Membranes

24 pages, 1200 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Challenges and Solutions for Global Water Scarcity

by Hilla Shemer, Shlomo Wald and Raphael Semiat

Membranes 2023, 13(6), 612; https://doi.org/10.3390/membranes13060612 - 20 Jun 2023

Cited by 12 | Viewed by 5886

Climate change, global population growth, and rising standards of living have put immense strain on natural resources, resulting in the unsecured availability of water as an existential resource. Access to high-quality drinking water is crucial for daily life, food production, industry, and nature. [...] Read more.

Climate change, global population growth, and rising standards of living have put immense strain on natural resources, resulting in the unsecured availability of water as an existential resource. Access to high-quality drinking water is crucial for daily life, food production, industry, and nature. However, the demand for freshwater resources exceeds the available supply, making it essential to utilize all alternative water resources such as the desalination of brackish water, seawater, and wastewater. Reverse osmosis desalination is a highly efficient method to increase water supplies and make clean, affordable water accessible to millions of people. However, to ensure universal access to water, various measures need to be implemented, including centralized governance, educational campaigns, improvements in water catchment and harvesting technologies, infrastructure development, irrigation and agricultural practices, pollution control, investments in novel water technologies, and transboundary water cooperation. This paper provides a comprehensive overview of measures for utilizing alternative water sources, with particular emphasis on seawater desalination and wastewater reclamation techniques. In particular, membrane-based technologies are critically reviewed, with a focus on their energy consumption, costs, and environmental impacts. Full article

(This article belongs to the Section Membrane Applications)

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12 pages, 5496 KiB

Open AccessArticle

Preparation of PVDF-PVP Composite Membranes for Oily Wastewater Treatment

by Sutrasno Kartohardjono, Ghofira Muna Khansa Salsabila, Azzahra Ramadhani, Irfan Purnawan and Woei Jye Lau

Membranes 2023, 13(6), 611; https://doi.org/10.3390/membranes13060611 - 20 Jun 2023

Cited by 2 | Viewed by 1519

Abstract

The oil and gas industry and related applications generate large quantities of oily wastewater, which can adversely affect the environment and human health if not properly handled. This study aims to prepare polyvinylidene fluoride (PVDF) membranes incorporated with polyvinylpyrrolidone (PVP) additives and utilize [...] Read more.

The oil and gas industry and related applications generate large quantities of oily wastewater, which can adversely affect the environment and human health if not properly handled. This study aims to prepare polyvinylidene fluoride (PVDF) membranes incorporated with polyvinylpyrrolidone (PVP) additives and utilize them to treat oily wastewater through the ultrafiltration (UF) process. Flat sheet membranes were prepared using PVDF dissolved in N,N-dimethylacetamide, followed by the addition of PVP ranging from 0.5 to 35 g. Characterization by scanning electron microscopy (SEM), water contact angle, Fourier transform infrared spectroscopy (FTIR), and mechanical strength tests were performed on the flat PVDF/PVP membranes to understand and compare the changes in the physical and chemical properties of the membranes. Prior to the UF process, oily wastewater was treated by a coagulation–flocculation process through a jar tester using polyaluminum chloride (PAC) as a coagulant. Based on the characterization of the membrane, the addition of PVP improves the physical and chemical properties of the membrane. The membrane’s pore size becomes larger, which can increase its permeability and flux. In general, the addition of PVP to the PVDF membrane can increase the porosity and decrease the water contact angle, thereby increasing the membrane’s hydrophilicity. With respect to filtration performance, the wastewater flux of the resultant membrane increases with increasing PVP content, but the rejections for TSS, turbidity, TDS, and COD are reduced. Full article

(This article belongs to the Special Issue Mixed-Matrix Membranes and Polymeric Membranes 2.0)

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17 pages, 5044 KiB

Open AccessArticle

Optical Properties and Interference Effects of the Lens Mitochondrion

by Felix Margadant, Zakaria Almsherqi, Xiaochun Xu and Yuru Deng

Membranes 2023, 13(6), 610; https://doi.org/10.3390/membranes13060610 - 20 Jun 2023

Viewed by 1387

Abstract

The lens mitochondrion of the tree shrew, located along the optical pathway between the lens and photoreceptors, has been investigated. The results suggest that the lens mitochondrion acts as a quasi-bandgap or imperfect photonic crystal. Interference effects cause a shift in the focus [...] Read more.

The lens mitochondrion of the tree shrew, located along the optical pathway between the lens and photoreceptors, has been investigated. The results suggest that the lens mitochondrion acts as a quasi-bandgap or imperfect photonic crystal. Interference effects cause a shift in the focus and introduce wavelength-dependent behavior similar to dispersion. Optical channels within the mitochondrion form a mild waveguide, preferentially propagating light within certain compartments. The lens mitochondrion also functions as an imperfect UV-shielding interference filter. Overall, this study provides insights into the dual role of the lens mitochondrion and the complex behavior of light within biological systems. Full article

(This article belongs to the Special Issue Artificial Models of Biological Membranes)

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12 pages, 3265 KiB

Open AccessCommunication

Synthesis and Characterization of Electrical and Thermal Conductive Vinyltriethoxysilane Functionalized Graphene Oxide/Poly (Methyl Methacrylate) Nanocomposite Films

by Srosh Fazil, Khurram Liaqat, Wajid Rehman and Magda H. Abdellatif

Membranes 2023, 13(6), 609; https://doi.org/10.3390/membranes13060609 - 20 Jun 2023

Cited by 1 | Viewed by 1064

Abstract

The present study is an attempt to improve thermal, mechanical and electrical properties of poly (methyl methacrylate) (PMMA). For this purpose, vinyltriethoxysilane (VTES) was grafted covalently on the surface of graphene oxide (GO). This VTES functionalized graphene oxide (VGO) was dispersed in the [...] Read more.

The present study is an attempt to improve thermal, mechanical and electrical properties of poly (methyl methacrylate) (PMMA). For this purpose, vinyltriethoxysilane (VTES) was grafted covalently on the surface of graphene oxide (GO). This VTES functionalized graphene oxide (VGO) was dispersed in the PMMA matrix using the solution casting method. The morphology of the resultant PMMA/VGO nanocomposites was analyzed by SEM indicating well-dispersed VGO in the PMMA matrix. Thermal stability, tensile strength and thermal conductivity increased by 90%, 91% and 75%, respectively, whereas volume electrical resistivity and surface electrical resistivity reduced to 9.45 × 10⁵ Ω/cm and 5.45 × 10⁷ Ω/cm², respectively. Full article

(This article belongs to the Special Issue Advanced Research on Thin-Film Composite Membranes)

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16 pages, 5947 KiB

Open AccessArticle

Saline Retention and Permeability of Nanofiltration Membranes Versus Resistance and Capacitance as Obtained from Impedance Spectroscopy under a Concentration Gradient

by Miguel-Ángel Pérez, Silvia Gallego, Laura Palacio, Antonio Hernández, Pedro Prádanos and Francisco Javier Carmona

Membranes 2023, 13(6), 608; https://doi.org/10.3390/membranes13060608 - 18 Jun 2023

Viewed by 1044

Abstract

Impedance spectroscopy has been widely used for the study of the electrical properties of membranes for their characterization. The most common use of this technique is the measure of the conductivity of different electrolyte solutions to study the behavior and movement of electrically [...] Read more.

Impedance spectroscopy has been widely used for the study of the electrical properties of membranes for their characterization. The most common use of this technique is the measure of the conductivity of different electrolyte solutions to study the behavior and movement of electrically charged particles inside the pores of membranes. The objective of this investigation was to observe if there is a relation present between the retention that a nanofiltration membrane possesses to certain electrolytic solutions (NaCl, KCl, MgCl₂, CaCl₂, and Na₂SO₄) and the parameters that are obtained through IS measurements of the active layer of the membrane. To achieve our objective, different characterization techniques were performed to obtain the permeability, retention, and zeta potential values of a Desal-HL nanofiltration membrane. Impedance spectroscopy measurements were performed when a gradient concentration was present between both sides of the membrane to study the variation that the electrical parameters had with the time evolution. Full article

(This article belongs to the Special Issue Membranes for Selective Nano/Sub-nanometer Scale Mass Transport)

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15 pages, 4462 KiB

Open AccessArticle

Conformational State of Fenamates at the Membrane Interface: A MAS NOESY Study

by Ilya A. Khodov, Konstantin V. Belov, Daniel Huster and Holger A. Scheidt

Membranes 2023, 13(6), 607; https://doi.org/10.3390/membranes13060607 - 17 Jun 2023

Cited by 2 | Viewed by 9172

Abstract

The present work analyzes the ¹H NOESY MAS NMR spectra of three fenamates (mefenamic, tolfenamic, and flufenamic acids) localized in the lipid–water interface of phosphatidyloleoylphosphatidylcholine (POPC) membranes. The observed cross-peaks in the two-dimensional NMR spectra characterized intramolecular proximities between the hydrogen atoms [...] Read more.

The present work analyzes the ¹H NOESY MAS NMR spectra of three fenamates (mefenamic, tolfenamic, and flufenamic acids) localized in the lipid–water interface of phosphatidyloleoylphosphatidylcholine (POPC) membranes. The observed cross-peaks in the two-dimensional NMR spectra characterized intramolecular proximities between the hydrogen atoms of the fenamates as well as intermolecular interactions between the fenamates and POPC molecules. The peak amplitude normalization for an improved cross-relaxation (PANIC) approach, the isolated spin-pair approximation (ISPA) model, and the two-position exchange model were used to calculate the interproton distances indicative of specific conformations of the fenamates. The results showed that the proportions of the A+C and B+D conformer groups of mefenamic and tolfenamic acids in the presence of POPC were comparable within the experimental error and amounted to 47.8%/52.2% and 47.7%/52.3%, respectively. In contrast, these proportions for the flufenamic acid conformers differed and amounted to 56.6%/43.4%. This allowed us to conclude that when they bind to the POPC model lipid membrane, fenamate molecules change their conformational equilibria. Full article

(This article belongs to the Special Issue Prospects for Application of Natural Compounds and Their Derivatives in Biological and Artificial Membranes)

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21 pages, 3452 KiB

Open AccessReview

Bringing GPCR Structural Biology to Medical Applications: Insights from Both V2 Vasopressin and Mu-Opioid Receptors

by Aurélien Fouillen, Julien Bous, Sébastien Granier, Bernard Mouillac and Remy Sounier

Membranes 2023, 13(6), 606; https://doi.org/10.3390/membranes13060606 - 16 Jun 2023

Viewed by 2146

Abstract

G-protein coupled receptors (GPCRs) are versatile signaling proteins that regulate key physiological processes in response to a wide variety of extracellular stimuli. The last decade has seen a revolution in the structural biology of clinically important GPCRs. Indeed, the improvement in molecular and [...] Read more.

G-protein coupled receptors (GPCRs) are versatile signaling proteins that regulate key physiological processes in response to a wide variety of extracellular stimuli. The last decade has seen a revolution in the structural biology of clinically important GPCRs. Indeed, the improvement in molecular and biochemical methods to study GPCRs and their transducer complexes, together with advances in cryo-electron microscopy, NMR development, and progress in molecular dynamic simulations, have led to a better understanding of their regulation by ligands of different efficacy and bias. This has also renewed a great interest in GPCR drug discovery, such as finding biased ligands that can either promote or not promote specific regulations. In this review, we focus on two therapeutically relevant GPCR targets, the V2 vasopressin receptor (V2R) and the mu-opioid receptor (µOR), to shed light on the recent structural biology studies and show the impact of this integrative approach on the determination of new potential clinical effective compounds. Full article

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

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23 pages, 3089 KiB

Open AccessArticle

Membranes in Water Reclamation: Treatment, Reuse and Concentrate Management

by Sukanyah Devaisy, Jaya Kandasamy, Tien Vinh Nguyen, Harsha Ratnaweera and Saravanamuthu Vigneswaran

Membranes 2023, 13(6), 605; https://doi.org/10.3390/membranes13060605 - 15 Jun 2023

Cited by 3 | Viewed by 1925

Abstract

In this article, an extensive examination is provided on the possible uses of membranes and hybrid processes in wastewater treatment. While membrane technologies face certain constraints, such as membrane fouling and scaling, the incomplete elimination of emerging contaminants, elevated expenses, energy usage, and [...] Read more.

In this article, an extensive examination is provided on the possible uses of membranes and hybrid processes in wastewater treatment. While membrane technologies face certain constraints, such as membrane fouling and scaling, the incomplete elimination of emerging contaminants, elevated expenses, energy usage, and brine disposal, there are approaches that can address these challenges. Methods such as pretreating the feed water, utilizing hybrid membrane systems and hybrid dual-membrane systems, and employing other innovative membrane-based treatment techniques can enhance the efficacy of membrane processes and advance sustainability. Full article

(This article belongs to the Special Issue Applications of Membrane Processes in Desalination, Wastewater Treatment and Resource Recovery)

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28 pages, 43955 KiB

Open AccessArticle

Nano-Chitosan/Eucalyptus Oil/Cellulose Acetate Nanofibers: Manufacturing, Antibacterial and Wound Healing Activities

by Nagwa A. Elbhnsawi, Bassma H. Elwakil, Ahmed H. Hassanin, Nader Shehata, Salma Sameh Elshewemi, Mohamed Hagar and Zakia A. Olama

Membranes 2023, 13(6), 604; https://doi.org/10.3390/membranes13060604 - 15 Jun 2023

Cited by 4 | Viewed by 1792

Abstract

Accelerated wound healing in infected skin is still one of the areas where current therapeutic tactics fall short, which highlights the critical necessity for the exploration of new therapeutic approaches. The present study aimed to encapsulate Eucalyptus oil in a nano-drug carrier to [...] Read more.

Accelerated wound healing in infected skin is still one of the areas where current therapeutic tactics fall short, which highlights the critical necessity for the exploration of new therapeutic approaches. The present study aimed to encapsulate Eucalyptus oil in a nano-drug carrier to enhance its antimicrobial activity. Furthermore, in vitro, and in vivo wound healing studies of the novel nano-chitosan/Eucalyptus oil/cellulose acetate electrospun nanofibers were investigated. Eucalyptus oil showed a potent antimicrobial activity against the tested pathogens and the highest inhibition zone diameter, MIC, and MBC (15.3 mm, 16.0 μg/mL, and 256 μg/mL, respectively) were recorded against Staphylococcus aureus. Data indicated a three-fold increase in the antimicrobial activity of Eucalyptus oil encapsulated chitosan nanoparticle (43 mm inhibition zone diameter against S. aureus). The biosynthesized nanoparticles had a 48.26 nm particle size, 19.0 mV zeta potential, and 0.45 PDI. Electrospinning of nano-chitosan/Eucalyptus oil/cellulose acetate nanofibers was conducted, and the physico-chemical and biological properties revealed that the synthesized nanofibers were homogenous, with a thin diameter (98.0 nm) and a significantly high antimicrobial activity. The in vitro cytotoxic effect in a human normal melanocyte cell line (HFB4) proved an 80% cell viability using 1.5 mg/mL of nano-chitosan/Eucalyptus oil/cellulose acetate nanofibers. In vitro and in vivo wound healing studies revealed that nano-chitosan/Eucalyptus oil/cellulose acetate nanofibers were safe and efficiently enhanced the wound-healing process through enhancing TGF-β, type I and type III collagen production. As a conclusion, the manufactured nano-chitosan/Eucalyptus oil/cellulose acetate nanofiber showed effective potentiality for its use as a wound healing dressing. Full article

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

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12 pages, 3274 KiB

Open AccessArticle

Sintering Aid Strategy for Promoting Oxygen Reduction Reaction on High-Performance Double-Layer LaNi_0.6Fe_0.4O_3–δ Composite Electrode for Devices Based on Solid-State Membranes

by Denis Osinkin and Nina Bogdanovich

Membranes 2023, 13(6), 603; https://doi.org/10.3390/membranes13060603 - 15 Jun 2023

Cited by 4 | Viewed by 955

Abstract

Strontium and cobalt-free LaNi_0.6Fe_0.4O_3–δ is considered one of the most promising electrodes for solid-state electrochemical devices. LaNi_0.6Fe_0.4O_3–δ has high electrical conductivity, a suitable thermal expansion coefficient, satisfactory tolerance to chromium poisoning, and chemical [...] Read more.

Strontium and cobalt-free LaNi_0.6Fe_0.4O_3–δ is considered one of the most promising electrodes for solid-state electrochemical devices. LaNi_0.6Fe_0.4O_3–δ has high electrical conductivity, a suitable thermal expansion coefficient, satisfactory tolerance to chromium poisoning, and chemical compatibility with zirconia-based electrolytes. The disadvantage of LaNi_0.6Fe_0.4O_3–δ is its low oxygen-ion conductivity. In order to increase the oxygen-ion conductivity, a complex oxide based on a doped ceria is added to the LaNi_0.6Fe_0.4O_3–δ. However, this leads to a decrease in the conductivity of the electrode. In this case, a two-layer electrode with a functional composite layer and a collector layer with the addition of sintering additives should be used. In this study, the effect of sintering additives (Bi_0.75Y_0.25O_2–δ and CuO) in the collector layer on the performance of LaNi_0.6Fe_0.4O_3–δ-based highly active electrodes in contact with the most common solid-state membranes (Zr_0.84Sc_0.16O_2–δ, Ce_0.8Sm_0.2O_2–δ, La_0.85Sr_0.15Ga_0.85Mg_0.15O_3–δ, La₁₀(SiO₄)₆O_3–δ, and BaCe_0.89Gd_0.1Cu_0.01O_3–δ) was investigated. It was shown that LaNi_0.6Fe_0.4O_3–δ has good chemical compatibility with the abovementioned membranes. The best electrochemical activity (polarization resistance about 0.02 Ohm cm² at 800 °C) was obtained for the electrode with 5 wt.% Bi_0.75Y_0.25O_1.5 and 2 wt.% CuO in the collector layer. Full article

(This article belongs to the Section Membrane Applications)

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17 pages, 8351 KiB

Open AccessArticle

Impact of Silver-Decorated Graphene Oxide (Ag-GO) towards Improving the Characteristics of Nanohybrid Polysulfone Membranes

by Nur Syahirah Suhalim, Norherdawati Kasim, Ebrahim Mahmoudi, Intan Juliana Shamsudin, Nor Laili-Azua Jamari and Fathiah Mohamed Zuki

Membranes 2023, 13(6), 602; https://doi.org/10.3390/membranes13060602 - 15 Jun 2023

Cited by 2 | Viewed by 1227

Abstract

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the [...] Read more.

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the modification of membrane characteristics, including but not limited to hydrophilicity, morphology, and selectivity. In this study, a nanohybrid polysulfone (PSf) membrane embedded with silver–graphene oxide (Ag-GO) was fabricated to overcome problems related to biofouling. The embedment of Ag-GO nanoparticles (NPs) is the aim towards producing membranes with antimicrobial properties. The fabricated membranes at different compositions of NPs (0 wt%, 0.3 wt%, 0.5 wt%, and 0.8 wt%) are denoted as M0, M1, M2, and M3, respectively. These PSf/Ag-GO membranes were characterized using FTIR, water contact angle (WCA) goniometer, FESEM, and salt rejection. The additions of GO significantly improved the hydrophilicity of PSf membranes. An additional OH peak at 3380.84 cm⁻¹ of the nanohybrid membrane from FTIR spectra may be related to hydroxyl (-OH) groups of GO. The WCA of the fabricated membranes decreased from 69.92° to 54.71°, which confirmed the improvement in its hydrophilicity. In comparison to the pure PSf membrane, the morphology of the finger-like structure of the fabricated nanohybrid membrane slightly bent with a larger bottom part. Among the fabricated membranes, M2 achieved the highest iron (Fe) removal, up to 93%. This finding proved that the addition of 0.5 wt% Ag-GO NPs enhanced the membrane water permeability together with its performance of ionic solute removal (Fe²⁺) from synthetic groundwater. In conclusion, embedding a small amount of Ag-GO NPs successfully improved the hydrophilicity of PSf membranes and was able to achieve high removal of Fe at 10–100 mg L⁻¹ towards purification of groundwater for safe drinking water. Full article

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

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13 pages, 3636 KiB

Open AccessArticle

Long-Term Stable Complementary Electrochromic Device Based on WO₃ Working Electrode and NiO-Pt Counter Electrode

by Yajie Ke, Zitao Wang, Haiyi Xie, Mahmoud A. Khalifa, Jianming Zheng and Chunye Xu

Membranes 2023, 13(6), 601; https://doi.org/10.3390/membranes13060601 - 15 Jun 2023

Cited by 4 | Viewed by 1433

Abstract

Complementary electrochromic devices (ECDs) composed of WO₃ and NiO electrodes have wide applications in smart windows. However, they have poor cycling stability due to ion-trapping and charge mismatch between electrodes, which limits their practical application. In this work, we introduce a partially [...] Read more.

Complementary electrochromic devices (ECDs) composed of WO₃ and NiO electrodes have wide applications in smart windows. However, they have poor cycling stability due to ion-trapping and charge mismatch between electrodes, which limits their practical application. In this work, we introduce a partially covered counter electrode (CE) composed of NiO and Pt to achieve good stability and overcome the charge mismatch based on our structure of electrochromic electrode/Redox/catalytic counter electrode (ECM/Redox/CCE). The device is assembled using a NiO-Pt counter electrode with WO₃ as the working electrode, and PC/LiClO₄ containing a tetramethylthiourea/tetramethylformaminium disulfide (TMTU/TMFDS²⁺) redox couple as the electrolyte. The partially covered NiO-Pt CE-based ECD exhibits excellent EC performance, including a large optical modulation of 68.2% at 603 nm, rapid switching times of 5.3 s (coloring) and 12.8 s (bleaching), and a high coloration efficiency of 89.6 cm²·C⁻¹. In addition, the ECD achieves a good stability of 10,000 cycles, which is promising for practical application. These findings suggest that the structure of ECC/Redox/CCE could overcome the charge mismatch problem. Moreover, Pt could enhance the Redox couple’s electrochemical activity for achieving high stability. This research provides a promising approach for the design of long-term stable complementary electrochromic devices. Full article

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15 pages, 2588 KiB

Open AccessArticle

Interaction of Quercetin, Cyanidin, and Their O-Glucosides with Planar Lipid Models: Implications for Their Biological Effects

by Daniela Meleleo, Pinarosa Avato, Filomena Conforti, Maria Pia Argentieri, Giovanni Messina, Giuseppe Cibelli and Rosanna Mallamaci

Membranes 2023, 13(6), 600; https://doi.org/10.3390/membranes13060600 - 14 Jun 2023

Cited by 3 | Viewed by 1112

Abstract

Flavonoids are specialized metabolites produced by plants, as free aglycones or as glycosylated derivatives, which are particularly endowed with a variety of beneficial health properties. The antioxidant, anti-inflammatory, antimicrobial, anticancer, antifungal, antiviral, anti-Alzheimer’s, anti-obesity, antidiabetic, and antihypertensive effects of flavonoids are now known. [...] Read more.

Flavonoids are specialized metabolites produced by plants, as free aglycones or as glycosylated derivatives, which are particularly endowed with a variety of beneficial health properties. The antioxidant, anti-inflammatory, antimicrobial, anticancer, antifungal, antiviral, anti-Alzheimer’s, anti-obesity, antidiabetic, and antihypertensive effects of flavonoids are now known. These bioactive phytochemicals have been shown to act on different molecular targets in cells including the plasma membrane. Due to their polyhydroxylated structure, lipophilicity, and planar conformation, they can either bind at the bilayer interface or interact with the hydrophobic fatty acid tails of the membrane. The interaction of quercetin, cyanidin, and their O-glucosides with planar lipid membranes (PLMs) similar in composition to those of the intestine was monitored using an electrophysiological approach. The obtained results show that the tested flavonoids interact with PLM and form conductive units. The modality of interaction with the lipids of the bilayer and the alteration of the biophysical parameters of PLMs induced by the tested substances provided information on their location in the membrane, helping to elucidate the mechanism of action which underlies some pharmacological properties of flavonoids. To our knowledge, the interaction of quercetin, cyanidin, and their O-glucosides with PLM surrogates of the intestinal membrane has never been previously monitored. Full article

(This article belongs to the Special Issue Biological Membrane and Bioactive Compounds Interactions)

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13 pages, 11796 KiB

Open AccessArticle

Design and Preparation a New Composite Hydrophilic/Hydrophobic Membrane for Desalination by Pervaporation

by Tarik Eljaddi, Eric Favre and Denis Roizard

Membranes 2023, 13(6), 599; https://doi.org/10.3390/membranes13060599 - 13 Jun 2023

Cited by 2 | Viewed by 1114

Abstract

Herein, experimental and theoretical approaches were used to design a new composite membrane for desalination by pervaporation. The theoretical approaches demonstrate the possibility to reach high mass transfer coefficients quite close to those obtained with conventional porous membranes if two conditions are verified: [...] Read more.

Herein, experimental and theoretical approaches were used to design a new composite membrane for desalination by pervaporation. The theoretical approaches demonstrate the possibility to reach high mass transfer coefficients quite close to those obtained with conventional porous membranes if two conditions are verified: (i) a dense layer with a low thickness and (ii) a support with a high-water permeability. For this purpose, several membranes with a cellulose triacetate (CTA) polymer were prepared and compared with a hydrophobic membrane prepared in a previous study. The composite membranes were tested for several feed conditions, i.e., pure water, brine and saline water containing a surfactant. The results show that, whatever the tested feed, no wetting occurred during several hours of desalination tests. In addition, a steady flux was obtained together with a very high salt rejection (close to 100%) for the CTA membranes. Lastly, the CTA composite membrane was tested with real seawater without any pretreatment. It was shown that the salt rejection was still very high (close to 99.5%) and that no wetting could be detected for several hours. This investigation opens a new direction to prepare specific and sustainable membranes for desalination by pervaporation. Full article

(This article belongs to the Special Issue Advance in Membrane Technology for Environmental Protection and Remediation)

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13 pages, 12405 KiB

Open AccessArticle

Synthesis and Oxygen Mobility of Bismuth Cerates and Titanates with Pyrochlore Structure

by Yuliya Bespalko, Nikita Eremeev, Ekaterina Sadovskaya, Tamara Krieger, Olga Bulavchenko, Evgenii Suprun, Mikhail Mikhailenko, Mikhail Korobeynikov and Vladislav Sadykov

Membranes 2023, 13(6), 598; https://doi.org/10.3390/membranes13060598 - 13 Jun 2023

Cited by 2 | Viewed by 867

Abstract

Synthesis and study of materials based on bismuth cerates and titanates were carried out. Complex oxides Bi_1.6Y_0.4Ti₂O₇ were synthesized by the citrate route; Bi₂Ce₂O₇ and Bi_1.6Y_0.4Ce₂ [...] Read more.

Synthesis and study of materials based on bismuth cerates and titanates were carried out. Complex oxides Bi_1.6Y_0.4Ti₂O₇ were synthesized by the citrate route; Bi₂Ce₂O₇ and Bi_1.6Y_0.4Ce₂O₇—by the Pechini method. The structural characteristics of materials after conventional sintering at 500–1300 °C were studied. It is demonstrated that the formation of a pure pyrochlore phase, Bi_1.6Y_0.4Ti₂O₇, occurs after high-temperature calcination. Complex oxides Bi₂Ce₂O₇ and Bi_1.6Y_0.4Ce₂O₇ have a pyrochlore structure formed at low temperatures. Yttrium doping of bismuth cerate lowers the formation temperature of the pyrochlore phase. As a result of calcination at high temperatures, the pyrochlore phase transforms into the CeO₂-like fluorite phase enriched by bismuth oxide. The influence of radiation-thermal sintering (RTS) conditions using e-beams was studied as well. In this case, dense ceramics are formed even at sufficiently low temperatures and short processing times. The transport characteristics of the obtained materials were studied. It has been shown that bismuth cerates have high oxygen conductivity. Conclusions are drawn about the oxygen diffusion mechanism for these systems. The materials studied are promising for use as oxygen-conducting layers in composite membranes. Full article

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14 pages, 3486 KiB

Open AccessArticle

Integrated Electrocoagulation, Ultrafiltration, Membrane Distillation, and Crystallization for Treating Produced Water

by Mahmood Jebur, Yelyzaveta Bachynska, Xiaolei Hao and Sumith Ranil Wickramasinghe

Membranes 2023, 13(6), 597; https://doi.org/10.3390/membranes13060597 - 12 Jun 2023

Cited by 1 | Viewed by 1252

Abstract

Produced water (PW) generated from hydraulic fracturing operations was treated using an integrated electrocoagulation, ultrafiltration, membrane distillation, and crystallization process (EC UF MDC). The aim was to determine the viability of this integrated process for maximizing water recovery. The results obtained here indicate [...] Read more.

Produced water (PW) generated from hydraulic fracturing operations was treated using an integrated electrocoagulation, ultrafiltration, membrane distillation, and crystallization process (EC UF MDC). The aim was to determine the viability of this integrated process for maximizing water recovery. The results obtained here indicate that optimizing the various unit operations could lead to increased recovery of PW. Membrane fouling limits all membrane separation processes. A pretreatment step to suppress fouling is essential. Here, removal of total suspended solids (TSS) and total organic carbon (TOC) was achieved by electrocoagulation (EC) followed by ultrafiltration (UF). The hydrophobic membrane used in membrane distillation may be fouled by dissolved organic compounds. Reducing membrane fouling is essential to increase the long-term durability of the membrane distillation (MD) system. In addition, combining membrane distillation with crystallization (MDC) can help reduce scale formation. By inducing crystallization in the feed tank, scale formation on the MD membrane was suppressed. The integrated EC UF MDC process can impact Water Resources/Oil & Gas Companies. Conservation of surface and groundwater is possible by treating and reusing PW. Additionally, treating PW reduces the amount of PW disposed in Class II disposal wells and promotes more environmentally sustainable operations. Full article

(This article belongs to the Special Issue Membrane Distillation for Wastewater Purification)

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18 pages, 2857 KiB

Open AccessArticle

Modelling the Performance of Electrically Conductive Nanofiltration Membranes

by Alexey A. Kapitonov and Ilya I. Ryzhkov

Membranes 2023, 13(6), 596; https://doi.org/10.3390/membranes13060596 - 12 Jun 2023

Cited by 1 | Viewed by 1204

Abstract

Electrically conductive membranes are a class of stimuli-responsive materials, which allow the adjustment of selectivity for and the rejection of charged species by varying the surface potential. The electrical assistance provides a powerful tool for overcoming the selectivity–permeability trade-off due to its interaction [...] Read more.

Electrically conductive membranes are a class of stimuli-responsive materials, which allow the adjustment of selectivity for and the rejection of charged species by varying the surface potential. The electrical assistance provides a powerful tool for overcoming the selectivity–permeability trade-off due to its interaction with charged solutes, allowing the passage of neutral solvent molecules. In this work, a mathematical model for the nanofiltration of binary aqueous electrolytes by an electrically conductive membrane is proposed. The model takes into account the steric as well as Donnan exclusion of charged species due to the simultaneous presence of chemical and electronic surface charges. It is shown that the rejection reaches its minimum at the potential of zero charge (PZC), where the electronic and chemical charges compensate for each other. The rejection increases when the surface potential varies in positive and negative directions with respect to the PZC. The proposed model is successfully applied to a description of experimental data on the rejection of salts and anionic dyes by PANi–PSS/CNT and MXene/CNT nanofiltration membranes. The results provide new insights into the selectivity mechanisms of conductive membranes and can be employed to describe electrically enhanced nanofiltration processes. 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, 3818 KiB

Open AccessArticle

Effective Removal of Acetaldehyde Using Piperazine/Nitric Acid Co-Impregnated Bead-Type Activated Carbon

by Yu-Jin Kang, Yu-Jin Kim, Seong-Jin Yoon, Dong-Jin Seo, Hye-Ryeong Cho, Kyeongseok Oh, Seong-Ho Yoon and Joo-Il Park

Membranes 2023, 13(6), 595; https://doi.org/10.3390/membranes13060595 - 12 Jun 2023

Cited by 1 | Viewed by 1037

Abstract

Acetaldehyde (CH₃CHO) in the atmosphere is associated with adverse health effects. Among the various options for use in removing CH₃CHO, adsorption is often employed because of its convenient application and economical processes, particularly when using activated carbon. In previous [...] Read more.

Acetaldehyde (CH₃CHO) in the atmosphere is associated with adverse health effects. Among the various options for use in removing CH₃CHO, adsorption is often employed because of its convenient application and economical processes, particularly when using activated carbon. In previous studies, the surface of activated carbon has been modified with amines to remove CH₃CHO from the atmosphere via adsorption. However, these materials are toxic and can have harmful effects on humans when the modified activated carbon is used in air-purifier filters. Therefore, in this study, a customized bead-type activated carbon (BAC) with surface modification options via amination was evaluated for removing CH₃CHO. Various amounts of non-toxic piperazine or piperazine/nitric acid were used in amination. Chemical and physical analyses of the surface-modified BAC samples were performed using Brunauer–Emmett–Teller measurements, elemental analyses, and Fourier transform infrared and X-ray photoelectron spectroscopy. The chemical structures on the surfaces of the modified BACs were analyzed in detail using X-ray absorption spectroscopy. The amine and carboxylic acid groups on the surfaces of the modified BACs are critical in CH₃CHO adsorption. Notably, piperazine amination decreased the pore size and volume of the modified BAC, but piperazine/nitric acid impregnation maintained the pore size and volume of the modified BAC. In terms of CH₃CHO adsorption, piperazine/nitric acid impregnation resulted in a superior performance, with greater chemical adsorption. The linkages between the amine and carboxylic acid groups may function differently in piperazine amination and piperazine/nitric acid treatment. Full article

(This article belongs to the Special Issue Separation Techniques and Circular Economy)

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12 pages, 2774 KiB

Open AccessArticle

PEM Electrochemical Hydrogen Compression with Sputtered Pt Catalysts

by Galin Borisov, Nevelin Borisov, Jochen Heiss, Uwe Schnakenberg and Evelina Slavcheva

Membranes 2023, 13(6), 594; https://doi.org/10.3390/membranes13060594 - 12 Jun 2023

Cited by 2 | Viewed by 1557

Abstract

This work presents research on thin magnetron-sputtered platinum (Pt) films deposited over commercial gas diffusion electrodes and applied to convert and pressurize hydrogen in an electrochemical hydrogen pump. The electrodes were integrated into a membrane electrode assembly with a proton conductive membrane. Their [...] Read more.

This work presents research on thin magnetron-sputtered platinum (Pt) films deposited over commercial gas diffusion electrodes and applied to convert and pressurize hydrogen in an electrochemical hydrogen pump. The electrodes were integrated into a membrane electrode assembly with a proton conductive membrane. Their electrocatalytic efficiency toward hydrogen oxidation and hydrogen evolution reactions was studied in a self-made laboratory test cell by means of steady-state polarization curves and cell voltage measurements (U/j and U/p_diff characteristics). The achieved current density at a cell voltage of 0.5 V, the atmospheric pressure of the input hydrogen, and a temperature of 60 °C was more than 1.3 A cm⁻². The registered increase in the cell voltage with the increasing pressure was only 0.05 mV bar⁻¹. Comparative data with commercial E-TEK electrodes reveal the superior catalyst performance and essential cost reduction of the electrochemical hydrogen conversion on the sputtered Pt films. Full article

(This article belongs to the Special Issue Advanced Membranes for Energy Storage and Conversion)

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21 pages, 2022 KiB

Open AccessReview

Different Approaches for the Preparation of Composite Ionic Liquid-Based Membranes for Proton Exchange Membrane Fuel Cell Applications—Recent Advancements

by Mohammad Ebrahimi, Kateryna Fatyeyeva and Wojciech Kujawski

Membranes 2023, 13(6), 593; https://doi.org/10.3390/membranes13060593 - 11 Jun 2023

Cited by 1 | Viewed by 1573

Abstract

The use of ionic liquid-based membranes as polymer electrolyte membranes for fuel cell applications increases significantly due to the major features of ionic liquids (i.e., high thermal stability and ion conductivity, non-volatility, and non-flammability). In general, there are three major methods to introduce [...] Read more.

The use of ionic liquid-based membranes as polymer electrolyte membranes for fuel cell applications increases significantly due to the major features of ionic liquids (i.e., high thermal stability and ion conductivity, non-volatility, and non-flammability). In general, there are three major methods to introduce ionic liquids into the polymer membrane, such as incorporating ionic liquid into a polymer solution, impregnating the polymer with ionic liquid, and cross-linking. The incorporation of ionic liquids into a polymer solution is the most common method, owing to easy operation of process and quick membrane formation. However, the prepared composite membranes suffer from a reduction in mechanical stability and ionic liquid leakage. While mechanical stability may be enhanced by the membrane’s impregnation with ionic liquid, ionic liquid leaching is still the main drawback of this method. The presence of covalent bonds between ionic liquids and polymer chains during the cross-linking reaction can decrease the ionic liquid release. Cross-linked membranes reveal more stable proton conductivity, although a decrease in ionic mobility can be noticed. In the present work, the main approaches for ionic liquid introduction into the polymer film are presented in detail, and the recently obtained results (2019–2023) are discussed in correlation with the composite membrane structure. In addition, some promising new methods (i.e., layer-by-layer self-assembly, vacuum-assisted flocculation, spin coating, and freeze drying) are described. Full article

(This article belongs to the Special Issue Advanced Polymeric Membranes for Fuel Cell Applications)

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18 pages, 3973 KiB

Open AccessArticle

Examining the Effect of Ionizing Radiations in Ion-Exchange Membranes of Interest in Biomedical Applications

by Íñigo Lara, Yago Freijanes, Sagrario Muñoz, Gema Ruiz and V. María Barragán

Membranes 2023, 13(6), 592; https://doi.org/10.3390/membranes13060592 - 10 Jun 2023

Viewed by 998

Abstract

The possible effects of ionizing radiation on four commercial membranes, which are typically used as electrolytes in fuel cells supplying energy to a huge variety of medical implantable devices, were studied. These devices could obtain energy from the biological environment through a glucose [...] Read more.

The possible effects of ionizing radiation on four commercial membranes, which are typically used as electrolytes in fuel cells supplying energy to a huge variety of medical implantable devices, were studied. These devices could obtain energy from the biological environment through a glucose fuel cell, which could be a good candidate to replace conventional batteries as a power source. In these applications, materials with high radiation stability for the fuel cell elements would be disabled. The polymeric membrane is one of the key elements in fuel cells. Membrane swelling properties are very important because they affect the fuel cell’s performance. For this reason, the swelling behaviors of various samples of each membrane irradiated with different doses were analyzed. Each sample was irradiated with a typical dose of a conventional radiotherapy treatment, and the regular conditions of the biological working environment were simulated. The target was to examine the possible effect of the received radiation on the membranes. The results show that the ionizing radiation influenced their swelling properties, as well as that dimensional changes were dependent on the existence of reinforcement, be it internal or external, in the membrane structure. Full article

(This article belongs to the Special Issue Membranes and Membrane Processes in Medicine)

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21 pages, 46083 KiB

Open AccessArticle

The Development of Alginate/Ag NPs/Caffeic Acid Composite Membranes as Adsorbents for Water Purification

by Angela Spoială, Cornelia-Ioana Ilie, Georgiana Dolete, Gabriela Petrișor, Roxana-Doina Trușcă, Ludmila Motelica, Denisa Ficai, Anton Ficai, Ovidiu-Cristian Oprea and Mara-Lia Dițu

Membranes 2023, 13(6), 591; https://doi.org/10.3390/membranes13060591 - 09 Jun 2023

Cited by 7 | Viewed by 1245

Abstract

Since the water pollution problem still affects the environmental system and human health, the need to develop innovative membranes has become imperious. Lately, researchers have focused on developing novel materials to help diminish the contamination problem. The aim of present research was to [...] Read more.

Since the water pollution problem still affects the environmental system and human health, the need to develop innovative membranes has become imperious. Lately, researchers have focused on developing novel materials to help diminish the contamination problem. The aim of present research was to obtain innovative adsorbent composite membranes based on a biodegradable polymer, alginate, to remove toxic pollutants. Of all pollutants, lead was chosen due to its high toxicity. The composite membranes were successfully obtained through a direct casting method. The silver nanoparticles (Ag NPs) and caffeic acid (CA) from the composite membranes were kept at low concentrations, which proved enough to bestow antimicrobial activity to the alginate membrane. The obtained composite membranes were characterised by Fourier transform infrared spectroscopy and microscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TG-DSC). Swelling behaviour, lead ion (Pb²⁺) removal capacity, regeneration and reusability were also determined. Further, the antimicrobial activity was tested against selected pathogenic strains (S. aureus, E. faecalis sp., P. aeruginosa, E. coli and C. albicans). The presence of Ag NPs and CA improves the antimicrobial activity of the newly developed membranes. Overall, the composite membranes are suitable for complex water treatment (removal of heavy metal ions and antimicrobial treatment). Full article

(This article belongs to the Special Issue Surface Modification and Performance Enhancement for Membranes)

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36 pages, 5504 KiB

Open AccessReview

Recent Advanced Synthesis Strategies for the Nanomaterial-Modified Proton Exchange Membrane in Fuel Cells

by Somasundaram Chandra Kishore, Suguna Perumal, Raji Atchudan, Muthulakshmi Alagan, Mohammad Ahmad Wadaan, Almohannad Baabbad and Devaraj Manoj

Membranes 2023, 13(6), 590; https://doi.org/10.3390/membranes13060590 - 09 Jun 2023

Cited by 3 | Viewed by 2157

Abstract

Hydrogen energy is converted to electricity through fuel cells, aided by nanostructured materials. Fuel cell technology is a promising method for utilizing energy sources, ensuring sustainability, and protecting the environment. However, it still faces drawbacks such as high cost, operability, and durability issues. [...] Read more.

Hydrogen energy is converted to electricity through fuel cells, aided by nanostructured materials. Fuel cell technology is a promising method for utilizing energy sources, ensuring sustainability, and protecting the environment. However, it still faces drawbacks such as high cost, operability, and durability issues. Nanomaterials can address these drawbacks by enhancing catalysts, electrodes, and fuel cell membranes, which play a crucial role in separating hydrogen into protons and electrons. Proton exchange membrane fuel cells (PEMFCs) have gained significant attention in scientific research. The primary objectives are to reduce greenhouse gas emissions, particularly in the automotive industry, and develop cost-effective methods and materials to enhance PEMFC efficiency. We provide a typical yet inclusive review of various types of proton-conducting membranes. In this review article, special focus is given to the distinctive nature of nanomaterial-filled proton-conducting membranes and their essential characteristics, including their structural, dielectric, proton transport, and thermal properties. We provide an overview of the various reported nanomaterials, such as metal oxide, carbon, and polymeric nanomaterials. Additionally, the synthesis methods in situ polymerization, solution casting, electrospinning, and layer-by-layer assembly for proton-conducting membrane preparation were analyzed. In conclusion, the way to implement the desired energy conversion application, such as a fuel cell, using a nanostructured proton-conducting membrane has been demonstrated. Full article

(This article belongs to the Special Issue Proton-Conducting Membranes)

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18 pages, 1707 KiB

Open AccessArticle

Analysis of the Polyphenolic Composition of Vaccinium L. Extracts and Their Protective Effect on Red Blood Cell Membranes

by Teresa Kaźmierczak, Dorota Bonarska-Kujawa, Katarzyna Męczarska, Sylwia Cyboran-Mikołajczyk, Jan Oszmiański and Ireneusz Kapusta

Membranes 2023, 13(6), 589; https://doi.org/10.3390/membranes13060589 - 07 Jun 2023

Viewed by 1180

Abstract

The blueberry fruit of the genus Vaccinium, including high blueberry, low blueberry, and wild bilberry, is consumed for its flavor and medicinal properties. The purpose of the experiments was to investigate the protective effect and mechanism of the interaction of blueberry fruit [...] Read more.

The blueberry fruit of the genus Vaccinium, including high blueberry, low blueberry, and wild bilberry, is consumed for its flavor and medicinal properties. The purpose of the experiments was to investigate the protective effect and mechanism of the interaction of blueberry fruit polyphenol extracts with the erythrocytes and their membranes. The content of polyphenolic compounds in the extracts was determined using the chromatographic UPLC–ESI–MS method. The effects of the extracts on red blood cell shape changes, hemolysis and osmotic resistance were examined. Changes in the order of packing and fluidity of the erythrocyte membrane and the lipid membrane model caused by the extracts were identified using fluorimetric methods. Erythrocyte membrane oxidation was induced by two agents: AAPH compound and UVC radiation. The results show that the tested extracts are a rich source of low molecular weight polyphenols that bind to the polar groups of the erythrocyte membrane, changing the properties of its hydrophilic area. However, they practically do not penetrate the hydrophobic part of the membrane and do not damage its structure. Research results suggest that the components of the extracts can defend the organism against oxidative stress if they are delivered to the organism in the form of dietary supplements. Full article

(This article belongs to the Special Issue Prospects for Application of Natural Compounds and Their Derivatives in Biological and Artificial Membranes)

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15 pages, 2793 KiB

Open AccessArticle

Using the Log Mean Temperature Difference (LMTD) and ε-NTU Methods to Analyze Heat and Mass Transfer in Direct Contact Membrane Distillation

by Mohammed A. Almeshaal and Karim Choubani

Membranes 2023, 13(6), 588; https://doi.org/10.3390/membranes13060588 - 07 Jun 2023

Cited by 1 | Viewed by 3456

Abstract

In direct contact membrane distillation (DCMD), heat and mass transfers occur through the porous membrane. Any model developed for the DCMD process should therefore be able to describe the mass transport mechanism through the membrane, the temperature and concentration effects on the surface [...] Read more.

In direct contact membrane distillation (DCMD), heat and mass transfers occur through the porous membrane. Any model developed for the DCMD process should therefore be able to describe the mass transport mechanism through the membrane, the temperature and concentration effects on the surface of the membrane, the permeate flux, and the selectivity of the membrane. In the present study, we developed a predictive mathematical model based on a counter flow heat exchanger analogy for the DCMD process. Two methods were used to analyze the water permeate flux across one hydrophobic membrane layer, namely the log mean temperature difference (LMTD) and the effectiveness-NTU methods. The set of equations was derived in a manner analogous to that employed for heat exchanger systems. The obtained results showed that the permeate flux increases by a factor of approximately 220% when increasing the log mean temperature difference by a factor of 80% or increasing the number of transfer units by a factor of 3%. A good level of agreement between this theoretical model and the experimental data at various feed temperatures confirmed that the model accurately predicts the permeate flux values for the DCMD process. Full article

(This article belongs to the Special Issue Membrane-Based Technologies for Water/Wastewater Treatment)

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13 pages, 7861 KiB

Open AccessArticle

The Effect of Divinylbenzene on the Structure and Properties of Polyethylene Films with Related Radiation Chemical Grafted Polystyrene and Sulfocationite Membranes

by Anatoly E. Chalykh, Ramil R. Khasbiullin, Ali D. Aliev, Vladimir V. Matveev, Vladimir K. Gerasimov, Nikita A. Slesarenko, Irina A. Avilova, Vitaly I. Volkov and Vladimir A. Tverskoy

Membranes 2023, 13(6), 587; https://doi.org/10.3390/membranes13060587 - 07 Jun 2023

Viewed by 1001

Abstract

In the present work, the effect of divinylbenzene (DVB) on the kinetics of post-radiation chemical graft polymerization styrene (St) on polyethylene (PE) film and its structural and morphological features were investigated. It has been found that the dependence of the degree of polystyrene [...] Read more.

In the present work, the effect of divinylbenzene (DVB) on the kinetics of post-radiation chemical graft polymerization styrene (St) on polyethylene (PE) film and its structural and morphological features were investigated. It has been found that the dependence of the degree of polystyrene (PS) grafting on the DVB concentration in the solution is extreme. An increase in the rate of graft polymerization at low concentrations of DVB in the solution is associated with a decrease in the mobility of the growing chains of PS. A decrease in the rate of graft polymerization at high concentrations of DVB is associated with a decrease in the rate of diffusion of St and iron(II) ions in the cross-linked network structure of macromolecules of graft PS. A comparative analysis of the IR transmission and multiple attenuated total internal reflection spectra of the films with graft PS shows that graft polymerization of St in the presence of DVB leads to the enrichment of the film surface layers in PS. These results have been confirmed by the data on the distribution of sulfur in these films after sulfonation. The micrographs of the surface of the grafted films show the formation of cross-linked local microphases of PS with fixed interfaces. Full article

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

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13 pages, 8443 KiB

Open AccessArticle

Long-Term Conductivity Stability of Electrolytic Membranes of Scandia Stabilized Zirconia Co-Doped with Ytterbia

by Dmitrii Agarkov, Mikhail Borik, Boris Komarov, Galina Korableva, Alexey Kulebyakin, Irina Kuritsyna, Elena Lomonova, Filipp Milovich, Valentina Myzina and Nataliya Tabachkova

Membranes 2023, 13(6), 586; https://doi.org/10.3390/membranes13060586 - 06 Jun 2023

Cited by 2 | Viewed by 1126

Abstract

The effect of high-temperature aging for 4800 h at a temperature of 1123 K on the crystal structure and the conductivity of (ZrO₂)_0.90(Sc₂O₃)_0.09(Yb₂O₃)_0.01 and (ZrO₂)_0.90 [...] Read more.

The effect of high-temperature aging for 4800 h at a temperature of 1123 K on the crystal structure and the conductivity of (ZrO₂)_0.90(Sc₂O₃)_0.09(Yb₂O₃)_0.01 and (ZrO₂)_0.90(Sc₂O₃)_0.08(Yb₂O₃)_0.02 single-crystal membranes were studied. Such membrane lifetime testing is critical to the operation of solid oxide fuel cells (SOFCs). The crystals were obtained by the method of directional crystallization of the melt in a cold crucible. The phase composition and structure of the membranes before and after aging were studied using X-ray diffraction and Raman spectroscopy. The conductivities of the samples were measured using the impedance spectroscopy technique. The (ZrO₂)_0.90(Sc₂O₃)_0.09(Yb₂O₃)_0.01 composition showed long-term conductivity stability (conductivity degradation not more than 4%). Long-term high-temperature aging of the (ZrO₂)_0.90(Sc₂O₃)_0.08(Yb₂O₃)_0.02 composition initiates the t″ → t′ phase transformation. In this case, a sharp decrease in conductivity of up to 55% was observed. The data obtained demonstrate a clear correlation between the specific conductivity and the change in the phase composition. The (ZrO₂)_0.90(Sc₂O₃)_0.09(Yb₂O₃)_0.01 composition can be considered a promising material for practical use as a solid electrolyte in SOFCs. Full article

(This article belongs to the Special Issue Membrane Technology for Solid Oxide Fuel Cells)

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14 pages, 5109 KiB

Open AccessArticle

Solid Oxide Fuel Cells with Magnetron Sputtered Single-Layer SDC and Multilayer SDC/YSZ/SDC Electrolytes

by Andrey Solovyev, Anna Shipilova and Egor Smolyanskiy

Membranes 2023, 13(6), 585; https://doi.org/10.3390/membranes13060585 - 05 Jun 2023

Cited by 3 | Viewed by 1641

Abstract

Samarium-doped ceria (SDC) is considered as an alternative electrolyte material for intermediate-temperature solid oxide fuel cells (IT-SOFCs) because its conductivity is higher than that of commonly used yttria-stabilized zirconia (YSZ). The paper compares the properties of anode-supported SOFCs with magnetron sputtered single-layer SDC [...] Read more.

Samarium-doped ceria (SDC) is considered as an alternative electrolyte material for intermediate-temperature solid oxide fuel cells (IT-SOFCs) because its conductivity is higher than that of commonly used yttria-stabilized zirconia (YSZ). The paper compares the properties of anode-supported SOFCs with magnetron sputtered single-layer SDC and multilayer SDC/YSZ/SDC thin-film electrolyte, with the YSZ blocking layer 0.5, 1, and 1.5 μm thick. The thickness of the upper and lower SDC layers of the multilayer electrolyte are constant and amount to 3 and 1 μm, respectively. The thickness of single-layer SDC electrolyte is 5.5 μm. The SOFC performance is studied by measuring current–voltage characteristics and impedance spectra in the range of 500–800 °C. X-ray diffraction and scanning electron microscopy are used to investigate the structure of the deposited electrolyte and other fuel cell layers. SOFCs with the single-layer SDC electrolyte show the best performance at 650 °C. At this temperature, open circuit voltage and maximum power density are 0.8 V and 651 mW/cm², respectively. The formation of the SDC electrolyte with the YSZ blocking layer improves the open circuit voltage up to 1.1 V and increases the maximum power density at the temperatures over 600 °C. It is shown that the optimal thickness of the YSZ blocking layer is 1 µm. The fuel cell with the multilayer SDC/YSZ/SDC electrolyte, with the layer thicknesses of 3/1/1 µm, has the maximum power density of 2263 and 1132 mW/cm² at 800 and 650 °C, respectively. Full article

(This article belongs to the Special Issue Fabrication, Characterization and Application of Organic/Inorganic Film Membranes and Advanced Materials (Volume II))

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19 pages, 10882 KiB

Open AccessArticle

An Electrochemistry and Computational Study at an Electrified Liquid–Liquid Interface for Studying Beta-Amyloid Aggregation

by Bongiwe Silwane, Mark Wilson and Ritu Kataky

Membranes 2023, 13(6), 584; https://doi.org/10.3390/membranes13060584 - 05 Jun 2023

Viewed by 1106

Abstract

Amphiphilic peptides, such as Aß amyloids, can adsorb at an interface between two immiscible electrolyte solutions (ITIES). Based on previous work (vide infra), a hydrophilic/hydrophobic interface is used as a simple biomimetic system for studying drug interactions. The ITIES provides a 2D interface [...] Read more.

Amphiphilic peptides, such as Aß amyloids, can adsorb at an interface between two immiscible electrolyte solutions (ITIES). Based on previous work (vide infra), a hydrophilic/hydrophobic interface is used as a simple biomimetic system for studying drug interactions. The ITIES provides a 2D interface to study ion-transfer processes associated with aggregation, as a function of Galvani potential difference. Here, the aggregation/complexation behaviour of Aβ_(1-42) is studied in the presence of Cu (II) ions, together with the effect of a multifunctional peptidomimetic inhibitor (P6). Cyclic and differential pulse voltammetry proved to be particularly sensitive to the detection of the complexation and aggregation of Aβ_(1-42), enabling estimations of changes in lipophilicity upon binding to Cu (II) and P6. At a 1:1 ratio of Cu (II):Aβ_(1-42), fresh samples showed a single DPV (Differential Pulse Voltammetry) peak half wave transfer potential (E1/2) at 0.40 V. Upon increasing the ratio of Cu (II) two-fold, fluctuations were observed in the DPVs, indicating aggregation. The approximate stoichiometry and binding properties of Aβ_(1-42) during complexation with Cu (II) were determined by performing a differential pulse voltammetry (DPV) standard addition method, which showed two binding regimes. A pKa of 8.1 was estimated, with a Cu:Aβ_1-42 ratio~1:1.7. Studies using molecular dynamics simulations of peptides at the ITIES show that Aβ_(1-42) strands interact through the formation of β-sheet stabilised structures. In the absence of copper, binding/unbinding is dynamic, and interactions are relatively weak, leading to the observation of parallel and anti-parallel arrangements of β-sheet stabilised aggregates. In the presence of copper ions, strong binding occurs between a copper ion and histidine residues on two peptides. This provides a convenient geometry for inducing favourable interactions between folded β-sheet structures. Circular Dichroism spectroscopy (CD spectroscopy) was used to support the aggregation behaviour of the Aβ_(1-42) peptides following the addition of Cu (II) and P6 to the aqueous phase. Full article

(This article belongs to the Special Issue Advances in Artiﬁcial and Biological Membranes, Volume II)

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17 pages, 4727 KiB

Open AccessArticle

Role of Calcium-Activated Potassium Channels in Proliferation, Migration and Invasion of Human Chronic Myeloid Leukemia K562 Cells

by Valeria Y. Vasileva, Zuleikha M. Khairullina, Anastasia V. Sudarikova and Vladislav I. Chubinskiy-Nadezhdin

Membranes 2023, 13(6), 583; https://doi.org/10.3390/membranes13060583 - 04 Jun 2023

Cited by 2 | Viewed by 1490

Abstract

Calcium-activated potassium channels (KCa) are important participants in calcium signaling pathways due to their ability to be activated by an increase in intracellular free calcium concentration. KCa channels are involved in the regulation of cellular processes in both normal and pathophysiological conditions, including [...] Read more.

Calcium-activated potassium channels (KCa) are important participants in calcium signaling pathways due to their ability to be activated by an increase in intracellular free calcium concentration. KCa channels are involved in the regulation of cellular processes in both normal and pathophysiological conditions, including oncotransformation. Previously, using patch-clamp, we registered the KCa currents in the plasma membrane of human chronic myeloid leukemia K562 cells, whose activity was controlled by local Ca²⁺ entry via mechanosensitive calcium-permeable channels. Here, we performed the molecular and functional identification of KCa channels and have uncovered their role in the proliferation, migration and invasion of K562 cells. Using a combined approach, we identified the functional activity of SK2, SK3 and IK channels in the plasma membrane of the cells. Selective SK and IK channel inhibitors, apamin and TRAM-34, respectively, reduced the proliferative, migratory and invasive capabilities of human myeloid leukemia cells. At the same time, the viability of K562 cells was not affected by KCa channel inhibitors. Ca²⁺ imaging showed that both SK and IK channel inhibitors affect Ca²⁺ entry and this could underlie the observed suppression of pathophysiological reactions of K562 cells. Our data imply that SK/IK channel inhibitors could be used to slow down the proliferation and spreading of chronic myeloid leukemia K562 cells that express functionally active KCa channels in the plasma membrane. Full article

(This article belongs to the Special Issue Membrane Permeability and Channels, Volume II)

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