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Membranes, Volume 10, Issue 11 (November 2020) – 65 articles

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Open AccessReview
Recent Progress in the Engineering of Polymeric Membranes for CO2 Capture from Flue Gas
Membranes 2020, 10(11), 365; https://doi.org/10.3390/membranes10110365 - 23 Nov 2020
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Abstract
CO2 capture from coal- or natural gas-derived flue gas has been widely considered as the next opportunity for the large-scale deployment of gas separation membranes. Despite the tremendous progress made in the synthesis of polymeric membranes with high CO2/N2 [...] Read more.
CO2 capture from coal- or natural gas-derived flue gas has been widely considered as the next opportunity for the large-scale deployment of gas separation membranes. Despite the tremendous progress made in the synthesis of polymeric membranes with high CO2/N2 separation performance, only a few membrane technologies were advanced to the bench-scale study or above from a highly idealized laboratory setting. Therefore, the recent progress in polymeric membranes is reviewed in the perspectives of capture system energetics, process synthesis, membrane scale-up, modular fabrication, and field tests. These engineering considerations can provide a holistic approach to better guide membrane research and accelerate the commercialization of gas separation membranes for post-combustion carbon capture. Full article
(This article belongs to the Special Issue Advanced Membranes for Carbon Capture)
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Open AccessArticle
Influence of Cholesterol on the Orientation of the Farnesylated GTP-Bound KRas-4B Binding with Anionic Model Membranes
Membranes 2020, 10(11), 364; https://doi.org/10.3390/membranes10110364 - 22 Nov 2020
Viewed by 228
Abstract
The Ras family of proteins is tethered to the inner leaflet of the cell membranes which plays an essential role in signal transduction pathways that promote cellular proliferation, survival, growth, and differentiation. KRas-4B, the most mutated Ras isoform in different cancers, has been [...] Read more.
The Ras family of proteins is tethered to the inner leaflet of the cell membranes which plays an essential role in signal transduction pathways that promote cellular proliferation, survival, growth, and differentiation. KRas-4B, the most mutated Ras isoform in different cancers, has been under extensive study for more than two decades. Here we have focused our interest on the influence of cholesterol on the orientations that KRas-4B adopts with respect to the plane of the anionic model membranes. How cholesterol in the bilayer might modulate preferences for specific orientation states is far from clear. Herein, after analyzing data from in total 4000 ns-long molecular dynamics (MD) simulations for four KRas-4B systems, properties such as the area per lipid and thickness of the membrane as well as selected radial distribution functions, penetration of different moieties of KRas-4B, and internal conformational fluctuations of flexible moieties in KRas-4B have been calculated. It has been shown that high cholesterol content in the plasma membrane (PM) favors one orientation state (OS1), exposing the effector-binding loop for signal transduction in the cell from the atomic level. We confirm that high cholesterol in the PM helps KRas-4B mutant stay in its constitutively active state, which suggests that high cholesterol intake can increase mortality and may promote cancer progression for cancer patients. We propose that during the treatment of KRas-4B-related cancers, reducing the cholesterol level in the PM and sustaining cancer progression by controlling the plasma cholesterol intake might be taken into account in anti-cancer therapies. Full article
(This article belongs to the Special Issue Modeling and Simulation of Lipid Membranes)
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Open AccessArticle
Investigation of Ion Transport Parameters and Electrochemical Performance of Plasticized Biocompatible Chitosan-Based Proton Conducting Polymer Composite Electrolytes
Membranes 2020, 10(11), 363; https://doi.org/10.3390/membranes10110363 - 21 Nov 2020
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Abstract
In this study, biopolymer composite electrolytes based on chitosan:ammonium iodide:Zn(II)-complex plasticized with glycerol were successfully prepared using the solution casting technique. Various electrical and electrochemical parameters of the biopolymer composite electrolytes’ films were evaluated prior to device application. The highest conducting plasticized membrane [...] Read more.
In this study, biopolymer composite electrolytes based on chitosan:ammonium iodide:Zn(II)-complex plasticized with glycerol were successfully prepared using the solution casting technique. Various electrical and electrochemical parameters of the biopolymer composite electrolytes’ films were evaluated prior to device application. The highest conducting plasticized membrane was found to have a conductivity of 1.17 × 10−4 S/cm. It is shown that the number density, mobility, and diffusion coefficient of cations and anions fractions are increased with the glycerol amount. Field emission scanning electron microscope and Fourier transform infrared spectroscopy techniques are used to study the morphology and structure of the films. The non-Debye type of relaxation process was confirmed from the peak appearance of the dielectric relaxation study. The obtained transference number of ions (cations and anions) and electrons for the highest conducting sample were identified to be 0.98 and 0.02, respectively. Linear sweep voltammetry shows that the electrochemical stability of the highest conducting plasticized system is 1.37 V. The cyclic voltammetry response displayed no redox reaction peaks over its entire potential range. It was discovered that the addition of Zn(II)-complex and glycerol plasticizer improved the electric double-layer capacitor device performances. Numerous crucial parameters of the electric double-layer capacitor device were obtained from the charge-discharge profile. The prepared electric double-layer capacitor device showed that the initial values of specific capacitance, equivalence series resistance, energy density, and power density are 36 F/g, 177 Ω, 4.1 Wh/kg, and 480 W/kg, respectively. Full article
(This article belongs to the Special Issue Modelling and Experiment of Anion-Exchange Membranes)
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Open AccessArticle
Newly Developed Pediatric Membrane Oxygenator that Suppresses Excessive Pressure Drop in Cardiopulmonary Bypass and Extracorporeal Membrane Oxygenation (ECMO)
Membranes 2020, 10(11), 362; https://doi.org/10.3390/membranes10110362 - 21 Nov 2020
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Abstract
This article developes a pediatric membrane oxygenator that is compact, high performance, and highly safe. This novel experimental approach, which imaging the inside of a membrane oxygenator during fluid perfusion using high-power X-ray CT, identifies air and blood retention in the local part [...] Read more.
This article developes a pediatric membrane oxygenator that is compact, high performance, and highly safe. This novel experimental approach, which imaging the inside of a membrane oxygenator during fluid perfusion using high-power X-ray CT, identifies air and blood retention in the local part of a membrane oxygenator. The cause of excessive pressure drop in a membrane oxygenator, which has been the most serious dysfunction in cardiovascular surgery and extracorporeal membrane oxygenation (ECMO), is the local retention of blood and air inside the oxygenator. Our designed blood flow channel for a membrane oxygenator has a circular channel and minimizes the boundary between laminated parts. The pressure drop in the blood flow channel is reduced, and the maximum gas transfer rates are increased by using this pediatric membrane oxygenator, as compared with the conventional oxygenator. Furthermore, it would be possible to reduce the incidents, which have occurred clinically, due to excessive pressure drop in the blood flow channel of the membrane oxygenator. The membrane oxygenator is said to be the “last stronghold” for patients with COVID-19 receiving ECMO treatment. Accordingly, the specification of our prototype is promising for low weight and pediatric patients. Full article
(This article belongs to the Section Fundamentals of Membrane Processes)
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Open AccessReview
Curvature-Dependent Electrostatic Field as a Principle for Modelling Membrane-Based MEMS Devices. A Review
Membranes 2020, 10(11), 361; https://doi.org/10.3390/membranes10110361 - 21 Nov 2020
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Abstract
The evolution of engineering applications is increasingly shifting towards the embedded nature, resulting in low-cost solutions, micro/nano dimensional and actuators being exploited as fundamental components to connect the physical nature of information with the abstract one, which is represented in the logical form [...] Read more.
The evolution of engineering applications is increasingly shifting towards the embedded nature, resulting in low-cost solutions, micro/nano dimensional and actuators being exploited as fundamental components to connect the physical nature of information with the abstract one, which is represented in the logical form in a machine. In this context, the scientific community has gained interest in modeling membrane Micro-Electro-Mechanical-Systems (MEMS), leading to a wide diffusion on an industrial level owing to their ease of modeling and realization. Physically, once the external voltage is applied, an electrostatic field, orthogonal to the tangent line of the membrane, is established inside the device, producing an electrostatic pressure that acts on the membrane, deforming it. Evidently, the greater the amplitude of the electrostatic field is, the greater the curvature of the membrane. Thus, it seems natural to consider the amplitude of the electrostatic field proportional to the curvature of the membrane. Starting with this principle, the authors are actively involved in developing a second-order semi-linear elliptic model in 1D and 2D geometries, obtaining important results regarding the existence, uniqueness and stability of solutions as well as evaluating the particular operating conditions of use of membrane MEMS devices. In this context, the idea of providing a survey matures to discussing the similarities and differences between the analytical and numerical results in detail, thereby supporting the choice of certain membrane MEMS devices according to the industrial application. Finally, some original results about the stability of the membrane in 2D geometry are presented and discussed. Full article
(This article belongs to the Special Issue Microfluidics and MEMS Technology for Membranes)
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Open AccessArticle
Monitoring Biofouling Potential Using ATP-Based Bacterial Growth Potential in SWRO Pre-Treatment of a Full-Scale Plant
Membranes 2020, 10(11), 360; https://doi.org/10.3390/membranes10110360 - 21 Nov 2020
Viewed by 365
Abstract
Several potential growth methods have been developed to monitor biological/organic fouling potential in seawater reverse osmosis (SWRO), but to date the correlation between these methods and biofouling of SWRO has not been demonstrated. In this research, the relation between a new adenosine triphosphate [...] Read more.
Several potential growth methods have been developed to monitor biological/organic fouling potential in seawater reverse osmosis (SWRO), but to date the correlation between these methods and biofouling of SWRO has not been demonstrated. In this research, the relation between a new adenosine triphosphate (ATP)-based bacterial growth potential (BGP) test of SWRO feed water and SWRO membrane performance is investigated. For this purpose, the pre-treatment of a full-scale SWRO plant including dissolved air flotation (DAF) and two stage dual media filtration (DMF) was monitored for 5 months using BGP, orthophosphate, organic fractions by liquid chromatography coupled with organic carbon detection (LC-OCD), silt density index (SDI), and modified fouling index (MFI). Results showed that particulate fouling potential was well controlled through the SWRO pre-treatment as the measured SDI and MFI in the SWRO feed water were below the recommended values. DAF in combination with coagulation (1–5 mg-Fe3+/L) consistently achieved 70% removal of orthophosphate, 50% removal of BGP, 25% removal of biopolymers, and 10% removal of humic substances. Higher BGP (100–950 µg-C/L) in the SWRO feed water corresponded to a higher normalized pressure drop in the SWRO, suggesting the applicability of using BGP as a biofouling indicator in SWRO systems. However, to validate this conclusion, more SWRO plants with different pre-treatment systems need to be monitored for longer periods of time. Full article
(This article belongs to the Special Issue Seawater Reverse Osmosis Desalination)
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Open AccessEditorial
Composite Electrolyte & Electrode Membranes for Electrochemical Energy Storage & Conversion Devices
Membranes 2020, 10(11), 359; https://doi.org/10.3390/membranes10110359 - 21 Nov 2020
Viewed by 319
Open AccessArticle
Monolayer Graphene Transfer onto Hydrophilic Substrates: A New Protocol Using Electrostatic Charging
Membranes 2020, 10(11), 358; https://doi.org/10.3390/membranes10110358 - 20 Nov 2020
Viewed by 189
Abstract
In the present work, we developed a novel method for transferring monolayer graphene onto four different commercial hydrophilic micro/ultra-filtration substrates. The developed method used electrostatic charging to maintain the contact between the graphene and the target substrate intact during the etching step through [...] Read more.
In the present work, we developed a novel method for transferring monolayer graphene onto four different commercial hydrophilic micro/ultra-filtration substrates. The developed method used electrostatic charging to maintain the contact between the graphene and the target substrate intact during the etching step through the wet transfer process. Several measurement/analysis techniques were used in order to evaluate the properties of the surfaces and to assess the quality of the transferred graphene. The techniques included water contact angle (CA), atomic force microscopy (AFM), and field emission scanning electron microscopy (FESEM). Potassium chloride (KCl) ions were used for the transport study through the developed graphene-based membranes. The results revealed that 70% rejection of KCI ions was recorded for the graphene/polyvinylidene difluoride (PVDF1) membrane, followed by 67% rejection for the graphene/polyethersulfone (PES) membrane, and 65% rejection for graphene/PVDF3 membrane. It was revealed that the smoothest substrate was the most effective in rejecting the ions. Although defects such as tears and cracks within the graphene layer were still evolving in this new transfer method, however, the use of Nylon 6,6 interfacial polymerization allowed sealing the tears and cracks within the graphene monolayer. This enhanced the KCl ions rejection of up to 85% through the defect-sealed graphene/polymer composite membranes. Full article
(This article belongs to the Section Membrane Preparation and Characterization)
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Open AccessArticle
Interaction between the Lentil Lipid Transfer Protein Lc-LTP2 and Its Novel Signal Ligand PI(4,5)P2
Membranes 2020, 10(11), 357; https://doi.org/10.3390/membranes10110357 - 20 Nov 2020
Viewed by 189
Abstract
It is known that plant lipid transfer proteins (LTPs) bind a broad spectrum of ligands including fatty acids (FAs), phospho- and glycolipids, acyl-coenzyme A and secondary metabolites. In this work, we used protein−lipid overlay assays to identify new putative LTP ligands. In our [...] Read more.
It is known that plant lipid transfer proteins (LTPs) bind a broad spectrum of ligands including fatty acids (FAs), phospho- and glycolipids, acyl-coenzyme A and secondary metabolites. In this work, we used protein−lipid overlay assays to identify new putative LTP ligands. In our experiments, the lentil lipid transfer protein Lc-LTP2 as well as LTPs from other plants were shown to bind phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2). Molecular modeling, 2-p-toluidinonaphthalene-6-sulphonate (TNS) displacement and liposome leakage experiments with Lc-LTP2 and its mutant analogs (R45A, Y80A, R45A/Y80A) were performed to investigate interactions between the protein and PI(4,5)P2. It was shown that PI(4,5)P2 initially interacted with the “bottom” entrance of the protein cavity and after complex formation the large polar head of this ligand was also oriented towards the same entrance. We also found that two highly conserved residues in plant LTPs, Arg45 and Tyr80, played an important role in protein-ligand interactions. Apparently, Arg45 is a key residue for interaction with PI(4,5)P2 during both initial contacting and holding in the protein cavity, while Tyr80 is probably a key amino acid playing an essential role in Lc-LTP2 docking to the membrane. Thus, we assumed that the ability of Lc-LTP2 to bind PI(4,5)P2 suggests the involvement of this protein in plant signal transduction. Full article
(This article belongs to the Special Issue Protein-Lipid Interactions as Key Regulators of Cell Function)
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Open AccessArticle
Influence of Sodium Hypochlorite Treatment on Pore Size Distribution of Polysulfone/Polyvinylpyrrolidone Membranes
Membranes 2020, 10(11), 356; https://doi.org/10.3390/membranes10110356 - 19 Nov 2020
Viewed by 195
Abstract
This work was focused on the study of hypochlorite treatment on the pore size distribution of membranes. To this end, ultrafiltration membranes from a polysulfone/polyvinylpyrrolidone blend with a sponge-like structure were fabricated and exposed to hypochlorite solutions with different active chlorine concentrations for [...] Read more.
This work was focused on the study of hypochlorite treatment on the pore size distribution of membranes. To this end, ultrafiltration membranes from a polysulfone/polyvinylpyrrolidone blend with a sponge-like structure were fabricated and exposed to hypochlorite solutions with different active chlorine concentrations for 4 h at ambient temperature. Liquid–liquid displacement and scanning electron microscopy were employed to study the limiting and surface pores, respectively. After treatment with 50 ppm hypochlorite solution at pH = 7.2, a five-fold increase in water permeance up to 1400 L/(m2·h·bar) was observed, accompanied by a 40% increase in the limiting pore sizes and almost a three-fold increase in the porosity. After 5000 ppm treatment at pH = 11.5, a 40% rise in the maximum limiting pore size and almost a two-fold increase in the porosity and permeance was observed, whereas the mean pore size was constant. Apparently, changes in the membrane structure at pH = 11.5 were connected with polyvinylpyrrolidone (PVP) degradation and wash-out, whereas at lower pH and despite lower active chlorine concentration, this process was coupled with polysulfone (PSf) destruction and removal. Full article
(This article belongs to the Special Issue Membranes for Water, Gas and Ion Separation)
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Open AccessCommunication
MEA Preparation for Direct Formate/Formic Acid Fuel Cell—Comparison of Palladium Black and Palladium Supported on Activated Carbon Performance on Power Generation in Passive Fuel Cell
Membranes 2020, 10(11), 355; https://doi.org/10.3390/membranes10110355 - 19 Nov 2020
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Abstract
Membrane electrode assemblies (MEAs) with palladium catalysts were successfully prepared by using a home-made manual pressing system with Nafion glue application that contributed to a decrease of additional energy consumption. The catalyst coated membranes were prepared with supported palladium on activated carbon (PdC) [...] Read more.
Membrane electrode assemblies (MEAs) with palladium catalysts were successfully prepared by using a home-made manual pressing system with Nafion glue application that contributed to a decrease of additional energy consumption. The catalyst coated membranes were prepared with supported palladium on activated carbon (PdC) and unsupported palladium black (PdB) for comparison. The performance of passive, air breathing, functioning under ambient conditions and with low concentration (1 M) formate/formic acid fuel cell was evaluated. Based on polarization curves, the best result was obtained with carbon supported catalyst and HCOOK fuel, achieving 21.01 mW/mgPd. Still, constant current discharge with PdC showed an energy generation efficiency of 14% with HCOOH over 3% with HCOOK caused by lower potassium ion conductivity and its permeability through the proton exchange membrane. The faradic efficiency of conversion in the cell is equal to the overall energy efficiency and makes the cell self-sufficient. Full article
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Open AccessArticle
Silica Nanoparticles Reinforced Ionogel as Nonvolatile and Stretchable Conductors
Membranes 2020, 10(11), 354; https://doi.org/10.3390/membranes10110354 - 19 Nov 2020
Viewed by 205
Abstract
Ionogels combine the advantages of being conductive, stretchable, transparent and nonvolatile, which makes them suitable to be applied as conductors for flexible electronic devices. In this paper, a series of ionogels based on 1-ethyl-3-methylimidazolium ethyl-sulfate ([C2mim][EtSO4]) and polyacrylic networks [...] Read more.
Ionogels combine the advantages of being conductive, stretchable, transparent and nonvolatile, which makes them suitable to be applied as conductors for flexible electronic devices. In this paper, a series of ionogels based on 1-ethyl-3-methylimidazolium ethyl-sulfate ([C2mim][EtSO4]) and polyacrylic networks were prepared. Silica nanoparticles (SNPs) were dispersed into the ionogel matrix to enhance its mechanical properties. The thermal, mechanical and electrical properties of the ionogels with various contents of crosslinking agents and SNPs were studied. The results show that a small amount of SNP doping just increases the breaking strain/stress and the nonvolatility of ionogels, as well as maintaining adequate conductivity and a high degree of transparency. Furthermore, the experimental results demonstrate that SNP-reinforced ionogels can be applied as conductors for dielectric elastomer actuators and stretchable wires, as well as for signal transmission. Full article
(This article belongs to the Special Issue Electrically Conductive Membranes)
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Open AccessArticle
Investigation into the Novel Microalgae Membrane Bioreactor with Internal Circulating Fluidized Bed for Marine Aquaculture Wastewater Treatment
Membranes 2020, 10(11), 353; https://doi.org/10.3390/membranes10110353 - 18 Nov 2020
Viewed by 276
Abstract
A microalgae membrane bioreactor (MMBR) with internal circulating fluidized bed (ICFB) was constructed at room temperature to study the removal efficiency of marine aquaculture wastewater pollutants and continuously monitor the biomass of microalgae. Within 40 days of operation, the removal efficiency of NO [...] Read more.
A microalgae membrane bioreactor (MMBR) with internal circulating fluidized bed (ICFB) was constructed at room temperature to study the removal efficiency of marine aquaculture wastewater pollutants and continuously monitor the biomass of microalgae. Within 40 days of operation, the removal efficiency of NO3–N and NH4+–N in the ICFB-MMBR reached 52% and 85%, respectively, and the removal amount of total nitrogen (TN) reached 16.2 mg/(L·d). In addition, the reactor demonstrated a strong phosphorus removal capacity. The removal efficiency of PO43−–P reached 80%. With the strengthening of internal circulation, the microalgae could be distributed evenly and enriched quickly. The maximum growth rate and biomass concentration reached 60 mg/(L·d) and 1.4 g/L, respectively. The harvesting of microalgae did not significantly affect the nitrogen and phosphorus removal efficiency of ICFB-MMBR. The membrane fouling of the reactor was investigated by monitoring transmembrane pressure difference (TMP). Overall, the membrane fouling cycle of ICFB-MMBR system was more than 40 days. Full article
(This article belongs to the Special Issue Advanced Membrane Processes in Water Treatment)
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Open AccessFeature PaperArticle
Experimental Evaluation of Anion Exchange Membranes for the Desalination of (Waste) Water Produced after Polymer-Flooding
Membranes 2020, 10(11), 352; https://doi.org/10.3390/membranes10110352 - 18 Nov 2020
Viewed by 246
Abstract
Electrodialysis (ED) has been recently proposed to desalinate polymer-flooding produced water (PFPW), a byproduct stream from the oil and gas industry rich in charged polymers. However, process performance is limited by fouling occurring on the ion-exchange membranes, particularly on the anionic ones (AEMs). [...] Read more.
Electrodialysis (ED) has been recently proposed to desalinate polymer-flooding produced water (PFPW), a byproduct stream from the oil and gas industry rich in charged polymers. However, process performance is limited by fouling occurring on the ion-exchange membranes, particularly on the anionic ones (AEMs). Thus, this study aimed to correlate the properties of different AEMs with their performance while desalinating PFPW, ultimately evaluating their significance when fouling is to be minimized and operation improved. Six stacks containing different homogeneous and commercially available AEMs were employed to desalinate synthetic PFPW during 8-days ED experiments operated in reversal mode. AEMs recovered from the stacks were analyzed in terms of water uptake, ion-exchange capacity, permselectivity, and area resistance, and compared with virgin AEMs. Relatively small changes were measured for most of the parameters evaluated. For most AEMs, the water uptake and resistance increased, while the ion-exchange capacity (IEC) and permselectivity decreased during operation. Ultimately, AEMs with high area resistance were linked to the fast development of limiting current conditions in the stack, so this property turned out to be the most relevant when desalinating PFPW. Full article
(This article belongs to the Special Issue Modelling and Experiment of Anion-Exchange Membranes)
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Open AccessArticle
Dependence of Water-Permeable Chitosan Membranes on Chitosan Molecular Weight and Alkali Treatment
Membranes 2020, 10(11), 351; https://doi.org/10.3390/membranes10110351 - 18 Nov 2020
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Abstract
Chitosan membranes were prepared by the casting method combined with alkali treatment. The molecular weight of chitosan and the alkali treatment influenced the water content and water permeability of the chitosan membranes. The water content increased as the NaOH concentration was increased from [...] Read more.
Chitosan membranes were prepared by the casting method combined with alkali treatment. The molecular weight of chitosan and the alkali treatment influenced the water content and water permeability of the chitosan membranes. The water content increased as the NaOH concentration was increased from 1 to 5 mol/L. The water permeation flux of chitosan membranes with three different molecular weights increased linearly with the operating pressure and was highest for the membrane formed from chitosan with the lowest molecular weight. Membranes with a lower water content had a higher water flux. The membranes blocked 100% of compounds with molecular weights above methyl orange (MW = 327 Da). At 60 ≤ MW ≤ 600, the blocking rate strongly depended on the substance. The results confirmed that the membranes are suitable for compound separation, such as in purification and wastewater treatment. Full article
(This article belongs to the Special Issue Membranes for Water and Wastewater Treatment)
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Open AccessArticle
Impact of Permeable Membrane on the Hydrocyclone Separation Performance for Oily Water Treatment
Membranes 2020, 10(11), 350; https://doi.org/10.3390/membranes10110350 - 18 Nov 2020
Viewed by 230
Abstract
In the oil industry and academy, the treatment of water contaminated with oil using conventional hydrocyclones and membranes has been an alternative to meet the requirements established by environmental control agencies. However, such equipment is not fully efficient in the treatment of much [...] Read more.
In the oil industry and academy, the treatment of water contaminated with oil using conventional hydrocyclones and membranes has been an alternative to meet the requirements established by environmental control agencies. However, such equipment is not fully efficient in the treatment of much diluted oily water, with both presenting restrictions in their performance. In this sense, the present work proposes to study the separation process of oily water using a new configuration of hydrocyclone, equipped with a porous ceramic membrane in the conical part’s wall (filtering hydrocyclone). For the theoretical study, a Eulerian–Eulerian approach was applied to solve the mass and momentum conservation equations, and the turbulence model, using the computational fluid dynamics technique. The results of the velocity, pressure and volumetric fraction of the involved phases, and the separation performance of the hydrocyclone, are presented, analyzed, and compared with those obtained with a conventional hydrocyclone. The results confirmed the high potential of the proposed equipment to be used in the separation of the water and oil mixture. Full article
(This article belongs to the Special Issue Numerical Modelling in Membrane Processes)
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Open AccessArticle
Application of Crosslinked Polybenzimidazole-Poly(Vinyl Benzyl Chloride) Anion Exchange Membranes in Direct Ethanol Fuel Cells
Membranes 2020, 10(11), 349; https://doi.org/10.3390/membranes10110349 - 17 Nov 2020
Viewed by 183
Abstract
Crosslinked membranes have been synthesized by a casting process using polybenzimidazole (PBI) and poly(vinyl benzyl chloride) (PVBC). The membranes were quaternized with 1,4-diazabicyclo[2.2.2]octane (DABCO) to obtain fixed positive quaternary ammonium groups. XPS analysis has showed insights into the changes from crosslinked to quaternized [...] Read more.
Crosslinked membranes have been synthesized by a casting process using polybenzimidazole (PBI) and poly(vinyl benzyl chloride) (PVBC). The membranes were quaternized with 1,4-diazabicyclo[2.2.2]octane (DABCO) to obtain fixed positive quaternary ammonium groups. XPS analysis has showed insights into the changes from crosslinked to quaternized membranes, demonstrating that the crosslinking reaction and the incorporation of DABCO have occurred, while the 13C-NMR corroborates the reaction of DABCO with PVBC only by one nitrogen atom. Mechanical properties were evaluated, obtaining maximum stress values around 72 MPa and 40 MPa for crosslinked and quaternized membranes, respectively. Resistance to oxidative media was also satisfactory and the membranes were evaluated in single direct ethanol fuel cell. PBI-c-PVBC/OH 1:2 membrane obtained 66 mW cm−2 peak power density, 25% higher than commercial PBI membranes, using 0.5 bar backpressure of pure O2 in the cathode and 1 mL min−1 KOH 2M EtOH 2 M aqueous solution in the anode. When the pressure was increased, the best performance was obtained by the same membrane, reaching 70 mW cm−2 peak power density at 2 bar O2 backpressure. Based on the characterization and single cell performance, PBI-c-PVBC/OH membranes are considered promising candidates as anion exchange electrolytes for direct ethanol fuel cells. Full article
(This article belongs to the Special Issue Anion Exchange Membrane Fuel Cells and Electrolyzers)
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Open AccessReview
Review of Synthetic and Hybrid Scaffolds in Cartilage Tissue Engineering
Membranes 2020, 10(11), 348; https://doi.org/10.3390/membranes10110348 - 17 Nov 2020
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Abstract
Cartilage tissue is under extensive investigation in tissue engineering and regenerative medicine studies because of its limited regenerative potential. Currently, many scaffolds are undergoing scientific and clinical research. A key for appropriate scaffolding is the assurance of a temporary cellular environment that allows [...] Read more.
Cartilage tissue is under extensive investigation in tissue engineering and regenerative medicine studies because of its limited regenerative potential. Currently, many scaffolds are undergoing scientific and clinical research. A key for appropriate scaffolding is the assurance of a temporary cellular environment that allows the cells to function as in native tissue. These scaffolds should meet the relevant requirements, including appropriate architecture and physicochemical and biological properties. This is necessary for proper cell growth, which is associated with the adequate regeneration of cartilage. This paper presents a review of the development of scaffolds from synthetic polymers and hybrid materials employed for the engineering of cartilage tissue and regenerative medicine. Initially, general information on articular cartilage and an overview of the clinical strategies for the treatment of cartilage defects are presented. Then, the requirements for scaffolds in regenerative medicine, materials intended for membranes, and methods for obtaining them are briefly described. We also describe the hybrid materials that combine the advantages of both synthetic and natural polymers, which provide better properties for the scaffold. The last part of the article is focused on scaffolds in cartilage tissue engineering that have been confirmed by undergoing preclinical and clinical tests. Full article
(This article belongs to the Special Issue Membrane Systems for Tissue Engineering 2020)
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Open AccessArticle
Desalination Performance Assessment of Scalable, Multi-Stack Ready Shock Electrodialysis Unit Utilizing Anion-Exchange Membranes
Membranes 2020, 10(11), 347; https://doi.org/10.3390/membranes10110347 - 17 Nov 2020
Viewed by 292
Abstract
Incumbent electromembrane separation processes, including electrodialysis (ED) and electrodeionization (EDI), provide competitive techniques for desalination, selective separation, and unique solutions for ultra-pure water production. However, most of these common electrochemical systems are limited by concentration polarization and the necessity for multistep raw water [...] Read more.
Incumbent electromembrane separation processes, including electrodialysis (ED) and electrodeionization (EDI), provide competitive techniques for desalination, selective separation, and unique solutions for ultra-pure water production. However, most of these common electrochemical systems are limited by concentration polarization and the necessity for multistep raw water pre-treatment. Shock electrodialysis (SED) utilizes overlimiting current to produce fresh, deionized water in a single step process by extending ion depleted zones that propagate through a porous medium as a sharp concentration gradient or a shock wave. So far, SED has been demonstrated on small scale laboratory units using cation-exchange membranes. In this work, we present a scalable and multi-stack ready unit with a large, 5000 mm2 membrane active area designed and constructed at the Technical University of Liberec in cooperation with MemBrain s.r.o. and Mega a.s. companies (Czechia). We report more than 99% salt rejection using anion-exchange membranes, depending on a dimensionless parameter that scales the constant applied current by the limiting current. It is shown that these parameters are most probably associated with pore size and porous media chemistry. Further design changes need to be done to the separator, the porous medium, and other functional elements to improve the functionality and energy efficiency. Full article
(This article belongs to the Special Issue Modelling and Experiment of Anion-Exchange Membranes)
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Open AccessArticle
Water Splitting and Transport of Ions in Electromembrane System with Bilayer Ion-Exchange Membrane
Membranes 2020, 10(11), 346; https://doi.org/10.3390/membranes10110346 - 16 Nov 2020
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Abstract
Bilayer ion-exchange membranes are mainly used for separating single and multiply charged ions. It is well known that in membranes in which the layers have different charges of the ionogenic groups of the matrix, the limiting current decreases, and the water splitting reaction [...] Read more.
Bilayer ion-exchange membranes are mainly used for separating single and multiply charged ions. It is well known that in membranes in which the layers have different charges of the ionogenic groups of the matrix, the limiting current decreases, and the water splitting reaction accelerates in comparison with monolayer (isotropic) ion-exchange membranes. We study samples of bilayer ion-exchange membranes with very thin cation-exchange layers deposited on an anion-exchange membrane-substrate in this work. It was revealed that in bilayer membranes, the limiting current’s value is determined by the properties of a thin surface film (modifying layer). A linear regularity of the dependence of the non-equilibrium effective rate constant of the water-splitting reaction on the resistance of the bipolar region, which is valid for both bilayer and bipolar membranes, has been revealed. It is shown that the introduction of the catalyst significantly reduces the water-splitting voltage, but reduces the selectivity of the membrane. It is possible to regulate the fluxes of salt ions and water splitting products (hydrogen and hydroxyl ions) by changing the current density. Such an ability makes it possible to conduct a controlled process of desalting electrolytes with simultaneous pH adjustment. Full article
(This article belongs to the Special Issue Modelling and Experiment of Anion-Exchange Membranes)
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Open AccessArticle
Separation of Alcohol-Water Mixtures by a Combination of Distillation, Hydrophilic and Organophilic Pervaporation Processes
Membranes 2020, 10(11), 345; https://doi.org/10.3390/membranes10110345 - 16 Nov 2020
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Abstract
It can be stated that in the fine chemical industries, especially in the pharmaceutical industry, large amounts of liquid waste and industrial waste solvents are generated during the production technology. Addressing these is a key issue because their disposal often accounts for the [...] Read more.
It can be stated that in the fine chemical industries, especially in the pharmaceutical industry, large amounts of liquid waste and industrial waste solvents are generated during the production technology. Addressing these is a key issue because their disposal often accounts for the largest proportion of the cost of the entire technology. There is need to develop regeneration processes that are financially beneficial to the plant and, if possible, reuse the liquid waste in the spirit of a circular economy, in a particular technology, or possibly elsewhere. The distillation technique proves to be a good solution in many cases, but in the case of mixtures with high water content and few volatile components, this process is often not cost-effective due to its high steam consumption, and in the case of azeotropic mixtures there are separation constraints. In the present work, the membrane process considered as an alternative; pervaporation is demonstrated through the treatment of low alcohol (methanol and ethanol) aqueous mixtures. Alcohol-containing process wastewaters were investigated in professional process simulator environment with user-added pervaporation modules. Eight different methods were built up in ChemCAD flowsheet simulator: organophilic pervaporation (OPV), hydrophilic pervaporation (HPV), hydrophilic pervaporation with recirculation (R-HPV), dynamic organophilic pervaporation (Dyn-OPV), dynamic hydronophilic pervaporation (Dyn-HPV), hybrid distillation-organophilic pervaporation (D + OPV), hybrid distillation-hydrophilic pervaporation (D + HPV), and finally hybrid distillation-hydrophilic pervaporation with recirculation (R-D + HPV). It can be stated the last solution in line was the most suitable in the terms of composition, however distillation of mixture with high water content has significant heat consumption. Furthermore, the pervaporation supplemented with dynamic tanks is not favourable due to the high recirculation rate in the case of tested mixtures and compositions. Full article
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Open AccessArticle
Effect of Alkali Treatment on the Mechanical Properties of Anion-Exchange Membranes with a Poly(vinyl Chloride) Backing and Binder
Membranes 2020, 10(11), 344; https://doi.org/10.3390/membranes10110344 - 16 Nov 2020
Viewed by 254
Abstract
An alkali treatment under various operating conditions is conducted on a commercial anion-exchange membrane containing poly(vinyl chloride) (PVC) as a backing and binder to study the effect of the treatment on the mechanical properties by both Müllen burst and tensile tests. Contrary to [...] Read more.
An alkali treatment under various operating conditions is conducted on a commercial anion-exchange membrane containing poly(vinyl chloride) (PVC) as a backing and binder to study the effect of the treatment on the mechanical properties by both Müllen burst and tensile tests. Contrary to our expectations, the Müllen burst pressure and tensile strain at break improved significantly after the alkali treatment in comparison to the pristine membrane and then decreased as the treatment period progressed. A good correlation is observed between the area below the stress–strain curve and burst pressure. To understand the obtained results, the PVC degradates are recovered by Soxhlet extraction and characterized via nuclear magnetic resonance and gel permeation chromatography. It is discovered that the PVC main chains degraded in the alkali solution. We propose a composite model to explain the burst pressure improvement mechanism by the change in the chemical structure of the PVC binder. Full article
(This article belongs to the Special Issue Modelling and Experiment of Anion-Exchange Membranes)
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Open AccessArticle
Electrophoretic Light Scattering and Electrochemical Impedance Spectroscopy Studies of Lipid Bilayers Modified by Cinnamic Acid and Its Hydroxyl Derivatives
Membranes 2020, 10(11), 343; https://doi.org/10.3390/membranes10110343 - 15 Nov 2020
Viewed by 248
Abstract
Pharmacological efficiency of active compounds is largely determined by their membrane permeability. Thus, identification of drug-membrane interactions seems to be a crucial element determining drug-like properties of chemical agents. Yet, knowledge of this issue is still lacking. Since chemoprevention based on natural compounds [...] Read more.
Pharmacological efficiency of active compounds is largely determined by their membrane permeability. Thus, identification of drug-membrane interactions seems to be a crucial element determining drug-like properties of chemical agents. Yet, knowledge of this issue is still lacking. Since chemoprevention based on natural compounds such as cinnamic acid (CinA), p-coumaric acid (p-CoA) and ferulic (FA) is becoming a strong trend in modern oncopharmacology, determination of physicochemical properties of these anticancer compounds is highly important. Here, electrophoretic light scattering and impedance spectroscopy were applied to study the effects of these phenolic acids on electrical properties of bilayers formed from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-diacyl-sn-glycero-3-phospho-l-serine (PS) or DOPC-PS mixture. After phenolic acid treatment, the negative charge of membranes increased in alkaline pH solutions, but not in acidic ones. The impedance data showed elevated values of both the electrical capacitance and the electrical resistance. We concluded that at acidic pH all tested compounds were able to solubilize into the membrane and permeate it. At neutral and alkaline pH, the CinA could be partially inserted into the bilayers, whereas p-CoA and FA could be anchored at the bilayer surface. Our results indicate that the electrochemical methods might be crucial for predicting pharmacological activity and bioavailability of phenolic acids. Full article
(This article belongs to the Special Issue Electrical Properties of Model Lipid Membranes)
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Theoretical Analysis of the Stationary Transport of 1:1 Salt Ions in a Cross-Section of a Desalination Channel, Taking into Account the Non-Catalytic Dissociation/Recombination Reaction of Water Molecules
Membranes 2020, 10(11), 342; https://doi.org/10.3390/membranes10110342 - 13 Nov 2020
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Abstract
In electromembrane systems, the theoretical study of salt ion transport usually uses mathematical models of salt ion transport in the depleted diffusion layer of ion-exchange membranes. This study uses a one-dimensional mathematical model of salt ion transport in a cross-section of a desalination [...] Read more.
In electromembrane systems, the theoretical study of salt ion transport usually uses mathematical models of salt ion transport in the depleted diffusion layer of ion-exchange membranes. This study uses a one-dimensional mathematical model of salt ion transport in a cross-section of a desalination channel formed by anion-exchange and cation-exchange membranes, taking into account an effect of a dissociation/recombination reaction of water molecules. The reaction on the one hand leads to an overlimiting mass transfer due to the effect of exaltation of the limiting current. On the other hand, an appearance of new electric charge carriers (hydrogen and hydroxyl ions) can reduce the space charge that occurs in membranes and suppress an electroconvective mechanism of overlimiting transport. Thus, there is a problem of studying these phenomena together, taking into account their mutual influence, and this article is devoted to the solution of this problem. Theoretically, using a method of mathematical modeling and numerical research, main regularities are established; in particular, it is shown that the dissociation/recombination reaction of water molecules does not lead to the destruction of the double electric layer at the membranes, but also creates a new double electric layer in the middle of the desalination channel. Thus, the space charge and the dissociation/recombination reaction significantly affect each other and simultaneously the transport of salt ions. Full article
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Open AccessArticle
Thin Graphene–Nanotube Films for Electronic and Photovoltaic Devices: DFTB Modeling
Membranes 2020, 10(11), 341; https://doi.org/10.3390/membranes10110341 - 13 Nov 2020
Viewed by 197
Abstract
Supercell atomic models of composite films on the basis of graphene and single-wall carbon nanotubes (SWCNTs) with an irregular arrangement of SWCNTs were built. It is revealed that composite films of this type have a semiconducting type of conductivity and are characterized by [...] Read more.
Supercell atomic models of composite films on the basis of graphene and single-wall carbon nanotubes (SWCNTs) with an irregular arrangement of SWCNTs were built. It is revealed that composite films of this type have a semiconducting type of conductivity and are characterized by the presence of an energy gap of 0.43–0.73 eV. It was found that the absorption spectrum of composite films contained specific peaks in a wide range of visible and infrared (IR) wavelengths. On the basis of calculated composite films volt-ampere characteristics (VAC), the dependence of the current flowing through the films on the distance between the nanotubes was identified. For the investigated composites, spectral dependences of the photocurrent were calculated. It was shown that depending on the distance between nanotubes, the maximum photocurrent might shift from the IR to the optical range. Full article
(This article belongs to the Section Membrane Preparation and Characterization)
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Open AccessArticle
Reduced Graphene Oxide-Based Foam as an Endocrine Disruptor Adsorbent in Aqueous Solutions
Membranes 2020, 10(11), 340; https://doi.org/10.3390/membranes10110340 - 13 Nov 2020
Viewed by 268
Abstract
A stable and magnetic graphene oxide (GO) foam–polyethyleneimine–iron nanoparticle (GO–PEI–FeNPs) composite has been fabricated for removal of endocrine disruptors—bisphenol A, progesterone and norethisterone—from aqueous solution. The foam with porous and hierarchical structures was synthesized by reduction of graphene oxide layers coupled with co-precipitation [...] Read more.
A stable and magnetic graphene oxide (GO) foam–polyethyleneimine–iron nanoparticle (GO–PEI–FeNPs) composite has been fabricated for removal of endocrine disruptors—bisphenol A, progesterone and norethisterone—from aqueous solution. The foam with porous and hierarchical structures was synthesized by reduction of graphene oxide layers coupled with co-precipitation of iron under a hydrothermal system using polyethyleneimine as a cross linker. The presence of magnetic iron nanoparticles facilitates the separation process after decontamination. The foam was fully characterized by surface and structural scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The foam exhibits a high adsorption capacity, and the maximum adsorption percentages are 68%, 49% and 80% for bisphenol A, progesterone and norethisterone, respectively. The adsorption process of bisphenol A is explained according to the Langmuir model, whereas the Freundlich model was used for progesterone and norethisterone adsorption. Full article
(This article belongs to the Special Issue Advancements of 2D Materials-based Membranes)
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Open AccessArticle
Processing Ceramic Proton Conductor Membranes for Use in Steam Electrolysis
Membranes 2020, 10(11), 339; https://doi.org/10.3390/membranes10110339 - 12 Nov 2020
Viewed by 256
Abstract
Steam electrolysis constitutes a prospective technology for industrial-scale hydrogen production. The use of ceramic proton-conducting electrolytes is a beneficial option for lowering the operating temperature. However, a significant challenge with this type of electrolyte has been upscaling robust planar type devices. The fabrication [...] Read more.
Steam electrolysis constitutes a prospective technology for industrial-scale hydrogen production. The use of ceramic proton-conducting electrolytes is a beneficial option for lowering the operating temperature. However, a significant challenge with this type of electrolyte has been upscaling robust planar type devices. The fabrication of such multi-layered devices, usually via a tape casting process, requires careful control of individual layers’ shrinkages to prevent warping and cracks during sintering. The present work highlights the successful processing of 50 × 50 mm2 planar electrode-supported barium cerium yttrium zirconate BaZr0.44Ce0.36Y0.2O2.9 (BZCY(54)8/92) half cells via a sequential tape casting approach. The sintering parameters of the half-cells were analyzed and adjusted to obtain defect-free half-cells with diminished warping. Suitably dense and gas-tight electrolyte layers are obtained after co-sintering at 1350 °C for 5 h. We then assembled an electrolysis cell using Ba0.5La0.5CoO3−δ as the steam electrode, screen printed on the electrolyte layer, and fired at 800 °C. A typical Ba0.5La0.5CoO3−δ|BaZr0.44Ce0.36Y0.2O3−δ(15 μm)|NiO-SrZr0.5Ce0.4Y0.1O3−δ cell at 600 °C with 80% steam in the anode compartment reached reproducible terminal voltages of 1.4 V @ 500 mA·cm−2, achieving ~84% Faradaic efficiency. Besides electrochemical characterization, the morphology and microstructure of the layered half-cells were analyzed by a combination of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectroscopy. Our results also provide a feasible approach for realizing the low-cost fabrication of large-sized protonic ceramic conducting electrolysis cells (PCECs). Full article
(This article belongs to the Special Issue Ceramic Membranes for Fuel Cell Applications and Hydrogen Production)
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Open AccessArticle
Hydrogen Purification from Compact Palladium Membrane Module Using a Low Temperature Diffusion Bonding Technology
Membranes 2020, 10(11), 338; https://doi.org/10.3390/membranes10110338 - 12 Nov 2020
Viewed by 221
Abstract
This study investigates a compact palladium membrane module (CPMM) for hydrogen purification, assembled by diffusion bonding at a low-temperature (450 °C). This CPMM resulted in hydrogen (H2) flux of 18.3 mL cm−2 min−1 with H2/N2 selectivity [...] Read more.
This study investigates a compact palladium membrane module (CPMM) for hydrogen purification, assembled by diffusion bonding at a low-temperature (450 °C). This CPMM resulted in hydrogen (H2) flux of 18.3 mL cm−2 min−1 with H2/N2 selectivity of over 1100. The H2 purification test using a 60% H2/40% CO2 mixed gas confirmed that the CPMM can separate H2 with a concentration of more than 99%, with a pressure difference of 5 bar. Moreover, the volume of the diffusion bonded membrane module is decreased by 81.4% than the flame-type membrane module pre-studied in our laboratory. Full article
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Open AccessReview
Membrane Separation Coupled with Electrochemical Advanced Oxidation Processes for Organic Wastewater Treatment: A Short Review
Membranes 2020, 10(11), 337; https://doi.org/10.3390/membranes10110337 - 12 Nov 2020
Viewed by 274
Abstract
Research on the coupling of membrane separation (MS) and electrochemical advanced oxidation processes (EAOPs) has been a hot area in water pollution control for decades. This coupling aims to greatly improve water quality and focuses on the challenges in practical application to provide [...] Read more.
Research on the coupling of membrane separation (MS) and electrochemical advanced oxidation processes (EAOPs) has been a hot area in water pollution control for decades. This coupling aims to greatly improve water quality and focuses on the challenges in practical application to provide a promising solution to water shortage problems. This article provides a summary of the coupling configurations of MS and EAOPs, including two-stage and one-pot processes. The two-stage process is a combination of MS and EAOPs where one process acts as a pretreatment for the other. Membrane fouling is reduced when setting EAOPs before MS, while mass transfer is promoted when placing EAOPs after MS. A one-pot process is a kind of integration of two technologies. The anode or cathode of the EAOPs is fabricated from porous materials to function as a membrane electrode; thus, pollutants are concurrently separated and degraded. The advantages of enhanced mass transfer and the enlarged electroactive area suggest that this process has excellent performance at a low current input, leading to much lower energy consumption. The reported conclusions illustrate that the coupling of MS and EAOPs is highly applicable and may be widely employed in wastewater treatment in the future. Full article
(This article belongs to the Special Issue Membranes: 10th Anniversary)
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Open AccessReview
Graphene-based Membranes for H2 Separation: Recent Progress and Future Perspective
Membranes 2020, 10(11), 336; https://doi.org/10.3390/membranes10110336 - 12 Nov 2020
Viewed by 270
Abstract
Hydrogen (H2) is an industrial gas that has showcased its importance in several well-known processes such as ammonia, methanol and steel productions, as well as in petrochemical industries. Besides, there is a growing interest in H2 production and purification owing [...] Read more.
Hydrogen (H2) is an industrial gas that has showcased its importance in several well-known processes such as ammonia, methanol and steel productions, as well as in petrochemical industries. Besides, there is a growing interest in H2 production and purification owing to the global efforts to minimize the emission of greenhouse gases. Nevertheless, H2 which is produced synthetically is expected to contain other impurities and unreacted substituents (e.g., carbon dioxide, CO2; nitrogen, N2 and methane, CH4), such that subsequent purification steps are typically required for practical applications. In this context, membrane-based separation has attracted a vast amount of interest due to its desirable advantages over conventional separation processes, such as the ease of operation, low energy consumption and small plant footprint. Efforts have also been made for the development of high-performance membranes that can overcome the limitations of conventional polymer membranes. In particular, the studies on graphene-based membranes have been actively conducted most recently, showcasing outstanding H2-separation performances. This review focuses on the recent progress and potential challenges in graphene-based membranes for H2 purification. Full article
(This article belongs to the Special Issue Graphene-Based Membranes: Overview and Perspectives)
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