Journal Description
Membranes
Membranes
is an international, peer-reviewed, open access journal, published monthly online by MDPI, covers the broad aspects of the science and technology of both biological and non-biological membranes. European Membrane Society (EMS), Membrane Society of Australasia (MSA) and Polish Membrane Society (PTMem) are affiliated with Membranes and their members receive discounts on the article processing charges.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Ei Compendex, PubMed, PMC, CAPlus / SciFinder, Inspec, and other databases.
- Journal Rank: JCR - Q2 (Chemistry, Physical) / CiteScore - Q2 (Chemical Engineering (miscellaneous))
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.6 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the first half of 2024).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Impact Factor:
3.3 (2023);
5-Year Impact Factor:
3.6 (2023)
Latest Articles
Fouling of Reverse Osmosis (RO) and Nanofiltration (NF) Membranes by Low Molecular Weight Organic Compounds (LMWOCs), Part 1: Fundamentals and Mechanism
Membranes 2024, 14(10), 221; https://doi.org/10.3390/membranes14100221 (registering DOI) - 17 Oct 2024
Abstract
Reverse osmosis (RO) and nanofiltration (NF) are ubiquitous technologies in modern water treatment, finding applications across various sectors. However, the availability of high-quality water suitable for RO/NF feed is diminishing due to droughts caused by global warming, increasing demand, and water pollution. As
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Reverse osmosis (RO) and nanofiltration (NF) are ubiquitous technologies in modern water treatment, finding applications across various sectors. However, the availability of high-quality water suitable for RO/NF feed is diminishing due to droughts caused by global warming, increasing demand, and water pollution. As concerns grow over the depletion of precious freshwater resources, a global movement is gaining momentum to utilize previously overlooked or challenging water sources, collectively known as “marginal water”. Fouling is a serious concern when treating marginal water. In RO/NF, biofouling, organic and colloidal fouling, and scaling are particularly problematic. Of these, organic fouling, along with biofouling, has been considered difficult to manage. The major organic foulants studied are natural organic matter (NOM) for surface water and groundwater and effluent organic matter (EfOM) for municipal wastewater reuse. Polymeric substances such as sodium alginate, humic acid, and proteins have been used as model substances of EfOM. Fouling by low molecular weight organic compounds (LMWOCs) such as surfactants, phenolics, and plasticizers is known, but there have been few comprehensive reports. This review aims to shed light on fouling behavior by LMWOCs and its mechanism. LMWOC foulants reported so far are summarized, and the role of LMWOCs is also outlined for other polymeric membranes, e.g., UF, gas separation membranes, etc. Regarding the mechanism of fouling, it is explained that the fouling is caused by the strong interaction between LMWOC and the membrane, which causes the water permeation to be hindered by LMWOCs adsorbed on the membrane surface (surface fouling) and sorbed inside the membrane pores (internal fouling). Adsorption amounts and flow loss caused by the LMWOC fouling were well correlated with the octanol–water partition coefficient (log P). In part 2, countermeasures to solve this problem and applications using the LMWOCs will be outlined.
Full article
(This article belongs to the Collection Featured Reviews in Membrane Science)
Open AccessReview
The Influence of Cholesterol on Membrane Targeted Bioactive Peptides: Modulating Peptide Activity Through Changes in Bilayer Biophysical Properties
by
Juan M. Giraldo-Lorza, Chad Leidy and Marcela Manrique-Moreno
Membranes 2024, 14(10), 220; https://doi.org/10.3390/membranes14100220 - 17 Oct 2024
Abstract
Cholesterol is a biological molecule that is essential for cellular life. It has unique features in terms of molecular structure and function, and plays an important role in determining the structure and properties of cell membranes. One of the most recognized functions of
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Cholesterol is a biological molecule that is essential for cellular life. It has unique features in terms of molecular structure and function, and plays an important role in determining the structure and properties of cell membranes. One of the most recognized functions of cholesterol is its ability to increase the level of lipid packing and rigidity of biological membranes while maintaining high levels of lateral mobility of the bulk lipids, which is necessary to sustain biochemical signaling events. There is increased interest in designing bioactive peptides that can act as effective antimicrobial agents without causing harm to human cells. For this reason, it becomes relevant to understand how cholesterol can affect the interaction between bioactive peptides and lipid membranes, in particular by modulating the peptides’ ability to penetrate and disrupt the membranes through these changes in membrane rigidity. Here we discuss cholesterol and its role in modulating lipid bilayer properties and discuss recent evidence showing how cholesterol modulates bioactive peptides to different degrees.
Full article
(This article belongs to the Special Issue Recent Advances in Biomembrane Models for Studying Interactions with Bio-/Molecules)
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Figure 1
Figure 1
<p>Secondary structures of representative BAPs using PyMOL 3.0. In brackets are the PDB ID and the origin of the peptides. The colors represent the secondary structures: (<b>a</b>) Indolicidin (PDB ID 8IS3, <span class="html-italic">Bos taurus</span>), (<b>b</b>) Magainin 2 (PDB ID 2MAG, <span class="html-italic">Xenopus laevis</span>), (<b>c</b>) Human β-Defensin-4 (PDB ID 5KI9, <span class="html-italic">Homo sapiens</span>), and (<b>d</b>) Human β-Defensin-2 (PDB ID 1FD4, <span class="html-italic">Homo sapiens</span>).</p> Full article ">Figure 2
<p>Representation of eukaryotic cell plasma membrane. The phospholipid bilayer contains all molecules, including phospholipids, proteins, and cholesterol. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), and sphingomyelin (SM). The irregular representation of the lipid acyl chains of lipids denotes the fluid nature of the bilayer.</p> Full article ">Figure 3
<p>Chemical representation of the head groups and acyl chains of the most abundant phospholipids of eukaryotic cell membranes. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), sphingomyelin (SM), and phosphatidylinositol (PI). The acyl chains range from fully saturated to multiple unsaturated.</p> Full article ">Figure 4
<p>The lipid composition of different organelles throughout the eukaryotic cell. The lipid data in the graphs are presented as a percentage of total phospholipids (PL) in mammals. The cholesterol content is presented as the molar ratio of cholesterol (CHO) with respect to the PL [<a href="#B2-membranes-14-00220" class="html-bibr">2</a>,<a href="#B3-membranes-14-00220" class="html-bibr">3</a>,<a href="#B61-membranes-14-00220" class="html-bibr">61</a>]. * Data was reported in CHO/PL ratio.</p> Full article ">Figure 5
<p>Summary of publications that quantified the phospholipid distribution in mammalian cells. Others are fibroblasts and cancer cells. The colors correspond to PC (<span class="html-fig-inline" id="membranes-14-00220-i001"><img alt="Membranes 14 00220 i001" src="/membranes/membranes-14-00220/article_deploy/html/images/membranes-14-00220-i001.png"/></span>), SM (<span class="html-fig-inline" id="membranes-14-00220-i002"><img alt="Membranes 14 00220 i002" src="/membranes/membranes-14-00220/article_deploy/html/images/membranes-14-00220-i002.png"/></span>), PE (<span class="html-fig-inline" id="membranes-14-00220-i003"><img alt="Membranes 14 00220 i003" src="/membranes/membranes-14-00220/article_deploy/html/images/membranes-14-00220-i003.png"/></span>), and PS (<span class="html-fig-inline" id="membranes-14-00220-i004"><img alt="Membranes 14 00220 i004" src="/membranes/membranes-14-00220/article_deploy/html/images/membranes-14-00220-i004.png"/></span>). Data are presented in ratios based on PC abundance.</p> Full article ">Figure 6
<p>(<b>a</b>) Chemical structure of cholesterol and (<b>b</b>) disposition of cholesterol into the hydrophobic region of the cell membrane.</p> Full article ">
<p>Secondary structures of representative BAPs using PyMOL 3.0. In brackets are the PDB ID and the origin of the peptides. The colors represent the secondary structures: (<b>a</b>) Indolicidin (PDB ID 8IS3, <span class="html-italic">Bos taurus</span>), (<b>b</b>) Magainin 2 (PDB ID 2MAG, <span class="html-italic">Xenopus laevis</span>), (<b>c</b>) Human β-Defensin-4 (PDB ID 5KI9, <span class="html-italic">Homo sapiens</span>), and (<b>d</b>) Human β-Defensin-2 (PDB ID 1FD4, <span class="html-italic">Homo sapiens</span>).</p> Full article ">Figure 2
<p>Representation of eukaryotic cell plasma membrane. The phospholipid bilayer contains all molecules, including phospholipids, proteins, and cholesterol. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), and sphingomyelin (SM). The irregular representation of the lipid acyl chains of lipids denotes the fluid nature of the bilayer.</p> Full article ">Figure 3
<p>Chemical representation of the head groups and acyl chains of the most abundant phospholipids of eukaryotic cell membranes. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), sphingomyelin (SM), and phosphatidylinositol (PI). The acyl chains range from fully saturated to multiple unsaturated.</p> Full article ">Figure 4
<p>The lipid composition of different organelles throughout the eukaryotic cell. The lipid data in the graphs are presented as a percentage of total phospholipids (PL) in mammals. The cholesterol content is presented as the molar ratio of cholesterol (CHO) with respect to the PL [<a href="#B2-membranes-14-00220" class="html-bibr">2</a>,<a href="#B3-membranes-14-00220" class="html-bibr">3</a>,<a href="#B61-membranes-14-00220" class="html-bibr">61</a>]. * Data was reported in CHO/PL ratio.</p> Full article ">Figure 5
<p>Summary of publications that quantified the phospholipid distribution in mammalian cells. Others are fibroblasts and cancer cells. The colors correspond to PC (<span class="html-fig-inline" id="membranes-14-00220-i001"><img alt="Membranes 14 00220 i001" src="/membranes/membranes-14-00220/article_deploy/html/images/membranes-14-00220-i001.png"/></span>), SM (<span class="html-fig-inline" id="membranes-14-00220-i002"><img alt="Membranes 14 00220 i002" src="/membranes/membranes-14-00220/article_deploy/html/images/membranes-14-00220-i002.png"/></span>), PE (<span class="html-fig-inline" id="membranes-14-00220-i003"><img alt="Membranes 14 00220 i003" src="/membranes/membranes-14-00220/article_deploy/html/images/membranes-14-00220-i003.png"/></span>), and PS (<span class="html-fig-inline" id="membranes-14-00220-i004"><img alt="Membranes 14 00220 i004" src="/membranes/membranes-14-00220/article_deploy/html/images/membranes-14-00220-i004.png"/></span>). Data are presented in ratios based on PC abundance.</p> Full article ">Figure 6
<p>(<b>a</b>) Chemical structure of cholesterol and (<b>b</b>) disposition of cholesterol into the hydrophobic region of the cell membrane.</p> Full article ">
Open AccessArticle
Computational Fluid Dynamics Modelling of Hydrogen Production via Water Splitting in Oxygen Membrane Reactors
by
Kai Bittner, Nikolaos Margaritis, Falk Schulze-Küppers, Jörg Wolters and Ghaleb Natour
Membranes 2024, 14(10), 219; https://doi.org/10.3390/membranes14100219 - 17 Oct 2024
Abstract
The utilization of oxygen transport membranes enables the production of high-purity hydrogen by the thermal decomposition of water below 1000 °C. This process is based on a chemical potential gradient across the membrane, which is usually achieved by introducing a reducing gas. Computational
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The utilization of oxygen transport membranes enables the production of high-purity hydrogen by the thermal decomposition of water below 1000 °C. This process is based on a chemical potential gradient across the membrane, which is usually achieved by introducing a reducing gas. Computational fluid dynamics (CFD) can be used to model reactors based on this concept. In this study, a modelling approach for water splitting is presented in which oxygen transport through the membrane acts as the rate-determining process for the overall reaction. This transport step is implemented in the CFD simulation. Both gas compartments are modelled in the simulations. Hydrogen and methane are used as reducing gases. The model is validated using experimental data from the literature and compared with a simplified perfect mixing modelling approach. Although the main focus of this work is to propose an approach to implement the water splitting in CFD simulations, a simulation study was conducted to exemplify how CFD modelling can be utilized in design optimization. Simplified 2-dimensional and rotational symmetric reactor geometries were compared. This study shows that a parallel overflow of the membrane in an elongated reactor is advantageous, as this reduces the back diffusion of the reaction products, which increases the mean driving force for oxygen transport through the membrane.
Full article
(This article belongs to the Section Membrane Applications for Gas Separation)
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Figure 1
Figure 1
<p>Schematic illustration of water splitting in oxygen membrane reactors.</p> Full article ">Figure 2
<p>Representation of the mesh of the membrane and the cells on its surface including the source terms.</p> Full article ">Figure 3
<p>Schematic illustration of a rotational symmetric oxygen membrane reactor with a perpendicular impinged membrane.</p> Full article ">Figure 4
<p>Mesh and results for the base case with <math display="inline"><semantics> <mrow> <msub> <mi>σ</mi> <mrow> <mi>a</mi> <mi>m</mi> <mi>b</mi> </mrow> </msub> <mo>=</mo> <mn>19.6</mn> </mrow> </semantics></math> S/m. A rotational symmetric mesh based on the experimental setup of Cai et al. [<a href="#B5-membranes-14-00219" class="html-bibr">5</a>] was used for the simulation.</p> Full article ">Figure 5
<p>Comparison of the results obtained from the CFD model with the experimentally obtained results by Cai et al. [<a href="#B5-membranes-14-00219" class="html-bibr">5</a>]. The graphs on the left-hand side show the hydrogen production rate on the feed side. The graphs on the right-hand side show the oxygen partial pressures on the feed and sweep side, respectively. The range of the simulated data (red and blue curves) results from the uncertainty in the ambipolar conductivity.</p> Full article ">Figure 5 Cont.
<p>Comparison of the results obtained from the CFD model with the experimentally obtained results by Cai et al. [<a href="#B5-membranes-14-00219" class="html-bibr">5</a>]. The graphs on the left-hand side show the hydrogen production rate on the feed side. The graphs on the right-hand side show the oxygen partial pressures on the feed and sweep side, respectively. The range of the simulated data (red and blue curves) results from the uncertainty in the ambipolar conductivity.</p> Full article ">Figure 6
<p>Mesh of the perpendicular impinged rotational symmetric reactor for the simulation study consisting of 71,000 cells. The geometry is schematically illustrated in <a href="#membranes-14-00219-f003" class="html-fig">Figure 3</a> (rotated by <math display="inline"><semantics> <msup> <mn>90</mn> <mo>∘</mo> </msup> </semantics></math>).</p> Full article ">Figure 7
<p>Mesh of the 2D reactor for the simulation study consisting of 18,000 cells for <math display="inline"><semantics> <mrow> <msub> <mi>L</mi> <mrow> <mi>m</mi> <mi>e</mi> <mi>m</mi> </mrow> </msub> <mo>=</mo> <mn>3</mn> </mrow> </semantics></math> cm and 29,000 cells for <math display="inline"><semantics> <mrow> <msub> <mi>L</mi> <mrow> <mi>m</mi> <mi>e</mi> <mi>m</mi> </mrow> </msub> <mo>=</mo> <mn>9</mn> </mrow> </semantics></math> cm. For the counter-current configuration, the inlet and outlet on the feed side are swapped.</p> Full article ">Figure 8
<p>Simulation results of the <math display="inline"><semantics> <msub> <mi mathvariant="normal">H</mi> <mn>2</mn> </msub> </semantics></math> production rate on the feed side for water splitting using hydrogen as a sweep gas.</p> Full article ">Figure 9
<p>Local oxygen flux simulation results for water splitting using hydrogen as a sweep gas. The results for a feed and sweep flow rate of 0.1 mmol/min/cm<sup>2</sup> are shown.</p> Full article ">Figure 10
<p>Simulation results of the <math display="inline"><semantics> <msub> <mi mathvariant="normal">H</mi> <mn>2</mn> </msub> </semantics></math> production rate on the feed side for water splitting using methane as a sweep gas. The flow rate variation refers to the percentage variation from the base flow rates (base feed flow rate: 0.319 mmol/min/cm<sup>2</sup> and base sweep flow rate: 0.080 mmol/min/cm<sup>2</sup>).</p> Full article ">Figure 11
<p>Local oxygen flux simulation results for water splitting using methane as a sweep gas. The simulation results for the base flow rates are shown (base feed flow rate: 0.319 mmol/min/cm<sup>2</sup> and base sweep flow rate: 0.080 mmol/min/cm<sup>2</sup>).</p> Full article ">Figure 12
<p><math display="inline"><semantics> <msub> <mi>CH</mi> <mn>4</mn> </msub> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi mathvariant="normal">H</mi> <mn>2</mn> </msub> <mi mathvariant="normal">O</mi> </mrow> </semantics></math> conversion simulation results for water splitting using methane as a sweep gas. The flow rate variation refers to the percentage variation from the base flow rates (base feed flow rate: 0.319 mmol/min/cm<sup>2</sup> and base sweep flow rate: 0.080 mmol/min/cm<sup>2</sup>).</p> Full article ">Figure 13
<p><math display="inline"><semantics> <mi>CO</mi> </semantics></math> selectivity simulation results for water splitting using methane as a sweep gas. The flow rate variation refers to the percentage variation from the base flow rates (base feed flow rate: 0.319 mmol/min/cm<sup>2</sup> and base sweep flow rate: 0.080 mmol/min/cm<sup>2</sup>).</p> Full article ">Figure 14
<p>Required heat input for water splitting using methane as a sweep gas. The flow rate variation refers to the percentage variation from the base flow rates (base feed flow rate: 0.319 mmol/min/cm<sup>2</sup> and base sweep flow rate: 0.080 mmol/min/cm<sup>2</sup>).</p> Full article ">Figure 15
<p>Simulated temperature distribution for water splitting using methane as a sweep gas. The results for the base flow rates are shown. For the simulations with parallel flows along the membranes, only the active membrane length regions are shown. The cases (<b>a</b>–<b>e</b>) refer to the CFD models described in <a href="#sec3dot2dot1-membranes-14-00219" class="html-sec">Section 3.2.1</a>.</p> Full article ">
<p>Schematic illustration of water splitting in oxygen membrane reactors.</p> Full article ">Figure 2
<p>Representation of the mesh of the membrane and the cells on its surface including the source terms.</p> Full article ">Figure 3
<p>Schematic illustration of a rotational symmetric oxygen membrane reactor with a perpendicular impinged membrane.</p> Full article ">Figure 4
<p>Mesh and results for the base case with <math display="inline"><semantics> <mrow> <msub> <mi>σ</mi> <mrow> <mi>a</mi> <mi>m</mi> <mi>b</mi> </mrow> </msub> <mo>=</mo> <mn>19.6</mn> </mrow> </semantics></math> S/m. A rotational symmetric mesh based on the experimental setup of Cai et al. [<a href="#B5-membranes-14-00219" class="html-bibr">5</a>] was used for the simulation.</p> Full article ">Figure 5
<p>Comparison of the results obtained from the CFD model with the experimentally obtained results by Cai et al. [<a href="#B5-membranes-14-00219" class="html-bibr">5</a>]. The graphs on the left-hand side show the hydrogen production rate on the feed side. The graphs on the right-hand side show the oxygen partial pressures on the feed and sweep side, respectively. The range of the simulated data (red and blue curves) results from the uncertainty in the ambipolar conductivity.</p> Full article ">Figure 5 Cont.
<p>Comparison of the results obtained from the CFD model with the experimentally obtained results by Cai et al. [<a href="#B5-membranes-14-00219" class="html-bibr">5</a>]. The graphs on the left-hand side show the hydrogen production rate on the feed side. The graphs on the right-hand side show the oxygen partial pressures on the feed and sweep side, respectively. The range of the simulated data (red and blue curves) results from the uncertainty in the ambipolar conductivity.</p> Full article ">Figure 6
<p>Mesh of the perpendicular impinged rotational symmetric reactor for the simulation study consisting of 71,000 cells. The geometry is schematically illustrated in <a href="#membranes-14-00219-f003" class="html-fig">Figure 3</a> (rotated by <math display="inline"><semantics> <msup> <mn>90</mn> <mo>∘</mo> </msup> </semantics></math>).</p> Full article ">Figure 7
<p>Mesh of the 2D reactor for the simulation study consisting of 18,000 cells for <math display="inline"><semantics> <mrow> <msub> <mi>L</mi> <mrow> <mi>m</mi> <mi>e</mi> <mi>m</mi> </mrow> </msub> <mo>=</mo> <mn>3</mn> </mrow> </semantics></math> cm and 29,000 cells for <math display="inline"><semantics> <mrow> <msub> <mi>L</mi> <mrow> <mi>m</mi> <mi>e</mi> <mi>m</mi> </mrow> </msub> <mo>=</mo> <mn>9</mn> </mrow> </semantics></math> cm. For the counter-current configuration, the inlet and outlet on the feed side are swapped.</p> Full article ">Figure 8
<p>Simulation results of the <math display="inline"><semantics> <msub> <mi mathvariant="normal">H</mi> <mn>2</mn> </msub> </semantics></math> production rate on the feed side for water splitting using hydrogen as a sweep gas.</p> Full article ">Figure 9
<p>Local oxygen flux simulation results for water splitting using hydrogen as a sweep gas. The results for a feed and sweep flow rate of 0.1 mmol/min/cm<sup>2</sup> are shown.</p> Full article ">Figure 10
<p>Simulation results of the <math display="inline"><semantics> <msub> <mi mathvariant="normal">H</mi> <mn>2</mn> </msub> </semantics></math> production rate on the feed side for water splitting using methane as a sweep gas. The flow rate variation refers to the percentage variation from the base flow rates (base feed flow rate: 0.319 mmol/min/cm<sup>2</sup> and base sweep flow rate: 0.080 mmol/min/cm<sup>2</sup>).</p> Full article ">Figure 11
<p>Local oxygen flux simulation results for water splitting using methane as a sweep gas. The simulation results for the base flow rates are shown (base feed flow rate: 0.319 mmol/min/cm<sup>2</sup> and base sweep flow rate: 0.080 mmol/min/cm<sup>2</sup>).</p> Full article ">Figure 12
<p><math display="inline"><semantics> <msub> <mi>CH</mi> <mn>4</mn> </msub> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi mathvariant="normal">H</mi> <mn>2</mn> </msub> <mi mathvariant="normal">O</mi> </mrow> </semantics></math> conversion simulation results for water splitting using methane as a sweep gas. The flow rate variation refers to the percentage variation from the base flow rates (base feed flow rate: 0.319 mmol/min/cm<sup>2</sup> and base sweep flow rate: 0.080 mmol/min/cm<sup>2</sup>).</p> Full article ">Figure 13
<p><math display="inline"><semantics> <mi>CO</mi> </semantics></math> selectivity simulation results for water splitting using methane as a sweep gas. The flow rate variation refers to the percentage variation from the base flow rates (base feed flow rate: 0.319 mmol/min/cm<sup>2</sup> and base sweep flow rate: 0.080 mmol/min/cm<sup>2</sup>).</p> Full article ">Figure 14
<p>Required heat input for water splitting using methane as a sweep gas. The flow rate variation refers to the percentage variation from the base flow rates (base feed flow rate: 0.319 mmol/min/cm<sup>2</sup> and base sweep flow rate: 0.080 mmol/min/cm<sup>2</sup>).</p> Full article ">Figure 15
<p>Simulated temperature distribution for water splitting using methane as a sweep gas. The results for the base flow rates are shown. For the simulations with parallel flows along the membranes, only the active membrane length regions are shown. The cases (<b>a</b>–<b>e</b>) refer to the CFD models described in <a href="#sec3dot2dot1-membranes-14-00219" class="html-sec">Section 3.2.1</a>.</p> Full article ">
Open AccessArticle
Cell Type-Specific Anti- and Pro-Oxidative Effects of Punica granatum L. Ellagitannins
by
Ewa Olchowik-Grabarek, Szymon Sekowski, Iga Mierzwinska, Izabela Zukowska, Nodira Abdulladjanova, Vadim Shlyonsky and Maria Zamaraeva
Membranes 2024, 14(10), 218; https://doi.org/10.3390/membranes14100218 (registering DOI) - 15 Oct 2024
Abstract
Pomegranate and its by-products contain a broad spectrum of phytochemicals, such as flavonoids, phenolic acids and tannins, having pleiotropic preventive and prophylactic properties in health disorders related to oxidative stress and microbial contamination. Here, we examined the biological effects of a pomegranate peel
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Pomegranate and its by-products contain a broad spectrum of phytochemicals, such as flavonoids, phenolic acids and tannins, having pleiotropic preventive and prophylactic properties in health disorders related to oxidative stress and microbial contamination. Here, we examined the biological effects of a pomegranate peel ellagitannins-enriched (>90%) extract, PETE. In vitro studies revealed that PETE has a strong antiradical action towards synthetic radicals and biologically relevant ROS surpassing or comparable to that of Trolox. In cellular models, it showed concentration-dependent (25–100 µg/mL) yet opposing effects depending on the cell membrane type and exposure conditions. In erythrocytes, PETE protected membrane integrity in the presence of the strong oxidant HClO and restored reduced glutathione levels to up to 85% of the control value while having much weaker acute and long-term intrinsic effects. Such protection persisted even after the removal of the extract from cells, indicating strong membrane interaction. In HeLa cancer cells, and at concentrations lower than those used for red blood cells, PETE induced robust potentiation of ROS production and mitochondrial potential dissipation, leading to autophagy-like membrane morphology changes and cell death. In S. aureus, the growth arrest and bacterial death in the presence of PETE (with MIC = 31.25 µg/mL and MBC = 125 µg/mL, respectively) can be linked to the tripled ROS induction by the extract in the same concentration range. This study indicates a specificity of ROS production by the pomegranate extract depending on the type of cell, the concentration of the extract and the time of incubation. This specificity witnesses a strong potential of the extract components as candidates in antioxidant and pro-oxidant therapy.
Full article
(This article belongs to the Section Biological Membranes)
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Figure 1
Figure 1
<p>Concentration-dependent free radical scavenging activity of PETE against DPPH (<b>A</b>), ABTS<sup>+</sup>; (<b>B</b>), O<sub>2</sub><sup>−.</sup>; (<b>C</b>) and NO (<b>D</b>). Lines in the graphs represent the best fit of data to the logistic equation (n = 3).</p> Full article ">Figure 2
<p>Protective effect of PETE against oxidative hemolysis (<b>A</b>) and on the level of GSH reduction (<b>B</b>) induced by 1 mM HClO. *** <span class="html-italic">p</span> < 0.001 vs. respective HClO (n = 5).</p> Full article ">Figure 3
<p>HeLa cells viability in the presence of PETE. *** <span class="html-italic">p</span> < 0.0005 vs. control (n = 5).</p> Full article ">Figure 4
<p>HeLa cell morphology. Control (<b>A</b>), HeLa + 75 µg/mL of PETE (<b>B</b>) and HeLa + 150 µg/mL of PETE (<b>C</b>). (Magnification 200×, yellow arrows mark vacuoles). Phase-contrast images are representative of three independent cell culture experiments.</p> Full article ">Figure 5
<p>Generation of ROS in the presence of PETE in HeLa cells. LSCM images of control cell (<b>A</b>) and cells in the presence of 25 µg/mL (<b>B</b>) or 50 µg/mL PETE (<b>C</b>) are shown. (<b>D</b>) Background-subtracted fluorescence intensity of DCF label of at least 50 ROI (cells). *** <span class="html-italic">p</span> < 0.001. Images are representative of three independent cell culture experiments.</p> Full article ">Figure 6
<p>Changes in mitochondrial potential (Ψ<sub>MT</sub>) in the presence of PETE in HeLa cells. LSCM images of control cell (<b>A</b>), and cells in the presence of 25 µg/mL (<b>B</b>) or 50 µg/mL PETE (<b>C</b>), are shown. (<b>D</b>) Background-subtracted fluorescence intensity of TMRM dye in at least 50 ROI (cells), *** <span class="html-italic">p</span> < 0.001 vs. control. Images are representative of three independent cell culture experiments.</p> Full article ">Figure 7
<p>Formation of ROS in the presence of PETE in <span class="html-italic">S. aureus</span> cells. *** <span class="html-italic">p</span> < 0.001 vs. control (n = 5).</p> Full article ">
<p>Concentration-dependent free radical scavenging activity of PETE against DPPH (<b>A</b>), ABTS<sup>+</sup>; (<b>B</b>), O<sub>2</sub><sup>−.</sup>; (<b>C</b>) and NO (<b>D</b>). Lines in the graphs represent the best fit of data to the logistic equation (n = 3).</p> Full article ">Figure 2
<p>Protective effect of PETE against oxidative hemolysis (<b>A</b>) and on the level of GSH reduction (<b>B</b>) induced by 1 mM HClO. *** <span class="html-italic">p</span> < 0.001 vs. respective HClO (n = 5).</p> Full article ">Figure 3
<p>HeLa cells viability in the presence of PETE. *** <span class="html-italic">p</span> < 0.0005 vs. control (n = 5).</p> Full article ">Figure 4
<p>HeLa cell morphology. Control (<b>A</b>), HeLa + 75 µg/mL of PETE (<b>B</b>) and HeLa + 150 µg/mL of PETE (<b>C</b>). (Magnification 200×, yellow arrows mark vacuoles). Phase-contrast images are representative of three independent cell culture experiments.</p> Full article ">Figure 5
<p>Generation of ROS in the presence of PETE in HeLa cells. LSCM images of control cell (<b>A</b>) and cells in the presence of 25 µg/mL (<b>B</b>) or 50 µg/mL PETE (<b>C</b>) are shown. (<b>D</b>) Background-subtracted fluorescence intensity of DCF label of at least 50 ROI (cells). *** <span class="html-italic">p</span> < 0.001. Images are representative of three independent cell culture experiments.</p> Full article ">Figure 6
<p>Changes in mitochondrial potential (Ψ<sub>MT</sub>) in the presence of PETE in HeLa cells. LSCM images of control cell (<b>A</b>), and cells in the presence of 25 µg/mL (<b>B</b>) or 50 µg/mL PETE (<b>C</b>), are shown. (<b>D</b>) Background-subtracted fluorescence intensity of TMRM dye in at least 50 ROI (cells), *** <span class="html-italic">p</span> < 0.001 vs. control. Images are representative of three independent cell culture experiments.</p> Full article ">Figure 7
<p>Formation of ROS in the presence of PETE in <span class="html-italic">S. aureus</span> cells. *** <span class="html-italic">p</span> < 0.001 vs. control (n = 5).</p> Full article ">
Open AccessReview
Efficient Removal of PFASs Using Photocatalysis, Membrane Separation and Photocatalytic Membrane Reactors
by
Nonhle Siphelele Neliswa Mabaso, Charmaine Sesethu Tshangana and Adolph Anga Muleja
Membranes 2024, 14(10), 217; https://doi.org/10.3390/membranes14100217 - 14 Oct 2024
Abstract
Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are persistent compounds characterized by stable C−F bonds giving them high thermal and chemical stability. Numerous studies have highlighted the presence of PFASs in the environment, surface waters and animals and humans. Exposure to these chemicals has been
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Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are persistent compounds characterized by stable C−F bonds giving them high thermal and chemical stability. Numerous studies have highlighted the presence of PFASs in the environment, surface waters and animals and humans. Exposure to these chemicals has been found to cause various health effects and has necessitated the need to develop methods to remove them from the environment. To date, the use of photocatalytic degradation and membrane separation to remove PFASs from water has been widely studied; however, these methods have drawbacks hindering them from being applied at full scale, including the recovery of the photocatalyst, uneven light distribution and membrane fouling. Therefore, to overcome some of these challenges, there has been research involving the coupling of photocatalysis and membrane separation to form photocatalytic membrane reactors which facilitate in the recovery of the photocatalyst, ensuring even light distribution and mitigating fouling. This review not only highlights recent advancements in the removal of PFASs using photocatalysis and membrane separation but also provides comprehensive information on the integration of photocatalysis and membrane separation to form photocatalytic membrane reactors. It emphasizes the performance of immobilized and slurry systems in PFAS removal while also addressing the associated challenges and offering recommendations for improvement. Factors influencing the performance of these methods will be comprehensively discussed, as well as the nanomaterials used for each technology. Additionally, knowledge gaps regarding the removal of PFASs using integrated photocatalytic membrane systems will be addressed, along with a comprehensive discussion on how these technologies can be applied in real-world applications.
Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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Figure 1
Figure 1
<p>(<b>a</b>) Schematic representation of the efffect of light on photocatalytic degradation of PFOA (this work), (<b>b</b>) degradation of PFOA in pure water using UV irradiation, (<b>c</b>) pure water using VUV irradiation and (<b>d</b>) sewage water using UV and VUV irradiation (<b>b</b>–<b>d</b> reproduced with permission from Ref. [<a href="#B24-membranes-14-00217" class="html-bibr">24</a>]).</p> Full article ">Figure 2
<p>Schematic representation of the (<b>a</b>) Effect of pH on photocatalyst’s surface charge (i) and interaction of anionic PFASs and photocatalyst’s surface at different pH values (ii) (this work). (<b>b</b>) Effect of pH on photocatalytic degradation of PFOA and (<b>c</b>) zeta potential of TiO<sub>2</sub> at various pH values (<b>b</b> and <b>c</b> reproduced with permission from Ref. [<a href="#B35-membranes-14-00217" class="html-bibr">35</a>]).</p> Full article ">Figure 3
<p>The effect of solute concentration on the degradation efficiency of PFOA with (<b>a</b>) Pb-BFO/0.5%rGO (reproduced with permission from Ref. [<a href="#B32-membranes-14-00217" class="html-bibr">32</a>]. (<b>b</b>) duo functional tri-metallic-oxide (f-TMO) photocatalyst (reproduced with permission from Ref. [<a href="#B37-membranes-14-00217" class="html-bibr">37</a>]) and (<b>c</b>) BiOI@Bi<sub>5</sub>O<sub>7</sub>I heterojunction photocatalyst (reproduced with permission from Ref. [<a href="#B38-membranes-14-00217" class="html-bibr">38</a>]).</p> Full article ">Figure 4
<p>Schematic representation (<b>a</b>) of the degradation efficiency of PFASs at low photocatalyst dosage(i), optimal dosage(ii) and high dosage (iii) (this work). (<b>b</b>) Degradation of PFOA at various photocatalyst dosages (reproduced with permission from Ref. [<a href="#B41-membranes-14-00217" class="html-bibr">41</a>]).</p> Full article ">Figure 5
<p>Configuration showing adsorption of PFOA on (<b>a</b>) In<sub>2</sub>O<sub>3</sub> and (<b>b</b>) TiO<sub>2</sub>.</p> Full article ">Figure 6
<p>(<b>a</b>) Degradation and (<b>b</b>) defluorination of PFOA using noble metal-doped TiO<sub>2</sub> ((<b>a</b>,<b>b</b>) reproduced with permission from Ref. [<a href="#B49-membranes-14-00217" class="html-bibr">49</a>]); (<b>c</b>) schematic representation of the electron trapping in metal-doped photocatalyst (this work).</p> Full article ">Figure 7
<p>Factors affecting the removal of PFASs via membrane separation.</p> Full article ">Figure 8
<p>Schematic representation of PFAS rejection efficiency in the presence of organic matter, illustrating (<b>a</b>) size exclusion and (<b>b</b>) electrostatic interactions. Black arrows indicate electrostatic exclusion between PFAS molecules and the membrane surface, as well as electrostatic shielding caused by the adsorption of cations in solution, which shields the membrane surface. (Reproduced with permission from Ref. [<a href="#B58-membranes-14-00217" class="html-bibr">58</a>]).</p> Full article ">Figure 9
<p>Rejection of (<b>a</b>) PFCAs and (<b>b</b>) PFSAs using NF membrane in spiked AFFF and groundwater solutions (Reproduced with permission from Ref. [<a href="#B8-membranes-14-00217" class="html-bibr">8</a>]).</p> Full article ">Figure 10
<p>(<b>a</b>) Rejection of PFOS with varying concentrations. (<b>b</b>) Influence of PFOS concentration on the Flux decay rate (F/F<sub>0</sub>): F<sub>0</sub> is the pure water flux; F is the flux at a specific moment in time. (Reproduced with permission from Ref. [<a href="#B62-membranes-14-00217" class="html-bibr">62</a>]).</p> Full article ">Figure 11
<p>(<b>a</b>) Schematic representation of the accumulation of molecules on surface of membrane (this work). (<b>b</b>,<b>c</b>) Rejection and permeate fluxes of PFOA and PFBA at various operation pressures [<a href="#B57-membranes-14-00217" class="html-bibr">57</a>].</p> Full article ">Figure 12
<p>(<b>a</b>) Influence of pH on rejection of PFOS. (<b>b</b>) Zeta potentials of PMIA membrane at various solution pHs (reproduced with permission from Ref. [<a href="#B62-membranes-14-00217" class="html-bibr">62</a>]).</p> Full article ">Figure 13
<p>(<b>a</b>) Formation of CF<sub>3</sub>(CF<sub>2</sub>)<sub>7</sub>SO<sub>3</sub>Ca due to electrostatic interaction between Ca<sup>2+</sup> and negatively charged sulfonate group; (<b>b</b>) formation of CF<sub>3</sub>(CF<sub>2</sub>)<sub>7</sub>SO<sub>3</sub> −Ca− O<sub>3</sub>S(CF<sub>2</sub>)<sub>7</sub>CF<sub>3</sub> through linkage of two PFOS molecules to Ca<sup>2+</sup>.</p> Full article ">Figure 14
<p>Schematic representation of the rejection proficiency of NF membrane for long- and short-chain PFASs (<b>a</b>), effect of organic matter and cations on rejection of long- and short-chain PFAS molecules (<b>b</b>) (this work) and (<b>c</b>) rejection proficiency of RO and NF membranes for long- and short-chain PFASs [<a href="#B57-membranes-14-00217" class="html-bibr">57</a>].</p> Full article ">Figure 15
<p>Schematic representation on the interaction of PFASs with membrane with (<b>a</b>) hydrophobic and (<b>b</b>) hydrophilic surface.</p> Full article ">Figure 16
<p>Schematic diagram showing the adsorption of PFOA onto polyamide barrier layer (<b>a</b>); electrostatic repulsion between polyamide barrier layer modified with carbonyl groups and PFOA (<b>b</b>).</p> Full article ">Figure 17
<p>Schematic diagram showing the removal of PFOA using NF membrane–UV hybrid system.</p> Full article ">Figure 18
<p>Flow diagram of NF/UV–sulphite pilot system for treatment of groundwater (reproduced with permission from Ref. [<a href="#B104-membranes-14-00217" class="html-bibr">104</a>]).</p> Full article ">Figure 19
<p>Schematic representation of an immobilized photocatalytic membrane reactor with crossflow filtration system.</p> Full article ">Figure 20
<p>A schematic diagram showing the photocatalytic degradation of PFOA adsorbed onto the photocatalytic membrane after exposure to UV.</p> Full article ">
<p>(<b>a</b>) Schematic representation of the efffect of light on photocatalytic degradation of PFOA (this work), (<b>b</b>) degradation of PFOA in pure water using UV irradiation, (<b>c</b>) pure water using VUV irradiation and (<b>d</b>) sewage water using UV and VUV irradiation (<b>b</b>–<b>d</b> reproduced with permission from Ref. [<a href="#B24-membranes-14-00217" class="html-bibr">24</a>]).</p> Full article ">Figure 2
<p>Schematic representation of the (<b>a</b>) Effect of pH on photocatalyst’s surface charge (i) and interaction of anionic PFASs and photocatalyst’s surface at different pH values (ii) (this work). (<b>b</b>) Effect of pH on photocatalytic degradation of PFOA and (<b>c</b>) zeta potential of TiO<sub>2</sub> at various pH values (<b>b</b> and <b>c</b> reproduced with permission from Ref. [<a href="#B35-membranes-14-00217" class="html-bibr">35</a>]).</p> Full article ">Figure 3
<p>The effect of solute concentration on the degradation efficiency of PFOA with (<b>a</b>) Pb-BFO/0.5%rGO (reproduced with permission from Ref. [<a href="#B32-membranes-14-00217" class="html-bibr">32</a>]. (<b>b</b>) duo functional tri-metallic-oxide (f-TMO) photocatalyst (reproduced with permission from Ref. [<a href="#B37-membranes-14-00217" class="html-bibr">37</a>]) and (<b>c</b>) BiOI@Bi<sub>5</sub>O<sub>7</sub>I heterojunction photocatalyst (reproduced with permission from Ref. [<a href="#B38-membranes-14-00217" class="html-bibr">38</a>]).</p> Full article ">Figure 4
<p>Schematic representation (<b>a</b>) of the degradation efficiency of PFASs at low photocatalyst dosage(i), optimal dosage(ii) and high dosage (iii) (this work). (<b>b</b>) Degradation of PFOA at various photocatalyst dosages (reproduced with permission from Ref. [<a href="#B41-membranes-14-00217" class="html-bibr">41</a>]).</p> Full article ">Figure 5
<p>Configuration showing adsorption of PFOA on (<b>a</b>) In<sub>2</sub>O<sub>3</sub> and (<b>b</b>) TiO<sub>2</sub>.</p> Full article ">Figure 6
<p>(<b>a</b>) Degradation and (<b>b</b>) defluorination of PFOA using noble metal-doped TiO<sub>2</sub> ((<b>a</b>,<b>b</b>) reproduced with permission from Ref. [<a href="#B49-membranes-14-00217" class="html-bibr">49</a>]); (<b>c</b>) schematic representation of the electron trapping in metal-doped photocatalyst (this work).</p> Full article ">Figure 7
<p>Factors affecting the removal of PFASs via membrane separation.</p> Full article ">Figure 8
<p>Schematic representation of PFAS rejection efficiency in the presence of organic matter, illustrating (<b>a</b>) size exclusion and (<b>b</b>) electrostatic interactions. Black arrows indicate electrostatic exclusion between PFAS molecules and the membrane surface, as well as electrostatic shielding caused by the adsorption of cations in solution, which shields the membrane surface. (Reproduced with permission from Ref. [<a href="#B58-membranes-14-00217" class="html-bibr">58</a>]).</p> Full article ">Figure 9
<p>Rejection of (<b>a</b>) PFCAs and (<b>b</b>) PFSAs using NF membrane in spiked AFFF and groundwater solutions (Reproduced with permission from Ref. [<a href="#B8-membranes-14-00217" class="html-bibr">8</a>]).</p> Full article ">Figure 10
<p>(<b>a</b>) Rejection of PFOS with varying concentrations. (<b>b</b>) Influence of PFOS concentration on the Flux decay rate (F/F<sub>0</sub>): F<sub>0</sub> is the pure water flux; F is the flux at a specific moment in time. (Reproduced with permission from Ref. [<a href="#B62-membranes-14-00217" class="html-bibr">62</a>]).</p> Full article ">Figure 11
<p>(<b>a</b>) Schematic representation of the accumulation of molecules on surface of membrane (this work). (<b>b</b>,<b>c</b>) Rejection and permeate fluxes of PFOA and PFBA at various operation pressures [<a href="#B57-membranes-14-00217" class="html-bibr">57</a>].</p> Full article ">Figure 12
<p>(<b>a</b>) Influence of pH on rejection of PFOS. (<b>b</b>) Zeta potentials of PMIA membrane at various solution pHs (reproduced with permission from Ref. [<a href="#B62-membranes-14-00217" class="html-bibr">62</a>]).</p> Full article ">Figure 13
<p>(<b>a</b>) Formation of CF<sub>3</sub>(CF<sub>2</sub>)<sub>7</sub>SO<sub>3</sub>Ca due to electrostatic interaction between Ca<sup>2+</sup> and negatively charged sulfonate group; (<b>b</b>) formation of CF<sub>3</sub>(CF<sub>2</sub>)<sub>7</sub>SO<sub>3</sub> −Ca− O<sub>3</sub>S(CF<sub>2</sub>)<sub>7</sub>CF<sub>3</sub> through linkage of two PFOS molecules to Ca<sup>2+</sup>.</p> Full article ">Figure 14
<p>Schematic representation of the rejection proficiency of NF membrane for long- and short-chain PFASs (<b>a</b>), effect of organic matter and cations on rejection of long- and short-chain PFAS molecules (<b>b</b>) (this work) and (<b>c</b>) rejection proficiency of RO and NF membranes for long- and short-chain PFASs [<a href="#B57-membranes-14-00217" class="html-bibr">57</a>].</p> Full article ">Figure 15
<p>Schematic representation on the interaction of PFASs with membrane with (<b>a</b>) hydrophobic and (<b>b</b>) hydrophilic surface.</p> Full article ">Figure 16
<p>Schematic diagram showing the adsorption of PFOA onto polyamide barrier layer (<b>a</b>); electrostatic repulsion between polyamide barrier layer modified with carbonyl groups and PFOA (<b>b</b>).</p> Full article ">Figure 17
<p>Schematic diagram showing the removal of PFOA using NF membrane–UV hybrid system.</p> Full article ">Figure 18
<p>Flow diagram of NF/UV–sulphite pilot system for treatment of groundwater (reproduced with permission from Ref. [<a href="#B104-membranes-14-00217" class="html-bibr">104</a>]).</p> Full article ">Figure 19
<p>Schematic representation of an immobilized photocatalytic membrane reactor with crossflow filtration system.</p> Full article ">Figure 20
<p>A schematic diagram showing the photocatalytic degradation of PFOA adsorbed onto the photocatalytic membrane after exposure to UV.</p> Full article ">
Open AccessArticle
Controlled Growth of ZIF-8 Membranes on GO-Coated α-Alumina Supports via ZnO Atomic Layer Deposition for Improved Gas Separation
by
Nahyeon Lee, Yun-Ho Ahn, Jaheon Kim and Kiwon Eum
Membranes 2024, 14(10), 216; https://doi.org/10.3390/membranes14100216 - 14 Oct 2024
Abstract
This study presents a novel approach for fabricating ZIF-8 membranes supported on α-alumina hollow fibers through the introduction of a graphene oxide (GO) gutter layer and the application of zinc oxide (ZnO) Atomic Layer Deposition (ALD). The method successfully addressed key challenges, including
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This study presents a novel approach for fabricating ZIF-8 membranes supported on α-alumina hollow fibers through the introduction of a graphene oxide (GO) gutter layer and the application of zinc oxide (ZnO) Atomic Layer Deposition (ALD). The method successfully addressed key challenges, including excessive precursor penetration and membrane thickness. The introduction of the GO layer and subsequent ZnO ALD treatment significantly reduced membrane thickness to approximately 300 nm and eliminated delamination issues between the GO layer and the alumina support. The optimized membranes demonstrated enhanced propylene permeance, with values approximately three times higher than those of membranes without GO, and achieved higher separation factors, indicating minimal inter-crystalline defects. Notably, the GO layer influenced the microstructure, leading to an increase in permeance with rising temperatures. These findings highlight the potential of this strategy for developing high-performance ZIF-8 membranes for gas separation applications.
Full article
(This article belongs to the Special Issue Thin-Film Composite Membranes for Gas and Vapor Separation)
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Figure 1
Figure 1
<p>Cross-sectional SEM images of (<b>A</b>) ZIF-8 membranes on bare α-alumina hollow fiber supports using RTD, and (<b>B</b>) deep penetration of ZIF-8 into the finger-like pores of the α-alumina support.</p> Full article ">Figure 2
<p>(<b>A</b>) Photograph of GO solution and bare α-alumina hollow fibers before coating. (<b>B</b>–<b>F</b>) Cross-sectional SEM images of GO-coated α-alumina fibers with varying GO concentrations: (<b>B</b>) 0.5 mg/mL, (<b>C</b>) 1 mg/mL, (<b>D</b>) 5 mg/mL, (<b>E</b>) 10 mg/mL, and (<b>F</b>) 20 mg/mL.</p> Full article ">Figure 3
<p>(<b>A</b>) pXRD patterns of the ZIF-8 membrane on GO-layered α-alumina support, bare α-alumina hollow fiber, and simulated ZIF-8 pattern. Cross-sectional SEM images showing (<b>B</b>) bare α-alumina support, (<b>C</b>) GO-coated α-alumina support, and (<b>D</b>) as-synthesized GO@ZIF-8 layer, with the delaminated interface between the GO layer and α-alumina. (<b>E</b>–<b>G</b>) Corresponding top-view SEM images of (<b>E</b>) bare α-alumina, (<b>F</b>) GO-coated support, and (<b>G</b>) GO@ZIF-8 layer.</p> Full article ">Figure 4
<p>(<b>A</b>) GO layer surface before ALD treatment, showing surface wrinkles. (<b>B</b>) GO surface after 20-cycle ZnO ALD treatment. (<b>C</b>) EDX mapping of Zn showing uniform distribution on the GO surface after 20 ALD cycles. (<b>D</b>) GO surface after post-treatment with 2 mIm vapor. (<b>E</b>) EDX mapping of the nitrogen atom. The illustrations in each column were designed to facilitate understanding.</p> Full article ">Figure 5
<p>(<b>A</b>) Cross-sectional and (<b>B</b>) top-view SEM image of ZIF-8 membrane grown on 2 mIm vapor-treated GO-layered α-alumina support, and (<b>C</b>) corresponding pXRD patterns.</p> Full article ">Figure 6
<p>(<b>A</b>) Propane/propylene separation performance of ZIF-8 membranes on non-coated α-alumina (Case 1) and GO-coated α-alumina (Case 2). (<b>B</b>) Temperature dependence of propylene permeance and propylene/propane selectivity for the non-coated α-alumina (Case 1) and GO-coated α-alumina (Case 2).</p> Full article ">
<p>Cross-sectional SEM images of (<b>A</b>) ZIF-8 membranes on bare α-alumina hollow fiber supports using RTD, and (<b>B</b>) deep penetration of ZIF-8 into the finger-like pores of the α-alumina support.</p> Full article ">Figure 2
<p>(<b>A</b>) Photograph of GO solution and bare α-alumina hollow fibers before coating. (<b>B</b>–<b>F</b>) Cross-sectional SEM images of GO-coated α-alumina fibers with varying GO concentrations: (<b>B</b>) 0.5 mg/mL, (<b>C</b>) 1 mg/mL, (<b>D</b>) 5 mg/mL, (<b>E</b>) 10 mg/mL, and (<b>F</b>) 20 mg/mL.</p> Full article ">Figure 3
<p>(<b>A</b>) pXRD patterns of the ZIF-8 membrane on GO-layered α-alumina support, bare α-alumina hollow fiber, and simulated ZIF-8 pattern. Cross-sectional SEM images showing (<b>B</b>) bare α-alumina support, (<b>C</b>) GO-coated α-alumina support, and (<b>D</b>) as-synthesized GO@ZIF-8 layer, with the delaminated interface between the GO layer and α-alumina. (<b>E</b>–<b>G</b>) Corresponding top-view SEM images of (<b>E</b>) bare α-alumina, (<b>F</b>) GO-coated support, and (<b>G</b>) GO@ZIF-8 layer.</p> Full article ">Figure 4
<p>(<b>A</b>) GO layer surface before ALD treatment, showing surface wrinkles. (<b>B</b>) GO surface after 20-cycle ZnO ALD treatment. (<b>C</b>) EDX mapping of Zn showing uniform distribution on the GO surface after 20 ALD cycles. (<b>D</b>) GO surface after post-treatment with 2 mIm vapor. (<b>E</b>) EDX mapping of the nitrogen atom. The illustrations in each column were designed to facilitate understanding.</p> Full article ">Figure 5
<p>(<b>A</b>) Cross-sectional and (<b>B</b>) top-view SEM image of ZIF-8 membrane grown on 2 mIm vapor-treated GO-layered α-alumina support, and (<b>C</b>) corresponding pXRD patterns.</p> Full article ">Figure 6
<p>(<b>A</b>) Propane/propylene separation performance of ZIF-8 membranes on non-coated α-alumina (Case 1) and GO-coated α-alumina (Case 2). (<b>B</b>) Temperature dependence of propylene permeance and propylene/propane selectivity for the non-coated α-alumina (Case 1) and GO-coated α-alumina (Case 2).</p> Full article ">
Open AccessArticle
Electroformation of Giant Unilamellar Vesicles from Damp Films in Conditions Involving High Cholesterol Contents, Charged Lipids, and Saline Solutions
by
Ivan Mardešić, Zvonimir Boban and Marija Raguz
Membranes 2024, 14(10), 215; https://doi.org/10.3390/membranes14100215 - 12 Oct 2024
Abstract
Giant unilamellar vesicles (GUVs) are frequently used as membrane models in studies of membrane properties. They are most often produced using the electroformation method. However, there are a number of parameters that can influence the success of the procedure. Some of the most
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Giant unilamellar vesicles (GUVs) are frequently used as membrane models in studies of membrane properties. They are most often produced using the electroformation method. However, there are a number of parameters that can influence the success of the procedure. Some of the most common conditions that have been shown to have a negative effect on GUV electroformation are the presence of high cholesterol (Chol) concentrations, the use of mixtures containing charged lipids, and the solutions with an elevated ionic strength. High Chol concentrations are problematic for the traditional electroformation protocol as it involves the formation of a dry lipid film by complete evaporation of the organic solvent from the lipid mixture. During drying, anhydrous Chol crystals form. They are not involved in the formation of the lipid bilayer, resulting in a lower Chol concentration in the vesicle bilayer compared to the original lipid mixture. Motivated primarily by the issue of artifactual Chol demixing, we have modified the electroformation protocol by incorporating the techniques of rapid solvent exchange (RSE), ultrasonication, plasma cleaning, and spin-coating for reproducible production of GUVs from damp lipid films. Aside from decreasing Chol demixing, we have shown that the method can also be used to produce GUVs from lipid mixtures with charged lipids and in ionic solutions used as internal solutions. A high yield of GUVs was obtained for Chol/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) samples with mixing ratios ranging from 0 to 2.5. We also succeeded in preparing GUVs from mixtures containing up to 60 mol% of the charged lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS) and in NaCl solutions with low ionic strength (<25 mM).
Full article
(This article belongs to the Section Membrane Fabrication and Characterization)
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Figure 1
<p>Examples of Chol crystals formed during the dry film phase when using the traditional electroformation protocol. The observed crystal structures are in good agreement with those observed in the study of Park et al. [<a href="#B21-membranes-14-00215" class="html-bibr">21</a>] on the phases of Chol crystallization. The scale bar represents 50 µm.</p> Full article ">Figure 2
<p>The modified protocol is for electroformation of GUVs from a damp lipid film. (<b>a</b>) The RSE method is used to produce an MLV solution. The RSE method is used to produce an MLV solution. An organic solvent (blue) containing lipids (red) is mixed with an aqueous solution (tube 1). The organic solvent is removed by vortexing the solution under vacuum in order to form MLVs (tube 3). (<b>b</b>) The suspension of MLVs is sonicated to produce LUVs. (<b>c</b>) A plasma cleaner is used to hydrophilize the ITO electrode. (<b>d</b>) The LUV suspension is deposited onto a plasma-cleaned ITO-coated glass and spin-coated to obtain a damp lipid film. (<b>e</b>) The coated electrode is used to assemble the electroformation chamber and connected to a voltage source to enable the growth of GUVs.</p> Full article ">Figure 3
<p>The effect of sonication parameters on the size of produced LUVs. (<b>a</b>) The effect of sonication duration using different sonication amplitudes for MLVs produced from a mixture with a Chol/POPC ratio of 1.5. (<b>b</b>) The effect of sonication duration for different Chol/POPC mixing ratios at a sonication amplitude of 60%.</p> Full article ">Figure 4
<p>The effect of increasing the Chol content on the electroformation of GUVs. (<b>a</b>) Size of GUVs as a function of the different Chol mixing ratios. The points and bars represent mean values and standard errors. The mean values were calculated by averaging the mean diameters from three independent samples for each concentration. (<b>b</b>) Size distribution densities for different Chol contents. Each distribution density represents 300 vesicles (100 vesicles from each of the three samples). (<b>c</b>) Fluorescence microscopy images for each sample. The scale bar represents 50 µm.</p> Full article ">Figure 5
<p>Electroformation from damp lipid films using different concentrations of POPS. (<b>a</b>) GUV size as a function of POPS concentrations. The points and bars represent mean values and standard errors. Mean values were calculated by averaging the mean diameters of three independent samples for each concentration. (<b>b</b>) Size distribution densities of GUVs for different POPS concentrations. Each distribution density represents 300 vesicles (100 vesicles from each of the three samples). (<b>c</b>) Fluorescence microscopy images for each sample. The scale bar represents 50 µm.</p> Full article ">Figure 6
<p>Electroformation from damp lipid films using saline solutions for the Chol/POPC mixture with a fixed Chol concentration of 10 mol%. (<b>a</b>) Size distribution of GUVs for different salt concentrations. Each distribution density represents 300 vesicles (100 vesicles from each of the three samples). (<b>b</b>) Fluorescence microscopy images for each sample. The scale bar represents 50 µm.</p> Full article ">
<p>Examples of Chol crystals formed during the dry film phase when using the traditional electroformation protocol. The observed crystal structures are in good agreement with those observed in the study of Park et al. [<a href="#B21-membranes-14-00215" class="html-bibr">21</a>] on the phases of Chol crystallization. The scale bar represents 50 µm.</p> Full article ">Figure 2
<p>The modified protocol is for electroformation of GUVs from a damp lipid film. (<b>a</b>) The RSE method is used to produce an MLV solution. The RSE method is used to produce an MLV solution. An organic solvent (blue) containing lipids (red) is mixed with an aqueous solution (tube 1). The organic solvent is removed by vortexing the solution under vacuum in order to form MLVs (tube 3). (<b>b</b>) The suspension of MLVs is sonicated to produce LUVs. (<b>c</b>) A plasma cleaner is used to hydrophilize the ITO electrode. (<b>d</b>) The LUV suspension is deposited onto a plasma-cleaned ITO-coated glass and spin-coated to obtain a damp lipid film. (<b>e</b>) The coated electrode is used to assemble the electroformation chamber and connected to a voltage source to enable the growth of GUVs.</p> Full article ">Figure 3
<p>The effect of sonication parameters on the size of produced LUVs. (<b>a</b>) The effect of sonication duration using different sonication amplitudes for MLVs produced from a mixture with a Chol/POPC ratio of 1.5. (<b>b</b>) The effect of sonication duration for different Chol/POPC mixing ratios at a sonication amplitude of 60%.</p> Full article ">Figure 4
<p>The effect of increasing the Chol content on the electroformation of GUVs. (<b>a</b>) Size of GUVs as a function of the different Chol mixing ratios. The points and bars represent mean values and standard errors. The mean values were calculated by averaging the mean diameters from three independent samples for each concentration. (<b>b</b>) Size distribution densities for different Chol contents. Each distribution density represents 300 vesicles (100 vesicles from each of the three samples). (<b>c</b>) Fluorescence microscopy images for each sample. The scale bar represents 50 µm.</p> Full article ">Figure 5
<p>Electroformation from damp lipid films using different concentrations of POPS. (<b>a</b>) GUV size as a function of POPS concentrations. The points and bars represent mean values and standard errors. Mean values were calculated by averaging the mean diameters of three independent samples for each concentration. (<b>b</b>) Size distribution densities of GUVs for different POPS concentrations. Each distribution density represents 300 vesicles (100 vesicles from each of the three samples). (<b>c</b>) Fluorescence microscopy images for each sample. The scale bar represents 50 µm.</p> Full article ">Figure 6
<p>Electroformation from damp lipid films using saline solutions for the Chol/POPC mixture with a fixed Chol concentration of 10 mol%. (<b>a</b>) Size distribution of GUVs for different salt concentrations. Each distribution density represents 300 vesicles (100 vesicles from each of the three samples). (<b>b</b>) Fluorescence microscopy images for each sample. The scale bar represents 50 µm.</p> Full article ">
Open AccessArticle
Typical Heterotrophic and Autotrophic Nitrogen Removal Process Coupled with Membrane Bioreactor: Comparison of Fouling Behavior and Characterization
by
Qiushan Liu, Tong Zhou, Yuru Liu, Wenjun Wu, Yufei Wang, Guohan Liu, Na Wei, Guangshuo Yin and Jin Guo
Membranes 2024, 14(10), 214; https://doi.org/10.3390/membranes14100214 - 7 Oct 2024
Abstract
There is limited research on the relationship between membrane fouling and microbial metabolites in the nitrogen removal process coupled with membrane bioreactors (MBRs). In this study, we compared anoxic-oxic (AO) and partial nitritation–anammox (PNA), which were selected as representative heterotrophic and autotrophic biological
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There is limited research on the relationship between membrane fouling and microbial metabolites in the nitrogen removal process coupled with membrane bioreactors (MBRs). In this study, we compared anoxic-oxic (AO) and partial nitritation–anammox (PNA), which were selected as representative heterotrophic and autotrophic biological nitrogen removal–coupled MBR processes for their fouling behavior. At the same nitrogen loading rate of 100 mg/L and mixed liquor suspended solids (MLSS) concentration of 4000 mg/L, PNA-MBR exhibited more severe membrane fouling compared to AO-MBR, as evidenced by monitoring changes in transmembrane pressure (TMP). In the autotrophic nitrogen removal process, without added organic carbon, the supernatant of PNA-MBR had higher concentrations of protein, polysaccharides, and low-molecular-weight humic substances, leading to a rapid flux decline. Extracellular polymeric substances (EPS) extracted from suspended sludge and cake sludge in PNA-MBR also contributed to more severe membrane fouling than in AO-MBR. The EPS subfractions of PNA-MBR exhibited looser secondary structures in protein and stronger surface hydrophobicity, particularly in the cake sludge, which contained higher contents of humic substances with lower molecular weights. The higher abundances of Candidatus Brocadia and Chloroflexi in PNA-MBR could lead to the production of more hydrophobic organics and humic substances. Hydrophobic metabolism products as well as anammox bacteria were deposited on the hydrophobic membrane surface and formed serious fouling. Therefore, hydrophilic membrane modification is more urgently needed to mitigate membrane fouling when running PNA–MBR than AO–MBR.
Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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<p>The concentration of NH<sub>4</sub><sup>+</sup>−N, NO<sub>2</sub><sup>−</sup>−N, and NO<sub>3</sub><sup>−</sup> − N in the influent and effluent of (<b>a</b>) AO−MBR and (<b>b</b>) PNA−MBR and the temporal variation in TMP during the operation of the two reactors (<b>c</b>).</p> Full article ">Figure 2
<p>Fouling behavior and characterization of AO/PNA supernatant and effluent of AO/PNA−MBR. (<b>a</b>) Normalized flux transformation; (<b>b</b>) membrane resistance calculation; (<b>c</b>) protein and polysaccharide concentration; (<b>d</b>) total organic carbon (TOC) and UV<sub>254</sub>; (<b>e</b>) FTIR analysis; (<b>f</b>) MW distribution.</p> Full article ">Figure 3
<p>Normalized flux transformation. (<b>a</b>,<b>b</b>) EPS extracted from the suspended sludge; (<b>c</b>,<b>d</b>) EPS extracted from the cake sludge.</p> Full article ">Figure 4
<p>Contents and EEM analyses of SMP, LB-EPS, and TB-EPS in suspended sludge (<b>a</b>,<b>c</b>) and the cake sludge on day 44 (<b>b</b>,<b>d</b>) in the AO-MBR and PNA-MBR.</p> Full article ">Figure 5
<p>Taxonomic distribution of the microbial community in the sludge of the AO-MBR and PNA-MBR in the operational phase (0 d and 44 d) of the suspended sludge and the cake sludge at phylum (<b>a</b>) and genus (<b>b</b>) level by 16S rRNA sequencing.</p> Full article ">
<p>The concentration of NH<sub>4</sub><sup>+</sup>−N, NO<sub>2</sub><sup>−</sup>−N, and NO<sub>3</sub><sup>−</sup> − N in the influent and effluent of (<b>a</b>) AO−MBR and (<b>b</b>) PNA−MBR and the temporal variation in TMP during the operation of the two reactors (<b>c</b>).</p> Full article ">Figure 2
<p>Fouling behavior and characterization of AO/PNA supernatant and effluent of AO/PNA−MBR. (<b>a</b>) Normalized flux transformation; (<b>b</b>) membrane resistance calculation; (<b>c</b>) protein and polysaccharide concentration; (<b>d</b>) total organic carbon (TOC) and UV<sub>254</sub>; (<b>e</b>) FTIR analysis; (<b>f</b>) MW distribution.</p> Full article ">Figure 3
<p>Normalized flux transformation. (<b>a</b>,<b>b</b>) EPS extracted from the suspended sludge; (<b>c</b>,<b>d</b>) EPS extracted from the cake sludge.</p> Full article ">Figure 4
<p>Contents and EEM analyses of SMP, LB-EPS, and TB-EPS in suspended sludge (<b>a</b>,<b>c</b>) and the cake sludge on day 44 (<b>b</b>,<b>d</b>) in the AO-MBR and PNA-MBR.</p> Full article ">Figure 5
<p>Taxonomic distribution of the microbial community in the sludge of the AO-MBR and PNA-MBR in the operational phase (0 d and 44 d) of the suspended sludge and the cake sludge at phylum (<b>a</b>) and genus (<b>b</b>) level by 16S rRNA sequencing.</p> Full article ">
Open AccessArticle
The Efficiency of Polyester-Polysulfone Membranes, Coated with Crosslinked PVA Layers, in the Water Desalination by Pervaporation
by
Izabela Gortat, Jerzy J. Chruściel, Joanna Marszałek, Renata Żyłła and Paweł Wawrzyniak
Membranes 2024, 14(10), 213; https://doi.org/10.3390/membranes14100213 - 7 Oct 2024
Abstract
Composite polymer membranes were obtained using the so-called dry phase inversion and were used for desalination of diluted saline water solutions by pervaporation (PV) method. The tests used a two-layer backing, porous, ultrafiltration commercial membrane (PS20), which consisted of a supporting polyester layer
[...] Read more.
Composite polymer membranes were obtained using the so-called dry phase inversion and were used for desalination of diluted saline water solutions by pervaporation (PV) method. The tests used a two-layer backing, porous, ultrafiltration commercial membrane (PS20), which consisted of a supporting polyester layer and an active polysulfone layer. The active layer of PV membranes was obtained in an aqueous environment, in the presence of a surfactant, by cross-linking a 5 wt.% aqueous solution of polyvinyl alcohol (PVA)—using various amounts of cross-linking substances: 50 wt.% aqueous solutions of glutaraldehyde (GA) or citric acid (CA) or a 40 wt.% aqueous solution of glyoxal. An ethylene glycol oligomer (PEG 200) was also used to prepare active layers on PV membranes. Witch its help a chemically cross-linked hydrogel with PVA and cross-linking reagents (CA or GA) was formed and used as an active layer. The manufactured PV membranes (PVA/PSf/PES) were used in the desalination of water with a salinity of 35‰, which corresponds to the average salinity of oceans. The pervaporation method was used to examine the efficiency (productivity and selectivity) of the desalination process. The PV was carried at a temperature of 60 °C and a feed flow rate of 60 dm3/h while the membrane area was 0.005 m2. The following characteristic parameters of the membranes were determined: thickness, hydrophilicity (based on contact angle measurements), density, degree of swelling and cross-linking density and compared with the analogous properties of the initial PS20 backing membrane. The physical microstructure of the cross-section of the membranes was analyzed using scanning electron microscopy (SEM) method.
Full article
(This article belongs to the Special Issue Membrane Processes in a Circular Economy: Opportunities and Challenges)
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<p>A structural formula of tannic acid.</p> Full article ">Figure 2
<p>Diagram of laboratory apparatus for water desalination using the PV process (M—pressure gauge, T—thermometer), arrows show the direction of feed and permeate flow.</p> Full article ">Figure 3
<p>Reaction scheme of the crosslinking reaction of polyvinyl alcohol (PVA) with glutaraldehyde (GA).</p> Full article ">Figure 4
<p>Reaction scheme of the crosslinking reaction of polyvinyl alcohol (PVA) with glyoxal solution.</p> Full article ">Figure 5
<p>Reaction scheme of the crosslinking reaction of polyvinyl alcohol (PVA) with citric acid (CA)—under assumption that only 2 COOH groups of CA reacted with PVA.</p> Full article ">Figure 6
<p>SEM images of the surfaces of selected PVA/PSf/PES membranes: (<b>A</b>) M56; (<b>B</b>) M67; (<b>C</b>) M75; (<b>D</b>) M86; (<b>E</b>) PERVAP 4510.</p> Full article ">Figure 7
<p>Relationship between the swelling degree (<span class="html-italic">S</span>) and the contact angle (δ) for the prepared PVA/PSf/PES membranes.</p> Full article ">Figure 8
<p>SEM image of the surface of the active layer of the M61 membrane containing PEG 200.</p> Full article ">Figure 9
<p>Summary of permeate flux (<span class="html-italic">J<sub>p</sub></span>) and retention degree (<span class="html-italic">R</span>) values after the water desalination process by PV method (<span class="html-italic">T</span> = 60 °C, <span class="html-italic">Q<sub>f</sub></span> = 60 dm<sup>3</sup>/h) for membranes crosslinked with selected crosslinking agents.</p> Full article ">Figure 10
<p>The summary of the influence of the type of the surfactant on the efficiency (<span class="html-italic">J<sub>p</sub></span>) and selectivity (<span class="html-italic">R</span>) of selected PVA/PSf/PES membranes for the water desalination process by PV (<span class="html-italic">T</span> = 60 °C, <span class="html-italic">Q<sub>f</sub></span> = 60 dm<sup>3</sup>/h).</p> Full article ">Figure 11
<p>The relationship between cross-linking density (<span class="html-italic">υ</span>) and permeate flux of developed membranes (<span class="html-italic">J<sub>p</sub></span>). The bars on the graph indicate the cross-linking density—left axis; Dots indicate the permeate stream—right axis.</p> Full article ">
<p>A structural formula of tannic acid.</p> Full article ">Figure 2
<p>Diagram of laboratory apparatus for water desalination using the PV process (M—pressure gauge, T—thermometer), arrows show the direction of feed and permeate flow.</p> Full article ">Figure 3
<p>Reaction scheme of the crosslinking reaction of polyvinyl alcohol (PVA) with glutaraldehyde (GA).</p> Full article ">Figure 4
<p>Reaction scheme of the crosslinking reaction of polyvinyl alcohol (PVA) with glyoxal solution.</p> Full article ">Figure 5
<p>Reaction scheme of the crosslinking reaction of polyvinyl alcohol (PVA) with citric acid (CA)—under assumption that only 2 COOH groups of CA reacted with PVA.</p> Full article ">Figure 6
<p>SEM images of the surfaces of selected PVA/PSf/PES membranes: (<b>A</b>) M56; (<b>B</b>) M67; (<b>C</b>) M75; (<b>D</b>) M86; (<b>E</b>) PERVAP 4510.</p> Full article ">Figure 7
<p>Relationship between the swelling degree (<span class="html-italic">S</span>) and the contact angle (δ) for the prepared PVA/PSf/PES membranes.</p> Full article ">Figure 8
<p>SEM image of the surface of the active layer of the M61 membrane containing PEG 200.</p> Full article ">Figure 9
<p>Summary of permeate flux (<span class="html-italic">J<sub>p</sub></span>) and retention degree (<span class="html-italic">R</span>) values after the water desalination process by PV method (<span class="html-italic">T</span> = 60 °C, <span class="html-italic">Q<sub>f</sub></span> = 60 dm<sup>3</sup>/h) for membranes crosslinked with selected crosslinking agents.</p> Full article ">Figure 10
<p>The summary of the influence of the type of the surfactant on the efficiency (<span class="html-italic">J<sub>p</sub></span>) and selectivity (<span class="html-italic">R</span>) of selected PVA/PSf/PES membranes for the water desalination process by PV (<span class="html-italic">T</span> = 60 °C, <span class="html-italic">Q<sub>f</sub></span> = 60 dm<sup>3</sup>/h).</p> Full article ">Figure 11
<p>The relationship between cross-linking density (<span class="html-italic">υ</span>) and permeate flux of developed membranes (<span class="html-italic">J<sub>p</sub></span>). The bars on the graph indicate the cross-linking density—left axis; Dots indicate the permeate stream—right axis.</p> Full article ">
Open AccessArticle
Landfill Leachate and Coagulants Addition Effects on Membrane Bioreactor Mixed Liquor: Filterability, Fouling, and Pollutant Removal
by
Rodrigo Almeria Ragio, Ana Carolina Santana and Eduardo Lucas Subtil
Membranes 2024, 14(10), 212; https://doi.org/10.3390/membranes14100212 - 2 Oct 2024
Abstract
Urban wastewater (UWW) and landfill leachate (LL) co-treatment using membrane bioreactors (MBRs) is a valuable method for managing LL in cities. Coagulants can enhance the filterability of mixed liquor (ML), but the assessment of fouling is still needed. This research aimed to investigate
[...] Read more.
Urban wastewater (UWW) and landfill leachate (LL) co-treatment using membrane bioreactors (MBRs) is a valuable method for managing LL in cities. Coagulants can enhance the filterability of mixed liquor (ML), but the assessment of fouling is still needed. This research aimed to investigate the effects of co-treating synthetic wastewater (SWW) and real LL on an MBR, as well as the impact of adding poly-aluminum chloride (PACl) and Tanfloc SG. Cell-ultrafiltration experiments were conducted with four different feeds: synthetic wastewater, co-treatment with LL (20% v/v), and co-treatment with the addition of 30 mg L−1 coagulants (either PACl or Tanfloc). Co-treatment aggravated flux loss and reduced the recovery rate; however, Tanfloc and PACl improved recovery after cleaning (by 11% and 9%, respectively). Co-treatment also increased cake and irrecoverable/irremovable inorganic resistances, though coagulants reduced the latter, despite a lower fit of the Hermia models during the first hour of filtration. Co-treatment reduced the removal efficiencies of almost all pollutants analyzed, with the most significant impacts observed on the organic fraction. Coagulants, particularly Tanfloc, enhanced overall performance by improving flux recovery and reducing irreversibility, thus benefiting membrane lifespan. In conclusion, Tanfloc addition yielded the best results in terms of filterability and pollutant removal.
Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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<p>Cell-ultrafiltration experiment design.</p> Full article ">Figure 2
<p>Co-treatment effect on SMP (<b>A</b>) and eEPS (<b>B</b>) concentrations in aerobic biomass.</p> Full article ">Figure 3
<p>Co-treatment effect on ML particle size distribution.</p> Full article ">Figure 4
<p>Co-treatment effect on flux loss and recovery by cleaning mechanisms.</p> Full article ">Figure 5
<p>Co-treatment effect on R<sub>f</sub> fractions.</p> Full article ">Figure 6
<p>Cotreatment effect on pollutants removal efficiency.</p> Full article ">Figure 7
<p>Coagulants effect on SMP (<b>A</b>) and eEPS (<b>B</b>) concentrations in aerobic biomass.</p> Full article ">Figure 8
<p>Coagulants effect on ML particle size distribution.</p> Full article ">Figure 9
<p>Coagulants effect on flux loss and recovery by cleaning mechanisms.</p> Full article ">Figure 10
<p>Coagulants effect on R<sub>f</sub> fractions.</p> Full article ">Figure 11
<p>Coagulants effect on pollutants removal efficiency.</p> Full article ">
<p>Cell-ultrafiltration experiment design.</p> Full article ">Figure 2
<p>Co-treatment effect on SMP (<b>A</b>) and eEPS (<b>B</b>) concentrations in aerobic biomass.</p> Full article ">Figure 3
<p>Co-treatment effect on ML particle size distribution.</p> Full article ">Figure 4
<p>Co-treatment effect on flux loss and recovery by cleaning mechanisms.</p> Full article ">Figure 5
<p>Co-treatment effect on R<sub>f</sub> fractions.</p> Full article ">Figure 6
<p>Cotreatment effect on pollutants removal efficiency.</p> Full article ">Figure 7
<p>Coagulants effect on SMP (<b>A</b>) and eEPS (<b>B</b>) concentrations in aerobic biomass.</p> Full article ">Figure 8
<p>Coagulants effect on ML particle size distribution.</p> Full article ">Figure 9
<p>Coagulants effect on flux loss and recovery by cleaning mechanisms.</p> Full article ">Figure 10
<p>Coagulants effect on R<sub>f</sub> fractions.</p> Full article ">Figure 11
<p>Coagulants effect on pollutants removal efficiency.</p> Full article ">
Open AccessArticle
Novel, Fluorine-Free Membranes Based on Sulfonated Polyvinyl Alcohol and Poly(ether-block-amide) with Sulfonated Montmorillonite Nanofiller for PEMFC Applications
by
Manhal H. Ibrahim Al-Mashhadani, Gábor Pál Szijjártó, Zoltán Sebestyén, Zoltán Károly, Judith Mihály and András Tompos
Membranes 2024, 14(10), 211; https://doi.org/10.3390/membranes14100211 - 1 Oct 2024
Abstract
Novel blend membranes containing S-PVA and PEBAX 1657 with a blend ratio of 8:2 (referred to as SPP) were prepared using a solution-casting technique. In the manufacturing process, sulfonated montmorillonite (S-MMT) in ratios of 0%, 3%, 5%, and 7% was used as a
[...] Read more.
Novel blend membranes containing S-PVA and PEBAX 1657 with a blend ratio of 8:2 (referred to as SPP) were prepared using a solution-casting technique. In the manufacturing process, sulfonated montmorillonite (S-MMT) in ratios of 0%, 3%, 5%, and 7% was used as a filler. The crystallinity of composite membranes has been investigated by X-ray diffraction (XRD), while the interaction between the components was evaluated using Fourier-transform infrared spectroscopy (FT-IR). With increasing filler content, good compatibility between the components due to hydrogen bonds was established, which ultimately resulted in improved tensile strength and chemical stability. In addition, due to the sulfonated moieties of S-MMT, the highest ion exchange capacity (0.46 meq/g) and water uptake (51.61%) can be achieved at the highest filler content with an acceptable swelling degree of 22.65%. The composite membrane with 7% S-MMT appears to be suitable for application in proton exchange membrane fuel cells (PEMFCs). Amongst the membranes studied, this membrane achieved the highest current density and power density in fuel cell tests, which were 149.5 mA/cm2 and 49.51 mW/cm2. Our fluorine-free composite membranes can become a promising new membrane family in PEMFC applications, offering an alternative to Nafion membranes.
Full article
(This article belongs to the Special Issue Recent Advances in Fluorine-Free Membranes)
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<p>Manufacturing procedure of blend membranes with different S-MMT content.</p> Full article ">Figure 2
<p>Water uptake and swelling ratio of SPP blend membranes and recast Nafion.</p> Full article ">Figure 3
<p>Ion exchange capacity for SPP blend membranes and recast Nafion.</p> Full article ">Figure 4
<p>(<b>A</b>): (<b>a</b>) Thermogravimetric (TG) and (<b>b</b>) derivate thermogravimetric (DTG) curves of S-PVA, PEBAX, and S-MMT; (<b>B</b>): (<b>a</b>) TG curves of the SPP blends membranes and (<b>b</b>) DTG curve and evolution profiles of some characteristic mass spectrometric ions of the SPP 7% S-MMT sample, <span class="html-italic">m</span>/<span class="html-italic">z</span>: 18 (water), <span class="html-italic">m</span>/<span class="html-italic">z</span>: 43 and 58 (acetone), <span class="html-italic">m</span>/<span class="html-italic">z</span>: 44 (carbon dioxide), <span class="html-italic">m</span>/<span class="html-italic">z</span>: 48 and 64 (sulfur dioxide).</p> Full article ">Figure 5
<p>In-plane and cross-sectional SEM images (<b>I</b> and <b>II</b>) for blend membranes ((<b>A</b>–<b>D</b>) refer to SPP 0% S-MMT, SPP 3% S-MMT, SPP 5% S-MMT, and SPP 7% S-MMT, respectively).</p> Full article ">Figure 6
<p>FTIR spectra of (<b>A</b>) SPP blend membranes and (<b>B</b>) the different constituents, such as parent and sulfonated montmorillonite (MMT and S-MMT), PVA, and S-PVA, as well as the pure PEBAX 1657.</p> Full article ">Figure 7
<p>X-ray diffraction patterns of SPP blend membranes.</p> Full article ">Figure 8
<p>Mechanical stability for SPP blend membranes.</p> Full article ">Figure 9
<p>Chemical stability by Fenton’s test for SPP blend membranes and recast Nafion.</p> Full article ">Figure 10
<p>Polarization curves and power density curves for SPP blend membranes. Solid and dashed lines correspond to voltage and power density.</p> Full article ">
<p>Manufacturing procedure of blend membranes with different S-MMT content.</p> Full article ">Figure 2
<p>Water uptake and swelling ratio of SPP blend membranes and recast Nafion.</p> Full article ">Figure 3
<p>Ion exchange capacity for SPP blend membranes and recast Nafion.</p> Full article ">Figure 4
<p>(<b>A</b>): (<b>a</b>) Thermogravimetric (TG) and (<b>b</b>) derivate thermogravimetric (DTG) curves of S-PVA, PEBAX, and S-MMT; (<b>B</b>): (<b>a</b>) TG curves of the SPP blends membranes and (<b>b</b>) DTG curve and evolution profiles of some characteristic mass spectrometric ions of the SPP 7% S-MMT sample, <span class="html-italic">m</span>/<span class="html-italic">z</span>: 18 (water), <span class="html-italic">m</span>/<span class="html-italic">z</span>: 43 and 58 (acetone), <span class="html-italic">m</span>/<span class="html-italic">z</span>: 44 (carbon dioxide), <span class="html-italic">m</span>/<span class="html-italic">z</span>: 48 and 64 (sulfur dioxide).</p> Full article ">Figure 5
<p>In-plane and cross-sectional SEM images (<b>I</b> and <b>II</b>) for blend membranes ((<b>A</b>–<b>D</b>) refer to SPP 0% S-MMT, SPP 3% S-MMT, SPP 5% S-MMT, and SPP 7% S-MMT, respectively).</p> Full article ">Figure 6
<p>FTIR spectra of (<b>A</b>) SPP blend membranes and (<b>B</b>) the different constituents, such as parent and sulfonated montmorillonite (MMT and S-MMT), PVA, and S-PVA, as well as the pure PEBAX 1657.</p> Full article ">Figure 7
<p>X-ray diffraction patterns of SPP blend membranes.</p> Full article ">Figure 8
<p>Mechanical stability for SPP blend membranes.</p> Full article ">Figure 9
<p>Chemical stability by Fenton’s test for SPP blend membranes and recast Nafion.</p> Full article ">Figure 10
<p>Polarization curves and power density curves for SPP blend membranes. Solid and dashed lines correspond to voltage and power density.</p> Full article ">
Open AccessArticle
Application of Polymeric Tubular Ultrafiltration Membranes for Separation of Car Wash Wastewater
by
Piotr Woźniak and Marek Gryta
Membranes 2024, 14(10), 210; https://doi.org/10.3390/membranes14100210 - 28 Sep 2024
Abstract
The commercial ultrafiltration tubular polyvinylidene fluoride (PVDF) (100 and 200 kDa) and polyethersulfone (PES) (4 kDa) membranes were applied for filtration of car wash wastewater. Intensive fouling was noticed, which caused an over 50% flux reduction during 3–5 h of the filtration process.
[...] Read more.
The commercial ultrafiltration tubular polyvinylidene fluoride (PVDF) (100 and 200 kDa) and polyethersulfone (PES) (4 kDa) membranes were applied for filtration of car wash wastewater. Intensive fouling was noticed, which caused an over 50% flux reduction during 3–5 h of the filtration process. This phenomenon was reduced by washing the membranes with an alkaline cleaning agent (pH = 11.5), which is used in car washes to remove insects. The filtration/membrane washing cycle was repeated many times to achieve stable operation of the membrane modules. It has been found that cyclic repeated washing did not deteriorate the performance of the membranes. Despite frequent cleaning of the membranes (every 5–7 h), irreversible fouling occurred, resulting in a 20% reduction in the initial permeate flux. However, the formation of a filter cake definitely improved the separation degree and, for the 200 kDa membranes, separation of the wastewater components was obtained as it was for the 4 kDa membranes, while, at the same time, the permeate flux was 5 times higher.
Full article
(This article belongs to the Special Issue Membrane Technologies for Water Purification)
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<p>UF experimental set-up. 1—feed tank, 2—pump, 3—tubular membrane, 4—permeate collector, 5—measurement cylinder, 6—valve, and P—manometer.</p> Full article ">Figure 2
<p>SEM images of tubular UF membranes. (<b>a</b>) ESP04 membrane (<b>top</b>) formed on the porous support layer (<b>down</b>) and (<b>b</b>) FP100 membrane cross-section; support layer was removed.</p> Full article ">Figure 3
<p>SEM images of membrane surfaces: (<b>a</b>) FP100, (<b>b</b>) FP200, and (<b>c</b>) ESP04.</p> Full article ">Figure 4
<p>Changes in the initial permeate flux during filtration of deionised water. W—membranes washed with 0.5% Insect solution (30 min). TMP = 0.1 MPa.</p> Full article ">Figure 5
<p>Changes in the permeate flux and turbidity of the feed and permeate during separation of the Turbo Foam + Hydrowax mixture. Membranes: (<b>a</b>,<b>b</b>) FP100 and (<b>c</b>,<b>d</b>) FP200. Water and water W—pure water flux (DI water as a feed) measured after the UF process and after washing the membrane with 0.5% Insect solution (30 min), respectively. Point R—rinse time 2 h.</p> Full article ">Figure 6
<p>SEM images of the FP100 and FP200 membrane surfaces. Deposits formed during separation of the Turbo Foam + Hydrowax mixture: (<b>a</b>) FP100 and (<b>c</b>) FP200. Deposits removed by washing with Insect solution: (<b>b</b>) FP100 and (<b>d</b>) FP200.</p> Full article ">Figure 7
<p>Changes in the rejection rate of COD and surfactants in samples taken at the beginning (5 h) and end (95 or 120 h) of the synthetic wastewater separation period. Membranes: (<b>a</b>) FP100 and (<b>b</b>) FP200.</p> Full article ">Figure 8
<p>Separation of real wastewater (WW1) using FP100 membrane. Series: S1, S3—VCR = 1, S2–VCR = 2, and S4—VCR = 4. W1, W2—membrane rinsed with 0.5% Insect solution (30 min).</p> Full article ">Figure 9
<p>Course of WW2 wastewater separation by FP100 membranes: (<b>a</b>) flux and (<b>b</b>) feed and permeate turbidity. W1, W2, W3—membrane washed using 0.5% Insect solution (30 min). The last two series—retentates from previous runs (VCR = 2) used as a feed.</p> Full article ">Figure 10
<p>SEM images of FP100 membrane after UF wastewater WW2 and 30 min washing with 0.5% Insect solution (<a href="#membranes-14-00210-f009" class="html-fig">Figure 9</a>, W1). Circle–area with pores.</p> Full article ">Figure 11
<p>Variation in separation rates of FP100 membranes (<b>a</b>) WW1 and (<b>b</b>) WW2. F—filtration of the first batch of wastewater by pristine membranes. R—filtration of retentates (VCR = 4) in the last batch (13 h) presented in <a href="#membranes-14-00210-f008" class="html-fig">Figure 8</a> and 29 h in <a href="#membranes-14-00210-f009" class="html-fig">Figure 9</a>a.</p> Full article ">Figure 12
<p>WW2 wastewater separation course using FP200 membranes. (<b>a</b>,<b>b</b>) Results obtained during 2x concentration of wastewater (VCR = 2) and (<b>c</b>,<b>d</b>)—2x concentration of retentates obtained (VCR = 4).</p> Full article ">Figure 13
<p>Changes in the permeate flux (<b>a</b>) and turbidity (<b>b</b>) during separation WW3 wastewater by ESP04 membrane. R—membrane rinsed with the 0.25% sodium disulfite solution for 30 min.</p> Full article ">Figure 14
<p>Change in retention rate of wastewater components (<b>a</b>) WW2 (FP200) and (<b>b</b>) WW3 (ESP04). F—permeate sample taken after the first 2 h of wastewater filtration. R—permeate sample taken at the end of the presented studies (FP200—<a href="#membranes-14-00210-f012" class="html-fig">Figure 12</a>c, ESP04—<a href="#membranes-14-00210-f013" class="html-fig">Figure 13</a>a).</p> Full article ">Figure 15
<p>Rejection calculated to the values obtained for the pre-filtered feed (<a href="#membranes-14-00210-t002" class="html-table">Table 2</a>, —F).</p> Full article ">Figure 16
<p>SEM images of studied tubular membrane surfaces after wastewater separation: (<b>a</b>) FP100 —WW1, (<b>c</b>) FP100—WW2, (<b>e</b>) FP200—WW2, and (<b>g</b>) ESP04—WW3; and after fouled membrane washing with Insect solution: (<b>b</b>) FP100—WW1, (<b>d</b>) FP100—WW2, (<b>f</b>) FP200—WW2, and (<b>h</b>) ESP04—WW3.</p> Full article ">Figure A1
<p>Dextran (0.5 g/L) rejection by studied pristine membranes pre-washed with the 0.5% Insect solution. TMP = 0.1 MPa.</p> Full article ">Figure A2
<p>Changes in dextran separation FP100 (<b>a</b>) and FP200 (<b>b</b>) membranes. UF—membrane washed after UF process (30 min); washed—cleaning time 120 min.</p> Full article ">
<p>UF experimental set-up. 1—feed tank, 2—pump, 3—tubular membrane, 4—permeate collector, 5—measurement cylinder, 6—valve, and P—manometer.</p> Full article ">Figure 2
<p>SEM images of tubular UF membranes. (<b>a</b>) ESP04 membrane (<b>top</b>) formed on the porous support layer (<b>down</b>) and (<b>b</b>) FP100 membrane cross-section; support layer was removed.</p> Full article ">Figure 3
<p>SEM images of membrane surfaces: (<b>a</b>) FP100, (<b>b</b>) FP200, and (<b>c</b>) ESP04.</p> Full article ">Figure 4
<p>Changes in the initial permeate flux during filtration of deionised water. W—membranes washed with 0.5% Insect solution (30 min). TMP = 0.1 MPa.</p> Full article ">Figure 5
<p>Changes in the permeate flux and turbidity of the feed and permeate during separation of the Turbo Foam + Hydrowax mixture. Membranes: (<b>a</b>,<b>b</b>) FP100 and (<b>c</b>,<b>d</b>) FP200. Water and water W—pure water flux (DI water as a feed) measured after the UF process and after washing the membrane with 0.5% Insect solution (30 min), respectively. Point R—rinse time 2 h.</p> Full article ">Figure 6
<p>SEM images of the FP100 and FP200 membrane surfaces. Deposits formed during separation of the Turbo Foam + Hydrowax mixture: (<b>a</b>) FP100 and (<b>c</b>) FP200. Deposits removed by washing with Insect solution: (<b>b</b>) FP100 and (<b>d</b>) FP200.</p> Full article ">Figure 7
<p>Changes in the rejection rate of COD and surfactants in samples taken at the beginning (5 h) and end (95 or 120 h) of the synthetic wastewater separation period. Membranes: (<b>a</b>) FP100 and (<b>b</b>) FP200.</p> Full article ">Figure 8
<p>Separation of real wastewater (WW1) using FP100 membrane. Series: S1, S3—VCR = 1, S2–VCR = 2, and S4—VCR = 4. W1, W2—membrane rinsed with 0.5% Insect solution (30 min).</p> Full article ">Figure 9
<p>Course of WW2 wastewater separation by FP100 membranes: (<b>a</b>) flux and (<b>b</b>) feed and permeate turbidity. W1, W2, W3—membrane washed using 0.5% Insect solution (30 min). The last two series—retentates from previous runs (VCR = 2) used as a feed.</p> Full article ">Figure 10
<p>SEM images of FP100 membrane after UF wastewater WW2 and 30 min washing with 0.5% Insect solution (<a href="#membranes-14-00210-f009" class="html-fig">Figure 9</a>, W1). Circle–area with pores.</p> Full article ">Figure 11
<p>Variation in separation rates of FP100 membranes (<b>a</b>) WW1 and (<b>b</b>) WW2. F—filtration of the first batch of wastewater by pristine membranes. R—filtration of retentates (VCR = 4) in the last batch (13 h) presented in <a href="#membranes-14-00210-f008" class="html-fig">Figure 8</a> and 29 h in <a href="#membranes-14-00210-f009" class="html-fig">Figure 9</a>a.</p> Full article ">Figure 12
<p>WW2 wastewater separation course using FP200 membranes. (<b>a</b>,<b>b</b>) Results obtained during 2x concentration of wastewater (VCR = 2) and (<b>c</b>,<b>d</b>)—2x concentration of retentates obtained (VCR = 4).</p> Full article ">Figure 13
<p>Changes in the permeate flux (<b>a</b>) and turbidity (<b>b</b>) during separation WW3 wastewater by ESP04 membrane. R—membrane rinsed with the 0.25% sodium disulfite solution for 30 min.</p> Full article ">Figure 14
<p>Change in retention rate of wastewater components (<b>a</b>) WW2 (FP200) and (<b>b</b>) WW3 (ESP04). F—permeate sample taken after the first 2 h of wastewater filtration. R—permeate sample taken at the end of the presented studies (FP200—<a href="#membranes-14-00210-f012" class="html-fig">Figure 12</a>c, ESP04—<a href="#membranes-14-00210-f013" class="html-fig">Figure 13</a>a).</p> Full article ">Figure 15
<p>Rejection calculated to the values obtained for the pre-filtered feed (<a href="#membranes-14-00210-t002" class="html-table">Table 2</a>, —F).</p> Full article ">Figure 16
<p>SEM images of studied tubular membrane surfaces after wastewater separation: (<b>a</b>) FP100 —WW1, (<b>c</b>) FP100—WW2, (<b>e</b>) FP200—WW2, and (<b>g</b>) ESP04—WW3; and after fouled membrane washing with Insect solution: (<b>b</b>) FP100—WW1, (<b>d</b>) FP100—WW2, (<b>f</b>) FP200—WW2, and (<b>h</b>) ESP04—WW3.</p> Full article ">Figure A1
<p>Dextran (0.5 g/L) rejection by studied pristine membranes pre-washed with the 0.5% Insect solution. TMP = 0.1 MPa.</p> Full article ">Figure A2
<p>Changes in dextran separation FP100 (<b>a</b>) and FP200 (<b>b</b>) membranes. UF—membrane washed after UF process (30 min); washed—cleaning time 120 min.</p> Full article ">
Open AccessReview
Innovative Trends in Modified Membranes: A Mini Review of Applications and Challenges in the Food Sector
by
Nicole Novelli do Nascimento, Carolina Moser Paraíso, Luiza C. A. Molina, Yuliya S. Dzyazko, Rosângela Bergamasco and Angélica Marquetotti Salcedo Vieira
Membranes 2024, 14(10), 209; https://doi.org/10.3390/membranes14100209 - 28 Sep 2024
Abstract
Membrane technologies play a pivotal role in various industrial sectors, including food processing. Membranes act as barriers, selectively allowing the passage of one or other types of species. The separation processes that involve them offer advantages such as continuity, energy efficiency, compactness of
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Membrane technologies play a pivotal role in various industrial sectors, including food processing. Membranes act as barriers, selectively allowing the passage of one or other types of species. The separation processes that involve them offer advantages such as continuity, energy efficiency, compactness of devices, operational simplicity, and minimal consumption of chemical reagents. The efficiency of membrane separation depends on various factors, such as morphology, composition, and process parameters. Fouling, a significant limitation in membrane processes, leads to a decline in performance over time. Anti-fouling strategies involve adjustments to process parameters or direct modifications to the membrane, aiming to enhance efficiency. Recent research has focused on mitigating fouling, particularly in the food industry, where complex organic streams pose challenges. Membrane processes address consumer demands for natural and healthy products, contributing to new formulations with antioxidant properties. These trends align with environmental concerns, emphasizing sustainable practices. Despite numerous works on membrane modification, a research gap exists, especially with regard to the application of modified membranes in the food industry. This review aims to systematize information on modified membranes, providing insights into their practical application. This comprehensive overview covers membrane modification methods, fouling mechanisms, and distinct applications in the food sector. This study highlights the potential of modified membranes for specific tasks in the food industry and encourages further research in this promising field.
Full article
(This article belongs to the Section Membrane Applications for Other Areas)
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<p>Annual publications on modified membranes with application in food areas from 2016 to 2023. Bars and dashed line reflect annual growth through 2022 and decline in 2023 are highlighted.</p> Full article ">Figure 2
<p>Keywords utilized in chosen articles and central countries whose authors published in the modified membrane field within the food sector between 2020 and 2024 are depicted: (<b>A</b>) keyword map indicating five points of similarity among articles; (<b>B</b>) collaboration network map among countries identified with a minimum of five citations.</p> Full article ">Figure 3
<p>Application of pressure-driven membrane separation for removal of different species from liquids.</p> Full article ">Figure 4
<p>Scheme of electrodialysis: The colored bars refer to the sequential arrangement of anodes and cathodes, incorporating cation exchange membranes (orange to green—concentrate) and anion exchange membranes (red to green—concentrate). When both ions are present, the bar is represented by blue—diluted.</p> Full article ">Figure 5
<p>Scheme of membrane distillation: The different shapes represent solid compounds and/or microorganisms that may be present in the liquid. With the change in pressure during distillation, only vapor will pass through the hydrophobic membrane (blue circles).</p> Full article ">Figure 6
<p>Tocopherol recovery in oil industry using modified membrane by [<a href="#B95-membranes-14-00209" class="html-bibr">95</a>].</p> Full article ">
<p>Annual publications on modified membranes with application in food areas from 2016 to 2023. Bars and dashed line reflect annual growth through 2022 and decline in 2023 are highlighted.</p> Full article ">Figure 2
<p>Keywords utilized in chosen articles and central countries whose authors published in the modified membrane field within the food sector between 2020 and 2024 are depicted: (<b>A</b>) keyword map indicating five points of similarity among articles; (<b>B</b>) collaboration network map among countries identified with a minimum of five citations.</p> Full article ">Figure 3
<p>Application of pressure-driven membrane separation for removal of different species from liquids.</p> Full article ">Figure 4
<p>Scheme of electrodialysis: The colored bars refer to the sequential arrangement of anodes and cathodes, incorporating cation exchange membranes (orange to green—concentrate) and anion exchange membranes (red to green—concentrate). When both ions are present, the bar is represented by blue—diluted.</p> Full article ">Figure 5
<p>Scheme of membrane distillation: The different shapes represent solid compounds and/or microorganisms that may be present in the liquid. With the change in pressure during distillation, only vapor will pass through the hydrophobic membrane (blue circles).</p> Full article ">Figure 6
<p>Tocopherol recovery in oil industry using modified membrane by [<a href="#B95-membranes-14-00209" class="html-bibr">95</a>].</p> Full article ">
Open AccessArticle
Multienzyme Immobilization on PVDF Membrane via One-Step Mussel-Inspired Method: Enhancing Fouling Resistance and Self-Cleaning Efficiency
by
Jéssica Mulinari, Diane Rigo, Carolina Elisa Demaman Oro, Alessandra Cristina de Meneses, Guilherme Zin, Rafael Vidal Eleutério, Marcus Vinícius Tres and Rogério Marcos Dallago
Membranes 2024, 14(10), 208; https://doi.org/10.3390/membranes14100208 - 27 Sep 2024
Abstract
Immobilizing different enzymes on membranes can result in biocatalytic active membranes with a self-cleaning capacity toward a complex mixture of foulants. The membrane modification can reduce fouling and enhance filtration performance. Protease, lipase, and amylase were immobilized on poly(vinylidene fluoride) (PVDF) microfiltration membranes
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Immobilizing different enzymes on membranes can result in biocatalytic active membranes with a self-cleaning capacity toward a complex mixture of foulants. The membrane modification can reduce fouling and enhance filtration performance. Protease, lipase, and amylase were immobilized on poly(vinylidene fluoride) (PVDF) microfiltration membranes using a polydopamine coating in a one-step method. The concentrations of polydopamine precursor and enzymes were optimized during the immobilization. The higher hydrolytic activities were obtained using 0.2 mg/mL of dopamine hydrochloride and 4 mg/mL of enzymes: 0.90 mgstarch/min·cm2 for amylase, 10.16 nmoltyrosine/min·cm2 for protease, and 20.48 µmolp-nitrophenol/min·cm2 for lipase. Filtration tests using a protein, lipid, and carbohydrate mixture showed that the modified membrane retained 41%, 29%, and 28% of its initial water permeance (1808 ± 39 L/m2·h·bar) after three consecutive filtration cycles, respectively. In contrast, the pristine membrane (initial water permeance of 2016 ± 40 L/m2·h·bar) retained only 23%, 12%, and 8%. Filtrations of milk powder solution were also performed to simulate dairy industry wastewater: the modified membrane maintained 28%, 26%, and 26% of its initial water permeance after three consecutive filtration cycles, respectively, and the pristine membrane retained 34%, 21%, and 7%. The modified membrane showed increased fouling resistance against a mixture of foulants and presented a similar water permeance after three cycles of simulated dairy wastewater filtration. Membrane fouling is reduced by the immobilized enzymes through two mechanisms: increased membrane hydrophilicity (evidenced by the reduced water contact angle after modification) and the enzymatic hydrolysis of foulants as they accumulate on the membrane surface.
Full article
(This article belongs to the Special Issue Membrane Technologies in Food Industry and Bioprocessing)
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<p>Response surfaces representing the behavior of the hydrolytic activity of the immobilized (<b>a</b>) amylase, (<b>b</b>) lipase, and (<b>c</b>) protease.</p> Full article ">Figure 2
<p>WCA of the pristine, PDA-coated (0.2 mg/mL), and PDA + EN (0.2 mg/mL of DA and 4 mg/mL of EN) modified membranes.</p> Full article ">Figure 3
<p>ATR-FTIR of the pristine and PDA-coated (DA, 0.2 mg/mL) membranes, the membrane with immobilized enzymes by PDA (DA + EN, 0.2 mg/mL of DA and 4 mg/mL of EN), and the lyophilized protease (Alcalase 2.4L), amylase (Termamyl BrewQ), and lipase (ET2).</p> Full article ">Figure 4
<p>Initial pure water permeance of the pristine, PDA-coated (0.2 mg/mL), and PDA + EN (0.2 mg/mL of DA and 4 mg/mL of EN) modified membranes and pure water permeance after three consecutive filtration steps of (<b>a</b>) a mixture of starch (0.75 g/L), soybean oil (1 g/L), and casein (0.5 g/L), and (<b>b</b>) milk powder (2 g/L). Relative pure water flux of the membranes after each filtration step of the (<b>c</b>) mixture and (<b>d</b>) milk powder.</p> Full article ">
<p>Response surfaces representing the behavior of the hydrolytic activity of the immobilized (<b>a</b>) amylase, (<b>b</b>) lipase, and (<b>c</b>) protease.</p> Full article ">Figure 2
<p>WCA of the pristine, PDA-coated (0.2 mg/mL), and PDA + EN (0.2 mg/mL of DA and 4 mg/mL of EN) modified membranes.</p> Full article ">Figure 3
<p>ATR-FTIR of the pristine and PDA-coated (DA, 0.2 mg/mL) membranes, the membrane with immobilized enzymes by PDA (DA + EN, 0.2 mg/mL of DA and 4 mg/mL of EN), and the lyophilized protease (Alcalase 2.4L), amylase (Termamyl BrewQ), and lipase (ET2).</p> Full article ">Figure 4
<p>Initial pure water permeance of the pristine, PDA-coated (0.2 mg/mL), and PDA + EN (0.2 mg/mL of DA and 4 mg/mL of EN) modified membranes and pure water permeance after three consecutive filtration steps of (<b>a</b>) a mixture of starch (0.75 g/L), soybean oil (1 g/L), and casein (0.5 g/L), and (<b>b</b>) milk powder (2 g/L). Relative pure water flux of the membranes after each filtration step of the (<b>c</b>) mixture and (<b>d</b>) milk powder.</p> Full article ">
Open AccessArticle
Improved Flux Performance in Brackish Water Reverse Osmosis Membranes by Modification with ZnO Nanoparticles and Interphase Polymerization
by
Jesús Álvarez-Sánchez, Germán Eduardo Dévora-Isiordia, Claudia Muro, Yedidia Villegas-Peralta, Reyna Guadalupe Sánchez-Duarte, Patricia Guadalupe Torres-Valenzuela and Sergio Pérez-Sicairos
Membranes 2024, 14(10), 207; https://doi.org/10.3390/membranes14100207 - 27 Sep 2024
Abstract
With each passing year, water scarcity in the world is increasing, drying up rivers, lakes, and dams. Reverse osmosis technology is a very viable alternative which helps to reduce water shortages. One of the challenges is to make the process more efficient, and
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With each passing year, water scarcity in the world is increasing, drying up rivers, lakes, and dams. Reverse osmosis technology is a very viable alternative which helps to reduce water shortages. One of the challenges is to make the process more efficient, and this can be achieved by improving the capacity by adapting membranes with nanomaterials in order to increase the permeate flux without exceeding the limits established in the process. In this research, brackish water membranes (BW30) were modified with ZnO nanoparticles by interphase polymerization. The modified membranes and BW30 (unmodified) were characterized by FTIR, AFM, contact angle, and micrometer. The membranes were tested in a cross-flow apparatus using 9000 ppm brackish water, and their permeate flux, salt rejection, and concentration polarization were determined. The salt rejection for the 10 mg ZnO NP membrane was 97.13 and 97.77% at 20 and 30 Hz, respectively, sufficient to generate drinking water. It obtained the best permeate flux of 12.2% compared to the BW30 membrane with 122.63 L m−2 h−1 at 6.24 MPa and 30 Hz, under these conditions, and the concentration polarization increased.
Full article
(This article belongs to the Special Issue Membrane Processes for Water Recovery in Food Processing Industries)
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<p>Mexico Drought Monitor by CONAGUA, 30 June 2024 [<a href="#B4-membranes-14-00207" class="html-bibr">4</a>].</p> Full article ">Figure 2
<p>Concentration polarization in reverse osmosis membrane [<a href="#B10-membranes-14-00207" class="html-bibr">10</a>].</p> Full article ">Figure 3
<p>Procedure used to modify membranes with interfacial polymerization and ZnO NP [<a href="#B9-membranes-14-00207" class="html-bibr">9</a>].</p> Full article ">Figure 4
<p>IR spectra of unmodified and modified membranes: BW30 (blue line), Control (pink line), 5 mg ZnO NP (purple line), 10 mg ZnO NP (green line), and 15 mg ZnO NP (red line).</p> Full article ">Figure 5
<p>The reaction between piperazine and 1,3,5-Benzenetricarbonyl trichloride (TMC) to synthesize the net polyamide [<a href="#B8-membranes-14-00207" class="html-bibr">8</a>].</p> Full article ">Figure 6
<p>Membrane surface contact angle measurements.</p> Full article ">Figure 7
<p>Analysis AFM 2D (10 × 10 µm): (<b>a</b>) BW30, (<b>b</b>) Control, (<b>c</b>) 5 mg ZnO NP, (<b>d</b>) 10 mg ZnO NP, and (<b>e</b>) 15 mg ZnO NP. The red arrows indicate an agglomerate of ZnO NP.</p> Full article ">Figure 8
<p>3D AFM results showing surface roughness for the tested membranes: (<b>a</b>) BW30, (<b>b</b>) Control, (<b>c</b>) 5 mg ZnO NP, (<b>d</b>) 10 mg ZnO NP, and (<b>e</b>) 15 mg ZnO NP. Scan area 10 × 10 µm.</p> Full article ">Figure 9
<p>SEM images at 1 µm: (<b>A</b>) BW30 membrane, (<b>B</b>) control membrane, (<b>C</b>) 5 mg ZnO NP membrane, (<b>D</b>) 10 mg ZnO NP membrane and (<b>E</b>) 15 mg ZnO NP membrane. The red arrow indicates the agglomerates.</p> Full article ">Figure 10
<p>Pressure versus flux of the membranes: BW30, control, 5 mg ZnO NP, 10 mg ZnO NP, and 15 mg ZnO NP. (<b>a</b>) 20 Hz and (<b>b</b>) 30 Hz.</p> Full article ">Figure 11
<p>Distribution of nanoparticles on the surface of ZnO NP-modified membranes and their corresponding flux at 20 and 30 Hz and at an operating pressure of 5 MPa. (<b>a</b>) 5 mg ZnO NP, (<b>b</b>) 10 mg ZnO NP and (<b>c</b>) 15 mg ZnO NP.</p> Full article ">Figure 12
<p>Pressure versus salt rejection of the membranes: BW30, control, 5 mg ZnO NP, 10 mg ZnO NP, and 15 mg ZnO NP. (<b>a</b>) 20 Hz and (<b>b</b>) 30 Hz.</p> Full article ">Figure 13
<p>Pressure versus concentration of polarization of the membranes: BW30, control, 5 mg ZnO NP, 10 mg ZnO NP, and 15 mg ZnO NP. (<b>a</b>) 20 Hz and (<b>b</b>) 30 Hz.</p> Full article ">
<p>Mexico Drought Monitor by CONAGUA, 30 June 2024 [<a href="#B4-membranes-14-00207" class="html-bibr">4</a>].</p> Full article ">Figure 2
<p>Concentration polarization in reverse osmosis membrane [<a href="#B10-membranes-14-00207" class="html-bibr">10</a>].</p> Full article ">Figure 3
<p>Procedure used to modify membranes with interfacial polymerization and ZnO NP [<a href="#B9-membranes-14-00207" class="html-bibr">9</a>].</p> Full article ">Figure 4
<p>IR spectra of unmodified and modified membranes: BW30 (blue line), Control (pink line), 5 mg ZnO NP (purple line), 10 mg ZnO NP (green line), and 15 mg ZnO NP (red line).</p> Full article ">Figure 5
<p>The reaction between piperazine and 1,3,5-Benzenetricarbonyl trichloride (TMC) to synthesize the net polyamide [<a href="#B8-membranes-14-00207" class="html-bibr">8</a>].</p> Full article ">Figure 6
<p>Membrane surface contact angle measurements.</p> Full article ">Figure 7
<p>Analysis AFM 2D (10 × 10 µm): (<b>a</b>) BW30, (<b>b</b>) Control, (<b>c</b>) 5 mg ZnO NP, (<b>d</b>) 10 mg ZnO NP, and (<b>e</b>) 15 mg ZnO NP. The red arrows indicate an agglomerate of ZnO NP.</p> Full article ">Figure 8
<p>3D AFM results showing surface roughness for the tested membranes: (<b>a</b>) BW30, (<b>b</b>) Control, (<b>c</b>) 5 mg ZnO NP, (<b>d</b>) 10 mg ZnO NP, and (<b>e</b>) 15 mg ZnO NP. Scan area 10 × 10 µm.</p> Full article ">Figure 9
<p>SEM images at 1 µm: (<b>A</b>) BW30 membrane, (<b>B</b>) control membrane, (<b>C</b>) 5 mg ZnO NP membrane, (<b>D</b>) 10 mg ZnO NP membrane and (<b>E</b>) 15 mg ZnO NP membrane. The red arrow indicates the agglomerates.</p> Full article ">Figure 10
<p>Pressure versus flux of the membranes: BW30, control, 5 mg ZnO NP, 10 mg ZnO NP, and 15 mg ZnO NP. (<b>a</b>) 20 Hz and (<b>b</b>) 30 Hz.</p> Full article ">Figure 11
<p>Distribution of nanoparticles on the surface of ZnO NP-modified membranes and their corresponding flux at 20 and 30 Hz and at an operating pressure of 5 MPa. (<b>a</b>) 5 mg ZnO NP, (<b>b</b>) 10 mg ZnO NP and (<b>c</b>) 15 mg ZnO NP.</p> Full article ">Figure 12
<p>Pressure versus salt rejection of the membranes: BW30, control, 5 mg ZnO NP, 10 mg ZnO NP, and 15 mg ZnO NP. (<b>a</b>) 20 Hz and (<b>b</b>) 30 Hz.</p> Full article ">Figure 13
<p>Pressure versus concentration of polarization of the membranes: BW30, control, 5 mg ZnO NP, 10 mg ZnO NP, and 15 mg ZnO NP. (<b>a</b>) 20 Hz and (<b>b</b>) 30 Hz.</p> Full article ">
Open AccessArticle
Nanostructured Affinity Membrane to Isolate Extracellular Vesicles from Body Fluids for Diagnostics and Regenerative Medicine
by
Monica Torsello, Margherita Animini, Chiara Gualandi, Francesca Perut, Antonino Pollicino, Cristiana Boi and Maria Letizia Focarete
Membranes 2024, 14(10), 206; https://doi.org/10.3390/membranes14100206 - 26 Sep 2024
Abstract
Electrospun regenerated cellulose (RC) nanofiber membranes were prepared starting from cellulose acetate (CA) with different degrees of substitution. The process was optimized to obtain continuous and uniformly sized CA fibers. After electrospinning, the CA membranes were heat-treated to increase their tensile strength before
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Electrospun regenerated cellulose (RC) nanofiber membranes were prepared starting from cellulose acetate (CA) with different degrees of substitution. The process was optimized to obtain continuous and uniformly sized CA fibers. After electrospinning, the CA membranes were heat-treated to increase their tensile strength before deacetylation to obtain regenerated cellulose (RC). Affinity membranes were obtained by functionalization, exploiting the hydroxyl groups on the cellulose backbone. 1,4-Butanediol-diglycidyl ether was used to introduce epoxy groups onto the membrane, which was further bioconjugated with the anti-CD63 antibody targeting the tetraspanin CD63 on the extracellular vesicle membrane surface. The highest ligand density was obtained with an anti-CD63 antibody concentration of 6.4 µg/mL when bioconjugation was performed in carbonate buffer. The resulting affinity membrane was tested for the adsorption of extracellular vesicles (EVs) from human platelet lysate, yielding a very promising binding capacity above 10 mg/mL and demonstrating the suitability of this approach.
Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Membrane Materials and Applications)
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<p>SEM images of CA (ds = 3.0) samples electrospun from different starting solutions: (<b>a</b>) 10 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 90:10 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), (<b>b</b>) 8 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 90:10 (<span class="html-italic">v</span>/<span class="html-italic">v</span>) (optical microscope image), (<b>c</b>) 10 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 80:20 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), (<b>d</b>) 8 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 80:20 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), (<b>e</b>) 6 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 80:20 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), (<b>f</b>) 10 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 70:30 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), (<b>g</b>) 8 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 70:30 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), and (<b>h</b>) 6 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 70:30 (<span class="html-italic">v</span>/<span class="html-italic">v</span>). SEM scale bar = 5 µm; optical microscope scale bar = 20 µm.</p> Full article ">Figure 2
<p>SEM images of CA (<b>a</b>) and RC (<b>b</b>) fibrous mats (scale bar = 5 μm); fiber diameter distribution of CA (<b>c</b>) and RC (<b>d</b>).</p> Full article ">Figure 3
<p>(<b>a</b>) Comparison of the ATR-FTIR spectra of cellulose acetate (CA, red) and regenerated cellulose (RC, black); water drop profiles on CA (<b>b</b>) and RC (<b>c</b>) electrospun samples.</p> Full article ">Figure 4
<p>Thermal characterization of CA and RC electrospun mats: (<b>a</b>) comparison of the TGA (solid lines) and DTGA (dashed lines) measurements for CA (red) and RC (black) mats; (<b>b</b>) and (<b>c</b>) DSC measurements (first heating scan and second heating scan after quenching) of CA and RC electrospun mat, respectively.</p> Full article ">Figure 5
<p>XPS spectra of CA and RC electrospun mats: (<b>a</b>) widescan (<b>b</b>) C1s envelope and its components (<b>c</b>) O1s envelope and its components.</p> Full article ">Figure 6
<p>(<b>a</b>) Chemical structure of RC functionalized with BDDE; (<b>b</b>) XPS widescan and (<b>c</b>) C1s envelope of functionalized RC.</p> Full article ">Figure 7
<p>(<b>a</b>) Schematic of the bioconjugation of the membranes and (<b>b</b>) quantification through fluorescence intensity and a fluorescence image of the fiber with the best conjugation (Ab-FITC concentration of 6.4 µg/mL rinsed in carbonate buffer).</p> Full article ">Figure 8
<p>Adsorption test and scheme of the BCA quantification of EVs.</p> Full article ">
<p>SEM images of CA (ds = 3.0) samples electrospun from different starting solutions: (<b>a</b>) 10 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 90:10 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), (<b>b</b>) 8 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 90:10 (<span class="html-italic">v</span>/<span class="html-italic">v</span>) (optical microscope image), (<b>c</b>) 10 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 80:20 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), (<b>d</b>) 8 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 80:20 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), (<b>e</b>) 6 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 80:20 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), (<b>f</b>) 10 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 70:30 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), (<b>g</b>) 8 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 70:30 (<span class="html-italic">v</span>/<span class="html-italic">v</span>), and (<b>h</b>) 6 <span class="html-italic">w</span>/<span class="html-italic">v</span>% in DCM:EtOH = 70:30 (<span class="html-italic">v</span>/<span class="html-italic">v</span>). SEM scale bar = 5 µm; optical microscope scale bar = 20 µm.</p> Full article ">Figure 2
<p>SEM images of CA (<b>a</b>) and RC (<b>b</b>) fibrous mats (scale bar = 5 μm); fiber diameter distribution of CA (<b>c</b>) and RC (<b>d</b>).</p> Full article ">Figure 3
<p>(<b>a</b>) Comparison of the ATR-FTIR spectra of cellulose acetate (CA, red) and regenerated cellulose (RC, black); water drop profiles on CA (<b>b</b>) and RC (<b>c</b>) electrospun samples.</p> Full article ">Figure 4
<p>Thermal characterization of CA and RC electrospun mats: (<b>a</b>) comparison of the TGA (solid lines) and DTGA (dashed lines) measurements for CA (red) and RC (black) mats; (<b>b</b>) and (<b>c</b>) DSC measurements (first heating scan and second heating scan after quenching) of CA and RC electrospun mat, respectively.</p> Full article ">Figure 5
<p>XPS spectra of CA and RC electrospun mats: (<b>a</b>) widescan (<b>b</b>) C1s envelope and its components (<b>c</b>) O1s envelope and its components.</p> Full article ">Figure 6
<p>(<b>a</b>) Chemical structure of RC functionalized with BDDE; (<b>b</b>) XPS widescan and (<b>c</b>) C1s envelope of functionalized RC.</p> Full article ">Figure 7
<p>(<b>a</b>) Schematic of the bioconjugation of the membranes and (<b>b</b>) quantification through fluorescence intensity and a fluorescence image of the fiber with the best conjugation (Ab-FITC concentration of 6.4 µg/mL rinsed in carbonate buffer).</p> Full article ">Figure 8
<p>Adsorption test and scheme of the BCA quantification of EVs.</p> Full article ">
Open AccessArticle
Enhanced Pollutant Removal and Antifouling in an Aerobic Ceramic Membrane Bioreactor with Bentonite for Pharmaceutical Wastewater Treatment
by
Salaheddine Elmoutez, Hafida Ayyoub, Mohamed Chaker Necibi, Azzedine Elmidaoui and Mohamed Taky
Membranes 2024, 14(10), 205; https://doi.org/10.3390/membranes14100205 - 26 Sep 2024
Abstract
This study examined the impact of adding bentonite clay (concentration of 1.5 to 10 g/L) to a pilot-scale aerobic ceramic membrane bioreactor (AeCMBR) for treating pharmaceutical wastewater (PhWW). The hydraulic retention time (HRT) was maintained at 24 h; the dissolved oxygen was between
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This study examined the impact of adding bentonite clay (concentration of 1.5 to 10 g/L) to a pilot-scale aerobic ceramic membrane bioreactor (AeCMBR) for treating pharmaceutical wastewater (PhWW). The hydraulic retention time (HRT) was maintained at 24 h; the dissolved oxygen was between 2 mg/L (on) and 4 mg/L (off) throughout operation. Organic and nitrogen pollution removal rates and heavy metal (Cu, Ni, Pb, Zn) reduction rates were assessed. The chemical oxygen demand (COD) removal efficiency exceeded 82%. Adsorption improved ammonia (NH4+) removal to 78%; the addition of 5 g of bentonite resulted in a 38% improvement compared with the process without bentonite. The average nitrate concentration decreased from 169.69 mg/L to 43.72 mg/L. The average removal efficiencies for Cu, Ni, Pb and Zn were 86%, 68.52%, 46.90% and 56.76%, respectively. Bentonite at 5 g/L significantly reduced membrane fouling. The cost–benefit analysis enabled us to predict that the process will meet the multiple objectives of durability, treatment performance and economic viability. The combination of an AeCMBR and bentonite adsorption has proven to be a valuable solution for treating highly polluted wastewater.
Full article
(This article belongs to the Topic Technologies for Wastewater and Sludge Treatment)
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<p>Schematic illustration of the AeCMBR pilot configuration.</p> Full article ">Figure 2
<p>COD concentration in AeCMBR–bentonite supernatant and effluent.</p> Full article ">Figure 3
<p>NH4+ removal performance of the AeCMBR–bentonite system.</p> Full article ">Figure 4
<p>The variation in NO<sub>3</sub> removal during operation.</p> Full article ">Figure 5
<p>Adsorption behaviors of (<b>a</b>) Cu, (<b>b</b>) Ni, (<b>c</b>) Pb, (<b>d</b>) Zn in the AeCMBR–bentonite system.</p> Full article ">Figure 6
<p>Total membrane resistance as a function of bentonite concentration.</p> Full article ">
<p>Schematic illustration of the AeCMBR pilot configuration.</p> Full article ">Figure 2
<p>COD concentration in AeCMBR–bentonite supernatant and effluent.</p> Full article ">Figure 3
<p>NH4+ removal performance of the AeCMBR–bentonite system.</p> Full article ">Figure 4
<p>The variation in NO<sub>3</sub> removal during operation.</p> Full article ">Figure 5
<p>Adsorption behaviors of (<b>a</b>) Cu, (<b>b</b>) Ni, (<b>c</b>) Pb, (<b>d</b>) Zn in the AeCMBR–bentonite system.</p> Full article ">Figure 6
<p>Total membrane resistance as a function of bentonite concentration.</p> Full article ">
Open AccessArticle
Chemical Cleaning Techniques for Fouled RO Membranes: Enhancing Fouling Removal and Assessing Microbial Composition
by
Mohammed A. Al-Balushi, Htet Htet Kyaw, Myo Tay Zar Myint, Mohammed Al-Abri and Sergey Dobretsov
Membranes 2024, 14(10), 204; https://doi.org/10.3390/membranes14100204 - 26 Sep 2024
Abstract
Membrane fouling, a major challenge in desalination, is addressed in this study by investigating three different chemical cleaning protocols (A, B, and C) targeting fouled reverse osmosis (RO) membranes and microbial community composition. Cleaning protocols A and B involve different chemical treatments selected
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Membrane fouling, a major challenge in desalination, is addressed in this study by investigating three different chemical cleaning protocols (A, B, and C) targeting fouled reverse osmosis (RO) membranes and microbial community composition. Cleaning protocols A and B involve different chemical treatments selected based on preliminary tests and literature review, while protocol C follows the manufacturer’s standard recommendation. Membrane morphology, foulant composition, and microbial community variability in fouled, virgin, and cleaned membranes are studied. Effective biofilm removal is observed across all protocols using scanning electron microscopy (SEM), while spectroscopic techniques highlight interactions between foulants and membranes. Importantly, a critical gap in understanding how cleaning strategies influence microbial communities on membranes is addressed. Shifts in dominant bacterial phyla (Proteobacteria, Firmicutes, and Actinobacteria) after cleaning are identified through 16S rRNA amplicon sequencing. Cleaning A showed the best results in reducing microbial counts and restoring composition similar to virgin membranes. Additionally, chemical treatment increased dominance of resistant genera such as Staphylococcus, Bacillus, Citrobacter, and Burkholderia. This study emphasizes the necessity for tailored fouling cleaning strategies for RO membranes, with Cleaning A is a promising solution, paving the way for enhanced water purification technologies.
Full article
(This article belongs to the Special Issue Membranes Processes for Marine Environment)
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Figure 1
Figure 1
<p>Comparative SEM Investigation of RO membranes subjected to chemical treatment and non-treatment, featuring (<b>A</b>) virgin, (<b>B</b>) fouled, (<b>C</b>) Cleaning A, (<b>D</b>) Cleaning B, and (<b>E</b>) Cleaning C.</p> Full article ">Figure 2
<p>SEM images of some of the diatoms of (<b>A</b>) <span class="html-italic">Thalassiosira</span> sp., (<b>B</b>) <span class="html-italic">Navicula</span> sp., (<b>C</b>) and (<b>D</b>) <span class="html-italic">Amphora</span> sp. found on the surface of the fouled RO membranes.</p> Full article ">Figure 3
<p>FTIR spectra of fouled, virgin, and treated RO membranes: (<b>A</b>) range from 500 to 4000 cm<sup>−1</sup> and (<b>B</b>) range from 500 to 2000 cm<sup>−1</sup>.</p> Full article ">Figure 4
<p>(<b>A</b>) TGA, and (<b>B</b>) DSC spectra of virgin, fouled, and cleaned membranes. Faster weight loss is shown with dotted circle.</p> Full article ">Figure 5
<p>Water contact angle (WCA) measurement of fouled, virgin, and treated RO membrane.</p> Full article ">Figure 6
<p>Total count of microorganisms (CFU/mL) on RO membranes before (fouled and virgin) and after chemical treatment (Cleaning A–C) over two time intervals: (<b>A</b>) 30 min of incubation and (<b>B</b>) 24 h. Different letters suggest significant differences at the confidence level of <span class="html-italic">p</span> < 0.05.</p> Full article ">Figure 7
<p>Phylum-level phylogenetic distribution in biofilms formed on membrane surfaces before (virgin, fouled) and after chemical treatment (Cleaning A–C).</p> Full article ">Figure 8
<p>Genus-level phylogenetic distribution in biofilms on membrane surfaces before (virgin, fouled) and after chemical treatment (Cleaning A–C).</p> Full article ">Figure 9
<p>Number of OTUs in all treated and non-treated RO membranes (<b>A</b>); Venn diagram of OTUs shared between all membranes subject to chemical treatment and the ones not cleaned (fouled) (<b>B</b>); principle component analysis of OTUs (<b>C</b>).</p> Full article ">Figure 10
<p>Relative abundance of the archaeal community attached to RO membranes before and after chemical treatment.</p> Full article ">
<p>Comparative SEM Investigation of RO membranes subjected to chemical treatment and non-treatment, featuring (<b>A</b>) virgin, (<b>B</b>) fouled, (<b>C</b>) Cleaning A, (<b>D</b>) Cleaning B, and (<b>E</b>) Cleaning C.</p> Full article ">Figure 2
<p>SEM images of some of the diatoms of (<b>A</b>) <span class="html-italic">Thalassiosira</span> sp., (<b>B</b>) <span class="html-italic">Navicula</span> sp., (<b>C</b>) and (<b>D</b>) <span class="html-italic">Amphora</span> sp. found on the surface of the fouled RO membranes.</p> Full article ">Figure 3
<p>FTIR spectra of fouled, virgin, and treated RO membranes: (<b>A</b>) range from 500 to 4000 cm<sup>−1</sup> and (<b>B</b>) range from 500 to 2000 cm<sup>−1</sup>.</p> Full article ">Figure 4
<p>(<b>A</b>) TGA, and (<b>B</b>) DSC spectra of virgin, fouled, and cleaned membranes. Faster weight loss is shown with dotted circle.</p> Full article ">Figure 5
<p>Water contact angle (WCA) measurement of fouled, virgin, and treated RO membrane.</p> Full article ">Figure 6
<p>Total count of microorganisms (CFU/mL) on RO membranes before (fouled and virgin) and after chemical treatment (Cleaning A–C) over two time intervals: (<b>A</b>) 30 min of incubation and (<b>B</b>) 24 h. Different letters suggest significant differences at the confidence level of <span class="html-italic">p</span> < 0.05.</p> Full article ">Figure 7
<p>Phylum-level phylogenetic distribution in biofilms formed on membrane surfaces before (virgin, fouled) and after chemical treatment (Cleaning A–C).</p> Full article ">Figure 8
<p>Genus-level phylogenetic distribution in biofilms on membrane surfaces before (virgin, fouled) and after chemical treatment (Cleaning A–C).</p> Full article ">Figure 9
<p>Number of OTUs in all treated and non-treated RO membranes (<b>A</b>); Venn diagram of OTUs shared between all membranes subject to chemical treatment and the ones not cleaned (fouled) (<b>B</b>); principle component analysis of OTUs (<b>C</b>).</p> Full article ">Figure 10
<p>Relative abundance of the archaeal community attached to RO membranes before and after chemical treatment.</p> Full article ">
Open AccessArticle
Purification of Liquid Fraction of Digestates from Different Origins—Comparison of Polymeric and Ceramic Ultrafiltration Membranes Used for This Purpose
by
Agnieszka Urbanowska
Membranes 2024, 14(10), 203; https://doi.org/10.3390/membranes14100203 - 25 Sep 2024
Abstract
Circular economy, clean technologies, and renewable energy are key to climate protection and modern environmental technology. Recovering water and valuable minerals from the liquid fraction of digestate is in line with this strategy. Digestate, a byproduct of anaerobic methane fermentation in biogas plants,
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Circular economy, clean technologies, and renewable energy are key to climate protection and modern environmental technology. Recovering water and valuable minerals from the liquid fraction of digestate is in line with this strategy. Digestate, a byproduct of anaerobic methane fermentation in biogas plants, is a potential source of water, minerals for fertilizers, and energy rather than waste. This study examined digestate from municipal and agricultural biogas plants and highlights the need for research on both due to their differences. The use of membrane techniques for water recovery from liquid digestate offers an innovative alternative to conventional methods. This study used standalone membrane filtration and an integrated system to produce water suitable for agricultural use. Ceramic membranes with cut-offs of 1, 5, 15, and 50 kDa and polymeric membranes of polyethersulfone and regenerated cellulose with cut-offs of 10 and 30 kDa were tested. The results showed that the membrane material significantly affects the transport and separation properties. Higher cut-off values increased permeate flux across all membranes. Ceramic membranes were more susceptible to fouling in standalone ultrafiltration, but were more effective in purifying digestate than polymeric membranes. The best results were obtained with a ceramic membrane with a 1 kDa cut-off (for example, for the integrated process and the municipal digestate, the retention rates of COD, BOD5 and DOC were 69%, 62%, and 75%, respectively).
Full article
(This article belongs to the Special Issue Separation Techniques and Circular Economy)
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<p>SEM images of selected membranes (1000× magnification): (<b>a</b>) polymeric regenerated cellulose 10 kDa, (<b>b</b>) ceramic 5 kDa.</p> Full article ">Figure 2
<p>Laboratory setup with Millipore’s Amicon 8400 chamber (1—Amicon 8400 chamber, 2—membrane, 3—stirrer, 4—compressed nitrogen cylinder, 5—regulator).</p> Full article ">Figure 3
<p>Sterlitech laboratory installation (1—compressed nitrogen cylinder, 2—pressure vessel, 3—manometer, 4—safety valve, 5—ceramic diaphragm in housing).</p> Full article ">Figure 4
<p>Redistilled water flux for polymeric and ceramic membranes.</p> Full article ">Figure 5
<p>Effect of membrane type and cut-off value on permeate flux for the liquid fraction of municipal (<b>a</b>) and agricultural (<b>b</b>) digestate.</p> Full article ">Figure 6
<p>Relative permeability during standalone UF and during the integrated process: sedimentation/filtration/coagulation/sedimentation/UF of (<b>a</b>) the liquid fraction of municipal digestate and (<b>b</b>) the liquid fraction of agricultural digestate using polymeric and ceramic membranes.</p> Full article ">Figure 7
<p>pH dependence of the relative permeability of polymeric and ceramic membranes for integrated process: sedimentation/filtration/coagulation/sedimentation/UF of the liquid fraction of (<b>a</b>) municipal and (<b>b</b>) agricultural digestates.</p> Full article ">Figure 8
<p>Effectiveness of DOC removal and reduction in BOD<sub>5</sub> and COD when conducting (<b>a</b>) UF and (<b>b</b>) integrated process: sedimentation/filtration/coagulation/sedimentation/UF of the liquid fraction of municipal digestate using polymeric and ceramic membranes.</p> Full article ">Figure 9
<p>Effectiveness of DOC removal and reduction in BOD<sub>5</sub> and COD when conducting (<b>a</b>) UF and (<b>b</b>) integrated process: sedimentation/filtration/coagulation/sedimentation/UF of the liquid fraction of agricultural digestate using polymeric and ceramic membranes.</p> Full article ">Figure 10
<p>Influence of solution pH on the degree of DOC reduction on organic and inorganic membranes during treatment of the liquid fraction of municipal digestate by (<b>a</b>) UF and (<b>b</b>) integrated: sedimentation/filtration/coagulation/sedimentation/UF processes.</p> Full article ">Figure 11
<p>Influence of solution pH on the degree of DOC reduction on organic and inorganic membranes during treatment of the liquid fraction of agricultural digestate by (<b>a</b>) UF and (<b>b</b>) integrated: sedimentation/filtration/coagulation/sedimentation/UF processes.</p> Full article ">
<p>SEM images of selected membranes (1000× magnification): (<b>a</b>) polymeric regenerated cellulose 10 kDa, (<b>b</b>) ceramic 5 kDa.</p> Full article ">Figure 2
<p>Laboratory setup with Millipore’s Amicon 8400 chamber (1—Amicon 8400 chamber, 2—membrane, 3—stirrer, 4—compressed nitrogen cylinder, 5—regulator).</p> Full article ">Figure 3
<p>Sterlitech laboratory installation (1—compressed nitrogen cylinder, 2—pressure vessel, 3—manometer, 4—safety valve, 5—ceramic diaphragm in housing).</p> Full article ">Figure 4
<p>Redistilled water flux for polymeric and ceramic membranes.</p> Full article ">Figure 5
<p>Effect of membrane type and cut-off value on permeate flux for the liquid fraction of municipal (<b>a</b>) and agricultural (<b>b</b>) digestate.</p> Full article ">Figure 6
<p>Relative permeability during standalone UF and during the integrated process: sedimentation/filtration/coagulation/sedimentation/UF of (<b>a</b>) the liquid fraction of municipal digestate and (<b>b</b>) the liquid fraction of agricultural digestate using polymeric and ceramic membranes.</p> Full article ">Figure 7
<p>pH dependence of the relative permeability of polymeric and ceramic membranes for integrated process: sedimentation/filtration/coagulation/sedimentation/UF of the liquid fraction of (<b>a</b>) municipal and (<b>b</b>) agricultural digestates.</p> Full article ">Figure 8
<p>Effectiveness of DOC removal and reduction in BOD<sub>5</sub> and COD when conducting (<b>a</b>) UF and (<b>b</b>) integrated process: sedimentation/filtration/coagulation/sedimentation/UF of the liquid fraction of municipal digestate using polymeric and ceramic membranes.</p> Full article ">Figure 9
<p>Effectiveness of DOC removal and reduction in BOD<sub>5</sub> and COD when conducting (<b>a</b>) UF and (<b>b</b>) integrated process: sedimentation/filtration/coagulation/sedimentation/UF of the liquid fraction of agricultural digestate using polymeric and ceramic membranes.</p> Full article ">Figure 10
<p>Influence of solution pH on the degree of DOC reduction on organic and inorganic membranes during treatment of the liquid fraction of municipal digestate by (<b>a</b>) UF and (<b>b</b>) integrated: sedimentation/filtration/coagulation/sedimentation/UF processes.</p> Full article ">Figure 11
<p>Influence of solution pH on the degree of DOC reduction on organic and inorganic membranes during treatment of the liquid fraction of agricultural digestate by (<b>a</b>) UF and (<b>b</b>) integrated: sedimentation/filtration/coagulation/sedimentation/UF processes.</p> Full article ">
Open AccessArticle
Enhancing the Separation Performance of Cellulose Membranes Fabricated from 1-Ethyl-3-methylimidazolium Acetate by Introducing Acetone as a Co-Solvent
by
Luying Chen, Dooli Kim and Wiebe M. de Vos
Membranes 2024, 14(9), 202; https://doi.org/10.3390/membranes14090202 - 23 Sep 2024
Abstract
Cellulose, a sustainable raw material, holds great promise as an ideal candidate for membrane materials. In this work, we focused on establishing a low-cost route for producing cellulose microfiltration membranes by adopting a co-solvent system comprising the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) and
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Cellulose, a sustainable raw material, holds great promise as an ideal candidate for membrane materials. In this work, we focused on establishing a low-cost route for producing cellulose microfiltration membranes by adopting a co-solvent system comprising the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) and acetone. The introduction of acetone as a co-solvent into the casting solution allowed control over the viscosity, thereby significantly enhancing the morphologies and filtration performances of the resulting cellulose membranes. Indeed, applying this co-solvent allowed the water permeability to be significantly increased, while maintaining high rejections. Furthermore, the prepared cellulose membrane demonstrated excellent fouling resistance behavior and flux recovery behavior during a challenging oil-in-water emulsion filtration. These results highlight a promising approach to fabricate high-performance cellulose membranes.
Full article
(This article belongs to the Section Membrane Fabrication and Characterization)
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<p>Fabrication process of cellulose membranes.</p> Full article ">Figure 2
<p>Dynamic viscosity of the cellulose/[EMIM]OAc/acetone casting solution solutions at various mass loading of [EMIM]OAc to acetone.</p> Full article ">Figure 3
<p>Cross-sectional SEM images of membranes showing the effect of the acetone loading on membrane porous structure: (<b>a<sub>1</sub></b>–<b>a<sub>4</sub></b>) IL:acetone = 1:0; (<b>b<sub>1</sub></b>–<b>b<sub>4</sub></b>) IL:acetone = 4:1; (<b>c<sub>1</sub></b>–<b>c<sub>4</sub></b>) IL:acetone = 3:1. (<b>a<sub>1</sub></b>,<b>b<sub>1</sub></b>,<b>c<sub>1</sub></b>) show the overall cross-section images; (<b>a<sub>2</sub></b>,<b>b<sub>2</sub></b>,<b>c<sub>2</sub></b>) are enlarged view of the top part; (<b>a<sub>3</sub></b>,<b>b<sub>3</sub></b>,<b>c<sub>3</sub></b>) are enlarged view of the middle part; and (<b>a<sub>4</sub></b>,<b>b<sub>4</sub></b>,<b>c<sub>4</sub></b>) are enlarged view of the bottom part.</p> Full article ">Figure 4
<p>Top surface SEM images of membranes showing the effect of the acetone loading on membrane porous structure: (<b>a<sub>1</sub></b>–<b>a<sub>3</sub></b>) IL:acetone = 1:0; (<b>b<sub>1</sub></b>–<b>b<sub>3</sub></b>) IL:acetone = 4:1; and (<b>c<sub>1</sub></b>–<b>c<sub>3</sub></b>) IL:acetone = 3:1.</p> Full article ">Figure 5
<p>Pure water permeability of the membranes prepared in different acetone loadings in the casting solution.</p> Full article ">Figure 6
<p>Emulsion retention of the membranes prepared in different acetone loadings in the casting solution.</p> Full article ">Figure 7
<p>Original pure water permeability, permeability during the emulsion retention process, recovered water permeability after emulsion retention, and recovered water permeability after being washed with water for the membranes prepared in different acetone loadings in the casting solution.</p> Full article ">
<p>Fabrication process of cellulose membranes.</p> Full article ">Figure 2
<p>Dynamic viscosity of the cellulose/[EMIM]OAc/acetone casting solution solutions at various mass loading of [EMIM]OAc to acetone.</p> Full article ">Figure 3
<p>Cross-sectional SEM images of membranes showing the effect of the acetone loading on membrane porous structure: (<b>a<sub>1</sub></b>–<b>a<sub>4</sub></b>) IL:acetone = 1:0; (<b>b<sub>1</sub></b>–<b>b<sub>4</sub></b>) IL:acetone = 4:1; (<b>c<sub>1</sub></b>–<b>c<sub>4</sub></b>) IL:acetone = 3:1. (<b>a<sub>1</sub></b>,<b>b<sub>1</sub></b>,<b>c<sub>1</sub></b>) show the overall cross-section images; (<b>a<sub>2</sub></b>,<b>b<sub>2</sub></b>,<b>c<sub>2</sub></b>) are enlarged view of the top part; (<b>a<sub>3</sub></b>,<b>b<sub>3</sub></b>,<b>c<sub>3</sub></b>) are enlarged view of the middle part; and (<b>a<sub>4</sub></b>,<b>b<sub>4</sub></b>,<b>c<sub>4</sub></b>) are enlarged view of the bottom part.</p> Full article ">Figure 4
<p>Top surface SEM images of membranes showing the effect of the acetone loading on membrane porous structure: (<b>a<sub>1</sub></b>–<b>a<sub>3</sub></b>) IL:acetone = 1:0; (<b>b<sub>1</sub></b>–<b>b<sub>3</sub></b>) IL:acetone = 4:1; and (<b>c<sub>1</sub></b>–<b>c<sub>3</sub></b>) IL:acetone = 3:1.</p> Full article ">Figure 5
<p>Pure water permeability of the membranes prepared in different acetone loadings in the casting solution.</p> Full article ">Figure 6
<p>Emulsion retention of the membranes prepared in different acetone loadings in the casting solution.</p> Full article ">Figure 7
<p>Original pure water permeability, permeability during the emulsion retention process, recovered water permeability after emulsion retention, and recovered water permeability after being washed with water for the membranes prepared in different acetone loadings in the casting solution.</p> Full article ">
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