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Membranes
Volume 11
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Membranes, Volume 11, Issue 6 (June 2021) – 82 articles

Cover Story (view full-size image): The reverse electrodialysis unit's operating parameters depend on the design of the module, solutions that are used, and the characteristics of the membranes. One of the main characteristics of the ion-exchange membranes that define the effectiveness of their application in reverse electrodialysis is permselectivity. In the paper, we used the microheterogeneous model to calculate the heterogeneous ion-exchange membranes' selectivity based on data from conductivity and diffusion permeability. The calculated values of the net power density and open-circuit voltage are compared with experimental data obtained on the lab-scale RED module. View this paper
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15 pages, 1598 KiB  
Review
Review: Mixed-Matrix Membranes with CNT for CO2 Separation Processes
by Marquidia J. Pacheco, Luis J. Vences, Hilda Moreno, Joel O. Pacheco, Ricardo Valdivia and Celso Hernández
Membranes 2021, 11(6), 457; https://doi.org/10.3390/membranes11060457 - 21 Jun 2021
Cited by 22 | Viewed by 4192
Abstract
The membranes’ role is of supreme importance in the separation of compounds under different phases of matter. The topic addressed here is based on the use of membranes on the gases separation, specifically the advantages of mixed-matrix membranes (MMMs) when using carbon nanotubes [...] Read more.
The membranes’ role is of supreme importance in the separation of compounds under different phases of matter. The topic addressed here is based on the use of membranes on the gases separation, specifically the advantages of mixed-matrix membranes (MMMs) when using carbon nanotubes as fillers to separate carbon dioxide (CO2) from other carrier gas. MMMs consist of a polymer support with additive fillers to improve their efficiency by increasing both selectivity and permeability. The most promising fillers in the MMM development are nanostructured molecules. Due to the good prospects of carbon nanotubes (CNTs) as MMM fillers, this article aims to concentrate the advances and developments of CNT–MMM to separate gases, such as CO2. The influence of functionalized CNT or mixtures of CNT with additional materials such as zeolites, hydrogel and, graphene sheets on membranes performance is highlighted in the present work. Full article
(This article belongs to the Special Issue Membranes for Gas Separation and Purification Processes)
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17 pages, 1992 KiB  
Article
Treatment of Wastewater from a Food and Beverage Industry Using Conventional Wastewater Treatment Integrated with Membrane Bioreactor System: A Pilot-Scale Case Study
by Sabrina Ng Muhamad Ng, Syazwani Idrus, Amimul Ahsan, Tuan Nurfarhana Tuan Mohd Marzuki and Siti Baizura Mahat
Membranes 2021, 11(6), 456; https://doi.org/10.3390/membranes11060456 - 21 Jun 2021
Cited by 17 | Viewed by 7441
Abstract
This study compares the performance of the Hollow Fiber (HF) and Flat Sheet (FS) types of membrane bioreactors (MBRs) for the treatment of food and beverage (F&B) industry wastewater in a pilot-scale study of a wastewater treatment plant (WWTP). HF and FS membrane [...] Read more.
This study compares the performance of the Hollow Fiber (HF) and Flat Sheet (FS) types of membrane bioreactors (MBRs) for the treatment of food and beverage (F&B) industry wastewater in a pilot-scale study of a wastewater treatment plant (WWTP). HF and FS membrane configurations were evaluated at two different Mixed Liquor Suspended Solid (MLSS) levels: 6000 mg/L and 12,000 mg/L. The performance of each configuration was evaluated in terms of Chemical Oxygen Demand (COD) and Total Suspended Solid (TSS) removals for effluent quality measurement. The transmembrane pressure (TMP), flux rate, and silt density index (SDI) were monitored and calculated for membrane fouling assessment. The results show that the rejection rates of COD and TSS for HF and FS membrane types were more than 84% for the two different MLSS levels. During the study, the HF membrane recorded 0.3 bar transmembrane pressure, which complies with the recommended range (i.e., two to three times of chemical cleaning). On the other hand, the FS membrane operates without chemical cleaning, and the TMP value was below the recommended range at 0.2 bar. It was found that the flux values recorded for both the HF and FS systems were within the recommended range of 40 L/m2/h. Analysis of SDI revealed that the calculated index ranged between 1 and 2.38 and was within the allowable limit of 3. Both types of MBR consistently achieved an 80% to 95% rejection rate of COD and TSS. Effluent quality measurement of treated F&B wastewater in this pilot-scale study using a WWTP integrated with an MBR indicated a good achievement with compliance with the Malaysia industrial effluent discharge standards. Full article
(This article belongs to the Special Issue Membrane Processes for the Metal-ion/Pollutants Detection on Water and Treatment of Industrial Wastewaters)
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24 pages, 2724 KiB  
Review
Recent Advances of Pervaporation Separation in DMF/H2O Solutions: A Review
by Zongqi Zhang, Siquan Xu, Yuanfeng Wu, Shengbin Shi and Guomin Xiao
Membranes 2021, 11(6), 455; https://doi.org/10.3390/membranes11060455 - 20 Jun 2021
Cited by 16 | Viewed by 5345
Abstract
N,N-dimethylformamide (DMF) is a commonly-used solvent in industry and pharmaceutics for extracting acetylene and fabricating polyacrylonitrile fibers. It is also a starting material for a variety of intermediates such as esters, pyrimidines or chlordimeforms. However, after being used, DMF can be form 5–25% [...] Read more.
N,N-dimethylformamide (DMF) is a commonly-used solvent in industry and pharmaceutics for extracting acetylene and fabricating polyacrylonitrile fibers. It is also a starting material for a variety of intermediates such as esters, pyrimidines or chlordimeforms. However, after being used, DMF can be form 5–25% spent liquors (mass fraction) that are difficult to recycle with distillation. From the point of view of energy-efficiency and environment-friendliness, an emergent separation technology, pervaporation, is broadly applied in separation of azeotropic mixtures and organic–organic mixtures, dehydration of aqueous–organic mixtures and removal of trace volatile organic compounds from aqueous solutions. Since the advances in membrane technologies to separate N,N-dimethylformamide solutions have been rarely reviewed before, hence this review mainly discusses the research progress about various membranes in separating N,N-dimethylformamide aqueous solutions. The current state of available membranes in industry and academia, and their potential advantages, limitations and applications are also reviewed. Full article
(This article belongs to the Special Issue Recent Advances in Membrane Materials and Membrane Processes for Water and Wastewater Treatment)
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22 pages, 4226 KiB  
Article
Phenolphthalein Anilide Based Poly(Ether Sulfone) Block Copolymers Containing Quaternary Ammonium and Imidazolium Cations: Anion Exchange Membrane Materials for Microbial Fuel Cell
by Aruna Kumar Mohanty, Young Eun Song, Jung Rae Kim, Nowon Kim and Hyun-jong Paik
Membranes 2021, 11(6), 454; https://doi.org/10.3390/membranes11060454 - 20 Jun 2021
Cited by 6 | Viewed by 3207
Abstract
A class of phenolphthalein anilide (PA)-based poly(ether sulfone) multiblock copolymers containing pendant quaternary ammonium (QA) and imidazolium (IM) groups were synthesized and evaluated as anion exchange membrane (AEM) materials. The AEMs were flexible and mechanically strong with good thermal stability. The ionomeric multiblock [...] Read more.
A class of phenolphthalein anilide (PA)-based poly(ether sulfone) multiblock copolymers containing pendant quaternary ammonium (QA) and imidazolium (IM) groups were synthesized and evaluated as anion exchange membrane (AEM) materials. The AEMs were flexible and mechanically strong with good thermal stability. The ionomeric multiblock copolymer AEMs exhibited well-defined hydrophobic/hydrophilic phase-separated morphology in small-angle X-ray scattering and atomic force microscopy. The distinct nanophase separated membrane morphology in the AEMs resulted in higher conductivity (IECw = 1.3–1.5 mequiv./g, σ(OH−) = 30–38 mS/cm at 20 °C), lower water uptake and swelling. Finally, the membranes were compared in terms of microbial fuel cell performances with the commercial cation and anion exchange membranes. The membranes showed a maximum power density of ~310 mW/m2 (at 0.82 A/m2); 1.7 and 2.8 times higher than the Nafion 117 and FAB-PK-130 membranes, respectively. These results demonstrated that the synthesized AEMs were superior to Nafion 117 and FAB-PK-130 membranes. Full article
(This article belongs to the Special Issue Applied Ion-Exchange Membrane Technologies for Sustainable Energy Production)
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15 pages, 1111 KiB  
Review
Extracellular Vesicles in Cervical Cancer and HPV Infection
by Víctor Acevedo-Sánchez, Ruth M. Rodríguez-Hernández, Sergio R. Aguilar-Ruíz, Honorio Torres-Aguilar and María de los A. Romero-Tlalolini
Membranes 2021, 11(6), 453; https://doi.org/10.3390/membranes11060453 - 20 Jun 2021
Cited by 20 | Viewed by 4159
Abstract
Since their description, extracellular vesicles (EVs) have shown growing relevance in cancer progression. These cell structures contain and transfer molecules such as nucleic acids (including DNA and RNA), proteins, and lipids. Despite the rising information about EVs’ relationship with cancer, there is still [...] Read more.
Since their description, extracellular vesicles (EVs) have shown growing relevance in cancer progression. These cell structures contain and transfer molecules such as nucleic acids (including DNA and RNA), proteins, and lipids. Despite the rising information about EVs’ relationship with cancer, there is still scarce evidence about their content and function in cervical cancer. Interestingly, the composition and purposes of some cellular molecules and the expression of oncogenic proteins packaged in EVs seem modified in HPV-infected cells; and, although only the E6 oncogenic protein has been detected in exosomes from HPV-positive cells, both E6/E7 oncogenes mRNA has been identified in EVs; however, their role still needs to be clarified. Given that EVs internalizing into adjacent or distant cells could modify their cellular behavior or promote cancer-associated events like apoptosis, proliferation, migration, or angiogenesis in receptor cells, their comprehensive study will reveal EV-associated mechanisms in cervical cancer. This review summarizes the current knowledge in composition and functions of cervical cancer and HPV Infection-derived EVs. Full article
(This article belongs to the Special Issue Cell Membrane Vesicles)
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13 pages, 2675 KiB  
Article
Ionic Transport Properties of Cation-Exchange Membranes Prepared from Poly(vinyl alcohol-b-sodium Styrene Sulfonate)
by Yuriko Kakihana, N. Awanis Hashim, Taiko Mizuno, Marika Anno and Mitsuru Higa
Membranes 2021, 11(6), 452; https://doi.org/10.3390/membranes11060452 - 19 Jun 2021
Cited by 4 | Viewed by 2923
Abstract
Membrane resistance and permselectivity for counter-ions have important roles in determining the performance of cation-exchange membranes (CEMs). In this study, PVA-based polyanions—poly(vinyl alcohol-b-sodium styrene sulfonate)—were synthesized, changing the molar percentages CCEG of the cation-exchange groups with respect to the vinyl [...] Read more.
Membrane resistance and permselectivity for counter-ions have important roles in determining the performance of cation-exchange membranes (CEMs). In this study, PVA-based polyanions—poly(vinyl alcohol-b-sodium styrene sulfonate)—were synthesized, changing the molar percentages CCEG of the cation-exchange groups with respect to the vinyl alcohol groups. From the block copolymer, poly(vinyl alcohol) (PVA)-based CEMs, hereafter called “B-CEMs”, were prepared by crosslinking the PVA chains with glutaraldehyde (GA) solution at various GA concentrations CGA. The ionic transport properties of the B-CEMs were compared with those previously reported for the CEMs prepared using a random copolymer—poly(vinyl alcohol-co-2-acrylamido-2-methylpropane sulfonic acid)—hereafter called ”R-CEMs”. The B-CEMs had lower water content than the R-CEMs at equal molar percentages of the cation-exchange groups. The charge density of the B-CEMs increased as CCEG increased, and reached a maximum value, which increased with increasing CGA. A maximum charge density of 1.47 mol/dm3 was obtained for a B-CEM with CCEG = 2.9 mol% and CGA = 0.10 vol.%, indicating that the B-CEM had almost two-thirds of the permselectivity of a commercial CEM (CMX: ASTOM Corp. Japan). The dynamic transport number and membrane resistance of a B-CEM with CCEG = 8.3 mol% and CGA = 0.10 vol.% were 0.99 and 1.6 Ωcm2, respectively. The B-CEM showed higher dynamic transport numbers than those of the R-CEMs with similar membrane resistances. Full article
(This article belongs to the Special Issue Novel Ion-Exchange Membranes)
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20 pages, 4935 KiB  
Review
Structures and Dynamics of Native-State Transmembrane Protein Targets and Bound Lipids
by Michael Overduin, Catharine Trieber, R. Scott Prosser, Louis-Philippe Picard and Joey G. Sheff
Membranes 2021, 11(6), 451; https://doi.org/10.3390/membranes11060451 - 17 Jun 2021
Cited by 13 | Viewed by 4875
Abstract
Membrane proteins work within asymmetric bilayers of lipid molecules that are critical for their biological structures, dynamics and interactions. These properties are lost when detergents dislodge lipids, ligands and subunits, but are maintained in native nanodiscs formed using styrene maleic acid (SMA) and [...] Read more.
Membrane proteins work within asymmetric bilayers of lipid molecules that are critical for their biological structures, dynamics and interactions. These properties are lost when detergents dislodge lipids, ligands and subunits, but are maintained in native nanodiscs formed using styrene maleic acid (SMA) and diisobutylene maleic acid (DIBMA) copolymers. These amphipathic polymers allow extraction of multicomponent complexes of post-translationally modified membrane-bound proteins directly from organ homogenates or membranes from diverse types of cells and organelles. Here, we review the structures and mechanisms of transmembrane targets and their interactions with lipids including phosphoinositides (PIs), as resolved using nanodisc systems and methods including cryo-electron microscopy (cryo-EM) and X-ray diffraction (XRD). We focus on therapeutic targets including several G protein-coupled receptors (GPCRs), as well as ion channels and transporters that are driving the development of next-generation native nanodiscs. The design of new synthetic polymers and complementary biophysical tools bodes well for the future of drug discovery and structural biology of native membrane:protein assemblies (memteins). Full article
(This article belongs to the Special Issue Analytical Sciences Of / With Bio(mimetic) Membranes)
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13 pages, 3783 KiB  
Article
Preparation and Characterization of a Novel Sulfonated Titanium Oxide Incorporated Chitosan Nanocomposite Membranes for Fuel Cell Application
by Saad Ahmed, Tasleem Arshad, Amir Zada, Annum Afzal, Muhammad Khan, Amjad Hussain, Muhammad Hassan, Muhammad Ali and Shiai Xu
Membranes 2021, 11(6), 450; https://doi.org/10.3390/membranes11060450 - 17 Jun 2021
Cited by 38 | Viewed by 3949
Abstract
In this study, nano-TiO2 sulfonated with 1,3-propane sultone (STiO2) was incorporated into the chitosan (CS) matrix for the preparation of CS/STiO2 nanocomposite membranes for fuel cell applications. The grafting of sulfonic acid (–SO3H) groups was confirmed by [...] Read more.
In this study, nano-TiO2 sulfonated with 1,3-propane sultone (STiO2) was incorporated into the chitosan (CS) matrix for the preparation of CS/STiO2 nanocomposite membranes for fuel cell applications. The grafting of sulfonic acid (–SO3H) groups was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis and energy-dispersive X-ray spectroscopy. The physicochemical properties of these prepared membranes, such as water uptake, swelling ratio, thermal and mechanical stability, ion exchange capacity and proton conductivity, were determined. The proton conducting groups on the surface of nano-TiO2 can form continuous proton conducting pathways along the CS/STiO2 interface and thus improve the proton conductivity of CS/STiO2 nanocomposite membranes. The CS/STiO2 nanocomposite membrane with 5 wt% of sulfonated TiO2 showed a proton conductivity (0.035 S·cm−1) equal to that of commercial Nafion 117 membrane (0.033 S·cm−1). The thermal and mechanical stability of the nanocomposite membranes were improved because the interfacial interaction between the -SO3H group of TiO2 and the –NH2 group of CS can restrict the mobility of CS chains to enhance the thermal and mechanical stability of the nanocomposite membranes. These CS/STiO2 nanocomposite membranes have promising applications in proton exchange membrane fuel cells. Full article
(This article belongs to the Special Issue Flexible Membranes for Batteries and Supercapacitor Applications)
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14 pages, 2398 KiB  
Article
A Study of the Interaction of a New Benzimidazole Schiff Base with Synthetic and Simulated Membrane Models of Bacterial and Mammalian Membranes
by Alberto Aragón-Muriel, Yamil Liscano, David Morales-Morales, Dorian Polo-Cerón and Jose Oñate-Garzón
Membranes 2021, 11(6), 449; https://doi.org/10.3390/membranes11060449 - 16 Jun 2021
Cited by 6 | Viewed by 3594
Abstract
Biological membranes are complex dynamic systems composed of a great variety of carbohydrates, lipids, and proteins, which together play a pivotal role in the protection of organisms and through which the interchange of different substances is regulated in the cell. Given the complexity [...] Read more.
Biological membranes are complex dynamic systems composed of a great variety of carbohydrates, lipids, and proteins, which together play a pivotal role in the protection of organisms and through which the interchange of different substances is regulated in the cell. Given the complexity of membranes, models mimicking them provide a convenient way to study and better understand their mechanisms of action and their interactions with biologically active compounds. Thus, in the present study, a new Schiff base (Bz-Im) derivative from 2-(m-aminophenyl)benzimidazole and 2,4-dihydroxybenzaldehyde was synthesized and characterized by spectroscopic and spectrometric techniques. Interaction studies of (Bz-Im) with two synthetic membrane models prepared with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and DMPC/1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) 3:1 mixture, imitating eukaryotic and prokaryotic membranes, respectively, were performed by applying differential scanning calorimetry (DSC). Molecular dynamics simulations were also developed to better understand their interactions. In vitro and in silico assays provided approaches to understand the effect of Bz-Im on these lipid systems. The DSC results showed that, at low compound concentrations, the effects were similar in both membrane models. By increasing the concentration of Bz-Im, the DMPC/DMPG membrane exhibited greater fluidity as a result of the interaction with Bz-Im. On the other hand, molecular dynamics studies carried out on the erythrocyte membrane model using the phospholipids POPE (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine), SM (N-(15Z-tetracosenoyl)-sphing-4-enine-1-phosphocholine), and POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) revealed that after 30 ns of interaction, both hydrophobic interactions and hydrogen bonds were responsible for the affinity of Bz-Im for PE and SM. The interactions of the imine with POPG (1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphoglycerol) in the E. coli membrane model were mainly based on hydrophobic interactions. Full article
(This article belongs to the Special Issue Modeling and Simulation of Lipid Membranes)
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18 pages, 8784 KiB  
Article
Improving the Structural Parameter of the Membrane Sublayer for Enhanced Forward Osmosis
by Jin Fei Sark, Nora Jullok and Woei Jye Lau
Membranes 2021, 11(6), 448; https://doi.org/10.3390/membranes11060448 - 15 Jun 2021
Cited by 14 | Viewed by 3683
Abstract
The structural (S) parameter of a medium is used to represent the mass transport resistance of an asymmetric membrane. In this study, we aimed to fabricate a membrane sublayer using a novel composition to improve the S parameter for enhanced forward [...] Read more.
The structural (S) parameter of a medium is used to represent the mass transport resistance of an asymmetric membrane. In this study, we aimed to fabricate a membrane sublayer using a novel composition to improve the S parameter for enhanced forward osmosis (FO). Thin film composite (TFC) membranes using polyamide (PA) as an active layer and different polysulfone:polyethersulfone (PSf:PES) supports as sublayers were prepared via the phase inversion technique, followed by interfacial polymerization. The membrane made with a PSf:PES ratio of 2:3 was observed to have the lowest contact angle (CA) with the highest overall porosity. It also had the highest water permeability (A; 3.79 ± 1.06 L m−2 h−1 bar−1) and salt permeability (B; 8.42 ± 2.34 g m−2 h−1), as well as a good NaCl rejection rate of 74%. An increase in porosity at elevated temperatures from 30 to 40 °C decreased Sint from 184 ± 4 to 159 ± 2 μm. At elevated temperatures, significant increases in the water flux from 13.81 to 42.86 L m−2 h−1 and reverse salt flux (RSF) from 12.74 to 460 g m−2 h−1 occur, reducing Seff from 152 ± 26 to 120 ± 14 μm. Sint is a temperature-dependent parameter, whereas Seff can only be reduced in a high-water- permeability membrane at elevated temperatures. Full article
(This article belongs to the Special Issue Membrane Development for Pervaporation and Vapor Permeation Processes)
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27 pages, 10791 KiB  
Review
Association of Alpha-Crystallin with Fiber Cell Plasma Membrane of the Eye Lens Accompanied by Light Scattering and Cataract Formation
by Raju Timsina and Laxman Mainali
Membranes 2021, 11(6), 447; https://doi.org/10.3390/membranes11060447 - 15 Jun 2021
Cited by 15 | Viewed by 6451
Abstract
α-crystallin is a major protein found in the mammalian eye lens that works as a molecular chaperone by preventing the aggregation of proteins and providing tolerance to stress in the eye lens. These functions of α-crystallin are significant for maintaining lens transparency. However, [...] Read more.
α-crystallin is a major protein found in the mammalian eye lens that works as a molecular chaperone by preventing the aggregation of proteins and providing tolerance to stress in the eye lens. These functions of α-crystallin are significant for maintaining lens transparency. However, with age and cataract formation, the concentration of α-crystallin in the eye lens cytoplasm decreases with a corresponding increase in the membrane-bound α-crystallin, accompanied by increased light scattering. The purpose of this review is to summarize previous and recent findings of the role of the: (1) lens membrane components, i.e., the major phospholipids (PLs) and sphingolipids, cholesterol (Chol), cholesterol bilayer domains (CBDs), and the integral membrane proteins aquaporin-0 (AQP0; formally MIP26) and connexins, and (2) α-crystallin mutations and post-translational modifications (PTMs) in the association of α-crystallin to the eye lens’s fiber cell plasma membrane, providing thorough insights into a molecular basis of such an association. Furthermore, this review highlights the current knowledge and need for further studies to understand the fundamental molecular processes involved in the association of α-crystallin to the lens membrane, potentially leading to new avenues for preventing cataract formation and progression. Full article
(This article belongs to the Special Issue Protein-Lipid Interactions as Key Regulators of Cell Function)
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16 pages, 1463 KiB  
Article
Aminophosphonates in Nanofiltration and Reverse Osmosis Permeates
by Ramona Kuhn, Carsten Vornholt, Volker Preuß, Isaac Mbir Bryant and Marion Martienssen
Membranes 2021, 11(6), 446; https://doi.org/10.3390/membranes11060446 - 15 Jun 2021
Cited by 4 | Viewed by 3394
Abstract
Aminophosphonates such as aminotris(methylenephosphonic acid) (ATMP) are common constituents of antiscalants. In nanofiltration (NF) and reverse osmosis (RO) processes, ATMP prevents inorganic scaling leading to more stable membrane performance. So far, little attention has been paid to the possible permeation of aminophosphonates through [...] Read more.
Aminophosphonates such as aminotris(methylenephosphonic acid) (ATMP) are common constituents of antiscalants. In nanofiltration (NF) and reverse osmosis (RO) processes, ATMP prevents inorganic scaling leading to more stable membrane performance. So far, little attention has been paid to the possible permeation of aminophosphonates through NF and RO membranes. We have investigated the permeability of these membrane types for ATMP and its potential metabolites iminodi(methylenephosphonic acid) (IDMP) and amino(methylenephosphonic acid) (AMPA) with two different NF membranes (TS40 and TS80) and one RO membrane (ACM2) and three different water compositions (ultra-pure water, synthetic tap water and local tap water). We found traces of phosphonates in all investigated permeates. The highest phosphonate rejection occurred with local tap water for all three membranes investigated. Filtration experiments with a technical antiscalant formulation containing ATMP indicated similar trends of phosphonate permeability through all three membranes. We assume that the separation mechanisms of the membranes are the results of a very complex relationship between physico-chemical properties such as Donnan exclusion, feed pH, feed ionic strength and feed concentration, as well as solute–solute interactions. Full article
(This article belongs to the Special Issue A Commemorative Issue in Honor of Victor Starov: Influence of Surface Forces on Membrane Separations)
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20 pages, 7982 KiB  
Article
Improving the Performance of Composite Hollow Fiber Membranes with Magnetic Field Generated Convection Application on pH Correction
by Aurelia Cristina Nechifor, Alexandru Goran, Vlad-Alexandru Grosu, Constantin Bungău, Paul Constantin Albu, Alexandra Raluca Grosu, Ovidiu Oprea, Florentina Mihaela Păncescu and Gheorghe Nechifor
Membranes 2021, 11(6), 445; https://doi.org/10.3390/membranes11060445 - 15 Jun 2021
Cited by 20 | Viewed by 3265
Abstract
The membranes and membrane processes have succeeded in the transition from major technological and biomedical applications to domestic applications: water recycling in washing machines, recycling of used cooking oil, recovery of gasoline vapors in the pumping stations or enrichment of air with oxygen. [...] Read more.
The membranes and membrane processes have succeeded in the transition from major technological and biomedical applications to domestic applications: water recycling in washing machines, recycling of used cooking oil, recovery of gasoline vapors in the pumping stations or enrichment of air with oxygen. In this paper, the neutralization of condensation water and the retention of aluminum from thermal power plants is studied using ethylene propylene diene monomer sulfonated (EPDM-S) membranes containing magnetic particles impregnated in a microporous propylene hollow fiber (I-PPM) matrix. The obtained membranes were characterized from the morphological and structural points of view, using scanning electron microscopy (SEM), high resolution SEM (HR-SEM), energy dispersive spectroscopy analysis (EDAX) and thermal gravimetric analyzer. The process performances (flow, selectivity) were studied using a variable magnetic field generated by electric coils. The results show the possibility of correcting the pH and removing aluminum ions from the condensation water of heating plants, during a winter period, without the intervention of any operator for the maintenance of the process. The pH was raised from an acidic one (2–4), to a slightly basic one (8–8.5), and the concentration of aluminum ions was lowered to the level allowed for discharge. Magnetic convection of the permeation module improves the pH correction process, but especially prevents the deposition of aluminum hydroxide on hollow fibers membranes. Full article
(This article belongs to the Collection Polymeric Membranes: Science, Materials and Applications)
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14 pages, 926 KiB  
Article
Lanolin-Based Synthetic Membranes for Transdermal Permeation and Penetration Drug Delivery Assays
by Cristina Alonso, Ilaria Collini, Meritxell Martí, Clara Barba and Luisa Coderch
Membranes 2021, 11(6), 444; https://doi.org/10.3390/membranes11060444 - 15 Jun 2021
Cited by 2 | Viewed by 2960
Abstract
Due to the high similarity in composition and structure between lanolin and human SC lipids, we will work with two models from wool wax. Two types of lanolin were evaluated: one extracted with water and surfactants (WEL) and the other extracted with organic [...] Read more.
Due to the high similarity in composition and structure between lanolin and human SC lipids, we will work with two models from wool wax. Two types of lanolin were evaluated: one extracted with water and surfactants (WEL) and the other extracted with organic solvents (SEL). Skin permeation and skin penetration studies were performed with two active compounds to study the feasibility of the use of lanolin-based synthetic membranes as models of mammalian skin. Diclofenac sodium and lidocaine were selected as the active compounds considering that they have different chemical natures and different lipophilicities. In the permeation assay with SEL, a better correlation was obtained with the less permeable compound diclofenac sodium. This assay suggests the feasibility of using artificial membranes with SEL as a model for percutaneous absorption studies, even though the lipophilic barrier should be improved. Penetration profiles of the APIs through the SEL and WEL membranes indicated that the two membranes diminish penetration and can be considered good membrane surrogates for skin permeability studies. However, the WEL membranes, with a pH value similar to that of the skin surface, promoted a higher degree of diminution of the permeability of the two drugs, similar to those found for the skin. Full article
(This article belongs to the Special Issue Functionalized and Composite Polymeric Membranes for Biomedical Applications)
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14 pages, 2960 KiB  
Article
Biochar/Kevlar Nanofiber Mixed Matrix Nanofiltration Membranes with Enhanced Dye/Salt Separation Performance
by Shiguo Gu, Lei Li, Fei Liu and Jian Li
Membranes 2021, 11(6), 443; https://doi.org/10.3390/membranes11060443 - 12 Jun 2021
Cited by 13 | Viewed by 3778
Abstract
Mixed matrix membranes have received ever-growing attention due to their high separation performance, taking the advantages of both porous fillers and polymer backbones. However, limitations still exist due to the instability of polymers in harsh environments. Here, Kevlar aramid nanofibers, a nanoscale version [...] Read more.
Mixed matrix membranes have received ever-growing attention due to their high separation performance, taking the advantages of both porous fillers and polymer backbones. However, limitations still exist due to the instability of polymers in harsh environments. Here, Kevlar aramid nanofibers, a nanoscale version of poly(paraphenylene terephthalamide), were applied to fabricate a nanofiltration membrane by a thermo-assisted phase inversion method due to their high mechanical strength, physical stability and resistance to solvents. Biochar was incorporated in the Kevlar nanofibers to evaluate its performance in dye/salt separation performance. The fillers’ distribution in the polymeric matrix, structural characteristics, and the interaction of fillers with the polymer in the membrane were characterized via SEM, FTIR, AFM and contact angle analysis. Under the optimal fabrication conditions, the obtained membrane exhibited a pure water flux of 3.83 L m−2 h−1 bar−1 with a dye rejection of 90.55%, 93.54% and 95.41% for Congo red, methyl blue and Reactive blue 19, respectively. Meanwhile, the mixed matrix membrane maintained a salt rejection of 59.92% and 85.37% for NaCl and Na2SO4, respectively. The obtained membrane with high separation performance suggested that Kevlar nanofiber and biochar are good candidates for membrane synthesis. Full article
(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)
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14 pages, 3306 KiB  
Article
Effect of Mobile Carrier on the Performance of PVAm–Nanocellulose Facilitated Transport Membranes for CO2 Capture
by Riccardo Casadei, Elham Firouznia and Marco Giacinti Baschetti
Membranes 2021, 11(6), 442; https://doi.org/10.3390/membranes11060442 - 12 Jun 2021
Cited by 13 | Viewed by 3595
Abstract
Facilitated transport membranes obtained by coupling polyvinylamine with highly charged carboxymethylated nanocellulose fibers were studied considering both water sorption and gas permeation experiments. In particular, the effect of the L-arginine as a mobile carrier was investigated to understand possible improvements in CO2 [...] Read more.
Facilitated transport membranes obtained by coupling polyvinylamine with highly charged carboxymethylated nanocellulose fibers were studied considering both water sorption and gas permeation experiments. In particular, the effect of the L-arginine as a mobile carrier was investigated to understand possible improvements in CO2 transport across the membranes. The results show that L-arginine addition decreases the water uptake of the membrane, due to the lower polyvinylamine content, but was able to improve the CO2 transport. Tests carried on at 35 °C and high relative humidity indeed showed an increase of both CO2 permeability and selectivity with respect to nitrogen and methane. In particular, the CO2 permeability increased from 160 to about 340 Barrer when arginine loading was increased from 0 to 45 wt%. In the same conditions, selectivity with respect to nitrogen was more than doubled, increasing from 20 to 45. Minor improvements were instead obtained with respect to methane; CO2/CH4 selectivity, indeed, even in presence of the mobile carrier, was limited to about 20. Full article
(This article belongs to the Special Issue Facilitated Transport Membranes for Gas Separations)
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36 pages, 3620 KiB  
Review
A Review on Mixed Matrix Membranes for Solvent Dehydration and Recovery Process
by Priyanka Goyal, Subramanian Sundarrajan and Seeram Ramakrishna
Membranes 2021, 11(6), 441; https://doi.org/10.3390/membranes11060441 - 11 Jun 2021
Cited by 17 | Viewed by 5300
Abstract
Solvent separation and dehydration are important operations for industries and laboratories. Processes such as distillation and extraction are not always effective and are energy-consuming. An alternate approach is offered by pervaporation, based on the solution-diffusion transport mechanism. Polymer-based membranes such as those made [...] Read more.
Solvent separation and dehydration are important operations for industries and laboratories. Processes such as distillation and extraction are not always effective and are energy-consuming. An alternate approach is offered by pervaporation, based on the solution-diffusion transport mechanism. Polymer-based membranes such as those made of Polydimethylsiloxane (PDMS) have offered good pervaporation performance. Attempts have been made to improve their performance by incorporating inorganic fillers into the PDMS matrix, in which metal-organic frameworks (MOFs) have proven to be the most efficient. Among the MOFs, Zeolitic imidazolate framework (ZIF) based membranes have shown an excellent performance, with high values for flux and separation factors. Various studies have been conducted, employing ZIF-PDMS membranes for pervaporation separation of mixtures such as aqueous-alcoholic solutions. This paper presents an extensive review of the pervaporation performance of ZIF-based mixed matrix membranes (MMMs), novel synthesis methods, filler modifications, factors affecting membrane performance as well as studies based on polymers other than PDMS for the membrane matrix. Some suggestions for future studies have also been provided, such as the use of biopolymers and self-healing membranes. Full article
(This article belongs to the Special Issue Characterization of Ceramic Membranes)
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13 pages, 3876 KiB  
Article
High Performance Mixed-Matrix Electrospun Membranes for Ammonium Removal from Wastewaters
by Shu-Ting Chen, Sumith Ranil Wickramasinghe and Xianghong Qian
Membranes 2021, 11(6), 440; https://doi.org/10.3390/membranes11060440 - 11 Jun 2021
Cited by 4 | Viewed by 2457
Abstract
Mixed-matrix electrospun membranes were developed to investigate ammonium removal from low ammonium concentration wastewaters for the first time. Particles derived from the inexpensive zeolite 13X were successfully incorporated into polyethersulfone (PES) matrices. The fabricated mixed-matrix electrospun membranes demonstrate high ammonium removal capacity reaching [...] Read more.
Mixed-matrix electrospun membranes were developed to investigate ammonium removal from low ammonium concentration wastewaters for the first time. Particles derived from the inexpensive zeolite 13X were successfully incorporated into polyethersulfone (PES) matrices. The fabricated mixed-matrix electrospun membranes demonstrate high ammonium removal capacity reaching over 55 mg/gzeolite, more than 2.5 times higher than the previously fabricated mixed-matrix membranes via non-solvent induced phase inversion. Moreover, the membranes fabricated exhibit high permeability and ease of regeneration. Over 90% of total ammonium nitrogen (TAN) can be removed from low TAN wastewaters such as aquaculture wastewaters. In addition to zeolite 13X, other zeolite particles including zeolite Y, zeolite 3A and 4A were also incorporated into the membrane matrix. The inexpensive zeolite 13X show the highest ammonium exchange capacity. Particle type, loading and the level of its dispersion all affect TAN removal capacity. Full article
(This article belongs to the Special Issue Innovative and Functional Polymer Membranes: Development and Applications)
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15 pages, 2865 KiB  
Article
Separation of H2O/CO2 Mixtures by MFI Membranes: Experiment and Monte Carlo Study
by Alexander Wotzka, Majid Namayandeh Jorabchi and Sebastian Wohlrab
Membranes 2021, 11(6), 439; https://doi.org/10.3390/membranes11060439 - 10 Jun 2021
Cited by 14 | Viewed by 4206
Abstract
The separation of CO2 from gas streams is a central process to close the carbon cycle. Established amine scrubbing methods often require hot water vapour to desorb the previously stored CO2. In this work, the applicability of MFI membranes for [...] Read more.
The separation of CO2 from gas streams is a central process to close the carbon cycle. Established amine scrubbing methods often require hot water vapour to desorb the previously stored CO2. In this work, the applicability of MFI membranes for H2O/CO2 separation is principally demonstrated by means of realistic adsorption isotherms computed by configurational-biased Monte Carlo (CBMC) simulations, then parameters such as temperatures, pressures and compositions were identified at which inorganic membranes with high selectivity can separate hot water vapour and thus make it available for recycling. Capillary condensation/adsorption by water in the microporous membranes used drastically reduces the transport and thus the CO2 permeance. Thus, separation factors of αH2O/CO2 = 6970 could be achieved at 70 °C and 1.8 bar feed pressure. Furthermore, the membranes were tested for stability against typical amines used in gas scrubbing processes. The preferred MFI membrane showed particularly high stability under application conditions. Full article
(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)
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13 pages, 2507 KiB  
Article
PRF-Solution in Large Sinus Membrane Perforation with Simultaneous Implant Placement-Micro CT and Histological Analysis
by Horia Mihail Barbu, Stefania Andrada Iancu, Violeta Hancu, Daniel Referendaru, Joseph Nissan and Sarit Naishlos
Membranes 2021, 11(6), 438; https://doi.org/10.3390/membranes11060438 - 10 Jun 2021
Cited by 14 | Viewed by 3415
Abstract
Background: The purpose of the study was to analyze the efficacy of platelet-rich fibrin (PRF) as a single augmentation material for complicated cases of maxillary sinus floor elevation, resulting from membrane perforation or previous infections. Methods: Implant insertion in the posterior region of [...] Read more.
Background: The purpose of the study was to analyze the efficacy of platelet-rich fibrin (PRF) as a single augmentation material for complicated cases of maxillary sinus floor elevation, resulting from membrane perforation or previous infections. Methods: Implant insertion in the posterior region of the maxilla was simultaneously performed with maxillary sinus floor augmentation. Schneiderian membrane elevation can be accompanied by extremely serious sinus membrane perforation, due to accidental tearing or intended incision for mucocele removal. PRFs were placed in the sinus cavity both for membrane sealing and sinus floor grafting. Radiological, histological and micro-CT analyses were performed. Implant survival was assessed every 6 months for 1 to 4 years, with a mean follow up of 1.8 years, after prosthetic loading. Radiological examinations were performed on CBCT at 9 and 12 and 36 months postoperatively and revealed improved degrees of radiopacity. Results: 19 implants were simultaneously placed in the course of nine maxillary sinus floor augmentation surgeries, with successful outcomes in terms of bone grafting and implant integration. New bone formation was evidenced 12 months postoperatively on radiological examination, micro-CT analysis, and histological analysis of a harvested bone segment from the augmented maxillary sinus. The mean gain in bone height of the sinus floor augmentation was 6.43 mm, with a maximum of 9 mm. The mean amount of vital bone obtained from histologic assessment was 52.30%, while bone volume/tissue volume ratio in micro-CT 3D had a mean of 50.32%. Conclusions: PRF may be considered as an alternative treatment for a single surgery of sinus augmentation with simultaneous implant placement, even in complicated cases with significant sinus membrane tearing. Full article
(This article belongs to the Special Issue Membranes for Tissue Engineering)
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20 pages, 6098 KiB  
Article
Analysis of Polyvinylidene Fluoride Membranes Fabricated for Membrane Distillation
by Minchul Ahn, Hyeongrak Cho, Yongjun Choi, Seockheon Lee and Sangho Lee
Membranes 2021, 11(6), 437; https://doi.org/10.3390/membranes11060437 - 10 Jun 2021
Cited by 1 | Viewed by 2995
Abstract
The optimization of the properties for MD membranes is challenging due to the trade-off between water productivity and wetting tendency. Herein, this study presents a novel methodology to examine the properties of MD membranes. Seven polyvinylidene fluoride (PVDF) membranes were synthesized under different [...] Read more.
The optimization of the properties for MD membranes is challenging due to the trade-off between water productivity and wetting tendency. Herein, this study presents a novel methodology to examine the properties of MD membranes. Seven polyvinylidene fluoride (PVDF) membranes were synthesized under different conditions by the phase inversion method and characterized to measure flux, rejection, contact angle (CA), liquid entry pressure (LEP), and pore sizes. Then, water vapor permeability (Bw), salt leakage ratio (Lw), and fiber radius (Rf) were calculated for the in-depth analysis. Results showed that the water vapor permeability and salt leakage ratio of the prepared membranes ranged from 7.76 × 10−8 s/m to 20.19 × 10−8 s/m and from 0.0020 to 0.0151, respectively. The Rf calculated using the Purcell model was in the range from 0.598 μm to 1.690 μm. Since the Rf was relatively small, the prepared membranes can have high LEP (more than 1.13 bar) even at low CA (less than 90.8°). The trade-off relations between the water vapor permeability and the other properties could be confirmed from the results of the prepared membranes. Based on these results, the properties of an efficient MD membrane were suggested as a guideline for the membrane development. Full article
(This article belongs to the Collection Polymeric Membranes: Science, Materials and Applications)
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17 pages, 3590 KiB  
Article
Composite Anion-Exchange Membrane Fabricated by UV Cross-Linking Vinyl Imidazolium Poly(Phenylene Oxide) with Polyacrylamides and Their Testing for Use in Redox Flow Batteries
by Martyna Charyton, Cristina Iojoiu, Peter Fischer, Gerard Henrion, Mathieu Etienne and Mateusz L. Donten
Membranes 2021, 11(6), 436; https://doi.org/10.3390/membranes11060436 - 10 Jun 2021
Cited by 9 | Viewed by 4472
Abstract
Composite anion-exchange membranes (AEMs) consisting of a porous substrate and a vinyl imidazolium poly(phenylene oxide) (VIMPPO)/acrylamide copolymer layer were fabricated in a straightforward process, for use in redox flow batteries. The porous substrate was coated with a mixture of VIMPPO and acrylamide monomers, [...] Read more.
Composite anion-exchange membranes (AEMs) consisting of a porous substrate and a vinyl imidazolium poly(phenylene oxide) (VIMPPO)/acrylamide copolymer layer were fabricated in a straightforward process, for use in redox flow batteries. The porous substrate was coated with a mixture of VIMPPO and acrylamide monomers, then subsequently exposed to UV irradiation, in order to obtain a radically cured ion-exchange coating. Combining VIMPPO with low-value reagents allowed to significantly reduce the amount of synthesized ionomer used to fabricate the mem- brane down to 15%. Varying the VIMPPO content also allowed tuning the ionic transport properties of the resulting AEM. A series of membranes with different VIMPPO/acrylamides ratios were prepared to assess the optimal composition by studying the changes of membranes properties—water uptake, area resistivity, permeability, and chemical stability. Characterization of the membranes was followed by cycling experiments in a vanadium RFB (VRFB) cell. Among three composite membranes, the one with VIMPPO 15% w/w—reached the highest energy efficiency (75.1%) matching the performance of commercial ion-exchange membranes (IEMs) used in VRFBs (Nafion® N 115: 75.0% and Fumasep® FAP 450: 73.0%). These results showed that the proposed composite AEM, fabricated in an industrially oriented process, could be considered to be a lower-cost alternative to the benchmarked IEMs. Full article
(This article belongs to the Section Membrane Chemistry)
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11 pages, 3075 KiB  
Article
Alginate Hydrogel Assisted Controllable Interfacial Polymerization for High-Performance Nanofiltration Membranes
by Zhao-Yu Ma, Yu-Ren Xue and Zhi-Kang Xu
Membranes 2021, 11(6), 435; https://doi.org/10.3390/membranes11060435 - 10 Jun 2021
Cited by 17 | Viewed by 3993
Abstract
The deepening crisis of freshwater resources has been driving the further development of new types of membrane-based desalination technologies represented by nanofiltration membranes. Solving the existing trade-off limitation on enhancing the water permeance and the rejection of salts is currently one of the [...] Read more.
The deepening crisis of freshwater resources has been driving the further development of new types of membrane-based desalination technologies represented by nanofiltration membranes. Solving the existing trade-off limitation on enhancing the water permeance and the rejection of salts is currently one of the most concerned research interests. Here, a facile and scalable approach is proposed to tune the interfacial polymerization by constructing a calcium alginate hydrogel layer on the porous substrates. The evenly coated thin hydrogel layer can not only store amine monomers like the aqueous phase but also suppress the diffusion of amine monomers inside, as well as provide a flat and stable interface to implement the interfacial polymerization. The resultant polyamide nanofilms have a relatively smooth morphology, negatively charged surface, and reduced thickness which facilitate a fast water permeation while maintaining rejection efficiency. As a result, the as-prepared composite membranes show improved water permeance (~30 Lm−2h−1bar−1) and comparable rejection of Na2SO4 (>97%) in practical applications. It is proved to be a feasible approach to manufacturing high-performance nanofiltration membranes with the assist of alginate hydrogel regulating interfacial polymerization. Full article
(This article belongs to the Special Issue Novel Materials for the Preparation and Application of Desalination Membranes)
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13 pages, 1257 KiB  
Article
Transition from Simple V-V to V-A and Hybrid ECMO Configurations in COVID-19 ARDS
by Piotr Suwalski, Jakub Staromłyński, Jakub Brączkowski, Maciej Bartczak, Silvia Mariani, Dominik Drobiński, Konstanty Szułdrzyński, Radosław Smoczyński, Marzena Franczyk, Wojciech Sarnowski, Agnieszka Gajewska, Anna Witkowska, Waldemar Wierzba, Artur Zaczyński, Zbigniew Król, Ewa Olek, Michał Pasierski, Justine Mafalda Ravaux, Maria Elena de Piero, Roberto Lorusso and Mariusz Kowalewskiadd Show full author list remove Hide full author list
Membranes 2021, 11(6), 434; https://doi.org/10.3390/membranes11060434 - 9 Jun 2021
Cited by 17 | Viewed by 6538
Abstract
In SARS-CoV-2 patients with severe acute respiratory distress syndrome (ARDS), Veno-Venous Extracorporeal Membrane Oxygenation (V-V ECMO) was shown to provide valuable treatment with reasonable survival in large multi-centre investigations. However, in some patients, conversion to modified ECMO support forms may be needed. In [...] Read more.
In SARS-CoV-2 patients with severe acute respiratory distress syndrome (ARDS), Veno-Venous Extracorporeal Membrane Oxygenation (V-V ECMO) was shown to provide valuable treatment with reasonable survival in large multi-centre investigations. However, in some patients, conversion to modified ECMO support forms may be needed. In this single-centre retrospective registry, all consecutive patients receiving V-V ECMO between 1 March 2020 to 1 May 2021 were included and analysed. The patient cohort was divided into two groups: those who remained on V-V ECMO and those who required conversion to other modalities. Seventy-eight patients were included, with fourteen cases (18%) requiring conversions to veno-arterial (V-A) or hybrid ECMO. The reasons for the ECMO mode configuration change were inadequate drainage (35.7%), inadequate perfusion (14.3%), myocardial infarction (7.1%), hypovolemic shock (14.3%), cardiogenic shock (14.3%) and septic shock (7.1%). In multivariable analysis, the use of dobutamine (p = 0.007) and a shorter ICU duration (p = 0.047) predicted the conversion. The 30-day mortality was higher in converted patients (log-rank p = 0.029). Overall, only 19 patients (24.4%) survived to discharge or lung transplantation. Adverse events were more common after conversion and included renal, cardiovascular and ECMO-circuit complications. Conversion itself was not associated with mortality in the multivariable analysis. In conclusion, as many as 18% of patients undergoing V-V ECMO for COVID-19 ARDS may require conversion to advanced ECMO support. Full article
(This article belongs to the Special Issue Challenges in the Extracorporeal Membrane Oxygenation Era)
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17 pages, 4825 KiB  
Article
TiO2 Nanoparticle Filler-Based Mixed-Matrix PES/CA Nanofiltration Membranes for Enhanced Desalination
by Mehwish Batool, Amir Shafeeq, Bilal Haider and Nasir M. Ahmad
Membranes 2021, 11(6), 433; https://doi.org/10.3390/membranes11060433 - 9 Jun 2021
Cited by 28 | Viewed by 4830
Abstract
Mixed-matrix nanocomposite (PES/CA/PVP) membranes were fabricated for water desalination by incorporating varying amount of titanium dioxide nanoparticles (TiO2 NPs) ranging from 0 and 2 wt. %. Efficient dispersion of nanoparticles within polymeric membranes was achieved using the chemical precipitation method for uniform [...] Read more.
Mixed-matrix nanocomposite (PES/CA/PVP) membranes were fabricated for water desalination by incorporating varying amount of titanium dioxide nanoparticles (TiO2 NPs) ranging from 0 and 2 wt. %. Efficient dispersion of nanoparticles within polymeric membranes was achieved using the chemical precipitation method for uniform surface generation, and an asymmetric morphology was achieved via phase inversion method. Finally, membranes were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Thermo Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), porosity and contact angle analysis. FTIR confirmed chemical composition of membranes in terms of polymers (PES/CA/PVP) and TiO2. TGA analysis confirmed an increase in thermal stability of membranes with the increase of TiO2 nanoparticles loading. The addition of TiO2 nanoparticles also resulted in an increase in porous structures due to an increase in mean pore size, as shown by SEM results. An increase in the hydrophilicity of the membranes was observed by increasing the concentration of TiO2 nanoparticles. The present study investigated pristine and mixed-matrix nanocomposite NF membrane performance while filtering a NaCl salt solution at varying concentration range (from 1 to 4 g/Lit 6 bar). The prepared membranes demonstrated significant improvement in water permeability and hydrophilicity. Further, to optimize the water flux and salt rejection, the concentration of Polyvinylpyrrolidone (PVP) was optimized along with TiO2 nanoparticles. Both the water flux and salt rejection of the fabricated membranes were observed to increase with an increase inTiO2 nanoparticles to 2 wt. % loading with optimized PVP concentration, which demonstrated the improved desalination performance of resultant membranes. Full article
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13 pages, 1582 KiB  
Article
Multidrug Resistance Like Protein 1 Activity in Malpighian Tubules Regulates Lipid Homeostasis in Drosophila
by Wen Liu, Hao Cao, Moses Kimari, Georgios Maronitis, Michael J. Williams and Helgi B Schiöth
Membranes 2021, 11(6), 432; https://doi.org/10.3390/membranes11060432 - 8 Jun 2021
Cited by 3 | Viewed by 3045
Abstract
Multidrug resistance proteins (MRPs), members of the ATP-binding cassette transporter (ABC transporter) family, are pivotal for transporting endo- and xenobiotics, which confer resistance to anticancer agents and contribute to the clearance of oxidative products. However, their function in many biological processes is still [...] Read more.
Multidrug resistance proteins (MRPs), members of the ATP-binding cassette transporter (ABC transporter) family, are pivotal for transporting endo- and xenobiotics, which confer resistance to anticancer agents and contribute to the clearance of oxidative products. However, their function in many biological processes is still unclear. We investigated the role of an evolutionarily conserved MRP in metabolic homeostasis by knocking down the expression of Drosophila multidrug-resistance like protein 1 (MRP) in several tissues involved in regulating metabolism, including the gut, fat body, and Malpighian tubules. Interestingly, only suppression of MRP in the Malpighian tubules, the functional equivalent to the human kidney, was sufficient to cause abnormal lipid accumulation and disrupt feeding behavior. Furthermore, reduced Malpighian tubule MRP expression resulted in increased Hr96 (homolog of human pregnane X receptor) expression. Hr96 is known to play a role in detoxification and lipid metabolism processes. Reduced expression of MRP in the Malpighian tubules also conveyed resistance to oxidative stress, as well as reduced normal levels of reactive oxygen species in adult flies. This study reveals that an evolutionarily conserved MRP is required in Drosophila Malpighian tubules for proper metabolic homeostasis. Full article
(This article belongs to the Special Issue Biological Membranes as Targets for Natural and Synthetic Compounds)
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14 pages, 3992 KiB  
Article
A Simple 1D Convection-Diffusion Model of Oxalic Acid Oxidation Using Reactive Electrochemical Membrane
by Ekaterina Skolotneva, Marc Cretin and Semyon Mareev
Membranes 2021, 11(6), 431; https://doi.org/10.3390/membranes11060431 - 7 Jun 2021
Cited by 4 | Viewed by 2693
Abstract
In recent years, electrochemical methods utilizing reactive electrochemical membranes (REM) have been recognized as the most promising technologies for the removal of organic pollutants from water. In this paper, we propose a 1D convection-diffusion-reaction model concerning the transport and oxidation of oxalic acid [...] Read more.
In recent years, electrochemical methods utilizing reactive electrochemical membranes (REM) have been recognized as the most promising technologies for the removal of organic pollutants from water. In this paper, we propose a 1D convection-diffusion-reaction model concerning the transport and oxidation of oxalic acid (OA) and oxygen evolution in the flow-through electrochemical oxidation system with REM. It allows the determination of unknown parameters of the system by treatment of experimental data and predicts the behavior of the electrolysis setup. There is a good agreement in calculated and experimental data at different transmembrane pressures and initial concentrations of OA. The model provides an understanding of the processes occurring in the system and gives the concentration, current density, potential, and overpotential distributions in REM. The dispersion coefficient was determined as a fitting parameter and it is in good agreement with literary data for similar REMs. It is shown that the oxygen evolution reaction plays an important role in the process even under the kinetic limit, and its contribution decreases with increasing total organic carbon flux through the REM. Full article
(This article belongs to the Special Issue Numerical Modelling in Membrane Processes)
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13 pages, 3585 KiB  
Article
Flue Gas Desulfurization (FGD) Wastewater Treatment Using Polybenzimidazole (PBI) Hollow Fiber (HF) Membranes
by Michael Dean Wales, Eminet Gebremichael, Xiao Wang, Elisabeth Perea, Palitha Jayaweera and Indira Jayaweera
Membranes 2021, 11(6), 430; https://doi.org/10.3390/membranes11060430 - 5 Jun 2021
Cited by 8 | Viewed by 5065
Abstract
Polybenzimidazole (PBI) hollow fiber membranes were used to treat flue gas desulfurization (FGD) wastewater (WW) from a coal fired power plant. Membranes were tested using both single salt solutions and real FGD WW. The PBI membranes showed >99% rejection for single salt solutions [...] Read more.
Polybenzimidazole (PBI) hollow fiber membranes were used to treat flue gas desulfurization (FGD) wastewater (WW) from a coal fired power plant. Membranes were tested using both single salt solutions and real FGD WW. The PBI membranes showed >99% rejection for single salt solutions of NaCl, MgCl2, CaSO4, and CaCl2 at approximately 2000 PPM (parts per million). The membranes also showed >97% rejection for FGD WW concentrations ranging from 6900 to 14,400 PPM total dissolved solids (TDS). The pH of the FGD WW was adjusted between 3.97–8.20, and there was an optimal pH between 5.31 and 7.80 where %rejection reached a maximum of >99%. The membranes were able to operate stably up to 50 °C, nearly doubling the water flux as compared to room temperature, and while maintaining >98% salt rejection. Full article
(This article belongs to the Section Membrane Applications)
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24 pages, 12151 KiB  
Article
Recuperative Amino Acids Separation through Cellulose Derivative Membranes with Microporous Polypropylene Fiber Matrix
by Aurelia Cristina Nechifor, Andreia Pîrțac, Paul Constantin Albu, Alexandra Raluca Grosu, Florina Dumitru, Ioana Alina Dimulescu (Nica), Ovidiu Oprea, Dumitru Pașcu, Gheorghe Nechifor and Simona Gabriela Bungău
Membranes 2021, 11(6), 429; https://doi.org/10.3390/membranes11060429 - 5 Jun 2021
Cited by 20 | Viewed by 4460
Abstract
The separation, concentration and transport of the amino acids through membranes have been continuously developed due to the multitude of interest amino acids of interest and the sources from which they must be recovered. At the same time, the types of membranes used [...] Read more.
The separation, concentration and transport of the amino acids through membranes have been continuously developed due to the multitude of interest amino acids of interest and the sources from which they must be recovered. At the same time, the types of membranes used in the sepa-ration of the amino acids are the most diverse: liquids, ion exchangers, inorganic, polymeric or composites. This paper addresses the recuperative separation of three amino acids (alanine, phe-nylalanine, and methionine) using membranes from cellulosic derivatives in polypropylene ma-trix. The microfiltration membranes (polypropylene hollow fibers) were impregnated with solu-tions of some cellulosic derivatives: cellulose acetate, 2-hydroxyethyl-cellulose, methyl 2-hydroxyethyl-celluloseand sodium carboxymethyl-cellulose. The obtained membranes were characterized in terms of the separation performance of the amino acids considered (retention, flux, and selectivity) and from a morphological and structural point of view: scanning electron microscopy (SEM), high resolution SEM (HR-SEM), Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and thermal gravimetric analyzer (TGA). The re-sults obtained show that phenylalanine has the highest fluxes through all four types of mem-branes, followed by methionine and alanine. Of the four kinds of membrane, the most suitable for recuperative separation of the considered amino acids are those based on cellulose acetate and methyl 2-hydroxyethyl-cellulose. Full article
(This article belongs to the Collection Polymeric Membranes: Science, Materials and Applications)
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16 pages, 2794 KiB  
Article
Surface Modification of E. coli Outer Membrane Vesicles with Glycosylphosphatidylinositol-Anchored Proteins: Generating Pro/Eukaryote Chimera Constructs
by Marianne Zaruba, Lena Roschitz, Haider Sami, Manfred Ogris, Wilhelm Gerner and Christoph Metzner
Membranes 2021, 11(6), 428; https://doi.org/10.3390/membranes11060428 - 4 Jun 2021
Cited by 6 | Viewed by 5193
Abstract
Extracellular vesicles produced by different types of cells have recently attracted great attention, not only for their role in physiology and pathology, but also because of the emerging applications in gene therapy, vaccine production and diagnostics. Less well known than their eukaryotic counterpart, [...] Read more.
Extracellular vesicles produced by different types of cells have recently attracted great attention, not only for their role in physiology and pathology, but also because of the emerging applications in gene therapy, vaccine production and diagnostics. Less well known than their eukaryotic counterpart, also bacteria produce extracellular vesicles, in the case of the Gram-negative E. coli the main species is termed outer membrane vesicles (OMVs). In this study, we show for the first time the functional surface modification of E. coli OMVs with glycosylphosphatidylinositol (GPI)-anchored protein, exploiting a process variably described as molecular painting or protein engineering in eukaryotic membranes, whereby the lipid part of the GPI anchor inserts in cell membranes. By transferring the process to bacterial vesicles, we can generate a hybrid of perfectly eukaryotic proteins (in terms of folding and post-translational modifications) on a prokaryotic platform. We could demonstrate that two different GPI proteins can be displayed on the same OMV. In addition to fluorescent marker proteins, cytokines, growth factors and antigens canb be potentially transferred, generating a versatile modular platform for a novel vaccine strategy. Full article
(This article belongs to the Special Issue Protein-Lipid Interactions as Key Regulators of Cell Function)
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