Membranes

17 pages, 2605 KiB

Open AccessArticle

Laboratory Efficacy of Locally Available Backwashing Methods at Removing Fouling in Hollow-Fiber Membrane Filters Used for Household Water Treatment

by Camille Heylen, Alice Oliveira Aguiar, Gabrielle String, Marta Domini, Nathaniel Goff, Anna Murray, Ayse Asatekin and Daniele Lantagne

Membranes 2021, 11(5), 375; https://doi.org/10.3390/membranes11050375 - 20 May 2021

Cited by 3 | Viewed by 2648

Abstract

Hollow-fiber membrane filters (HFMFs) for household water treatment (HWT) can efficaciously remove disease-causing organisms in laboratory settings. However, lower effectiveness in use in low- and middle-income countries (LMICs) and humanitarian contexts (HCs) has been observed and attributed to membrane fouling and the associated [...] Read more.

Hollow-fiber membrane filters (HFMFs) for household water treatment (HWT) can efficaciously remove disease-causing organisms in laboratory settings. However, lower effectiveness in use in low- and middle-income countries (LMICs) and humanitarian contexts (HCs) has been observed and attributed to membrane fouling and the associated cleaning. In LMICs/HCs, it is not possible to prevent and control fouling using commonly known methods (e.g., testing influent water, maintenance regimes), and the literature on fouling/cleaning of HFMFs distributed in LMICs is scarce. As such, controlled laboratory experiments were conducted to determine the efficacy of locally available (in LMICs/HCs) backwashing solutions at removing fouling using different influent waters and HFMF types. Four commonly distributed HFMFs were selected; fouling layers were developed by filtering three influent water compositions, representing LMIC/HC waters, for 10-days, and bleach, water, or vinegar backwashing solutions were used for daily backwashing. Filter performance indicators included: fiber mechanical properties (strain at break, break force), water quantity performance (flow), water quality performance (turbidity, E. coli), and imaging. The study found fouling developed rapidly and altered mechanical properties and water quantity indicators within 200 h of filtration. Fouling did not decrease water quality indicators. Backwashing improved the filter’s mechanical properties and water quantity performance, but it did not fully recover the initial performance. Additionally, recovery differed between backwashing solutions, and no universal cleaning recommendation appropriate for HFMFs in LMICs/HCs was identified. Overall, fouling development and control depended on HFMF type, influent water quality, and backwashing solution type; thus, caution before distributing HFMFs for long-term use in LMICs/HCs is recommended. Full article

(This article belongs to the Special Issue Hollow Fiber Membranes and Their Applications)

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15 pages, 5209 KiB

Open AccessArticle

Microstructured Hollow Fiber Membranes: Potential Fiber Shapes for Extracorporeal Membrane Oxygenators

by Paul Ecker, Markus Pekovits, Tsvetan Yorov, Bahram Haddadi, Benjamin Lukitsch, Martin Elenkov, Christoph Janeczek, Christian Jordan, Margit Gfoehler and Michael Harasek

Membranes 2021, 11(5), 374; https://doi.org/10.3390/membranes11050374 - 20 May 2021

Cited by 6 | Viewed by 3715

Abstract

Extracorporeal membrane oxygenators are essential medical devices for the treatment of patients with respiratory failure. A promising approach to improve oxygenator performance is the use of microstructured hollow fiber membranes that increase the available gas exchange surface area. However, by altering the traditional [...] Read more.

Extracorporeal membrane oxygenators are essential medical devices for the treatment of patients with respiratory failure. A promising approach to improve oxygenator performance is the use of microstructured hollow fiber membranes that increase the available gas exchange surface area. However, by altering the traditional circular fiber shape, the risk of low flow, stagnating zones that obstruct mass transfer and encourage thrombus formation, may increase. Finding an optimal fiber shape is therefore a significant task. In this study, experimentally validated computational fluid dynamics simulations were used to investigate transverse flow within fiber packings of circular and microstructured fiber geometries. A numerical model was applied to calculate the local Sherwood number on the membrane surface, allowing for qualitative comparison of gas exchange capacities in low-velocity areas caused by the microstructured geometries. These adverse flow structures lead to a tradeoff between increased surface area and mass transfer. Based on our simulations, we suggest an optimal fiber shape for further investigations that increases potential mass transfer by up to 48% in comparison to the traditional, circular hollow fiber shape. Full article

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

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8 pages, 835 KiB

Open AccessArticle

Effects of Thermal Annealing on the Properties of Zirconium-Doped Mg_xZn_1−XO Films Obtained through Radio-Frequency Magnetron Sputtering

by Wen-Yen Lin, Feng-Tsun Chien, Hsien-Chin Chiu, Jinn-Kong Sheu and Kuang-Po Hsueh

Membranes 2021, 11(5), 373; https://doi.org/10.3390/membranes11050373 - 20 May 2021

Cited by 4 | Viewed by 2411

Abstract

Zirconium-doped Mg_xZn_1−xO (Zr-doped MZO) mixed-oxide films were investigated, and the temperature sensitivity of their electric and optical properties was characterized. Zr-doped MZO films were deposited through radio-frequency magnetron sputtering using a 4-inch ZnO/MgO/ZrO₂ (75/20/5 wt%) target. Hall measurement, [...] Read more.

Zirconium-doped Mg_xZn_1−xO (Zr-doped MZO) mixed-oxide films were investigated, and the temperature sensitivity of their electric and optical properties was characterized. Zr-doped MZO films were deposited through radio-frequency magnetron sputtering using a 4-inch ZnO/MgO/ZrO₂ (75/20/5 wt%) target. Hall measurement, X-ray diffraction (XRD), transmittance, and X-ray photoelectron spectroscopy (XPS) data were obtained. The lowest sheet resistance, highest mobility, and highest concentration were 1.30 × 10³ Ω/sq, 4.46 cm²/Vs, and 7.28 × 10¹⁹ cm⁻³, respectively. The XRD spectra of the as-grown and annealed Zr-doped MZO films contained Mg_xZn_1−xO(002) and ZrO₂(200) coupled with Mg(OH)₂(101) at 34.49°, 34.88°, and 38.017°, respectively. The intensity of the XRD peak near 34.88° decreased with temperature because the films that segregated Zr⁴⁺ from ZrO₂(200) increased. The absorption edges of the films were at approximately 348 nm under 80% transmittance because of the Mg content. XPS revealed that the amount of Zr⁴⁺ increased with the annealing temperature. Zr is a potentially promising double donor, providing up to two extra free electrons per ion when used in place of Zn²⁺. Full article

(This article belongs to the Special Issue Thin-Film Transistors)

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13 pages, 2082 KiB

Open AccessArticle

Simulations on Simple Models of Connexin Hemichannels Indicate That Ca²⁺ Blocking Is Not a Pure Electrostatic Effect

by Felipe Villanelo, Jorge Carrasco, Joaquin Jensen-Flores, Jose Antonio Garate and Tomas Perez-Acle

Membranes 2021, 11(5), 372; https://doi.org/10.3390/membranes11050372 - 20 May 2021

Viewed by 2095

Abstract

Connexin hemichannels allow the unspecific but regulated interchange of molecules from ions to second messenger and ATP, between the eukariotic cell and its extracellular space. The transport of ions and water through hemichannels is important for physiological functions and also in the progression [...] Read more.

Connexin hemichannels allow the unspecific but regulated interchange of molecules from ions to second messenger and ATP, between the eukariotic cell and its extracellular space. The transport of ions and water through hemichannels is important for physiological functions and also in the progression of several pathological conditions. Extracellular Ca²⁺ concentration is one of the regulators that drives the channel to a closed state. However the relation between their functional and structural states is far for being totally understood. In this work, we modelled connexin hemichannels using simple systems based on a fixed array of carbon atoms and assess the Ca²⁺ regulation using molecular dynamics simulations. The two proposed mechanism described so far for calcium action were studied combined, e.g., an electrostatic effect and a pore stretching. Our results show that the addition of positive charge density inside the channel cannot stop the flow of potassium, chloride nor water. Only a pore stretching at the center of the pore can explain the channel blocking. Full article

(This article belongs to the Special Issue Electrostatics in Cell Membranes and in Artificial Membrane Models)

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14 pages, 2595 KiB

Open AccessArticle

[EMIM][Tf2N]-Modified Silica as Filler in Mixed Matrix Membrane for Carbon Dioxide Separation

by Siti Nur Alwani Shafie, Nik Abdul Hadi Md Nordin, Muhammad Roil Bilad, Nurasyikin Misdan, Norazlianie Sazali, Zulfan Adi Putra, Mohd Dzul Hakim Wirzal, Alamin Idris, Juhana Jaafar and Zakaria Man

Membranes 2021, 11(5), 371; https://doi.org/10.3390/membranes11050371 - 19 May 2021

Cited by 10 | Viewed by 2677

Abstract

This study focuses on the effect of modified silica fillers by [EMIN][Tf₂N] via physical adsorption on the CO₂ separation performance of a mixed matrix membrane (MMM). The IL-modified silica was successfully synthesized as the presence of fluorine element was observed [...] Read more.

This study focuses on the effect of modified silica fillers by [EMIN][Tf₂N] via physical adsorption on the CO₂ separation performance of a mixed matrix membrane (MMM). The IL-modified silica was successfully synthesized as the presence of fluorine element was observed in both Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectrometer (XPS) analyses. The prepared MMMs with different loadings of the IL-modified silica were then compared with an unmodified silica counterpart and neat membrane. The morphology of IL-modified MMMs was observed to have insignificant changes, while polymer chains of were found to be slightly more flexible compared to their counterpart. At 2 bar of operating pressure, a significant increase in performance was observed with the incorporation of 3 wt% Sil-IL fillers compared to that of pure polycarbonate (PC). The permeability increased from 353 to 1151 Barrer while the CO₂/CH₄ selectivity increased from 20 to 76. The aforementioned increment also exceeded the Robeson upper bound. This indicates that the incorporation of fillers surface-modified with ionic liquid in an organic membrane is worth exploring for CO₂ separation. Full article

(This article belongs to the Special Issue Advanced Polymeric Membranes for Energy & Environment)

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13 pages, 2110 KiB

Open AccessArticle

Effect of Membrane Materials and Operational Parameters on Performance and Energy Consumption of Oil/Water Emulsion Filtration

by Nafiu Umar Barambu, Muhammad Roil Bilad, Nurul Huda, Nik Abdul Hadi Md Nordin, Mohamad Azmi Bustam, Aris Doyan and Jumardi Roslan

Membranes 2021, 11(5), 370; https://doi.org/10.3390/membranes11050370 - 19 May 2021

Cited by 12 | Viewed by 2565

Abstract

Membrane technology is one of reliable options for treatment of oil/water emulsion. It is highly attractive because of its effectiveness in separating fine oil droplets of <2 µm sizes, which is highly challenging for other processes. However, the progress for its widespread implementations [...] Read more.

Membrane technology is one of reliable options for treatment of oil/water emulsion. It is highly attractive because of its effectiveness in separating fine oil droplets of <2 µm sizes, which is highly challenging for other processes. However, the progress for its widespread implementations is still highly restricted by membrane fouling. Most of the earlier studies have demonstrated the promise of achieving more sustained filtration via membrane material developments. This study addresses issues beyond membrane development by assessing the impact of membrane material (blend of polysulfone, PSF and polyethylene glycol, PEG), operational pressure, and crude oil concentration on the filtration performance of oil/water emulsion. The filtration data were then used to project the pumping energy for a full-scale system. Results show that fouling resistant membrane offered high oil/water emulsion permeability, which translated into a low energy consumption. The oil/water emulsion permeability was improved by three-fold from 45 ± 0 to 139 ± 1 L/(m² h bar) for PSF/PEG-0 membrane in comparison to the most optimum one of PSF/PEG-60. It corresponded to an energy saving of up to ~66%. The pumping energy could further be reduced from 27.0 to 7.6 Wh/m³ by operation under ultra-low pressure from 0.2 to 0.05 bar. Sustainable permeability could be achieved when treating 1000 ppm oil/water emulsion, but severe membrane fouling was observed when treating emulsion containing crude oils of >3000 ppm to a point of no flux. Full article

(This article belongs to the Special Issue Advanced Polymeric Membranes for Energy & Environment)

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14 pages, 1755 KiB

Open AccessArticle

Effect of Pre-Oxidation on Coagulation/Ceramic Membrane Treatment of Yangtze River Water

by Shengji Xia, Xinran Zhang, Yuanchen Zhao, Fibor J. Tan, Pan Li and Yanling Liu

Membranes 2021, 11(5), 369; https://doi.org/10.3390/membranes11050369 - 19 May 2021

Cited by 2 | Viewed by 2372

Abstract

The membrane separation process is being widely used in water treatment. It is very important to control membrane fouling in the process of water treatment. This study was conducted to evaluate the efficiency of a pre-oxidation-coagulation flat ceramic membrane filtration process using different [...] Read more.

The membrane separation process is being widely used in water treatment. It is very important to control membrane fouling in the process of water treatment. This study was conducted to evaluate the efficiency of a pre-oxidation-coagulation flat ceramic membrane filtration process using different oxidant types and dosages in water treatment and membrane fouling control. The results showed that under suitable concentration conditions, the effect on membrane fouling control of a NaClO pre-oxidation combined with a coagulation/ceramic membrane system was better than that of an O₃ system. The oxidation process changed the structure of pollutants, reduced the pollution load and enhanced the coagulation process in a pre-oxidation-coagulation system as well. The influence of the oxidant on the filtration system was related to its oxidizability and other characteristics. NaClO and O₃ performed more efficiently than KMnO₄. NaClO was more conducive to the removal of DOC, and O₃ was more conducive to the removal of UV₂₅₄. Full article

(This article belongs to the Special Issue Water Treatment Process)

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37 pages, 2405 KiB

Open AccessEditor’s ChoiceReview

Prediction of Permeate Flux in Ultrafiltration Processes: A Review of Modeling Approaches

by Carolina Quezada, Humberto Estay, Alfredo Cassano, Elizabeth Troncoso and René Ruby-Figueroa

Membranes 2021, 11(5), 368; https://doi.org/10.3390/membranes11050368 - 18 May 2021

Cited by 22 | Viewed by 6556

Abstract

In any membrane filtration, the prediction of permeate flux is critical to calculate the membrane surface required, which is an essential parameter for scaling-up, equipment sizing, and cost determination. For this reason, several models based on phenomenological or theoretical derivation (such as gel-polarization, [...] Read more.

In any membrane filtration, the prediction of permeate flux is critical to calculate the membrane surface required, which is an essential parameter for scaling-up, equipment sizing, and cost determination. For this reason, several models based on phenomenological or theoretical derivation (such as gel-polarization, osmotic pressure, resistance-in-series, and fouling models) and non-phenomenological models have been developed and widely used to describe the limiting phenomena as well as to predict the permeate flux. In general, the development of models or their modifications is done for a particular synthetic model solution and membrane system that shows a good capacity of prediction. However, in more complex matrices, such as fruit juices, those models might not have the same performance. In this context, the present work shows a review of different phenomenological and non-phenomenological models for permeate flux prediction in UF, and a comparison, between selected models, of the permeate flux predictive capacity. Selected models were tested with data from our previous work reported for three fruit juices (bergamot, kiwi, and pomegranate) processed in a cross-flow system for 10 h. The validation of each selected model’s capacity of prediction was performed through a robust statistical examination, including a residual analysis. The results obtained, within the statistically validated models, showed that phenomenological models present a high variability of prediction (values of R-square in the range of 75.91–99.78%), Mean Absolute Percentage Error (MAPE) in the range of 3.14–51.69, and Root Mean Square Error (RMSE) in the range of 0.22–2.01 among the investigated juices. The non-phenomenological models showed a great capacity to predict permeate flux with R-squares higher than 97% and lower MAPE (0.25–2.03) and RMSE (3.74–28.91). Even though the estimated parameters have no physical meaning and do not shed light into the fundamental mechanistic principles that govern these processes, these results suggest that non-phenomenological models are a useful tool from a practical point of view to predict the permeate flux, under defined operating conditions, in membrane separation processes. However, the phenomenological models are still a proper tool for scaling-up and for an understanding the UF process. Full article

(This article belongs to the Special Issue Numerical Modelling in Membrane Processes)

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21 pages, 5063 KiB

Open AccessEditor’s ChoiceArticle

Study of Anion Exchange Membrane Properties Incorporating N-spirocyclic Quaternary Ammonium Cations and Aqueous Organic Redox Flow Battery Performance

by Misgina Tilahun Tsehaye, Xian Yang, Tobias Janoschka, Martin D. Hager, Ulrich S. Schubert, Fannie Alloin and Cristina Iojoiu

Membranes 2021, 11(5), 367; https://doi.org/10.3390/membranes11050367 - 18 May 2021

Cited by 12 | Viewed by 4511

Abstract

Flexible cross-linked anion exchange membranes (AEMs) based on poly (p-phenylene oxide) grafted with N-spirocyclic quaternary ammonium cations were synthesized via UV-induced free-radical polymerization by using diallylpiperidinium chloride as an ionic monomer. Five membranes with ion exchange capacity (IEC) varying between [...] Read more.

Flexible cross-linked anion exchange membranes (AEMs) based on poly (p-phenylene oxide) grafted with N-spirocyclic quaternary ammonium cations were synthesized via UV-induced free-radical polymerization by using diallylpiperidinium chloride as an ionic monomer. Five membranes with ion exchange capacity (IEC) varying between 1.5 to 2.8 mmol Cl⁻·g⁻¹ polymer were obtained and the correlation between IEC, water uptake, state of water in the membrane and ionic conductivity was studied. In the second part of this study, the influence of properties of four of these membranes on cell cycling stability and performance was investigated in an aqueous organic redox flow battery (AORFB) employing dimethyl viologen (MV) and N,N,N-2,2,6,6-heptamethylpiperidinyl oxy-4-ammonium chloride (TMA-TEMPO). The influence of membrane properties on cell cycling stability and performance was studied. At low-current density (20 mA·cm⁻²), the best capacity retention was obtained with lower IEC membranes for which the water uptake, freezable water and TMA-TEMPO and MV crossover are low. However, at a high current density (80 mA·cm⁻²), membrane resistance plays an important role and a membrane with moderate IEC, more precisely, moderate ion conductivity and water uptake was found to maintain the best overall cell performance. The results in this work contribute to the basic understanding of the relationship between membrane properties and cell performance, providing insights guiding the development of advanced membranes to improve the efficiency and power capability for AORFB systems. Full article

(This article belongs to the Section Membrane Analysis and Characterization)

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9 pages, 1229 KiB

Open AccessCommunication

The Impact of Chemical-Mechanical Ex Situ Aging on PFSA Membranes for Fuel Cells

by Mylène Robert, Assma El Kaddouri, Jean-Christophe Perrin, Kévin Mozet, Jérôme Dillet, Jean-Yves Morel and Olivier Lottin

Membranes 2021, 11(5), 366; https://doi.org/10.3390/membranes11050366 - 18 May 2021

Cited by 12 | Viewed by 2975

Abstract

A proton-exchange membrane fuel cell (PEMFC) constitutes today one of the preferred technologies to promote hydrogen-based alternative energies. However, the large-scale deployment of PEMFCs is still hampered by insufficient durability and reliability. In particular, the degradation of the polyelectrolyte membrane, caused by harsh [...] Read more.

A proton-exchange membrane fuel cell (PEMFC) constitutes today one of the preferred technologies to promote hydrogen-based alternative energies. However, the large-scale deployment of PEMFCs is still hampered by insufficient durability and reliability. In particular, the degradation of the polyelectrolyte membrane, caused by harsh mechanical and chemical stresses experienced during fuel cell operation, has been identified as one of the main factors restricting the PEMFC lifetime. An innovative chemical-mechanical ex situ aging device was developed to simultaneously expose the membrane to mechanical fatigue and an oxidizing environment (i.e., free radicals) in order to reproduce conditions close to those encountered in fuel cell systems. A cyclic compressive stress of 5 or 10 MPa was applied during several hours while a degrading solution (H₂O₂ or a Fenton solution) was circulated in contact with the membrane. The results demonstrated that both composite Nafion^™ XL and non-reinforced Nafion^™ NR211 membranes are significantly degraded by the conjoint mechanical and chemical stress exposure. The fluoride emission rate (FER) was generally slightly lower with XL than with NR211, which could be attributed to the degradation mitigation strategies developed for composite XL, except when the pressure level or the aging duration were increased, suggesting a limitation of the improved durability of XL. Full article

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

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15 pages, 3611 KiB

Open AccessArticle

Combined Effect of Activated Carbon Particles and Non-Adsorptive Spherical Beads as Fluidized Media on Fouling, Organic Removal and Microbial Communities in Anaerobic Membrane Bioreactor

by Daeeun Kwon, Theo Y.C. Lam, Minseok Kim, Giin-Yu Amy Tan, Po-Heng Lee and Jeonghwan Kim

Membranes 2021, 11(5), 365; https://doi.org/10.3390/membranes11050365 - 18 May 2021

Cited by 9 | Viewed by 2829

Abstract

The combined effect of acrylonitrile butadiene styrene (ABS) spherical beads and granular activated carbon (GAC) particles as fluidized media on the performance of anaerobic fluidized bed membrane bioreactor (AFMBR) was investigated. GAC particles and ABS beads were fluidized together in a single AFMBR [...] Read more.

The combined effect of acrylonitrile butadiene styrene (ABS) spherical beads and granular activated carbon (GAC) particles as fluidized media on the performance of anaerobic fluidized bed membrane bioreactor (AFMBR) was investigated. GAC particles and ABS beads were fluidized together in a single AFMBR to investigate membrane fouling and organic removal efficiency as well as energy consumption. The density difference between these two similarly sized media caused the stratified bed layer where ABS beads are fluidized above the GAC along the membrane. Membrane relaxation was effective to reduce the fouling and trans-membrane pressure (TMP) below 0.25 bar could be achieved at 6 h of hydraulic retention time (HRT). More than 90% of soluble chemical oxygen demand (SCOD) was removed after 80 d operation. Biogas consisting of 65% of methane was produced by AFMBR, suggesting that combined use of GAC and ABS beads did not have any adverse effect on methane production during the operational period. Scanning Electron Microscope (SEM) examinations showed the adherence of microbes to both media. However, 16S rRNA results revealed that fewer microbes attached to ABS beads than GAC. There were also compositional differences between the ABS and GAC microbial communities. The abundance of the syntrophs and exoelectrogens population on ABS beads was relatively low compared to that of GAC. Our result implied that syntrophic synergy and possible occurrence of direct interspecies electron transfer (DIET) might be facilitated in AFMBR by GAC, while traditional methanogenic pathways were dominant in ABS beads. The electrical energy required was 0.02 kWh/m³, and it was only about 13% of that produced by AFMBR. Full article

(This article belongs to the Special Issue Anaerobic Membrane Bioreactor for Wastewater Treatment)

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14 pages, 2040 KiB

Open AccessArticle

Liposomes Prevent In Vitro Hemolysis Induced by Streptolysin O and Lysenin

by Marcelo Ayllon, Gamid Abatchev, Andrew Bogard, Rosey Whiting, Sarah E. Hobdey and Daniel Fologea

Membranes 2021, 11(5), 364; https://doi.org/10.3390/membranes11050364 - 18 May 2021

Cited by 2 | Viewed by 3397

Abstract

The need for alternatives to antibiotics in the fight against infectious diseases has inspired scientists to focus on antivirulence factors instead of the microorganisms themselves. In this respect, prior work indicates that tiny, enclosed bilayer lipid membranes (liposomes) have the potential to compete [...] Read more.

The need for alternatives to antibiotics in the fight against infectious diseases has inspired scientists to focus on antivirulence factors instead of the microorganisms themselves. In this respect, prior work indicates that tiny, enclosed bilayer lipid membranes (liposomes) have the potential to compete with cellular targets for toxin binding, hence preventing their biological attack and aiding with their clearance. The effectiveness of liposomes as decoy targets depends on their availability in the host and how rapidly they are cleared from the circulation. Although liposome PEGylation may improve their circulation time, little is known about how such a modification influences their interactions with antivirulence factors. To fill this gap in knowledge, we investigated regular and long-circulating liposomes for their ability to prevent in vitro red blood cell hemolysis induced by two potent lytic toxins, lysenin and streptolysin O. Our explorations indicate that both regular and long-circulating liposomes are capable of similarly preventing lysis induced by streptolysin O. In contrast, PEGylation reduced the effectiveness against lysenin-induced hemolysis and altered binding dynamics. These results suggest that toxin removal by long-circulating liposomes is feasible, yet dependent on the particular virulence factor under scrutiny. Full article

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

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8 pages, 1376 KiB

Open AccessArticle

The Profound Influence of Lipid Composition on the Catalysis of the Drug Target NADH Type II Oxidoreductase

by Albert Godoy-Hernandez and Duncan G. G. McMillan

Membranes 2021, 11(5), 363; https://doi.org/10.3390/membranes11050363 - 17 May 2021

Cited by 2 | Viewed by 2378

Abstract

Lipids play a pivotal role in cellular respiration, providing the natural environment in which an oxidoreductase interacts with the quinone pool. To date, it is generally accepted that negatively charged lipids play a major role in the activity of quinone oxidoreductases. By changing [...] Read more.

Lipids play a pivotal role in cellular respiration, providing the natural environment in which an oxidoreductase interacts with the quinone pool. To date, it is generally accepted that negatively charged lipids play a major role in the activity of quinone oxidoreductases. By changing lipid compositions when assaying a type II NADH:quinone oxidoreductase, we demonstrate that phosphatidylethanolamine has an essential role in substrate binding and catalysis. We also reveal the importance of acyl chain composition, specifically c14:0, on membrane-bound quinone-mediated catalysis. This demonstrates that oxidoreductase lipid specificity is more diverse than originally thought and that the lipid environment plays an important role in the physiological catalysis of membrane-bound oxidoreductases. Full article

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

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19 pages, 8774 KiB

Open AccessArticle

Preparation of Ultrafiltration Membrane by Polyethylene Glycol Non-Covalent Functionalized Multi-Walled Carbon Nanotubes: Application for HA Removal and Fouling Control

by Yu Wang, Mengchan Dong, Xinya Xiong, Xiaoli Gai, Jia Zeng, Guirong Luan, Yufei Wang, Yaochen Wu and Jin Guo

Membranes 2021, 11(5), 362; https://doi.org/10.3390/membranes11050362 - 17 May 2021

Cited by 8 | Viewed by 3150

Abstract

Polyethylene glycol (PEG) non-covalent-functionalized multi-walled carbon nanotubes (MWCNT) membrane were prepared by vacuum filtration. The dispersion and stability of MWCNT non-covalent functionalized with PEG were all improved. TEM characterization and XPS quantitative analysis proved that the use of PEG to non-covalent functionalize MWCNT [...] Read more.

Polyethylene glycol (PEG) non-covalent-functionalized multi-walled carbon nanotubes (MWCNT) membrane were prepared by vacuum filtration. The dispersion and stability of MWCNT non-covalent functionalized with PEG were all improved. TEM characterization and XPS quantitative analysis proved that the use of PEG to non-covalent functionalize MWCNT was successful. SEM image analysis confirmed that the pore size of PEG–MWCNT membrane was more concentrated and distributed in a narrower range of diameter. Contact angle measurement demonstrated that PEG non-covalent functionalization greatly enhanced the hydrophilicity of MWCNT membranes. The results of pure water flux showed that the PEG–MWCNT membranes could be categorized into low pressure membrane. PEG-MWCNT membrane had a better effect on the removal of humic acid (HA) and a lower TMP growth rate compared with a commercial 0.01-μm PVDF ultrafiltration membrane. During the filtration of bovine serum albumin (BSA), the antifouling ability of PEG-MWCNT membranes were obviously better than the raw MWCNT membranes. The TMP recovery rate of PEG–MWCNT membrane after cross flushing was 79.4%, while that of raw MWCNT–_COOH and MWCNT membrane were only 14.9% and 28.3%, respectively. PEG non-covalent functionalization improved the antifouling ability of the raw MWCNT membranes and reduced the irreversible fouling, which effectively prolonged the service life of MWCNT membrane. Full article

(This article belongs to the Special Issue Membrane Fouling Control in Water Treatment)

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17 pages, 9172 KiB

Open AccessArticle

Antifouling Polyethersulfone-Petrol Soot Nanoparticles Composite Ultrafiltration Membrane for Dye Removal in Wastewater

by Nkechi P. Nwafor, Richard M. Moutloali, Keneiloe Sikhwivhilu, Oluwole B. Familoni and Luqman A. Adams

Membranes 2021, 11(5), 361; https://doi.org/10.3390/membranes11050361 - 15 May 2021

Cited by 6 | Viewed by 2292

Abstract

Engineered nanoparticles are known to boost membrane performance in membrane technology. Hitherto, tunable properties that lead to improved hydrophilicity due to increased surface oxygen functionalities upon oxidation of petrol soot have not been fully exploited in membrane filtration technology. Herein, the integration of [...] Read more.

Engineered nanoparticles are known to boost membrane performance in membrane technology. Hitherto, tunable properties that lead to improved hydrophilicity due to increased surface oxygen functionalities upon oxidation of petrol soot have not been fully exploited in membrane filtration technology. Herein, the integration of oxidized petrol soot nanoparticles (PSN) into polyethersulfone ultrafiltration membranes produced via phase inversion technique for dye removal in wastewater is reported. The nanoparticles, as well as the composite membranes, were characterized with diverse physicochemical methods, particularly TEM, SEM, BET, AFM, contact angle, etc. The effect of varying the ratio of PSN (0.05–1.0 wt %) on the properties of the composite membrane was evaluated. The composite membranes displayed increased hydrophilicity, enhanced pure water flux, and antifouling properties relative to the pristine membrane. For example, the obtained pure water flux increased from 130 L·m⁻²·h⁻¹ for base membrane to 265 L·m⁻²·h⁻¹ for the best composite membrane (M4). The best flux recovery ratio (FRR) observed for the membranes containing PSN was ca. 80% in contrast to 49% obtained with the pristine membrane indicative of the positive influence of PSN on membrane antifouling behavior. Furthermore, the PSN composite membranes displayed relatively selective anionic dye rejection of ˃95% for Congo red and between 50–71% for methyl orange compared with 42–96% rejection obtained for cationic methylene blue dye with increasing PSN content. The successful fabrication of polyethersulfone–PSN composite membranes by a simple blending process opens a novel route for the preparation of economical, functional, and scalable water purification membranes capable of addressing the complex issue of water remediation of organic azo dyes. Full article

(This article belongs to the Section Polymeric Membranes)

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16 pages, 4699 KiB

Open AccessArticle

Production Strategies of TiN_x Coatings via Reactive High Power Impulse Magnetron Sputtering for Selective H₂ Separation

by Cecilia Mortalò, Silvia Maria Deambrosis, Francesco Montagner, Valentina Zin, Monica Fabrizio, Luca Pasquali, Raffaella Capelli, Monica Montecchi and Enrico Miorin

Membranes 2021, 11(5), 360; https://doi.org/10.3390/membranes11050360 - 15 May 2021

Cited by 3 | Viewed by 2253

Abstract

This scientific work aims to optimize the preparation of titanium nitride coatings for selective H₂ separation using the Reactive High Power Impulse Magnetron Sputtering technology (RHiPIMS). Currently, nitride-based thin films are considered promising membranes for hydrogen. The first series of TiN_x [...] Read more.

This scientific work aims to optimize the preparation of titanium nitride coatings for selective H₂ separation using the Reactive High Power Impulse Magnetron Sputtering technology (RHiPIMS). Currently, nitride-based thin films are considered promising membranes for hydrogen. The first series of TiN_x/Si test samples were developed while changing the reactive gas percentage (N₂%) during the process. Obtained coatings were extensively characterized in terms of morphology, composition, and microstructure. A 500 nm thick, dense TiN_x coating was then deposited on a porous alumina substrate and widely investigated. Moreover, the as-prepared TiN_x films were heat-treated in an atmosphere containing hydrogen in order to prove their chemical and structural stability; which revealed to be promising. This study highlighted how the RHiPIMS method permits fine control of the grown layer’s stoichiometry and microstructure. Moreover, it pointed out the need for a protective layer to prevent surface oxidation of the nitride membrane by air and the necessity to deepen the study of TiN_x/alumina interface in order to improve film/substrate adhesion. Full article

(This article belongs to the Special Issue Characterization of Ceramic Membranes)

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11 pages, 2222 KiB

Open AccessCommunication

Investigating the Proton and Ion Transfer Properties of Supported Ionic Liquid Membranes Prepared for Bioelectrochemical Applications Using Hydrophobic Imidazolium-Type Ionic Liquids

by László Koók, Piroska Lajtai-Szabó, Péter Bakonyi, Katalin Bélafi-Bakó and Nándor Nemestóthy

Membranes 2021, 11(5), 359; https://doi.org/10.3390/membranes11050359 - 14 May 2021

Cited by 2 | Viewed by 2335

Abstract

Hydrophobic ionic liquids (IL) may offer a special electrolyte in the form of supported ionic liquid membranes (SILM) for microbial fuel cells (MFC) due to their advantageous mass transfer characteristics. In this work, the proton and ion transfer properties of SILMs made with [...] Read more.

Hydrophobic ionic liquids (IL) may offer a special electrolyte in the form of supported ionic liquid membranes (SILM) for microbial fuel cells (MFC) due to their advantageous mass transfer characteristics. In this work, the proton and ion transfer properties of SILMs made with IL containing imidazolium cation and [PF₆]⁻ and [NTf₂]⁻ anions were studied and compared to Nafion. It resulted that both ILs show better proton mass transfer and diffusion coefficient than Nafion. The data implied the presence of water microclusters permeating through [hmim][PF₆]-SILM to assist the proton transfer. This mechanism could not be assumed in the case of [NTf₂]⁻ containing IL. Ion transport numbers of K⁺, Na⁺, and H⁺ showed that the IL with [PF₆]⁻ anion could be beneficial in terms of reducing ion transfer losses in MFCs. Moreover, the conductivity of [bmim][PF₆]-SILM at low electrolyte concentration (such as in MFCs) was comparable to Nafion. Full article

(This article belongs to the Section Membrane Applications)

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16 pages, 2415 KiB

Open AccessReview

Donnan Membrane Process for the Selective Recovery and Removal of Target Metal Ions—A Mini Review

by Dennis Asante-Sackey, Sudesh Rathilal, Emmanuel Kweinor Tetteh, Elorm Obotey Ezugbe and Lingham V. Pillay

Membranes 2021, 11(5), 358; https://doi.org/10.3390/membranes11050358 - 14 May 2021

Cited by 21 | Viewed by 4321

Abstract

Membrane-based water purification technologies contribute significantly to water settings, where it is imperative to use low-cost energy sources to make the process economically and technically competitive for large-scale applications. Donnan membrane processes (DMPs) are driven by a potential gradient across an ion exchange [...] Read more.

Membrane-based water purification technologies contribute significantly to water settings, where it is imperative to use low-cost energy sources to make the process economically and technically competitive for large-scale applications. Donnan membrane processes (DMPs) are driven by a potential gradient across an ion exchange membrane and have an advantage over fouling in conventional pressure driven membrane technologies, which are gaining attention. DMP is a removal, recovery and recycling technology that is commonly used for separation, purification and the concentrating of metals in different water and waste streams. In this study, the principle and application of DMP for sustainable wastewater treatment and prospects of chemical remediation are reviewed and discussed. In addition, the separation of dissolved metal ions in wastewater settings without the use of pressure driven gradients or external energy supply membrane technologies is highlighted. Furthermore, DMP distinctive configurations and operational factors are explored and the prospects of integrating them into the wastewater treatment plants are recommended. Full article

(This article belongs to the Special Issue Membrane Technology for the Removal of Organic Micropollutants and Emerging Pollutants)

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18 pages, 6520 KiB

Open AccessArticle

Effect of the Agglomerate Geometry on the Effective Electrical Conductivity of a Porous Electrode

by Abimael Rodriguez, Roger Pool, Jaime Ortegon, Beatriz Escobar and Romeli Barbosa

Membranes 2021, 11(5), 357; https://doi.org/10.3390/membranes11050357 - 14 May 2021

Cited by 2 | Viewed by 2696

Abstract

The study of the microstructure of random heterogeneous materials, related to an electrochemical device, is relevant because their effective macroscopic properties, e.g., electrical or proton conductivity, are a function of their effective transport coefficients (ETC). The magnitude of ETC depends on the distribution [...] Read more.

The study of the microstructure of random heterogeneous materials, related to an electrochemical device, is relevant because their effective macroscopic properties, e.g., electrical or proton conductivity, are a function of their effective transport coefficients (ETC). The magnitude of ETC depends on the distribution and properties of the material phase. In this work, an algorithm is developed to generate stochastic two-phase (binary) image configurations with multiple geometries and polydispersed particle sizes. The recognizable geometry in the images is represented by the white phase dispersed and characterized by statistical descriptors (two-point and line-path correlation functions). Percolation is obtained for the geometries by identifying an infinite cluster to guarantee the connection between the edges of the microstructures. Finally, the finite volume method is used to determine the ETC. Agglomerate phase results show that the geometry with the highest local current distribution is the triangular geometry. In the matrix phase, the most significant results are obtained by circular geometry, while the lowest is obtained by the 3-sided polygon. The proposed methodology allows to establish criteria based on percolation and surface fraction to assure effective electrical conduction according to their geometric distribution; results provide an insight for the microstructure development with high projection to be used to improve the electrode of a Membrane Electrode Assembly (MEA). Full article

(This article belongs to the Special Issue Advanced Membrane Electrode Assembly (MEA) for Applications in Fuel Cell and Electrolyzer Based Systems)

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23 pages, 9467 KiB

Open AccessArticle

Water as a Blood Model for Determination of CO₂ Removal Performance of Membrane Oxygenators

by Benjamin Lukitsch, Raffael Koller, Paul Ecker, Martin Elenkov, Christoph Janeczek, Markus Pekovits, Bahram Haddadi, Christian Jordan, Margit Gfoehler and Michael Harasek

Membranes 2021, 11(5), 356; https://doi.org/10.3390/membranes11050356 - 12 May 2021

Cited by 1 | Viewed by 3014

Abstract

CO₂ removal via membrane oxygenators has become an important and reliable clinical technique. Nevertheless, oxygenators must be further optimized to increase CO₂ removal performance and to reduce severe side effects. Here, in vitro tests with water can significantly reduce costs and [...] Read more.

CO₂ removal via membrane oxygenators has become an important and reliable clinical technique. Nevertheless, oxygenators must be further optimized to increase CO₂ removal performance and to reduce severe side effects. Here, in vitro tests with water can significantly reduce costs and effort during development. However, they must be able to reasonably represent the CO₂ removal performance observed with blood. In this study, the deviation between the CO₂ removal rate determined in vivo with porcine blood from that determined in vitro with water is quantified. The magnitude of this deviation (approx. 10%) is consistent with results reported in the literature. To better understand the remaining difference in CO₂ removal rate and in order to assess the application limits of in vitro water tests, CFD simulations were conducted. They allow to quantify and investigate the influences of the differing fluid properties of blood and water on the CO₂ removal rate. The CFD results indicate that the main CO₂ transport resistance, the diffusional boundary layer, behaves generally differently in blood and water. Hence, studies of the CO₂ boundary layer should be preferably conducted with blood. In contrast, water tests can be considered suitable for reliable determination of the total CO₂ removal performance of oxygenators. Full article

(This article belongs to the Special Issue Numerical Modelling in Membrane Processes)

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14 pages, 5215 KiB

Open AccessArticle

OH⁻ and H₃O⁺ Diffusion in Model AEMs and PEMs at Low Hydration: Insights from Ab Initio Molecular Dynamics

by Tamar Zelovich and Mark E. Tuckerman

Membranes 2021, 11(5), 355; https://doi.org/10.3390/membranes11050355 - 12 May 2021

Cited by 12 | Viewed by 3714

Abstract

Fuel cell-based anion-exchange membranes (AEMs) and proton exchange membranes (PEMs) are considered to have great potential as cost-effective, clean energy conversion devices. However, a fundamental atomistic understanding of the hydroxide and hydronium diffusion mechanisms in the AEM and PEM environment is an ongoing [...] Read more.

Fuel cell-based anion-exchange membranes (AEMs) and proton exchange membranes (PEMs) are considered to have great potential as cost-effective, clean energy conversion devices. However, a fundamental atomistic understanding of the hydroxide and hydronium diffusion mechanisms in the AEM and PEM environment is an ongoing challenge. In this work, we aim to identify the fundamental atomistic steps governing hydroxide and hydronium transport phenomena. The motivation of this work lies in the fact that elucidating the key design differences between the hydroxide and hydronium diffusion mechanisms will play an important role in the discovery and determination of key design principles for the synthesis of new membrane materials with high ion conductivity for use in emerging fuel cell technologies. To this end, ab initio molecular dynamics simulations are presented to explore hydroxide and hydronium ion solvation complexes and diffusion mechanisms in the model AEM and PEM systems at low hydration in confined environments. We find that hydroxide diffusion in AEMs is mostly vehicular, while hydronium diffusion in model PEMs is structural. Furthermore, we find that the region between each pair of cations in AEMs creates a bottleneck for hydroxide diffusion, leading to a suppression of diffusivity, while the anions in PEMs become active participants in the hydronium diffusion, suggesting that the presence of the anions in model PEMs could potentially promote hydronium diffusion. Full article

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

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12 pages, 1015 KiB

Open AccessArticle

Clarification Processes of Orange Prickly Pear Juice (Opuntia spp.) by Microfiltration

by Jaime A. Arboleda Mejia and Jorge Yáñez-Fernandez

Membranes 2021, 11(5), 354; https://doi.org/10.3390/membranes11050354 - 12 May 2021

Cited by 10 | Viewed by 2504

Abstract

In this study, fresh orange prickly pear juice (Opuntia spp.) was clarified by a cross-flow microfiltration (MF) process on a laboratory scale. The viability of the process—in terms of productivity (permeate flux of 77.80 L/h) and the rejection of selected membranes towards [...] Read more.

In this study, fresh orange prickly pear juice (Opuntia spp.) was clarified by a cross-flow microfiltration (MF) process on a laboratory scale. The viability of the process—in terms of productivity (permeate flux of 77.80 L/h) and the rejection of selected membranes towards specific compounds—was analyzed. The quality of the clarified juice was also analyzed for total antioxidants (TEAC), betalains content (mg/100 g wet base), turbidity (NTU) and colorimetry parameters (L, a*, b*, Croma and H). The MF process permitted an excellent level of clarification, reducing the suspended solids and turbidity of the fresh juice. In the clarified juice, a decrease in total antioxidants (2.03 TEAC) and betalains content (4.54 mg/100 g wet basis) was observed as compared to the fresh juice. Furthermore, there were significant changes in color properties due to the effects of the L, a*, b*, C and h° values after removal of turbidity of the juice. The turbidity also decreased (from 164.33 to 0.37 NTU). Full article

(This article belongs to the Special Issue Advances on Bio-Based Materials for Food Packaging Applications)

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13 pages, 3772 KiB

Open AccessArticle

Analysis of Concentration Polarisation in Full-Size Spiral Wound Reverse Osmosis Membranes Using Computational Fluid Dynamics

by Wenshu Wei, Xiang Zou, Xinxiang Ji, Rulin Zhou, Kangkang Zhao and Yuan Wang

Membranes 2021, 11(5), 353; https://doi.org/10.3390/membranes11050353 - 10 May 2021

Cited by 12 | Viewed by 3954

Abstract

A three-dimensional model for the simulation of concentration polarisation in a full-scale spiral wound reverse osmosis (RO) membrane element was developed. The model considered the coupled effect of complex spacer geometry, pressure drop and membrane filtration. The simulated results showed that, at a [...] Read more.

A three-dimensional model for the simulation of concentration polarisation in a full-scale spiral wound reverse osmosis (RO) membrane element was developed. The model considered the coupled effect of complex spacer geometry, pressure drop and membrane filtration. The simulated results showed that, at a salt concentration of 10,000 mg/L and feed pressure of 10.91 bar, permeate flux decreased from 27.6 L/(m² h) (LMH) at the module inlet to 24.1 LMH at the module outlet as a result of salt accumulation in the absence of a feed spacer. In contrast, the presence of the spacer increased pressure loss along the membranes, and its presence created vortices and enhanced fluid velocity at the boundary layer and led to a minor decrease in flux to 26.5 LMH at the outlet. This paper underpins the importance of the feed spacer’s role in mitigating concentration polarisation in full-scale spiral wound modules. The model can be used by both the industry and by academia for improved understanding and accurate presentation of mass transfer phenomena of full-scale RO modules by different commercial manufacturers that cannot be achieved by experimental characterization of the mass transfer coefficient or by CFD modelling of simplified 2D flow channels. Full article

(This article belongs to the Special Issue State-of-the-Art Membrane Science and Technology in Australasia)

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14 pages, 3203 KiB

Open AccessArticle

Effect of F16-Betulin Conjugate on Mitochondrial Membranes and Its Role in Cell Death Initiation

by Mikhail V. Dubinin, Alena A. Semenova, Darya A. Nedopekina, Eldar V. Davletshin, Anna Yu. Spivak and Konstantin N. Belosludtsev

Membranes 2021, 11(5), 352; https://doi.org/10.3390/membranes11050352 - 10 May 2021

Cited by 21 | Viewed by 2599

Abstract

This work demonstrates the effects of a newly synthesized conjugate of the plant triterpenoid betulin and the penetrating cation F16 used for mitochondrial targeting. The resulting F16-betulin conjugate revealed a mitochondria-targeted effect, decreasing the mitochondrial potential and inducing superoxide overproduction in rat thymocytes [...] Read more.

This work demonstrates the effects of a newly synthesized conjugate of the plant triterpenoid betulin and the penetrating cation F16 used for mitochondrial targeting. The resulting F16-betulin conjugate revealed a mitochondria-targeted effect, decreasing the mitochondrial potential and inducing superoxide overproduction in rat thymocytes in vitro. It has been suggested that this may cause the cytotoxic effect of the conjugate, which significantly exceeds the effectiveness of its precursors, betulin and F16. Using isolated rat liver mitochondria, we found that the F16-betulin conjugate has a surface-active effect on mitochondrial membranes, causing organelle aggregation. This effect of the derivative resulted in a dose-dependent decrease in mitochondrial transmembrane potential, as well as suppression of respiration and oxidative phosphorylation, especially in the case of nicotinamide adenine dinucleotide (NAD)-fueled organelles. In addition, the F16-betulin conjugate caused an increase in H₂O₂ generation by mitochondria fueled with glutamate and malate. These effects of the derivative can presumably be due to the powerful suppression of the redox activity of complex I of the mitochondrial electron transport chain. The paper discusses how the mitochondria-targeted effects of the F16-betulin conjugate may be related to its cytotoxic effects. Full article

(This article belongs to the Special Issue Recent Developments in Membrane Biology)

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15 pages, 41336 KiB

Open AccessArticle

Cation Exchange Membranes Coated with Polyethyleneimine and Crown Ether to Improve Monovalent Cation Electrodialytic Selectivity

by Shanshan Yang, Shuaijun Yu, Lu Yu, Yuanwei Liu, Junbin Liao, Jiangnan Shen and Congjie Gao

Membranes 2021, 11(5), 351; https://doi.org/10.3390/membranes11050351 - 10 May 2021

Cited by 8 | Viewed by 3407

Abstract

Developing monovalent cation permselective membranes (MCPMs) with high-efficient permselectivity is the core concern in specific industrial applications. In this work, we have fabricated a series of novel cation exchange membranes (CEMs) based on sulfonated polysulfone (SPSF) surface modification by polyethyleneimine (PEI) and 4′-aminobenzo-12-crown-4 [...] Read more.

Developing monovalent cation permselective membranes (MCPMs) with high-efficient permselectivity is the core concern in specific industrial applications. In this work, we have fabricated a series of novel cation exchange membranes (CEMs) based on sulfonated polysulfone (SPSF) surface modification by polyethyleneimine (PEI) and 4′-aminobenzo-12-crown-4 (12C4) codeposited with dopamine (DA) successively, which was followed by the cross-linking of glutaraldehyde (GA). The as-prepared membranes before and after modification were systematically characterized with regard to their structures as well as their physicochemical and electrochemical properties. Particularly, the codeposition sequence of modified ingredients was investigated on galvanostatic permselectivity to cations. The modified membrane (M-12C4-0.50-PEI) exhibits significantly prominent selectivity to Li⁺ ions (

P_{{Mg}^{2 +}}^{{Li}^{+}}

= 5.23) and K⁺ ions (

P_{{Mg}^{2 +}}^{K^{+}}

= 13.56) in Li⁺/Mg²⁺ and K⁺/Mg²⁺ systems in electrodialysis (ED), which is far superior to the pristine membrane (M-0,

P_{{Mg}^{2 +}}^{{Li}^{+}}

= 0.46,

P_{{Mg}^{2 +}}^{K^{+}}

= 1.23) at a constant current density of 5.0 mA·cm⁻². It possibly arises from the synergistic effects of electrostatic repulsion (positively charged PEI), pore-size sieving (distribution of modified ingredients), and specific interaction effect (12C4 ~Li⁺). This facile strategy may provide new insights into developing selective CEMs in the separation of specific cations by ED. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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11 pages, 43276 KiB

Open AccessArticle

Organic Nanobowls Modified Thin Film Composite Membrane for Enhanced Purification Performance toward Different Water Resources

by Changjin Ou, Sisi Li, Zhongyi Wang, Juan Qin, Qian Wang, Zhipeng Liao and Jiansheng Li

Membranes 2021, 11(5), 350; https://doi.org/10.3390/membranes11050350 - 10 May 2021

Cited by 12 | Viewed by 2496

Abstract

The structure and composition of nanofillers have a significant influence on polyamide nanofiltration (NF) membranes. In this work, an asymmetric organic nanobowl containing a concave cavity was synthesized and incorporated into a polyamide layer to prepare thin film nanocomposite (TFN) membranes via an [...] Read more.

The structure and composition of nanofillers have a significant influence on polyamide nanofiltration (NF) membranes. In this work, an asymmetric organic nanobowl containing a concave cavity was synthesized and incorporated into a polyamide layer to prepare thin film nanocomposite (TFN) membranes via an interfacial polymerization process. Benefiting from the hydrophilicity, hollow cavity and charge property of the compatible organic nanobowls, the separation performance of the developed TFN membrane was significantly improved. The corresponding water fluxes increased to 119.44 ± 5.56, 141.82 ± 3.24 and 130.27 ± 2.05 L/(m²·h) toward Na₂SO₄, MgCl₂ and NaCl solutions, respectively, with higher rejections, compared with the control thin film composite (TFC) and commercial (CM) membranes. Besides this, the modified TFN membrane presented a satisfying purification performance toward tap water, municipal effluent and heavy metal wastewater. More importantly, a better antifouling property of the TFN membrane than TFC and CM membranes was achieved with the assistance of organic nanobowls. These results indicate that the separation performance of the TFN membrane can be elevated by the incorporation of organic nanobowls. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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19 pages, 4978 KiB

Open AccessArticle

Dynamic Modeling of Fouling in Reverse Osmosis Membranes

by Bowen Ling, Peng Xie, David Ladner and Ilenia Battiato

Membranes 2021, 11(5), 349; https://doi.org/10.3390/membranes11050349 - 10 May 2021

Cited by 13 | Viewed by 3275

Abstract

During reverse osmosis (RO) membrane filtration, performance is dramatically affected by fouling, which concurrently decreases the permeate flux while increasing the energy required to operate the system. Comprehensive design and optimization of RO systems are best served by an understanding of the coupling [...] Read more.

During reverse osmosis (RO) membrane filtration, performance is dramatically affected by fouling, which concurrently decreases the permeate flux while increasing the energy required to operate the system. Comprehensive design and optimization of RO systems are best served by an understanding of the coupling between membrane shape, local flow field, and fouling; however, current studies focus exclusively on simplified steady-state models that ignore the dynamic coupling between fluid flow, solute transport, and foulant accumulation. We developed a customized solver (SUMs: Stanford University Membrane Solver) under the open source finite volume simulator OpenFOAM to solve transient Navier–Stokes, advection–diffusion, and adsorption–desorption equations for foulant accumulation. We implemented two permeate flux reduction models at the membrane boundary: the resistance-in-series (RIS) model and the effective-pressure-drop (EPD) model. The two models were validated against filtration experiments by comparing the equilibrium flux, pressure drop, and fouling pattern on the membrane. Both models not only predict macroscopic quantities (e.g., permeate flux and pressure drop) but also the fouling pattern developed on the membrane, with a good match with experimental results. Furthermore, the models capture the temporal evolution of foulant accumulation and its coupling with flux reduction. Full article

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

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10 pages, 711 KiB

Open AccessArticle

Development of Ammonia Selectively Permeable Zeolite Membrane for Sensor in Sewer System

by Hisao Inami, Chie Abe and Yasuhisa Hasegawa

Membranes 2021, 11(5), 348; https://doi.org/10.3390/membranes11050348 - 10 May 2021

Cited by 9 | Viewed by 2771

Abstract

Ammonia (NH₃) and hydrogen sulfide (H₂S) are hazardous and odorous gases. A special device that is not affected by other gases is necessary so that it can detect such gases. Zeolite membranes can separate the desired component selectively by [...] Read more.

Ammonia (NH₃) and hydrogen sulfide (H₂S) are hazardous and odorous gases. A special device that is not affected by other gases is necessary so that it can detect such gases. Zeolite membranes can separate the desired component selectively by molecular sieving and selective adsorption. LTA-, MFI-, and FAU-type zeolite membranes were prepared in this study, and the permeation and separation performances were determined for the ternary mixture of NH₃, H₂S, and N₂ to develop an NH₃ selectively permeable membrane. Although the separation factors of NH₃ were high enough for the LTA-type zeolite membrane, the NH₃ permeance was the lowest among the three membranes. In contrast, the FAU-type zeolite membrane with Si/Al = 1.35 showed a high enough NH₃ permeance and a NH₃/N₂ separation factor. The membrane modification and varying the membrane composition were carried out to reduce the H₂S permeance. As a result, the H₂S permeance could be decreased by modification with silane coupling agents, and a separation factor of NH₃ toward H₂S of over 3000 was achieved. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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13 pages, 9073 KiB

Open AccessArticle

Influence of Organic Solvent Species on Dehydration Behaviors of NaA-Type Zeolite Membrane

by Yasuhisa Hasegawa, Wakako Matsuura, Chie Abe and Ayumi Ikeda

Membranes 2021, 11(5), 347; https://doi.org/10.3390/membranes11050347 - 10 May 2021

Cited by 10 | Viewed by 2621

Abstract

In this study, an NaA-type zeolite membrane was prepared, and the dehydration performances of the membrane were determined by the pervaporation for several organic solvents to understand the lower dehydration performances of zeolite membranes for NMP solutions than those for alcohols. For a [...] Read more.

In this study, an NaA-type zeolite membrane was prepared, and the dehydration performances of the membrane were determined by the pervaporation for several organic solvents to understand the lower dehydration performances of zeolite membranes for NMP solutions than those for alcohols. For a 90 wt% ethanol solution at 348 K, the permeation flux and separation factor of the membrane were 3.82 kg m⁻² h⁻¹ and 73,800, respectively. The high dehydration performances were also obtained for alcohols and low boiling solvents (acetonitrile, acetone, methyl ethyl ketone (MEK) and tetrahydrofuran (THF)). However, the permeation flux and separation factors decreased significantly for high boiling solvents, such as N,N-dimethylacetamide (DMA), N,N-dimethyl formamide (DMF), dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP). The influences of the water content and temperature on the dehydration performances for the NMP solutions were determined to understand the lower dehydration performances for those solvents. Those results suggest that the lower dehydration performances for the high boiling solvents were attributed to the lower vapor pressures of water and the higher permeances of those solvents. Furthermore, this study proposes that the permeation behaviors through zeolite membranes could be understood by the determination of the effect of temperature on the permeance of individual components. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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21 pages, 3980 KiB

Open AccessEditor’s ChoiceReview

Peripheral Membrane Proteins: Promising Therapeutic Targets across Domains of Life

by Deborah M. Boes, Albert Godoy-Hernandez and Duncan G. G. McMillan

Membranes 2021, 11(5), 346; https://doi.org/10.3390/membranes11050346 - 08 May 2021

Cited by 27 | Viewed by 6616

Abstract

Membrane proteins can be classified into two main categories—integral and peripheral membrane proteins—depending on the nature of their membrane interaction. Peripheral membrane proteins are highly unique amphipathic proteins that interact with the membrane indirectly, using electrostatic or hydrophobic interactions, or directly, using hydrophobic [...] Read more.

Membrane proteins can be classified into two main categories—integral and peripheral membrane proteins—depending on the nature of their membrane interaction. Peripheral membrane proteins are highly unique amphipathic proteins that interact with the membrane indirectly, using electrostatic or hydrophobic interactions, or directly, using hydrophobic tails or GPI-anchors. The nature of this interaction not only influences the location of the protein in the cell, but also the function. In addition to their unique relationship with the cell membrane, peripheral membrane proteins often play a key role in the development of human diseases such as African sleeping sickness, cancer, and atherosclerosis. This review will discuss the membrane interaction and role of periplasmic nitrate reductase, CymA, cytochrome c, alkaline phosphatase, ecto-5’-nucleotidase, acetylcholinesterase, alternative oxidase, type-II NADH dehydrogenase, and dihydroorotate dehydrogenase in certain diseases. The study of these proteins will give new insights into their function and structure, and may ultimately lead to ground-breaking advances in the treatment of severe diseases. Full article

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

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