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Membranes, Volume 12, Issue 10 (October 2022) – 122 articles

Cover Story (view full-size image): The problem of water purification is relevant due to the continuous increase in the level of pollution of natural water sources and sharp climatic changes. The amount of water pollution increases with the increase in production capacity, the purification of which cannot be fully handled by conventional processes. The application of novel nanomaterials will enhance the features of water treatment processes. In this review, the application of carbon nanomaterials in membrane water purification was considered. The ways to solve the problems with the application of various carbon nanomaterials in membrane processes were discussed. Their efficiency, properties, and characteristics as a modifier for membranes were analyzed. View this paper
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12 pages, 3331 KiB  
Article
Study on the Actuation Properties of Polyurethane Fiber Membranes Filled with PEG-SWNTs Dielectric Microcapsules
by Gang Lu, Changgeng Shuai, Yinsong Liu and Xue Yang
Membranes 2022, 12(10), 1026; https://doi.org/10.3390/membranes12101026 - 21 Oct 2022
Cited by 1 | Viewed by 1284
Abstract
Polyurethane dielectric elastomer (PUDE), a typical representative of emerging intelligent materials, has advantages, such as good elasticity and flexibility, fast response speed, high electromechanical conversion efficiency, and strong environmental tolerance. It has promising applications in underwater bionic actuators, but its electromechanical properties should [...] Read more.
Polyurethane dielectric elastomer (PUDE), a typical representative of emerging intelligent materials, has advantages, such as good elasticity and flexibility, fast response speed, high electromechanical conversion efficiency, and strong environmental tolerance. It has promising applications in underwater bionic actuators, but its electromechanical properties should be improved further. In this context, the design of polyethylene glycol (PEG) single-walled carbon nanotube (SWNTs) dielectric microcapsules was adopted to balance the problem of contradictions, which conventional dielectric modification methods face between comprehensive properties (e.g., dielectric properties and modulus). Moreover, the dielectric microcapsule was evenly filled into the polyurethane fiber by coaxial spinning technology to enhance the actuation performance and instability of the electrical breakdown threshold of conventional polyurethane dielectric modification. It was revealed that the dielectric microcapsules were oriented in the polyurethane fiber, and the actuation performance of the composite fiber membrane was significantly better than that of the polyurethane fiber membrane filled with SWNTs, thus confirming that the filling design of the dielectric microcapsules in polyurethane fiber could have certain technical advantages. On that basis, this study provides a novel idea for the dielectric modification of polyurethane. Full article
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21 pages, 10720 KiB  
Article
Ti3C2 MXene Membranes for Gas Separation: Influence of Heat Treatment Conditions on D-Spacing and Surface Functionalization
by Aline Alencar Emerenciano, Rubens Maribondo do Nascimento, Ana Paula Cysne Barbosa, Ke Ran, Wilhelm Albert Meulenberg and Jesus Gonzalez-Julian
Membranes 2022, 12(10), 1025; https://doi.org/10.3390/membranes12101025 - 21 Oct 2022
Cited by 11 | Viewed by 2622
Abstract
Two-dimensional (2D) MXene materials have recently been the focus of membrane research due to their unique properties, such as their single-atomic-layer thickness, flexibility, molecular filtration abilities and microstructural similarities with graphene, which is currently the most efficient precursor material for gas separation applications. [...] Read more.
Two-dimensional (2D) MXene materials have recently been the focus of membrane research due to their unique properties, such as their single-atomic-layer thickness, flexibility, molecular filtration abilities and microstructural similarities with graphene, which is currently the most efficient precursor material for gas separation applications. In addition, the potential to process nanoscale channels has motivated investigations of parameters which can improve membrane permeability and selectivity. Interlayer spacing and defects, which are still challenging to control, are among the most crucial parameters for membrane performance. Herein, the effect of heat treatment on the d-spacing of MXene nanosheets and the surface functionalization of nanolayers was shown regarding its impact on the gas diffusion mechanism. The distance of the layers was reduced by a factor of over 10 from 0.345 nm to 0.024 nm, the defects were reduced, and the surface functionalization was maintained upon treatment of the Ti3C2 membrane at 500 °C under an Ar/H2 atmosphere as compared to 80 °C under vacuum. This led to a change from Knudsen diffusion to molecular sieving, as demonstrated by single-gas permeation tests at room temperature. Overall, this work shows a simple and promising way to improve H2/CO2 selectivity via temperature treatment under a controlled atmosphere. Full article
(This article belongs to the Topic Membrane Separation Technology Research)
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17 pages, 6994 KiB  
Article
Obtaining and Characterizing the Osmium Nanoparticles/n–Decanol Bulk Membrane Used for the p–Nitrophenol Reduction and Separation System
by Aurelia Cristina Nechifor, Alexandru Goran, Szidonia-Katalin Tanczos, Florentina Mihaela Păncescu, Ovidiu-Cristian Oprea, Alexandra Raluca Grosu, Cristian Matei, Vlad-Alexandru Grosu, Bogdan Ștefan Vasile and Paul Constantin Albu
Membranes 2022, 12(10), 1024; https://doi.org/10.3390/membranes12101024 - 21 Oct 2022
Cited by 5 | Viewed by 1485
Abstract
Liquid membranes based on nanoparticles follow a continuous development, both from obtaining methods and characterization of techniques points of view. Lately, osmium nanoparticles have been deposited either on flat membranes, with the aim of initiating some reaction processes, or on hollow fiber membranes, [...] Read more.
Liquid membranes based on nanoparticles follow a continuous development, both from obtaining methods and characterization of techniques points of view. Lately, osmium nanoparticles have been deposited either on flat membranes, with the aim of initiating some reaction processes, or on hollow fiber membranes, with the aim of increasing the contact surface with the phases of the membrane system. This paper presents the obtainment and characterization of a liquid membrane based on osmium nanoparticles (Os–NP) dispersed in ndecanol (nDol) for the realization of a membrane system with a large contact surface between the phases, but without using a liquid membrane support. The dispersion of osmium nanoparticles in n-decanol is carried out by the method of reducing osmium tetroxide with 1–undecenoic acid (UDA). The resulting membrane was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy analysis (EDAX), thermoanalysis (TG, DSC), Fourier transform infra-red (FTIR) spectroscopy and dynamic light scattering (DLS). In order to increase the mass transfer surface, a design for the membrane system was realized with the dispersion of the membrane through the receiving phase and the dispersion of the source phase through the membrane (DBLM-dispersion bulk liquid membrane). The process performance was tested for the reduction of p–nitrophenol (pNP) from the source phase, using sodium tetra-borohydride (NaBH4), to p–aminophenol (pAP), which was transported and collected in the receiving phase. The obtained results show that membranes based on the dispersion of osmium nanoparticles in n–decanol can be used with an efficiency of over 90% for the reduction of p–nitrophenol and the separation of p–aminophenol. Full article
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11 pages, 3278 KiB  
Article
Increased Tropism of Extracellular Vesicles Derived from Palmitic Acid-Treated Hepatocytes to Activated Hepatic Stellate Cells
by Momoka Yamaguchi, Takanori Kanazawa, Sumire Morino, Shingo Iioka, Yuta Watanabe, Naoki Dohi, Kenjirou Higashi, Hiromu Kondo and Tomohisa Ishikawa
Membranes 2022, 12(10), 1023; https://doi.org/10.3390/membranes12101023 - 21 Oct 2022
Viewed by 1954
Abstract
Myofibroblast-like activated hepatic stellate cells (aHSCs), which produce collagen, a major cause of liver fibrosis, are specific target cells for antifibrotic treatment. Recently, several reports have indicated that extracellular vesicles (EVs) play important roles in cell-to-cell communication through their tropism for specific cells [...] Read more.
Myofibroblast-like activated hepatic stellate cells (aHSCs), which produce collagen, a major cause of liver fibrosis, are specific target cells for antifibrotic treatment. Recently, several reports have indicated that extracellular vesicles (EVs) play important roles in cell-to-cell communication through their tropism for specific cells or organs. Therefore, the present study aimed to identify aHSC-directed EVs by focusing on cell-to-cell interactions in the liver under pathological conditions. EVs were derived from the hepatocyte cell line AML12 treated with or without palmitic acid (PA) and evaluated for their physical properties and uptake by the aHSC cell line LX-2. AML12-derived EVs had a mean particle diameter of 110–130 nm, negative charge, and expressed the exosomal makers CD9 and CD63. PA-treated AML12 cells released larger EVs with higher protein levels than those without PA treatment. The intracellular uptake efficacy of EVs derived from PA-treated AML12 cells into activated LX-2 cells was significantly higher than those without PA treatment. Our study revealed that PA treatment induces hepatocytes to release EVs with aHSC-tropism. These findings may contribute to the development of an EV-based drug delivery system (DDS) for aHSC-targeted therapy and provide new insights into the role of steatotic hepatocyte-derived EVs in physiological or pathophysiological functions. Full article
(This article belongs to the Special Issue Functional Analysis and Applications of Membrane Lipids)
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20 pages, 6649 KiB  
Article
Modelling Analysis of a Membrane-Based Fresh Air Processing System
by Sebastian Englart and Krzysztof Rajski
Membranes 2022, 12(10), 1022; https://doi.org/10.3390/membranes12101022 - 20 Oct 2022
Cited by 2 | Viewed by 1246
Abstract
The current standard of residential buildings is based on well-insulated and airtight construction as an effective way to reduce primary energy consumption. On the other hand, this intensifies the issue of the indoor air quality. In this paper, the applicability of a hybrid [...] Read more.
The current standard of residential buildings is based on well-insulated and airtight construction as an effective way to reduce primary energy consumption. On the other hand, this intensifies the issue of the indoor air quality. In this paper, the applicability of a hybrid dehumidification/evaporative cooling system for the processing and supply of fresh air is evaluated. The proposed novel system employs cross-flow hollow-fiber membrane modules. To provide a better insight into this novel approach, the system’s performance is numerically investigated using a validated mathematical model. The proposed fresh air processing system provides supply air parameters in or close to the summer comfort range. The analyzed system is characterized by a high coefficient of performance (COP) of up to 33.2 at an outdoor air temperature in the range of 30 °C to 38 °C and a humidity ratio in the range of 8 g/kg to 14 g/kg. Moreover, a temperature difference of up to 9.7 °C can be obtained after the two-stage membrane processing and the mixing process. Full article
(This article belongs to the Collection Feature Papers in Membrane Engineering and Applications)
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20 pages, 4203 KiB  
Article
Two-Dimensional Conjugated Mass Transfer of Carbon Dioxide Absorption in a Hollow-Fiber Gas-Liquid Membrane Contactor
by Chii-Dong Ho, Luke Chen, Chien-Chang Huang, Chien-Hua Chen, Thiam Leng Chew and Yu-Han Chen
Membranes 2022, 12(10), 1021; https://doi.org/10.3390/membranes12101021 - 20 Oct 2022
Cited by 1 | Viewed by 1299
Abstract
The absorption efficiencies of CO2 in hollow-fiber membrane contactors using an ethanolamine (MEA) solvent under both concurrent- and countercurrent-flow operations were investigated theoretically and experimentally. Two-dimensional mathematical modeling was developed by Happel’s free surface model, and the resultant partial differential equations were [...] Read more.
The absorption efficiencies of CO2 in hollow-fiber membrane contactors using an ethanolamine (MEA) solvent under both concurrent- and countercurrent-flow operations were investigated theoretically and experimentally. Two-dimensional mathematical modeling was developed by Happel’s free surface model, and the resultant partial differential equations were solved analytically using the separated variables method with the use of an orthogonal expansion technique. A simplified expression of Sherwood number variations was reported by employing the relevant operations conditions and expressed in terms of the computed eigenvalues for predicting concentration distribution and absorption efficiency. It is emphasized that, in comparing various fiber packing configurations, both theoretical predictions and experimental results should be compared to find the absorption flux increment accomplished by the CO2/N2 stream passing through the fiber cells under the same mass flow rate. The value of the present mathematical treatment is evident to propose a simplified expression of the averaged Sherwood number variations, and provides the predictions of the absorption flux, absorption efficiency, average Sherwood number with the absorbent Graetz number, inlet CO2 concentration, and absorbent flow rates as parameters. The availability of such concise expressions, as developed directly from the analytical formulations, is the value of the present study. The experiments of the CO2 absorption using MEA with alumina (Al2O3) hollow fiber membranes are also set up to confirm the accuracy of the theoretical predictions. The accuracy derivations between the experimental results and theoretical predictions for concurrent- and countercurrent-flow operations are 4.10×102E1.50×102 and 1.40×102E9.0×101, respectively. The operations of the hollow-fiber membrane contactor implementing N = 7 fiber cells and N = 19 fiber cells offer an inexpensive method of improving absorption efficiency by increasing fiber numbers with consideration of device performance. Full article
(This article belongs to the Section Inorganic Membranes)
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27 pages, 4321 KiB  
Article
Fabrication and Characterisation of MWCNT/Polyvinyl (PVC) Polymer Inclusion Membrane for Zinc (II) Ion Removal from Aqueous Solution
by Nadia Aqilah Khalid, Noor Fazliani Shoparwe, Abdul Hafidz Yusoff, Ahmad Ziad Sulaiman, Abdul Latif Ahmad and Nur Aina Azmi
Membranes 2022, 12(10), 1020; https://doi.org/10.3390/membranes12101020 - 20 Oct 2022
Cited by 2 | Viewed by 1606
Abstract
Heavy metal pollution has prompted researchers to establish the most effective method to tackle the impacts of heavy metals on living things and the environment, which include by applying nanoparticles. An example is the employment of multi-walled carbon nanotubes (MWCNTs) as an additive [...] Read more.
Heavy metal pollution has prompted researchers to establish the most effective method to tackle the impacts of heavy metals on living things and the environment, which include by applying nanoparticles. An example is the employment of multi-walled carbon nanotubes (MWCNTs) as an additive in an intermediate membrane or polymer inclusion membrane (PIM). The MWCNTs were added to enhance the properties and reinforce the transport performance of zinc (II) ion (Zn2+) removal from the source phase to the receiver phase by the PIMs. The present study constructed a membrane with a poly(vinyl chloride) (PVC)-based polymer, dioctyl phthalate (DOP) plasticiser, and bis-(2-ethylhexyl) phosphate (B2EHP) carrier incorporated with different concentrations of MWCNTs. The contact angle (CA), water uptake, ion exchange capacity (IEC), and porosity of the fabricated membranes were evaluated. The membrane was also characterised by employing scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). Subsequently, the fabricated PIM (W1) and mixed matrix (MM)-PIM (W2–W5) samples were assessed under different parameters to acquire the ideal membrane composition and effectiveness. Kinetic modelling of Zn2+ removal by the fabricated PIMs under similar conditions was performed to reveal the mechanisms involved. The average removal efficiency of the membranes was >99% at different parameter conditions. Nevertheless, the W3 membrane with 1.0 wt% MWCNT immersed in a 5 mg/L initial Zn2+ concentration and 1.0 M receiver solution for seven hours at pH 2 demonstrated the highest percentage of Zn2+ removal. The experimental data were best fitted to the pseudo-first-order kinetic model (PFO) in kinetic modelling, and the permeability and flux of the W3 at optimum conditions were 0.053 m s−1 and 0.0532 mol m−2 s−1, respectively. In conclusion, the transport mechanism of Zn2+ was enhanced with the addition of the MWCNTs. Full article
(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))
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18 pages, 904 KiB  
Article
Determination of Single-Ion Partition Coefficients between Water and Plasticized PVC Membrane Using Equilibrium-Based Techniques
by Andrei V. Siamionau and Vladimir V. Egorov
Membranes 2022, 12(10), 1019; https://doi.org/10.3390/membranes12101019 - 20 Oct 2022
Cited by 1 | Viewed by 2354
Abstract
An experimentally simple method for the direct determination of single-ion partition coefficients between water and a PVC membrane plasticized with o-NPOE is suggested. The method uses the traditional assumption of equal single-ion partition coefficients for some reference cation and anion, in this case [...] Read more.
An experimentally simple method for the direct determination of single-ion partition coefficients between water and a PVC membrane plasticized with o-NPOE is suggested. The method uses the traditional assumption of equal single-ion partition coefficients for some reference cation and anion, in this case tetraphenylphosphonium (TPP+) and tetraphenylborate (TPB). The method is based on an integrated approach, including direct study of some salts’ distribution between water and membrane phases, estimation of ion association constants, and measurements of unbiased selectivity coefficients for ions of interest, including the reference ones. The knowledge of distribution coefficients together with ion association constants allows for direct calculation of the multiple of the single-ion partition coefficients for the corresponding cation and anion, while the knowledge of unbiased selectivity coefficients together with ion association constants allows for immediate estimation of the single-ion partition coefficients for any ion under study, if the corresponding value for the reference ion is known. Both potentiometric and extraction studies are inherently equilibrium-based techniques, while traditionally accepted methods such as voltammetry and diffusion are kinetical. The inner coherent scale of single-ion partition coefficients between water and membrane phases was constructed. Full article
(This article belongs to the Collection Feature Papers in Membrane Surface and Interfaces)
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2 pages, 191 KiB  
Editorial
Special Issue on Drug–Membrane Interactions Volume II
by Marina Pinheiro and Sandra G. Silva
Membranes 2022, 12(10), 1018; https://doi.org/10.3390/membranes12101018 - 20 Oct 2022
Viewed by 872
Abstract
There is no life without cells and there are no cells without membranes [...] Full article
(This article belongs to the Special Issue Study on Drug-Membrane Interactions, Volume II)
18 pages, 7836 KiB  
Article
Polyphenylene Sulfide Ultrafine Viscous Fibrous Membrane Modified by ZIF-8 for Highly Effective Oil/Water Separation under High Salt or Alkaline Conditions
by Wenlei Liu, Lingli Yu, Xianfeng Cui, Ce Tan, Mengen Zhang, Di Wu, Zhenhuan Li and Maliang Zhang
Membranes 2022, 12(10), 1017; https://doi.org/10.3390/membranes12101017 - 20 Oct 2022
Cited by 4 | Viewed by 1867
Abstract
The oil/water separation in harsh environments has always been a challenging topic all over the world. In this study, the ZIF-8/PPS fiber membranes were fabricated via the combination of hot pressing and in situ growth. The distribution of ZIF-8 in the membranes was [...] Read more.
The oil/water separation in harsh environments has always been a challenging topic all over the world. In this study, the ZIF-8/PPS fiber membranes were fabricated via the combination of hot pressing and in situ growth. The distribution of ZIF-8 in the membranes was adjusted by changing the ZIF-8 in situ growth time, which could control the oil/water separation effect. Due to the hydrophilic nature of the ZIF-8/PPS fiber membranes, the water molecules in the oil-in-water emulsion could quickly penetrate into the fiber membrane under the drive of pressure, gravity, and capillary force, forming a water layer on the surface of the fiber membranes. The coupling of the water layer and the fiber structure prevented direct contact between the oil molecules and the fiber membrane, thereby realizing the separation of the emulsion. The results show that when the ZIF-8 in situ growth time was 10 h, the contact angle, the porosity, and the pure water flux of the ZIF-8/PPS fiber membranes were 72.5°, 52.3%, and 12,351 L/h·m2, respectively. More importantly, the separation efficiency of M10 was 97%, and the oil/water separation efficiency reached 95% after 14 cycles. This study provides a novel strategy for preparing MOFs/fiber materials for oil/water separation in harsh environments. Full article
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20 pages, 3177 KiB  
Article
Analysis of the Influence of Process Parameters on the Properties of Homogeneous and Heterogeneous Membranes for Gas Separation
by Daniel Polak and Maciej Szwast
Membranes 2022, 12(10), 1016; https://doi.org/10.3390/membranes12101016 - 19 Oct 2022
Cited by 3 | Viewed by 1650
Abstract
Heterogeneous membranes, otherwise known as Mixed Matrix Membranes (MMMs), which are used in gas separation processes, are the subject of growing interest. This is due to their potential to improve the process properties of membranes compared to those of homogeneous membranes, i.e., those [...] Read more.
Heterogeneous membranes, otherwise known as Mixed Matrix Membranes (MMMs), which are used in gas separation processes, are the subject of growing interest. This is due to their potential to improve the process properties of membranes compared to those of homogeneous membranes, i.e., those made of polymer only. Using such membranes in a process involves subjecting them to varying temperatures and pressures. This paper investigates the effects of temperature and feed pressure on the process properties of homogeneous and heterogeneous membranes. Membranes made of Pebax®2533 copolymer and containing additional fillers such as SiO2, ZIF−8, and POSS-Ph were investigated. Tests were performed over a temperature range of 25–55 °C and a pressure range of 2–8 bar for N2, CH4, and CO2 gases. It was found that temperature positively influences the increase in permeability, while pressure influences permeability depending on the gas used, which is related to the effect of pressure on the solubility of the gas in the membrane. Full article
(This article belongs to the Special Issue Preparation and Application of Advanced Functional Membranes)
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11 pages, 4505 KiB  
Article
Facile Fabrication of α-Alumina Hollow Fiber-Supported ZIF-8 Membrane Module and Impurity Effects on Propylene Separation Performance
by Taewhan Kim, Yeong Jae Kim, Chanjong Yu, Jongbum Kim and Kiwon Eum
Membranes 2022, 12(10), 1015; https://doi.org/10.3390/membranes12101015 - 19 Oct 2022
Cited by 2 | Viewed by 1539
Abstract
The separation of C3 olefin and paraffin, which is essential for the production of propylene, can be facilitated by the ZIF-8 membrane. However, the commercial application of the membrane has not yet been achieved because the fabrication process does not meet industrial [...] Read more.
The separation of C3 olefin and paraffin, which is essential for the production of propylene, can be facilitated by the ZIF-8 membrane. However, the commercial application of the membrane has not yet been achieved because the fabrication process does not meet industrial regulatory criteria. In this work, we provide a straightforward and cost-effective membrane fabrication technique that permits the rapid synthesis of ZIF-8 hollow fiber membranes. The scalability of the technology was confirmed by the incorporation of three ZIF-8 hollow fiber membranes into a single module using an introduced fiber mounting methodology. The molecular sieving characteristics of the ZIF-8 membrane module on a binary combination of C3 olefin and paraffin (C3H6/C3H8 selectivity of 110 and a C3H6 permeance of 13 GPU) were examined at atmospheric conditions. In addition, the high-pressure performance of these membranes was demonstrated at a 5 bar of equimolar binary feed pressure with a C3H6/C3H8 selectivity of 55 and a C3H6 permeance of 9 GPU due to propylene adsorption site saturation. To further accurately portray the separation performance of the membrane on an actual industrial feed, the effect of impurities (ethylene, ethane, butylene, i-butane, and n-butane), which can be found in C3 splitters, was investigated and a considerable decrement (~15%) in the propylene permeance upon an interaction with C4 hydrocarbons was confirmed. Finally, the long-term stability of the ZIF-8 membrane was confirmed by continuous operation for almost a month without any loss of its initial performance (C3H6/C3H8 separation factor of 110 and a C3H6 permeance of 13 GPU). From an industrial point of view, this straightforward technique could offer a number of merits such as a short synthesis time, minimal chemical requirements, and excellent reproductivity. Full article
(This article belongs to the Special Issue Membrane Process Systems and Techniques)
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13 pages, 2706 KiB  
Article
Inhibition of Zinc Dendrites Realized by a β-P(VDF-TrFE) Nanofiber Layer in Aqueous Zn-Ion Batteries
by Geumyong Park, Hyeonghun Park, WooJun Seol, Seokho Suh, Ji Young Jo, Santosh Kumar and Hyeong-Jin Kim
Membranes 2022, 12(10), 1014; https://doi.org/10.3390/membranes12101014 - 19 Oct 2022
Cited by 3 | Viewed by 2059
Abstract
Uncontrollable Zn dendrite formations and parasitic side reactions on Zn electrodes induce poor cycling stability and safety issues, preventing the large-scale commercialization of Zn-ion batteries. Herein, to achieve uniform Zn deposition and suppress side reactions, an electrospun ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) copolymer, [...] Read more.
Uncontrollable Zn dendrite formations and parasitic side reactions on Zn electrodes induce poor cycling stability and safety issues, preventing the large-scale commercialization of Zn-ion batteries. Herein, to achieve uniform Zn deposition and suppress side reactions, an electrospun ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) copolymer, a P(VDF-TrFE) nanofiber layer, is introduced as an artificial solid–electrolyte interface on a Cu substrate acting as a current collector. The aligned molecular structure of β-P(VDF-TrFE) can effectively suppress localized current density on the Cu surface, lead to uniform Zn deposition, and suppress side reactions by preventing direct contact between electrodes and aqueous electrolytes. The half-cell configuration formed by the newly fabricated electrode can achieve an average coulombic efficiency of 99.2% over 300 cycles without short-circuiting at a current density of 1 mA cm−2 and areal capacity of 1 mAh cm−2. Stable cycling stability is also maintained for 200 cycles at a current density of 0.5 A g−1 in a full-cell test using MnO2 as a cathode. Full article
(This article belongs to the Topic Membranes for Electrochemical Energy Conversion)
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14 pages, 2692 KiB  
Article
Evaluating the Feasibility of Employing Dynamic Membranes for the Direct Filtration of Municipal Wastewater
by Pau Sanchis-Perucho, Daniel Aguado, José Ferrer, Aurora Seco and Ángel Robles
Membranes 2022, 12(10), 1013; https://doi.org/10.3390/membranes12101013 - 19 Oct 2022
Cited by 1 | Viewed by 1039
Abstract
The aim of this study was to assess the feasibility of using dynamic membranes for direct filtration of municipal wastewater. The influence of different alternative supporting materials (one or two layers of flat open monofilament woven polyamide meshes with 1 or 5 µm [...] Read more.
The aim of this study was to assess the feasibility of using dynamic membranes for direct filtration of municipal wastewater. The influence of different alternative supporting materials (one or two layers of flat open monofilament woven polyamide meshes with 1 or 5 µm of pore size) was studied. A stable short-term self-forming DM was achieved (from some hours to 3 days) regardless of the supporting material used, producing relatively similar permeate qualities (total suspended solids, chemical oxygen demand, total nitrogen, total phosphorous and turbidity of 67–88 mg L−1, 155–186 mg L−1, 48.7–50.4 mg L−1, 4.7–4.9 mg L−1, and 167–174 NTU, respectively). A DM permeability loss rate of from 5.21 to 10.03 LMH bar−1 day−1 was obtained, which depended on the supporting material used. Unfortunately, the preliminary energy, carbon footprint, and economic evaluations performed showed that although DMs obtain higher pollutant captures than conventional treatments (primary settler), the benefits are not enough to justify their use for treating average municipal wastewater. However, this alternative scheme could be suitable for treating higher-loaded MWW with a higher fraction of organic matter in the non-settleable solids. Full article
(This article belongs to the Special Issue Water and Wastewater Treatment Technologies with Membrane Filtration)
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12 pages, 3082 KiB  
Article
Expression of Mutant Glycine Receptors in Xenopus Oocytes Using Canonical and Non-Canonical Amino Acids Reveals Distinct Roles of Conserved Proline Residues
by Sarah C. R. Lummis and Dennis A. Dougherty
Membranes 2022, 12(10), 1012; https://doi.org/10.3390/membranes12101012 - 19 Oct 2022
Cited by 2 | Viewed by 1108
Abstract
Pentameric ligand-gated ion channels (pLGIC) play important roles in fast neuronal signal transmission. Functional receptors are pentamers, with each subunit having an extracellular domain (ECD), a transmembrane domain (TMD) and an intracellular domain. The binding of the agonist to the ECD induces a [...] Read more.
Pentameric ligand-gated ion channels (pLGIC) play important roles in fast neuronal signal transmission. Functional receptors are pentamers, with each subunit having an extracellular domain (ECD), a transmembrane domain (TMD) and an intracellular domain. The binding of the agonist to the ECD induces a structural change that is transduced to the TMD to open the channel. Molecular details of this process are emerging, but a comprehensive understanding is still lacking. Proline (Pro) is one amino acid that has attracted much interest; its unusual features generate bends in loops and kinks and bulges in helices, which can be essential for function in some pLGICs. Here, we explore the roles of four conserved Pros in the glycine receptor (GlyR), creating substitutions with canonical and noncanonical amino acids, characterizing them using two electrode voltage clamp electrophysiology in Xenopus oocytes, and interpreting changes in receptor parameters using structural data from the open and closed states of the receptor. The data reveal that for efficient function, the Pro in the α1β1 loop is needed to create a turn and to be the correct size and shape to interact with nearby residues; the peptide bond of the Pro in the Cys-loop requires the cis conformation; and the Pros in loop A and M1 allow efficient function because of their reduced hydrogen bonding capacity. These data are broadly consistent with data from other pLGICs, and therefore likely represent the important features of these Pros in all members of the family. Full article
(This article belongs to the Special Issue The Xenopus Oocyte: A Tool for Membrane Biology)
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13 pages, 2044 KiB  
Article
High Flux Nanofiltration Membranes with Double-Walled Carbon Nanotube (DWCNT) as the Interlayer
by Zhen Wang, Xiaojuan Wang, Tao Zheng, Bing Mo, Huacheng Xu, Yijun Huang, Jian Wang, Congjie Gao and Xueli Gao
Membranes 2022, 12(10), 1011; https://doi.org/10.3390/membranes12101011 - 19 Oct 2022
Cited by 1 | Viewed by 1448
Abstract
Nanofiltration (NF) membranes with a high permeability and rejection are of great interest in desalination, separation and purification. However, how to improve the permeation and separation performance still poses a great challenge in the preparation of NF membranes. Herein, the novel composite NF [...] Read more.
Nanofiltration (NF) membranes with a high permeability and rejection are of great interest in desalination, separation and purification. However, how to improve the permeation and separation performance still poses a great challenge in the preparation of NF membranes. Herein, the novel composite NF membrane was prepared through the interfacial polymerization of M-phenylenediamine (MPD) and trimesoyl chloride (TMC) on a double-walled carbon nanotube (DWCNT) interlayer supported by PES substrate. The DWCNT interlayer had a great impact on the polyamide layer formation. With the increase of the DWCNT dosage, the XPS results revealed an increase in the number of carboxyl groups, which decreased the crosslinking degree of the polyamide layer. Additionally, the AFM results showed that the surface roughness and specific surface area increased gradually. The water flux of the prepared membrane increased from 25.4 L/(m2·h) and 26.6 L/(m2·h) to 109 L/(m2·h) and 104.3 L/(m2·h) with 2000 ppm Na2SO4 and NaCl solution, respectively, under 0.5 MPa. Meanwhile, the rejection of Na2SO4 and NaCl decreased from 99.88% and 99.38% to 96.48% and 60.47%. The proposed method provides a novel insight into the rational design of the multifunctional interlayer, which shows great potential in the preparation of high-performance membranes. Full article
(This article belongs to the Special Issue Environmentally Conscious Development of Membrane Separations)
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12 pages, 2314 KiB  
Article
Study on Treatment of Tiny Pollution Water with PAC-HUM System in Kuitun River
by Liang Pei and Jia Duo
Membranes 2022, 12(10), 1010; https://doi.org/10.3390/membranes12101010 - 18 Oct 2022
Cited by 2 | Viewed by 1035
Abstract
Kuitun city, Xinjiang is dry and short of water, so it is urgent to treat and utilize all kinds of unconventional water. In view of this problem, we conducted a study on the treatment of tiny pollution water in Kuitun River. We investigated [...] Read more.
Kuitun city, Xinjiang is dry and short of water, so it is urgent to treat and utilize all kinds of unconventional water. In view of this problem, we conducted a study on the treatment of tiny pollution water in Kuitun River. We investigated the effect of dosage of powder activated carbon (PAC) on hollow-fiber ultrafiltration membrane (HUM) performance. The results show that the stable operation time of hollow fiber ultrafiltration membranes lengthened and the rate of reduction of the flux was reduced when the PAC dosage was increased. The addition of PAC had no obvious effect on the resistance of membrane filtration. We conducted experiments to evaluate the effect of ultrafiltration of tiny pollution water in combination with PAC. When the parameters of operation and PAC dosage were appropriately regulated, the removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH3-N) and ferric ions (Fe) reached 62%, 32% and 90%, respectively. When the PAC dosage was 200 mg/L, 100 mg/L and 150 mg/L, the highest removal rates were achieved under normal temperature and pressure. The effluent COD was less than 5.0 mg/L, NH3-N was less than 1.5 mg/L and Fe was less than 0.5 mg/L, achieving better results than the quality standard of surface water (GB3838-2002). The treated water can be discharged into the river or recirculated to utilities. The fouled membrane was cleaned by water rinsing, water/acid rinsing and water/alkali rinsing, with recovery ratios of 44%, 81% and 88%, respectively. The results of this study can serve as a foundation for the efficient utilization of water resources and the development of new water treatment technologies in Xinjiang. Full article
(This article belongs to the Special Issue Membrane Distillation for Wastewater Treatment)
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13 pages, 2072 KiB  
Article
The Rigid Adsorbent Lattice Fluid Model: Thermodynamic Consistency and Relationship to the Real Adsorbed Solution Theory
by Stefano Brandani
Membranes 2022, 12(10), 1009; https://doi.org/10.3390/membranes12101009 - 18 Oct 2022
Cited by 1 | Viewed by 1007
Abstract
The Rigid Adsorbent Lattice Fluid model has been shown to comply with all the requirements for thermodynamic consistency in the case of an adsorbent that does not undergo structural changes. This is achieved by introducing a correction to the reduced density function that [...] Read more.
The Rigid Adsorbent Lattice Fluid model has been shown to comply with all the requirements for thermodynamic consistency in the case of an adsorbent that does not undergo structural changes. This is achieved by introducing a correction to the reduced density function that multiplies the combinatorial term. A procedure to calculate the predicted adsorbed mixture activity coefficients has been presented that allows the production of excess Gibbs energy plots at a constant reduced grand potential. The predicted nonideality is structurally consistent with the Non-Ideal Adsorbed Solution Theory of Myers in terms of both its dependence on concentration and reduced grand potential. The ability to generate excess Gibbs energy values allows linking the new Rigid Adsorbent Lattice Fluid model to the traditional Real Adsorbed Solution Theory providing an alternative approach to predicting multicomponent adsorption based solely on pure component data. Full article
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17 pages, 2184 KiB  
Article
Magnesium-Doped Sr2(Fe,Mo)O6−δ Double Perovskites with Excellent Redox Stability as Stable Electrode Materials for Symmetrical Solid Oxide Fuel Cells
by Kun Zheng, Jakub Lach, Hailei Zhao, Xiubing Huang and Kezhen Qi
Membranes 2022, 12(10), 1006; https://doi.org/10.3390/membranes12101006 - 18 Oct 2022
Cited by 4 | Viewed by 1834
Abstract
In this work, magnesium-doped Sr2Fe1.2Mg0.2Mo0.6O6−δ and Sr2Fe0.9Mg0.4Mo0.7O6−δ double perovskites with excellent redox stability have been successfully obtained. The physicochemical properties including: crystal structure properties, redox [...] Read more.
In this work, magnesium-doped Sr2Fe1.2Mg0.2Mo0.6O6−δ and Sr2Fe0.9Mg0.4Mo0.7O6−δ double perovskites with excellent redox stability have been successfully obtained. The physicochemical properties including: crystal structure properties, redox stability, thermal expansion properties in oxidizing and reducing conditions, oxygen content as a function of temperature and transport properties, as well as the chemical compatibility with typical electrolytes have been systematically investigated. The in situ oxidation of reduced samples using high-temperature XRD studies shows the crystal structure of materials stable at up to a high-temperature range. The in situ reduction and oxidation of sinters with dilatometer measurements prove the excellent redox stability of materials, with the thermal expansion coefficients measured comparable with electrolytes. The oxygen nonstoichiometry δ of compounds was determined and recorded in air and argon up to 900 °C. Sr2Fe1.2Mg0.2Mo0.6O6−δ oxide presents satisfactory values of electrical conductivity in air (56.2 S·cm−1 at 600 °C) and reducing conditions (10.3 S·cm−1 at 800 °C), relatively high coefficients D and k, and good ionic conductivity (cal. 0.005 S·cm−1 at 800 °C). The stability studies show that both compounds are compatible with Ce0.8Gd0.2O1.9 but react with the La0.8Sr0.2Ga0.8Mg0.2O3−d electrolyte. Therefore, the magnesium-doped double perovskites with excellent redox stability can be potentially qualified as electrode materials for symmetrical SOFCs and are of great interest for further investigations. Full article
(This article belongs to the Special Issue Membranes for Energy Conversion (Volume II))
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23 pages, 1489 KiB  
Article
Influence of the Processing Parameters on the Aroma Profile and Chemical Composition of Conventional and Ecological Cabernet Sauvignon Red Wines during Concentration by Reverse Osmosis
by Ivana Ivić, Mirela Kopjar, Jasmina Obhođaš, Andrija Vinković, Jurislav Babić, Josip Mesić and Anita Pichler
Membranes 2022, 12(10), 1008; https://doi.org/10.3390/membranes12101008 - 17 Oct 2022
Viewed by 1325
Abstract
Wine aroma represents one of the most important quality parameters and it is influenced by various factors, such as climate conditions, viticulture and vinification techniques, storage conditions, etc. Wines produced from conventionally and ecologically grown grapes of the same variety have different chemical [...] Read more.
Wine aroma represents one of the most important quality parameters and it is influenced by various factors, such as climate conditions, viticulture and vinification techniques, storage conditions, etc. Wines produced from conventionally and ecologically grown grapes of the same variety have different chemical compositions and aroma profiles. The composition of wine can also be influenced by the additional treatment of wine, such as the concentration of wine by reverse osmosis (RO). The aim of this study was to investigate the influence of four different pressures (2.5, 3.5, 4.5 and 5.5 MPa) and two temperature regimes (with and without cooling) on the aroma profile and chemical composition of conventional and ecological Cabernet Sauvignon red wine during concentration by reverse osmosis. The results showed that different processing parameters influenced the permeate flux, the retentate temperature and the compounds retention. Higher working pressures (4.5 and 5.5 MPa) and the regime, with cooling, resulted in a higher retention of the total aroma compounds than the opposite processing parameters. The retention of individual compounds depended also on their chemical properties and their interactions with the membrane surface. The reverse osmosis membranes proved to be permeable for ethanol, acetic acid or undesirable 4-ethylphenol and 4-ethylguaiacol that made them applicable for their correction or removal. Full article
(This article belongs to the Special Issue Novel Membranes for Molecular Separations)
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16 pages, 1410 KiB  
Article
PEBA/PDMS Composite Multilayer Hollow Fiber Membranes for the Selective Separation of Butanol by Pervaporation
by Carla Arregoitia-Sarabia, Daniel González-Revuelta, Marcos Fallanza, Alfredo Ortiz and Daniel Gorri
Membranes 2022, 12(10), 1007; https://doi.org/10.3390/membranes12101007 - 17 Oct 2022
Cited by 5 | Viewed by 1992
Abstract
The growing interest in the production of biofuels has motivated numerous studies on separation techniques that allow the separation/concentration of organics produced by fermentation, improving productivity and performance. In this work, the preparation and characterization of new butanol-selective membranes was reported. The prepared [...] Read more.
The growing interest in the production of biofuels has motivated numerous studies on separation techniques that allow the separation/concentration of organics produced by fermentation, improving productivity and performance. In this work, the preparation and characterization of new butanol-selective membranes was reported. The prepared membranes had a hollow fiber configuration and consisted of two dense selective layers: a first layer of PEBA and a second (outer) layer of PDMS. The membranes were tested to evaluate their separation performance in the selective removal of organics from a synthetic ABE solution. Membranes with various thicknesses were prepared in order to evaluate the effect of the PDMS protective layer on permeant fluxes and membrane selectivity. The mass transport phenomena in the pervaporation process were characterized using a resistances-in-series model. The experimental results showed that PEBA as the material of the dense separating layer is the most favorable in terms of selectivity towards butanol with respect to the other components of the feed stream. The addition of a protective layer of PDMS allows the sealing of possible pinholes; however, its thickness should be kept as small as possible since permeation fluxes decrease with increasing thickness of PDMS and this material also has greater selectivity towards acetone compared to other feed components. Full article
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13 pages, 2827 KiB  
Article
Investigation of Phosphatidylserine-Transporting Activity of Human TMEM16C Isoforms
by Hanggu Kim, Eunyoung Kim and Byoung-Cheol Lee
Membranes 2022, 12(10), 1005; https://doi.org/10.3390/membranes12101005 - 17 Oct 2022
Cited by 4 | Viewed by 1481
Abstract
Lipid scrambling is a rapid process that dissipates the asymmetrical distribution of phospholipids in the plasma membrane. It is involved in various physiological functions such as blood coagulation and apoptosis. Many TMEM16 members are recognized as Ca2+-activated phospholipid scramblases, which transport [...] Read more.
Lipid scrambling is a rapid process that dissipates the asymmetrical distribution of phospholipids in the plasma membrane. It is involved in various physiological functions such as blood coagulation and apoptosis. Many TMEM16 members are recognized as Ca2+-activated phospholipid scramblases, which transport phospholipids between the two leaflets of the plasma membrane nonspecifically and bidirectionally; among these, TMEM16C is abundant in the brain, especially in neuronal cells. We investigated the scrambling activity of three human TMEM16C isoforms with different N-terminus lengths. After optimizing conditions to minimize endogenous scrambling activity, an annexin V-based imaging assay was used to detect phosphatidylserine (PS) scrambling in 293T cells. Unlike previous results, our data showed that human TMEM16C isoform 1 and isoform 3 exposed PS to the cell surface. A surface biotinylation assay showed that the surface expression of isoform 2, which did not show scrambling activity, was ~5 times lower than the other isoforms. In contrast to other TMEM16 proteins, flux assays and electrophysiology recording showed TMEM16C does not possess ion-transporting activity. We conclude that the N-terminus of TMEM16C determines whether TMEM16C can translocate to the plasma membrane and facilitate scrambling activity; membrane-localized TMEM16C isoforms 1 and 3 transport PS to the outer leaflet. Full article
(This article belongs to the Special Issue Membrane Proteins: Function, Structure, and Dynamic)
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18 pages, 8535 KiB  
Article
Effects of the Water Matrix on the Degradation of Micropollutants by a Photocatalytic Ceramic Membrane
by Shuyana A. Heredia Deba, Bas A. Wols, Doekle R. Yntema and Rob G. H. Lammertink
Membranes 2022, 12(10), 1004; https://doi.org/10.3390/membranes12101004 - 16 Oct 2022
Cited by 4 | Viewed by 1889
Abstract
The consumption of pharmaceuticals has increased the presence of micropollutants (MPs) in the environment. The removal and degradation of pharmaceutical mixtures in different water matrices are thus of significant importance. The photocatalytic degradation of four micropollutants—diclofenac (DCF), iopamidol (INN), methylene blue (MB), and [...] Read more.
The consumption of pharmaceuticals has increased the presence of micropollutants (MPs) in the environment. The removal and degradation of pharmaceutical mixtures in different water matrices are thus of significant importance. The photocatalytic degradation of four micropollutants—diclofenac (DCF), iopamidol (INN), methylene blue (MB), and metoprolol (MTP)—have been analyzed in this study by using a photocatalytic ceramic membrane. We experimentally analyzed the degradation rate by using several water matrices by changing the feed composition of micropollutants in the mixture (from mg· L1 to μg·L1), adding different concentrations of inorganic compounds (NaHCO3 and NaCl), and by using tap water. A maximum degradation of 97% for DCF and MTP, and 85% for INN was observed in a micropollutants (MPs) mixture in tap water at environmentally relevant feed concentrations [1–6 μg·L1]o; and 86% for MB in an MPs mixture [1–3 mg·L1]o with 100 mg·L1 of NaCl. This work provides further insights into the applicability of photocatalytic membranes and illustrates the importance of the water matrix to the photocatalytic degradation of micropollutants. Full article
(This article belongs to the Special Issue Catalysis in Membrane Reactors 2022)
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12 pages, 1852 KiB  
Article
Identifying Characteristic Frequencies in the Electrochemical Impedance of Ion-Exchange Membrane Systems
by Antonio Angel Moya
Membranes 2022, 12(10), 1003; https://doi.org/10.3390/membranes12101003 - 16 Oct 2022
Cited by 2 | Viewed by 1268
Abstract
In this study, the characteristic frequencies of the electrochemical impedance of ion-exchange membrane systems constituted by the membrane and two diffusion boundary layers adjacent to the membrane were investigated. Approximations of the impedance of the Randles equivalent electric circuit in multiple frequency ranges [...] Read more.
In this study, the characteristic frequencies of the electrochemical impedance of ion-exchange membrane systems constituted by the membrane and two diffusion boundary layers adjacent to the membrane were investigated. Approximations of the impedance of the Randles equivalent electric circuit in multiple frequency ranges were considered, and the characteristic frequencies of the zeros and poles of orders ½ and 1 were derived. The characteristic geometric frequencies, those associated with the interfacial charge transfer and the diffusive transport processes, as well as those associated with the transitions between processes, were identified by means of analytical expressions. Full article
(This article belongs to the Special Issue Membranes for Energy Conversion (Volume II))
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16 pages, 8115 KiB  
Article
Application and Visualization of Fluorescent-Tagged Antiscalants in Electrodialysis Processing of Aqueous Solutions Prone to Gypsum Scale Deposition
by Violetta Gil, Maxim Oshchepkov, Anastasia Ryabova, Maria Trukhina, Mikhail Porozhnyy, Sergey Tkachenko, Natalia Pismenskaya and Konstantin Popov
Membranes 2022, 12(10), 1002; https://doi.org/10.3390/membranes12101002 - 16 Oct 2022
Cited by 3 | Viewed by 1381
Abstract
Membrane scaling is a serious problem in electrodialysis. A widely used technique for controlling scale deposition in water treatment technologies is the application of antiscalants (AS). The present study reports on gypsum scale inhibition in electrodialysis cell by the two novel ASs: fluorescent-tagged [...] Read more.
Membrane scaling is a serious problem in electrodialysis. A widely used technique for controlling scale deposition in water treatment technologies is the application of antiscalants (AS). The present study reports on gypsum scale inhibition in electrodialysis cell by the two novel ASs: fluorescent-tagged bisphosphonate 1-hydroxy-7-(6-methoxy-1,3-dioxo-1Hbenzo[de]isoquinolin-2(3H)-yl)heptane-1,1-diyl-bis(phosphonic acid), HEDP-F and fluorescein-tagged polyacrylate, PAA-F2 (molecular mass 4000 Da) monitored by chronopotentiometry and fluorescent microscopy. It was found that cation-exchange membrane MK-40 scaling is sufficiently reduced by both ASs, used in 10−6 mol·dm−3 concentrations. PAA-F2 at these concentrations was found to be more efficient than HEDP-F. At the same time, PAA-F2 reveals gypsum crystals’ habit modification, while HEDP-F does not noticeably affect the crystal form of the deposit. The strong auto-luminescence of MK-40 hampers visualization of both PAA-F2 and HEDP-F on the membrane surface. Nevertheless, PAA-F2 is proved to localize partly on the surface of gypsum crystals as a molecular adsorption layer, and to change their crystal habit. Crystal surface coverage by PAA-F2 appears to be nonuniform. Alternatively, HEDP-F localizes on the surface of a deposit tentatively in the form of [Ca-HEDP-F]. The proposed mechanisms of action are formulated and discussed. The application of antiscalants in electrodialysis for membrane scaling mitigation is demonstrated to be very promising. Full article
(This article belongs to the Special Issue Membranes in Electrochemistry Applications 2.0)
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7 pages, 4606 KiB  
Communication
Gravure Printing of Graphite-Based Anodes for Lithium-Ion Printed Batteries
by Maria Montanino, Anna De Girolamo Del Mauro, Claudia Paoletti and Giuliano Sico
Membranes 2022, 12(10), 999; https://doi.org/10.3390/membranes12100999 - 14 Oct 2022
Cited by 2 | Viewed by 1329
Abstract
Aimed at the growing interest in printed batteries, widely used industrial gravure printing was recently proven to be able to produce high-quality electrodes for lithium-ion batteries (LiBs), demonstrating its utility in the study of new functional materials. Here, for the first time, gravure [...] Read more.
Aimed at the growing interest in printed batteries, widely used industrial gravure printing was recently proven to be able to produce high-quality electrodes for lithium-ion batteries (LiBs), demonstrating its utility in the study of new functional materials. Here, for the first time, gravure printing was investigated for the mass production of well-known low-cost graphite-based anodes for LiBs. Graphite was also chosen as a case study to explore the influence of process parameters on the layer microstructure and the performance of the printed anodes. In particular, upon decreasing the size of the active material nanoparticles through ball-milling, an enhancement in anode performance was observed, which is related to an improvement in the material distribution in the printed layer, even in the case of increasing mass loading through a multilayer approach. A further improvement in performance, close to the theoretical capacity, was possible by changing the ink parameters, obtaining a denser microstructure of the printed anode. Such good results further demonstrate the possibility of using gravure printing for the mass production of electrodes for printed batteries and, in general, components in the field of energy. Full article
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20 pages, 2649 KiB  
Article
Thermally Rearranged Mixed Matrix Membranes from Copoly(o-hydroxyamide)s and Copoly(o-hydroxyamide-amide)s with a Porous Polymer Network as a Filler—A Comparison of Their Gas Separation Performances
by Cenit Soto, Bibiana Comesaña-Gandara, Ángel Marcos, Purificación Cuadrado, Laura Palacio, Ángel E. Lozano, Cristina Álvarez, Pedro Prádanos and Antonio Hernandez
Membranes 2022, 12(10), 998; https://doi.org/10.3390/membranes12100998 - 14 Oct 2022
Cited by 3 | Viewed by 1695
Abstract
Copoly(o-hydroxyamide)s (HPA) and copoly(o-hydroxyamide-amide)s (PAA) have been synthesized to be used as continuous phases in mixed matrix membranes (MMMs). These polymeric matrices were blended with different loads (15 and 30 wt.%) of a relatively highly microporous porous polymer network (PPN). SEM images of [...] Read more.
Copoly(o-hydroxyamide)s (HPA) and copoly(o-hydroxyamide-amide)s (PAA) have been synthesized to be used as continuous phases in mixed matrix membranes (MMMs). These polymeric matrices were blended with different loads (15 and 30 wt.%) of a relatively highly microporous porous polymer network (PPN). SEM images of the manufactured MMMs exhibited good compatibility between the two phases for all the membranes studied, and their mechanical properties have been shown to be good enough even after thermal treatment. The WAX results show that the addition of PPN as a filler up to 30% does not substantially change the intersegmental distance and the polymer packing. It seems that, for all the membranes studied, the free volume that determines gas transport is in the high end of the possible range. This means that gas flow occurs mainly between the microvoids in the polymer matrix around the filler. In general, both HPA- and PAA-based MMMs exhibited a notable improvement in gas permeability, due to the presence of PPN, for all gases tested, with an almost constant selectivity. In summary, although the thermal stability of the PAA is limited by the thermal stability of the polyamide side chain, their mechanical properties were better. The permeability was higher for the PAA membranes before their thermal rearrangement, and these values increased after the addition of moderate amounts of PPN. Full article
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16 pages, 2901 KiB  
Article
Possible Role of Bent Structure of Methylated Lithocholic Acid on Artificial and Plasma Membranes
by Tomoyuki Iwasaki, Nobuyuki Endo, Yuta Nakayama, Toshiyuki Kamei, Toshinori Shimanouchi, Hidemi Nakamura and Keita Hayashi
Membranes 2022, 12(10), 997; https://doi.org/10.3390/membranes12100997 - 14 Oct 2022
Viewed by 1328
Abstract
Bile acids form micelles that are essential for the absorption of dietary lipids. However, excessive bile acid micelles can disrupt the plasma membrane by removing phospholipids, resulting in cell death. We hypothesized that the bent geometrical structure of the steroid scaffold of bile [...] Read more.
Bile acids form micelles that are essential for the absorption of dietary lipids. However, excessive bile acid micelles can disrupt the plasma membrane by removing phospholipids, resulting in cell death. We hypothesized that the bent geometrical structure of the steroid scaffold of bile acids decreases the lipid order (similar to unsaturated phospholipids with cis double bonds), disrupting the plasma membrane. Here, lithocholic acid (LCA), a bile acid, was methylated to prevent micellization. Methylated lithocholic acid (Me-LCA) was mixed with a thin phase-separated lipid bilayer comprising 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and cholesterol (Chol). Me-LCA was not localized in the DPPC-rich rigid phase but localized in the DOPC-rich fluid phase, and excess Me-LCA did not affect the phase separation. Me-LCA is distributed in the plasma and organelle membranes. However, Me-LCA with bent structure did not affect the membrane properties, membrane fluidity, and hydrophobicity of liposomes composed of DOPC, DPPC, and Chol and also did not affect the proliferation of cells. Full article
(This article belongs to the Section Biological Membrane Functions)
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13 pages, 4223 KiB  
Article
Effect of Graphene Oxide on the Properties of Polymer Inclusion Membranes for Gold Extraction from Acidic Solution
by Siti Madiha Husna, Abdul Hafidz Yusoff, Mythili Mohan, Nur Aina Azmi, Teo Pao Ter, Noor Fazliani Shoparwe and Ahmad Ziad Sulaiman
Membranes 2022, 12(10), 996; https://doi.org/10.3390/membranes12100996 - 14 Oct 2022
Cited by 1 | Viewed by 1546
Abstract
The cyanidation leaching method is hazardous to the environment, but it is widely applied in the gold mining process because it is effective for gold extraction. This study fabricates polymer inclusion membranes (PIMs), which have environment-friendly properties, with graphene oxide (GO) as an [...] Read more.
The cyanidation leaching method is hazardous to the environment, but it is widely applied in the gold mining process because it is effective for gold extraction. This study fabricates polymer inclusion membranes (PIMs), which have environment-friendly properties, with graphene oxide (GO) as an alternative to the cyanidation leaching method for gold extraction. Poly(vinylidenefluoride-co-hexa-fluoropropylene)-based PIMs with different GO concentrations in five membranes (i.e., M1 (0 wt.%), M2 (0.5 wt.%), M3 (1.0 wt.%), M4 (1.5 wt.%), and M5 (2.0 wt.%)) are studied for their potential to extract gold from a hydrochloric acid solution. The membranes are prepared using di-(2-ethylhexyl) phosphoric acid as the extractant and dioctyl phthalate as the plasticizer. Scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, ion exchange capacity, and water uptake are used to characterize the physical and chemical properties of the fabricated PIMs. The results show that the optimized membrane for gold extraction is M4 (1.5 wt.% GO), which yields a better performance on thermal stability, ion exchange capacity (IEC), and water uptake. M4 (1.5 wt.% GO) also exhibits a smooth and dense structure, with the maximum extraction efficiency obtained at 84.71% of extracted gold. In conclusion, PIMs can be used as an alternative for extracting gold with a better performance by the presence of 1.5 wt.% GO in membrane composition. Full article
(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))
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16 pages, 3957 KiB  
Article
Microstructure Reconstruction and Multiphysics Dynamic Distribution Simulation of the Catalyst Layer in PEMFC
by Zhigang Zhan, Hao Song, Xiaoxiang Yang, Panxing Jiang, Rui Chen, Hesam Bazargan Harandi, Heng Zhang and Mu Pan
Membranes 2022, 12(10), 1001; https://doi.org/10.3390/membranes12101001 - 14 Oct 2022
Cited by 3 | Viewed by 1639
Abstract
Due to the complexity of both material composition and the structure of the catalyst layer (CL) used in the proton-exchange membrane fuel cell (PEMFC), conjugated heat and mass transfer as well as electrochemical processes simultaneously occur through the CL. In this study, a [...] Read more.
Due to the complexity of both material composition and the structure of the catalyst layer (CL) used in the proton-exchange membrane fuel cell (PEMFC), conjugated heat and mass transfer as well as electrochemical processes simultaneously occur through the CL. In this study, a microstructure model of CL was first reconstructed using images acquired by Nano-computed tomography (Nano-CT) of a real sample of CL. Then, the multiphysics dynamic distribution (MPDD) simulation, which is inherently a multiscale approach made of a combination of pore-scale and homogeneous models, was conducted on the reconstructed microstructure model to compute the corresponded heat and mass transport, electrochemical reactions, and water phase-change processes. Considering a computational domain with the size of 4 um and cube shape, this model consisting of mass and heat transport as well as electrochemical reactions reached a stable solution within 3 s as the convergence time. In the presence of sufficient oxygen, proton conduction was identified as the dominant factor determining the strength of the electrochemical reaction. Additionally, it was concluded that current density, temperature, and the distribution of water all exhibit similar distribution trends, which decrease from the interface between CL and the proton-exchange membrane to the interface between CL and the gas-diffusion layer. The present study not only provides an in-depth understanding of the mass and heat transport and electrochemical reaction in the CL microstructure, but it also guides the optimal design and fabrication of CL components and structures, such as improving the local structure to reduce the number of dead pores and large agglomerates, etc. Full article
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