Membranes

16 pages, 7888 KiB

Open AccessArticle

Stability of Non-Concentric, Multilayer, and Fully Aligned Porous MoS₂ Nanotubes

by Pablo Jahir Peña-Obeso, Rafael Huirache-Acuña, Fernando Iguazú Ramirez-Zavaleta and José Luis Rivera

Membranes 2022, 12(8), 818; https://doi.org/10.3390/membranes12080818 - 22 Aug 2022

Cited by 2 | Viewed by 1317

Nanotubes made of non-concentric and multiple small layers of porous MoS₂ contain inner pores suitable for membrane applications. In this study, molecular dynamics simulations using reactive potentials were employed to estimate the stability of the nanotubes and how their stability compares to [...] Read more.

Nanotubes made of non-concentric and multiple small layers of porous MoS₂ contain inner pores suitable for membrane applications. In this study, molecular dynamics simulations using reactive potentials were employed to estimate the stability of the nanotubes and how their stability compares to macroscopic single- (1L) and double-layer MoS₂ flakes. The observed stability was explained in terms of several analyses that focused on the size of the area of full-covered layers, number of layers, polytype, and size of the holes in the 1L flakes. The reactive potential used in this work reproduced experimental results that have been previously reported, including the small dependency of the stability on the polytype, the formation of S–S bonds between inter- and intra-planes, and the limit of stability for two concentric rings forming a single ring-like flake. Full article

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

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12 pages, 3735 KiB

Open AccessArticle

Thin-Film Composite Membranes with a Carbon Nanotube Interlayer for Organic Solvent Nanofiltration

by Mingjia Liao, Yun Zhu, Genghao Gong and Lei Qiao

Membranes 2022, 12(8), 817; https://doi.org/10.3390/membranes12080817 - 22 Aug 2022

Cited by 9 | Viewed by 1650

Abstract

Compared to the traditional chemical-crosslinking-based polymer, the porous polytetrafluoroethylene (PTFE) substrate is considered to be an excellent support for the fabrication of thin-film composite (TFC) organic solvent nanofiltration (OSN) membranes. However, the low surface energy and chemical inertness of PTFE membranes presented major [...] Read more.

Compared to the traditional chemical-crosslinking-based polymer, the porous polytetrafluoroethylene (PTFE) substrate is considered to be an excellent support for the fabrication of thin-film composite (TFC) organic solvent nanofiltration (OSN) membranes. However, the low surface energy and chemical inertness of PTFE membranes presented major challenges for fabricating a polyamide active layer on its surface via interfacial polymerization (IP). In this study, a triple-layered TFC OSN membrane was fabricated via IP, which consisted of a PA top layer on a carbon nanotube (CNT) interlayer covering the macroporous PTFE substrate. The defect-free formation and cross-linking degree of the PA layer can be improved by controlling the CNT deposition amount to achieve a good OSN performance. This new TFC OSN membrane exhibited a high dye rejection (the rejection of Bright blue B > 97%) and a moderate and stable methanol permeated flux of approximately 8.0 L m⁻² h⁻¹ bar⁻¹. Moreover, this TFC OSN membrane also exhibited an excellent solvent resistance to various organic solvents and long-term stability during a continuous OSN process. Full article

(This article belongs to the Special Issue Preparation of Organic-Inorganic Hybrid Membranes and Their Membrane Performance)

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15 pages, 7165 KiB

Open AccessArticle

Research on Measuring Pure Membrane Electrical Resistance under the Effects of Salinity Gradients and Diffusion Boundary Layer and Double Layer Resistances

by Yang Zhao and Liang Duan

Membranes 2022, 12(8), 816; https://doi.org/10.3390/membranes12080816 - 22 Aug 2022

Cited by 5 | Viewed by 1472

Abstract

Forward osmosis membranes are an emerging technology with great potential applicability in energy-efficient wastewater treatments and the differentiation between two solutions. Such solutions often differ in their concentrations or compositions. In this study, the membrane electrical resistances of three different membranes, including cation [...] Read more.

Forward osmosis membranes are an emerging technology with great potential applicability in energy-efficient wastewater treatments and the differentiation between two solutions. Such solutions often differ in their concentrations or compositions. In this study, the membrane electrical resistances of three different membranes, including cation or anion-exchange membranes and forward osmosis membranes, were analyzed by Luggin capillary coupled with AC impedance spectroscopy (EIS) so as to obtain the real membrane and ion transfer impedance values near the membrane interface. The results reveal that the membrane impedance obtained by both the DC and AC approaches decreased as the lowest external solution concentration increased. Furthermore, the relationship between the membrane conductivity and the internal salt solution concentration was also investigated. It can be seen that the external ion concentration is directly proportional to the free ion concentration in the membrane, and the free ion concentration in the membrane is closely related to the membrane electrical resistance. Full article

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15 pages, 3861 KiB

Open AccessArticle

Bromine Crossover in Operando Analysis of Proton Exchange Membranes in Hydrogen−Bromate Flow Batteries

by Alexander Modestov, Natalia Kartashova, Roman Pichugov, Mikhail Petrov, Anatoly Antipov and Lilia Abunaeva

Membranes 2022, 12(8), 815; https://doi.org/10.3390/membranes12080815 - 22 Aug 2022

Cited by 6 | Viewed by 1654

Abstract

The manuscript deals with the fundamental problem of platinum hydrogen oxidation catalyst poisoning of the hybrid chemical power source based on bromate electroreduction and hydrogen electro-oxidation reactions. The poisoning is caused by the crossover of bromine-containing species through the proton exchange membrane separating [...] Read more.

The manuscript deals with the fundamental problem of platinum hydrogen oxidation catalyst poisoning of the hybrid chemical power source based on bromate electroreduction and hydrogen electro-oxidation reactions. The poisoning is caused by the crossover of bromine-containing species through the proton exchange membrane separating compartments of the flow cell. Poisoning results in a drastic decrease in the flow cell performance. This paper describes the results of the direct measurement of bromine-containing species’ crossover through perfluorosulfonic acid membranes of popular vendors in a hydrogen−bromate flow cell and proposes corresponding scenarios for the flow battery charge−discharge operation based on the electrolyte’s control of the pH value. The rate of the crossover of the bromine-containing species through the membrane is found to be inversely proportional to the membrane thickness. Full article

(This article belongs to the Section Membrane Applications)

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12 pages, 4250 KiB

Open AccessArticle

Membrane Fouling and Electrochemical Regeneration at a PbO₂-Reactive Electrochemical Membrane: Study on Experiment and Mechanism

by Liankai Gu, Yonghao Zhang, Weiqing Han and Kajia Wei

Membranes 2022, 12(8), 814; https://doi.org/10.3390/membranes12080814 - 22 Aug 2022

Cited by 1 | Viewed by 1466

Abstract

Membrane fouling and regeneration are the key issues for the application of membrane separation (MS) technology. Reactive electrochemical membranes (REMs) exhibited high, stable permeate flux and the function of chemical-free electrochemical regeneration. This study fabricated a micro-filtration REM characterized by a PbO₂ [...] Read more.

Membrane fouling and regeneration are the key issues for the application of membrane separation (MS) technology. Reactive electrochemical membranes (REMs) exhibited high, stable permeate flux and the function of chemical-free electrochemical regeneration. This study fabricated a micro-filtration REM characterized by a PbO₂ layer (PbO₂-REM) to investigate the electro-triggered anti-fouling and regeneration progress within REMs. The PbO₂-REM exhibited a three-dimensional porous structure with a few branch-like micro-pores. The PbO₂-REM could alleviate Humic acid (HA) and Bisphenol A (BPA) fouling through electrochemical degradation combined with bubble migration, which achieved the best anti-fouling performance at current density of 4 mA cm⁻² with 99.2% BPA removal. Regeneration in the electro-backwash (e-BW) mode was found as eight times that in the forward wash and full flux recovery was achieved at a current density of 3 mA cm⁻². EIS and simulation study also confirmed complete regeneration by e-BW, which was ascribed to the air–water wash formed by bubble migration and flow. Repeated regeneration tests showed that PbO₂-REM was stable for more than five cycles, indicating its high durability for practical uses. Mechanism analysis assisted by finite element simulation illustrated that the high catalytic PbO₂ layer plays an important role in antifouling and regeneration. Full article

(This article belongs to the Special Issue Advance in Electromembrane Technology)

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16 pages, 3111 KiB

Open AccessArticle

Treatment of Tuna Cooking Juice via Ceramic Ultrafiltration Membrane: Optimization Using Response Surface Methodology

by Wala Aloulou, Hajer Aloulou, Afef Attia, Sudip Chakraborty and Raja Ben Amar

Membranes 2022, 12(8), 813; https://doi.org/10.3390/membranes12080813 - 22 Aug 2022

Cited by 4 | Viewed by 1629

Abstract

In the present work, optimized ultrafiltration conditions, using a ceramic multi tubular titania membrane (150 KDa), were investigated for the treatment of tuna cooking juice, for water reuse in the industrial process. The interactive effects of the volume concentrating factor (VCF) (1.03–4.25), feed [...] Read more.

In the present work, optimized ultrafiltration conditions, using a ceramic multi tubular titania membrane (150 KDa), were investigated for the treatment of tuna cooking juice, for water reuse in the industrial process. The interactive effects of the volume concentrating factor (VCF) (1.03–4.25), feed temperature (T) (20–60 °C), and applied transmembrane pressure (ΔP) (2–5 bar) on protein removal (R protein) and permeate flux (J) were determined. A Box–Behnken experimental design (BBD) with the response surface methodology (RSM) was used for statistical analysis, modeling, and optimization of the operating conditions. The analysis of variance (ANOVA) results proved that the protein removal and permeate flux were significant and represented good correlation coefficients of 0.9859 and 0.9294, respectively. Mathematical modeling showed that the best conditions were VCF = 1.5 and a feed temperature of 60 °C, under a transmembrane pressure of 5 bar. The fouling mechanism was checked by applying a polarization concentration model. Determination of the gel concentration confirmed the results found in the mass balance calculation and proved that the VCF must not exceed 1.5. The membrane regeneration efficiency was proven by determining the water permeability after the chemical cleaning process. Full article

(This article belongs to the Special Issue Membrane Process Systems and Techniques)

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19 pages, 1196 KiB

Open AccessReview

Interactions between the Nicotinic and Endocannabinoid Receptors at the Plasma Membrane

by Ana Sofía Vallés and Francisco J. Barrantes

Membranes 2022, 12(8), 812; https://doi.org/10.3390/membranes12080812 - 22 Aug 2022

Cited by 4 | Viewed by 2198

Abstract

Compartmentalization, together with transbilayer and lateral asymmetries, provide the structural foundation for functional specializations at the cell surface, including the active role of the lipid microenvironment in the modulation of membrane-bound proteins. The chemical synapse, the site where neurotransmitter-coded signals are decoded by [...] Read more.

Compartmentalization, together with transbilayer and lateral asymmetries, provide the structural foundation for functional specializations at the cell surface, including the active role of the lipid microenvironment in the modulation of membrane-bound proteins. The chemical synapse, the site where neurotransmitter-coded signals are decoded by neurotransmitter receptors, adds another layer of complexity to the plasma membrane architectural intricacy, mainly due to the need to accommodate a sizeable number of molecules in a minute subcellular compartment with dimensions barely reaching the micrometer. In this review, we discuss how nature has developed suitable adjustments to accommodate different types of membrane-bound receptors and scaffolding proteins via membrane microdomains, and how this “effort-sharing” mechanism has evolved to optimize crosstalk, separation, or coupling, where/when appropriate. We focus on a fast ligand-gated neurotransmitter receptor, the nicotinic acetylcholine receptor, and a second-messenger G-protein coupled receptor, the cannabinoid receptor, as a paradigmatic example. Full article

(This article belongs to the Special Issue Membrane Channel of Cells)

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13 pages, 2683 KiB

Open AccessArticle

A Larger Membrane Area Increases Cytokine Removal in Polymethyl Methacrylate Hemofilters

by Tomoyuki Nakamura, Kazuhiro Moriyama, Naohide Kuriyama, Yoshitaka Hara, Satoshi Komatsu, Takahiro Kawaji, Yu Kato, Takuma Ishihara, Ayumi Shintani and Osamu Nishida

Membranes 2022, 12(8), 811; https://doi.org/10.3390/membranes12080811 - 22 Aug 2022

Cited by 1 | Viewed by 1491

Abstract

Blood purification is performed to control cytokines in critically ill patients. The relationship between the clearance (CL) and the membrane area during adsorption is not clear. We hypothesized that the CL increases with the hydrophobic area when hydrophobic binding contributes to cytokine adsorption. [...] Read more.

Blood purification is performed to control cytokines in critically ill patients. The relationship between the clearance (CL) and the membrane area during adsorption is not clear. We hypothesized that the CL increases with the hydrophobic area when hydrophobic binding contributes to cytokine adsorption. We investigated the relationship between the hemofilter membrane area and the CL of the high mobility group box 1 protein (HMGB-1) and interleukin-6 (IL-6). We performed experimental hemofiltration in vitro using polymethyl methacrylate membranes CH-1.8W (1.8 m²) and CH-1.0N (1.0 m²), as well as polysulfone membrane NV-18X (1.8 m²). After adding 100 mg of HMGB1 or 10 μg of IL-6 into the test solution, experimental hemofiltration was conducted for 360 min in a closed-loop circulation system, and the same amount of HMGB1 and IL-6 was added after 180 min. With CH-1.8W and CH-1.0N, both HMGB-1 and IL-6 showed a rapid concentration decrease of more than 70% at 180 min and 360 min after the re-addition. At 15 min, the CL of HMGB-1 was CH-1.8W: 28.4 and CH-1.0N: 19.8, and that of IL-6 was CH-1.8W: 41.1 and CH-1.0N: 25.4. CH-1.8W and CH-1.0N removed HMGB1 and IL-6 by adsorption and CH-1.8W was superior in CL, which increased with a greater membrane area. Full article

(This article belongs to the Special Issue Surface and Interface Engineering of Polymeric Membrane)

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17 pages, 5131 KiB

Open AccessArticle

Cake Layer Fouling Potential Characterization for Wastewater Reverse Osmosis via Gradient Filtration

by Rulu Ouyang, Bin Huang, Chun-Hai Wei, Hongwei Rong, Huarong Yu, Fangshu Qu, Kang Xiao and Xia Huang

Membranes 2022, 12(8), 810; https://doi.org/10.3390/membranes12080810 - 21 Aug 2022

Cited by 2 | Viewed by 1376

Abstract

It is of great importance to quantitatively characterize feed fouling potential for the effective and efficient prevention and control of reverse osmosis membrane fouling. A gradient filtration method with microfiltration (MF 0.45 μm) → ultrafiltration (UF 100 kDa) → nanofiltration (NF 300 Da) [...] Read more.

It is of great importance to quantitatively characterize feed fouling potential for the effective and efficient prevention and control of reverse osmosis membrane fouling. A gradient filtration method with microfiltration (MF 0.45 μm) → ultrafiltration (UF 100 kDa) → nanofiltration (NF 300 Da) was proposed to extract the cake layer fouling index, I, of different feed foulants in this study. MF, UF, and NF showed high rejection of model suspended solids (kaolin), colloids (sodium alginate and bovine serum albumin), and dissolved organic matters (humic acid) during constant-pressure individual filtration tests, where the cake layer was the dominant fouling mechanism, with I showing a good linear positive correlation with the foulant concentration. MF → UF → NF gradient filtration tests of synthetic wastewater (i.e., model mixture) showed that combined models were more effective than single models to analyze membrane fouling mechanisms. For each membrane of gradient filtration, I showed a positive correlation with the targeted foulant concentration. Therefore, a quantitative assessment method based on MF → UF → NF gradient filtration, the correlation of combined fouling models, and the calculation of I would be useful for characterizing the fouling potentials of different foulants. This method was further successfully applied for characterizing the fouling potential of real wastewater (i.e., sludge supernatant from a membrane bioreactor treating dyeing and finishing wastewater). Full article

(This article belongs to the Special Issue Membrane Fouling in Water/Wastewater Treatment: Characterization, Modeling and Control)

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15 pages, 4011 KiB

Open AccessArticle

Micromechanism Study of Molecular Compatibility of PVDF/PEI Blend Membrane

by Ming Gao, Yuanlu Zhu, Jiangyi Yan, Weixing Wu and Beifu Wang

Membranes 2022, 12(8), 809; https://doi.org/10.3390/membranes12080809 - 21 Aug 2022

Cited by 7 | Viewed by 1936

Abstract

In this paper, the compatibility of polyetherimide (PEI) with different contents as a high-performance copolymer and polyvinylidene fluoride (PVDF) was studied, and 5%–20% PEI was prepared by the non-solvent-induced phase inversion method. The compatibility of PVDF and PEI was evaluated by analyzing the [...] Read more.

In this paper, the compatibility of polyetherimide (PEI) with different contents as a high-performance copolymer and polyvinylidene fluoride (PVDF) was studied, and 5%–20% PEI was prepared by the non-solvent-induced phase inversion method. The compatibility of PVDF and PEI was evaluated by analyzing the physical structure and properties of the blend membrane, the microstructure, the glass transition temperature Tg, the enthalpy, and the mechanism of the polymer blend enthalpy change. The results show that the blend membranes have -NH and C=O-N binding energies at X-ray photoelectron spectroscopy (XPS), which preliminarily proves that fluorine–amine bonds are formed between the polymers, and new spectra appeared by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) peaks, which further proves that the two have the formation of fluorine–amine bonds, the Tg and enthalpy of the mixed membrane was increased, and a scanning electron microscope (SEM) observed that the membrane pores changed from finger-like pores to sponge-like macropores. When the content of PEI is 15%, the performance of the blended membrane is the best, the water contact angle increases to 58.5°, the porosity increases to 17.33%, the maximum force increases to 8.04 N, and the elongation at break decreases to 24.26%, the pure water flux is 1870.292 L/m²·h, and the oil rejection is 87%. In addition, the enthalpy change of polymer blending further proves that PEI and PVDF are compatible systems and have a good performance improvement for PVDF. Full article

(This article belongs to the Section Polymeric Membranes)

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12 pages, 2272 KiB

Open AccessArticle

Athermal Concentration of Blueberry Juice by Forward Osmosis: Food Additives as Draw Solution

by Haoqi Chu, Zhihan Zhang, Huazhao Zhong, Kai Yang, Peilong Sun, Xiaojun Liao and Ming Cai

Membranes 2022, 12(8), 808; https://doi.org/10.3390/membranes12080808 - 21 Aug 2022

Cited by 4 | Viewed by 1652

Abstract

This study is to evaluate the athermal forward osmosis (FO) concentration process of blueberry juice using food additives as a draw solution (DS). The effects of food additives, including citric acid, sodium benzoate, and potassium sorbate, on the concentration processes are studied, and [...] Read more.

This study is to evaluate the athermal forward osmosis (FO) concentration process of blueberry juice using food additives as a draw solution (DS). The effects of food additives, including citric acid, sodium benzoate, and potassium sorbate, on the concentration processes are studied, and their effects on the products and membranes are compared. Results show that all these three food additives can be alternative DSs in concentration, among which citric acid shows the best performance. The total anthocyanin content (TAC) of blueberry juice concentrated by citric acid, sodium benzoate, and potassium sorbate were 752.56 ± 29.04, 716.10 ± 30.80, and 735.31 ± 24.92 mg·L⁻¹, respectively, increased by 25.5%, 17.8%, and 19.9%. Meanwhile, the total phenolic content (TPC) increased by 21.0%, 10.6%, and 16.6%, respectively. Citric acid, sodium benzoate, and potassium sorbate all might reverse into the concentrated juice in amounts of 3.083 ± 0.477, 1.497 ± 0.008, and 0.869 ± 0.003 g/kg, respectively. These reversed food additives can make the TPC and TAC in juice steadier during its concentration and storage. Accordingly, food additives can be an excellent choice for DSs in the FO concentration process of juices, not only improving the concentration efficiency but also increasing the stability of blueberry juice. Full article

(This article belongs to the Special Issue Application of Membrane Technology in Foods and Natural Products)

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25 pages, 4943 KiB

Open AccessArticle

Ethanol Separation from an Ethanol–Water Solution Using Vacuum Membrane Distillation

by Abeer G. Nassif, Salah S. Ibrahim, Hasan Sh. Majdi and Qusay F. Alsalhy

Membranes 2022, 12(8), 807; https://doi.org/10.3390/membranes12080807 - 20 Aug 2022

Cited by 4 | Viewed by 3336

Abstract

The vacuum membrane distillation (VMD) process was applied to separate ethanol from a simulated ethanol–water solution using a commercial polytetrafluoroethylene (PTFE) membrane. The presence of ethanol in the ethanol–water solution with a 2 wt.% ethanol concentration at a temperature above 40 °C during [...] Read more.

The vacuum membrane distillation (VMD) process was applied to separate ethanol from a simulated ethanol–water solution using a commercial polytetrafluoroethylene (PTFE) membrane. The presence of ethanol in the ethanol–water solution with a 2 wt.% ethanol concentration at a temperature above 40 °C during the MD process may result in membrane failure due to an increase in the chance of the PTFE membrane wetting at high temperatures. Therefore, the operating temperature in this study was not higher than 35 °C, with an initial ethanol concentration up to 10 wt.%. This work focuses on optimizing the VMD operating parameters using the Taguchi technique based on an analysis of variance (ANOVA). It was found that the feed temperature was the most-affected parameter, leading to a significant increase in the permeation flux of the PTFE membrane. Our results also showed that the permeate flux was reported at about 24.145 kg/m²·h, with a separation factor of 8.6 of the permeate under the operating conditions of 2 wt.%, 30 °C, 60 mm Hg(abs), and 0.6 L/min feed (concentration, temperature, permeate vacuum pressure, and flow rate, respectively). The initial feed concentration, vacuum pressure, and feed flow rate have a lower impact on the permeation flux. Full article

(This article belongs to the Special Issue Chitosan-Based Membranes and Films for Water Purification)

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17 pages, 1820 KiB

Open AccessArticle

Extraction and Characterization of Antioxidant Compounds in Almond (Prunus amygdalus) Shell Residues for Food Packaging Applications

by Arantzazu Valdés, María Carmen Garrigós and Alfonso Jiménez

Membranes 2022, 12(8), 806; https://doi.org/10.3390/membranes12080806 - 20 Aug 2022

Cited by 3 | Viewed by 1994

Abstract

This work proposes the revalorization of almond shell (AS) wastes as an active additive for food packaging applications. A new microwave-assisted extraction (MAE) method to obtain extracts rich in polyphenolic compounds with high antioxidant capacity was optimized. An experimental design to optimize the [...] Read more.

This work proposes the revalorization of almond shell (AS) wastes as an active additive for food packaging applications. A new microwave-assisted extraction (MAE) method to obtain extracts rich in polyphenolic compounds with high antioxidant capacity was optimized. An experimental design to optimize the MAE procedure through response surface methodology (RSM) using a Box–Behnken design was proposed. The effects of extraction temperature, irradiation time, ethanol:water concentration, and solvent pH at three levels were evaluated in terms of total phenolic content (TPC) and antioxidant activity (DPPH (2,2-diphenyl-1-picrylhydrazyl) and ferric reducing antioxidant power (FRAP) assays). The optimal conditions found were 57 min, 80 °C, pH 8, and 70% (v/v) ethanol. Optimized MAE extracts showed low soluble protein content (0.43 mg BSA g⁻¹) and were rich in TPC (5.64 mg GAE g⁻¹), flavonoids (1.42 mg CE g⁻¹), and polysaccharides (1.59 mg glucose g⁻¹), with good antioxidant capacity (2.82 mg AAE acid g⁻¹). These results suggest the potential application of these extracts in the food industry as active additives. This strategy opens new pathways to valorize almond shell residues, contributing to the circular economy. Full article

(This article belongs to the Special Issue Biodegradable Films Characterization and Food Packaging)

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16 pages, 2776 KiB

Open AccessArticle

Tuning the Gas Separation Performances of Smectic Liquid Crystalline Polymer Membranes by Molecular Engineering

by Joey Kloos, Menno Houben, Johan Lub, Kitty Nijmeijer, Albert P. H. J. Schenning and Zandrie Borneman

Membranes 2022, 12(8), 805; https://doi.org/10.3390/membranes12080805 - 20 Aug 2022

Cited by 4 | Viewed by 1680

Abstract

The effect of layer spacing and halogenation on the gas separation performances of free-standing smectic LC polymer membranes is being investigated by molecular engineering. LC membranes with various layer spacings and halogenated LCs were fabricated while having a planar aligned smectic morphology. Single [...] Read more.

The effect of layer spacing and halogenation on the gas separation performances of free-standing smectic LC polymer membranes is being investigated by molecular engineering. LC membranes with various layer spacings and halogenated LCs were fabricated while having a planar aligned smectic morphology. Single permeation and sorption data show a correlation between gas diffusion and layer spacing, which results in increasing gas permeabilities with increasing layer spacing while the ideal gas selectivity of He over CO₂ or He over N₂ decreases. The calculated diffusion coefficients show a 6-fold increase when going from membranes with a layer spacing of 31.9 Å to membranes with a layer spacing of 45.2 Å, demonstrating that the layer spacing in smectic LC membranes mainly affects the diffusion of gasses rather than their solubility. A comparison of gas sorption and permeation performances of smectic LC membranes with and without halogenated LCs shows only a limited effect of LC halogenation by a slight increase in both solubility and diffusion coefficients for the membranes with halogenated LCs, resulting in a slightly higher gas permeation and increased ideal gas selectivities towards CO₂. These results show that layer spacing plays an important role in the gas separation performances of smectic LC polymer membranes. Full article

(This article belongs to the Special Issue Elucidating Mass Transfer Processes in Membranes for Gas Separation)

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25 pages, 8879 KiB

Open AccessArticle

Preparation and Characterization of Chitosan/TiO₂ Composite Membranes as Adsorbent Materials for Water Purification

by Angela Spoială, Cornelia-Ioana Ilie, Georgiana Dolete, Alexa-Maria Croitoru, Vasile-Adrian Surdu, Roxana-Doina Trușcă, Ludmila Motelica, Ovidiu-Cristian Oprea, Denisa Ficai, Anton Ficai, Ecaterina Andronescu and Lia-Mara Dițu

Membranes 2022, 12(8), 804; https://doi.org/10.3390/membranes12080804 - 20 Aug 2022

Cited by 37 | Viewed by 3794

Abstract

As it is used in all aspects of human life, water has become more and more polluted. For the past few decades, researchers and scientists have focused on developing innovative composite adsorbent membranes for water purification. The purpose of this research was to [...] Read more.

As it is used in all aspects of human life, water has become more and more polluted. For the past few decades, researchers and scientists have focused on developing innovative composite adsorbent membranes for water purification. The purpose of this research was to synthesize a novel composite adsorbent membrane for the removal of toxic pollutants (namely heavy metals, antibiotics and microorganisms). The as-synthesized chitosan/TiO₂ composite membranes were successfully prepared through a simple casting method. The TiO₂ nanoparticle concentration from the composite membranes was kept low, at 1% and 5%, in order not to block the functional groups of chitosan, which are responsible for the adsorption of metal ions. Nevertheless, the concentration of TiO₂ must be high enough to bestow good photocatalytic and antimicrobial activities. The synthesized composite membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and swelling capacity. The antibacterial activity was determined against four strains, Escherichia coli, Citrobacter spp., Enterococcus faecalis and Staphylococcus aureus. For the Gram-negative strains, a reduction of more than 5 units log CFU/mL was obtained. The adsorption capacity for heavy metal ions was maximum for the chitosan/TiO₂ 1% composite membrane, the retention values being 297 mg/g for Pb²⁺ and 315 mg/g for Cd²⁺ ions. These values were higher for the chitosan/TiO₂ 1% than for chitosan/TiO₂ 5%, indicating that a high content of TiO₂ can be one of the reasons for modest results reported previously in the literature. The photocatalytic degradation of a five-antibiotic mixture led to removal efficiencies of over 98% for tetracycline and meropenem, while for vancomycin and erythromycin the efficiencies were 86% and 88%, respectively. These values indicate that the chitosan/TiO₂ composite membranes exhibit excellent photocatalytic activity under visible light irradiation. The obtained composite membranes can be used for complex water purification processes (removal of heavy metal ions, antibiotics and microorganisms). Full article

(This article belongs to the Special Issue Chitosan-Based Membranes and Films for Water Purification)

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13 pages, 2917 KiB

Open AccessArticle

Study on Spacing Regulation and Separation Performance of Nanofiltration Membranes of GO

by Na Meng, Pinping Zhao, Wei Zhou, Jie Yan, Die Hu, Yanqing Fang, Jun Lu and Qiang Liu

Membranes 2022, 12(8), 803; https://doi.org/10.3390/membranes12080803 - 19 Aug 2022

Cited by 1 | Viewed by 1381

Abstract

Graphene oxide (GO) membranes have attracted significant attention in the field of water processing in recent years due to their unique characteristics. However, few reports focus on both membrane stability and the “trade-off” effect. In this study, a series of aliphatic diamines (1, [...] Read more.

Graphene oxide (GO) membranes have attracted significant attention in the field of water processing in recent years due to their unique characteristics. However, few reports focus on both membrane stability and the “trade-off” effect. In this study, a series of aliphatic diamines (1, 2-ethylenediamine, 1, 4-butanediamine, and 1, 6-hexamethylenediamine) of covalent crosslinked GO were used to prepare diamine-modified nanofiltration membranes, BPPO/AX-GO, with adjustable layer spacing using the vacuum extraction–filtration method. Moreover, Ax-GO-modified nanofiltration membranes modified with adipose diamine had higher layer spacing, lower mass-transfer resistance, and better stability. When the number of carbon atoms was 5, the best layer spacing was reached, and when the number of carbon atoms was greater than 4, the modified membrane nanosheets more easily accumulated. With the increase in layer spacing, the water flux of the composite film increased to 26.27 L/m²·h·bar. Meanwhile, adipose diamine crosslinking significantly improved the stability of GO films. The interception sequence of different valence salts in the composite membrane was NaCl > Na₂SO₄ > MgSO₄, and the rejection rate of bivalent salts was higher than that of monovalent salts. The results can provide some experimental basis and research ideas for overcoming the “trade-off” effect of a lamellar GO membrane. Full article

(This article belongs to the Special Issue Ion-Selective Separation Membrane)

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18 pages, 7604 KiB

Open AccessArticle

Analysis and Experimental Study on Water Vapor Partial Pressure in the Membrane Distillation Process

by Zanshe Wang, Zhaoying Jia, Ran Li, Qi Gao and Zhaolin Gu

Membranes 2022, 12(8), 802; https://doi.org/10.3390/membranes12080802 - 19 Aug 2022

Cited by 3 | Viewed by 1951

Abstract

In membrane distillation, the vapor pressure difference is the driving force of mass transfer. The vapor pressure is generally assumed by the saturation pressure and calculated by the Antoine equation. However, in the actual operation process, the feed solutions usually flow in a [...] Read more.

In membrane distillation, the vapor pressure difference is the driving force of mass transfer. The vapor pressure is generally assumed by the saturation pressure and calculated by the Antoine equation. However, in the actual operation process, the feed solutions usually flow in a non-equilibrium state, which does not meet the theoretical and measurement conditions of the vapor-liquid equilibrium (VLE) state. This study tested the actual water vapor pressure of the pure water, lithium bromide (LiBr) solution, lithium chloride (LiCl) solution, and calcium chloride (CaCl₂) solution under different flow conditions. The results showed that the actual water vapor pressure was lower than the saturation pressure overall, and the difference increased with temperature but decreased with the mass concentration. Therefore, in vacuum membrane distillation (VMD), air gap membrane distillation (AGMD), and sweeping gas membrane distillation (SGMD), the membrane flux calculated by water vapor saturation pressure was higher than the actual membrane flux, and the relative difference decreased and was less than 10% after 60 °C. In direct contact membrane distillation (DCMD), the water vapor pressure difference on both membrane sides was almost the same by using the saturation vapor pressure or the tested data since the pressure errors were partially offset in parallel flow or counter-flow modes. Full article

(This article belongs to the Special Issue Theoretical and Experimental Investigation of the Mass and Heat Transfers in Membrane Separation Processes)

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18 pages, 2430 KiB

Open AccessArticle

Comparative Analysis of Bio-Vanillin Recovery from Bioconversion Media Using Pervaporation and Vacuum Distillation

by Rita Valério, Carla Brazinha and João G. Crespo

Membranes 2022, 12(8), 801; https://doi.org/10.3390/membranes12080801 - 19 Aug 2022

Cited by 2 | Viewed by 1840

Abstract

The increasing demand for natural products has led to biotechnological vanillin production, which requires the recovery of vanillin (and vanillyl alcohol at trace concentrations, as in botanical vanillin) from the bioconversion broth, free from potential contaminants: the substrate and metabolites of bioconversion. This [...] Read more.

The increasing demand for natural products has led to biotechnological vanillin production, which requires the recovery of vanillin (and vanillyl alcohol at trace concentrations, as in botanical vanillin) from the bioconversion broth, free from potential contaminants: the substrate and metabolites of bioconversion. This work discusses the recovery and fractionation of bio-vanillin, from a bioconversion broth, by pervaporation and by vacuum distillation, coupled with fractionated condensation. The objective was to recover vanillin free of potential contaminants, with maximised fluxes and selectivity for vanillin against water and minimised energy consumption per mass of vanillin recovered. In vacuum distillation fractionated condensation, adding several consecutive water pulses to the feed increased the percentage of recovered vanillin. In pervaporation-fractionated condensation and vacuum distillation-fractionated condensation processes, it was possible to recover vanillin and traces of vanillyl alcohol without the presence of potential contaminants. Vacuum distillation–experiments presented higher vanillin fluxes than pervaporation fractionated condensation experiments, 2.7 ± 0.1 g·m⁻² h⁻¹ and 1.19 ± 0.01 g·m⁻² h⁻¹, respectively. However, pervaporation fractionated condensation assures a selectivity of vanillin against water of 4.5 on the pervaporation step (acting as a preconcentration step) and vacuum distillation fractionated condensation requires a higher energy consumption per mass of vanillin recovered when compared with pervaporation– fractionated condensation, 2727 KWh kg_VAN⁻¹ at 85 °C and 1361 KWh kg_VAN⁻¹ at 75 °C, respectively. Full article

(This article belongs to the Section Membrane Processing and Engineering)

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17 pages, 5546 KiB

Open AccessArticle

Effect of Silica Sodalite Loading on SOD/PSF Membranes during Treatment of Phenol-Containing Wastewater

by Olawumi O. Sadare, Rivoningo Ngobeni and Michael O. Daramola

Membranes 2022, 12(8), 800; https://doi.org/10.3390/membranes12080800 - 19 Aug 2022

Cited by 2 | Viewed by 1303

Abstract

In this study, silica sodalite (SSOD) was prepared via topotactic conversion and different silica sodalite loadings were infused into the polysulfone (PSF) for application in phenol-containing water treatment. The composite membranes were fabricated through the phase inversion technique. Physicochemical characteristics of the nanoparticles [...] Read more.

In this study, silica sodalite (SSOD) was prepared via topotactic conversion and different silica sodalite loadings were infused into the polysulfone (PSF) for application in phenol-containing water treatment. The composite membranes were fabricated through the phase inversion technique. Physicochemical characteristics of the nanoparticles and membranes were checked using a Scanning Electron Microscope (SEM), Brunauer Emmett–Teller (BET), and Fourier Transform Infrared (FTIR) for surface morphology, textural properties, and surface chemistry, respectively. A nanotensile test, Atomic Force Microscopy (AFM), and contact angle measurement were used to check the mechanical properties, surface roughness, and hydrophilicity of the membranes, respectively. SEM results revealed that the pure polysulfone surface is highly porous with large evident pores. However, the pores decreased with increasing SSOD loading. The performance of the fabricated membranes was evaluated using a dead-end filtration device at varying feed pressure during phenol-containing water treatment. The concentration of phenol in water used in this study was 20 mg/L. The pure PSF displayed the maximum phenol rejection of 95 55% at 4 bar, compared to the composite membranes having 61.35% and 64.75% phenol rejection for 5 wt.% SSOD loading and 10 wt.% SSOD loading, respectively. In this study, a novel Psf-infused SSOD membrane was successfully fabricated for the treatment of synthetic phenol-containing water to alleviate the challenges associated with it. Full article

(This article belongs to the Special Issue Membrane Process Systems and Techniques)

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13 pages, 4759 KiB

Open AccessArticle

A Zero-Brine Discharge Seawater Desalination Using a Pilot-Scale Membrane Distillation System Integrated with Crystallizer

by Jian Zuo, Chin Ann Chow, Ludovic F. Dumée and Antony J. Prince

Membranes 2022, 12(8), 799; https://doi.org/10.3390/membranes12080799 - 19 Aug 2022

Cited by 3 | Viewed by 3285

Abstract

The management of brines generated from reverse osmosis operation remains a critical challenge requiring new approaches and processes to limit the impact of brine discharge onto ecosystems and to enhance both water and valuable resource recovery. The treatment of real seawater reverse osmosis [...] Read more.

The management of brines generated from reverse osmosis operation remains a critical challenge requiring new approaches and processes to limit the impact of brine discharge onto ecosystems and to enhance both water and valuable resource recovery. The treatment of real seawater reverse osmosis (SWRO) brines (45,000 ppm TDS) obtained from a local Singaporean desalination plant with a crystallizer integrated pilot-scale membrane distillation unit (MDC) was studied. Commercial STOMATE^® hollow fiber membranes were used in vacuum membrane distillation (VMD) configuration, leading to an average flux of around 3.7 L/m²-h at a permeate vacuum of 80 kPa and an average feed temperature of 65 °C. Consistent separation operations were achieved for the treatment of real SWRO brine over a period of 280 h; this led to a water recovery of >95% and to the collection of salt slurries, containing up to ~10–20 wt% of moisture, from the crystallizer. This approach demonstrates the potential of MDC systems to achieve zero brine discharge efficiently from seawater desalination systems, providing an environmentally friendly alternative to manage brines by increasing water recovery and generating salt slurries of economic value. Full article

(This article belongs to the Section Membrane Applications)

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37 pages, 4833 KiB

Open AccessReview

Adsorptive Membrane for Boron Removal: Challenges and Future Prospects

by Shaymala Mehanathan, Juhana Jaafar, Atikah Mohd Nasir, Roshanida A. Rahman, Ahmad Fauzi Ismail, Rosli Md Illias, Mohd Hafiz Dzarfan Othman, Mukhlis A Rahman, Muhammad Roil Bilad and Muhammad Nihal Naseer

Membranes 2022, 12(8), 798; https://doi.org/10.3390/membranes12080798 - 18 Aug 2022

Cited by 8 | Viewed by 2613

Abstract

The complexity of removing boron compounds from aqueous systems has received serious attention among researchers and inventors in the water treating industry. This is due to the higher level of boron in the aquatic ecosystem, which is caused by the geochemical background and [...] Read more.

The complexity of removing boron compounds from aqueous systems has received serious attention among researchers and inventors in the water treating industry. This is due to the higher level of boron in the aquatic ecosystem, which is caused by the geochemical background and anthropogenic factors. The gradual increase in the distribution of boron for years can become extremely toxic to humans, terrestrial organisms and aquatic organisms. Numerous methods of removing boron that have been executed so far can be classified under batch adsorption, membrane-based processes and hybrid techniques. Conventional water treatments such as coagulation, sedimentation and filtration do not significantly remove boron, and special methods would have to be installed in order to remove boron from water resources. The blockage of membrane pores by pollutants in the available membrane technologies not only decreases their performance but can make the membranes prone to fouling. Therefore, the surface-modifying flexibility in adsorptive membranes can serve as an advantage to remove boron from water resources efficiently. These membranes are attractive because of the dual advantage of adsorption/filtration mechanisms. Hence, this review is devoted to discussing the capabilities of an adsorptive membrane in removing boron. This study will mainly highlight the issues of commercially available adsorptive membranes and the drawbacks of adsorbents incorporated in single-layered adsorptive membranes. The idea of layering adsorbents to form a highly adsorptive dual-layered membrane for boron removal will be proposed. The future prospects of boron removal in terms of the progress and utilization of adsorptive membranes along with recommendations for improving the techniques will also be discussed further. Full article

(This article belongs to the Section Membrane Applications)

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15 pages, 5260 KiB

Open AccessArticle

Design of Enzyme Loaded W/O Emulsions by Direct Membrane Emulsification for CO₂ Capture

by Suchintan Mondal, Bhavna Alke, Aline Machado de Castro, Paloma Ortiz-Albo, Usman Taqui Syed, João G. Crespo and Carla Brazinha

Membranes 2022, 12(8), 797; https://doi.org/10.3390/membranes12080797 - 18 Aug 2022

Cited by 3 | Viewed by 1710

Abstract

Membrane-based gas separation is a promising unit operation in a low-carbon economy due to its simplicity, ease of operation, reduced energy consumption and portability. A methodology is proposed to immobilise enzymes in stable water-in-oil (W/O) emulsions produced by direct membrane emulsification systems and [...] Read more.

Membrane-based gas separation is a promising unit operation in a low-carbon economy due to its simplicity, ease of operation, reduced energy consumption and portability. A methodology is proposed to immobilise enzymes in stable water-in-oil (W/O) emulsions produced by direct membrane emulsification systems and thereafter impregnated them in the pores of a membrane producing emulsion-based supported liquid membranes. The selected case-study was for biogas (CO₂ and CH₄) purification. Upon initial CO₂ sorption studies, corn oil was chosen as a low-cost and non-toxic bulk phase (oil phase). The emulsions were prepared with Nadir^® UP150 P flat-sheet polymeric membranes. The optimised emulsions consisted of 2% Tween 80 (w/w) in corn oil as the continuous phase and 0.5 g.L⁻¹ carbonic anhydrase enzyme with 5% PEG 300 (w/w) in aqueous solution as the dispersed phase. These emulsions were impregnated onto a porous hydrophobic PVDF membrane to prepare a supported liquid membrane for gas separation. Lastly, gas permeability studies indicated that the permeability of CO₂ increased by ~15% and that of CH₄ decreased by ~60% when compared to the membrane without carbonic anhydrase. Thus, a proof-of-concept for enhancement of CO₂ capture using emulsion-based supported liquid membrane was established. Full article

(This article belongs to the Special Issue Novel Membranes for Molecular Separations)

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11 pages, 5448 KiB

Open AccessArticle

Conversion of Carbon Dioxide into Chemical Vapor Deposited Graphene with Controllable Number of Layers via Hydrogen Plasma Pre-Treatment

by Yotsarayuth Seekaew, Nantikan Tammanoon, Adisorn Tuantranont, Tanom Lomas, Anurat Wisitsoraat and Chatchawal Wongchoosuk

Membranes 2022, 12(8), 796; https://doi.org/10.3390/membranes12080796 - 18 Aug 2022

Cited by 6 | Viewed by 2945

Abstract

In this work, we report the conversion of carbon dioxide (CO₂) gas into graphene on copper foil by using a thermal chemical vapor deposition (CVD) method assisted by hydrogen (H₂) plasma pre-treatment. The synthesized graphene has been characterized by [...] Read more.

In this work, we report the conversion of carbon dioxide (CO₂) gas into graphene on copper foil by using a thermal chemical vapor deposition (CVD) method assisted by hydrogen (H₂) plasma pre-treatment. The synthesized graphene has been characterized by Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results show the controllable number of layers (two to six layers) of high-quality graphene by adjusting H₂ plasma pre-treatment powers (100–400 W). The number of layers is reduced with increasing H₂ plasma pre-treatment powers due to the direct modification of metal catalyst surfaces. Bilayer graphene can be well grown with H₂ plasma pre-treatment powers of 400 W while few-layer graphene has been successfully formed under H₂ plasma pre-treatment powers ranging from 100 to 300 W. The formation mechanism is highlighted. Full article

(This article belongs to the Collection Feature Papers in Membrane Surface and Interfaces)

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11 pages, 1556 KiB

Open AccessArticle

PB1F2 from Influenza A Virus Regulates the Interaction between Cytochrome C and Cardiolipin

by Yujuan Wang and Junfeng Wang

Membranes 2022, 12(8), 795; https://doi.org/10.3390/membranes12080795 - 18 Aug 2022

Cited by 2 | Viewed by 1531

Abstract

PB1F2 is a membrane associated protein encoded by the influenza virus gene in the host. Similar to endogenous pro-apoptotic proteins, it acts on the mitochondria of the host immune cells, inducing apoptosis of the cells. The PB1F2 protein has been demonstrated to facilitate [...] Read more.

PB1F2 is a membrane associated protein encoded by the influenza virus gene in the host. Similar to endogenous pro-apoptotic proteins, it acts on the mitochondria of the host immune cells, inducing apoptosis of the cells. The PB1F2 protein has been demonstrated to facilitate the release of cytochrome c in addition to impairing the integrity of the inner mitochondrial membrane. This investigation focused on how the protein PB1F2 interacted with cardiolipin and cytochrome c. The regulation of PB1F2 on the binding of cytochrome c to cardiolipin in two kinds of in vitro membrane mimics was investigated by biophysical techniques. PB1F2 aids in the dissociation of cytochrome c-cardiolipin complexes in liposomes and nanodiscs. The results provide novel explanations and evidence for how PB1F2 functions as a viral virulence factor by inducing immune cell death. Full article

(This article belongs to the Special Issue Artificial Models of Biological Membranes)

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12 pages, 3370 KiB

Open AccessArticle

Long-Chain Modification of the Tips and Inner Walls of MWCNTs and Their Nanocomposite Reverse Osmosis Membranes

by Qing Li, Dengfeng Yang, Qingzhi Liu, Jianhua Wang, Zhun Ma, Dongmei Xu and Jun Gao

Membranes 2022, 12(8), 794; https://doi.org/10.3390/membranes12080794 - 18 Aug 2022

Viewed by 1078

Abstract

Multi-walled carbon nanotubes (MWCNTs) were modified on the tips and inner walls by 12-chloro-12-oxododecanedioic acid-methyl ester groups and then added to the polyamide composite membranes to prepare MWCNT-CH₂OCOC₁₂H₂₃O₂ membranes for desalination. The characterization results of transmission [...] Read more.

Multi-walled carbon nanotubes (MWCNTs) were modified on the tips and inner walls by 12-chloro-12-oxododecanedioic acid-methyl ester groups and then added to the polyamide composite membranes to prepare MWCNT-CH₂OCOC₁₂H₂₃O₂ membranes for desalination. The characterization results of transmission electron microscopy, Fourier transform, infrared transform, and thermogravimetric analysis showed that the 12-chloro-12-oxododecanedioic acid-methyl ester group was successfully grafted to the entrances and inner walls of the MWCNTs. The performance of the MWCNTs’ composite membranes was evaluated by scanning electron microscopy, contact angle, and filtration test. The modified membrane morphology is more uniform, and there is no structural damage. The grafting of carbon nanotubes with methyl 12-chloro-12-oxydodecyldicarboxylate could improve the hydrophilicity of the membrane. Under identical conditions, the water flux of MWCNT-CH₂OCOC₁₂H₂₃O₂ membranes was higher than that of the pristine carbon nanotube’s membrane, and the desalination rate was also slightly improved. Full article

(This article belongs to the Special Issue Nanotechnology and Hybrid Membranes)

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13 pages, 1848 KiB

Open AccessArticle

Experimental Investigations on the Performance of a Hollow Fiber Membrane Evaporative Cooler (HFMEC) in Hot–Dry Regions

by Nanfeng Li, Tao Zhong, Lu Zhou, Simin Huang, Si Zeng and Caihang Liang

Membranes 2022, 12(8), 793; https://doi.org/10.3390/membranes12080793 - 18 Aug 2022

Cited by 7 | Viewed by 1503

Abstract

The applicability of a hollow fiber membrane evaporative cooler in hot–dry regions was investigated by experimental studies. To better understand the actual operating environment of the hollow fiber membrane evaporative cooler, the outdoor air design conditions for summer air conditioning in five cities [...] Read more.

The applicability of a hollow fiber membrane evaporative cooler in hot–dry regions was investigated by experimental studies. To better understand the actual operating environment of the hollow fiber membrane evaporative cooler, the outdoor air design conditions for summer air conditioning in five cities were simulated by an enthalpy difference laboratory. Subsequently, the effects of water and air flow rates on outlet air parameters and performance parameters were investigated by setting-up a hollow fiber membrane evaporative cooling experimental rig. It was found that the hollow fiber membrane evaporative cooler has good application prospects in hot–dry regions such as Lanzhou, Xi’an, Yinchuan, Urumqi, and Karamay. Among them, the hollow fiber membrane evaporative cooler has higher applicability in regions with higher air temperatures and lower humidity such as Urumqi and Karamay. The results indicate that the air outlet temperature and relative humidity ranged from 26.5 °C to 30.8 °C and 63.5% to 82.8%, respectively. The outlet air temperature and relative humidity of the HFMEC can meet the thermal comfort requirements of hot–dry regions in the summer at an appropriate air flow rate. The maximum air temperature drop, wet-bulb efficiency, cooling capacity, and COP were 7.5 °C, 62.9%, 396.4 W, and 4.81, respectively. In addition, the effect of the air flow rate on the performance parameters was more significant than that of the water flow rate. Full article

(This article belongs to the Special Issue Separation of Greenhouse Gases Using Hollow Fiber Membrane Contactor)

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14 pages, 4570 KiB

Open AccessArticle

Seawater Reverse Osmosis Performance Decline Caused by Short-Term Elevated Feed Water Temperature

by Thomas Altmann, Paulus J. Buijs, Andreia S. F. Farinha, Vitor R. Proença Borges, Nadia M. Farhat, Johannes S. Vrouwenvelder and Ratul Das

Membranes 2022, 12(8), 792; https://doi.org/10.3390/membranes12080792 - 18 Aug 2022

Cited by 7 | Viewed by 3768

Abstract

The shortage of fresh water resources has made the desalination of seawater a widely adopted technology. Seawater reverse osmosis (SWRO) is the most commonly used method for desalination. The SWRO process is energy-intensive, and most of the energy in SWRO is spent on [...] Read more.

The shortage of fresh water resources has made the desalination of seawater a widely adopted technology. Seawater reverse osmosis (SWRO) is the most commonly used method for desalination. The SWRO process is energy-intensive, and most of the energy in SWRO is spent on pressurizing the seawater to overcome the osmotic barrier for producing fresh water. The pressure needed depends on the salinity of the seawater, its temperature, and the membrane surface properties. Membrane compaction occurs in SWRO due to hydraulic pressure application for long-term operations and operating temperature fluctuations due to seasonal seawater changes. This study investigates the effects of short-term feed water temperature increase on the SWRO process in a full-scale pilot with pretreatment and a SWRO installation consisting of a pressure vessel which contains seven industrial-scale 8” diameter spiral wound membrane elements. A SWRO feed water temperature of 40 °C, even for a short period of 7 days, caused a permanent performance decline illustrated by a strong specific energy consumption increase of 7.5%. This study highlights the need for membrane manufacturer data that account for the water temperature effect on membrane performance over a broad temperature range. There is a need to develop new membranes that are more tolerant to temperature fluctuations. Full article

(This article belongs to the Special Issue Novel Membranes for Desalination)

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17 pages, 4762 KiB

Open AccessArticle

Interaction of Oxicam Derivatives with the Artificial Models of Biological Membranes—Calorimetric and Fluorescence Spectroscopic Study

by Jadwiga Maniewska, Żaneta Czyżnikowska, Berenika M. Szczęśniak-Sięga and Krystyna Michalak

Membranes 2022, 12(8), 791; https://doi.org/10.3390/membranes12080791 - 17 Aug 2022

Cited by 1 | Viewed by 1857

Abstract

The modified 1,2-benzothiazine analogues designed as new drug candidates and discussed in this paper are oxicam derivatives. Oxicams are a class of non-steroidal anti-inflammatory drugs (NSAIDs). Their biological target is cyclooxygenase (COX), a membrane protein associated with the phospholipid bilayer. In recent decades, [...] Read more.

The modified 1,2-benzothiazine analogues designed as new drug candidates and discussed in this paper are oxicam derivatives. Oxicams are a class of non-steroidal anti-inflammatory drugs (NSAIDs). Their biological target is cyclooxygenase (COX), a membrane protein associated with the phospholipid bilayer. In recent decades, it has been proven that the biological effect of NSAIDs may be closely related to their interaction at the level of the biological membrane. These processes are often complicated and the biological membranes themselves are very complex. Therefore, to study these mechanisms, simplified models of biological membranes are used. To characterize the interaction of six oxicam derivatives with DPPC, DMPC and EYPC, artificial models of biological membranes (multi-bilayers or liposomes), differential scanning calorimetry (DSC) and fluorescence spectroscopy techniques were applied. In spectroscopic measurements, two fluorescent probes (Laurdan and Prodan) localized in different membrane segments were used. All tested oxicam derivatives interacted with the lipid bilayers and may penetrate the artificial models of biological membranes. They intercalated into the lipid bilayers and were located in the vicinity of the polar/apolar membrane interface. Moreover, a good drug candidate should not only have high efficiency against a molecular target but also exhibit strictly defined ADMET parameters, therefore these activities of the studied compounds were also estimated. Full article

(This article belongs to the Special Issue Artificial Models of Biological Membranes)

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15 pages, 67175 KiB

Open AccessReview

A Review of the Application of Modified Separators in Inhibiting the “shuttle effect” of Lithium–Sulfur Batteries

by Bo-Wen Zhang, Bo Sun, Pei Fu, Feng Liu, Chen Zhu, Bao-Ming Xu, Yong Pan and Chi Chen

Membranes 2022, 12(8), 790; https://doi.org/10.3390/membranes12080790 - 17 Aug 2022

Cited by 16 | Viewed by 2955

Abstract

Lithium-sulfur batteries with high theoretical specific capacity and high energy density are considered to be one of the most promising energy storage devices. However, the “shuttle effect” caused by the soluble polysulphide intermediates migrating back and forth between the positive and negative electrodes [...] Read more.

Lithium-sulfur batteries with high theoretical specific capacity and high energy density are considered to be one of the most promising energy storage devices. However, the “shuttle effect” caused by the soluble polysulphide intermediates migrating back and forth between the positive and negative electrodes significantly reduces the active substance content of the battery and hinders the commercial applications of lithium–sulfur batteries. The separator being far from the electrochemical reaction interface and in close contact with the electrode poses an important barrier to polysulfide shuttle. Therefore, the electrochemical performance including coulombic efficiency and cycle stability of lithium–sulfur batteries can be effectively improved by rationally designing the separator. In this paper, the research progress of the modification of lithium–sulfur battery separators is reviewed from the perspectives of adsorption effect, electrostatic effect, and steric hindrance effect, and a novel modification of the lithium–sulfur battery separator is prospected. Full article

(This article belongs to the Special Issue Mixed-Matrix Membranes and Polymeric Membranes)

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17 pages, 1542 KiB

Open AccessArticle

Sunflower Oilcake as a Potential Source for the Development of Edible Membranes

by Ancuţa Petraru and Sonia Amariei

Membranes 2022, 12(8), 789; https://doi.org/10.3390/membranes12080789 - 17 Aug 2022

Cited by 4 | Viewed by 1342

Abstract

Sunflower oilcake flour (SFOC) resulting from the cold extraction of oil is a rich source of valuable bio-components that stimulated the development of novel, biodegradable and edible films. The films were prepared by incorporating different concentration of sunflower oilcakes (0.1–0.5 g). The obtained [...] Read more.

Sunflower oilcake flour (SFOC) resulting from the cold extraction of oil is a rich source of valuable bio-components that stimulated the development of novel, biodegradable and edible films. The films were prepared by incorporating different concentration of sunflower oilcakes (0.1–0.5 g). The obtained films were characterized in terms of physical, water-affinity, antimicrobial and morphological properties. The edible-film properties were affected significantly by the presence and the level of SFOC added. The water vapor permeability and water vapor transmission rate improved with the amount of SFOC added. However, the solubility, oxygen and grease barrier were slightly lower than control film. SEM analysis revealed a rougher but continuous structure with the increases in sunflower oilcake. Moreover, the films with different SFOC levels were opaque, thus presenting good protection against UV radiation. Overall, the SFOC can be use as raw material to produce edible films with suitable properties and microbiological stability for food-packaging applications. Full article

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