Membranes

14 pages, 45644 KiB

Open AccessArticle

Fluid-Structure Interaction Analysis on Membrane Behavior of a Microfluidic Passive Valve

by Zhen-hao Lin, Xiao-juan Li, Zhi-jiang Jin and Jin-yuan Qian

Membranes 2020, 10(10), 300; https://doi.org/10.3390/membranes10100300 - 21 Oct 2020

Cited by 10 | Viewed by 3233

In this paper, the effect of membrane features on flow characteristics in the microfluidic passive valve (MPV) and the membrane behavior against fluid flow are studied using the fluid-structure interaction (FSI) analysis. Firstly, the microvalve model with different numbers of microholes and pitches [...] Read more.

In this paper, the effect of membrane features on flow characteristics in the microfluidic passive valve (MPV) and the membrane behavior against fluid flow are studied using the fluid-structure interaction (FSI) analysis. Firstly, the microvalve model with different numbers of microholes and pitches of microholes are designed to investigate the flow rate of the MPV. The result shows that the number of microholes on the membrane has a significant impact on the flow rate of the MPV, while the pitch of microholes has little effect on it. The constant flow rate maintained by the microvalve (the number of microholes n = 4) is 5.75 mL/min, and the threshold pressure to achieve the flow rate is 4 kPa. Secondly, the behavior of the membrane against the fluid flow is analyzed. The result shows that as the inlet pressure increases, the flow resistance of the MPV increases rapidly, and the deformation of the membrane gradually becomes stable. Finally, the effect of the membrane material on the flow rate and the deformation of the membrane are studied. The result shows that changes in the material properties of the membrane cause a decrease in the amount of deformation in all stages the all positions of the membrane. This work may provide valuable guidance for the optimization of microfluidic passive valve in microfluidic system. Full article

(This article belongs to the Special Issue Microfluidics and MEMS Technology for Membranes)

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32 pages, 1194 KiB

Open AccessReview

Regulation of Cell Death by Mitochondrial Transport Systems of Calcium and Bcl-2 Proteins

by Natalia Naumova and Radek Šachl

Membranes 2020, 10(10), 299; https://doi.org/10.3390/membranes10100299 - 21 Oct 2020

Cited by 27 | Viewed by 5394

Abstract

Mitochondria represent the fundamental system for cellular energy metabolism, by not only supplying energy in the form of ATP, but also by affecting physiology and cell death via the regulation of calcium homeostasis and the activity of Bcl-2 proteins. A lot of research [...] Read more.

Mitochondria represent the fundamental system for cellular energy metabolism, by not only supplying energy in the form of ATP, but also by affecting physiology and cell death via the regulation of calcium homeostasis and the activity of Bcl-2 proteins. A lot of research has recently been devoted to understanding the interplay between Bcl-2 proteins, the regulation of these interactions within the cell, and how these interactions lead to the changes in calcium homeostasis. However, the role of Bcl-2 proteins in the mediation of mitochondrial calcium homeostasis, and therefore the induction of cell death pathways, remain underestimated and are still not well understood. In this review, we first summarize our knowledge about calcium transport systems in mitochondria, which, when miss-regulated, can induce necrosis. We continue by reviewing and analyzing the functions of Bcl-2 proteins in apoptosis. Finally, we link these two regulatory mechanisms together, exploring the interactions between the mitochondrial Ca²⁺ transport systems and Bcl-2 proteins, both capable of inducing cell death, with the potential to determine the cell death pathway—either the apoptotic or the necrotic one. Full article

(This article belongs to the Special Issue Membrane Channels and Transporters)

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Schematic presentation of Ca2+ transport systems in mitochondria. (1) Ca2+ influx and efflux through the outer mitochondrial membrane (OMM) driven via the voltage-dependent anion channel (VDAC). (2) Ca2+ influx through the inner mitochondrial membrane (IMM) driven by three major transport systems: (i) mitochondrial Ca2+ uniporter (MCU), (ii) mitochondrial ryanodine receptor (mRyR), (iii) rapid mode of Ca2+ uptake (RaM) and one mitochondrial system under debate: (iv) leucine zipper- EF-hand containing transmembrane protein (LETM1). Ca2+ influx through the MCU is established by the electrochemical gradient created by the electron transport chain (ETC). (3) Ca2+ efflux through the IMM driven by three other major transport systems: (i) Na+/Ca2+/Li+ (NCLX) exchanger, (ii) H+/Ca2+ exchanger (HCX), (iii) mitochondrial permeability transition pore complex (mPTPC) and one mitochondrial system under debate: (iv) leucine zipper- EF-hand containing transmembrane protein (LETM1). (4) The core constituents of mPTPC include: the adenine nucleotide translocase (ANT), matrix cyclophilin D (CypD) and phosphate carrier (PiC), which serve as pore regulators, and the pro-apoptotic proteins Bax and Bak, which can induce mitochondrial swelling and rupture during the mPTP opening. ATP-synthase is the key IMM-pore forming unit of mPTPC. Full article ">Figure 2
Classification of Bcl-2 of proteins based on their apoptotic activity. (A) anti-apoptotic; (B) pro-apoptotic; and (C) apoptotic mediators of the Bcl-2 family proteins containing one BH-3 domain. Full article ">Figure 3
Bcl-2 proteins and mitochondrial Ca2+ transport systems determine the necrotic or apoptotic cell death pathways. mPTP-mediated necrosis and MOMP-mediated apoptosis are initiated by various extracellular and intracellular cell death stimuli. Central events for cell death rely on interactions between “activators” and “sensitizers” BH3-only proteins (these proteins are marked by dark blue). Activators (BID, BIM, PUMA, NOXA) bind and activate Bax and Bak and induce a series of their conformational changes and subsequent oligomerization within the OMM, finally resulting in MOMP. Sensitizers (BAD, BIK, BMF, HRK) bind the pro-survival Bcl-2 proteins (Bcl-2, Bcl-XL, Mcl-1) and release them to activate Bax and Bak. MOMP results in the release of pro-apoptogenic factors, formation of an apoptosome, and activation of the cascade that leads to MOMP-mediated apoptosis (these events are marked by orange). In contrast, the central event for mPTP-mediated necrosis is the Ca2+-induced formation of mPTPC in the IMM and its mediation by the Bcl-2 members (Bax, Bak, Bcl-XL, Bcl-2, BID). mPTP opening rapidly dissipates the proton gradient across the IMM and induce mPTP-mediated necrosis (all of these events are marked by green). Thus, a possible functional link between Bcl-2 proteins and Ca2+-transport systems and between MOMP-mediated apoptosis and mPTP-mediated necrosis may exist. Intracellular or extracellular cell death stimuli may lead to the other types of RCD that are not directly related to the mediation of Ca2+ homeostasis by Bcl-2 members (including extrinsic apoptosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, LDCD, ADCD, ICD) (these events are marked by light blue). Full article ">

11 pages, 2062 KiB

Open AccessFeature PaperArticle

Separation of Fructose and Glucose via Nanofiltration in Presence of Fructooligosaccharides

by Zulhaj Rizki, Anja E. M. Janssen, Albert van der Padt and Remko M. Boom

Membranes 2020, 10(10), 298; https://doi.org/10.3390/membranes10100298 - 21 Oct 2020

Cited by 4 | Viewed by 3831

Abstract

Fructose and glucose are commonly present together in mixtures and may need to be separated. Current separation methods for these isomers are complex and costly. Nanofiltration is a cost-effective method that has been widely used for separating carbohydrates of different sizes; however, it [...] Read more.

Fructose and glucose are commonly present together in mixtures and may need to be separated. Current separation methods for these isomers are complex and costly. Nanofiltration is a cost-effective method that has been widely used for separating carbohydrates of different sizes; however, it is not commonly used for such similar molecules. Here, we report the separation of fructose and glucose in a nanofiltration system in the presence of fructooligosaccharides (FOS). Experiments were performed using a pilot-scale filtration setup using a spiral wound nanofiltration membrane with molecular weight cutoff of 1 kDa. We observed three important factors that affected the separation: (1) separation of monosaccharides only occurred in the presence of FOS and became more effective when FOS dominated the solution; (2) better separation was achieved when the monosaccharides were mainly fructose; and (3) the presence of salt improved the separation only moderately. The rejection ratio (R_f/R_g) in a fructose/glucose mixture is 0.92. We reported a rejection ratio of 0.69, which was observed in a mixture of 50 g/L FOS with a fructose to glucose ratio of 4.43. The separation is hypothesized to occur due to selective transport in the FOS layer, resulting in a preferential binding towards fructose. Full article

(This article belongs to the Section Membrane Applications)

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Rejection ratio of fructose over glucose (Rf/Rg) from various references [<a href="#B13-membranes-10-00298" class="html-bibr">13</a>,<a href="#B15-membranes-10-00298" class="html-bibr">15</a>,<a href="#B17-membranes-10-00298" class="html-bibr">17</a>,<a href="#B18-membranes-10-00298" class="html-bibr">18</a>,<a href="#B21-membranes-10-00298" class="html-bibr">21</a>] under different setups and feeds. Full article ">Figure 2
Effect of oligosaccharides concentration on selectivity in a nanofiltration system. The dotted line is the reference rejection ratio for a mixture with only fructose and glucose. The dot-dashed line is the reference rejection ratio for the FOS mixture. The dashed line is shown to guide the eye. The 95% confidence interval for concentration ratio and the rejections are shown inside the brackets. Full article ">Figure 3
Effect of the monosaccharide composition on selectivity in a nanofiltration system. The total oligosaccharide concentration was 35 g/L, and the total monosaccharide concentration was 16 g/L. The dotted line is the reference rejection ratio for a mixture with only fructose and glucose. The dot-dashed line is the reference rejection ratio for the FOS mixture. The dashed line is shown to guide the eye. The 95% confidence interval for concentration ratio and the rejections are shown inside the brackets. Full article ">Figure 4
The rejection ratio of fructose and glucose in a nanofiltration system with only monosaccharides. The total monosaccharide concentration was 16 g/L. The dotted line is the reference rejection ratio for a mixture with only fructose and glucose. The dot-dashed line is the reference rejection ratio for FOS mixture. The dashed line is shown to guide the eye. The 95% confidence interval for concentration ratio and the rejections are shown inside the brackets. Full article ">Figure 5
Effect of addition of salt on the separation of fructose and glucose in nanofiltration with only monosaccharides. The total monosaccharide concentration was 16 g/L. The dashed lines are shown to guide the eye. Full article ">Figure 6
Effects of the addition of salt on the separation of fructose and glucose in the FOS system. The oligosaccharide concentration was 35 g/L, and the monosaccharide concentration was 16 g/L. Full article ">

29 pages, 5168 KiB

Open AccessReview

Nanocomposite Membranes for Liquid and Gas Separations from the Perspective of Nanostructure Dimensions

by Pei Sean Goh, Kar Chun Wong and Ahmad Fauzi Ismail

Membranes 2020, 10(10), 297; https://doi.org/10.3390/membranes10100297 - 21 Oct 2020

Cited by 29 | Viewed by 6690

Abstract

One of the critical aspects in the design of nanocomposite membrane is the selection of a well-matched pair of nanomaterials and a polymer matrix that suits their intended application. By making use of the fascinating flexibility of nanoscale materials, the functionalities of the [...] Read more.

One of the critical aspects in the design of nanocomposite membrane is the selection of a well-matched pair of nanomaterials and a polymer matrix that suits their intended application. By making use of the fascinating flexibility of nanoscale materials, the functionalities of the resultant nanocomposite membranes can be tailored. The unique features demonstrated by nanomaterials are closely related to their dimensions, hence a greater attention is deserved for this critical aspect. Recognizing the impressive research efforts devoted to fine-tuning the nanocomposite membranes for a broad range of applications including gas and liquid separation, this review intends to discuss the selection criteria of nanostructured materials from the perspective of their dimensions for the production of high-performing nanocomposite membranes. Based on their dimension classifications, an overview of the characteristics of nanomaterials used for the development of nanocomposite membranes is presented. The advantages and roles of these nanomaterials in advancing the performance of the resultant nanocomposite membranes for gas and liquid separation are reviewed. By highlighting the importance of dimensions of nanomaterials that account for their intriguing structural and physical properties, the potential of these nanomaterials in the development of nanocomposite membranes can be fully harnessed. Full article

(This article belongs to the Special Issue Advances in Nanocomposite Membranes)

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15 pages, 20725 KiB

Open AccessArticle

Amino Acid Cross-Linked Graphene Oxide Membranes for Metal Ions Permeation, Insertion and Antibacterial Properties

by Lijuan Qian, Haijing Wang, Jingyi Yang, Xiaolei Chen, Xue Chang, Yu Nan, Zhuanyan He, Peizhuo Hu, Wangsuo Wu and Tonghuan Liu

Membranes 2020, 10(10), 296; https://doi.org/10.3390/membranes10100296 - 21 Oct 2020

Cited by 12 | Viewed by 2936

Abstract

Graphene oxide (GO) and its composite membranes have exhibited great potential for application in water purification and desalination. This article reports that a novel graphene oxide membrane (GOM) of ~5 µm thickness was fabricated onto a nylon membrane by vacuum filtration and cross-linked [...] Read more.

Graphene oxide (GO) and its composite membranes have exhibited great potential for application in water purification and desalination. This article reports that a novel graphene oxide membrane (GOM) of ~5 µm thickness was fabricated onto a nylon membrane by vacuum filtration and cross-linked by amino acids (L-alanine, L-phenylalanine, and serine). The GOM cross-linked by amino acids (GOM-A) exhibits excellent stability, high water flux, and high rejection to metal ions. The rejection coefficients to alkali and alkaline earth metal ions through GOM-A were over 94% and 96%, respectively. The rejection coefficients decreased with an increasing H⁺ concentration. Metal ions (K⁺, Ca²⁺, and Fe³⁺) can be inserted into GOM-A layers, which enlarges the interlayer spacing of GOM-A and neutralizes the electronegativity of the membrane, resulting in the decease in the rejection coefficients to metal ions. Meanwhile, GOM-A showed quite high antibacterial efficiency against E. coli. With the excellent performance as described above, GOM-A could be used to purify and desalt water. Full article

(This article belongs to the Special Issue Membranes: 10th Anniversary)

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39 pages, 6018 KiB

Open AccessReview

2D Nanocomposite Membranes: Water Purification and Fouling Mitigation

by Lara Loske, Keizo Nakagawa, Tomohisa Yoshioka and Hideto Matsuyama

Membranes 2020, 10(10), 295; https://doi.org/10.3390/membranes10100295 - 20 Oct 2020

Cited by 19 | Viewed by 5056

Abstract

In this study, the characteristics of different types of nanosheet membranes were reviewed in order to determine which possessed the optimum propensity for antifouling during water purification. Despite the tremendous amount of attention that nanosheets have received in recent years, their use to [...] Read more.

In this study, the characteristics of different types of nanosheet membranes were reviewed in order to determine which possessed the optimum propensity for antifouling during water purification. Despite the tremendous amount of attention that nanosheets have received in recent years, their use to render membranes that are resistant to fouling has seldom been investigated. This work is the first to summarize the abilities of nanosheet membranes to alleviate the effect of organic and inorganic foulants during water treatment. In contrast to other publications, single nanosheets, or in combination with other nanomaterials, were considered to be nanostructures. Herein, a broad range of materials beyond graphene-based nanomaterials is discussed. The types of nanohybrid membranes considered in the present work include conventional mixed matrix membranes, stacked membranes, and thin-film nanocomposite membranes. These membranes combine the benefits of both inorganic and organic materials, and their respective drawbacks are addressed herein. The antifouling strategies of nanohybrid membranes were divided into passive and active categories. Nanosheets were employed in order to induce fouling resistance via increased hydrophilicity and photocatalysis. The antifouling properties that are displayed by two-dimensional (2D) nanocomposite membranes also are examined. Full article

(This article belongs to the Special Issue Organic–Inorganic Hybrid Membranes for Separation and Purification Applications)

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15 pages, 8366 KiB

Open AccessArticle

Study of the Interaction of a Novel Semi-Synthetic Peptide with Model Lipid Membranes

by Lucia Sessa, Simona Concilio, Peter Walde, Tom Robinson, Petra S. Dittrich, Amalia Porta, Barbara Panunzi, Ugo Caruso and Stefano Piotto

Membranes 2020, 10(10), 294; https://doi.org/10.3390/membranes10100294 - 19 Oct 2020

Cited by 9 | Viewed by 3257

Abstract

Most linear peptides directly interact with membranes, but the mechanisms of interaction are far from being completely understood. Here, we present an investigation of the membrane interactions of a designed peptide containing a non-natural, synthetic amino acid. We selected a nonapeptide that is [...] Read more.

Most linear peptides directly interact with membranes, but the mechanisms of interaction are far from being completely understood. Here, we present an investigation of the membrane interactions of a designed peptide containing a non-natural, synthetic amino acid. We selected a nonapeptide that is reported to interact with phospholipid membranes, ALYLAIRKR, abbreviated as ALY. We designed a modified peptide (azoALY) by substituting the tyrosine residue of ALY with an antimicrobial azobenzene-bearing amino acid. Both of the peptides were examined for their ability to interact with model membranes, assessing the penetration of phospholipid monolayers, and leakage across the bilayer of large unilamellar vesicles (LUVs) and giant unilamellar vesicles (GUVs). The latter was performed in a microfluidic device in order to study the kinetics of leakage of entrapped calcein from the vesicles at the single vesicle level. Both types of vesicles were prepared from a 9:1 (mol/mol) mixture of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho(1′-rac-glycerol). Calcein leakage from the vesicles was more pronounced at a low concentration in the case of azoALY than for ALY. Increased vesicle membrane disturbance in the presence of azoALY was also evident from an enzymatic assay with LUVs and entrapped horseradish peroxidase. Molecular dynamics simulations of ALY and azoALY in an anionic POPC/POPG model bilayer showed that ALY peptide only interacts with the lipid head groups. In contrast, azoALY penetrates the hydrophobic core of the bilayers causing a stronger membrane perturbation as compared to ALY, in qualitative agreement with the experimental results from the leakage assays. Full article

(This article belongs to the Special Issue Modeling and Simulation of Lipid Membranes)

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Density profile of the system ALY-POPC/POPG (9:1) after 45 ns of molecular dynamic (MD) simulation. Cyan line: water molecules; blue line: phosphorous atoms; dashed blue line: nitrogen atoms; dashed black line: carbon chains of the phospholipid, black line: terminal carbons of the phospholipid; red line ALY peptide. Full article ">Figure 2
Density profile of the system azoALY-POPC/POPG (9:1) after 45 ns of MD simulation. Cyan line: water molecules; blue line: phosphorous atoms; dashed blue line: nitrogen atoms; dashed black line: carbon chains of the phospholipid, black line: terminal carbons of the phospholipid; red line azoALY peptide. Full article ">Figure 3
Thickness maps of POPC/POPG/ALY (a) and POPC/POPG/azoALY (b) during the last 5 ns of the MD simulation (total time 50 ns). The top panel is the deformation profile as a color map projected onto the surface defined by fitting a grid (spacing 2 Å) to the positions of the phosphate atoms in the top leaflet during the trajectory, followed by time averaging and spatial smoothing. Full article ">Figure 4
Confocal fluorescence images of calcein leakage from an exemplary POPC/POPG (9:1) GUV with azoALY added externally (50 μM at time 0 min. A single GUV was held in one spatial location using a microfluidic platform; for details, see reference [<a href="#B39-membranes-10-00294" class="html-bibr">39</a>]. Scale bar: 5 μm. Full article ">Figure 5
Kinetics of calcein release from POPC/POPG (9:1) GUVs for externally added ALY or azoALY (1 and 50 μM) using 3 separate vesicles. Control measurements without the addition of peptide showed no calcein release (data not shown). Full article ">Figure 6
Horseradish peroxidase isoenzyme C enzyme (HRPC) enzyme leakage from large unilamellar vesicles (LUVs), measured with H2O2 and ABTS2−, the latter being membrane impermeable. Full article ">Figure 7
Enzymatic activity time dependence in four different systems: (grey bar) Blank vesicles with HRPC entrapped without peptides (dilution factor 100×); (green bar) control vesicles with HRPC entrapped, adding Triton X-100 (dilution factor 2000×); (yellow bar) vesicles with HRPC entrapped, adding a solution of ALY at 4 μM (dilution factor 100×); and (blue bar) vesicles with HRPC entrapped, adding a solution of azoALY at 4 μM (dilution factor 100×). Each data point shown is the average from three measurements and the small standard deviation is indicated with a bar. Full article ">Scheme 1
Synthetic path of amino acid azoTyr. Full article ">

17 pages, 7073 KiB

Open AccessArticle

Enhanced Fouling Resistance and Antimicrobial Property of Ultrafiltration Membranes Via Polyelectrolyte-Assisted Silver Phosphate Nanoparticle Immobilization

by Kunal Olimattel, Jared Church, Woo Hyoung Lee, Karin Y. Chumbimuni-Torres, Lei Zhai and A H M Anwar Sadmani

Membranes 2020, 10(10), 293; https://doi.org/10.3390/membranes10100293 - 17 Oct 2020

Cited by 12 | Viewed by 3782

Abstract

Ultrafiltration (UF) is a low-pressure membrane that yields higher permeate flux and saves significant operating costs compared to high-pressure membranes; however, studies addressing the combined improvement of anti-organic and biofouling properties of UF membranes are lacking. This study investigated the fouling resistance and [...] Read more.

Ultrafiltration (UF) is a low-pressure membrane that yields higher permeate flux and saves significant operating costs compared to high-pressure membranes; however, studies addressing the combined improvement of anti-organic and biofouling properties of UF membranes are lacking. This study investigated the fouling resistance and antimicrobial property of a UF membrane via silver phosphate nanoparticle (AgPNP) embedded polyelectrolyte (PE) functionalization. Negatively charged polyacrylic acid (PAA) and positively charged polyallylamine hydrochloride (PAH) were deposited on the membrane using a fluidic layer-by-layer assembly technique. AgPNPs were immobilized within the crosslinked “bilayers” (BL) of PAH/PAA. The effectiveness of AgPNP immobilization was confirmed by microprofile measurements on membrane surfaces using a solid contact Ag micro-ion-selective electrode. Upon stable and uniform BL formation on the membrane surface, the permeate flux was governed by a combined effect of PAH/PAA-derived hydrophilicity and surface/pore coverage by the BLs “tightening” of the membrane. When fouled by a model organic foulant (humic acid), the functionalized membrane exhibited a lower flux decline and a greater flux recovery due to the electrostatic repulsion imparted by PAA when compared to the unmodified membrane. The functionalization rendered antimicrobial property, as indicated by fewer attachments of bacteria that initiate the formation of biofilms leading to biofouling. Full article

(This article belongs to the Section Polymeric Membranes)

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15 pages, 4574 KiB

Open AccessEditor’s ChoiceArticle

Graphene Oxide-Based Membranes for Water Purification Applications: Effect of Plasma Treatment on the Adhesion and Stability of the Synthesized Membranes

by Omer Alnoor, Tahar Laoui, Ahmed Ibrahim, Feras Kafiah, Ghaith Nadhreen, Sultan Akhtar and Zafarullah Khan

Membranes 2020, 10(10), 292; https://doi.org/10.3390/membranes10100292 - 17 Oct 2020

Cited by 19 | Viewed by 4516

Abstract

The adhesion enhancement of graphene oxide (GO) and reduced graphene oxide (rGO) layer in the underlying polyethersulfone (PES) microfiltration membrane is a crucial step towards developing a high-performance membrane for water purification applications. In the present study, we modified the surface of a [...] Read more.

The adhesion enhancement of graphene oxide (GO) and reduced graphene oxide (rGO) layer in the underlying polyethersulfone (PES) microfiltration membrane is a crucial step towards developing a high-performance membrane for water purification applications. In the present study, we modified the surface of a PES microfiltration membrane with plasma treatment (PT) carried out at different times (2, 10, and 20 min). We studied the effect of PT on the adhesion, stability, and performance of the synthesized GO/rGO-PES membranes. The membranes’ surface morphology and chemistry were characterized using atomic force microscopy, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. The membrane performance was evaluated by conducting a diffusion test for potassium chloride (KCl) ions through the synthesized membranes. The results revealed that the 2 min PT enhanced the adhesion and stability of the deposited GO/rGO layer when compared to the other plasma-treated membranes. This was associated with an increase in the KCl ion rejection from ~27% to 57%. Surface morphology analysis at a high magnification was performed for the synthesized membranes before and after the diffusion test. Although the membrane’s rejection was improved, the analysis revealed that the GO layers suffered from micro/nano cracks, which negatively affected the membrane’s overall performance. The use of the rGO layer, however, helped in minimizing the GO cracks and enhanced the KCl ion rejection to approximately 94%. Upon increasing the number of rGO deposition cycles from three to five, the performance of the developed rGO-PES membrane was further improved, as confirmed by the increase in its ion rejection to ~99%. Full article

(This article belongs to the Special Issue Advances in Nanocomposite Membranes)

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15 pages, 3495 KiB

Open AccessArticle

Flux-Reducing Tendency of Pd-Based Membranes Employed in Butane Dehydrogenation Processes

by Thijs A. Peters, Marit Stange and Rune Bredesen

Membranes 2020, 10(10), 291; https://doi.org/10.3390/membranes10100291 - 16 Oct 2020

Cited by 4 | Viewed by 2567

Abstract

We report on the effect of butane and butylene on hydrogen permeation through thin state-of-the-art Pd–Ag alloy membranes. A wide range of operating conditions, such as temperature (200–450 °C) and H₂/butylene (or butane) ratio (0.5–3), on the flux-reducing tendency were investigated. [...] Read more.

We report on the effect of butane and butylene on hydrogen permeation through thin state-of-the-art Pd–Ag alloy membranes. A wide range of operating conditions, such as temperature (200–450 °C) and H₂/butylene (or butane) ratio (0.5–3), on the flux-reducing tendency were investigated. In addition, the behavior of membrane performance during prolonged exposure to butylene was evaluated. In the presence of butane, the flux-reducing tendency was found to be limited up to the maximum temperature investigated, 450 °C. Compared to butane, the flux-reducing tendency in the presence of butylene was severe. At 400 °C and 20% butylene, the flux decreases by ~85% after 3 h of exposure but depends on temperature and the H₂/butylene ratio. In terms of operating temperature, an optimal performance was found at 250–300 °C with respect to obtaining the highest absolute hydrogen flux in the presence of butylene. At lower temperatures, the competitive adsorption of butylene over hydrogen accounts for a large initial flux penalty. Full article

(This article belongs to the Special Issue Membrane Reactors for Process Intensification: Recent Advances and Key Applications)

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16 pages, 11661 KiB

Open AccessArticle

Fabrication of Bentonite–Silica Sand/Suspended Waste Palm Leaf Composite Membrane for Water Purification

by Saad A. Aljlil

Membranes 2020, 10(10), 290; https://doi.org/10.3390/membranes10100290 - 16 Oct 2020

Cited by 7 | Viewed by 2821

Abstract

In this study, a method for fabricating tubular ceramic membranes via extrusion using economical and locally available bentonite–silica sand and waste palm leaves was developed as a tool for conducting the necessary task of purifying water polluted with oil and suspended solid materials [...] Read more.

In this study, a method for fabricating tubular ceramic membranes via extrusion using economical and locally available bentonite–silica sand and waste palm leaves was developed as a tool for conducting the necessary task of purifying water polluted with oil and suspended solid materials produced via various industrial processes. The developed tubular ceramic membranes were found to be highly efficient at separating the pollutants from water. The properties of the fabricated membrane were evaluated via mechanical testing, pore size distribution analysis, and contact angle measurements. The water contact angle of the fabricated membrane was determined to be 55.5°, which indicates that the membrane surface is hydrophilic, and the average pore size was found to be 66 nm. The membrane was found to demonstrate excellent corrosion resistance under acidic as well as basic conditions, with weight losses of less than 1% in each case. The membrane surface was found to be negatively charged and it could strongly repulse the negatively charged fine bentonite particles and oil droplets suspended in the water, thereby enabling facile purification through backwashing. The obtained ceramic membranes with desirable hydrophilic properties can thus serve as good candidates for use in ultrafiltration processes. Full article

(This article belongs to the Section Membrane Applications)

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19 pages, 4847 KiB

Open AccessArticle

Enhancing the Antibacterial Properties of PVDF Membrane by Hydrophilic Surface Modification Using Titanium Dioxide and Silver Nanoparticles

by Kajeephan Samree, Pen-umpai Srithai, Panaya Kotchaplai, Pumis Thuptimdang, Pisut Painmanakul, Mali Hunsom and Sermpong Sairiam

Membranes 2020, 10(10), 289; https://doi.org/10.3390/membranes10100289 - 15 Oct 2020

Cited by 42 | Viewed by 4738

Abstract

This work investigates polyvinylidene fluoride (PVDF) membrane modification to enhance its hydrophilicity and antibacterial properties. PVDF membranes were coated with nanoparticles of titanium dioxide (TiO₂-NP) and silver (AgNP) at different concentrations and coating times and characterized for their porosity, morphology, chemical [...] Read more.

This work investigates polyvinylidene fluoride (PVDF) membrane modification to enhance its hydrophilicity and antibacterial properties. PVDF membranes were coated with nanoparticles of titanium dioxide (TiO₂-NP) and silver (AgNP) at different concentrations and coating times and characterized for their porosity, morphology, chemical functional groups and composition changes. The results showed the successfully modified PVDF membranes containing TiO₂-NP and AgNP on their surfaces. When the coating time was increased from 8 to 24 h, the compositions of Ti and Ag of the modified membranes were increased from 1.39 ± 0.13 to 4.29 ± 0.16 and from 1.03 ± 0.07 to 3.62 ± 0.08, respectively. The water contact angle of the membranes was decreased with increasing the coating time and TiO₂-NP/AgNP ratio. The surface roughness and permeate fluxes of coated membranes were increased due to increased hydrophilicity. Antimicrobial and antifouling properties were investigated by the reduction of Escherichia coli cells and the inhibition of biofilm formation on the membrane surface, respectively. Compared with that of the original PVDF membrane, the modified membranes exhibited antibacterial efficiency up to 94% against E. coli cells and inhibition up to 65% of the biofilm mass reduction. The findings showed hydrophilic improvement and an antimicrobial property for possible wastewater treatment without facing the eminent problem of biofouling. Full article

(This article belongs to the Special Issue CESE-2019: Applications of Membranes for Sustainability)

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17 pages, 2864 KiB

Open AccessArticle

Scaling Risk Assessment in Nanofiltration of Mine Waters

by Krzysztof Mitko, Ewa Laskowska, Marian Turek, Piotr Dydo and Krzysztof Piotrowski

Membranes 2020, 10(10), 288; https://doi.org/10.3390/membranes10100288 - 15 Oct 2020

Cited by 11 | Viewed by 2657

Abstract

Nanofiltration can be applied for the treatment of mine waters. One of the main problems is the risk of crystallization of sparingly soluble salts on the membrane surface (scaling). In this work, a series of batch-mode nanofiltration experiments of the mine waters was [...] Read more.

Nanofiltration can be applied for the treatment of mine waters. One of the main problems is the risk of crystallization of sparingly soluble salts on the membrane surface (scaling). In this work, a series of batch-mode nanofiltration experiments of the mine waters was performed in a dead-end Sterlitech^® HP 4750X Stirred Cell. Based on the laboratory results, the concentration profiles of individual ions along the membrane length in a single-pass industrial-scale nanofiltration (NF) unit was calculated, assuming the tanks-in-series flow model inside the membrane module. These calculations also propose a method for estimating the maximum achievable recovery before the occurrence of the calcium sulfate dihydrate scaling in a single-pass NF 40″ length spiral wound module, simultaneously allowing metastable supersaturation of calcium sulfate dihydrate. The performance of three membrane types (NF270, NFX, NFDL) has been evaluated for the nanofiltration of mine water. Full article

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

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22 pages, 2263 KiB

Open AccessArticle

Integrating Pressure-Driven Membrane Separation Processes to Improve Eco-Efficiency in Cheese Manufacture: A Preliminary Case Study

by Scott Benoit, Julien Chamberland, Alain Doyen, Manuele Margni, Christian Bouchard and Yves Pouliot

Membranes 2020, 10(10), 287; https://doi.org/10.3390/membranes10100287 - 15 Oct 2020

Cited by 7 | Viewed by 3391

Abstract

Pressure-driven membrane separation processes are commonly used in cheese milk standardization. Using ultrafiltration (UF) or microfiltration (MF), membrane separation processes make it possible to concentrate the milk proteins and increase the yields of cheese vats. However, the contribution of membrane separation processes to [...] Read more.

Pressure-driven membrane separation processes are commonly used in cheese milk standardization. Using ultrafiltration (UF) or microfiltration (MF), membrane separation processes make it possible to concentrate the milk proteins and increase the yields of cheese vats. However, the contribution of membrane separation processes to the environmental impact and economical profitability of dairy processes is still unclear. The objective of this study was to evaluate the contribution of membrane separation processes to the eco-efficiency of cheddar cheese production in Québec (Canada) using process simulation. Three scenarios were compared: two included UF or MF at the cheese milk standardization step, and one did not incorporate membrane separation processes. The results showed that even if membrane separation processes make it possible to increase vat yields, they do not improve the eco-efficiency of cheddar cheese processes. However, membrane separation processes may benefit the eco-efficiency of the process more when used for byproduct valorization. Full article

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Process flow diagram of scenarios A and B. In scenario A, the concentration step is carried out using ultrafiltration membranes (10 kDa) until a volume concentration factor (VCF) of 3.5 is reached, followed by continuous diafiltration (2.0 DV). In scenario B, the concentration step is carried out using microfiltration membranes (0.1 µm) until a VCF of 3.0 is reached, followed by discontinuous diafiltration (2.0 DV each). Full article ">Figure 2
Process flow diagram of scenario C. Based on the information from Tetra Pak [<a href="#B18-membranes-10-00287" class="html-bibr">18</a>]. Full article ">Figure 3
Distribution of the dairy fluids at the standardization step for scenarios A, B, and C. Full article ">Figure 4
Process flow diagram of the multistage filtration units of scenarios A and B. Full article ">Figure 5
Comparisons of the net margin generated per ton of raw milk received as a function of the selling prices ($CAD·kg−1) of the product and coproducts from scenarios A, B, and C for whey powder selling prices lower in scenario C than in scenarios A and B. (a) All permeate powder (PP) prices. (b) Lowest PP price. (c) Highest PP price. WP: Whey Powder, Sc.: Scenario, PP: Permeate Powder. Full article ">

11 pages, 7181 KiB

Open AccessArticle

Enhanced Selective Hydrogen Permeation through Graphdiyne Membrane: A Theoretical Study

by Quan Liu, Long Cheng and Gongping Liu

Membranes 2020, 10(10), 286; https://doi.org/10.3390/membranes10100286 - 15 Oct 2020

Cited by 13 | Viewed by 3260

Abstract

Graphdiyne (GDY), with uniform pores and atomic thickness, is attracting widespread attention for application in H₂ separation in recent years. However, the challenge lies in the rational design of GDYs for fast and selective H₂ permeation. By MD and DFT calculations, [...] Read more.

Graphdiyne (GDY), with uniform pores and atomic thickness, is attracting widespread attention for application in H₂ separation in recent years. However, the challenge lies in the rational design of GDYs for fast and selective H₂ permeation. By MD and DFT calculations, several flexible GDYs were constructed to investigate the permeation properties of four pure gas (H₂, N₂, CO₂, and CH₄) and three equimolar binary mixtures (H₂/N₂, H₂/CO₂, and H₂/CH₄) in this study. When the pore size is smaller than 2.1 Å, the GDYs acted as an exceptional filter for H₂ with an approximately infinite H₂ selectivity. Beyond the size-sieving effect, in the separation process of binary mixtures, the blocking effect arising from the strong gas–membrane interaction was proven to greatly impede H₂ permeation. After understanding the mechanism, the H₂ permeance of the mixtures of H₂/CO₂ was further increased to 2.84 × 10⁵ GPU by reducing the blocking effect with the addition of a tiny amount of surface charges, without sacrificing the selectivity. This theoretical study provides an additional atomic understanding of H₂ permeation crossing GDYs, indicating that the GDY membrane could be a potential candidate for H₂ purification. Full article

(This article belongs to the Special Issue Polymer Membranes for Gas Separation)

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30 pages, 2765 KiB

Open AccessReview

A Review of CFD Modelling and Performance Metrics for Osmotic Membrane Processes

by Kang Yang Toh, Yong Yeow Liang, Woei Jye Lau and Gustavo A. Fimbres Weihs

Membranes 2020, 10(10), 285; https://doi.org/10.3390/membranes10100285 - 15 Oct 2020

Cited by 32 | Viewed by 6940

Abstract

Simulation via Computational Fluid Dynamics (CFD) offers a convenient way for visualising hydrodynamics and mass transport in spacer-filled membrane channels, facilitating further developments in spiral wound membrane (SWM) modules for desalination processes. This paper provides a review on the use of CFD modelling [...] Read more.

Simulation via Computational Fluid Dynamics (CFD) offers a convenient way for visualising hydrodynamics and mass transport in spacer-filled membrane channels, facilitating further developments in spiral wound membrane (SWM) modules for desalination processes. This paper provides a review on the use of CFD modelling for the development of novel spacers used in the SWM modules for three types of osmotic membrane processes: reverse osmosis (RO), forward osmosis (FO) and pressure retarded osmosis (PRO). Currently, the modelling of mass transfer and fouling for complex spacer geometries is still limited. Compared with RO, CFD modelling for PRO is very rare owing to the relative infancy of this osmotically driven membrane process. Despite the rising popularity of multi-scale modelling of osmotic membrane processes, CFD can only be used for predicting process performance in the absence of fouling. This paper also reviews the most common metrics used for evaluating membrane module performance at the small and large scales. Full article

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

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Schematic diagram of a spiral wound membrane (SWM) module [<a href="#B2-membranes-10-00285" class="html-bibr">2</a>]. Full article ">Figure 2
Schematic figures illustrating the principles of (a) forward osmosis (FO), (b) reverse osmosis (RO) and (c) pressure retarded osmosis (PRO). Full article ">Figure 3
Spacer geometry configurations for (a) conventional spacer [<a href="#B68-membranes-10-00285" class="html-bibr">68</a>], (b) triply periodic minimal surface (TPMS) spacer [<a href="#B52-membranes-10-00285" class="html-bibr">52</a>], (c) perforated spacer [<a href="#B55-membranes-10-00285" class="html-bibr">55</a>] and (d) submerged spacer with nodes [<a href="#B58-membranes-10-00285" class="html-bibr">58</a>]. Full article ">Figure 4
Experimental setup for flow visualisation of PIV [<a href="#B59-membranes-10-00285" class="html-bibr">59</a>]. Full article ">Figure 5
Velocity vector obtained from particle image velocimetry (PIV) imaging at centre of membrane channel for (a) ladder orientation and (b) normal orientation [<a href="#B59-membranes-10-00285" class="html-bibr">59</a>]. Full article ">Figure 6
Concentration profile across an FO membrane showing the different types of concentration polarisation. Full article ">Figure 7
Examples of (a) FO–RO [<a href="#B132-membranes-10-00285" class="html-bibr">132</a>], (b) PRO–RO [<a href="#B14-membranes-10-00285" class="html-bibr">14</a>] and (c) FO–RO–PRO hybrid systems [<a href="#B22-membranes-10-00285" class="html-bibr">22</a>]. Full article ">

40 pages, 1800 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Forward Osmosis as Concentration Process: Review of Opportunities and Challenges

by Gaetan Blandin, Federico Ferrari, Geoffroy Lesage, Pierre Le-Clech, Marc Héran and Xavier Martinez-Lladó

Membranes 2020, 10(10), 284; https://doi.org/10.3390/membranes10100284 - 14 Oct 2020

Cited by 60 | Viewed by 10222

Abstract

In the past few years, osmotic membrane systems, such as forward osmosis (FO), have gained popularity as “soft” concentration processes. FO has unique properties by combining high rejection rate and low fouling propensity and can be operated without significant pressure or temperature gradient, [...] Read more.

In the past few years, osmotic membrane systems, such as forward osmosis (FO), have gained popularity as “soft” concentration processes. FO has unique properties by combining high rejection rate and low fouling propensity and can be operated without significant pressure or temperature gradient, and therefore can be considered as a potential candidate for a broad range of concentration applications where current technologies still suffer from critical limitations. This review extensively compiles and critically assesses recent considerations of FO as a concentration process for applications, including food and beverages, organics value added compounds, water reuse and nutrients recovery, treatment of waste streams and brine management. Specific requirements for the concentration process regarding the evaluation of concentration factor, modules and design and process operation, draw selection and fouling aspects are also described. Encouraging potential is demonstrated to concentrate streams more than 20-fold with high rejection rate of most compounds and preservation of added value products. For applications dealing with highly concentrated or complex streams, FO still features lower propensity to fouling compared to other membranes technologies along with good versatility and robustness. However, further assessments on lab and pilot scales are expected to better define the achievable concentration factor, rejection and effective concentration of valuable compounds and to clearly demonstrate process limitations (such as fouling or clogging) when reaching high concentration rate. Another important consideration is the draw solution selection and its recovery that should be in line with application needs (i.e., food compatible draw for food and beverage applications, high osmotic pressure for brine management, etc.) and be economically competitive. Full article

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

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16 pages, 6615 KiB

Open AccessArticle

Analysis of Dynamics Targeting CNT-Based Drug Delivery through Lung Cancer Cells: Design, Simulation, and Computational Approach

by Nafiseh Sohrabi, Afshar Alihosseini, Vahid Pirouzfar and Maysam Zamani Pedram

Membranes 2020, 10(10), 283; https://doi.org/10.3390/membranes10100283 - 14 Oct 2020

Cited by 18 | Viewed by 3033

Abstract

Nowadays, carbon nano (CN) structures and specifically carbon nanotubes (CNTs), because of the nanotube’s nanoscale shape, are widely used in carrier and separation applications. The conjugation of CNTs with polysaccharide, proteins, drugs, and magnetic nanoparticles provides a chance for smart targeting and trajectory [...] Read more.

Nowadays, carbon nano (CN) structures and specifically carbon nanotubes (CNTs), because of the nanotube’s nanoscale shape, are widely used in carrier and separation applications. The conjugation of CNTs with polysaccharide, proteins, drugs, and magnetic nanoparticles provides a chance for smart targeting and trajectory manipulation, which are used in the crucial field of life science applications, including for cancer disease diagnostics and treatments. Providing an optimal procedure for delivering a drug to a specific area based on mathematical criteria is key in systemic delivery design. Trajectory guidance and applied force control are the main parameters affected by systemic delivery. Moreover, a better understanding of the tissue parameters and cell membrane molecular behaviour are other factors that can be indirectly affected by the targeted delivery. Both sides are an essential part of successful targeting. The lung is one of the challenging organs for drug delivery inside the human body. It has a large surface area with a thin epithelium layer. A few severe diseases directly involve human lung cells, and optimal and successful drug delivery to the lung for the treatment procedure is vital. In this paper, we studied functionalized CNTs’ targeted delivery via crossing through the lung cell membrane. Molecular dynamics (MD) software simulated all the interaction forces. Mathematical modelling of the cell membrane and proposed delivery system based on the relation of velocity and force has been considered. Dynamics equations for CNTs were defined in the time and frequency domain using control theory methods. The proposed delivery system consists of two main parts: crossing through the cell membrane and targeting inside the cell. For both steps, a mathematical model and a proper magnetic field profile have been proposed. The designed system provides criteria for crossing through the cell membrane within 30 s to 5 min and a translocation profile of 1 to 100 Å. Full article

(This article belongs to the Special Issue Study on Drug-Membrane Interactions)

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12 pages, 2124 KiB

Open AccessArticle

Performance and Microbial Community of Different Biofilm Membrane Bioreactors Treating Antibiotic-Containing Synthetic Mariculture Wastewater

by Huining Zhang, Xin Yuan, Hanqing Wang, Shuoqi Ma and Bixiao Ji

Membranes 2020, 10(10), 282; https://doi.org/10.3390/membranes10100282 - 14 Oct 2020

Cited by 8 | Viewed by 2828

Abstract

The performance of pollutant removals, tetracycline (TC) and norfloxacin (NOR) removals, membrane fouling mitigation and the microbial community of three Anoxic/Oxic membrane bioreactors (AO-MBRs), including a moving bed biofilm MBR (MBRa), a fixed biofilm MBR (MBRb) and an AO-MBR (MBRc) for control, were [...] Read more.

The performance of pollutant removals, tetracycline (TC) and norfloxacin (NOR) removals, membrane fouling mitigation and the microbial community of three Anoxic/Oxic membrane bioreactors (AO-MBRs), including a moving bed biofilm MBR (MBRa), a fixed biofilm MBR (MBRb) and an AO-MBR (MBRc) for control, were compared in treating antibiotic-containing synthetic mariculture wastewater. The results showed that MBRb had the best effect on antibiotic removal and membrane fouling mitigation compared to the other two bioreactors. The maximum removal rate of TC reached 91.65% and the maximum removal rate of NOR reached 45.46% in MBRb. The addition of antibiotics had little effect on the removal of chemical oxygen demand (COD) and ammonia nitrogen (NH₄⁺-N)—both maintained more than 90% removal rate during the entire operation. High-throughput sequencing demonstrated that TC and NOR resulted in a significant decrease in the microbial diversity and the microbial richness MBRs. Flavobacteriia, Firmicutes and Azoarcus, regarded as drug-resistant bacteria, might play a crucial part in the removal of antibiotics. In addition, the dynamics of microbial community had a great change, which included the accumulation of resistant microorganisms and the gradual reduction or disappearance of other microorganisms under antibiotic pressure. The research provides an insight into the antibiotic-containing mariculture wastewater treatment and has certain reference value. Full article

(This article belongs to the Special Issue Membrane Biofouling Mitigation: From Fundamental Concepts to Applicative Solutions)

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29 pages, 3493 KiB

Open AccessReview

Application of Hybrid Membrane Processes Coupling Separation and Biological or Chemical Reaction in Advanced Wastewater Treatment

by Raffaele Molinari, Cristina Lavorato and Pietro Argurio

Membranes 2020, 10(10), 281; https://doi.org/10.3390/membranes10100281 - 13 Oct 2020

Cited by 33 | Viewed by 5050

Abstract

The rapid urbanization and water shortage impose an urgent need in improving sustainable water management without compromising the socioeconomic development all around the world. In this context, reclaimed wastewater has been recognized as a sustainable water management strategy since it represents an alternative [...] Read more.

The rapid urbanization and water shortage impose an urgent need in improving sustainable water management without compromising the socioeconomic development all around the world. In this context, reclaimed wastewater has been recognized as a sustainable water management strategy since it represents an alternative water resource for non-potable or (indirect) potable use. The conventional wastewater remediation approaches for the removal of different emerging contaminants (pharmaceuticals, dyes, metal ions, etc.) are unable to remove/destroy them completely. Hybrid membrane processes (HMPs) are a powerful solution for removing emerging pollutants from wastewater. On this aspect, the present paper focused on HMPs obtained by the synergic coupling of biological and/or chemical reaction driven processes with membrane processes, giving a critical overview and particular emphasis on some case studies reported in the pertinent literature. By using these processes, a satisfactory quality of treated water can be achieved, permitting its sustainable reuse in the hydrologic cycle while minimizing environmental and economic impact. Full article

(This article belongs to the Special Issue Membrane Preparation and Characterisation and Their Application in Environmental Field (Volume II))

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16 pages, 2063 KiB

Open AccessPerspective

Membrane and Electrochemical Processes for Water Desalination: A Short Perspective and the Role of Nanotechnology

by Moon Son, Kyung Hwa Cho, Kwanho Jeong and Jongkwan Park

Membranes 2020, 10(10), 280; https://doi.org/10.3390/membranes10100280 - 12 Oct 2020

Cited by 9 | Viewed by 3852

Abstract

In the past few decades, membrane-based processes have become mainstream in water desalination because of their relatively high water flux, salt rejection, and reasonable operating cost over thermal-based desalination processes. The energy consumption of the membrane process has been continuously lowered (from >10 [...] Read more.

In the past few decades, membrane-based processes have become mainstream in water desalination because of their relatively high water flux, salt rejection, and reasonable operating cost over thermal-based desalination processes. The energy consumption of the membrane process has been continuously lowered (from >10 kWh m⁻³ to ~3 kWh m⁻³) over the past decades but remains higher than the theoretical minimum value (~0.8 kWh m⁻³) for seawater desalination. Thus, the high energy consumption of membrane processes has led to the development of alternative processes, such as the electrochemical, that use relatively less energy. Decades of research have revealed that the low energy consumption of the electrochemical process is closely coupled with a relatively low extent of desalination. Recent studies indicate that electrochemical process must overcome efficiency rather than energy consumption hurdles. This short perspective aims to provide platforms to compare the energy efficiency of the representative membrane and electrochemical processes based on the working principle of each process. Future water desalination methods and the potential role of nanotechnology as an efficient tool to overcome current limitations are also discussed. Full article

(This article belongs to the Special Issue Nanotechnology in Engineered Membranes)

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15 pages, 2300 KiB

Open AccessArticle

Solid-State Membrane Sensors Based on Man-Tailored Biomimetic Receptors for Selective Recognition of Isoproturon and Diuron Herbicides

by Ayman H. Kamel, Abd El-Galil E. Amr, Mohamed A. Al-Omar and Abdulrahman A. Almehizia

Membranes 2020, 10(10), 279; https://doi.org/10.3390/membranes10100279 - 12 Oct 2020

Cited by 6 | Viewed by 2774

Abstract

Solid-contact ion-selective electrodes (SC-ISEs) have shown great potential for routine and portable ion detection. The introduction of nanomaterials as ion-to-electron transducers and the adoption of different performance-enhancement strategies have significantly promoted the development of SC-ISEs. Herein, new solid-contact ion-selective electrodes, along with the [...] Read more.

Solid-contact ion-selective electrodes (SC-ISEs) have shown great potential for routine and portable ion detection. The introduction of nanomaterials as ion-to-electron transducers and the adoption of different performance-enhancement strategies have significantly promoted the development of SC-ISEs. Herein, new solid-contact ion-selective electrodes, along with the implementation of multiwalled carbon nanotubes (MWCNTs) as ion-to-electron transducers and potassium tetrakis (p-chlorophenyl) borate (KTpClB) as lipophilic ionic additives, were presented for the detection of isoproturon (IPU) and diuron (DU) herbicides. Molecularly imprinted polymers (MIPs), with special molecule recognition properties for isoproturon (IPU) and diuron (DU), were prepared, characterized, and introduced as sensory recognition materials in the presented electrodes. Sensors revealed a near-Nernstian response for both isoproturon (IPU) and diuron (DU) with slopes of 53.1 ± 1.2 (r² = 0.997) and 57.2 ± 0.3 (r² = 0.998) over the linear ranges of 2.2 × 10⁻⁶–1.0 × 10⁻³ M and 3.2 × 10⁻⁶–1.0 × 10⁻³ M with detection limits of 8.3 × 10⁻⁷ and 1.4 × 10⁻⁶ M, respectively. The response time of the presented sensors was found to be <5 s and the lifetime was at least eight weeks. The sensors exhibited good selectivity towards isoproturon (IPU) and diuron (DU) in comparison with some other herbicides, alkali, alkaline earth, and heavy metal ions. The presented sensors were successfully applied for the direct determination of isoproturon (IPU) and diuron (DU) in real water samples. Full article

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

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14 pages, 3558 KiB

Open AccessArticle

Preparation of Shellac Resin Microcapsules Coated with Urea Formaldehyde Resin and Properties of Waterborne Paint Films for Tilia amurensis Rupr.

by Xiaoxing Yan and Lin Wang

Membranes 2020, 10(10), 278; https://doi.org/10.3390/membranes10100278 - 12 Oct 2020

Cited by 18 | Viewed by 2415

Abstract

A two-step in situ polymerization method was utilized to fabricate urea formaldehyde (UF) resin-coated shellac resin microcapsules. The morphology and composition of microcapsules with different core-wall ratios were analyzed by scanning electron microscope (SEM) and infrared (IR) spectrum. The effects of different concentrations [...] Read more.

A two-step in situ polymerization method was utilized to fabricate urea formaldehyde (UF) resin-coated shellac resin microcapsules. The morphology and composition of microcapsules with different core-wall ratios were analyzed by scanning electron microscope (SEM) and infrared (IR) spectrum. The effects of different concentrations of microcapsules on gloss, color difference, hardness, adhesion, and impact resistance of waterborne paint films were studied. At the same time, the self-healing effect of the prepared microcapsules applied to waterborne paint film was discussed. The results revealed that the shellac resin microcapsules coated with UF resin were successfully prepared. At the 0.67:1 and 0.75:1 core-wall ratios, the color differences of the paint film with 0–20.0% (weight percent) microcapsules were small and the color was uniform. Under the condition of 60° incident angle and the same microcapsule concentration, a good gloss was obtained. When the concentration was 20.0%, the hardness of paint film reached the maximum value. The adhesion of paint film was better, which was not affected by microcapsule concentration. When the concentration was 5.0% and 10.0%, the microstructure of paint film was good. The paint film with a 10.0% concentration of the shellac resin microcapsules coated with UF resin had better self-healing performance and the comprehensive performance was better. This paper provides the basis for the industrial application of self-healing waterborne wood paint films. Full article

(This article belongs to the Section Membrane Chemistry)

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16 pages, 4997 KiB

Open AccessFeature PaperArticle

Hyperbranch-Crosslinked S-SEBS Block Copolymer Membranes for Desalination by Pervaporation

by Mengyu Yan, Yunyun Lu, Na Li, Feixiang Zeng, Qinzhuo Wang, Hongcun Bai and Zongli Xie

Membranes 2020, 10(10), 277; https://doi.org/10.3390/membranes10100277 - 10 Oct 2020

Cited by 16 | Viewed by 3457

Abstract

Sulfonated aromatic polymer (SAP) featuring hydrophilic nanochannels for water transport is a promising membrane material for desalination. SAPs with a high sulfonation degree favor water transport but suffer from reduced mechanical strength and membrane swelling. In this work, a hyperbranched polyester, H302, was [...] Read more.

Sulfonated aromatic polymer (SAP) featuring hydrophilic nanochannels for water transport is a promising membrane material for desalination. SAPs with a high sulfonation degree favor water transport but suffer from reduced mechanical strength and membrane swelling. In this work, a hyperbranched polyester, H302, was introduced to crosslink a sulfonated styrene-ethylene/butylene-styrene (S-SEBS) copolymer membrane. The effects of crosslinking temperature and amount of H302 on the microstructure, and the pervaporation desalination performance of the membrane, were investigated. H302/S-SEBS copolymer membranes with different crosslinking conditions were characterized by various techniques including FTIR, DSC, EA, SEM, TEM and SAXS, and tensile strength, water sorption and contact angle measurements. The results indicate that the introduction of hyperbranched polyester enlarged the hydrophilic microdomain of the S-SEBS membrane. Crosslinking with hyperbranched polyester with heat treatment effectively enhanced the mechanical strength of the S-SEBS membrane, with the tensile strength being increased by 140–200% and the swelling ratio reduced by 45–70%, while reasonable water flux was maintained. When treating 5 wt% hypersaline water at 65 °C, the optimized crosslinked membrane containing 15 wt% H302 and heated at 100 °C reached a water flux of 9.3 kg·m⁻²·h⁻¹ and a salt rejection of 99.9%. The results indicate that the hyperbranched-S-SEBS membrane is promising for use in PV desalination. Full article

(This article belongs to the Special Issue Membranes for Water, Gas and Ion Separation)

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18 pages, 6057 KiB

Open AccessArticle

Performance Evaluation and Kinetic Analysis of Photocatalytic Membrane Reactor in Wastewater Treatment

by Zeyad Zeitoun, Ahmed H. El-Shazly, Shaaban Nosier, Mohamed R. Elmarghany, Mohamed S. Salem and Mahmoud M. Taha

Membranes 2020, 10(10), 276; https://doi.org/10.3390/membranes10100276 - 8 Oct 2020

Cited by 9 | Viewed by 3749

Abstract

The objectives of the current study are to assess and compare the performance of a developed photocatalytic membrane reactor (PMR) in treating industrial waste (e.g., organic dye waste) against membrane distillation. The current PMR is composed of a feed tank, which is a [...] Read more.

The objectives of the current study are to assess and compare the performance of a developed photocatalytic membrane reactor (PMR) in treating industrial waste (e.g., organic dye waste) against membrane distillation. The current PMR is composed of a feed tank, which is a continuous stirred photocatalytic reactor containing slurry Titanium dioxide (TiO₂) particles that are activated by using ultraviolet lamp irradiation at a wavelength of 365 nm, and a poly-vinylidene flouride (PVDF) membrane cell. The experimental setup was designed in a flexible way to enable both separate and integrated investigations of the photocatalytic reactor and the membrane, separately and simultaneously. The experimental work was divided into two phases. Firstly, the PVDF membrane was fabricated and characterized to examine its morphology, surface charge, and hydrophobicity by using a scanning electron microscope, surface zeta potential, and contact angle tests, respectively. Secondly, the effects of using different concentrations of the TiO₂ photocatalyst and feed (e.g., dye concentration) were examined. It is found that the PMR can achieve almost 100% dye removal and pure permeate is obtained at certain conditions. Additionally, a kinetic analysis was performed and revealed that the photocatalytic degradation of dye follows a pseudo-first-order reaction. Full article

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9 pages, 1291 KiB

Open AccessArticle

A Critical Study of the Effect of Polymeric Fibers on the Performance of Supported Liquid Membranes in Sample Microextraction for Metals Analysis

by Rafael J. González-Álvarez, José A. López-López, Juan J. Pinto and Carlos Moreno

Membranes 2020, 10(10), 275; https://doi.org/10.3390/membranes10100275 - 5 Oct 2020

Cited by 1 | Viewed by 2026

Abstract

Popularity of hollow fiber-supported liquid membranes (HF-SLM) for liquid-phase microextraction (HF-LPME) has increased in the last decades. In particular, HF-SLM are applied for sample treatment in the determination and speciation of metals. Up to the date, optimization of preconcentration systems has been focused [...] Read more.

Popularity of hollow fiber-supported liquid membranes (HF-SLM) for liquid-phase microextraction (HF-LPME) has increased in the last decades. In particular, HF-SLM are applied for sample treatment in the determination and speciation of metals. Up to the date, optimization of preconcentration systems has been focused on chemical conditions. However, criteria about fiber selection are not reflected in published works. HFs differ in pore size, porosity, wall thickness, etc., which can affect efficiency and/or selectivity of chemical systems in extraction of metals. In this work, Ag+ transport using tri-isobutylphosphine sulfide (TIBPS) has been used as a model to evaluate differences in metal transport due to the properties of three different fibers. Accurel PP 50/280 fibers, with a higher effective surface and smaller wall thickness, showed the highest efficiency for metal transport. Accurel PP Q3/2 exhibited intermediate efficiency but easier handling and, finally, Accurel PP S6/2 fibers, with a higher wall thickness, offered poorer efficiency but the highest stability and capability for metal speciation. Summarizing, selection of the polymeric support of HF-SLM is a key factor in their applicability of LPME for metals in natural waters. Full article

(This article belongs to the Special Issue Chemical Engineering and Membrane Solutions to Global Societal Challenges)

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12 pages, 1817 KiB

Open AccessArticle

Membranes for Modelling Cardiac Tissue Stiffness In Vitro Based on Poly(trimethylene carbonate) and Poly(ethylene glycol) Polymers

by Iris Allijn, Marcelo Ribeiro, André Poot, Robert Passier and Dimitrios Stamatialis

Membranes 2020, 10(10), 274; https://doi.org/10.3390/membranes10100274 - 3 Oct 2020

Cited by 15 | Viewed by 3113

Abstract

Despite the increased expenditure of the pharmaceutical industry on research and development, the number of drugs for cardiovascular diseases that reaches the market is decreasing. A major issue is the limited ability of the current in vitro and experimental animal models to accurately [...] Read more.

Despite the increased expenditure of the pharmaceutical industry on research and development, the number of drugs for cardiovascular diseases that reaches the market is decreasing. A major issue is the limited ability of the current in vitro and experimental animal models to accurately mimic human heart disease, which hampers testing of the efficacy of potential cardiac drugs. Moreover, many non-heart-related drugs have severe adverse cardiac effects, which is a major cause of drugs’ retraction after approval. A main hurdle of current in vitro models is their inability to mimic the stiffness of in vivo cardiac tissue. For instance, poly(styrene) petri dishes, which are often used in these models, have a Young’s modulus in the order of GPa, while the stiffness of healthy human heart tissue is <50 kPa. In pathological conditions, such as scarring and fibrosis, the stiffness of heart tissue is in the >100 kPa range. In this study, we focus on developing new membranes, with a set of properties for mimicry of cardiac tissue stiffness in vitro, based on methacrylate-functionalized macromers and triblock-copolymers of poly(trimethylene carbonate) and poly(ethylene glycol). The new membranes have Young’s moduli in the hydrated state ranging from 18 kPa (healthy tissue) to 2.5 MPa (pathological tissue), and are suitable for cell contraction studies using human pluripotent stem-cell-derived cardiomyocytes. The membranes with higher hydrophilicity have low drug adsorption and low Young’s moduli and could be suitable for drug screening applications. Full article

(This article belongs to the Special Issue Membrane Systems for Tissue Engineering 2020)

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Ring-opening polymerization and functionalization schematic for photo-crosslinkable macromers. (a) Hexanediol was used as an initiator for the ring-opening polymerization of trimethylene carbonate (TMC), resulting in two-armed poly-TMC (PTMC), which was functionalized with MAAh, giving PTMC-dMA. (b) Commercial polyethylene glycol (PEG) (Mn = 10 kg/mol) was used as an initiator for TMC polymerization, resulting in a triblock-copolymer, which subsequently was functionalized into PTMC-PEG-PTMC-dMA. (c) Commercial PEG (Mn = 10 kg/mol) was functionalized, resulting in PEG-dMA. Full article ">Figure 2
Mechanical properties and buffer uptake of the membranes. (a) Stress-strain curves of the membranes, with an inset of the first 300% strain. (b) Ashby plot of the Young’s modulus (bars, left Y-axis) vs. the buffer uptake (dots, right Y-axis) of the membranes. The dotted line indicates the maximum physiological stiffness of 50 kPa (c) Elongation at break of the membranes. * p < 0.05, ** p < 0.01, *** p < 0.001. Full article ">Figure 3
Verapamil adsorption to the membranes. (a) Chemical structure of verapamil hydrochloride and important physicochemical properties for drug development and adsorption studies. (b) Verapamil adsorption to the uncoated membranes and PDMS as control after 3 h. Data are the results of three experiments and depicted as mean ± SEM. Full article ">Figure 4
Cardiomyocyte (CM) contraction behavior and shape. (a) Degree of contraction of the CMs (bars, left Y-axis) in relation to the Young’s modulus (dots, right Y-axis) shows an increased contraction for a decreased Young’s modulus. (b) Cell-spreading circumference of the relaxed CMs is significantly lower for the stiff substrates glass and PTMC (M1). (c) Shape as defined by the CM circumferences. * p < 0.05, ** p < 0.01, *** p < 0.001 (<a href="#app1-membranes-10-00274" class="html-app">Supplementary Video</a>). Full article ">

31 pages, 3711 KiB

Open AccessReview

Vertically Aligned Carbon Nanotube Membranes: Water Purification and Beyond

by Jeong Hoon Lee, Han-Shin Kim, Eun-Tae Yun, So-Young Ham, Jeong-Hoon Park, Chang Hoon Ahn, Sang Hyup Lee and Hee-Deung Park

Membranes 2020, 10(10), 273; https://doi.org/10.3390/membranes10100273 - 2 Oct 2020

Cited by 18 | Viewed by 6483

Abstract

Vertically aligned carbon nanotube (VACNT) membranes have attracted significant attention for water purification owing to their ultra-high water permeability and antibacterial properties. In this paper, we critically review the recent progresses in the synthesis of VACNT arrays and fabrication of VACNT membrane methods, [...] Read more.

Vertically aligned carbon nanotube (VACNT) membranes have attracted significant attention for water purification owing to their ultra-high water permeability and antibacterial properties. In this paper, we critically review the recent progresses in the synthesis of VACNT arrays and fabrication of VACNT membrane methods, with particular emphasis on improving water permeability and anti-biofouling properties. Furthermore, potential applications of VACNT membranes other than water purification (e.g., conductive membranes, electrodes in proton exchange membrane fuel cells, and solar electricity–water generators) have been introduced. Finally, future outlooks are provided to overcome the limitations of commercialization and desalination currently faced by VACNT membranes. This review will be useful to researchers in the broader scientific community as it discusses current and new trends regarding the development of VACNT membranes as well as their potential applications. Full article

(This article belongs to the Special Issue Carbon-Based Nanocomposite Membranes)

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14 pages, 1683 KiB

Open AccessArticle

Hydration and Diffusion of H⁺, Li⁺, Na⁺, Cs⁺ Ions in Cation-Exchange Membranes Based on Polyethylene- and Sulfonated-Grafted Polystyrene Studied by NMR Technique and Ionic Conductivity Measurements

by Vitaliy I. Volkov, Alexander V. Chernyak, Daniil V. Golubenko, Vladimir A. Tverskoy, Georgiy A. Lochin, Ervena S. Odjigaeva and Andrey B. Yaroslavtsev

Membranes 2020, 10(10), 272; https://doi.org/10.3390/membranes10100272 - 1 Oct 2020

Cited by 23 | Viewed by 4416

Abstract

The main particularities of sulfonate groups hydration, water molecule and alkaline metal cation translation mobility as well as ionic conductivity were revealed by NMR and impedance spectroscopy techniques. Cation-exchange membranes MSC based on cross-linked sulfonated polystyrene (PS) grafted on polyethylene with ion-exchange capacity [...] Read more.

The main particularities of sulfonate groups hydration, water molecule and alkaline metal cation translation mobility as well as ionic conductivity were revealed by NMR and impedance spectroscopy techniques. Cation-exchange membranes MSC based on cross-linked sulfonated polystyrene (PS) grafted on polyethylene with ion-exchange capacity of 2.5 mg-eq/g were investigated. Alkaline metal cation hydration numbers (h) calculated from temperature dependences of ¹H chemical shift of water molecule for membranes equilibrated with water vapor at RH = 95% are 5, 6, and 4 for Li⁺, Na⁺, and Cs⁺ ions, respectively. These values are close to h for equimolar aqueous salt solutions. Water molecules and counter ions Li⁺, Na⁺, and Cs⁺ diffusion coefficients were measured by pulsed field gradient NMR on the ¹H, ⁷Li, ²³Na, and ¹³³Cs nuclei. For membranes as well as for aqueous chloride solutions, cation diffusion coefficients increased in the following sequence: Li⁺ < Na⁺ < Cs⁺. Cation and water molecule diffusion activation energies in temperature range from 20 °C to 80 °C were close to each other (about 20 kJ/mol). The cation conductivity of MSC membranes is in the same sequence, Li⁺ < Na⁺ < Cs⁺ << H⁺. The conductivity values calculated from the NMR diffusion coefficients with the use of the Nernst–Einstein equation are essentially higher than experimentally determined coefficients. The reason for this discrepancy is the heterogeneity of membrane pore and channel system. Ionic conductivity is limited by cation transfer in narrow channels, whereas the diffusion coefficient characterizes ion mobility in wide pores first of all. Full article

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

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14 pages, 2259 KiB

Open AccessArticle

An Efficient Method to Determine Membrane Molecular Weight Cut-Off Using Fluorescent Silica Nanoparticles

by Mariam Fadel, Yvan Wyart and Philippe Moulin

Membranes 2020, 10(10), 271; https://doi.org/10.3390/membranes10100271 - 1 Oct 2020

Cited by 6 | Viewed by 4480

Abstract

Membrane processes have revolutionized many industries because they are more energy and environmentally friendly than other separation techniques. This initial selection of the membrane for any application is based on its Molecular Weight Cut-Off (MWCO). However, there is a lack of a quantitative, [...] Read more.

Membrane processes have revolutionized many industries because they are more energy and environmentally friendly than other separation techniques. This initial selection of the membrane for any application is based on its Molecular Weight Cut-Off (MWCO). However, there is a lack of a quantitative, liable, and rapid method to determine the MWCO of the membrane. In this study, a methodology to determine the MWCO, based on the retention of fluorescent silica nanoparticles (NPs), is presented. Optimized experimental conditions (Transmembrane pressure, filtration duration, suspension concentration, etc.) have been performed on different membranes MWCO. Filtrations with suspension of fluorescent NPs of different diameters 70, 100, 200 and 300 nm have been examined. The NPs sizes were selected to cover a wide range in order to study NPs diameters larger, close to, and smaller than the membrane pore size. A particle tracking analysis with a nanosight allows us to calculate the retention curves at all times. The retention rate curves were shifted over the filtration process at different times due to the fouling. The mechanism of fouling of the retained NPs explains the determined value of the MWCO. The reliability of this methodology, which presents a rapid quantitative way to determine the MWCO, is in good agreement with the value given by the manufacturer. In addition, this methodology gives access to the retention curve and makes it possible to determine the MWCO as a function of the desired retention rate. Full article

(This article belongs to the Special Issue Membranes: 10th Anniversary)

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