Membranes

15 pages, 13373 KiB

Open AccessArticle

Calcium Sulfate and Calcium Carbonate Scaling of Thin-Film Composite Polyamide Reverse Osmosis Membranes with Surface-Tethered Polyacrylic Acid Chains

by Yian Chen and Yoram Cohen

Membranes 2022, 12(12), 1287; https://doi.org/10.3390/membranes12121287 - 19 Dec 2022

Cited by 5 | Viewed by 1642

Abstract

The gypsum and calcite scaling propensities of the thin-film composite polyamide (PA-TFC) reverse osmosis (RO) membrane, modified with a tethered surface layer of polyacrylic acid (PAA) chains, was evaluated and compared to the scaling of selected commercial RO membranes. The tethered PAA layer [...] Read more.

The gypsum and calcite scaling propensities of the thin-film composite polyamide (PA-TFC) reverse osmosis (RO) membrane, modified with a tethered surface layer of polyacrylic acid (PAA) chains, was evaluated and compared to the scaling of selected commercial RO membranes. The tethered PAA layer was synthesized onto a commercial polyamide membrane (i.e., base-PA) via atmospheric pressure plasma-induced graft polymerization (APPIGP). The PAA nano-structured (SNS) base-PA membrane (SNS-PAA-PA) was scaled to a lesser degree, as quantified by a lower permeate flux decline and surface imaging, relative to the tested commercial membranes (Dow SW30, Toray SWRO, and BWRO). The cleaning of gypsum-scaled membranes with D.I. water flushing achieved 100% water permeability recovery for both the SNS-PAA-PA and Dow SW30 membranes, relative to 92–98% permeability restoration for the Toray membranes. The calcium carbonate scaling of SNS-PAA-PA membranes was also lower relative to the commercial membranes, but permeability recovery after D.I. water cleaning was somewhat lower (94%) but consistent with the level of surface scale coverage. In contrast, the calcite and gypsum-scaled membrane areas of the commercial membranes post-cleaning were significantly higher than for the SNS-PAA-PA membrane but with 100% permeability recovery, suggesting the potential for membrane damage when mineral scaling is severe. Full article

(This article belongs to the Special Issue Recent Advances in Desalination Based on Membrane Technologies)

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13 pages, 3562 KiB

Open AccessArticle

Experimental and Computational Approaches to Sulfonated Poly(arylene ether sulfone) Synthesis Using Different Halogen Atoms at the Reactive Site

by Seol Jang, Jung-Eun Cha, Seung Jae Moon, Justin Georg Albers, Min Ho Seo, Young-Woo Choi and Jong Hak Kim

Membranes 2022, 12(12), 1286; https://doi.org/10.3390/membranes12121286 - 19 Dec 2022

Viewed by 1366

Abstract

Engineering thermoplastics, such as poly(arylene ether sulfone), are more often synthesized using F-containing monomers rather than Cl-containing monomers because the F atom is considered more electronegative than Cl, leading to a better condensation polymerization reaction. In this study, the reaction’s spontaneity improved when [...] Read more.

Engineering thermoplastics, such as poly(arylene ether sulfone), are more often synthesized using F-containing monomers rather than Cl-containing monomers because the F atom is considered more electronegative than Cl, leading to a better condensation polymerization reaction. In this study, the reaction’s spontaneity improved when Cl atoms were used compared to the case using F atoms. Specifically, sulfonated poly(arylene ether sulfone) was synthesized by reacting 4,4′-dihydroxybiphenyl with two types of biphenyl sulfone monomers containing Cl and F atoms. No significant difference was observed in the structural, elemental, and chemical properties of the two copolymers based on nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, and electrochemical impedance spectroscopy. However, the solution viscosity and mechanical strength of the copolymer synthesized with the Cl-terminal monomers were slightly higher than those of the copolymer synthesized with the F-terminal monomers due to higher reaction spontaneity. The first-principle study was employed to elucidate the underlying mechanisms of these reactions. Full article

(This article belongs to the Special Issue Membrane Development and Applications in Electrochemistry)

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10 pages, 1766 KiB

Open AccessArticle

Treatment of Boiler Condensate by Ultrafiltration for Reuse

by Grégory Cano and Philippe Moulin

Membranes 2022, 12(12), 1285; https://doi.org/10.3390/membranes12121285 - 19 Dec 2022

Cited by 2 | Viewed by 1363

Abstract

The generation of water vapor is crucial for the petrochemical industry. In order to protect the boiler from damage, the re-injected water must not contain any suspended matter, especially hydrocarbons. Moreover, it is condensed steam with a temperature close to 100 °C and [...] Read more.

The generation of water vapor is crucial for the petrochemical industry. In order to protect the boiler from damage, the re-injected water must not contain any suspended matter, especially hydrocarbons. Moreover, it is condensed steam with a temperature close to 100 °C and the unintentional creation or chronic generation of pollution, respectively, that can more or less produce the concentrated pollution. In this context, membrane processes appear promising in order to achieve this reuse and more especially crossflow ceramic membranes. The novelty of this paper is to study the retention of hydrocarbons and suspended solids contained in the condensate hot water of a high-capacity boiler using ceramic ultrafiltration membranes. In total, two ultrafiltration molecular weight cut-offs were used: 50–150 kDa. Several operating parameters were studied such as effluent type (accidental or chronic pollution), temperature, transmembrane pressure, initial volume, and pilot plant size. In all cases, retention of suspended matter was above 90% and residual hydrocarbon concentrations were under 0.1 ppm even for high-volume concentrations. Control of the transmembrane pressure and the molecular weight cut-off of the membrane are key to optimizing the process. Despite the high-volume concentration obtained, the membranes were perfectly regenerated with conventional cleaning procedures. Full article

(This article belongs to the Special Issue Ceramic Membranes for Wastewater and Water Reuse)

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10 pages, 3239 KiB

Open AccessCommunication

Seeded Synthesis of AlPO₄-5 Membrane in Diluted Mother Liquor

by Jing Wang and Chao Ji

Membranes 2022, 12(12), 1284; https://doi.org/10.3390/membranes12121284 - 19 Dec 2022

Viewed by 1309

Abstract

AlPO₄-5 with an AFI topology membrane on an a-alumina substrate has been fabricated continuously, without defects, and with high intergrowth. By using traditional hydrothermal methods in diluted mother liquor, an AlPO₄-5 membrane has been produced by a simple second [...] Read more.

AlPO₄-5 with an AFI topology membrane on an a-alumina substrate has been fabricated continuously, without defects, and with high intergrowth. By using traditional hydrothermal methods in diluted mother liquor, an AlPO₄-5 membrane has been produced by a simple second growth synthesis. Scanning electron microscopy (SEM) revealed no defects in the prepared supporting film, and X-ray (XRD) diffraction confirmed the layer of molecular sieve AlPO₄-5 on the porous support of α-alumina. In this study, various synthesis parameters were systematically examined. Based on H₂, He, N₂, CO₂, and SF₆ permeance results, the supported membranes display Knudsen diffusion behavior, and the membrane’s pervaporation properties of organic compounds (n-hexane, o-xylene, and TIPB) show minimized defects, verifying their high quality. Full article

(This article belongs to the Section Inorganic Membranes)

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18 pages, 2844 KiB

Open AccessArticle

Modeling the Conductivity and Diffusion Permeability of a Track-Etched Membrane Taking into Account a Loose Layer

by Vladlen S. Nichka, Semyon A. Mareev, Pavel Yu. Apel, Konstantin G. Sabbatovskiy, Vladimir D. Sobolev and Victor V. Nikonenko

Membranes 2022, 12(12), 1283; https://doi.org/10.3390/membranes12121283 - 19 Dec 2022

Cited by 6 | Viewed by 1664

Abstract

The microheterogeneous model makes it possible to describe the main transport properties of ion-exchange membranes using a single set of input parameters. This paper describes an adaptation of the microheterogeneous model for describing the electrical conductivity and diffusion permeability of a track-etched membrane [...] Read more.

The microheterogeneous model makes it possible to describe the main transport properties of ion-exchange membranes using a single set of input parameters. This paper describes an adaptation of the microheterogeneous model for describing the electrical conductivity and diffusion permeability of a track-etched membrane (TEM). Usually, the transport parameters of TEMs are evaluated assuming that ion transfer occurs through the solution filling the membrane pores, which are cylindrical and oriented normally to the membrane surface. The version of the microheterogeneous model developed in this paper takes into account the presence of a loose layer, which forms as an intermediate layer between the pore solution and the membrane bulk material during track etching. It is assumed that this layer can be considered as a “gel phase” in the framework of the microheterogeneous model due to the fixed hydroxyl and carboxyl groups, which imparts ion exchange properties to the loose layer. The qualitative and quantitative agreement between the calculated and experimental concentration dependencies of the conductivity and diffusion permeability is discussed. The role of the model input parameters is described in relation to the structural features of the membrane. In particular, the inclination of the pores relative to the surface and their narrowing in the middle part of the membrane can be important for their properties. Full article

(This article belongs to the Special Issue Ion Transport in Membranes and Membrane Systems: Modelling and Experiment)

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14 pages, 3100 KiB

Open AccessArticle

A Thermodynamic Study on the Interaction between RH-23 Peptide and DMPC-Based Biomembrane Models

by Cristiano Giordani, Stefano Russo, Cristina Torrisi, Silvia Morante, Francesco Castelli and Maria Grazia Sarpietro

Membranes 2022, 12(12), 1282; https://doi.org/10.3390/membranes12121282 - 19 Dec 2022

Viewed by 1255

Abstract

Investigation of the interaction between drugs and biomembrane models, as a strategy to study and eventually improve drug/substrate interactions, is a crucial factor in preliminary screening. Synthesized peptides represent a source of potential anticancer and theragnostic drugs. In this study, we investigated the [...] Read more.

Investigation of the interaction between drugs and biomembrane models, as a strategy to study and eventually improve drug/substrate interactions, is a crucial factor in preliminary screening. Synthesized peptides represent a source of potential anticancer and theragnostic drugs. In this study, we investigated the interaction of a novel synthesized peptide, called RH-23, with a simplified dimyristoylphosphatidylcholine (DMPC) model of the cellular membrane. The interaction of RH-23 with DMPC, organized either in multilamellar vesicles (MLVs) and in Langmuir-Blodgett (LB) monolayers, was assessed using thermodynamic techniques, namely differential scanning calorimetry (DSC) and LB. The calorimetric evaluations showed that RH-23 inserted into MLVs, causing a stabilization of the phospholipid gel phase that increased with the molar fraction of RH-23. Interplay with LB monolayers revealed that RH-23 interacted with DMPC molecules. This work represents the first experimental thermodynamic study on the interaction between RH-23 and a simplified model of the lipid membrane, thus providing a basis for further evaluations of the effect of RH-23 on biological membranes and its therapeutic/diagnostic potential. Full article

(This article belongs to the Special Issue Membrane-Based Technologies in Pharmaceutical Sciences)

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50 pages, 2217 KiB

Open AccessReview

Polyhexanide-Releasing Membranes for Antimicrobial Wound Dressings: A Critical Review

by António Jorge Guiomar and Ana M. Urbano

Membranes 2022, 12(12), 1281; https://doi.org/10.3390/membranes12121281 - 18 Dec 2022

Cited by 8 | Viewed by 3559

Abstract

The prevalence of chronic, non-healing skin wounds in the general population, most notably diabetic foot ulcers, venous leg ulcers and pressure ulcers, is approximately 2% and is expected to increase, driven mostly by the aging population and the steady rise in obesity and [...] Read more.

The prevalence of chronic, non-healing skin wounds in the general population, most notably diabetic foot ulcers, venous leg ulcers and pressure ulcers, is approximately 2% and is expected to increase, driven mostly by the aging population and the steady rise in obesity and diabetes. Non-healing wounds often become infected, increasing the risk of life-threatening complications, which poses a significant socioeconomic burden. Aiming at the improved management of infected wounds, a variety of wound dressings that incorporate antimicrobials (AMDs), namely polyhexanide (poly(hexamethylene biguanide); PHMB), have been introduced in the wound-care market. However, many wound-care professionals agree that none of these wound dressings show comprehensive or optimal antimicrobial activity. This manuscript summarizes and discusses studies on PHMB-releasing membranes (PRMs) for wound dressings, detailing their preparation, physical properties that are relevant to the context of AMDs, drug loading and release, antibacterial activity, biocompatibility, wound-healing capacity, and clinical trials conducted. Some of these PRMs were able to improve wound healing in in vivo models, with no associated cytotoxicity, but significant differences in study design make it difficult to compare overall efficacies. It is hoped that this review, which includes, whenever available, international standards for testing AMDs, will provide a framework for future studies. Full article

(This article belongs to the Special Issue Functional Porous Membranes for Energy, Environmental and Biomedical Applications)

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14 pages, 5288 KiB

Open AccessArticle

MOF-Based Sorbents Used for the Removal of Hg²⁺ from Aqueous Solutions via a Sorption-Assisted Microfiltration

by Agnieszka Miśkiewicz, Wojciech Starosta, Rafał Walczak and Grażyna Zakrzewska-Kołtuniewicz

Membranes 2022, 12(12), 1280; https://doi.org/10.3390/membranes12121280 - 17 Dec 2022

Cited by 1 | Viewed by 1316

Abstract

Mercury is considered to be one of the most important chemicals of public health concern. Therefore, it is necessary to develop an effective method of removing mercury ions from aqueous solutions to protect people from exposure to this element. This paper presents research [...] Read more.

Mercury is considered to be one of the most important chemicals of public health concern. Therefore, it is necessary to develop an effective method of removing mercury ions from aqueous solutions to protect people from exposure to this element. This paper presents research on the application of a sorption-assisted microfiltration (SAMF) hybrid process for the removal of Hg²⁺ from aqueous solutions. As adsorbents used in the process, the metal-organic-framework-UiO-66-type materials have been considered. The methods of synthesis of two types of metal-organic-framework (MOF) sorbents were developed: UiO-66_MAA modified with mercaptoacetic acid (MAA) and a composite of UiO-66 with cellulose. The results of the experiments performed proved that the separation of Hg²⁺ from water solutions conducted in such a system was effective; however, a relatively long initial contact time of reagents before filtration was required. The experimental results can be used to optimize the parameters of the SAMF process in order to obtain an effective method of Hg²⁺ removal from aqueous solutions. Full article

(This article belongs to the Special Issue Polymer Inclusion Membrane in Industrial Application)

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31 pages, 3666 KiB

Open AccessArticle

Design Parameters of a Direct Contact Membrane Distillation and a Case Study of Its Applicability to Low-Grade Waste Energy

by Bitaw Nigatu Tewodros, Dae Ryook Yang and Kiho Park

Membranes 2022, 12(12), 1279; https://doi.org/10.3390/membranes12121279 - 17 Dec 2022

Cited by 3 | Viewed by 2238

Abstract

In the design of membrane distillation systems, the effect of different heat transfer coefficient models on the transmembrane flux seems to have been overlooked thus far. Interestingly, the range of discrepancy in the results of the transmembrane flux is wide, especially in the [...] Read more.

In the design of membrane distillation systems, the effect of different heat transfer coefficient models on the transmembrane flux seems to have been overlooked thus far. Interestingly, the range of discrepancy in the results of the transmembrane flux is wide, especially in the laminar flow region, where MD is often operated. This can be inferred by studying the design and parameters of the direct contact membrane distillation system. In this study, the physical and physiochemical properties that affect the design of MD are comprehensively reviewed, and based on the reviewed parameters, an MD design algorithm is developed. In addition, a cost analysis of the designed MD process for low-grade-energy fluids is conducted. As a result, a total unit product cost of USD 1.59/m³, 2.69/m³, and 15.36/m³ are obtained for the feed velocities of 0.25, 1 and 2.5 m/s, respectively. Among the design parameters, the membrane thickness and velocity are found to be the most influential. Full article

(This article belongs to the Special Issue Advances in Membrane Science for Sustainable Future)

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13 pages, 2147 KiB

Open AccessArticle

Structural Role of Plasma Membrane Sterols in Osmotic Stress Tolerance of Yeast Saccharomyces cerevisiae

by Svyatoslav S. Sokolov, Marina M. Popova, Peter Pohl, Andreas Horner, Sergey A. Akimov, Natalia A. Kireeva, Dmitry A. Knorre, Oleg V. Batishchev and Fedor F. Severin

Membranes 2022, 12(12), 1278; https://doi.org/10.3390/membranes12121278 - 17 Dec 2022

Cited by 3 | Viewed by 2109

Abstract

Yeast S. cerevisiae has been shown to suppress a sterol biosynthesis as a response to hyperosmotic stress. In the case of sodium stress, the failure to suppress biosynthesis leads to an increase in cytosolic sodium. The major yeast sterol, ergosterol, is known to [...] Read more.

Yeast S. cerevisiae has been shown to suppress a sterol biosynthesis as a response to hyperosmotic stress. In the case of sodium stress, the failure to suppress biosynthesis leads to an increase in cytosolic sodium. The major yeast sterol, ergosterol, is known to regulate functioning of plasma membrane proteins. Therefore, it has been suggested that the suppression of its biosynthesis is needed to adjust the activity of the plasma membrane sodium pumps and channels. However, as the sterol concentration is in the range of thirty to forty percent of total plasma membrane lipids, it is believed that its primary biological role is not regulatory but structural. Here we studied how lowering the sterol content affects the response of a lipid bilayer to an osmotic stress. In accordance with previous observations, we found that a decrease of the sterol fraction increases a water permeability of the liposomal membranes. Yet, we also found that sterol-free giant unilamellar vesicles reduced their volume during transient application of the hyperosmotic stress to a greater extent than the sterol-rich ones. Furthermore, our data suggest that lowering the sterol content in yeast cells allows the shrinkage to prevent the osmotic pressure-induced plasma membrane rupture. We also found that mutant yeast cells with the elevated level of sterol accumulated propidium iodide when exposed to mild hyperosmotic conditions followed by hypoosmotic stress. It is likely that the decrease in a plasma membrane sterol content stimulates a drop in cell volume under hyperosmotic stress, which is beneficial in the case of a subsequent hypo-osmotic one. Full article

(This article belongs to the Special Issue Membrane Regulation of Protein Function)

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19 pages, 5353 KiB

Open AccessArticle

A Green Stable Antifouling PEGylated PVDF Membrane Prepared by Vapor-Induced Phase Separation

by Hana Nur Aini, Irish Maggay, Yung Chang and Antoine Venault

Membranes 2022, 12(12), 1277; https://doi.org/10.3390/membranes12121277 - 16 Dec 2022

Viewed by 1663

Abstract

While green solvents are being implemented in the fabrication of polyvinylidene fluoride (PVDF) membranes, most are not compatible with the vapor-induced phase separation (VIPS) process for which relatively low dissolution temperatures are required. Additionally, preparing antifouling green membranes in one step by blending [...] Read more.

While green solvents are being implemented in the fabrication of polyvinylidene fluoride (PVDF) membranes, most are not compatible with the vapor-induced phase separation (VIPS) process for which relatively low dissolution temperatures are required. Additionally, preparing antifouling green membranes in one step by blending the polymer with an antifouling material before inducing phase separation remains extremely challenging due to the solubility issues. Here, the green solvent triethyl phosphate (TEP) was used to solubilize both PVDF and a copolymer (synthesized from styrene monomer and poly(ethylene glycol) methyl ether methacrylate). VIPS was then used, yielding symmetric bi-continuous microfiltration membranes. For a 2 wt% copolymer content in the casting solution, the corresponding membrane P2 showed a homogeneous and dense surface distribution of the copolymer, resulting in a high hydration capacity (>900 mg/cm³) and effective resistance to biofouling during the adsorption tests using bovine serum albumin, Escherichia coli or whole blood, with a measured fouling reduction of 80%, 89% and 90%, respectively. Cyclic filtration tests using bacteria highlighted the competitive antifouling properties of the membranes with a flux recovery ratio after two water/bacterial solution cycles higher than 70%, a reversible flux decline ratio of about 62% and an irreversible flux decline ratio of 28%. Finally, these green antifouling membranes were shown to be stable despite several weeks of immersion in water. Full article

(This article belongs to the Special Issue Separation Principles and Applications of Membrane Technology)

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30 pages, 3650 KiB

Open AccessReview

An Overview of the Modification Strategies in Developing Antifouling Nanofiltration Membranes

by Nor Naimah Rosyadah Ahmad, Abdul Wahab Mohammad, Ebrahim Mahmoudi, Wei Lun Ang, Choe Peng Leo and Yeit Haan Teow

Membranes 2022, 12(12), 1276; https://doi.org/10.3390/membranes12121276 - 16 Dec 2022

Cited by 20 | Viewed by 2404

Abstract

Freshwater deficiency has become a significant issue affecting many nations’ social and economic development because of the fast-growing demand for water resources. Nanofiltration (NF) is one of the promising technologies for water reclamation application, particularly in desalination, water, and wastewater treatment fields. Nevertheless, [...] Read more.

Freshwater deficiency has become a significant issue affecting many nations’ social and economic development because of the fast-growing demand for water resources. Nanofiltration (NF) is one of the promising technologies for water reclamation application, particularly in desalination, water, and wastewater treatment fields. Nevertheless, membrane fouling remains a significant concern since it can reduce the NF membrane performance and increase operating expenses. Consequently, numerous studies have focused on improving the NF membrane’s resistance to fouling. This review highlights the recent progress in NF modification strategies using three types of antifouling modifiers, i.e., nanoparticles, polymers, and composite polymer/nanoparticles. The correlation between antifouling performance and membrane properties such as hydrophilicity, surface chemistry, surface charge, and morphology are discussed. The challenges and perspectives regarding antifouling modifiers and modification strategies conclude this review. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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10 pages, 1780 KiB

Open AccessArticle

Modification of Carbon Nanomaterials by Association with Poly(3-octylthiophene-2,5-diyl) as a Method of Improving the Solid-Contact Layer in Ion-Selective Electrodes

by Barbara Niemiec, Robert Piech and Beata Paczosa-Bator

Membranes 2022, 12(12), 1275; https://doi.org/10.3390/membranes12121275 - 16 Dec 2022

Cited by 2 | Viewed by 1269

Abstract

A new group of carbon nanomaterials modified with poly(3-octylthiophene-2,5-diyl) for solid-contact layers in ion-selective electrodes was obtained. The materials were characterized by scanning electron microscopy and measurement of the contact angle. The modification greatly improved the hydrophobicity of the materials, and the highest [...] Read more.

A new group of carbon nanomaterials modified with poly(3-octylthiophene-2,5-diyl) for solid-contact layers in ion-selective electrodes was obtained. The materials were characterized by scanning electron microscopy and measurement of the contact angle. The modification greatly improved the hydrophobicity of the materials, and the highest contact angle (175°) was obtained for a polymer-modified carbon nanofibers/nanotube nanocomposite. The electrical parameters of the electrodes were determined using the methods of chronopotentiometry and electrochemical impedance spectroscopy. The highest electrical charge capacity was obtained for polymer-modified carbon nanofibers (7.87 mF/cm²). For this material, the lowest detection limit (10^−6.2 M) and the best potential reversibility (SD = 0.2 mV) were also obtained in potentiometric measurements. Full article

(This article belongs to the Special Issue Membrane-Based Electrochemical Sensors)

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24 pages, 14534 KiB

Open AccessReview

A Review on the Morphology and Material Properties of the Gas Separation Membrane: Molecular Simulation

by Yilin Liu, Na Li, Xin Cui, Weichao Yan, Jincai Su and Liwen Jin

Membranes 2022, 12(12), 1274; https://doi.org/10.3390/membranes12121274 - 15 Dec 2022

Cited by 4 | Viewed by 2237

Abstract

Gas membrane separation technology is widely applied in different industry processes because of its advantages relating to separation performance and economic efficiency. It is usually difficult and time consuming to determine the suitable membrane materials for specific industrial separation processes through traditional experimental [...] Read more.

Gas membrane separation technology is widely applied in different industry processes because of its advantages relating to separation performance and economic efficiency. It is usually difficult and time consuming to determine the suitable membrane materials for specific industrial separation processes through traditional experimental research methods. Molecular simulation is widely used to investigate the microscopic morphology and macroscopic properties of materials, and it guides the improvement of membrane materials. This paper comprehensively reviews the molecular-level exploration of the dominant mechanism and influencing factors of gas membrane-based separation. The thermodynamics and kinetics of polymer membrane synthesis, the molecular interactions among the penetrated gases, the relationships between the membrane properties and the transport characteristics of different gases in the composite membrane are summarized and discussed. The limitations and perspectives of the molecular simulation method in the study of the gas membrane separation process are also presented to rationalize its potential and innovative applications. This review provides a more comprehensive reference for promoting the materials’ design and engineering application of the gas separation membrane. Full article

(This article belongs to the Special Issue Modeling and Prediction of the Performance of Membrane Processes)

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19 pages, 3892 KiB

Open AccessArticle

Surface Interactions and Nanoconfinement of Methane and Methane plus CO₂ Revealed by High-Pressure Magic Angle Spinning NMR Spectroscopy and Molecular Dynamics

by Salim Ok, Siddharth Gautam, Kao-Hsiang Liu and David R. Cole

Membranes 2022, 12(12), 1273; https://doi.org/10.3390/membranes12121273 - 15 Dec 2022

Cited by 3 | Viewed by 1577

Abstract

This study explores the fundamental, molecular- to microscopic-level behavior of methane gas confined into nanoporous silica proxies with different pore diameters and surface-to-volume (S/V) ratios. Surfaces and pore walls of nanoporous silica matrices are decorated with hydroxyl (-OH) groups, resembling natural heterogeneity. High-pressure [...] Read more.

This study explores the fundamental, molecular- to microscopic-level behavior of methane gas confined into nanoporous silica proxies with different pore diameters and surface-to-volume (S/V) ratios. Surfaces and pore walls of nanoporous silica matrices are decorated with hydroxyl (-OH) groups, resembling natural heterogeneity. High-pressure MAS NMR was utilized to characterize the interactions between methane and the engineered nanoporous silica proxies under various temperature and pressure regimes. There was a change in the chemical shift position of confined methane slightly in the mixtures with nanoporous silica up to 393 K, as shown by high-pressure ¹³C-NMR. The ¹³C-NMR chemical shift of methane was changed by pressure, explained by the densification of methane inside the nanoporous silica materials. The influence of pore diameter and S/V of the nanoporous silica materials on the behaviors and dynamics of methane were studied. The presence of CO₂ in mixtures of silica and methane needs analysis with caution because CO₂ in a supercritical state and gaseous CO₂ change the original structure of nanoporous silica and change surface area and pore volume. According to simulation, the picosecond scale dynamics of methane confined in larger pores of amorphous silica is faster. In the 4 nm pore, the diffusivity obtained from MD simulations in the pore with a higher S/V ratio is slower due to the trapping of methane molecules in adsorbed layers close to the corrugated pore surface. In contrast, relaxation measured with NMR for smaller pores (higher S/V) exhibits larger T₁, indicating slower relaxation. Full article

(This article belongs to the Special Issue Advanced Research on Zeolite Based Membranes)

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9 pages, 3662 KiB

Open AccessArticle

An Experimental Study of a Zeolite Membrane Reactor for Reverse Water Gas Shift

by Motomu Sakai, Kyoka Tanaka and Masahiko Matsukata

Membranes 2022, 12(12), 1272; https://doi.org/10.3390/membranes12121272 - 15 Dec 2022

Cited by 3 | Viewed by 1516

Abstract

Reverse water gas shift (RWGS) is attracting attention as one of the promising technologies for CO₂ conversion. Selective removal of H₂O from the reaction system can improve the CO₂ conversion beyond the equilibrium conversion of RWGS in a conventional [...] Read more.

Reverse water gas shift (RWGS) is attracting attention as one of the promising technologies for CO₂ conversion. Selective removal of H₂O from the reaction system can improve the CO₂ conversion beyond the equilibrium conversion of RWGS in a conventional reactor. In this study, a conventional plug-flow reactor without membrane, and two types of RWGS membrane reactors using ZSM-5 membranes, were developed. The yield of CO without membrane (Case 1) was almost the same as the equilibrium conversion. A membrane reactor (Case 2) showed a CO yield 2–3% above that of a conventional reactor. From the results, the effectiveness of the dehydration membrane reactor for RWGS was verified. In addition, CO yield was further increased in the reactor made up of the combination of conventional reactor and membrane reactor (Case 3). For example, the CO yields in Cases 1, 2, and 3 at 560 K were 21.8, 24.9, and 29.0%, respectively. Although the CO yield increased in Case 2, a large amount of raw materials penetrated through the membrane to the permeation side, and was lost. In Case 3, H₂ and CO₂ permeation through the membrane were suppressed because of the existence of H₂O, resulting in the prevention of the leakage of raw material, and contributing to the high CO yield. Full article

(This article belongs to the Special Issue Catalysis in Membrane Reactors 2022)

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27 pages, 3090 KiB

Open AccessReview

A Review on Membrane Biofouling: Prediction, Characterization, and Mitigation

by Nour AlSawaftah, Waad Abuwatfa, Naif Darwish and Ghaleb A. Husseini

Membranes 2022, 12(12), 1271; https://doi.org/10.3390/membranes12121271 - 15 Dec 2022

Cited by 15 | Viewed by 3903

Abstract

Water scarcity is an increasing problem on every continent, which instigated the search for novel ways to provide clean water suitable for human use; one such way is desalination. Desalination refers to the process of purifying salts and contaminants to produce water suitable [...] Read more.

Water scarcity is an increasing problem on every continent, which instigated the search for novel ways to provide clean water suitable for human use; one such way is desalination. Desalination refers to the process of purifying salts and contaminants to produce water suitable for domestic and industrial applications. Due to the high costs and energy consumption associated with some desalination techniques, membrane-based technologies have emerged as a promising alternative water treatment, due to their high energy efficiency, operational simplicity, and lower cost. However, membrane fouling is a major challenge to membrane-based separation as it has detrimental effects on the membrane’s performance and integrity. Based on the type of accumulated foulants, fouling can be classified into particulate, organic, inorganic, and biofouling. Biofouling is considered the most problematic among the four fouling categories. Therefore, proper characterization and prediction of biofouling are essential for creating efficient control and mitigation strategies to minimize the damage associated with biofouling. Moreover, the use of artificial intelligence (AI) in predicting membrane fouling has garnered a great deal of attention due to its adaptive capability and prediction accuracy. This paper presents an overview of the membrane biofouling mechanisms, characterization techniques, and predictive methods with a focus on AI-based techniques, and mitigation strategies. Full article

(This article belongs to the Special Issue Membrane Technologies for Water and Wastewater Treatment: Advances, Challenges, and Future Avenues)

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15 pages, 2338 KiB

Open AccessFeature PaperArticle

Novel Polyelectrolyte-Based Draw Solute That Overcomes the Trade-Off between Forward Osmosis Performance and Ease of Regeneration

by Daryoush Emadzadeh, Amirsajad Atashgar and Boguslaw Kruczek

Membranes 2022, 12(12), 1270; https://doi.org/10.3390/membranes12121270 - 15 Dec 2022

Viewed by 1335

Abstract

Forward osmosis (FO) is an emerging technology for seawater and brackish desalination, wastewater treatment, and other applications, such as food processing, power generation, and protein and pharmaceutical enrichment. However, choosing a draw solute (DS) that provides an appropriate driving force and, at the [...] Read more.

Forward osmosis (FO) is an emerging technology for seawater and brackish desalination, wastewater treatment, and other applications, such as food processing, power generation, and protein and pharmaceutical enrichment. However, choosing a draw solute (DS) that provides an appropriate driving force and, at the same time, is easy to recover, is challenging. In this study, water-soluble poly(styrene sulfonate) (PSS) was modified by a high-electrical-conductivity 3,4-ethylenedioxythiophene (EDOT) monomer to fabricate a novel draw solute (mPSS). FO tests with the CTA membrane in the active layer facing the feed solution (AL-FS) orientation, using a 50 mS/cm aqueous solution of synthesized solute and distilled water as a feed solution exhibited a water flux of 4.2 L h⁻¹ m⁻² and a corresponding reverse solute flux of 0.19 g h⁻¹ m⁻². The FO tests with the same membrane, using a 50 mS/cm NaCl control draw solution, yielded a lower water flux of 3.6 L h⁻¹ m⁻² and a reverse solute flux of 4.13 g h⁻¹ m⁻², which was more than one order of magnitude greater. More importantly, the synthesized draw solute was easily regenerated using a commercial ultrafiltration membrane (PS35), which showed over 96% rejection. Full article

(This article belongs to the Special Issue Nanomaterial-Based Membranes for Water Treatment and Desalination)

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13 pages, 3355 KiB

Open AccessArticle

Improved Esterification of Citric Acid and n-Butanol Using a Dense and Acid-Resistant Beta Zeolite Membrane

by Zhengquan Yang, Mingyu Peng, Yu Li, Xiaowei Wu, Tian Gui, Yuqin Li, Fei Zhang, Xiangshu Chen and Hidetoshi Kita

Membranes 2022, 12(12), 1269; https://doi.org/10.3390/membranes12121269 - 15 Dec 2022

Cited by 2 | Viewed by 1394

Abstract

In this work, a dense and acid-resistant beta zeolite membrane was applied to improve the esterification of citric acid and n-butanol, for the first time. Through the continuous removal of the by-product water via pervaporation (PV), the conversion of citric acid was significantly [...] Read more.

In this work, a dense and acid-resistant beta zeolite membrane was applied to improve the esterification of citric acid and n-butanol, for the first time. Through the continuous removal of the by-product water via pervaporation (PV), the conversion of citric acid was significantly enhanced from 71.7% to 99.2% using p-Toluenesulfonic acid (PTSA) as catalyst. PTSA was a well-known strong acid, and the membrane kept almost no change after PV-esterification, indicating the superior acid resistance of beta zeolite membrane. Compared to the use of acid-resistant MOR zeolite membrane by PV-esterification, a consistently higher conversion of citric acid was obtained using a high-flux beta zeolite membrane. The results showed that high water permeation on the beta zeolite membrane, with good acid resistance, had a strong promoting effect on esterification, leading to an improved conversion. In addition, the citric acid conversion of 97.7% could still be achieved by PV-esterification at a low reaction temperature of 388 K. Full article

(This article belongs to the Special Issue Catalysis in Membrane Reactors 2022)

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12 pages, 2200 KiB

Open AccessArticle

Enhancing the Performance of PVDF/GO Ultrafiltration Membrane via Improving the Dispersion of GO with Homogeniser

by Xin Sun, Hana Shiraz, Riccardo Wong, Jingtong Zhang, Jinxin Liu, Jun Lu and Na Meng

Membranes 2022, 12(12), 1268; https://doi.org/10.3390/membranes12121268 - 15 Dec 2022

Cited by 6 | Viewed by 2925

Abstract

In this study, PVDF/GO-h composite membranes were synthesised using a homogeniser to improve the dispersion of GO nanosheets within the composite membrane’s structure, and then characterised and contrasted to PVDF/GO-s control samples, which were synthesised via traditional blending method-implementing a magnetic stirrer. By [...] Read more.

In this study, PVDF/GO-h composite membranes were synthesised using a homogeniser to improve the dispersion of GO nanosheets within the composite membrane’s structure, and then characterised and contrasted to PVDF/GO-s control samples, which were synthesised via traditional blending method-implementing a magnetic stirrer. By characterizing membrane via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), water contact angle (WCA) and membrane performance. SEM results showed that the number of the finger-like structure channels and pores in the sponge like structure of PVDF/GO-h composite membranes become more compared with PVDF/GO-s membranes. Water contact angle tests showed that the PVDF/GO-h composite membranes have lower contact angle than PVDF/GO-s control, which indicated the PVDF/GO-h composite membranes are more hydrophilic. Results also showed that composite membranes blended using homogeniser exhibited both improved water flux and rejection of target pollutants. In summary, it was shown that the performance of composite membranes could be improved significantly via homogenisation during synthesis, thus outlining the importance of further research into proper mixing. Full article

(This article belongs to the Special Issue Advanced Membrane Technologies for Wastewater Treatment and Recycling)

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11 pages, 1646 KiB

Open AccessArticle

An Activated Bismuth Layer Formed In Situ on a Solid Bismuth Microelectrode for Electrochemical Sensitive Determination of Ga(III)

by Malgorzata Grabarczyk and Edyta Wlazlowska

Membranes 2022, 12(12), 1267; https://doi.org/10.3390/membranes12121267 - 15 Dec 2022

Cited by 2 | Viewed by 1148

Abstract

In this paper, an activated bismuth layer formed in situ on a solid bismuth microelectrode, used as a working electrode for the electrochemical sensitive determination of Ga(III), based on anodic stripping voltammetry (ASV) is discussed. The new electrode significantly enhances the sensitivity in [...] Read more.

In this paper, an activated bismuth layer formed in situ on a solid bismuth microelectrode, used as a working electrode for the electrochemical sensitive determination of Ga(III), based on anodic stripping voltammetry (ASV) is discussed. The new electrode significantly enhances the sensitivity in the ASV determination of Ga(III) and exhibits superior performance in comparison to a bismuth film electrode prepared on a glassy carbon disc. The experimental variables, such as the potential and time of solid-bismuth-microelectrode activation, the composition of the supporting electrolyte, and the influence of possible interferences on the Ga(III) signal response, were tested. The most favorable values were selected (pH = 4.6; acetate buffer; activation potential/time: −1.8 V/6 s and −1.4 V/60 s). In the optimized conditions, the peak current was found to be proportional to the concentration of Ga(III) over the range from 2 × 10⁻⁸ to 2 × 10⁻⁶ mol L⁻¹ with R = 0.993. The limit of detection (LOD) was 7 × 10⁻⁹ mol L⁻¹. Finally, the proposed method was successfully applied for gallium determination in certified reference waters, such as surface water and waste water, as well as tap and river water samples. The water samples were analyzed without any pretreatment and recovery values from 92.4 to 105.5% were obtained. Full article

(This article belongs to the Special Issue Membrane-Based Electrochemical Sensors)

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22 pages, 5876 KiB

Open AccessArticle

Design and Utilization of a Direct Methanol Fuel Cell

by Aser Alaa Ahmed, Malik Al Labadidi, Ahmed T. Hamada and Mehmet Fatih Orhan

Membranes 2022, 12(12), 1266; https://doi.org/10.3390/membranes12121266 - 14 Dec 2022

Cited by 6 | Viewed by 4132

Abstract

This study introduces a step-by-step, summarized overview of direct methanol fuel cell (DMFC) fundamentals, thermodynamic–electrochemical principles, and system evaluation factors. In addition, a parametric investigation of a JENNY 600S DMFC is conducted to simulate cell performance behavior under varying operating conditions. The system [...] Read more.

This study introduces a step-by-step, summarized overview of direct methanol fuel cell (DMFC) fundamentals, thermodynamic–electrochemical principles, and system evaluation factors. In addition, a parametric investigation of a JENNY 600S DMFC is conducted to simulate cell performance behavior under varying operating conditions. The system is mathematically modeled and solved in MATLAB and accounts for multi-irreversibilities such as the activation and ohmic and concentration overpotentials. The performance of the modeled system was validated against theoretical and experimental results from the literature. The results indicated that increasing the fuel cell’s operating temperature yields enhanced output cell voltages due to enhanced methanol oxidation reactions. Nevertheless, the maximum efficiency limits of the fuel cell tend to decrease with an increase in temperature. In addition, the model has also depicted that enhanced output cell voltages are associated with increased oxygen consumption, resulting in the lower exit flowrates of the reactants. Full article

(This article belongs to the Section Membrane Physics and Theory)

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12 pages, 1841 KiB

Open AccessReview

A Review of Recent Chitosan Anion Exchange Membranes for Polymer Electrolyte Membrane Fuel Cells

by Vijayalekshmi Vijayakumar and Sang Yong Nam

Membranes 2022, 12(12), 1265; https://doi.org/10.3390/membranes12121265 - 14 Dec 2022

Cited by 9 | Viewed by 2466

Abstract

Considering the critical energy challenges and the generation of zero-emission anion exchange membrane (AEM) sources, chitosan-based anion exchange membranes have garnered considerable interest in fuel cell applications owing to their various advantages, including their eco-friendly nature, flexibility for structural modification, and improved mechanical, [...] Read more.

Considering the critical energy challenges and the generation of zero-emission anion exchange membrane (AEM) sources, chitosan-based anion exchange membranes have garnered considerable interest in fuel cell applications owing to their various advantages, including their eco-friendly nature, flexibility for structural modification, and improved mechanical, thermal, and chemical stability. The present mini-review highlights the advancements of chitosan-based biodegradable anion exchange membranes for fuel cell applications published between 2015 and 2022. Key points from the rigorous literature evaluation are: grafting with various counterions in addition to crosslinking contributed good conductivity and chemical as well as mechanical stability to the membranes; use of the interpenetrating network as well as layered structures, blending, and modified nanomaterials facilitated a significant reduction in membrane swelling and long-term alkaline stability. The study gives insightful guidance to the industry about replacing Nafion with a low-cost, environmentally friendly membrane source. It is suggested that more attention be given to exploring chitosan-based anion exchange membranes in consideration of effective strategies that focus on durability, as well as optimization of the operational conditions of fuel cells for large-scale applications. Full article

(This article belongs to the Special Issue Advanced Membranes for Fuel Cells and Redox Flow Batteries)

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28 pages, 4823 KiB

Open AccessArticle

Understanding Functional Redundancy and Promiscuity of Multidrug Transporters in E. coli under Lipophilic Cation Stress

by Mohammad S. Radi, Lachlan J. Munro, Jesus E. Salcedo-Sora, Se Hyeuk Kim, Adam M. Feist and Douglas B. Kell

Membranes 2022, 12(12), 1264; https://doi.org/10.3390/membranes12121264 - 14 Dec 2022

Cited by 2 | Viewed by 1607

Abstract

Multidrug transporters (MDTs) are major contributors to microbial drug resistance and are further utilized for improving host phenotypes in biotechnological applications. Therefore, the identification of these MDTs and the understanding of their mechanisms of action in vivo are of great importance. However, their [...] Read more.

Multidrug transporters (MDTs) are major contributors to microbial drug resistance and are further utilized for improving host phenotypes in biotechnological applications. Therefore, the identification of these MDTs and the understanding of their mechanisms of action in vivo are of great importance. However, their promiscuity and functional redundancy represent a major challenge towards their identification. Here, a multistep tolerance adaptive laboratory evolution (TALE) approach was leveraged to achieve this goal. Specifically, a wild-type E. coli K-12-MG1655 and its cognate knockout individual mutants ΔemrE, ΔtolC, and ΔacrB were evolved separately under increasing concentrations of two lipophilic cations, tetraphenylphosphonium (TPP⁺), and methyltriphenylphosphonium (MTPP⁺). The evolved strains showed a significant increase in MIC values of both cations and an apparent cross-cation resistance. Sequencing of all evolved mutants highlighted diverse mutational mechanisms that affect the activity of nine MDTs including acrB, mdtK, mdfA, acrE, emrD, tolC, acrA, mdtL, and mdtP. Besides regulatory mutations, several structural mutations were recognized in the proximal binding domain of acrB and the permeation pathways of both mdtK and mdfA. These details can aid in the rational design of MDT inhibitors to efficiently combat efflux-based drug resistance. Additionally, the TALE approach can be scaled to different microbes and molecules of medical and biotechnological relevance. Full article

(This article belongs to the Special Issue Research on Bacterial Cell Membranes)

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24 pages, 8791 KiB

Open AccessArticle

The Application of the Nanofiltration Membrane NF270 for Separation of Fermentation Broths

by Wirginia Tomczak

Membranes 2022, 12(12), 1263; https://doi.org/10.3390/membranes12121263 - 14 Dec 2022

Cited by 5 | Viewed by 2273

Abstract

The potential for nanofiltration (NF) in removing both relatively low molecular weight (MW) organic species and charged solutes from complex media is noteworthy. The main aim of the current work was to improve understanding of the separation mechanisms of fermentation broths components in [...] Read more.

The potential for nanofiltration (NF) in removing both relatively low molecular weight (MW) organic species and charged solutes from complex media is noteworthy. The main aim of the current work was to improve understanding of the separation mechanisms of fermentation broths components in the NF process. For this purpose, the experimental investigations were performed using the commercial polyamide NF270 membrane. The feed solution was ultrafiltered 1,3-propanediol (1,3-PD) broths. The separation results were analyzed and discussed in light of the detailed characteristics of both the membrane and the broth components. It has been noted that the membrane ensured the complete 1,3-PD permeability and significant rejection of some feed components. A thorough analysis showed that the retention of carboxylic acids was based on both the Donnan effect and sieve mechanism, according to the following order: succinic acid > lactic acid > acetic acid > formic acid. Indeed, acids retention increased with increasing charged acids ions valency, Stokes radius (r_S) as well as MW, and decreasing diffusion coefficient (D). In turn, for ions, the following orders retention was determined: SO₄²⁻ = PO₄³⁻ > Cl⁻ and Ca²⁺ > Na⁺ > NH₄⁺ ~ K⁺. It indicated that the ions retention increased with increasing ions charge density, hydrated radius (r_H), and hydration energy (E_h). It showed that the separation of the ions was based on the Donnan exclusion, sieving effect, and dielectric exclusion. Full article

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

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10 pages, 3067 KiB

Open AccessArticle

Ionic Liquids-Polymer of Intrinsic Microporosity (PIMs) Blend Membranes for CO₂ Separation

by Giuseppe Ferraro, Carmela Astorino, Mattia Bartoli, Alberto Martis, Stefania Lettieri, Candido Fabrizio Pirri and Sergio Bocchini

Membranes 2022, 12(12), 1262; https://doi.org/10.3390/membranes12121262 - 13 Dec 2022

Cited by 4 | Viewed by 1575

Abstract

Membranes with high CO₂ solubility are essential for developing a separation technology with low carbon footprint. To this end, physical blend membranes of [BMIM][Ac] and [BMIM][Succ] as Ionic Liquids (ILs) and PIM-1 as the polymer were prepared trying to combine the high [...] Read more.

Membranes with high CO₂ solubility are essential for developing a separation technology with low carbon footprint. To this end, physical blend membranes of [BMIM][Ac] and [BMIM][Succ] as Ionic Liquids (ILs) and PIM-1 as the polymer were prepared trying to combine the high permeability properties of PIM-1 with the high CO₂ solubility of the chosen ILs. Membranes with a PIM-1/[BMIM][Ac] 4/1 ratio nearly double their CO₂ solubility at 0.8 bar (0.86 cm³ (STP)/cm³ cmHg), while other ratios still maintain similar solubilities to PIM-1 (0.47 cm³ (STP)/cm³ cmHg). Moreover, CO₂ permeability of PIM-1/[BMIM][Ac] blended membranes were between 1050 and 2090 Barrer for 2/1 and 10/1 ratio, lower than PIM-1 membrane, but still highly permeable. The here presented self-standing and mechanically resistant blend membranes have yet a lower permeability compared to PIM-1 yet an improved CO₂ solubility, which eventually will translate in higher CO₂/N₂ selectivity. These promising preliminary results will allow us to select and optimize the best performing PIM-1/ILs blends to develop outstanding membranes for an improved gas separation technology. Full article

(This article belongs to the Special Issue Membrane Materials and Processes for Liquid and Gas Separation)

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20 pages, 812 KiB

Open AccessReview

The Re-Localization of Proteins to or Away from Membranes as an Effective Strategy for Regulating Stress Tolerance in Plants

by Yee-Shan Ku, Sau-Shan Cheng, Ming-Yan Cheung, Cheuk-Hin Law and Hon-Ming Lam

Membranes 2022, 12(12), 1261; https://doi.org/10.3390/membranes12121261 - 13 Dec 2022

Cited by 1 | Viewed by 1745

Abstract

The membranes of plant cells are dynamic structures composed of phospholipids and proteins. Proteins harboring phospholipid-binding domains or lipid ligands can localize to membranes. Stress perception can alter the subcellular localization of these proteins dynamically, causing them to either associate with or detach [...] Read more.

The membranes of plant cells are dynamic structures composed of phospholipids and proteins. Proteins harboring phospholipid-binding domains or lipid ligands can localize to membranes. Stress perception can alter the subcellular localization of these proteins dynamically, causing them to either associate with or detach from membranes. The mechanisms behind the re-localization involve changes in the lipidation state of the proteins and interactions with membrane-associated biomolecules. The functional significance of such re-localization includes the regulation of molecular transport, cell integrity, protein folding, signaling, and gene expression. In this review, proteins that re-localize to or away from membranes upon abiotic and biotic stresses will be discussed in terms of the mechanisms involved and the functional significance of their re-localization. Knowledge of the re-localization mechanisms will facilitate research on increasing plant stress adaptability, while the study on re-localization of proteins upon stresses will further our understanding of stress adaptation strategies in plants. Full article

(This article belongs to the Special Issue Advanced Research on Structure-Function Relationships of Membrane Proteins, 2nd Edition)

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18 pages, 6671 KiB

Open AccessFeature PaperArticle

Performance Comparison of Proton Exchange Membrane Water Electrolysis Cell Using Channel and PTL Flow Fields through Three-Dimensional Two-Phase Flow Simulation

by Seongsoon Park, Woojung Lee and Youngseung Na

Membranes 2022, 12(12), 1260; https://doi.org/10.3390/membranes12121260 - 13 Dec 2022

Cited by 4 | Viewed by 2867

Abstract

Water electrolysis technology is required to overcome the intermittency of renewable energy sources. Among various water electrolysis methods, the proton exchange membrane water electrolysis (PEMWE) cell has the advantages of a fast response and high current density. However, high capital costs have hindered [...] Read more.

Water electrolysis technology is required to overcome the intermittency of renewable energy sources. Among various water electrolysis methods, the proton exchange membrane water electrolysis (PEMWE) cell has the advantages of a fast response and high current density. However, high capital costs have hindered the commercialization of PEMWE; therefore, it is important to lower the price of bipolar plates, which make PEMWE expensive. In addition, since the flow field inscribed in the bipolar plate significantly influences the performance, it is necessary to design the enhanced pattern. A three-dimensional two-phase flow model was used to analyze the two-phase flow and electrochemical reactions of the PEMWE anode. In order to compare the experimental results with the simulation, experiments were conducted according to the flow rate, and the results were in good agreement. First, as a result of comparing the performance of the channel and PTL (porous transport layer) flow fields, the channel flow field showed better performance than the PTL flow field. For the channel flow field, the higher the ratio of the channel width-to-rib width and the permeability of PTL, the performance got better. In the case of the PTL flow field, with the increased capillary pressure, the performance improved even if the PTL permeability decreased. Next, the direction of gravity affected the performance only when the channel flow field was used, and the X+ and Z+ directions were optimal for the performance. Finally, increasing the inlet flow rate could reduce the difference in performance between the channel and PTL flow fields, but the pressure drop gradually increased. Full article

(This article belongs to the Special Issue Nanomaterial-Based Membranes for Water Treatment and Desalination)

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21 pages, 5553 KiB

Open AccessArticle

Novel Magnetic Mixed Cellulose Acetate Matrix Membranes with Oxygen-Enrichment Potential

by Norhan Nady, Noha Salem, Mohamed R. Elmarghany, Mohamed S. Salem and Sherif H. Kandil

Membranes 2022, 12(12), 1259; https://doi.org/10.3390/membranes12121259 - 13 Dec 2022

Cited by 1 | Viewed by 1507

Abstract

This work presents novel magnetic mixed cellulose-based matrix membranes that combine the advantages of a low-cost common polymer matrix, such as cellulose acetate (CA), and a low-cost magnetic filler. Moreover, the presented magnetic mixed CA matrix membranes were fabricated and used without applying [...] Read more.

This work presents novel magnetic mixed cellulose-based matrix membranes that combine the advantages of a low-cost common polymer matrix, such as cellulose acetate (CA), and a low-cost magnetic filler. Moreover, the presented magnetic mixed CA matrix membranes were fabricated and used without applying an external magnetic field during either the membrane casting or the separating process. Poly(methylmethacrylate) and lithium chloride were used in order to improve the mechanical properties and porosity of the fabricated membranes. The iron–nickel magnetic alloys used were prepared through a simple chemical reduction method with unique morphologies (Fe₁₀Ni₉₀—starfish-like and Fe₂₀Ni₈₀—necklace-like). The novel magnetic mixed CA matrix membranes fabricated were characterized using different analysis techniques, including SEM, EDX, XRD, TGA, and FTIR-ATR analyses. Furthermore, the static water contact angle, membrane thickness, surface roughness, tensile strength, and membrane porosity (using ethanol and water) were determined. In addition, vibrating sample magnetometer (VSM) analysis was conducted and the oxygen transition rate (OTR) was studied. The magnetic mixed CA matrix membrane containing starfish-like Fe₁₀Ni₉₀ alloy was characterized by high coercivity (109 Oe) and an efficient 1.271 × 10⁻⁵ cm³/(m²·s) OTR compared to the blank CA membrane with 19.8 Oe coercivity and no OTR. The effects of the polymeric matrix composition, viscosity, and compatibility with the alloys/fillers used on the structure and performance of the fabricated mixed CA matrix membranes compared to the previously used poly(ethersufone) polymeric matrix are discussed and highlighted. The novel magnetic mixed CA matrix membranes presented have good potential for use in the oxygen-enrichment process. Full article

(This article belongs to the Special Issue Mixed-Matrix Membranes: Preparation, Characterization, Modeling/Simulation and Applications)

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18 pages, 5173 KiB

Open AccessArticle

Optimization of Preparation Conditions of Poly(m-phenylene isophthalamide) PMIA Hollow Fiber Nanofiltration Membranes for Dye/Salt Wastewater Treatment

by Qinliang Jiang and Kaisong Zhang

Membranes 2022, 12(12), 1258; https://doi.org/10.3390/membranes12121258 - 13 Dec 2022

Cited by 2 | Viewed by 1602

Abstract

Externally selective thin film composite (TFC) hollow fiber (HF) nanofiltration membranes (NFMs) hold great industrial application prospects because of their high surface area module. However, the complicated preparation process of the membrane has hindered its mass manufacture and application. In this work, PMIA [...] Read more.

Externally selective thin film composite (TFC) hollow fiber (HF) nanofiltration membranes (NFMs) hold great industrial application prospects because of their high surface area module. However, the complicated preparation process of the membrane has hindered its mass manufacture and application. In this work, PMIA TFC HF NFMs were successfully prepared by the interfacial polymerization (IP) of piperazine (PIP) with 1,3,5-benzenetricarbonyl trichloride (TMC). The effect of the membrane preparation conditions on their separation performance was systematically investigated. The characterized results showed the successful formation of a polyamide (PA) separation layer on PMIA HF substrates by the IP process. The as-prepared HF NFMs’ performance under optimized conditions achieved the highest pure water permeability (18.20 L·m⁻²·h⁻¹, 0.35 MPa) and superior salt rejection in the order: R_Na₂SO₄ (98.30%) > R_MgSO₄ (94.60%) > R_MgCl₂ (61.48%) > R_NaCl (19.24%). In addition, the as-prepared PMIA HF TFC NFMs exhibited desirable pressure resistance at various operating bars and Na₂SO₄ feed concentrations. Excellent separation performance of chromotrope 2B dye was also achieved. The as-prepared PMIA HF NFMs thus show great promise for printing and dyeing wastewater treatment. Full article

(This article belongs to the Special Issue Mixed Matrix Membranes for Energy and Environmental Applications)

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