Geoffroy Lesage, Pierre Le-Clech, Marc Héran and Xavier Martinez-Lladó

Membranes 2020, 10(10), 284; https://doi.org/10.3390/membranes10100284 - 14 Oct 2020

Cited by 90 | Viewed by 13927

Abstract

In the past few years, osmotic membrane systems, such as forward osmosis (FO), have gained popularity as “soft” concentration processes. FO has unique properties by combining high rejection rate and low fouling propensity and can be operated without significant pressure or temperature gradient, [...] Read more.

In the past few years, osmotic membrane systems, such as forward osmosis (FO), have gained popularity as “soft” concentration processes. FO has unique properties by combining high rejection rate and low fouling propensity and can be operated without significant pressure or temperature gradient, and therefore can be considered as a potential candidate for a broad range of concentration applications where current technologies still suffer from critical limitations. This review extensively compiles and critically assesses recent considerations of FO as a concentration process for applications, including food and beverages, organics value added compounds, water reuse and nutrients recovery, treatment of waste streams and brine management. Specific requirements for the concentration process regarding the evaluation of concentration factor, modules and design and process operation, draw selection and fouling aspects are also described. Encouraging potential is demonstrated to concentrate streams more than 20-fold with high rejection rate of most compounds and preservation of added value products. For applications dealing with highly concentrated or complex streams, FO still features lower propensity to fouling compared to other membranes technologies along with good versatility and robustness. However, further assessments on lab and pilot scales are expected to better define the achievable concentration factor, rejection and effective concentration of valuable compounds and to clearly demonstrate process limitations (such as fouling or clogging) when reaching high concentration rate. Another important consideration is the draw solution selection and its recovery that should be in line with application needs (i.e., food compatible draw for food and beverage applications, high osmotic pressure for brine management, etc.) and be economically competitive. Full article

(This article belongs to the Special Issue Membrane Technologies for Resource Recovery)

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13 pages, 4861 KB

Open AccessEditor’s ChoiceCase Report

Pilot-Scale Demonstration of Membrane-Based Nitrogen Recovery from Swine Manure

by Beatriz Molinuevo-Salces, Berta Riaño, Matias B. Vanotti, David Hernández-González and María Cruz García-González

Membranes 2020, 10(10), 270; https://doi.org/10.3390/membranes10100270 - 1 Oct 2020

Cited by 44 | Viewed by 6194

Abstract

Gas-permeable membranes technology presents a high potential for nitrogen (N) recovery from wastewaters rich in ammonia (NH₃). The EU project Ammonia Trapping (AT) is aimed at transferring knowledge from the lab-scale level to on-farm pilot-scale level, using this technology to recover [...] Read more.

Gas-permeable membranes technology presents a high potential for nitrogen (N) recovery from wastewaters rich in ammonia (NH₃). The EU project Ammonia Trapping (AT) is aimed at transferring knowledge from the lab-scale level to on-farm pilot-scale level, using this technology to recover NH₃ from livestock wastewaters. The goal of this study is to report the results of an on-farm pilot-scale demonstration plant using gas-permeable membranes to recover N from raw swine manure. After a setup optimization of the plant, stable, and continuous operation was achieved. The maximum NH₃ recovery rate obtained was 38.20 g NH₃-N m⁻² membrane day⁻¹. This recovery rate was greatly affected by the temperature of the process. In addition to its contribution to NH₃ emissions reduction, this technology contributes to the recovery of nutrients in the form of a concentrated stable ammonium sulphate solution. This solution contained 3.2% of N, which makes it suitable for fertigation. The economic approach revealed an economic feasibility of the technology, resulting in a cost of 2.07 € per kg N recovered. Full article

(This article belongs to the Special Issue Membrane Technologies for Nutrient Recovery)

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18 pages, 5241 KB

Open AccessEditor’s ChoiceArticle

Modelling and Optimisation of Multi-Stage Flash Distillation and Reverse Osmosis for Desalination of Saline Process Wastewater Sources

by Andras Jozsef Toth

Membranes 2020, 10(10), 265; https://doi.org/10.3390/membranes10100265 - 28 Sep 2020

Cited by 93 | Viewed by 13768

Abstract

Nowadays, there is increasing interest in advanced simulation methods for desalination. The two most common desalination methods are multi-stage flash distillation (MSF) and reverse osmosis (RO). Numerous research works have been published on these separations, however their simulation appears to be difficult due [...] Read more.

Nowadays, there is increasing interest in advanced simulation methods for desalination. The two most common desalination methods are multi-stage flash distillation (MSF) and reverse osmosis (RO). Numerous research works have been published on these separations, however their simulation appears to be difficult due to their complexity, therefore continuous improvement is required. The RO, in particular, is difficult to model, because the liquids to be separated also depend specifically on the membrane material. The aim of this study is to model steady-state desalination opportunities of saline process wastewater in flowsheet environment. Commercial flowsheet simulator programs were investigated: ChemCAD for thermal desalination and WAVE program for membrane separation. The calculation of the developed MSF model was verified based on industrial data. It can be stated that both simulators are capable of reducing saline content from 4.5 V/V% to 0.05 V/V%. The simulation results are in accordance with the expectations: MSF has higher yield, but reverse osmosis is simpler process with lower energy demand. The main additional value of the research lies in the comparison of desalination modelling in widely commercially available computer programs. Furthermore, complex functions are established between the optimized operating parameters of multi-stage flash distillation allowing to review trends in flash steps for complete desalination plants. Full article

(This article belongs to the Special Issue Process of Membrane Separation: Comparison with Competing Traditional Processes)

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22 pages, 4327 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Bovine Hemoglobin Enzymatic Hydrolysis by a New Ecoefficient Process—Part I: Feasibility of Electrodialysis with Bipolar Membrane and Production of Neokyotorphin (α137-141)

by Mira Abou-Diab, Jacinthe Thibodeau, Barbara Deracinois, Christophe Flahaut, Ismail Fliss, Pascal Dhulster, Naima Nedjar and Laurent Bazinet

Membranes 2020, 10(10), 257; https://doi.org/10.3390/membranes10100257 - 25 Sep 2020

Cited by 20 | Viewed by 4224

Abstract

Neokyotorphin (α137-141) is recognized as an antimicrobial peptide and a natural meat preservative. It is produced by conventional enzymatic hydrolysis of bovine hemoglobin, a major component of cruor, a by-product of slaughterhouses. However, during conventional hydrolysis, chemical agents are necessary to adjust and [...] Read more.

Neokyotorphin (α137-141) is recognized as an antimicrobial peptide and a natural meat preservative. It is produced by conventional enzymatic hydrolysis of bovine hemoglobin, a major component of cruor, a by-product of slaughterhouses. However, during conventional hydrolysis, chemical agents are necessary to adjust and regulate the pH of the protein solution and the mineral salt content of the final hydrolysate is consequently high. To produce this peptide of interest without chemical agents and with a low salt concentration, electrodialysis with bipolar membrane (EDBM), an electromembrane process recognized as a green process, with two different membrane configurations (cationic (MCP) and anionic (AEM) membranes) was investigated. Hydrolysis in EDBM showed the same enzymatic mechanism, “Zipper”, and allowed the generation of α137-141 in the same concentration as observed in conventional hydrolysis (control). EDBM-MCP allowed the production of hydrolysates containing a low concentration of mineral salts but with fouling formation on MCP, while EDBM-AEM allowed the production of hydrolysates without fouling but with a similar salt concentration than the control. To the best of our knowledge, this was the first time that EDBM was demonstrated as a feasible and innovative technology to produce peptide hydrolysates from enzymatic hydrolysis. Full article

(This article belongs to the Special Issue Membrane Technologies for Sustainable Biofood Production Lines)

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72 pages, 17395 KB

Open AccessEditor’s ChoiceReview

Electrodialytic Processes: Market Overview, Membrane Phenomena, Recent Developments and Sustainable Strategies

by Laurent Bazinet and Thibaud R. Geoffroy

Membranes 2020, 10(9), 221; https://doi.org/10.3390/membranes10090221 - 2 Sep 2020

Cited by 131 | Viewed by 12465

Abstract

In the context of preserving and improving human health, electrodialytic processes are very promising perspectives. Indeed, they allow the treatment of water, preservation of food products, production of bioactive compounds, extraction of organic acids, and recovery of energy from natural and wastewaters without [...] Read more.

In the context of preserving and improving human health, electrodialytic processes are very promising perspectives. Indeed, they allow the treatment of water, preservation of food products, production of bioactive compounds, extraction of organic acids, and recovery of energy from natural and wastewaters without major environmental impact. Hence, the aim of the present review is to give a global portrait of the most recent developments in electrodialytic membrane phenomena and their uses in sustainable strategies. It has appeared that new knowledge on pulsed electric fields, electroconvective vortices, overlimiting conditions and reversal modes as well as recent demonstrations of their applications are currently boosting the interest for electrodialytic processes. However, the hurdles are still high when dealing with scale-ups and real-life conditions. Furthermore, looking at the recent research trends, potable water and wastewater treatment as well as the production of value-added bioactive products in a circular economy will probably be the main applications to be developed and improved. All these processes, taking into account their principles and specificities, can be used for specific eco-efficient applications. However, to prove the sustainability of such process strategies, more life cycle assessments will be necessary to convince people of the merits of coupling these technologies. Full article

(This article belongs to the Special Issue Membrane Technologies for Sustainable Biofood Production Lines)

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21 pages, 1440 KB

Open AccessEditor’s ChoiceReview

A Reevaluation of Chitosan-Decorated Nanoparticles to Cross the Blood-Brain Barrier

by Hernán Cortés, Sergio Alcalá-Alcalá, Isaac H. Caballero-Florán, Sergio A. Bernal-Chávez, Arturo Ávalos-Fuentes, Maykel González-Torres, Manuel González-Del Carmen, Gabriela Figueroa-González, Octavio D. Reyes-Hernández, Benjamín Floran, María L. Del Prado-Audelo and Gerardo Leyva-Gómez

Membranes 2020, 10(9), 212; https://doi.org/10.3390/membranes10090212 - 30 Aug 2020

Cited by 92 | Viewed by 8012

Abstract

The blood-brain barrier (BBB) is a sophisticated and very selective dynamic interface composed of endothelial cells expressing enzymes, transport systems, and receptors that regulate the passage of nutrients, ions, oxygen, and other essential molecules to the brain, regulating its homeostasis. Moreover, the BBB [...] Read more.

The blood-brain barrier (BBB) is a sophisticated and very selective dynamic interface composed of endothelial cells expressing enzymes, transport systems, and receptors that regulate the passage of nutrients, ions, oxygen, and other essential molecules to the brain, regulating its homeostasis. Moreover, the BBB performs a vital function in protecting the brain from pathogens and other dangerous agents in the blood circulation. Despite its crucial role, this barrier represents a difficult obstacle for the treatment of brain diseases because many therapeutic agents cannot cross it. Thus, different strategies based on nanoparticles have been explored in recent years. Concerning this, chitosan-decorated nanoparticles have demonstrated enormous potential for drug delivery across the BBB and treatment of Alzheimer’s disease, Parkinson’s disease, gliomas, cerebral ischemia, and schizophrenia. Our main objective was to highlight the high potential of chitosan adsorption to improve the penetrability through the BBB of nanoformulations for diseases of CNS. Therefore, we describe the BBB structure and function, as well as the routes of chitosan for crossing it. Moreover, we define the methods of decoration of nanoparticles with chitosan and provide numerous examples of their potential utilization in a variety of brain diseases. Lastly, we discuss future directions, mentioning the need for extensive characterization of proposed nanoformulations and clinical trials for evaluation of their efficacy. Full article

(This article belongs to the Special Issue Study on Drug-Membrane Interactions)

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8 pages, 1381 KB

Open AccessEditor’s ChoiceBrief Report

Implications for SARS-CoV-2 Vaccine Design: Fusion of Spike Glycoprotein Transmembrane Domain to Receptor-Binding Domain Induces Trimerization

by Taha Azad, Ragunath Singaravelu, Mathieu J.F. Crupi, Taylor Jamieson, Jaahnavi Dave, Emily E.F. Brown, Reza Rezaei, Zaid Taha, Stephen Boulton, Nikolas T. Martin, Abera Surendran, Joanna Poutou, Mina Ghahremani, Kazem Nouri, Jack T. Whelan, Jessie Duong, Sarah Tucker, Jean-Simon Diallo, John C. Bell and Carolina S. Ilkow

Membranes 2020, 10(9), 215; https://doi.org/10.3390/membranes10090215 - 30 Aug 2020

Cited by 19 | Viewed by 6876

Abstract

The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic presents an urgent need for an effective vaccine. Molecular characterization of SARS-CoV-2 is critical to the development of effective vaccine and therapeutic strategies. In the present study, we show that the fusion of [...] Read more.

The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic presents an urgent need for an effective vaccine. Molecular characterization of SARS-CoV-2 is critical to the development of effective vaccine and therapeutic strategies. In the present study, we show that the fusion of the SARS-CoV-2 spike protein receptor-binding domain to its transmembrane domain is sufficient to mediate trimerization. Our findings may have implications for vaccine development and therapeutic drug design strategies targeting spike trimerization. As global efforts for developing SARS-CoV-2 vaccines are rapidly underway, we believe this observation is an important consideration for identifying crucial epitopes of SARS-CoV-2. Full article

(This article belongs to the Collection Feature Papers in Membranes in Life Sciences)

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35 pages, 3620 KB

Open AccessEditor’s ChoiceReview

Progress on the Fabrication and Application of Electrospun Nanofiber Composites

by Mariela Toriello, Morteza Afsari, Ho Kyong Shon and Leonard D. Tijing

Membranes 2020, 10(9), 204; https://doi.org/10.3390/membranes10090204 - 28 Aug 2020

Cited by 138 | Viewed by 13226

Abstract

Nanofibers are one of the most attractive materials in various applications due to their unique properties and promising characteristics for the next generation of materials in the fields of energy, environment, and health. Among the many fabrication methods, electrospinning is one of the [...] Read more.

Nanofibers are one of the most attractive materials in various applications due to their unique properties and promising characteristics for the next generation of materials in the fields of energy, environment, and health. Among the many fabrication methods, electrospinning is one of the most efficient technologies which has brought about remarkable progress in the fabrication of nanofibers with high surface area, high aspect ratio, and porosity features. However, neat nanofibers generally have low mechanical strength, thermal instability, and limited functionalities. Therefore, composite and modified structures of electrospun nanofibers have been developed to improve the advantages of nanofibers and overcome their drawbacks. The combination of electrospinning technology and high-quality nanomaterials via materials science advances as well as new modification techniques have led to the fabrication of composite and modified nanofibers with desired properties for different applications. In this review, we present the recent progress on the fabrication and applications of electrospun nanofiber composites to sketch a progress line for advancements in various categories. Firstly, the different methods for fabrication of composite and modified nanofibers have been investigated. Then, the current innovations of composite nanofibers in environmental, healthcare, and energy fields have been described, and the improvements in each field are explained in detail. The continued growth of composite and modified nanofiber technology reveals its versatile properties that offer alternatives for many of current industrial and domestic issues and applications. Full article

(This article belongs to the Section Membrane Applications)

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30 pages, 1113 KB

Open AccessEditor’s ChoiceReview

Polymyxins and Bacterial Membranes: A Review of Antibacterial Activity and Mechanisms of Resistance

by Carole Ayoub Moubareck

Membranes 2020, 10(8), 181; https://doi.org/10.3390/membranes10080181 - 8 Aug 2020

Cited by 159 | Viewed by 21137

Abstract

Following their initial discovery in the 1940s, polymyxin antibiotics fell into disfavor due to their potential clinical toxicity, especially nephrotoxicity. However, the dry antibiotic development pipeline, together with the rising global prevalence of infections caused by multidrug-resistant (MDR) Gram-negative bacteria have both rejuvenated [...] Read more.

Following their initial discovery in the 1940s, polymyxin antibiotics fell into disfavor due to their potential clinical toxicity, especially nephrotoxicity. However, the dry antibiotic development pipeline, together with the rising global prevalence of infections caused by multidrug-resistant (MDR) Gram-negative bacteria have both rejuvenated clinical interest in these polypeptide antibiotics. Parallel to the revival of their use, investigations into the mechanisms of action and resistance to polymyxins have intensified. With an initial known effect on biological membranes, research has uncovered the detailed molecular and chemical interactions that polymyxins have with Gram-negative outer membranes and lipopolysaccharide structure. In addition, genetic and epidemiological studies have revealed the basis of resistance to these agents. Nowadays, resistance to polymyxins in MDR Gram-negative pathogens is well elucidated, with chromosomal as well as plasmid-encoded, transferrable pathways. The aims of the current review are to highlight the important chemical, microbiological, and pharmacological properties of polymyxins, to discuss their mechanistic effects on bacterial membranes, and to revise the current knowledge about Gram-negative acquired resistance to these agents. Finally, recent research, directed towards new perspectives for improving these old agents utilized in the 21st century, to combat drug-resistant pathogens, is summarized. Full article

(This article belongs to the Special Issue Membranes: 10th Anniversary)

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22 pages, 4703 KB

Open AccessEditor’s ChoiceReview

Surface Modifications of Anion Exchange Membranes for an Improved Reverse Electrodialysis Process Performance: A Review

by Francis Kotoka, Ivan Merino-Garcia and Svetlozar Velizarov

Membranes 2020, 10(8), 160; https://doi.org/10.3390/membranes10080160 - 22 Jul 2020

Cited by 56 | Viewed by 7330

Abstract

Reverse electrodialysis (RED) technology represents a promising electro-membrane process for renewable energy harvesting from aqueous streams with different salinity. However, the performance of the key components of the system, that is, the ion exchange membranes, is limited by both the presence of multivalent [...] Read more.

Reverse electrodialysis (RED) technology represents a promising electro-membrane process for renewable energy harvesting from aqueous streams with different salinity. However, the performance of the key components of the system, that is, the ion exchange membranes, is limited by both the presence of multivalent ions and fouling phenomena, thus leading to a reduced generated net power density. In this context, the behavior of anion exchange membranes (AEMs) in RED systems is more severely affected, due to the undesirable interactions between their positively charged fixed groups and, mostly negatively charged, foulant materials present in natural streams. Therefore, controlling both the monovalent anion permselectivity and the membrane surface hydrophilicity is crucial. In this respect, different surface modification procedures were considered in the literature, to enhance the above-mentioned properties. This review reports and discusses the currently available approaches for surface modifications of AEMs, such as graft polymerization, dip coating, and layer-by-layer, among others, mainly focusing on preparing monovalent permselective AEMs with antifouling characteristics, but also considering hydrophilicity aspects and identifying the most promising modifying agents to be utilized. Thus, the present study aimed at providing new insights for the further design and development of selective, durable, and cost-effective modified AEMs for an enhanced RED process performance, which is indispensable for a practical implementation of this electro-membrane technology at an industrial scale. Full article

(This article belongs to the Special Issue Modelling and Experiment of Anion-Exchange Membranes)

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22 pages, 4275 KB

Open AccessEditor’s ChoiceArticle

Electrical, Dielectric Property and Electrochemical Performances of Plasticized Silver Ion-Conducting Chitosan-Based Polymer Nanocomposites

by Jihad M. Hadi, Shujahadeen B. Aziz, Muaffaq M. Nofal, Sarkawt A. Hussein, Muhamad H. Hafiz, Mohamad A. Brza, Rebar T. Abdulwahid, Mohd F. Z. Kadir and Haw J. Woo

Membranes 2020, 10(7), 151; https://doi.org/10.3390/membranes10070151 - 13 Jul 2020

Cited by 111 | Viewed by 7263

Abstract

In the present work, chitosan (CS) as a natural biopolymer was used to prepare nanocomposite polymer electrolytes (NCPEs) in order to reduce plastic waste pollution. The plasticized CS-based NCSPE has been prepared via the solution casting technique. The electrical properties of the films [...] Read more.

In the present work, chitosan (CS) as a natural biopolymer was used to prepare nanocomposite polymer electrolytes (NCPEs) in order to reduce plastic waste pollution. The plasticized CS-based NCSPE has been prepared via the solution casting technique. The electrical properties of the films were investigated using AC conductivity, dielectric properties, electric modulus, and electrical impedance spectroscopy (EIS). The obtained results from the dielectric properties and electric modulus study confirm the non-Debye behavior of ion dynamics. The effect of glycerol plasticizer on ionic conductivity of the CS:AgNO₃:Al₂O₃ system was investigated via AC conductivity and impedance studies. The conductivity of the samples was explained based on electrical equivalent circuits and Bode plots. The electrochemical properties such as transfer number measurement (TNM), linear sweep voltammetry (LSV), and cyclic voltammetry (CV) were carried out to inspect the sample suitability for electrochemical double-layer capacitor (EDLC) application. The highest conductivity was 3.7 × 10⁻⁴ S cm⁻¹ with the electrochemical stability window up to 2.1 V at room temperature. Through the TNM study, the ionic conductivity of plasticized CS-based NCSPE was confirmed, and ion transport (t_ion) of the highest conducting sample was found to be 0.985. The activated carbon electrode with the highest conducting sample was employed in the EDLC device fabrication. Accordingly, it can be said that the highest conducting sample had capable performance to be applied in electrochemical device application. Full article

(This article belongs to the Special Issue Polymeric Membrane)

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93 pages, 18781 KB

Open AccessEditor’s ChoiceReview

Electrodialysis Applications in Wastewater Treatment for Environmental Protection and Resources Recovery: A Systematic Review on Progress and Perspectives

by Luigi Gurreri, Alessandro Tamburini, Andrea Cipollina and Giorgio Micale

Membranes 2020, 10(7), 146; https://doi.org/10.3390/membranes10070146 - 9 Jul 2020

Cited by 384 | Viewed by 37296

Abstract

This paper presents a comprehensive review of studies on electrodialysis (ED) applications in wastewater treatment, outlining the current status and the future prospect. ED is a membrane process of separation under the action of an electric field, where ions are selectively transported across [...] Read more.

This paper presents a comprehensive review of studies on electrodialysis (ED) applications in wastewater treatment, outlining the current status and the future prospect. ED is a membrane process of separation under the action of an electric field, where ions are selectively transported across ion-exchange membranes. ED of both conventional or unconventional fashion has been tested to treat several waste or spent aqueous solutions, including effluents from various industrial processes, municipal wastewater or salt water treatment plants, and animal farms. Properties such as selectivity, high separation efficiency, and chemical-free treatment make ED methods adequate for desalination and other treatments with significant environmental benefits. ED technologies can be used in operations of concentration, dilution, desalination, regeneration, and valorisation to reclaim wastewater and recover water and/or other products, e.g., heavy metal ions, salts, acids/bases, nutrients, and organics, or electrical energy. Intense research activity has been directed towards developing enhanced or novel systems, showing that zero or minimal liquid discharge approaches can be techno-economically affordable and competitive. Despite few real plants having been installed, recent developments are opening new routes for the large-scale use of ED techniques in a plethora of treatment processes for wastewater. Full article

(This article belongs to the Special Issue Electromembrane Processes: Experiments and Modelling)

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29 pages, 4785 KB

Open AccessEditor’s ChoiceReview

Recent Developments in Nanomaterials-Modified Membranes for Improved Membrane Distillation Performance

by Saikat Sinha Ray, Harshdeep Singh Bakshi, Raghav Dangayach, Randeep Singh, Chinmoy Kanti Deb, Mahesh Ganesapillai, Shiao-Shing Chen and Mihir Kumar Purkait

Membranes 2020, 10(7), 140; https://doi.org/10.3390/membranes10070140 - 3 Jul 2020

Cited by 100 | Viewed by 11150

Abstract

Membrane distillation (MD) is a thermally induced membrane separation process that utilizes vapor pressure variance to permeate the more volatile constituent, typically water as vapor, across a hydrophobic membrane and rejects the less volatile components of the feed. Permeate flux decline, membrane fouling, [...] Read more.

Membrane distillation (MD) is a thermally induced membrane separation process that utilizes vapor pressure variance to permeate the more volatile constituent, typically water as vapor, across a hydrophobic membrane and rejects the less volatile components of the feed. Permeate flux decline, membrane fouling, and wetting are some serious challenges faced in MD operations. Thus, in recent years, various studies have been carried out on the modification of these MD membranes by incorporating nanomaterials to overcome these challenges and significantly improve the performance of these membranes. This review provides a comprehensive evaluation of the incorporation of new generation nanomaterials such as quantum dots, metalloids and metal oxide-based nanoparticles, metal organic frameworks (MOFs), and carbon-based nanomaterials in the MD membrane. The desired characteristics of the membrane for MD operations, such as a higher liquid entry pressure (LEPw), permeability, porosity, hydrophobicity, chemical stability, thermal conductivity, and mechanical strength, have been thoroughly discussed. Additionally, methodologies adopted for the incorporation of nanomaterials in these membranes, including surface grafting, plasma polymerization, interfacial polymerization, dip coating, and the efficacy of these modified membranes in various MD operations along with their applications are addressed. Further, the current challenges in modifying MD membranes using nanomaterials along with prominent future aspects have been systematically elaborated. Full article

(This article belongs to the Special Issue Membranes: 10th Anniversary)

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56 pages, 600 KB

Open AccessEditor’s ChoiceReview

Membrane-Based Processes Used in Municipal Wastewater Treatment for Water Reuse: State-Of-The-Art and Performance Analysis

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

Membranes 2020, 10(6), 131; https://doi.org/10.3390/membranes10060131 - 25 Jun 2020

Cited by 106 | Viewed by 14147

Abstract

Wastewater reuse as a sustainable, reliable and energy recovery concept is a promising approach to alleviate worldwide water scarcity. However, the water reuse market needs to be developed with long-term efforts because only less than 4% of the total wastewater worldwide has been [...] Read more.

Wastewater reuse as a sustainable, reliable and energy recovery concept is a promising approach to alleviate worldwide water scarcity. However, the water reuse market needs to be developed with long-term efforts because only less than 4% of the total wastewater worldwide has been treated for water reuse at present. In addition, the reclaimed water should fulfill the criteria of health safety, appearance, environmental acceptance and economic feasibility based on their local water reuse guidelines. Moreover, municipal wastewater as an alternative water resource for non-potable or potable reuse, has been widely treated by various membrane-based treatment processes for reuse applications. By collecting lab-scale and pilot-scale reuse cases as much as possible, this review aims to provide a comprehensive summary of the membrane-based treatment processes, mainly focused on the hydraulic filtration performance, contaminants removal capacity, reuse purpose, fouling resistance potential, resource recovery and energy consumption. The advances and limitations of different membrane-based processes alone or coupled with other possible processes such as disinfection processes and advanced oxidation processes, are also highlighted. Challenges still facing membrane-based technologies for water reuse applications, including institutional barriers, financial allocation and public perception, are stated as areas in need of further research and development. Full article

(This article belongs to the Special Issue Membranes for Water Disinfection)

20 pages, 2951 KB

Open AccessEditor’s ChoiceArticle

Metal Complex as a Novel Approach to Enhance the Amorphous Phase and Improve the EDLC Performance of Plasticized Proton Conducting Chitosan-Based Polymer Electrolyte

by Ahmad S. F. M. Asnawi, Shujahadeen B. Aziz, Muaffaq M. Nofal, Yuhanees M. Yusof, Iver Brevik, Muhamad H. Hamsan, Mohamad A. Brza, Rebar T. Abdulwahid and Mohd F. Z. Kadir

Membranes 2020, 10(6), 132; https://doi.org/10.3390/membranes10060132 - 25 Jun 2020

Cited by 65 | Viewed by 5077

Abstract

This work indicates that glycerolized chitosan-NH₄F polymer electrolytes incorporated with zinc metal complexes are crucial for EDLC application. The ionic conductivity of the plasticized system was improved drastically from 9.52 × 10⁻⁴ S/cm to 1.71 × 10⁻³ S/cm with [...] Read more.

This work indicates that glycerolized chitosan-NH₄F polymer electrolytes incorporated with zinc metal complexes are crucial for EDLC application. The ionic conductivity of the plasticized system was improved drastically from 9.52 × 10⁻⁴ S/cm to 1.71 × 10⁻³ S/cm with the addition of a zinc metal complex. The XRD results demonstrated that the amorphous phase was enhanced for the system containing the zinc metal complex. The transference number of ions (t_ion) and electrons (t_e) were measured for two of the highest conducting electrolyte systems. It confirmed that the ions were the dominant charge carriers in both systems as t_ion values for CSNHG4 and CSNHG5 electrolytes were 0.976 and 0.966, respectively. From the examination of LSV, zinc improved the electrolyte electrochemical stability to 2.25 V. The achieved specific capacitance from the CV plot reveals the role of the metal complex on storage properties. The charge–discharge profile was obtained for the system incorporated with the metal complex. The obtained specific capacitance ranged from 69.7 to 77.6 F/g. The energy and power densities became stable from 7.8 to 8.5 Wh/kg and 1041.7 to 248.2 W/kg, respectively, as the EDLC finalized the cycles. Full article

(This article belongs to the Special Issue Polymeric Membrane)

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17 pages, 18670 KB

Open AccessEditor’s ChoiceArticle

Diffusion Dialysis for Separation of Hydrochloric Acid, Iron and Zinc Ions from Highly Concentrated Pickling Solutions

by Rosa Gueccia, Alba Ruiz Aguirre, Serena Randazzo, Andrea Cipollina and Giorgio Micale

Membranes 2020, 10(6), 129; https://doi.org/10.3390/membranes10060129 - 24 Jun 2020

Cited by 32 | Viewed by 7029

Abstract

Acid recovery from pickling waste solutions is an important step to enhance hot-dip-galvanizing industry process sustainability. Diffusion dialysis (DD) can be used to separate acids and heavy metals (e.g., iron and zinc) from pickling waters, promoting the circular use of such raw materials. [...] Read more.

Acid recovery from pickling waste solutions is an important step to enhance hot-dip-galvanizing industry process sustainability. Diffusion dialysis (DD) can be used to separate acids and heavy metals (e.g., iron and zinc) from pickling waters, promoting the circular use of such raw materials. In the present study, a laboratory scale unit operating in batch and a continuous large scale unit, both equipped with Fumasep anionic exchange membranes, were tested. Results obtained show that zinc and iron concentration affect the HCl recovery in opposite ways. Iron chlorides enhance acid recovery, while zinc chlorides considerably tend to diffuse through the membrane because of negatively charged chloro-complexes formation and slightly reduce the acid diffusion. A multi-components mathematical model, with a time-dependent and distributed-parameters architecture, was adopted enabling the prediction of operations with hydrochloric acid, zinc, and iron metals both in batch and in continuous dialyzers. As a result, a good comparison between model simulations and experiments was achieved in both configurations. Full article

(This article belongs to the Special Issue Membrane Technologies for Resource Recovery)

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24 pages, 14297 KB

Open AccessEditor’s ChoiceReview

Solid-Contact Ion-Selective Electrodes: Response Mechanisms, Transducer Materials and Wearable Sensors

by Yan Lyu, Shiyu Gan, Yu Bao, Lijie Zhong, Jianan Xu, Wei Wang, Zhenbang Liu, Yingming Ma, Guifu Yang and Li Niu

Membranes 2020, 10(6), 128; https://doi.org/10.3390/membranes10060128 - 23 Jun 2020

Cited by 131 | Viewed by 15232

Abstract

Wearable sensors based on solid-contact ion-selective electrodes (SC-ISEs) are currently attracting intensive attention in monitoring human health conditions through real-time and non-invasive analysis of ions in biological fluids. SC-ISEs have gone through a revolution with improvements in potential stability and reproducibility. The introduction [...] Read more.

Wearable sensors based on solid-contact ion-selective electrodes (SC-ISEs) are currently attracting intensive attention in monitoring human health conditions through real-time and non-invasive analysis of ions in biological fluids. SC-ISEs have gone through a revolution with improvements in potential stability and reproducibility. The introduction of new transducing materials, the understanding of theoretical potentiometric responses, and wearable applications greatly facilitate SC-ISEs. We review recent advances in SC-ISEs including the response mechanism (redox capacitance and electric-double-layer capacitance mechanisms) and crucial solid transducer materials (conducting polymers, carbon and other nanomaterials) and applications in wearable sensors. At the end of the review we illustrate the existing challenges and prospects for future SC-ISEs. We expect this review to provide readers with a general picture of SC-ISEs and appeal to further establishing protocols for evaluating SC-ISEs and accelerating commercial wearable sensors for clinical diagnosis and family practice. Full article

(This article belongs to the Special Issue Advances in Artificial and Biological Membranes: Mechanisms of Ionic Sensitivity, Ion-Sensor Designs and Applications for Ions Measurement)

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17 pages, 5141 KB

Open AccessEditor’s ChoiceArticle

Development of Hydrophilic PVDF Membrane Using Vapour Induced Phase Separation Method for Produced Water Treatment

by Normi Izati Mat Nawi, Ho Min Chean, Norazanita Shamsuddin, Muhammad Roil Bilad, Thanitporn Narkkun, Kajornsak Faungnawakij and Asim Laeeq Khan

Membranes 2020, 10(6), 121; https://doi.org/10.3390/membranes10060121 - 16 Jun 2020

Cited by 95 | Viewed by 10718

Abstract

During the production of oil and gas, a large amount of oily wastewater is generated, which would pollute the environment if discharged without proper treatment. As one of the most promising treatment options, membrane material used for oily wastewater treatment should possess desirable [...] Read more.

During the production of oil and gas, a large amount of oily wastewater is generated, which would pollute the environment if discharged without proper treatment. As one of the most promising treatment options, membrane material used for oily wastewater treatment should possess desirable properties of high hydraulic performance combined with high membrane fouling resistance. This project employs the vapor induced phase separation (VIPS) technique to develop a hydrophilic polyvinylidene fluoride (PVDF) membrane with polyethylene glycol (PEG) as an additive for produced water treatment. Results show that thanks to its slow nonsolvent intake, the VIPS method hinders additive leaching during the cast film immersion. The results also reveal that the exposure of the film to the open air before immersion greatly influences the structure of the developed membranes. By extending the exposure time from 0 to 30 min, the membrane morphology change from typical asymmetric with large macrovoids to the macrovoid-free porous symmetric membrane with a granular structure, which corresponds to 35% increment of steady-state permeability to 189 L·m⁻²h⁻¹bar⁻¹, while maintaining >90% of oil rejection. It was also found that more PEG content resides in the membrane matrix when the exposure time is extended, contributes to the elevation of surface hydrophilicity, which improves the membrane antifouling properties. Overall results demonstrate the potential of VIPS method for the fabrication of hydrophilic PVDF membrane by helping to preserve hydrophilic additive in the membrane matrices. Full article

(This article belongs to the Special Issue Organic–Inorganic Hybrid Membranes for Separation and Purification Applications)

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16 pages, 2094 KB

Open AccessEditor’s ChoiceArticle

Electrochemical Characteristics of Glycerolized PEO-Based Polymer Electrolytes

by Muhammad S. Mustafa, Hewa O. Ghareeb, Shujahadeen B. Aziz, M. A. Brza, Shakhawan Al-Zangana, Jihad M. Hadi and M. F. Z. Kadir

Membranes 2020, 10(6), 116; https://doi.org/10.3390/membranes10060116 - 5 Jun 2020

Cited by 66 | Viewed by 5627

Abstract

In this article, poly(ethylene oxide)-based polymer electrolyte films doped with ammonium iodide (NH₄I) and plasticized with glycerol were provided by a solution casting method. In the unplasticized system, the maximum ionic conductivity of

3.96 \times 10^{- 5}

S cm [...] Read more.

In this article, poly(ethylene oxide)-based polymer electrolyte films doped with ammonium iodide (NH₄I) and plasticized with glycerol were provided by a solution casting method. In the unplasticized system, the maximum ionic conductivity of

3.96 \times 10^{- 5}

S cm⁻¹ was achieved by the electrolyte comprised of 70 wt. % PEO:30 wt. % NH₄I. The conductivity was further enhanced up to

(1.77 \times 10^{- 4}

S cm⁻¹) for the plasticized system when 10 wt. % glycerol was added to the highest conducting unplasticized one at ambient temperature. The films were characterized by various techniques to evaluate their electrochemical performance. The results of impedance spectroscopy revealed that bulk resistance (R_b) considerably decreased for the highest plasticized polymer electrolyte. The dielectric properties and electric modulus parameters were studied in detail. The LSV analysis verified that the plasticized system can be used in energy storage devices with electrochemical stability up to 1.09 V and the TNM data elucidated that the ions were the main charge carrier. The values of the ion transference number (t_ion) and electron transfer number (t_el) were calculated. The nonappearance of any redox peaks in the cyclic voltammograms indicated that the chemical reaction had not occurred at the electrode/electrolyte interface. Full article

(This article belongs to the Special Issue Electromembrane Processes: Emerging Applications, Materials and Process Configurations)

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55 pages, 13892 KB

Open AccessEditor’s ChoiceReview

Metal and Covalent Organic Frameworks for Membrane Applications

by Mingyuan Fang, Carmen Montoro and Mona Semsarilar

Membranes 2020, 10(5), 107; https://doi.org/10.3390/membranes10050107 - 22 May 2020

Cited by 56 | Viewed by 13061

Abstract

Better and more efficient membranes are needed to face imminent and future scientific, technological and societal challenges. New materials endowed with enhanced properties are required for the preparation of such membranes. Metal and Covalent Organic Frameworks (MOFs and COFs) are a new class [...] Read more.

Better and more efficient membranes are needed to face imminent and future scientific, technological and societal challenges. New materials endowed with enhanced properties are required for the preparation of such membranes. Metal and Covalent Organic Frameworks (MOFs and COFs) are a new class of crystalline porous materials with large surface area, tuneable pore size, structure, and functionality, making them a perfect candidate for membrane applications. In recent years an enormous number of articles have been published on the use of MOFs and COFs in preparation of membranes for various applications. This review gathers the work reported on the synthesis and preparation of membranes containing MOFs and COFs in the last 10 years. Here we give an overview on membranes and their use in separation technology, discussing the essential factors in their synthesis as well as their limitations. A full detailed summary of the preparation and characterization methods used for MOF and COF membranes is given. Finally, applications of these membranes in gas and liquid separation as well as fuel cells are discussed. This review is aimed at both experts in the field and newcomers, including students at both undergraduate and postgraduate levels, who would like to learn about preparation of membranes from crystalline porous materials. Full article

(This article belongs to the Special Issue Membranes: 10th Anniversary)

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17 pages, 3033 KB

Open AccessEditor’s ChoiceReview

The Role of New Inorganic Materials in Composite Membranes for Water Disinfection

by Roberto Castro-Muñoz

Membranes 2020, 10(5), 101; https://doi.org/10.3390/membranes10050101 - 14 May 2020

Cited by 53 | Viewed by 6255

Abstract

Today, there is an increasing interest in improving the physicochemical properties of polymeric membranes by merging the membranes with different inorganic materials. These so-called composite membranes have been implemented in different membrane-based technologies (e.g., microfiltration, ultrafiltration, nanofiltration, membrane bioreactors, among others) for water [...] Read more.

Today, there is an increasing interest in improving the physicochemical properties of polymeric membranes by merging the membranes with different inorganic materials. These so-called composite membranes have been implemented in different membrane-based technologies (e.g., microfiltration, ultrafiltration, nanofiltration, membrane bioreactors, among others) for water treatment and disinfection. This is because such inorganic materials (such as TiO₂-, ZnO-, Ag-, and Cu-based nanoparticles, carbon-based materials, to mention just a few) can improve the separation performance of membranes and also some other properties, such as antifouling, mechanical, thermal, and physical and chemical stability. Moreover, such materials display specific biological activity towards viruses, bacteria, and protozoa, showing enhanced water disinfection properties. Therefore, the aim of this review is to collect the latest advances (in the last five years) in using composite membranes and new hybrid materials for water disinfection, paying particular emphasis on relevant results and new hydride composites together with their preparation protocols. Moreover, this review addresses the main mechanism of action of different conventional and novel inorganic materials toward biologically active matter. Full article

(This article belongs to the Special Issue Membranes for Water Disinfection)

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18 pages, 2840 KB

Open AccessEditor’s ChoiceReview

New Perspectives on Fuel Cell Technology: A Brief Review

by Norazlianie Sazali, Wan Norharyati Wan Salleh, Ahmad Shahir Jamaludin and Mohd Nizar Mhd Razali

Membranes 2020, 10(5), 99; https://doi.org/10.3390/membranes10050099 - 13 May 2020

Cited by 382 | Viewed by 31129

Abstract

Energy storage and conversion is a very important link between the steps of energy production and energy consumption. Traditional fossil fuels are a natural and unsustainable energy storage medium with limited reserves and notorious pollution problems, therefore demanding a better choice to store [...] Read more.

Energy storage and conversion is a very important link between the steps of energy production and energy consumption. Traditional fossil fuels are a natural and unsustainable energy storage medium with limited reserves and notorious pollution problems, therefore demanding a better choice to store and utilize the green and renewable energies in the future. Energy and environmental problems require a clean and efficient way of using the fuels. Fuel cell functions to efficiently convert oxidant and chemical energy accumulated in the fuel directly into DC electric, with the by-products of heat and water. Fuel cells, which are known as effective electrochemical converters, and electricity generation technology has gained attention due to the need for clean energy, the limitation of fossil fuel resources and the capability of a fuel cell to generate electricity without involving any moving mechanical part. The fuel cell technologies that received high interest for commercialization are polymer electrolyte membrane fuel cells (PEMFCs), solid oxide fuel cells (SOFCs), and direct methanol fuel cells (DMFCs). The optimum efficiency for the fuel cell is not bound by the principle of Carnot cycle compared to other traditional power machines that are generally based on thermal cycles such as gas turbines, steam turbines and internal combustion engines. However, the fuel cell applications have been restrained by the high cost needed to commercialize them. Researchers currently focus on the discovery of different materials and manufacturing methods to enhance fuel cell performance and simplify components of fuel cells. Fuel cell systems’ designs are utilized to reduce the costs of the membrane and improve cell efficiency, durability and reliability, allowing them to compete with the traditional combustion engine. In this review, we primarily analyze recent developments in fuel cells technologies and up-to-date modeling for PEMFCs, SOFCs and DMFCs. Full article

(This article belongs to the Special Issue Ionic Conductive Membranes for Fuel Cells)

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28 pages, 5265 KB

Open AccessEditor’s ChoiceReview

Towards Electrochemical Water Desalination Techniques: A Review on Capacitive Deionization, Membrane Capacitive Deionization and Flow Capacitive Deionization

by Gbenro Folaranmi, Mikhael Bechelany, Philippe Sistat, Marc Cretin and Francois Zaviska

Membranes 2020, 10(5), 96; https://doi.org/10.3390/membranes10050096 - 12 May 2020

Cited by 111 | Viewed by 16723

Abstract

Electrochemical water desalination has been a major research area since the 1960s with the development of capacitive deionization technique. For the latter, its modus operandi lies in temporary salt ion adsorption when a simple potential difference (1.0–1.4 V) of about 1.2 V is [...] Read more.

Electrochemical water desalination has been a major research area since the 1960s with the development of capacitive deionization technique. For the latter, its modus operandi lies in temporary salt ion adsorption when a simple potential difference (1.0–1.4 V) of about 1.2 V is supplied to the system to temporarily create an electric field that drives the ions to their different polarized poles and subsequently desorb these solvated ions when potential is switched off. Capacitive deionization targets/extracts the solutes instead of the solvent and thus consumes less energy and is highly effective for brackish water. This paper reviews Capacitive Deionization (mechanism of operation, sustainability, optimization processes, and shortcomings) with extension to its counterparts (Membrane Capacitive Deionization and Flow Capacitive Deionization). Full article

(This article belongs to the Section Membrane Processing and Engineering)

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28 pages, 2922 KB

Open AccessEditor’s ChoiceReview

Membrane Technologies in Wastewater Treatment: A Review

by Elorm Obotey Ezugbe and Sudesh Rathilal

Membranes 2020, 10(5), 89; https://doi.org/10.3390/membranes10050089 - 30 Apr 2020

Cited by 1188 | Viewed by 64788

Abstract

In the face of water shortages, the world seeks to explore all available options in reducing the over exploitation of limited freshwater resources. One of the surest available water resources is wastewater. As the population grows, industrial, agricultural, and domestic activities increase accordingly [...] Read more.

In the face of water shortages, the world seeks to explore all available options in reducing the over exploitation of limited freshwater resources. One of the surest available water resources is wastewater. As the population grows, industrial, agricultural, and domestic activities increase accordingly in order to cater for the voluminous needs of man. These activities produce large volumes of wastewater from which water can be reclaimed to serve many purposes. Over the years, conventional wastewater treatment processes have succeeded to some extent in treating effluents for discharge purposes. However, improvements in wastewater treatment processes are necessary in order to make treated wastewater re-usable for industrial, agricultural, and domestic purposes. Membrane technology has emerged as a favorite choice for reclaiming water from different wastewater streams for re-use. This review looks at the trending membrane technologies in wastewater treatment, their advantages and disadvantages. It also discusses membrane fouling, membrane cleaning, and membrane modules. Finally, recommendations for future research pertaining to the application of membrane technology in wastewater treatment are made. Full article

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25 pages, 6860 KB

Open AccessEditor’s ChoiceArticle

Polyimide/Ionic Liquid Composite Membranes for Middle and High Temperature Fuel Cell Application: Water Sorption Behavior and Proton Conductivity

by Kateryna Fatyeyeva, Sergiy Rogalsky, Stanislav Makhno, Oksana Tarasyuk, Jorge Arturo Soto Puente and Stéphane Marais

Membranes 2020, 10(5), 82; https://doi.org/10.3390/membranes10050082 - 28 Apr 2020

Cited by 31 | Viewed by 5238

Abstract

Four water insoluble room-temperature protic ionic liquids (PILs) based on the N-alkylimidazolium cation with the alkyl chain length from 1 to 4 and bis(trifluoromethylsulfonyl)imide anion were synthesized and their chemical structure was confirmed by the ¹H NMR and ¹⁹F NMR [...] Read more.

Four water insoluble room-temperature protic ionic liquids (PILs) based on the N-alkylimidazolium cation with the alkyl chain length from 1 to 4 and bis(trifluoromethylsulfonyl)imide anion were synthesized and their chemical structure was confirmed by the ¹H NMR and ¹⁹F NMR analysis. PILs were revealed to be thermally stable up to 360 and 400 °C. At the same time, the proton conductivity of PILs was found to be dependent mostly on the temperature and, to a less extent, on the type of the cation, i.e., the increase of the conductivity from ~3 × 10⁻⁴ S/cm at 25 °C to 2 × 10⁻² S/cm at 150 °C was observed. The water vapour sorption capacity of PILs was evaluated as a function of relative humidity and the influence of the alkyl chain length on the phase behaviour in the PIL-water system was discussed. The composite polyimide/PILs membranes were prepared by the PIL immobilization in the porous polymer (Matrimid^® 5218) film. The composite membranes showed a high level of proton conductivity (~10⁻³ S/cm) at elevated temperatures (up to 160 °C). The obtained results reveal that the elaborated composite polyimide/PIL membranes are promising candidates for the application as proton exchange membrane at middle and high temperatures. Full article

(This article belongs to the Special Issue Membranes: 10th Anniversary)

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17 pages, 4794 KB

Open AccessEditor’s ChoiceArticle

Oily Wastewater Treatment Using Polyamide Thin Film Composite Membrane Technology

by Sarah Elhady, Mohamed Bassyouni, Ramadan A. Mansour, Medhat H. Elzahar, Shereen Abdel-Hamid, Yasser Elhenawy and Mamdou Y. Saleh

Membranes 2020, 10(5), 84; https://doi.org/10.3390/membranes10050084 - 28 Apr 2020

Cited by 59 | Viewed by 8144

Abstract

In this study, polyamide (PA) thin film composite (TFC) reverse osmosis (RO) membrane filtration was used in edible oil wastewater emulsion treatment. The PA-TFC membrane was characterized using mechanical, thermal, chemical, and physical tests. Surface morphology and cross-sections of TFCs were characterized using [...] Read more.

In this study, polyamide (PA) thin film composite (TFC) reverse osmosis (RO) membrane filtration was used in edible oil wastewater emulsion treatment. The PA-TFC membrane was characterized using mechanical, thermal, chemical, and physical tests. Surface morphology and cross-sections of TFCs were characterized using SEM. The effects of edible oil concentrations, average droplets size, and contact angle on separation efficiency and flux were studied in detail. Purification performance was enhanced using activated carbon as a pre-treatment unit. The performance of the RO unit was assessed by chemical oxygen demand (COD) removal and permeate flux. Oil concentration in wastewater varied between 3000 mg/L and 6000 mg/L. Oily wastewater showed a higher contact angle (62.9°) than de-ionized water (33°). Experimental results showed that the presence of activated carbon increases the permeation COD removal from 94% to 99%. The RO membrane filtration coupled with an activated carbon unit of oily wastewater is a convenient hybrid technique for removal of high-concentration edible oil wastewater emulsion up to 99%. Using activated carbon as an adsorption pre-treatment unit improved the permeate flux from 34 L/m²hr to 75 L/m²hr. Full article

(This article belongs to the Special Issue Membranes: 10th Anniversary)

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22 pages, 5956 KB

Open AccessEditor’s ChoiceArticle

Experimental Investigation of the Effect of Implanting TiO₂-NPs on PVC for Long-Term UF Membrane Performance to Treat Refinery Wastewater

by Faris H. Al-Ani, Qusay F. Alsalhy, Rawia Subhi Raheem, Khalid T. Rashid and Alberto Figoli

Membranes 2020, 10(4), 77; https://doi.org/10.3390/membranes10040077 - 21 Apr 2020

Cited by 76 | Viewed by 4848

Abstract

This study investigated the impact of implanting TiO₂-NPs within a membrane to minimize the influence of long-term operation on the membrane characteristics. Four poly vinyle chloride-titanium oxide (PVC-TiO₂-NPs) membranes were prepared to create an ultrafiltration membrane (UF) that would [...] Read more.

This study investigated the impact of implanting TiO₂-NPs within a membrane to minimize the influence of long-term operation on the membrane characteristics. Four poly vinyle chloride-titanium oxide (PVC-TiO₂-NPs) membranes were prepared to create an ultrafiltration membrane (UF) that would effectively treat actual refinery wastewater. The hypothesis of this work was that TiO₂-NPs would function as a hydrophilic modification of the PVC membrane and excellent self-cleaning material, which in turn would greatly extend the membrane’s lifetime. The membranes were characterized via Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray (EDX), atomic force microscope (AFM), and scanning electron microscope (SEM). The removal efficiency of turbidity, total suspended solid (TSS), oil and grease, heavy metals and chemical oxygen demand (COD) were investigated. Contact angle (CA) reduced by 12.7% and 27.5% on the top and bottom surfaces, respectively. The PVC membrane with TiO₂-NPs had larger mean pore size on its surface and more holes with larger size inside the membrane structure. The addition of TiO₂-NPs could remarkably enhance the antifouling property of the PVC membrane. The pure water permeability (PWP) of the membrane was enhanced by 95.3% with an increase of TiO₂ to 1.5 gm/100gm. The PWP after backwashing was reduced from 22.3% for PVC to 10.1% with 1.5 gm TiO₂-NPs. The long-term performance was improved from five days for PVC to 23 d with an increase in TiO₂-NPs to 1.5 gm. The improvements of PVC-TiO₂-NPs long-term were related to the enhancement of the hydrophilic character of the membrane and increase tensile strength due to the reinforcement effect of TiO₂-NPs. These results clearly identify the impact of the TiO₂-NPs content on the long-term PVC/TiO₂-NPs performance and confirm our hypothesis that it is possible to use TiO₂-NPs to effectively enhance the lifetime of membranes during their long-term operation. Full article

(This article belongs to the Special Issue Membrane Preparation and Characterisation and Their Application in Environmental Field (Volume II))

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13 pages, 2118 KB

Open AccessEditor’s ChoiceArticle

Enhanced O₂/N₂ Separation of Mixed-Matrix Membrane Filled with Pluronic-Compatibilized Cobalt Phthalocyanine Particles

by S. A. S. C. Samarasinghe, Chong Yang Chuah, H. Enis Karahan, G. S. M. D. P. Sethunga and Tae-Hyun Bae

Membranes 2020, 10(4), 75; https://doi.org/10.3390/membranes10040075 - 18 Apr 2020

Cited by 27 | Viewed by 7134

Abstract

Membrane-based air separation (O₂/N₂) is of great importance owing to its energy efficiency as compared to conventional processes. Currently, dense polymeric membranes serve as the main pillar of industrial processes used for the generation of O₂- and [...] Read more.

Membrane-based air separation (O₂/N₂) is of great importance owing to its energy efficiency as compared to conventional processes. Currently, dense polymeric membranes serve as the main pillar of industrial processes used for the generation of O₂- and N₂-enriched gas. However, conventional polymeric membranes often fail to meet the selectivity needs owing to the similarity in the effective diameters of O₂ and N₂ gases. Meanwhile, mixed-matrix membranes (MMMs) are convenient to produce high-performance membranes while keeping the advantages of polymeric materials. Here, we propose a novel MMM for O₂/N₂ separation, which is composed of Matrimid^® 5218 (Matrimid) as the matrix, cobalt(II) phthalocyanine microparticles (CoPCMPs) as the filler, and Pluronic^® F-127 (Pluronic) as the compatibilizer. By the incorporation of CoPCMPs to Matrimid, without Pluronic, interfacial defects were formed. Pluronic-treated CoPCMPs, on the other hand, enhanced O₂ permeability and O₂/N₂ selectivity by 64% and 34%, respectively. We explain the enhancement achieved with the increase of both O₂ diffusivity and O₂/N₂ solubility selectivity. Full article

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

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17 pages, 4494 KB

Open AccessEditor’s ChoiceArticle

Leveraging Nanocrystal HKUST-1 in Mixed-Matrix Membranes for Ethylene/Ethane Separation

by Chong Yang Chuah, S.A.S.C. Samarasinghe, Wen Li, Kunli Goh and Tae-Hyun Bae

Membranes 2020, 10(4), 74; https://doi.org/10.3390/membranes10040074 - 16 Apr 2020

Cited by 45 | Viewed by 7425

Abstract

The energy-intensive ethylene/ethane separation process is a key challenge to the petrochemical industry. HKUST-1, a metal–organic framework (MOF) which possesses high accessible surface area and porosity, is utilized in mixed-matrix membrane fabrication to investigate its potential for improving the performance for C₂ [...] Read more.

The energy-intensive ethylene/ethane separation process is a key challenge to the petrochemical industry. HKUST-1, a metal–organic framework (MOF) which possesses high accessible surface area and porosity, is utilized in mixed-matrix membrane fabrication to investigate its potential for improving the performance for C₂H₄/C₂H₆ separation. Prior to membrane fabrication and gas permeation analysis, nanocrystal HKUST-1 was first synthesized. This step is critical in order to ensure that defect-free mixed-matrix membranes can be formed. Then, polyimide-based polymers, ODPA-TMPDA and 6FDA-TMPDA, were chosen as the matrices. Our findings revealed that 20 wt% loading of HKUST-1 was capable of improving C₂H₄ permeability (155% for ODPA-TMPDA and 69% for 6FDA-TMPDA) without excessively sacrificing the C₂H₄/C₂H₆ selectivity. The C₂H₄ and C₂H₆ diffusivity, as well as solubility, were also improved substantially as compared to the pure polymeric membranes. Overall, our results edge near the upper bound, confirming the effectiveness of leveraging nanocrystal HKUST-1 filler for performance enhancements in mixed-matrix membranes for C₂H₄/C₂H₆ separation. Full article

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

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25 pages, 7729 KB

Open AccessEditor’s ChoiceArticle

Structural, Morphological, Electrical and Electrochemical Properties of PVA: CS-Based Proton-Conducting Polymer Blend Electrolytes

by Ayub Shahab Marf, Ranjdar M. Abdullah and Shujahadeen B. Aziz

Membranes 2020, 10(4), 71; https://doi.org/10.3390/membranes10040071 - 15 Apr 2020

Cited by 93 | Viewed by 5392

Abstract

Polymer blend electrolytes based on poly(vinyl alcohol):chitosan (PVA:CS) incorporated with various quantities of ammonium iodide were prepared and characterized using a range of electrochemical, structural and microscopic techniques. In the structural analysis, X-ray diffraction (XRD) was used to confirm the buildup of the [...] Read more.

Polymer blend electrolytes based on poly(vinyl alcohol):chitosan (PVA:CS) incorporated with various quantities of ammonium iodide were prepared and characterized using a range of electrochemical, structural and microscopic techniques. In the structural analysis, X-ray diffraction (XRD) was used to confirm the buildup of the amorphous phase. To reveal the effect of dopant addition on structural changes, field-emission scanning electron microscope (FESEM) was used. The protrusions of salt aggregates with large quantity were seen at the surface of the formed films at 50 wt.% of the added salt. The nature of the relationship between conductivity and dielectric properties was shown using electrochemical impedance spectroscopy (EIS). The EIS spectra were fitted with electrical equivalent circuits (EECs). It was observed that both dielectric constant and dielectric loss were high in the low-frequency region. For all samples, loss tangent and electric modulus plots were analyzed to become familiar with the relaxation behavior. Linear sweep voltammetry (LSV) and transference number measurement (TNM) were recorded. A relatively high cut-off potential for the polymer electrolyte was obtained at 1.33 V and both values of the transference number for ion (t_ion) and electronic (t_elec) showed the ion dominant as charge carrier species. The TNM and LSV measurements indicate the suitability of the samples for energy storage application if their conductivity can be more enhanced. Full article

(This article belongs to the Special Issue Ionic Conductive Membranes for Fuel Cells)

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Open AccessEditor’s ChoiceArticle

Treatment of Cyanide-Free Wastewater from Brass Electrodeposition with EDTA by Electrodialysis: Evaluation of Underlimiting and Overlimiting Operations

by Kayo Santana Barros, Tatiana Scarazzato, Valentín Pérez-Herranz and Denise Crocce Romano Espinosa

Membranes 2020, 10(4), 69; https://doi.org/10.3390/membranes10040069 - 11 Apr 2020

Cited by 25 | Viewed by 5071

Abstract

Growing environmental concerns have led to the development of cleaner processes, such as the substitution of cyanide in electroplating industries and changes in the treatment of wastewaters. Hence, we evaluated the treatment of cyanide-free wastewater from the brass electroplating industry with EDTA as [...] Read more.

Growing environmental concerns have led to the development of cleaner processes, such as the substitution of cyanide in electroplating industries and changes in the treatment of wastewaters. Hence, we evaluated the treatment of cyanide-free wastewater from the brass electroplating industry with EDTA as a complexing agent by electrodialysis, aimed at recovering water and concentrated solutions for reuse. The electrodialysis tests were performed in underlimiting and overlimiting conditions. The results suggested that intense water dissociation occurred at the cathodic side of the commercial anion-exchange membrane (HDX) during the overlimiting test. Consequently, the pH reduction at this membrane may have led to the reaction of protons with complexes of EDTA-metals and insoluble species. This allowed the migration of free Cu²⁺ and Zn²⁺ to the cation-exchange membrane as a result of the intense electric field and electroconvection. These overlimiting phenomena accounted for the improvement of the percent extraction and percent concentration, since in the electrodialysis stack employed herein, the concentrate compartments of cationic and anionic species were connected to the same reservoir. Chronopotentiometric studies showed that electroconvective vortices minimized fouling/scaling at both membranes. The electrodialysis in the overlimiting condition seemed to be more advantageous due to water dissociation and electroconvection. Full article

(This article belongs to the Special Issue Electromembrane Processes: Emerging Applications, Materials and Process Configurations)

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