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Membranes
Volume 10
Issue 6
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Membranes, Volume 10, Issue 6 (June 2020) – 24 articles

Cover Story (view full-size image): The aim of this work is to study the combined effect of colloids and soluble microbial products (SMP) on membrane fouling. Two MBRs were investigated for treating two types of wastewater (wwt). Domestic wwt presented 5.5 times more SMP proteins and 11 times more SMP carbohydrates compared to the synthetic one. In contrast, synthetic wwt had 20% more colloids with a size lower than membrane pore size than domestic. Finally, the TMP at 36 days reached 16 kPa for synthetic wwt and 11 kPa for domestic. Consequently, the quantity of colloids and possibly their special characteristics play a more important role in membrane fouling compared to the SMP, a novel conclusion that can be used for mitigation of membranes fouling. View this paper
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15 pages, 3094 KiB  
Article
In-Situ Combination of Bipolar Membrane Electrodialysis with Monovalent Selective Anion-Exchange Membrane for the Valorization of Mixed Salts into Relatively High-Purity Monoprotic and Diprotic Acids
by Haiyang Yan, Wei Li, Yongming Zhou, Muhammad Irfan, Yaoming Wang, Chenxiao Jiang and Tongwen Xu
Membranes 2020, 10(6), 135; https://doi.org/10.3390/membranes10060135 - 26 Jun 2020
Cited by 15 | Viewed by 4381
Abstract
The crystalized mixed salts from the zero liquid discharge process are a hazardous threat to the environment. In this study, we developed a novel electrodialysis (SBMED) method by assembling the monovalent selective anion-exchange membrane (MSAEM) into the bipolar membrane electrodialysis (BMED) stack. By [...] Read more.
The crystalized mixed salts from the zero liquid discharge process are a hazardous threat to the environment. In this study, we developed a novel electrodialysis (SBMED) method by assembling the monovalent selective anion-exchange membrane (MSAEM) into the bipolar membrane electrodialysis (BMED) stack. By taking the advantages of water splitting in the bipolar membrane and high perm-selectivity of MSAEM for the Cl− ions against the SO42− ions, this combination allows the concurrent separation of Cl−/SO42− and conversion of mixed salts into relatively high-purity monoprotic and diprotic acids. The current density has a significant impact on the acid purity. Both the monoprotic and diprotic acid purities were higher than 80% at a low current density of 10 mA/cm2. The purities of the monoprotic acids decreased with an increase in the current density, indicating that the perm-selectivity of MSAEM decreases with increasing current density. An increase in the ratio of monovalent to divalent anions in the feed was beneficial to increase the purity of monoprotic acids. High-purity monoprotic acids in the range of 93.9–96.1% were obtained using this novel SBMED stack for treating simulated seawater. Therefore, it is feasible for SBMED to valorize the mixed salts into relatively high-purity monoprotic and diprotic acids in one step. Full article
(This article belongs to the Special Issue Membranes: 10th Anniversary)
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Figure 1

Figure 1
<p>A typical zero liquid discharge wastewater treating procedure.</p> Full article ">Figure 2
<p>Schematic diagram for the novel electrodialysis stack (SBMED) process. BPM, bipolar membrane; AEM, anion-exchange membrane; CEM, cation-exchange membrane; MSAEM, mono-selective anion-exchange membrane.</p> Full article ">Figure 3
<p>Effect of the current density on the voltage drop across the SEDBM stack and on the conductivity in the salt compartment.</p> Full article ">Figure 4
<p>Effect of the current density on the evolution of the acid concentration in the acid I compartment and base concentration as a function of time.</p> Full article ">Figure 5
<p>Effect of the current density on acid purity. (<b>a</b>) The evolution of HCl purity in the acid I compartment as a function of time; (<b>b</b>) the final HCl and H<sub>2</sub>SO<sub>4</sub> purity in the acid I and acid II compartments after the experiments, respectively. Other experimental conditions: feed in salt compartment, 0.05 mol/L NaCl + 0.05 mol/L Na<sub>2</sub>SO<sub>4</sub>; electrode rinse solution, 0.3 mol/L Na<sub>2</sub>SO<sub>4</sub>; flow rate of each circulation, 200 mL/min.</p> Full article ">Figure 6
<p>Effect of the monovalent and divalent components on the voltage drop across the SBMED stack, conductivity evolution curves in the salt compartment and HCl purity in the acid I compartment. Other experimental conditions: current density, 20 mA/cm<sup>2</sup>; electrode rinse solution, 0.3 mol/L Na<sub>2</sub>SO<sub>4</sub>; flow rate of each circulation, 200 mL/min.</p> Full article ">Figure 7
<p>The influence of the mixed salt component on the current efficiency and energy consumption. (<b>a</b>) Current efficiency in the acid I and base compartment for the different salt components; (<b>b</b>) energy consumption for the produced HCl and NaOH.</p> Full article ">Figure 8
<p>The SBMED performances, i.e., voltage drop curve as a function of time, HCl purity in the acid I compartment, acid concentration curve in the acid I compartment and base concentration curve in the base compartment using simulated seawater.</p> Full article ">
21 pages, 3305 KiB  
Article
Characterization of Poly(Acrylic) Acid-Modified Heterogenous Anion Exchange Membranes with Improved Monovalent Permselectivity for RED
by Ivan Merino-Garcia, Francis Kotoka, Carla A.M. Portugal, João G. Crespo and Svetlozar Velizarov
Membranes 2020, 10(6), 134; https://doi.org/10.3390/membranes10060134 - 26 Jun 2020
Cited by 22 | Viewed by 4056
Abstract
The performance of anion-exchange membranes (AEMs) in Reverse Electrodialysis is hampered by both presence of multivalent ions and fouling phenomena, thus leading to reduced net power density. Therefore, we propose a monolayer surface modification procedure to functionalize Ralex-AEMs with poly(acrylic) acid (PAA) in [...] Read more.
The performance of anion-exchange membranes (AEMs) in Reverse Electrodialysis is hampered by both presence of multivalent ions and fouling phenomena, thus leading to reduced net power density. Therefore, we propose a monolayer surface modification procedure to functionalize Ralex-AEMs with poly(acrylic) acid (PAA) in order to (i) render a monovalent permselectivity, and (ii) minimize organic fouling. Membrane surface modification was carried out by putting heterogeneous AEMs in contact with a PAA-based aqueous solution for 24 h. The resulting modified membranes were firstly characterized by contact angle, water uptake, ion exchange capacity, fixed charge density, and swelling degree measurements, whereas their electrochemical responses were evaluated through cyclic voltammetry. Besides, their membrane electro-resistance was also studied via electrochemical impedance spectroscopy analyses. Finally, membrane permselectivity and fouling behavior in the presence of humic acid were evaluated through mass transport experiments using model NaCl containing solutions. The use of modified PAA-AEMs resulted in a significantly enhanced monovalent permselectivity (sulfate rejection improved by >35%) and membrane hydrophilicity (contact angle decreased by >15%) in comparison with the behavior of unmodified Ralex-AEMs, without compromising the membrane electro-resistance after modification, thus demonstrating the technical feasibility of the proposed membrane modification procedure. This study may therefore provide a feasible way for achieving an improved Reverse Electrodialysis process efficiency. Full article
(This article belongs to the Special Issue Electromembrane Processes: Experiments and Modelling)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Anion exchange membrane diagram including both electric double-layer (EDL) and diffusion boundary layer (DBL) effects, adapted with permission from [<a href="#B40-membranes-10-00134" class="html-bibr">40</a>]. Copyright 2016 Elsevier.</p> Full article ">Figure 2
<p>Two-compartment diffusion cell layout.</p> Full article ">Figure 3
<p>Hydrophilicity analysis: contact angle data.</p> Full article ">Figure 4
<p>Fourier attenuated atomic force microscopy (<span class="html-italic">ATR-FTIR</span>) spectra of unmodified and poly(acrylic) acid (PAA)-modified AEMs.</p> Full article ">Figure 5
<p>Cyclic voltammetry analyses: effect of PAA concentration in AEM modification at Ag electrodes.</p> Full article ">Figure 6
<p>Equivalent circuit diagram showing the combination of membrane, electric double-layer, and diffusion boundary layer resistances.</p> Full article ">Figure 7
<p>Electrochemical impedance spectroscopy (<span class="html-italic">EIS</span>) study of the unmodified membrane including experimental (continuous line) and fitting data (dotted lined): (<b>a</b>) Bode plot; (<b>b</b>) Nyquist plot.</p> Full article ">Figure 8
<p>Sulfate evolution with time during mass transport experiments as a function of the AEM used in the absence of humic acid (HA) in the feed compartment.</p> Full article ">Figure 9
<p>HA studies: sulfate evolution with time during mass transport experiments as a function of the one side modified AEM used.</p> Full article ">
11 pages, 2663 KiB  
Article
Microfiltration Membranes Modified with Silver Oxide by Plasma Treatment
by Joanna Kacprzyńska-Gołacka, Anna Kowalik-Klimczak, Ewa Woskowicz, Piotr Wieciński, Monika Łożyńska, Sylwia Sowa, Wioletta Barszcz and Bernadetta Kaźmierczak
Membranes 2020, 10(6), 133; https://doi.org/10.3390/membranes10060133 - 26 Jun 2020
Cited by 9 | Viewed by 2748
Abstract
Microfiltration (MF) membranes have been widely used for the separation and concentration of various components in food processing, biotechnology and wastewater treatment. The deposition of components from the feed solution and accumulation of bacteria on the surface and in the membrane matrix greatly [...] Read more.
Microfiltration (MF) membranes have been widely used for the separation and concentration of various components in food processing, biotechnology and wastewater treatment. The deposition of components from the feed solution and accumulation of bacteria on the surface and in the membrane matrix greatly reduce the effectiveness of MF. This is due to a decrease in the separation efficiency of the membrane, which contributes to a significant increase in operating costs and the cost of exploitative parts. In recent years, significant interest has arisen in the field of membrane modifications to make their surfaces resistant to the deposition of components from the feed solution and the accumulation of bacteria. The aim of this work was to develop appropriate process parameters for the plasma surface deposition of silver oxide (AgO) on MF polyamide membranes, which enables the fabrication of filtration materials with high permeability and antibacterial properties. Full article
(This article belongs to the Special Issue Membranes for Water Disinfection)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>SEM images of membranes with the AgO coatings deposited at different magnetron powers P<sub>M</sub>: (<bold>a</bold>) native membrane; (<bold>b</bold>) P<sub>M-Ag</sub> = 80 W, <italic>t</italic> = 30 s; (<bold>c</bold>) P<sub>M-Ag</sub> = 270 W, <italic>t</italic> = 30 s; (<bold>d</bold>) P<sub>M-Ag</sub> = 500 W, <italic>t</italic> = 30 s.</p> Full article ">Figure 2
<p>3D microscope images of the AgO coated membranes after filtration of bacterial suspensions.</p> Full article ">Figure 3
<p>Reduction (%) in viability of <italic>Escherichia coli</italic> and <italic>Bacillus subtilis</italic> on the native membrane and membranes covered with an AgO coating deposited within 30 s at different magnetron powers P<sub>M-Ag.</sub></p> Full article ">Figure 4
<p>Comparison of the photocatalytic properties of native membrane and membranes covered with an AgO coating deposited within 30 s at different magnetron powers P<sub>M-Ag</sub>.</p> Full article ">Figure 5
<p>The effect of changing the magnetron power in the deposition process of the AgO coating on the membrane surface on the permeate flux determined during filtration of demineralized water.</p> Full article ">Figure 6
<p>Concentrations of silver (Ag) ions in filtrate after the filtration process of demineralized water using membrane with the AgO coating (P<sub>M-Ag</sub> = 80 W).</p> Full article ">
20 pages, 2951 KiB  
Article
Metal Complex as a Novel Approach to Enhance the Amorphous Phase and Improve the EDLC Performance of Plasticized Proton Conducting Chitosan-Based Polymer Electrolyte
by Ahmad S. F. M. Asnawi, Shujahadeen B. Aziz, Muaffaq M. Nofal, Yuhanees M. Yusof, Iver Brevik, Muhamad H. Hamsan, Mohamad A. Brza, Rebar T. Abdulwahid and Mohd F. Z. Kadir
Membranes 2020, 10(6), 132; https://doi.org/10.3390/membranes10060132 - 25 Jun 2020
Cited by 53 | Viewed by 4010
Abstract
This work indicates that glycerolized chitosan-NH4F polymer electrolytes incorporated with zinc metal complexes are crucial for EDLC application. The ionic conductivity of the plasticized system was improved drastically from 9.52 × 10−4 S/cm to 1.71 × 10−3 S/cm with [...] Read more.
This work indicates that glycerolized chitosan-NH4F polymer electrolytes incorporated with zinc metal complexes are crucial for EDLC application. The ionic conductivity of the plasticized system was improved drastically from 9.52 × 10−4 S/cm to 1.71 × 10−3 S/cm with the addition of a zinc metal complex. The XRD results demonstrated that the amorphous phase was enhanced for the system containing the zinc metal complex. The transference number of ions (tion) and electrons (te) were measured for two of the highest conducting electrolyte systems. It confirmed that the ions were the dominant charge carriers in both systems as tion values for CSNHG4 and CSNHG5 electrolytes were 0.976 and 0.966, respectively. From the examination of LSV, zinc improved the electrolyte electrochemical stability to 2.25 V. The achieved specific capacitance from the CV plot reveals the role of the metal complex on storage properties. The charge–discharge profile was obtained for the system incorporated with the metal complex. The obtained specific capacitance ranged from 69.7 to 77.6 F/g. The energy and power densities became stable from 7.8 to 8.5 Wh/kg and 1041.7 to 248.2 W/kg, respectively, as the EDLC finalized the cycles. Full article
(This article belongs to the Special Issue Polymeric Membrane)
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Graphical abstract
Full article ">Figure 1
<p>XRD patterns for (<b>a</b>) CSNHG0, (<b>b</b>) CSNHG2, (<b>c</b>) CSNHG4 and (<b>d</b>) CSNHG5.</p> Full article ">Figure 1 Cont.
<p>XRD patterns for (<b>a</b>) CSNHG0, (<b>b</b>) CSNHG2, (<b>c</b>) CSNHG4 and (<b>d</b>) CSNHG5.</p> Full article ">Figure 2
<p>Impedance plots for (<b>a</b>) CSNHG0, (<b>b</b>) CSNHG1, (<b>c</b>) CSNHG2, (<b>d</b>) CSNHG3, (<b>e</b>) CSNHG4 and (<b>f</b>) CSNHG5.</p> Full article ">Figure 2 Cont.
<p>Impedance plots for (<b>a</b>) CSNHG0, (<b>b</b>) CSNHG1, (<b>c</b>) CSNHG2, (<b>d</b>) CSNHG3, (<b>e</b>) CSNHG4 and (<b>f</b>) CSNHG5.</p> Full article ">Figure 3
<p>Current versus time for the (<b>a</b>) CSNHG4 electrolyte and (<b>b</b>) CSNHG5 electrolyte.</p> Full article ">Figure 4
<p>Linear sweep voltammetry (LSV) curve for the (<b>a</b>) CSNHG4 electrolyte and (<b>b</b>) CSNHG5 electrolyte.</p> Full article ">Figure 5
<p>CV curves of the fabricated EDLC using (<b>a</b>) CSNHG4 and (<b>b</b>) CSNHG5 electrolyte at different scan rates.</p> Full article ">Figure 6
<p>Charge–discharge profile for the fabricated EDLC at initial cycles.</p> Full article ">Figure 7
<p>Specific capacitance (<span class="html-italic">C<sub>s</sub></span>) of the fabricated EDLC for 100 cycles.</p> Full article ">Figure 8
<p>The plot of (<b>a</b>) efficiency, and (<b>b</b>) ESR of the fabricated EDLC for 100 cycles.</p> Full article ">Figure 9
<p>Energy density and power density of the fabricated EDLC for 100 cycles.</p> Full article ">
56 pages, 600 KiB  
Review
Membrane-Based Processes Used in Municipal Wastewater Treatment for Water Reuse: State-Of-The-Art and Performance Analysis
by Jiaqi Yang, Mathias Monnot, Lionel Ercolei and Philippe Moulin
Membranes 2020, 10(6), 131; https://doi.org/10.3390/membranes10060131 - 25 Jun 2020
Cited by 73 | Viewed by 9086
Abstract
Wastewater reuse as a sustainable, reliable and energy recovery concept is a promising approach to alleviate worldwide water scarcity. However, the water reuse market needs to be developed with long-term efforts because only less than 4% of the total wastewater worldwide has been [...] Read more.
Wastewater reuse as a sustainable, reliable and energy recovery concept is a promising approach to alleviate worldwide water scarcity. However, the water reuse market needs to be developed with long-term efforts because only less than 4% of the total wastewater worldwide has been treated for water reuse at present. In addition, the reclaimed water should fulfill the criteria of health safety, appearance, environmental acceptance and economic feasibility based on their local water reuse guidelines. Moreover, municipal wastewater as an alternative water resource for non-potable or potable reuse, has been widely treated by various membrane-based treatment processes for reuse applications. By collecting lab-scale and pilot-scale reuse cases as much as possible, this review aims to provide a comprehensive summary of the membrane-based treatment processes, mainly focused on the hydraulic filtration performance, contaminants removal capacity, reuse purpose, fouling resistance potential, resource recovery and energy consumption. The advances and limitations of different membrane-based processes alone or coupled with other possible processes such as disinfection processes and advanced oxidation processes, are also highlighted. Challenges still facing membrane-based technologies for water reuse applications, including institutional barriers, financial allocation and public perception, are stated as areas in need of further research and development. Full article
(This article belongs to the Special Issue Membranes for Water Disinfection)
18 pages, 5520 KiB  
Article
Effect of Vitamin K3 Inhibiting the Function of NorA Efflux Pump and Its Gene Expression on Staphylococcus aureus
by Saulo R. Tintino, Veruska C. A. de Souza, Julia M. A. da Silva, Cícera Datiane de M. Oliveira-Tintino, Pedro S. Pereira, Tereza C. Leal-Balbino, Antonio Pereira-Neves, José P. Siqueira-Junior, José G. M. da Costa, Fabíola F. G. Rodrigues, Irwin R. A. Menezes, Gabriel C. A. da Hora, Maria C. P. Lima, Henrique D. M. Coutinho and Valdir Q. Balbino
Membranes 2020, 10(6), 130; https://doi.org/10.3390/membranes10060130 - 25 Jun 2020
Cited by 35 | Viewed by 3975
Abstract
Resistance to antibiotics has made diseases that previously healed easily become more difficult to treat. Staphylococcus aureus is an important cause of hospital-acquired infections and multi-drug resistant. NorA efflux pump, present in bacteria S. aureus, is synthesized by the expression of the [...] Read more.
Resistance to antibiotics has made diseases that previously healed easily become more difficult to treat. Staphylococcus aureus is an important cause of hospital-acquired infections and multi-drug resistant. NorA efflux pump, present in bacteria S. aureus, is synthesized by the expression of the norA gene. Menadione, also known as vitamin K3, is one of the synthetic forms of vitamin K. Therefore, the aim of this study is to verify the menadione effect on efflux inhibition through NorA pump gene expression inhibition and assess the effects of menadione in bacterial membrane. The effect of menadione as an efflux pump inhibitor (EPI) was evaluated by the microdilution method, fluorimetry, electron microscopy, and by RT-qPCR to evaluate gene expression. In the molecular docking, association with menadione induces increased fluorescence intensity. Menadione was observed (100% of the clusters) interacting with residues ILE12, ILE15, PHE16, ILE19, PHE47, GLN51, ALA105, and MET109 from NorA. The results showed the norA gene had its expression significantly diminished in the presence of menadione. The simulation showed that several menadione molecules were able to go through the bilayer and allow the entry of water molecules into the hydrophobic regions of the bilayer. When present within membranes, menadione may have caused membrane structural changes resulting in a decline of the signaling pathways involved in norA expression. Menadione demonstrated to be an efflux pump inhibitor with dual mechanism: affecting the efflux pump by direct interaction with protein NorA and indirectly inhibiting the norA gene expression, possibly by affecting regulators present in the membrane altered by menadione. Full article
(This article belongs to the Special Issue Dynamics and Nano-Organization in Plasma Membranes)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Synergistic effect of menadione on the ethidium bromide against the strain of <span class="html-italic">S. aureus</span> 1199B. Geometric mean ± standard error of the mean, with <span class="html-italic">t</span>-Test. a4: <span class="html-italic">p</span> &lt; 0.0001 vs. control of ethidium bromide.</p> Full article ">Figure 2
<p>Inhibition of efflux pump by increasing fluorescence. 1—Peak corresponding to the other bacterial constituents. 2—Peak corresponding to ethidium bromide. Inhibition of efflux pump by increasing fluorescence. Carbonyl Cyanide m-Chlorophenylhydrazine (CCCP).</p> Full article ">Figure 3
<p>Molecular docking of the structural model for the complex menadione-nora. (<b>A</b>) Overall structure of NorA obtained through homology modeling, with the position of Menadione inside of the transmembrane channel. (<b>B</b>) Detail of the lowest energy conformation and most populated conformational cluster obtained from the molecular docking calculations. Menadione is interacting with the closer residues ILE12, ILE15, PHE16, ILE19, PHE47, GLN51, ALA105, and MET109. Ligand is represented in cyan. Receptor molecule is represented in yellow, while the residues closest to the ligand are represented in gray. Hydrogen, oxygen, nitrogen and sulfur are represented in white, red, blue and yellow, respectively.</p> Full article ">Figure 4
<p>Relative <span class="html-italic">norA</span> gene expression in <span class="html-italic">S. aureus</span> 1199B in the presence of menadione associated with norfloxacin in comparison to the growth control: (<b>A</b>) comparison between growth control and association; (<b>B</b>) comparison between growth control and norfloxacin alone.</p> Full article ">Figure 5
<p>Transmission electron microscopy of <span class="html-italic">S. aureus</span> grown under culture medium. (<b>A</b>) General view showing rounded cells with a thick cell wall envelope and homogeneous electron density in the cytoplasm. Central division septa (*) are seen in some cells. (<b>B</b>,<b>C</b>) Detailed view of non-dividing (<b>B</b>) and dividing (<b>C</b>) bacteria A tripartite cell wall (CW) is seen enclosing the plasma membrane. Asterisk indicates the septum. (<b>D</b>) Inset of the cell wall. Black arrowhead indicates outer highly stained fibrous surface and intermediate translucent region; Arrow points to a heavily stained inner thin zone; the plasma membrane (white arrowhead) is seen immediately below this electrodense layer of the wall. Bars: A: 500 nm; B,C: 200 nm; D: 100 nm.</p> Full article ">Figure 6
<p>Transmission electron microscopy of <span class="html-italic">S. aureus</span> treated with antibiotics (Norfloxacin MIC/4): (<b>A</b>) General view: the cells are round and intact, with a well-defined cell wall. Division septa (*) are seen in some cells. (<b>B</b>,<b>C</b>) Detailed view of dividing (<b>B</b>) and non-dividing (<b>C</b>) bacteria showing the tripartite cell wall (CW). Asterisks indicate cell wall septa. (<b>D</b>) Inset of the cell wall. Black arrowhead, outer highly stained fibrous surface and intermediate translucent region; Arrow, heavily stained inner thin zone; white arrowhead, plasma membrane. Bars: A: 500 nm; B,C: 200 nm; D: 100 nm.</p> Full article ">Figure 7
<p>Transmission electron microscopy of <span class="html-italic">S. aureus</span> treated with antibiotics (Menadione MIC/4). (<b>A</b>) General view: some cells display altered cell wall without a tripartite-layers structure (black arrowheads). (<b>B</b>) Detailed view: the cell has no visible electron-dense inner thin zone of the cell wall (black arrowhead). White arrowhead indicates the plasma membrane. (<b>C</b>) Left cell display the normal tripartite cell wall with a heavily stained inner thin zone (arrow), whereas this electron-dense layer is not seen on the right cell (black arrowhead). (<b>D</b>) Inset of the Figure C. White arrowhead, plasma membrane. Bars: A: 500 nm; B,C: 200 nm; D: 100 nm.</p> Full article ">Figure 8
<p>Transmission electron microscopy of <span class="html-italic">S. aureus</span> treated with antibiotics (Menadione MIC/4) and Antibiotic CIM/4). (<b>A</b>) General view: some cells exhibit abnormal electron density in the cytoplasm (★) and altered cell wall with no visible tripartite-layers structure (black arrowheads). (<b>B</b>) Inset of Figure A. (<b>C</b>) Detailed view of a cell showing alterations in the shape, loss of cytosolic electron-density (★) and mesosome-like structures (M). (<b>D</b>) A lysed cell with cell wall disruption (arrow) and cytoplasmic disintegration (asterisk). Bars: A: 500 nm; B–D: 200 nm.</p> Full article ">Figure 8 Cont.
<p>Transmission electron microscopy of <span class="html-italic">S. aureus</span> treated with antibiotics (Menadione MIC/4) and Antibiotic CIM/4). (<b>A</b>) General view: some cells exhibit abnormal electron density in the cytoplasm (★) and altered cell wall with no visible tripartite-layers structure (black arrowheads). (<b>B</b>) Inset of Figure A. (<b>C</b>) Detailed view of a cell showing alterations in the shape, loss of cytosolic electron-density (★) and mesosome-like structures (M). (<b>D</b>) A lysed cell with cell wall disruption (arrow) and cytoplasmic disintegration (asterisk). Bars: A: 500 nm; B–D: 200 nm.</p> Full article ">Figure 9
<p>Average density profiles and snapshots conformations for the beginning and the end of menadione with POPG bilayer simulation. Initially (<b>A</b>,<b>C</b>) The menadione molecules (orange) were distributed above the membrane (grey). In the end (<b>B</b>,<b>D</b>), several went through the membrane and allowed the entry of water molecules (blue spheres) in the hydrophobic regions. The density curves shown are: water (blue lines), phosphate groups (red), glycerol groups (green), acyl chains (black dots), and menadione molecules (black circles).</p> Full article ">Figure 10
<p>Degree of lipid reorientation and overall disorder in the bilayer. (<b>A</b>) Deuterium order parameter S<sub>CD</sub> values were calculated for acyl chains sn1 (black) and sn2 (red). The filled circles and squares represents the order at the first 10 ns of simulation, while the empty circles and squares are the values for the last 10 ns; (<b>B</b>) Frequency distribution of the tilt angle of the lipid with the respect to the normal axis to the bilayer. The orientation values (0° = parallel to the <span class="html-italic">z</span> axis; 90° = perpendicular to the <span class="html-italic">z</span> axis) were also averaged for the initial 10 ns (black) and the final 10 ns (red).</p> Full article ">
17 pages, 18670 KiB  
Article
Diffusion Dialysis for Separation of Hydrochloric Acid, Iron and Zinc Ions from Highly Concentrated Pickling Solutions
by Rosa Gueccia, Alba Ruiz Aguirre, Serena Randazzo, Andrea Cipollina and Giorgio Micale
Membranes 2020, 10(6), 129; https://doi.org/10.3390/membranes10060129 - 24 Jun 2020
Cited by 29 | Viewed by 5542
Abstract
Acid recovery from pickling waste solutions is an important step to enhance hot-dip-galvanizing industry process sustainability. Diffusion dialysis (DD) can be used to separate acids and heavy metals (e.g., iron and zinc) from pickling waters, promoting the circular use of such raw materials. [...] Read more.
Acid recovery from pickling waste solutions is an important step to enhance hot-dip-galvanizing industry process sustainability. Diffusion dialysis (DD) can be used to separate acids and heavy metals (e.g., iron and zinc) from pickling waters, promoting the circular use of such raw materials. In the present study, a laboratory scale unit operating in batch and a continuous large scale unit, both equipped with Fumasep anionic exchange membranes, were tested. Results obtained show that zinc and iron concentration affect the HCl recovery in opposite ways. Iron chlorides enhance acid recovery, while zinc chlorides considerably tend to diffuse through the membrane because of negatively charged chloro-complexes formation and slightly reduce the acid diffusion. A multi-components mathematical model, with a time-dependent and distributed-parameters architecture, was adopted enabling the prediction of operations with hydrochloric acid, zinc, and iron metals both in batch and in continuous dialyzers. As a result, a good comparison between model simulations and experiments was achieved in both configurations. Full article
(This article belongs to the Special Issue Membrane Technologies for Resource Recovery)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Sketch of the batch (on the left) and continuous (on the right) experimental systems. (a) balances, (b) peristaltic pumps, (c) Diffusion Dialysis units, (r) retentate buffer, (d) diffusate buffer, (f) feed tank, (w) deionized water tank, (P) pressure meter. The arrows denote the osmotic flux (<span class="html-italic">J<sub>os</sub></span>), the drag flux (<span class="html-italic">J<sub>dr</sub></span>) and the <span class="html-italic">i</span>-component flux (<span class="html-italic">J<sub>i</sub></span>) across the membrane.</p> Full article ">Figure 2
<p>(<b>a</b>) ZnCl<sub>2</sub> leakage percentage and (<b>b</b>) HCl Recovery Ratio vs. initial Zn concentration in the retentate: 0 (<span class="html-fig-inline" id="membranes-10-00129-i001"> <img alt="Membranes 10 00129 i001" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i001.png"/></span>) 5 (<span class="html-fig-inline" id="membranes-10-00129-i002"> <img alt="Membranes 10 00129 i002" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i002.png"/></span>), 10 (<span class="html-fig-inline" id="membranes-10-00129-i003"> <img alt="Membranes 10 00129 i003" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i003.png"/></span>) and 20 g/L (<span class="html-fig-inline" id="membranes-10-00129-i004"> <img alt="Membranes 10 00129 i004" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i004.png"/></span>). Initial acid concentration: 3.6 g/L (0.1 mol/L) (empty symbols) and 73 g/L (2 mol/L) (solid symbols). Solutions flow rate fixed at 48 mL/min. Feed solution: HCl + ZnCl<sub>2</sub>. Inlet diffusate: 3.6 g/L (0.1 mol/L) HCl solution (empty symbols) and deionized water (solid symbol). Batch experimental-set-up.</p> Full article ">Figure 3
<p>Trend over time of the retentate tank volume. Initial Zn conc.: 0 (<span class="html-fig-inline" id="membranes-10-00129-i005"> <img alt="Membranes 10 00129 i005" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i005.png"/></span>); 5 (<span class="html-fig-inline" id="membranes-10-00129-i006"> <img alt="Membranes 10 00129 i006" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i006.png"/></span>), 10 (<span class="html-fig-inline" id="membranes-10-00129-i007"> <img alt="Membranes 10 00129 i007" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i007.png"/></span>) and 20 (<span class="html-fig-inline" id="membranes-10-00129-i008"> <img alt="Membranes 10 00129 i008" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i008.png"/></span>) g/L. Initial HCl concentration: 73 g/L (2 mol/L). Solutions flow rate fixed at 48 mL/min. Feed solution: HCl + ZnCl<sub>2</sub>. Inlet diffusate: deionized water. Batch experimental-set-up.</p> Full article ">Figure 4
<p>Temporal trend of HCl concentration (<b>a</b>), Zinc concentration (<b>b</b>) and Iron concentration (<b>c</b>) in the diffusate. Initial Zn concentrations: 0 (<span class="html-fig-inline" id="membranes-10-00129-i009"> <img alt="Membranes 10 00129 i009" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i009.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i010"> <img alt="Membranes 10 00129 i010" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i010.png"/></span>) and 10 (<span class="html-fig-inline" id="membranes-10-00129-i011"> <img alt="Membranes 10 00129 i011" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i011.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i012"> <img alt="Membranes 10 00129 i012" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i012.png"/></span>) g/L. Initial Fe conc.: 0 (<span class="html-fig-inline" id="membranes-10-00129-i013"> <img alt="Membranes 10 00129 i013" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i013.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i014"> <img alt="Membranes 10 00129 i014" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i014.png"/></span>); 100 (<span class="html-fig-inline" id="membranes-10-00129-i015"> <img alt="Membranes 10 00129 i015" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i015.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i016"> <img alt="Membranes 10 00129 i016" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i016.png"/></span>) g/L. Initial acid conc.: 73 g/L (2 mol/L). Solutions flow rate fixed at 48 mL/min. Feed solution: HCl + FeCl<sub>2</sub> + ZnCl<sub>2</sub>. Inlet diffusate: deionized water. Batch experimental-set-up.</p> Full article ">Figure 5
<p>Model calibration results in terms of variation of the zinc diffusive permeability (<b>a</b>)<b>,</b> additional Zn mass coefficient (<b>b</b>) and additional HCl mass coefficient (<b>c</b>) as a function of Zn concentration in the feed compartment.</p> Full article ">Figure 6
<p>HCl concentration in diffusate (<b>a</b>), diffusate volume (<b>b</b>), Fe concentration in retentate (<b>c</b>) and Zn concentration in retentate (<b>d</b>) vs. time. Initial Zn concentrations: 5 (<span class="html-fig-inline" id="membranes-10-00129-i017"> <img alt="Membranes 10 00129 i017" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i017.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i018"> <img alt="Membranes 10 00129 i018" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i018.png"/></span>) and 10 (<span class="html-fig-inline" id="membranes-10-00129-i019"> <img alt="Membranes 10 00129 i019" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i019.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i020"> <img alt="Membranes 10 00129 i020" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i020.png"/></span>) g/L. Initial Fe concentrations: 100 (<span class="html-fig-inline" id="membranes-10-00129-i021"> <img alt="Membranes 10 00129 i021" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i021.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i022"> <img alt="Membranes 10 00129 i022" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i022.png"/></span>) and 150 (<span class="html-fig-inline" id="membranes-10-00129-i023"> <img alt="Membranes 10 00129 i023" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i023.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i024"> <img alt="Membranes 10 00129 i024" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i024.png"/></span>) g/L. Initial acid concentrations: 73 g/L (2 mol/L). Flow rate: 48 mL/min. Feed: HCl, FeCl<sub>2</sub>, ZnCl<sub>2</sub> solution. Diffusate IN: deionized water. Theoretical curves (—) obtained by using the model.</p> Full article ">Figure 7
<p>Flow rate (<b>a</b>), HCl concentration (<b>b</b>), Fe concentration (<b>c</b>) and Zn concentration (<b>d</b>) vs. channel length for retentate (blue) and diffusate (red) for the continuous test 4 named in <a href="#membranes-10-00129-t002" class="html-table">Table 2</a>. Theoretical curves (—) obtained by using the model. Experimental data (dots).</p> Full article ">Figure 8
<p>Parity plots of all experimental (exp) and predicted (mod) values. (<b>a</b>)&amp;(<b>b</b>) species concentration and tanks volumes in retentate and diffusate compartments for tests with initial HCl at 73 g/L (2 mol/L), Zn at 5 (<span class="html-fig-inline" id="membranes-10-00129-i025"> <img alt="Membranes 10 00129 i025" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i025.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i026"> <img alt="Membranes 10 00129 i026" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i026.png"/></span>) and 10 (<span class="html-fig-inline" id="membranes-10-00129-i027"> <img alt="Membranes 10 00129 i027" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i027.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i028"> <img alt="Membranes 10 00129 i028" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i028.png"/></span>) g/L, and Fe at 100 (<span class="html-fig-inline" id="membranes-10-00129-i029"> <img alt="Membranes 10 00129 i029" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i029.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i030"> <img alt="Membranes 10 00129 i030" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i030.png"/></span>) and 150 (<span class="html-fig-inline" id="membranes-10-00129-i031"> <img alt="Membranes 10 00129 i031" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i031.png"/></span>,<span class="html-fig-inline" id="membranes-10-00129-i032"> <img alt="Membranes 10 00129 i032" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i032.png"/></span>) g/L. (<b>c</b>)&amp;(<b>d</b>) species concentration and flow rates in retentate and diffusate streams for tests 1 (<span class="html-fig-inline" id="membranes-10-00129-i033"> <img alt="Membranes 10 00129 i033" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i033.png"/></span>) 2 (<span class="html-fig-inline" id="membranes-10-00129-i034"> <img alt="Membranes 10 00129 i034" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i034.png"/></span>), 3 (<span class="html-fig-inline" id="membranes-10-00129-i035"> <img alt="Membranes 10 00129 i035" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i035.png"/></span>), and 4 (<span class="html-fig-inline" id="membranes-10-00129-i036"> <img alt="Membranes 10 00129 i036" src="/membranes/membranes-10-00129/article_deploy/html/images/membranes-10-00129-i036.png"/></span>) named in <a href="#membranes-10-00129-t002" class="html-table">Table 2</a>.</p> Full article ">
24 pages, 14297 KiB  
Review
Solid-Contact Ion-Selective Electrodes: Response Mechanisms, Transducer Materials and Wearable Sensors
by Yan Lyu, Shiyu Gan, Yu Bao, Lijie Zhong, Jianan Xu, Wei Wang, Zhenbang Liu, Yingming Ma, Guifu Yang and Li Niu
Membranes 2020, 10(6), 128; https://doi.org/10.3390/membranes10060128 - 23 Jun 2020
Cited by 99 | Viewed by 10388
Abstract
Wearable sensors based on solid-contact ion-selective electrodes (SC-ISEs) are currently attracting intensive attention in monitoring human health conditions through real-time and non-invasive analysis of ions in biological fluids. SC-ISEs have gone through a revolution with improvements in potential stability and reproducibility. The introduction [...] Read more.
Wearable sensors based on solid-contact ion-selective electrodes (SC-ISEs) are currently attracting intensive attention in monitoring human health conditions through real-time and non-invasive analysis of ions in biological fluids. SC-ISEs have gone through a revolution with improvements in potential stability and reproducibility. The introduction of new transducing materials, the understanding of theoretical potentiometric responses, and wearable applications greatly facilitate SC-ISEs. We review recent advances in SC-ISEs including the response mechanism (redox capacitance and electric-double-layer capacitance mechanisms) and crucial solid transducer materials (conducting polymers, carbon and other nanomaterials) and applications in wearable sensors. At the end of the review we illustrate the existing challenges and prospects for future SC-ISEs. We expect this review to provide readers with a general picture of SC-ISEs and appeal to further establishing protocols for evaluating SC-ISEs and accelerating commercial wearable sensors for clinical diagnosis and family practice. Full article
(This article belongs to the Special Issue Advances in Artificial and Biological Membranes: Mechanisms of Ionic Sensitivity, Ion-Sensor Designs and Applications for Ions Measurement)
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Figure 1

Figure 1
<p>An overview from liquid-contact ion-selective electrodes (LC-ISEs) to solid-contact ISEs (SC-ISEs) for wearable sensors. (<b>A</b>) Classic LC-ISEs (e.g., pH meter) by a liquid-contact between internal solution and ion-selective membrane (ISM). (<b>B</b>) The structure of SC-ISEs by a solid-contact between solid ion-to-electron transducer layer and ISM. (<b>C</b>) An example of the SC-ISEs for wearable sensor applications [<a href="#B9-membranes-10-00128" class="html-bibr">9</a>].</p> Full article ">Figure 2
<p>Response mechanisms for the SC-ISEs. (<b>A</b>) Redox capacitance-based SC-ISEs with poly(3,4-ethylenedioxythiophene) (PEDOT) as an example for redox SC transducer. (<b>B</b>) Electric-double-layer (EDL) capacitance-based SC-ISEs with carbon as an example for EDL SC transducer. Both SC-ISEs contain three interfaces, GC/SC, SC/ISM and ISM/aq. GC: glass carbon electrode substrate; SC: solid contact; aq: aqueous solution; ET: electron transfer; IT: ion transfer. The corresponding phase interfacial potentials are presented on the right (detailed illustration shown in the main text and <a href="#app1-membranes-10-00128" class="html-app">Appendix A</a>).</p> Full article ">Figure 3
<p>Structural design and functionalization of conducting polymers (CPs) for CP-based SC-ISEs. (<b>A</b>) Scanning electronic microscopy (SEM) image of the designed high-surface 3D poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT(PSS)) by nanosphere lithography and electrosynthesis. The right: the potential traces of 3D PEDOT(PSS) functionalized with (red line) and without (black line) a lipophilic redox 1,1′-dimethylferrocene. It is found that the functionalized 3D PEDOT(PSS) exhibits much better reproducibility. Reprinted with permission from [<a href="#B24-membranes-10-00128" class="html-bibr">24</a>], Copyright (2016) John Wiley and Sons publications. (<b>B</b>) The oxidized PPy by doping perfluorooctanesulfonate (PFOS<sup>−</sup>) anion (PPy-PFOS) enhanced the hydrophobicity leading to remarkably improved reproducibility. Reprinted with permission from [<a href="#B25-membranes-10-00128" class="html-bibr">25</a>], Copyright (2017) American Chemical Society. (<b>C</b>) Superhydrophobic tetrakis-(pentafluorophenyl)borate (TPFPhB<sup>−</sup>) anion doping PEDOT as an SC transducer to reduce the water-layer effect. It should be noted the TPFPhB<sup>−</sup> ion transfer (ion exchange) between SC and ISM further enhanced the potential stability (see Equation (3)). The abbreviation of tetrakis-(pentafluorophenyl)borate on the original Figure is TFAB<sup>−</sup>. Herein it is replaced by TPFPhB<sup>−</sup>. Reprinted with permission from [<a href="#B26-membranes-10-00128" class="html-bibr">26</a>], Copyright (2019) American Chemical Society. (<b>D</b>) An ultimate approach by both C<sub>14</sub>-chain functionalized PEDOT and TPFPhB<sup>−</sup> doping to improve the performances of SC-ISEs. Reprinted with permission from [<a href="#B27-membranes-10-00128" class="html-bibr">27</a>], Copyright (2017) American Chemical Society.</p> Full article ">Figure 4
<p>Suppress of the leaking of ISM components. (<b>A</b>) A CP-based SC-ISE by coating the silicon rubber (SR) on the ISM layer. (<b>B</b>) A photograph of the SR on the poly(vinyl chloride) (PVC)-based ISM. (<b>C</b>) Fourier transform infrared (FTIR) spectra analysis of the SR layer (bottom and top) in comparison with standard ISM components. The ISM components were observed in both bottom and top SR (typical dioctyl sebacate, DOS). (<b>D</b>) The K<sup>+</sup>-response of SR-coated SC-ISEs compared with an uncoated one. Reprinted with permission from [<a href="#B49-membranes-10-00128" class="html-bibr">49</a>], Copyright (2019) American Chemical Society.</p> Full article ">Figure 5
<p>Carbon-based SC-ISEs. (<b>A</b>) High-surface 3D-ordered microporous (3DOM) carbon as a SC transducer for SC-ISEs. Reprinted with permission from [<a href="#B50-membranes-10-00128" class="html-bibr">50</a>], Copyright (2007) American Chemical Society. (<b>B</b>) Colloid-imprinted mesoporous (CIM) carbon with higher surface area as a SC transducer for SC-ISEs. Reprinted with permission from [<a href="#B52-membranes-10-00128" class="html-bibr">52</a>], Copyright (2014) American Chemical Society. (<b>C</b>) The porous carbon sub-micrometer spheres (PC-SMSs) for superhydrophobic SC transducer with the contact angle up to 137°. Reprinted with permission from [<a href="#B53-membranes-10-00128" class="html-bibr">53</a>], Copyright (2015) Elsevier. (<b>D</b>) Single-wall carbon nanotube (SWCNT)-based SC-ISEs and the illustrated EDL capacitance response mechanism. Reprinted with permission from [<a href="#B54-membranes-10-00128" class="html-bibr">54</a>], Copyright (2008) American Chemical Society. (<b>E</b>) The chemically prepared reduced graphene oxide (RGO) as SC transducer for SC-ISEs. Reprinted with permission from [<a href="#B55-membranes-10-00128" class="html-bibr">55</a>], Copyright (2012) Royal Society of Chemistry.</p> Full article ">Figure 6
<p>Au nanoclusters-based SC-ISEs. (<b>A</b>–<b>C</b>) Au<sub>144</sub> redox nanocluster based-SC-ISEs. (<b>A</b>) Reduced and oxidized states of thiol monolayer-protected Au clusters (MPCs) (Au<sub>144</sub>) doped with tetrakis(4-chlorophenyl) borate (TB<sup>−</sup>) anion (MPC<sup>0</sup>/MPC<sup>+</sup>TB<sup>−</sup>). (<b>B</b>) Au MPCs-based SC-ISEs with well-defined phase interfacial potential definition. (<b>C</b>) Water-layer test of Au<sub>144</sub>-based SC-ISEs. Reprinted with permission from [<a href="#B61-membranes-10-00128" class="html-bibr">61</a>], Copyright (2012) American Chemical Society. (<b>D</b>,<b>E</b>) Au<sub>25</sub> redox nanocluster based-SC-ISEs. (<b>D</b>) Transmission electronic image (TEM) of the Au<sub>25</sub> synthesized by optimized one-phase reduction procedure. (<b>E</b>) The Au<sub>25</sub>-based SC-ISEs for K<sup>+</sup>-response to examine its long-term stability. Reprinted with permission from [<a href="#B62-membranes-10-00128" class="html-bibr">62</a>], Copyright (2016) Elsevier. (<b>F</b>) Au MPCs-based single-piece SC-ISEs through mixing the SC and ISM phase. Reprinted with permission from [<a href="#B63-membranes-10-00128" class="html-bibr">63</a>], Copyright (2016) Elsevier.</p> Full article ">Figure 7
<p>A few other representative SC materials. (<b>A</b>) Co(II)/Co(III) complex redox buffer-based SC-ISEs. Reprinted with permission from [<a href="#B64-membranes-10-00128" class="html-bibr">64</a>], Copyright (2013) American Chemical Society. (<b>B</b>,<b>C</b>) Lithium-battery materials of LiFePO<sub>4/</sub>FePO<sub>4</sub>-based SC-ISEs. Reprinted with permission from [<a href="#B70-membranes-10-00128" class="html-bibr">70</a>], Copyright (2016) John Wiley and Sons publications. (<b>D</b>,<b>E</b>) MoS<sub>2</sub> nanomaterials was used for the EDL-type solid contact. SEM image of MoS<sub>2</sub> (<b>D</b>) and water layer test (<b>E</b>). Reprinted with permission from [<a href="#B71-membranes-10-00128" class="html-bibr">71</a>], Copyright (2016) Elsevier. (<b>F</b>) Metal–organic frameworks (MOFs)-based SC-ISEs. Reprinted with permission from [<a href="#B73-membranes-10-00128" class="html-bibr">73</a>], Copyright (2018) American Chemical Society.</p> Full article ">Figure 8
<p>CPs-based wearable SC-ISEs for skin sweat ion sensing. (<b>A</b>) An integrated multi-parameter electrochemical wearable sensor involving Na<sup>+</sup> and K<sup>+</sup>-SC-ISEs, glucose, lactate and temperature. The PEDOT was used for the SC transducer. Reprinted with permission from [<a href="#B75-membranes-10-00128" class="html-bibr">75</a>], Copyright (2016) Springer Nature. (<b>B</b>) PEDOT-based wearable SC-ISEs for pH and Ca<sup>2+</sup> sensors. Reprinted with permission from [<a href="#B76-membranes-10-00128" class="html-bibr">76</a>], Copyright (2016) American Chemical Society. (<b>C</b>–<b>E</b>) PEDOT-based self-healable SC-ISEs for wearable senor. Reprinted with permission from [<a href="#B77-membranes-10-00128" class="html-bibr">77</a>], Copyright (2019) American Chemical Society.</p> Full article ">Figure 9
<p>Carbon-based wearable SC-ISEs for skin sweat ion sensing. (<b>A</b>) SWCNT-based flexible SC-ISEs by using cotton yard as flexible substrate. Reprinted with permission from [<a href="#B78-membranes-10-00128" class="html-bibr">78</a>], Copyright (2013) Royal Society of Chemistry. A series of preparation including SWCNT ink and ISM dipping as shown in (<b>a</b>–<b>d</b>). (<b>B</b>) Multi-wall carbon nanotube (MWCNT) textile-based SC-ISEs for Na<sup>+</sup> and K<sup>+</sup> sensing. Reprinted with permission from [<a href="#B80-membranes-10-00128" class="html-bibr">80</a>], Copyright (2016) John Wiley and Sons publications. (<b>C</b>) Carbon textile-based sensor array for multiparameter analysis. Reprinted with permission from Science Advances [<a href="#B81-membranes-10-00128" class="html-bibr">81</a>], Copyright (2019) American Association for the Advancement of Science. (<b>D</b>) High-quality graphene-based wearable SC-ISEs for multichannel ion sensing including K<sup>+</sup>, Na<sup>+</sup>, Cl<sup>−</sup> and pH [<a href="#B82-membranes-10-00128" class="html-bibr">82</a>]. (<b>E</b>) The suggested protocol for on-body measurement. It should be noted that the importance of calibration of SC-ISEs to assure the accuracy of real-time analysis. Reprinted with permission from [<a href="#B83-membranes-10-00128" class="html-bibr">83</a>], Copyright (2019) American Chemical Society.</p> Full article ">Figure 10
<p>Au nanomaterials-based wearable SC-ISEs for skin sweat ion sensing. (<b>A</b>–<b>C</b>) AuND array-based SC-ISEs for sweat Na<sup>+</sup> sensing. (<b>A</b>) The preparation procedure for AuND-based SC-ISEs by photolithography technique. (<b>B</b>) A schematic for the SC-ISEs on-body measurement. (<b>C</b>) Real-time analysis of sweat Na<sup>+</sup> during cycling and rest states. Reprinted with permission from [<a href="#B84-membranes-10-00128" class="html-bibr">84</a>], Copyright (2017) American Chemical Society. (<b>D</b>,<b>E</b>) Gold-based vertically aligned nanowires (V-AuNWs)-based stretchable SC-ISEs for Na<sup>+</sup>, K<sup>+</sup> and pH sensing. (<b>D</b>) The preparation of V-AuNWs on PDMS film and corresponding optical images for observing the stretching. Scale bar: 200 μm. Reprinted with permission from [<a href="#B85-membranes-10-00128" class="html-bibr">85</a>], Copyright (2019) John Wiley and Sons publications. (<b>E</b>) The Na<sup>+</sup>, K<sup>+</sup> and pH sensing from 0% to 30% stretching. Reprinted with permission from [<a href="#B86-membranes-10-00128" class="html-bibr">86</a>], Copyright (2020) American Chemical Society.</p> Full article ">Figure 11
<p>Wearable SC-ISEs for ion detection in interstitial fluid. (<b>A</b>–<b>C</b>) Microneedle-based SC-ISEs for K<sup>+</sup> analysis in skin interstitial fluid. (<b>A</b>) Illustration of microneedle patch including working electrode (WE) and reference electrode (RE). For the WE, the bare microneedle was coated carbon, f-MWCNTs and K<sup>+</sup>-ISM. For the RE, the bare microneedle was coated Ag/AgCl; and poly(vinly butyral) membrane and polyurethane. (<b>B</b>) K<sup>+</sup> response before and after insertion into the animal skin. (<b>C</b>) Ex vivo K<sup>+</sup> measurement in chicken skin with calibration. Reprinted with permission from [<a href="#B88-membranes-10-00128" class="html-bibr">88</a>], Copyright (2019) American Chemical Society. (<b>D</b>,<b>E</b>) A cotton fiber-based SC-ISEs for Li<sup>+</sup> sensing in the human plasma. (<b>D</b>) A SEM image for the cotton-based SC-ISEs. (<b>E</b>) Li<sup>+</sup>-response in aqueous solution and human plasma. The inset shows the time traces for Li<sup>+</sup> response. Reprinted with permission from [<a href="#B89-membranes-10-00128" class="html-bibr">89</a>], Copyright (2018) American Chemical Society.</p> Full article ">
36 pages, 4275 KiB  
Article
Assessment of the Performance of Electrodialysis in the Removal of the Most Potent Odor-Active Compounds of Herring Milt Hydrolysate: Focus on Ion-Exchange Membrane Fouling and Water Dissociation as Limiting Process Conditions
by Sarah Todeschini, Véronique Perreault, Charles Goulet, Mélanie Bouchard, Pascal Dubé, Yvan Boutin and Laurent Bazinet
Membranes 2020, 10(6), 127; https://doi.org/10.3390/membranes10060127 - 20 Jun 2020
Cited by 11 | Viewed by 3218
Abstract
Herring milt hydrolysate (HMH), like many fish products, presents the drawback to be associated with off-flavors. As odor is an important criterion, an effective deodorization method targeting the volatile compounds responsible for off-flavors needs to be developed. The potential of electrodialysis (ED) to [...] Read more.
Herring milt hydrolysate (HMH), like many fish products, presents the drawback to be associated with off-flavors. As odor is an important criterion, an effective deodorization method targeting the volatile compounds responsible for off-flavors needs to be developed. The potential of electrodialysis (ED) to remove the 15 volatile compounds identified, in the first part of this work, for their main contribution to the odor of HMH, as well as trimethylamine, dimethylamine and trimethylamine oxide, was assessed by testing the impact of both hydrolysate pH (4 and 7) and current conditions (no current vs. current applied). The ED performance was compared with that of a deaerator by assessing three hydrolysate pH values (4, 7 and 10). The initial pH of HMH had a huge impact on the targeted compounds, while ED had no effect. The fouling formation, resulting from electrostatic and hydrophobic interactions between HMH constituents and ion-exchange membranes (IEM); the occurrence of water dissociation on IEM interfaces, due to the reaching of the limiting current density; and the presence of water dissociation catalyzers were considered as the major limiting process conditions. The deaerator treatment on hydrolysate at pH 7 and its alkalization until pH 10 led to the best removal of odorant compounds. Full article
(This article belongs to the Special Issue In-Depth on the Fouling and Antifouling of Ion-Exchange Membranes)
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<p>Electrodialysis cell configuration; V<sup>+</sup>: cationic volatile compounds, AEM: anion-exchange membrane, CEM: cation-exchange membrane.</p> Full article ">Figure 2
<p>pH evolution in HMH solutions at pH 4 and 7, and in the corresponding KCl recovery solutions treated with and without current during ED treatments of 240 min.</p> Full article ">Figure 3
<p>Conductivity evolution in HMH solutions at pH 4 and 7, and in the corresponding KCl recovery solutions, treated with and without current during ED treatments of 240 min.</p> Full article ">Figure 4
<p>Global system resistance evolution during ED treatments of 240 min at pH 4 and pH 7, with current.</p> Full article ">Figure 5
<p>Membrane thickness before and after each 4-h ED treatment conducted at pH 4, (<b>a</b>) without current and (<b>b</b>) with current. Values with different letters corresponding to the same membranes are significantly different <span class="html-italic">p</span> &lt; 0.05 (Tukey test).</p> Full article ">Figure 6
<p>Membrane thickness before and after each 4-h ED treatment conducted at pH 7, (<b>a</b>) without current and (<b>b</b>) with current. Values with different letters corresponding to the same membranes are significantly different, <span class="html-italic">p</span> &lt; 0.05 (Tukey test).</p> Full article ">Figure 7
<p>Membrane conductivity before and after each 4-h ED treatments conducted at pH 4, (<b>a</b>) without current and (<b>b</b>) with current. Values with different letters corresponding to the same membranes are significantly different <span class="html-italic">p</span> &lt; 0.05 (Tukey test).</p> Full article ">Figure 8
<p>Membrane conductivity before and after each 4-h ED treatments conducted at pH 7, (<b>a</b>) without current and (<b>b</b>) with current. Values with different letters corresponding to the same membranes are significantly different <span class="html-italic">p</span> &lt; 0.05 (Tukey test).</p> Full article ">
21 pages, 5458 KiB  
Article
Direct Measurement of Crossover and Interfacial Resistance of Ion-Exchange Membranes in All-Vanadium Redox Flow Batteries
by Yasser Ashraf Gandomi, Doug S. Aaron, Zachary B. Nolan, Arya Ahmadi and Matthew M. Mench
Membranes 2020, 10(6), 126; https://doi.org/10.3390/membranes10060126 - 18 Jun 2020
Cited by 13 | Viewed by 3917
Abstract
Among various components commonly used in redox flow batteries (RFBs), the separator plays a significant role, influencing resistance to current as well as capacity decay via unintended crossover. It is well-established that the ohmic overpotential is dominated by the membrane and interfacial resistance [...] Read more.
Among various components commonly used in redox flow batteries (RFBs), the separator plays a significant role, influencing resistance to current as well as capacity decay via unintended crossover. It is well-established that the ohmic overpotential is dominated by the membrane and interfacial resistance in most aqueous RFBs. The ultimate goal of engineering membranes is to improve the ionic conductivity while keeping crossover at a minimum. One of the major issues yet to be addressed is the contribution of interfacial phenomena in the influence of ionic and water transport through the membrane. In this work, we have utilized a novel experimental system capable of measuring the ionic crossover in real-time to quantify the permeability of ionic species. Specifically, we have focused on quantifying the contributions from the interfacial resistance to ionic crossover. The trade-off between the mass and ionic transport impedance caused by the interface of the membranes has been addressed. The MacMullin number has been quantified for a series of electrolyte configurations and a correlation between the ionic conductivity of the contacting electrolyte and the Nafion® membrane has been established. The performance of individual ion-exchange membranes along with a stack of various separators have been explored. We have found that utilizing a stack of membranes is significantly beneficial in reducing the electroactive species crossover in redox flow batteries compared to a single membrane of the same fold thickness. For example, we have demonstrated that the utilization of five layers of Nafion® 211 membrane reduces the crossover by 37% while only increasing the area-specific resistance (ASR) by 15% compared to a single layer Nafion® 115 membrane. Therefore, the influence of interfacial impedance in reducing the vanadium ion crossover is substantially higher compared to a corresponding increase in ASR, indicating that mass and ohmic interfacial resistances are dissimilar. We have expanded our analysis to a combination of commercially available ion-exchange membranes and provided a design chart for membrane selection based on the application of interest (short duration/high-performance vs. long-term durability). The results of this study provide a deeper insight into the optimization of all-vanadium redox flow batteries (VRFBs). Full article
(This article belongs to the Special Issue Development of Membranes in Battery and Membrane-Based Devices)
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Graphical abstract
Full article ">Figure 1
<p>Test configuration used for measuring concentration-gradient-induced crossover; the setup includes several flow cells (Cell 1, 2, and 3), electrolyte reservoirs, and UV/Vis spectroscopy apparatus including UV light source, spectrometer, and UV cell (Cell 4) [<a href="#B16-membranes-10-00126" class="html-bibr">16</a>].</p> Full article ">Figure 2
<p>Schematic of the device designed in-house for measuring: (<b>a</b>) in-plane ionic conductivity of ion-exchange membranes (IEMs), (<b>b</b>) ionic conductivity of electrolytes [<a href="#B27-membranes-10-00126" class="html-bibr">27</a>].</p> Full article ">Figure 3
<p>The area specific resistance (ASR) for all-vanadium redox flow batteries (VRFBs) assembled with multi-layer configurations of Nafion<sup>®</sup> 115 (Note: The ASR values were corrected for the values without membrane).</p> Full article ">Figure 4
<p>In-plane ionic conductivity of Nafion<sup>®</sup> 115 equilibrated in different electrolytes.</p> Full article ">Figure 5
<p>The ionic conductivity measured for various electrolytes.</p> Full article ">Figure 6
<p>The ASR value for single-layer N115 and predicted ASR variation as a function of membrane thickness.</p> Full article ">Figure 7
<p>Concentration of the vanadium in the vanadium-deficient electrolyte at the end of the experiment for a cell with single-layer N115 membrane along with predicted vanadium crossover based on Fickian diffusion behavior.</p> Full article ">Figure 8
<p>UV/Vis spectrum of vanadium-deficient electrolyte during crossover test for series of ion-exchange membranes (N115).</p> Full article ">Figure 9
<p>Electrochemical impedance spectroscopy for series of IEMs, (<b>a</b>) The spectra prior (contacting electrolyte at both sides: aqueous electrolyte with 3.3 M of H<sub>2</sub>SO<sub>4</sub>), during (vanadium-deficient and enriched electrolyte in different sides as described in the text), and after crossover measurement (contacting electrolyte: aqueous electrolyte with 1.5 M of V(IV), and 3.3 M of H<sub>2</sub>SO<sub>4</sub> at both sides); (<b>b</b>) Spectra at high-frequency region.</p> Full article ">Figure 10
<p>Comparison of ASR for multilayers of NR211 with a single layer N115 Nafion<sup>®</sup> membrane during crossover measurement.</p> Full article ">Figure 11
<p>Comparison of concentration-gradient-induced crossover between 5 layers of NR211 and 1 layer of N115.</p> Full article ">Figure 12
<p>Schematic illustration of proposed reduction of ionic crossover for multilayers of IEMs, (<b>a</b>) 1 layer of N115, (<b>b</b>) 5 layers of NR211.</p> Full article ">Figure 13
<p>IEM selection chart for reducing ionic crossover in VRFBs. Dashed line represents an exponential fit to the experimentally measured vanadium ion (V(IV)) crossover data associated with the cells with single-layer Nafion<sup>®</sup> membrane. The large white arrows demonstrate the improvement in capacity retention with multilayer thinner IEMs for different scenarios including high-performance operation as well as short- and long-duration cycling.</p> Full article ">
21 pages, 5836 KiB  
Article
The Development of Electroconvection at the Surface of a Heterogeneous Cation-Exchange Membrane Modified with Perfluorosulfonic Acid Polymer Film Containing Titanium Oxide
by Violetta Gil, Mikhail Porozhnyy, Olesya Rybalkina, Dmitrii Butylskii and Natalia Pismenskaya
Membranes 2020, 10(6), 125; https://doi.org/10.3390/membranes10060125 - 17 Jun 2020
Cited by 12 | Viewed by 2585
Abstract
One way to enhance mass transfer and reduce fouling in wastewater electrodialysis is stimulation of electroconvective mixing of the solution adjoining membranes by modifying their surfaces. Several samples were prepared by casting the perfluorosulfonic acid (PFSA) polymer film doped with TiO2 nanoparticles [...] Read more.
One way to enhance mass transfer and reduce fouling in wastewater electrodialysis is stimulation of electroconvective mixing of the solution adjoining membranes by modifying their surfaces. Several samples were prepared by casting the perfluorosulfonic acid (PFSA) polymer film doped with TiO2 nanoparticles onto the surface of the heterogeneous cation-exchange membrane MK-40. It is found that changes in surface characteristics conditioned by such modification lead to an increase in the limiting current density due to the stimulation of electroconvection, which develops according to the mechanism of electroosmosis of the first kind. The greatest increase in the current compared to the pristine membrane can be obtained by modification with the film being 20 μm thick and containing 3 wt% of TiO2. The sample containing 6 wt% of TiO2 provides higher mass transfer in overlimiting current modes due to the development of nonequilibrium electroconvection. A 1.5-fold increase in the thickness of the modifying film reduces the positive effect of introducing TiO2 nanoparticles due to (1) partial shielding of the nanoparticles on the surface of the modified membrane; (2) a decrease in the tangential component of the electric force, which affects the development of electroconvection. Full article
(This article belongs to the Special Issue In-Depth on the Fouling and Antifouling of Ion-Exchange Membranes)
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<p>Principal scheme of the experimental setup: electrodialysis cell (1) consisting of one desalination compartment (DC), one concentration compartment (CC) and two electrode compartments; tanks with solutions (2, 3); Luggin’s capillaries (4), connected with silver chloride electrodes (5); electrochemical complex Autolab PGSTAT-100 (6); flow pass cell with pH combination electrode (7), connected to pH-meter Expert 001 (8).</p> Full article ">Figure 2
<p>Optical images of the studied membranes: MK-40 (<b>a</b>), MK-40<sub>21</sub> (<b>b</b>), MK-40<sub>21+3%</sub> (<b>c</b>), MK-40<sub>21+6%</sub> (<b>d</b>), MK-40<sub>33+3%</sub> (<b>e</b>), MK-40<sub>33+6%</sub> (<b>f</b>). Parameter <span class="html-italic">b</span> characterizes the roughness of the surface and shows the difference between the highest and lowest areas of the membrane relief.</p> Full article ">Figure 3
<p>Concentration dependences of the conterion (Na<sup>+</sup>) transport number in the studied membranes.</p> Full article ">Figure 4
<p>Current-voltage characteristics (solid lines) and the difference in pH between the outlet and inlet solution passing through the desalination compartment of the electrodialysis cell (dashed lines) of the pristine and modified membranes.</p> Full article ">Figure 5
<p>Schematic representation of streamlines near the surface of the MK-40 (<b>a</b>) membrane and that, modified by PFSA polymer film of various thicknesses: about 20 μm (<b>b</b>) and about 30 μm (<b>c</b>).</p> Full article ">Figure 6
<p>Chronopotentiometric curves of the studied membranes measured at <math display="inline"><semantics> <mrow> <mi>i</mi> <mo>/</mo> <msubsup> <mi>i</mi> <mrow> <mi>lim</mi> </mrow> <mrow> <mi>th</mi> </mrow> </msubsup> </mrow> </semantics></math>= 2. The circles show the inflection points related to <span class="html-italic">τ<sub>exp.</sub></span></p> Full article ">Figure 7
<p>Electrochemical impedance spectra of the MK-40 as well as MK-40<sub>21</sub>, MK-40<sub>21+3%</sub>, MK-40<sub>21+6%</sub> (<b>a</b>) and MK-40<sub>33+3%</sub>, MK-40<sub>33+6%</sub> (<b>b</b>) samples at <math display="inline"><semantics> <mrow> <mi>i</mi> <mo>/</mo> <msubsup> <mi>i</mi> <mrow> <mi>lim</mi> </mrow> <mrow> <mi>th</mi> </mrow> </msubsup> </mrow> </semantics></math> = 1.5.</p> Full article ">Figure 8
<p>Electrochemical impedance spectra of the MK-40 as well as MK-40<sub>21</sub>, MK-40<sub>21+3%</sub>, MK-40<sub>21+6%</sub> (<b>a</b>) and MK-40<sub>33+3%</sub>, MK-40<sub>33+6%</sub> (<b>b</b>) samples at <math display="inline"><semantics> <mrow> <mi>i</mi> <mo>/</mo> <msubsup> <mi>i</mi> <mrow> <mi>lim</mi> </mrow> <mrow> <mi>th</mi> </mrow> </msubsup> </mrow> </semantics></math> = 1.8.</p> Full article ">
18 pages, 7726 KiB  
Article
ZrO2-TiO2 Incorporated PVDF Dual-Layer Hollow Fiber Membrane for Oily Wastewater Treatment: Effect of Air Gap
by Nurshahnawal Yaacob, Pei Sean Goh, Ahmad Fauzi Ismail, Noor Aina Mohd Nazri, Be Cheer Ng, Muhammad Nizam Zainal Abidin and Lukka Thuyavan Yogarathinam
Membranes 2020, 10(6), 124; https://doi.org/10.3390/membranes10060124 - 16 Jun 2020
Cited by 24 | Viewed by 5094
Abstract
Dual-layer hollow fiber (DLHF) nanocomposite membrane prepared by co-extrusion technique allows a uniform distribution of nanoparticles within the membrane outer layer to enhance the membrane performance. The effects of spinning parameters especially the air gap on the physico-chemical properties of ZrO2-TiO [...] Read more.
Dual-layer hollow fiber (DLHF) nanocomposite membrane prepared by co-extrusion technique allows a uniform distribution of nanoparticles within the membrane outer layer to enhance the membrane performance. The effects of spinning parameters especially the air gap on the physico-chemical properties of ZrO2-TiO2 nanoparticles incorporated PVDF DLHF membranes for oily wastewater treatment have been investigated in this study. The zeta potential of the nanoparticles was measured to be around –16.5 mV. FESEM–EDX verified the uniform distribution of Ti, Zr, and O elements throughout the nanoparticle sample and the TEM images showed an average nanoparticles grain size of ~12 nm. Meanwhile, the size distribution intensity was around 716 nm. A lower air gap was found to suppress the macrovoid growth which resulted in the formation of thin outer layer incorporated with nanoparticles. The improvement in the separation performance of PVDF DLHF membranes embedded with ZrO2-TiO2 nanoparticles by about 5.7% in comparison to the neat membrane disclosed that the incorporation of ZrO2-TiO2 nanoparticles make them potentially useful for oily wastewater treatment. Full article
(This article belongs to the Special Issue Organic–Inorganic Hybrid Membranes for Separation and Purification Applications)
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<p>Schematic diagram of the dual-layer hollow fiber (DLHF) membrane structure with ZrO<sub>2</sub>-TiO<sub>2</sub> embedded polyvinylidene fluoride (PVDF) outer layer and PVDF inner layer.</p> Full article ">Figure 2
<p>Zeta potential of ZrO<sub>2</sub>-TiO<sub>2</sub> nanoparticles with inset showing the deconvolution of two peaks.</p> Full article ">Figure 3
<p>Transmission electron microscopy (TEM) images of ZrO<sub>2</sub>-TiO<sub>2</sub> nanoparticles. (<b>a</b>) TiO<sub>2</sub> crystal spacing with inset shows the peaks and the percentage of elemental composition and (<b>b</b>) Small agglomeration and dispersion of nanoparticles.</p> Full article ">Figure 4
<p>Distribution of ZrO<sub>2</sub>-TiO<sub>2</sub> nanoparticles</p> Full article ">Figure 5
<p>The overall (×100 magnification) structure of DLHF membranes spun at air gap of 5 cm for (<b>a</b>) DL-ZT0 and (<b>b</b>) DL-ZT1.</p> Full article ">Figure 6
<p>The cross-section (×300 magnification) structure of DL-ZT0 membranes spun at different air gap of (<b>a</b>) 5 cm, (<b>b</b>) 10 cm, (<b>c</b>) 20 cm, (<b>d</b>) 30 cm, (<b>e</b>) 40 cm, and (<b>f</b>) 50 cm.</p> Full article ">Figure 7
<p>The cross-section (×300 magnification) structure of DL-ZT1 membranes spun at different air gap of (<b>a</b>) 5 cm, (<b>b</b>) 10 cm, (<b>c</b>) 20 cm, (<b>d</b>) 30 cm, (<b>e</b>) 40 cm, and (<b>f</b>) 50 cm.</p> Full article ">Figure 8
<p>Schematic illustration of the effect of air gap on DLHF membrane structure.</p> Full article ">Figure 9
<p>Contact angle measurement with increasing air gap length.</p> Full article ">Figure 10
<p>Effect of air gap on flux and oil rejection.</p> Full article ">
16 pages, 4314 KiB  
Article
Analysis for Reverse Temperature Dependence of Hydrogen Permeability through Pd-X (X = Y, Ho, Ni) Alloy Membranes Based on Hydrogen Chemical Potential
by Asuka Suzuki and Hiroshi Yukawa
Membranes 2020, 10(6), 123; https://doi.org/10.3390/membranes10060123 - 16 Jun 2020
Cited by 9 | Viewed by 3010
Abstract
It is generally understood that the hydrogen permeability of Pd-Ag alloy membranes declines with decreasing temperature. However, recent studies have revealed that the hydrogen permeability of Pd-Ag alloy membranes inversely increases at a certain temperature range and reaches a peak. The peak behavior [...] Read more.
It is generally understood that the hydrogen permeability of Pd-Ag alloy membranes declines with decreasing temperature. However, recent studies have revealed that the hydrogen permeability of Pd-Ag alloy membranes inversely increases at a certain temperature range and reaches a peak. The peak behavior reflects the shape of pressure-composition isotherms (PCT curves). In order to elucidate the relationship between the reverse temperature dependence of hydrogen permeability and the PCT curves, the hydrogen permeability of pure Pd and Pd-X (X = Ho, Y, and Ni) alloy membranes were investigated. The pure Pd and Pd-5 mol%Ni alloy membranes, in which the α-α’ phase transition occurs, exhibits more significant peak behaviors than Pd-5 mol%Ho, Pd-5 mol%Y, and Pd-23 mol%Ag alloy membranes, in which the α-α’ phase transition is suppressed. Large differences in hydrogen solubility, at the hydrogen pressures above and below the plateau region or the inflection point, make the peak behaviors more significant. It is revealed that the peak temperature can be roughly predicted by the hydrogen pressure at the plateau regions or the inflection points in the PCT curves. Full article
(This article belongs to the Special Issue Recent Advances in Hydrogen Permeable Metal Membranes)
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Full article ">Figure 1
<p>X-ray diffraction (XRD) profiles for Pd-5 mol%Ho, Pd-5 mol%Y, an Pd-5 mol%Ni alloy foils used in this study.</p> Full article ">Figure 2
<p>(<b>a</b>) Arrhenius plot of hydrogen permeation coefficient (<span class="html-italic">ϕ</span>) for pure Pd, Pd-5 mol% Ho alloy, Pd-5 mol% Y alloy, and Pd-5 mol% Ni alloy membranes. For comparison, hydrogen permeation coefficient for Pd-23 mol% Ag alloy membrane is also shown [<a href="#B18-membranes-10-00123" class="html-bibr">18</a>]. The results of Pd-5 mol% Ho, Pd-5 mol% Y, and Pd-23 mol% Ag alloys included in broken square are enlarged in (<b>b</b>).</p> Full article ">Figure 3
<p>Schematic illustration of Arrhenius plot of the hydrogen permeation coefficient showing the definition of the values related to the peak behavior.</p> Full article ">Figure 4
<p>Pressure-composition-isotherms (PCT curves) for pure Pd, Pd-5 mol% Ho alloy, Pd-5 mol% Y alloy and Pd-5 mol% Ni alloy at (<b>a</b>) 400 °C and (<b>b</b>) 250 °C. For comparison, the PCT curves for Pd-23 mol% Ag alloy are also shown [<a href="#B18-membranes-10-00123" class="html-bibr">18</a>]. The PCT curves inside the broken lined squares in (<b>a</b>,<b>b</b>) are enlarged in (<b>c</b>,<b>d</b>).</p> Full article ">Figure 5
<p>(<b>a</b>,<b>b</b>) PCT factors and (<b>c</b>,<b>d</b>) mobility of hydrogen atoms for pure Pd, Pd-5 mol% Ho alloy, Pd-5 mol% Y alloy, Pd-5 mol% Ni alloy, and Pd-23 mol% Ag alloy at (<b>a</b>,<b>c</b>) 400 °C and (<b>b</b>,<b>d</b>) 250 °C. The PCT factors are calculated under a pressure condition of 0.10 MPa at the feed side and 0.01 MPa at the permeation side.</p> Full article ">Figure 6
<p>PCT curves for pure Pd at (<b>a</b>) 200~400 °C and (<b>b</b>)~150 °C reported in the literature [<a href="#B25-membranes-10-00123" class="html-bibr">25</a>].</p> Full article ">Figure 7
<p>Changes in the PCT factor and hydrogen concentrations at feed and permeation sides of pure Pd as a function of the inverse of temperature. The PCT factor and hydrogen concentrations were quantified under a pressure condition of 0.10 MPa at the feed side and 0.01 MPa at the permeation side.</p> Full article ">Figure 8
<p>(<b>a</b>) Changes in the PCT factors of pure Pd and Pd-23 mol% Ag alloy as a function of the inverse of temperature. The PCT factors were quantified under a pressure condition of 0.10 MPa at the feed side and 0.01 MPa at the permeation side. (<b>b</b>,<b>c</b>) Corresponding PCT curves of the pure Pd and Pd-23 mol% Ag alloy at (<b>b</b>) 200 °C and 300 °C and (<b>c</b>) 110 °C and 180 °C (peak temperature).</p> Full article ">Figure 9
<p>Arrhenius plot of the mobility of hydrogen atoms in pure Pd and Pd-23 mol% Ag alloy [<a href="#B18-membranes-10-00123" class="html-bibr">18</a>]. The broken line indicates extrapolation from the mobility at high temperature.</p> Full article ">Figure 10
<p>Isothermal sections at (<b>a</b>) 23 °C and (<b>b</b>–<b>d</b>) 25 °C in the equilibrium phase diagrams for Pd-H-X (X = (a) Ho, (b) Y, (c) Ni, (d) Ag) ternary systems [<a href="#B17-membranes-10-00123" class="html-bibr">17</a>,<a href="#B26-membranes-10-00123" class="html-bibr">26</a>].</p> Full article ">Figure 11
<p>Schematic illustration of the PCT curves showing the relationship between the peak behaviors of the hydrogen permeability and the hydriding properties.</p> Full article ">Figure 12
<p>Relationship between the peak temperature and hydrogen pressure at plateau regions or inflection points in the PCT curves at 250 °C.</p> Full article ">
15 pages, 3045 KiB  
Article
Performance Improvement and Biofouling Mitigation in Osmotic Microbial Fuel Cells via In Situ Formation of Silver Nanoparticles on Forward Osmosis Membrane
by Yuqin Lu, Jia Jia, Hengfeng Miao, Wenquan Ruan and Xinhua Wang
Membranes 2020, 10(6), 122; https://doi.org/10.3390/membranes10060122 - 16 Jun 2020
Cited by 26 | Viewed by 3051
Abstract
An osmotic microbial fuel cell (OsMFC) using a forward osmosis (FO) membrane to replace the proton exchange membrane in a typical MFC achieves superior electricity production and better effluent water quality during municipal wastewater treatment. However, inevitable FO membrane fouling, especially biofouling, has [...] Read more.
An osmotic microbial fuel cell (OsMFC) using a forward osmosis (FO) membrane to replace the proton exchange membrane in a typical MFC achieves superior electricity production and better effluent water quality during municipal wastewater treatment. However, inevitable FO membrane fouling, especially biofouling, has a significantly adverse impact on water flux and thus hinders the stable operation of the OsMFC. Here, we proposed a method for biofouling mitigation of the FO membrane and further improvement in current generation of the OsMFC by applying a silver nanoparticle (AgNP) modified FO membrane. The characteristic tests revealed that the AgNP modified thin film composite (TFC) polyamide FO membrane showed advanced hydrophilicity, more negative zeta potential and better antibacterial property. The biofouling of the FO membrane in OsMFC was effectively alleviated by using the AgNP modified membrane. This phenomenon could be attributed to the changes of TFC–FO membrane properties and the antibacterial property of AgNPs on the membrane surface. An increased hydrophilicity and a more negative zeta potential of the modified membrane enhanced the repulsion between foulants and membrane surface. In addition, AgNPs directly disturbed the functions of microorganisms deposited on the membrane surface. Owing to the biofouling mitigation of the AgNP modified membrane, the water flux and electricity generation of OsMFC were correspondingly improved. Full article
(This article belongs to the Special Issue Membranes for Environmental Applications 2020)
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<p>Sketch map of the preparation for an AgNP modified thin film composite-forward osmosis (TFC–FO) membrane.</p> Full article ">Figure 2
<p>(<b>a</b>) Photographic images, (<b>b</b>) SEM images, and (<b>c</b>) EDX analyses of (1) the pristine and (2) the modified active layer of the TFC–FO membranes.</p> Full article ">Figure 3
<p>Electricity generation of (<b>a</b>) the control OsMFC and (<b>b</b>) AgNP-OsMFC, and (<b>c</b>) their power density and polarization curves.</p> Full article ">Figure 4
<p>Variations in (<b>a</b>) total organic carbon (TOC), (<b>b</b>) NH<sub>4</sub><sup>+</sup>–N, (<b>c</b>) total nitrogen (TN), and (<b>d</b>) total phosphorous (TP) concentrations in the influent, anolyte, catholyte, and FO permeate at the end of each cycle in (1) the control OsMFC and (2) the AgNP-OsMFC, respectively.</p> Full article ">Figure 4 Cont.
<p>Variations in (<b>a</b>) total organic carbon (TOC), (<b>b</b>) NH<sub>4</sub><sup>+</sup>–N, (<b>c</b>) total nitrogen (TN), and (<b>d</b>) total phosphorous (TP) concentrations in the influent, anolyte, catholyte, and FO permeate at the end of each cycle in (1) the control OsMFC and (2) the AgNP-OsMFC, respectively.</p> Full article ">Figure 5
<p>Variations in water flux of the FO membrane and conductivity of the anolyte and catholyte at the end of each cycle in (<b>a</b>) the control OsMFC and (<b>b</b>) AgNP-OsMFC.</p> Full article ">Figure 6
<p>Photos (<b>a</b>) SEM and (<b>b</b>) EDX; (<b>c</b>) results of (1) the fouled pristine membrane and (2) the modified TFC–FO membrane.</p> Full article ">Figure 7
<p>Confocal laser scanning microscopy (CLSM) images of (<b>a</b>) α-<span class="html-small-caps">d</span>-glucopyranose polysaccharides, (<b>b</b>) ß-<span class="html-small-caps">d</span>-glucopyranose polysaccharides, (<b>c</b>) proteins, and (<b>d</b>) microorganisms in the control (<b>1</b>) OsMFC and (<b>2</b>) AgNP-OsMFC.</p> Full article ">
17 pages, 5141 KiB  
Article
Development of Hydrophilic PVDF Membrane Using Vapour Induced Phase Separation Method for Produced Water Treatment
by Normi Izati Mat Nawi, Ho Min Chean, Norazanita Shamsuddin, Muhammad Roil Bilad, Thanitporn Narkkun, Kajornsak Faungnawakij and Asim Laeeq Khan
Membranes 2020, 10(6), 121; https://doi.org/10.3390/membranes10060121 - 16 Jun 2020
Cited by 83 | Viewed by 7758
Abstract
During the production of oil and gas, a large amount of oily wastewater is generated, which would pollute the environment if discharged without proper treatment. As one of the most promising treatment options, membrane material used for oily wastewater treatment should possess desirable [...] Read more.
During the production of oil and gas, a large amount of oily wastewater is generated, which would pollute the environment if discharged without proper treatment. As one of the most promising treatment options, membrane material used for oily wastewater treatment should possess desirable properties of high hydraulic performance combined with high membrane fouling resistance. This project employs the vapor induced phase separation (VIPS) technique to develop a hydrophilic polyvinylidene fluoride (PVDF) membrane with polyethylene glycol (PEG) as an additive for produced water treatment. Results show that thanks to its slow nonsolvent intake, the VIPS method hinders additive leaching during the cast film immersion. The results also reveal that the exposure of the film to the open air before immersion greatly influences the structure of the developed membranes. By extending the exposure time from 0 to 30 min, the membrane morphology change from typical asymmetric with large macrovoids to the macrovoid-free porous symmetric membrane with a granular structure, which corresponds to 35% increment of steady-state permeability to 189 L·m−2h−1bar−1, while maintaining >90% of oil rejection. It was also found that more PEG content resides in the membrane matrix when the exposure time is extended, contributes to the elevation of surface hydrophilicity, which improves the membrane antifouling properties. Overall results demonstrate the potential of VIPS method for the fabrication of hydrophilic PVDF membrane by helping to preserve hydrophilic additive in the membrane matrices. Full article
(This article belongs to the Special Issue Organic–Inorganic Hybrid Membranes for Separation and Purification Applications)
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Full article ">Figure 1
<p>Simplified process flow of membrane preparation using VIPS method.</p> Full article ">Figure 2
<p>Schematic diagram of the crossflow filtration setup.</p> Full article ">Figure 3
<p>The FESEM images of the top surface and cross-sectional morphology of the resulting membranes at a magnification of 3000× and 1000×, respectively.</p> Full article ">Figure 4
<p>The pore size distribution of the resulting membranes.</p> Full article ">Figure 5
<p>The static (<b>a</b>) and dynamic (<b>b</b>) contact angle of the resulting membrane.</p> Full article ">Figure 6
<p>FTIR spectra of the selected membranes.</p> Full article ">Figure 7
<p>XPS wide scan spectra of PVDF/PEG-0 and PVDF/PEG-30 membranes (inset shows the corresponding intensity of selected element).</p> Full article ">Figure 8
<p>Clean water permeability (CWP) of the resulting membranes.</p> Full article ">Figure 9
<p>Permeability of the developed membranes treating PW with frequent water flushing.</p> Full article ">Figure 10
<p>The quality of permeate in terms of oil rejection and turbidity obtained after 1.5 h of PW filtration.</p> Full article ">Figure 11
<p>Fouling resistance analysis of modified membranes developed using NIPS (PVDF/PEG-0, up) and VIPS (PVDF/PEG-30, bottom) techniques.</p> Full article ">
22 pages, 4925 KiB  
Review
A Review for Consistent Analysis of Hydrogen Permeability through Dense Metallic Membranes
by Asuka Suzuki and Hiroshi Yukawa
Membranes 2020, 10(6), 120; https://doi.org/10.3390/membranes10060120 - 10 Jun 2020
Cited by 28 | Viewed by 5534
Abstract
The hydrogen permeation coefficient (ϕ) is generally used as a measure to show hydrogen permeation ability through dense metallic membranes, which is the product of the Fick’s diffusion coefficient (D) and the Sieverts’ solubility constant (K). However, [...] Read more.
The hydrogen permeation coefficient (ϕ) is generally used as a measure to show hydrogen permeation ability through dense metallic membranes, which is the product of the Fick’s diffusion coefficient (D) and the Sieverts’ solubility constant (K). However, the hydrogen permeability of metal membranes cannot be analyzed consistently with this conventional description. In this paper, various methods for consistent analysis of hydrogen permeability are reviewed. The derivations of the descriptions are explained in detail and four applications of the consistent descriptions of hydrogen permeability are introduced: (1) prediction of hydrogen flux under given conditions, (2) comparability of hydrogen permeability, (3) understanding of the anomalous temperature dependence of hydrogen permeability of Pd-Ag alloy membrane, and (4) design of alloy composition of non-Pd-based alloy membranes to satisfy both high hydrogen permeability together with strong resistance to hydrogen embrittlement. Full article
(This article belongs to the Special Issue Recent Advances in Hydrogen Permeable Metal Membranes)
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Figure 1
<p>Schematic illustration of changes in (<b>a</b>) the hydrogen flux (<span class="html-italic">J</span>) and (<b>b</b>) pressure-dependent hydrogen permeation coefficient as a function of the square root of hydrogen pressure at the feed side.</p> Full article ">Figure 2
<p>Schematic illustration showing the relationships between (<b>a</b>) the hydrogen flux (<span class="html-italic">J</span>) and the difference in hydrogen concentration between the feed and permeation sides (Δ<span class="html-italic">c</span>), (<b>b</b>) apparent hydrogen diffusion coefficient (<span class="html-italic">D</span>) and average hydrogen concentration (<span class="html-italic">c</span>), (<b>c</b>) <span class="html-italic">d</span>ln(<span class="html-italic">P</span>/<span class="html-italic">P</span><sup>0</sup>)<sup>0.5</sup> and <span class="html-italic">d</span>ln<span class="html-italic">c</span>, and (<b>d</b>) intrinsic hydrogen diffusion coefficient (<span class="html-italic">D</span>*) and average hydrogen concentration (<span class="html-italic">c</span>).</p> Full article ">Figure 3
<p>Changes in the hydrogen flux through pure Nb membrane at 400 °C normalized by the inverse of the membrane thickness as functions of (<b>a</b>) the differences in hydrogen concentration (∆<span class="html-italic">c</span>), (<b>b</b>) square root of hydrogen pressures between the feed and permeation sides (Δ<span class="html-italic">P</span><sup>0.5</sup>) and (<b>c</b>) PCT factor (<span class="html-italic">f</span><sub>PCT</sub>).</p> Full article ">Figure 4
<p>Change in the hydrogen flux through pure Pd membrane at 300 °C as a function of the difference in the square root of hydrogen pressures at the feed and permeation sides [<a href="#B15-membranes-10-00120" class="html-bibr">15</a>].</p> Full article ">Figure 5
<p>Changes in (<b>a</b>) the hydrogen flux and (<b>b</b>) the pressure-dependent hydrogen permeation coefficient for pure Pd membrane as a function of the square root of hydrogen pressure at the feed side [<a href="#B15-membranes-10-00120" class="html-bibr">15</a>].</p> Full article ">Figure 6
<p>(<b>a</b>) pressure–composition isotherm (PCT curve) for pure Pd at 300 °C and (<b>b</b>) change in the hydrogen flux through pure Pd membrane at 300 °C in <a href="#membranes-10-00120-f004" class="html-fig">Figure 4</a> replotted as a function of the PCT factor.</p> Full article ">Figure 7
<p>Comparison of the experimental and estimated hydrogen fluxes through pure Pd membrane at 300 °C under a pressure condition of 1.000 MPa at the feed side and 0.502 MPa at the permeation side. The estimations were carried out using the conventional hydrogen permeation coefficient, the pressure-dependent hydrogen permeation coefficient, and the PCT factor.</p> Full article ">Figure 8
<p>Arrhenius plot of the hydrogen permeation coefficient for the power law reported in the literature [<a href="#B13-membranes-10-00120" class="html-bibr">13</a>,<a href="#B14-membranes-10-00120" class="html-bibr">14</a>] and the pressure-dependent hydrogen permeation coefficient at 0.1 MPa [<a href="#B15-membranes-10-00120" class="html-bibr">15</a>].</p> Full article ">Figure 9
<p>Arrhenius plot of hydrogen permeation coefficient (<span class="html-italic">ϕ</span>) of Pd–23 mol%Ag alloy membrane [<a href="#B27-membranes-10-00120" class="html-bibr">27</a>]. The temperature dependence of hydrogen permeation coefficients of Pd−25 mol%Ag reported in the literature [<a href="#B33-membranes-10-00120" class="html-bibr">33</a>,<a href="#B34-membranes-10-00120" class="html-bibr">34</a>] is also shown in the figure.</p> Full article ">Figure 10
<p>(<b>a</b>) Pressure–composition isotherms (PCT curves) for Pd-23 mol%Ag alloy, (<b>b</b>) schematic illustration of a PCT curve showing how to estimate the difference in hydrogen concentrations between feed and permeation sides (Δ<span class="html-italic">c</span>) and the PCT factor (<span class="html-italic">f</span><sub>PCT</sub>), and (<b>c</b>,<b>d</b>) changes in the hydrogen flux normalized by the inverse of membrane thickness as functions of (<b>c</b>) Δ<span class="html-italic">c</span> and (<b>d</b>) <span class="html-italic">f</span><sub>PCT</sub> [<a href="#B27-membranes-10-00120" class="html-bibr">27</a>], with copyright permission from Japan Institute of Metal and Materials (JIM).</p> Full article ">Figure 11
<p>Arrhenius plot of the mobility (<span class="html-italic">B</span>) for hydrogen diffusion in Pd–23 mol%Ag alloy [<a href="#B27-membranes-10-00120" class="html-bibr">27</a>]. The intrinsic hydrogen diffusion coefficients reported by Wang et al. [<a href="#B39-membranes-10-00120" class="html-bibr">39</a>] are modified into the mobility for hydrogen diffusion and plotted in the figure, with copyright permission from Japan Institute of Metal and Materials (JIM).</p> Full article ">Figure 12
<p>(<b>a</b>) Temperature dependence of the PCT factor (<span class="html-italic">f</span><sub>PCT</sub>), the hydrogen concentration at each feed and permeation side of the membrane (<span class="html-italic">c</span><sub>1</sub> and <span class="html-italic">c</span><sub>2</sub>), and their difference (Δ<span class="html-italic">c</span>) when the pressure condition of the feed and permeation sides are fixed to be 0.10 and 0.01 MPa, respectively [<a href="#B27-membranes-10-00120" class="html-bibr">27</a>]. (<b>b</b>) PCT curves of Pd-23 mol%Ag alloy at low pressure range [<a href="#B27-membranes-10-00120" class="html-bibr">27</a>], with copyright permission from Japan Institute of Metal and Materials (JIM).</p> Full article ">Figure 13
<p>Schematic illustration of PCT curves showing the concept for alloy design [<a href="#B28-membranes-10-00120" class="html-bibr">28</a>,<a href="#B32-membranes-10-00120" class="html-bibr">32</a>], with copyright permission from Japan Institute of Metal and Materials (JIM).</p> Full article ">Figure 14
<p>(<b>a</b>) PCT curves of pure V [<a href="#B47-membranes-10-00120" class="html-bibr">47</a>] and V-Fe alloys at 300 °C, (<b>b</b>) PCT factors for each alloy at each condition represented by star symbol (☆) in (<b>a</b>), and (<b>c</b>) time dependence of hydrogen flux normalized by the inverse of membrane thickness (<span class="html-italic">J·L</span>) for Pd-27 mol%Ag-coated V-10 mol%Fe alloy membranes at 300 °C. The experimental results for V-7.5 and V-11 mol%Fe alloy membranes under the conditions represented by the star symbols in (<b>a</b>) and the estimated value for Pd-23 mol%Ag alloy under the same condition as V-10 mol%Fe alloy are also shown in the figure [<a href="#B28-membranes-10-00120" class="html-bibr">28</a>].</p> Full article ">Figure 15
<p>Relationship between the pre-exponential factor (<span class="html-italic">B</span><sub>0</sub>) and the activation energy (<span class="html-italic">E</span>) for V-based solid solution alloys [<a href="#B28-membranes-10-00120" class="html-bibr">28</a>,<a href="#B48-membranes-10-00120" class="html-bibr">48</a>], Nb-based solid solution alloys [<a href="#B32-membranes-10-00120" class="html-bibr">32</a>], and Nb-based dual phase alloys [<a href="#B30-membranes-10-00120" class="html-bibr">30</a>,<a href="#B31-membranes-10-00120" class="html-bibr">31</a>].</p> Full article ">
12 pages, 2890 KiB  
Article
Free Standing, Large-Area Silicon Nitride Membranes for High Toxin Clearance in Blood Surrogate for Small-Format Hemodialysis
by Joshua J. Miller, Jared A. Carter, Kayli Hill, Jon-Paul S. DesOrmeaux, Robert N. Carter, Thomas R. Gaborski, James A. Roussie, James L. McGrath and Dean G. Johnson
Membranes 2020, 10(6), 119; https://doi.org/10.3390/membranes10060119 - 6 Jun 2020
Cited by 1 | Viewed by 3484
Abstract
Developing highly-efficient membranes for toxin clearance in small-format hemodialysis presents a fabrication challenge. The miniaturization of fluidics and controls has been the focus of current work on hemodialysis (HD) devices. This approach has not addressed the membrane efficiency needed for toxin clearance in [...] Read more.
Developing highly-efficient membranes for toxin clearance in small-format hemodialysis presents a fabrication challenge. The miniaturization of fluidics and controls has been the focus of current work on hemodialysis (HD) devices. This approach has not addressed the membrane efficiency needed for toxin clearance in small-format hemodialysis devices. Dr. Willem Kolff built the first dialyzer in 1943 and many changes have been made to HD technology since then. However, conventional HD still uses large instruments with bulky dialysis cartridges made of ~2 m2 of 10 micron thick, tortuous-path membrane material. Portable, wearable, and implantable HD systems may improve clinical outcomes for patients with end-stage renal disease by increasing the frequency of dialysis. The ability of ultrathin silicon-based sheet membranes to clear toxins is tested along with an analytical model predicting long-term multi-pass experiments from single-pass clearance experiments. Advanced fabrication methods are introduced that produce a new type of nanoporous silicon nitride sheet membrane that features the pore sizes needed for middle-weight toxin removal. Benchtop clearance results with sheet membranes (~3 cm2) match a theoretical model and indicate that sheet membranes can reduce (by orders of magnitude) the amount of membrane material required for hemodialysis. This provides the performance needed for small-format hemodialysis. Full article
(This article belongs to the Special Issue Advanced Silicon Membranes)
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Graphical abstract
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<p>Expected remaining lifetime of end-stage renal disease (ESRD) patients on hemodialysis (HD) for the past two decades. For all age groups of ESRD patients, there has been no significant improvement in life expectancies [<a href="#B9-membranes-10-00119" class="html-bibr">9</a>]. This demonstrates a need for disruptive technologies in the field of hemodialysis.</p> Full article ">Figure 2
<p>Sheet membrane fabrication process. (<b>a</b>) Assembled device halves ready for membrane transfer. (<b>b</b>) Loading three ~ 1″ × 1″ samples of nanoporous silicon nitride membrane wafers prior to release etch. (<b>c</b>) Etching using a Xactix<sup>®</sup> E2 tool allows for transfer from the silicon wafer portions to the device frames. (<b>d</b>) Separating the mesh and sheet membranes from wafer samples. (<b>e</b>) Vacuum chuck inverted for transfer onto acrylic. (<b>f</b>) Devices applied to sheet membranes. (<b>g</b>) Device ready for leak check and sealing.</p> Full article ">Figure 3
<p>Nanoporous nitride oxide membrane. (<b>a</b>) SEM of nanoporous silicon nitride (NPN) membrane surface showing the pores. (<b>b</b>) SEM of cleaved NPN membrane showing relationship between pore size and membrane thickness. (<b>c</b>) Drawing of the patterned SU8 layer. (<b>d</b>) Optical image of the SU8 structure, here shown on a chip-based NPN membrane.</p> Full article ">Figure 4
<p>(<b>a</b>) Vacuum is applied through a mesh, to aid transfer, in order to lift the membrane from the wafer substrate after it is etched free in the Xactix<sup>®</sup> E2. (<b>b</b>) The membrane is aligned with the bottom half of the device, which is made of two layers—one to support the membrane, and the other to hold the fluidic channels. (<b>c</b>) The upper half of the device is adhered to the lower half with pressure-sensitive adhesive. (<b>d</b>) The final device is leak tested and ready for clearance testing.</p> Full article ">Figure 5
<p>Comparison of the theoretical real-time urea clearance (see Equation (15)) to two multi-pass benchtop experiments with the sheet membrane device. Agreement was observed to match theory, thus showing that our model for <math display="inline"><semantics> <mrow> <mi>K</mi> <mo>=</mo> <mi>k</mi> <mi>r</mi> <mrow> <mo>(</mo> <mrow> <msub> <mi>A</mi> <mrow> <mi>m</mi> <mi>p</mi> </mrow> </msub> <mo>/</mo> <msub> <mi>A</mi> <mrow> <mi>s</mi> <mi>p</mi> </mrow> </msub> </mrow> <mo>)</mo> </mrow> <mi>k</mi> <mi>r</mi> <mi>γ</mi> </mrow> </semantics></math> is accurate (see Equation (18)). <span class="html-italic">A<sub>mp</sub></span> = 2.88 × 10<sup>–4</sup> m<sup>2</sup>; <span class="html-italic">A<sub>sp</sub></span> =1.4 × 10<sup>–6</sup> m<sup>2</sup>. (Experiment 1: R<sup>2</sup> = 0.98; Experiment 2: R<sup>2</sup> = 0.96.)</p> Full article ">Figure 6
<p>Single-pass clearance of urea in 100% serum, normalized to the membrane surface area. Adapted from Advanced Healthcare Materials, Wiley Publishing, 2020. [<a href="#B5-membranes-10-00119" class="html-bibr">5</a>].</p> Full article ">
15 pages, 5334 KiB  
Article
Combined Effect of Colloids and SMP on Membrane Fouling in MBRs
by Dimitra Banti, Manassis Mitrakas, Georgios Fytianos, Alexandra Tsali and Petros Samaras
Membranes 2020, 10(6), 118; https://doi.org/10.3390/membranes10060118 - 6 Jun 2020
Cited by 23 | Viewed by 3175
Abstract
Membrane fouling investigations in membrane bioreactors (MBRs) are a top research issue. The aim of this work is to study the combined effect of colloids and soluble microbial products (SMPs) on membrane fouling. Two lab-pilot MBRs were investigated for treating two types of [...] Read more.
Membrane fouling investigations in membrane bioreactors (MBRs) are a top research issue. The aim of this work is to study the combined effect of colloids and soluble microbial products (SMPs) on membrane fouling. Two lab-pilot MBRs were investigated for treating two types of wastewater (wwt), synthetic and domestic. Transmembrane pressure (TMP), SMP, particle size distribution and treatment efficiency were evaluated. Chemical Oxygen Demand (COD) removal and nitrification were successful for both kinds of sewage reaching up to 95–97% and 100%, respectively. Domestic wwt presented 5.5 times more SMP proteins and 11 times more SMP carbohydrates compared to the synthetic one. In contrast, synthetic wwt had around 20% more colloids in the mixed liquor with a size lower than membrane pore size (<400 nm) than domestic. Finally, the TMP at 36 days reached 16 kPa for synthetic wwt and 11 kPa for domestic. Therefore, synthetic wwt, despite its low concentration of SMPs, caused severe membrane fouling compared to domestic, a result that is attributed to the increased concentration of colloids. Consequently, the quantity of colloids and possibly their special characteristics play decisive and more important roles in membrane fouling compared to the SMP—a novel conclusion that can be used to mitigate membranes fouling. Full article
(This article belongs to the Special Issue New Perspectives on Membrane Bioreactors)
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<p>Flow diagram of the membrane bioreactor (MBR) units. AT: aeration tank (20 L), MT: membrane tank (5 L), PLC: programmable logic controller, CO: air compressor, DO: dissolved oxygen controller, PI: pressure indicator, P1: raw wastewater feed pump, Ρ2: activated sludge recirculation pump, Ρ3: effluent pump.</p> Full article ">Figure 2
<p>COD, NH<sub>4</sub>-N and total N percentage removal for synthetic and domestic wastewater.</p> Full article ">Figure 3
<p>SMP concentration in the form of proteins in the mixed liquor of synthetic and domestic wastewater.</p> Full article ">Figure 4
<p>SMP concentration in the form of carbohydrates in the mixed liquor of synthetic and domestic wastewater.</p> Full article ">Figure 5
<p>Loosely bound EPS (LBEPS) and tightly bound EPS (TBEPS) concentrations in the form of proteins for the mixed liquor of synthetic and domestic wastewater.</p> Full article ">Figure 6
<p>LBEPS and TBEPS concentrations in the form of carbohydrates for the mixed liquor of synthetic and domestic wastewater.</p> Full article ">Figure 7
<p>Typical TMP graphs as a function of MBR operation time for synthetic versus domestic wastewater. Flux for synthetic wwt = 16.4 Lmh, flux for domestic wwt = 20.9 Lmh. For both MBRs temperature = 24 ± 2 °C and DO in both ATs =2.5 ± 0.5 mg/L.</p> Full article ">Figure 8
<p>Percentage of particles smaller than 1000 nm for a sample from the aeration tank (AΤ) as a function of MBR operation time (<b>a</b>) for synthetic versus (<b>b</b>) domestic wastewater.</p> Full article ">Figure 9
<p>Cumulative percentage of particles smaller than 1000 nm for a sample from the aeration tank (AΤ) as a function of MBR operation time (<b>a</b>) for synthetic versus (<b>b</b>) domestic wastewater.</p> Full article ">Figure 10
<p>Percentage of particles smaller than 1000 nm for samples of the permeate (p) as a function of MBR operation time (<b>a</b>) for synthetic versus (<b>b</b>) domestic wastewater.</p> Full article ">Figure 11
<p>Cumulative percentage of particles smaller than 1000 nm for samples of the permeate (p) as a function of MBR operation time (<b>a</b>) for synthetic versus (<b>b</b>) domestic wastewater.</p> Full article ">
20 pages, 7852 KiB  
Article
A Molecular Dynamics Study on Rotational Nanofluid and Its Application to Desalination
by Qingsong Tu, Wice Ibrahimi, Steven Ren, James Wu and Shaofan Li
Membranes 2020, 10(6), 117; https://doi.org/10.3390/membranes10060117 - 6 Jun 2020
Cited by 6 | Viewed by 3559
Abstract
In this work, we systematically study a rotational nanofluidic device for reverse osmosis (RO) desalination by using large scale molecular dynamics modeling and simulation. Moreover, we have compared Molecular Dynamics simulation with fluid mechanics modeling. We have found that the pressure generated by [...] Read more.
In this work, we systematically study a rotational nanofluidic device for reverse osmosis (RO) desalination by using large scale molecular dynamics modeling and simulation. Moreover, we have compared Molecular Dynamics simulation with fluid mechanics modeling. We have found that the pressure generated by the centrifugal motion of nanofluids can counterbalance the osmosis pressure developed from the concentration gradient, and hence provide a driving force to filtrate fresh water from salt water. Molecular Dynamics modeling of two different types of designs are performed and compared. Results indicate that this novel nanofluidic device is not only able to alleviate the fouling problem significantly, but it is also capable of maintaining high membrane permeability and energy efficiency. The angular velocity of the nanofluids within the device is investigated, and the critical angular velocity needed for the fluids to overcome the osmotic pressure is derived. Meanwhile, a maximal angular velocity value is also identified to avoid Taylor-Couette instability. The MD simulation results agree well with continuum modeling results obtained from fluid hydrodynamics theory, which provides a theoretical foundation for scaling up the proposed rotational osmosis device. Successful fabrication of such rotational RO membrane centrifuge may potentially revolutionize the membrane desalination technology by providing a fundamental solution to the water resource problem. Full article
(This article belongs to the Special Issue Numerical Modeling and Performance Prediction of Nanofiltration)
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Figure 1
<p>Proposed scaled up rotational nanofluidic device with nanoporous membrane wall. (<b>a</b>) Schematic illustration of an inner rotator generated swirling motion, (<b>b</b>) The coarse scale holes on the wall of the centrifuge, and (<b>c</b>) the fine scale pores in the graphene membrane patch covered on the coarse sale holes in the centrifuge wall.</p> Full article ">Figure 2
<p>Molecular structures of two types of models for MD calculations. (<b>a</b>) The top and bisection view of Model I, with light-blue tube represents nanoporous membrane and pink tube represents rotator. (<b>b</b>) The top and bisection view of Model II, with light-blue tube represents nanoporous membrane and dark-blue tube represents rotator.</p> Full article ">Figure 3
<p>Snapshots of Model II over six simulation times, in unit nano-second. Na<math display="inline"><semantics> <msup> <mrow/> <mo>+</mo> </msup> </semantics></math> and Cl<math display="inline"><semantics> <msup> <mrow/> <mo>−</mo> </msup> </semantics></math> ions are in blue and yellow color, other molecules are H<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>O with oxygen atom in red color.</p> Full article ">Figure 4
<p>(<b>a</b>) Water density profiles of model type II along the radial and longitudinal directions under <math display="inline"><semantics> <mrow> <mi>ω</mi> <mo>=</mo> <mn>17</mn> <mo>.</mo> <mn>5</mn> </mrow> </semantics></math> rad/ns (Values along azimuthal direction are averaged). The trajectory of a typical Na<math display="inline"><semantics> <msup> <mrow/> <mo>+</mo> </msup> </semantics></math> ion (<b>b</b>) and Cl<math display="inline"><semantics> <msup> <mrow/> <mo>−</mo> </msup> </semantics></math> ion (<b>c</b>) which are located near the center at <math display="inline"><semantics> <mrow> <mi>t</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics></math> and move to the membrane wall at <math display="inline"><semantics> <mrow> <mi>t</mi> <mo>=</mo> <mn>2</mn> </mrow> </semantics></math> ns.</p> Full article ">Figure 5
<p>(<b>a</b>) Top-view of rotating water molecules (Oxygen in red and Hydrogen in white) with velocity vector (blue arrows) plotted on Oxygen. (<b>b</b>) 3D plot of velocity field of water molecules. Only velocity vectors (blue arrows) are shown. Azimuthal velocity <math display="inline"><semantics> <msub> <mi>v</mi> <mi>θ</mi> </msub> </semantics></math> along radial direction of Model I (<b>c</b>) and Model II (<b>d</b>) under different angular velocities.</p> Full article ">Figure 6
<p>(<b>a</b>) Averaged azimuthal velocities of fluid near <math display="inline"><semantics> <mrow> <mi>r</mi> <mo>=</mo> <msub> <mi>R</mi> <mi>i</mi> </msub> </mrow> </semantics></math> as a function of angular velocity <math display="inline"><semantics> <mi>ω</mi> </semantics></math> for Model I and Model II. The curve “Non-slip BC” means <math display="inline"><semantics> <mrow> <msub> <mi>v</mi> <mi>θ</mi> </msub> <mo>=</mo> <msub> <mi>R</mi> <mi>i</mi> </msub> <mi>ω</mi> </mrow> </semantics></math>. (<b>b</b>) Lower and Upper limits of the centrifugal pressure <math display="inline"><semantics> <msub> <mi>P</mi> <mi>ω</mi> </msub> </semantics></math> derived from fluid dynamics and that obtained from MD calculations.</p> Full article ">Figure 7
<p>Taylor instability and vortex when <math display="inline"><semantics> <mrow> <mi>ω</mi> <mo>=</mo> <mn>90</mn> </mrow> </semantics></math> rad/ns. (<b>a</b>) Two vortexes (sketched by black lines) are observed inside the container. The fluid is rendered as colored colloid for better 3D view. (<b>b</b>) Water density profile in radial-longitudinal plane. (<b>c</b>) Distribution of water density along radial direction. The Nano-Porous Tube (NPT) wall in the figure signifies the location of the CNT membrane wall and that its properties are held at constant over time.</p> Full article ">Figure 8
<p>(<b>a</b>) Volume of filtrated water as a function of simulation time. (<b>b</b>) Water flux as a function of angular velocity.</p> Full article ">Figure 9
<p>(<b>a</b>) Comparison of permeability of the current system with other RO materials. (<b>b</b>) Calculated energy efficiency as a function of simulation time, under <math display="inline"><semantics> <mrow> <mi>ω</mi> <mo>=</mo> <mn>35</mn> </mrow> </semantics></math> rad/ns.</p> Full article ">Figure A1
<p>Schematic illustration on how to scale-up a nano-porous rotating membrane to macroscale and its macroscale fabrication concept. (<b>a</b>) Multiscale porous membrane structure, (<b>b</b>) Rotating porous membrane, and (<b>c</b>) A rotator-generated centrifugal fluid motion of the feed solution (seawater in RO).</p> Full article ">
16 pages, 2094 KiB  
Article
Electrochemical Characteristics of Glycerolized PEO-Based Polymer Electrolytes
by Muhammad S. Mustafa, Hewa O. Ghareeb, Shujahadeen B. Aziz, M. A. Brza, Shakhawan Al-Zangana, Jihad M. Hadi and M. F. Z. Kadir
Membranes 2020, 10(6), 116; https://doi.org/10.3390/membranes10060116 - 5 Jun 2020
Cited by 46 | Viewed by 4356
Abstract
In this article, poly(ethylene oxide)-based polymer electrolyte films doped with ammonium iodide (NH4I) and plasticized with glycerol were provided by a solution casting method. In the unplasticized system, the maximum ionic conductivity of 3.96 × 10 − 5   S cm [...] Read more.
In this article, poly(ethylene oxide)-based polymer electrolyte films doped with ammonium iodide (NH4I) and plasticized with glycerol were provided by a solution casting method. In the unplasticized system, the maximum ionic conductivity of 3.96 × 10 − 5   S cm−1 was achieved by the electrolyte comprised of 70 wt. % PEO:30 wt. % NH4I. The conductivity was further enhanced up to   ( 1.77 × 10 − 4 S cm−1) for the plasticized system when 10 wt. % glycerol was added to the highest conducting unplasticized one at ambient temperature. The films were characterized by various techniques to evaluate their electrochemical performance. The results of impedance spectroscopy revealed that bulk resistance (Rb) considerably decreased for the highest plasticized polymer electrolyte. The dielectric properties and electric modulus parameters were studied in detail. The LSV analysis verified that the plasticized system can be used in energy storage devices with electrochemical stability up to 1.09 V and the TNM data elucidated that the ions were the main charge carrier. The values of the ion transference number (tion) and electron transfer number (tel) were calculated. The nonappearance of any redox peaks in the cyclic voltammograms indicated that the chemical reaction had not occurred at the electrode/electrolyte interface. Full article
(This article belongs to the Special Issue Electromembrane Processes: Emerging Applications, Materials and Process Configurations)
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<p>Real part of dielectric constant (<math display="inline"><semantics> <msup> <mi>ε</mi> <mo>′</mo> </msup> </semantics></math>) against frequency for un-plasticized PEOH1, PEOH2, PEOH3 and plasticized PEOH4 at room temperature.</p> Full article ">Figure 2
<p>Imaginary part of dielectric loss (<math display="inline"><semantics> <msup> <mi>ε</mi> <mo>″</mo> </msup> </semantics></math>) against frequency for unplasticized PEOH1, PEOH2, PEOH3 and plasticized PEOH4 at room temperature.</p> Full article ">Figure 3
<p>Part of dielectric constant loss (<math display="inline"><semantics> <msup> <mi>M</mi> <mo>′</mo> </msup> </semantics></math>) against frequency for un-plasticized PEOH1, PEOH2, PEOH3 and plasticized PEOH4 at room temperature.</p> Full article ">Figure 4
<p>Imaginary part of dielectric constant loss (<math display="inline"><semantics> <msup> <mi>M</mi> <mo>″</mo> </msup> </semantics></math>) against frequency for un-plasticized PEOH1, PEOH2, PEOH3 and plasticized PEOH4 at room temperature.</p> Full article ">Figure 5
<p>The room temperature impedance plots for (<b>a</b>) PEOH1; (<b>b</b>) PEOH2; (<b>c</b>) PEOH3 and (<b>d</b>) PEOH4.</p> Full article ">Figure 6
<p>Current–time plot for the highest conducting plasticized (PEOH4) system.</p> Full article ">Figure 7
<p>Linear sweep voltammetry for PEOH4 film at scan rate of 10 mV s<sup>−1</sup> at ambient temperature.</p> Full article ">Figure 8
<p>Cyclic voltammetry responses of PEOH4 in the potential range 0 to 0.9 V at different sweep rates from 10 to 100 mV s<sup>−1</sup>.</p> Full article ">
10 pages, 2348 KiB  
Article
Influences of Combined Organic Fouling and Inorganic Scaling on Flux and Fouling Behaviors in Forward Osmosis
by Youngpil Chun, Kwanho Jeong and Kyung Hwa Cho
Membranes 2020, 10(6), 115; https://doi.org/10.3390/membranes10060115 - 2 Jun 2020
Cited by 4 | Viewed by 3029
Abstract
This study investigated the influence of combined organic fouling and inorganic scaling on the flux and fouling behaviors of thin-film composite (TFC) forward osmosis (FO) membranes. Two organic macromolecules, namely, bovine serum albumin (BSA) and sodium alginate (SA), and gypsum (GS), as an [...] Read more.
This study investigated the influence of combined organic fouling and inorganic scaling on the flux and fouling behaviors of thin-film composite (TFC) forward osmosis (FO) membranes. Two organic macromolecules, namely, bovine serum albumin (BSA) and sodium alginate (SA), and gypsum (GS), as an inorganic scaling agent, were selected as model foulants. It was found that GS scaling alone caused the most severe flux decline. When a mixture of organic and inorganic foulants was employed, the flux decline was retarded, compared with when the filtration was performed with only the inorganic scaling agent (GS). The early onset of the conditioning layer formation, which was due to the organics, was probably the underlying mechanism for this inhibitory phenomenon, which had suppressed the deposition and growth of the GS crystals. Although the combined fouling resulted in less flux decline, compared with GS scaling alone, the concoction of SA and GS resulted in more fouling and flux decline, compared with the mixture of BSA and GS. This was because of the carboxyl acidity of the alginate, which attracted calcium ions and formed an intermolecular bridge. Full article
(This article belongs to the Section Membrane Processing and Engineering)
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<p>Permeate water flux, <math display="inline"><semantics> <mrow> <msub> <mi>J</mi> <mi>w</mi> </msub> <mo>,</mo> </mrow> </semantics></math> patterns and the corresponding total dissolved solids (TDS) concentration of FS: (<b>a</b>) TFC-1, (<b>b</b>) TFC-2, (1) GS, (2) BSA + GS, and (3) SA + GS.</p> Full article ">Figure 2
<p>Permeate <math display="inline"><semantics> <mrow> <msub> <mi>J</mi> <mi>w</mi> </msub> </mrow> </semantics></math> of (<b>a</b>) TFC-1 and (<b>b</b>) TFC-2 during fouling and scaling experiments. The experiments were conducted for 20 h. The permeate <math display="inline"><semantics> <mrow> <msub> <mi>J</mi> <mi>w</mi> </msub> </mrow> </semantics></math> was normalized by the pure <math display="inline"><semantics> <mrow> <msub> <mi>J</mi> <mi>w</mi> </msub> </mrow> </semantics></math> utilizing MilliQ water as the feed and 1 M NaCl as DS, at the same initial flux of 20 ± 0.5 LMH.</p> Full article ">Figure 3
<p>Field-emission scanning electron microscopy (FESEM) images of (<b>a</b>) TFC-1 and (<b>b</b>) TFC-2 after (1) GS, (2) BSA + GS and (3) SA + GS scaling or foulings, respectively.</p> Full article ">Figure 4
<p>Representative attenuated total reflectance (ATR)-Fourier transform infrared (ATR-FTIR) absorbance spectra for (<b>a</b>) TFC-1 and (<b>b</b>) TFC-2.</p> Full article ">
16 pages, 3748 KiB  
Article
PVA-Based Mixed Matrix Membranes Comprising ZSM-5 for Cations Separation
by Fangmeng Sheng, Noor Ul Afsar, Yanran Zhu, Liang Ge and Tongwen Xu
Membranes 2020, 10(6), 114; https://doi.org/10.3390/membranes10060114 - 30 May 2020
Cited by 25 | Viewed by 4219
Abstract
The traditional ion-exchange membranes face the trade-off effect between the ion flux and perm-selectivity, which limits their application for selective ion separation. Herein, we amalgamated various amounts of the ZSM-5 with the polyvinyl alcohol as ions transport pathways to improve the permeability of [...] Read more.
The traditional ion-exchange membranes face the trade-off effect between the ion flux and perm-selectivity, which limits their application for selective ion separation. Herein, we amalgamated various amounts of the ZSM-5 with the polyvinyl alcohol as ions transport pathways to improve the permeability of monovalent cations and exclusively reject the divalent cations. The highest contents of ZSM-5 in the mixed matrix membranes (MMMs) can be extended up to 60 wt% while the MMMs with optimized content (50 wt%) achieved high perm-selectivity of 34.4 and 3.7 for H+/Zn2+ and Li+/Mg2+ systems, respectively. The obtained results are high in comparison with the commercial CSO membrane. The presence of cationic exchange sites in the ZSM-5 initiated the fast transport of proton, while the microporous crystalline morphology restricted the active transport of larger hydrated cations from the solutions. Moreover, the participating sites and porosity of ZSM-5 granted continuous channels for ions electromigration in order to give high limiting current density to the MMMs. The SEM analysis further exhibited that using ZSM-5 as conventional fillers, gave a uniform and homogenous formation to the membranes. However, the optimized amount of fillers and the assortment of a proper dispersion phase are two critical aspects and must be considered to avoid defects and agglomeration of these enhancers during the formation of membranes. Full article
(This article belongs to the Special Issue Electromembrane Processes: Experiments and Modelling)
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<p>Schematic diagram of the testing device for the I–V curve.</p> Full article ">Figure 2
<p>(<b>a</b>) Skeletal diagram, (<b>b</b>) nitrogen adsorption-desorption isotherms, and (<b>c</b>) pore size distribution profiles of ZSM-5 zeolite.</p> Full article ">Figure 3
<p>The adsorption property of ZSM-5 for LiCl/MgCl<sub>2</sub> mixed solutions: (<b>a</b>) Li<sup>+</sup> adsorption vs. concentration of solution, (<b>b</b>) Li<sup>+</sup> adsorption vs. time (day), respectively.</p> Full article ">Figure 4
<p>Surface (<b>A1</b>–<b>E1</b>) and cross-section (<b>A2</b>–<b>E2</b>) morphologies of ZSM-5/PVA-based mixed matrix membranes (MMMs): (<b>A</b>), (<b>B</b>), (<b>C</b>), (<b>D</b>) and (<b>E</b>) are 20 wt%, 30 wt%, 40 wt%, 50 wt%, and 60 wt% zeolite doping content, respectively.</p> Full article ">Figure 5
<p>XRD pattern of ZSM-5/PVA-based mixed matrix membranes (MMMs) in comparison with the ZSM-5 zeolite powder.</p> Full article ">Figure 6
<p>Water uptake (WU) and area swelling of the prepared MMMs.</p> Full article ">Figure 7
<p>(<b>a</b>) Current-voltage curves, and (<b>b</b>) membrane resistance of representative’s membranes.</p> Full article ">Figure 8
<p>The ion flux and perm-selectivity of ZSM-5/PVA-based MMMs for H<sup>+</sup>/Zn<sup>2+</sup>.</p> Full article ">Figure 9
<p>The ion flux and perm-selectivity of ZSM-5/PVA-based MMMs for Li<sup>+</sup>/Mg<sup>2+</sup>.</p> Full article ">
19 pages, 2739 KiB  
Article
How Overlimiting Current Condition Influences Lactic Acid Recovery and Demineralization by Electrodialysis with Nanofiltration Membrane: Comparison with Conventional Electrodialysis
by Marielle Beaulieu, Véronique Perreault, Sergey Mikhaylin and Laurent Bazinet
Membranes 2020, 10(6), 113; https://doi.org/10.3390/membranes10060113 - 27 May 2020
Cited by 20 | Viewed by 3240
Abstract
Acid whey is the main co-product resulting from the production of fresh cheeses and Greek-type yogurts. It generally goes through a spray-drying process prior to valorization, but it needs to be deacidified (lactic acid recovery) and demineralized beforehand to obtain a powder of [...] Read more.
Acid whey is the main co-product resulting from the production of fresh cheeses and Greek-type yogurts. It generally goes through a spray-drying process prior to valorization, but it needs to be deacidified (lactic acid recovery) and demineralized beforehand to obtain a powder of quality with all the preserved compounds of interest such as lactose and proteins. Electrodialysis (ED) is a process actually used for acid whey treatment, but scaling formation at the surface of the ion-exchange membrane is still a major problem. In this work, a combination of two new avenues of ED treatment has been studied. First, the integration of a nanofiltration (NF) membrane in an ED conventional stack was compared to a classical ED stack with an anion-exchange membrane in a standard current condition. Secondly, both configurations were tested in the overlimiting current condition to study the impact of electroconvective vortices on process efficiency. The combined effects of the NF membrane and overlimiting current condition led to a higher lactic acid recovery rate of acid whey (40%), while the conventional ED stack in the overlimiting current condition led to a higher demineralization (87% based on the total cation concentration). Those effects were related to the conductivity, pH, global resistance, and energy consumption of each treatment that are influenced by water splitting phenomenon, which was decreased in the overlimiting condition. Full article
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<p>ED cell configuration (<b>a</b>) “CACAC” and (<b>b</b>) “CNfCNfC” used for acid whey deacidification and demineralization.</p> Full article ">Figure 2
<p>Determination of limiting current density (LCD) of (<b>a</b>) CACAC and (<b>b</b>) CNfCNfC membrane configuration.</p> Full article ">Figure 3
<p>Representative (<b>a</b>) current–voltage (CV) curves for AEM and NF membranes and (<b>b</b>) ChP for an AEM membrane at current density of 2.9 mA/cm<sup>2</sup>.</p> Full article ">Figure 4
<p>pH evolution in (<b>a</b>) whey and (<b>b</b>) NaCl solution during electrodialysis (ED) according to the configurations (CACAC and CNfCNf) and the current conditions (underlimiting and overlimiting) used.</p> Full article ">Figure 5
<p>Evolution of lactic acid in (<b>a</b>) whey and (<b>b</b>) NaCl compartments during ED according to the configurations (CACAC and CNfCNf) and the current conditions (underlimiting and overlimiting) used.</p> Full article ">Figure 6
<p>(<b>a</b>) Whey and (<b>b</b>) NaCl conductivity during ED for all configurations and current conditions tested.</p> Full article ">Figure 7
<p>Scheme of ionic migration during ED treatments.</p> Full article ">Figure 8
<p>Ion concentration in whey compartment during ED treatments: (<b>a</b>) calcium, (<b>b</b>) potassium, (<b>c</b>) magnesium, (<b>d</b>) sodium, and (<b>e</b>) phosphorous.</p> Full article ">Figure 9
<p>Overall system resistance of the electrodialysis cell.</p> Full article ">
14 pages, 3942 KiB  
Article
Poly(ε-Caprolactone) Hollow Fiber Membranes for the Biofabrication of a Vascularized Human Liver Tissue
by Simona Salerno, Franco Tasselli, Enrico Drioli and Loredana De Bartolo
Membranes 2020, 10(6), 112; https://doi.org/10.3390/membranes10060112 - 27 May 2020
Cited by 21 | Viewed by 3679
Abstract
The creation of a liver tissue that recapitulates the micro-architecture and functional complexity of a human organ is still one of the main challenges of liver tissue engineering. Here we report on the development of a 3D vascularized hepatic tissue based on biodegradable [...] Read more.
The creation of a liver tissue that recapitulates the micro-architecture and functional complexity of a human organ is still one of the main challenges of liver tissue engineering. Here we report on the development of a 3D vascularized hepatic tissue based on biodegradable hollow fiber (HF) membranes of poly(ε-caprolactone) (PCL) that compartmentalize human hepatocytes on the external surface and between the fibers, and endothelial cells into the fiber lumen. To this purpose, PCL HF membranes were prepared by a dry-jet wet phase inversion spinning technique tailoring the operational parameters in order to obtain fibers with suitable properties. After characterization, the fibers were applied to generate a human vascularized hepatic unit by loading endothelial cells in their inner surface and hepatocytes on the external surface. The unit was connected to a perfusion system, and the morpho-functional behavior was evaluated. The results demonstrated the large integration of endothelial cells with the internal surface of individual PCL fibers forming vascular-like structures, and hepatocytes covered completely the external surface and the space between fibers. The perfused 3D hepatic unit retained its functional activity at high levels up to 18 days. This bottom-up tissue engineering approach represents a rational strategy to create relatively 3D vascularized tissues and organs. Full article
(This article belongs to the Special Issue Membranes: 10th Anniversary)
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<p>Poly(ε-caprolactone) (PCL) hollow fiber (HF) membrane bioreactor and scheme of the 3D human hepatic tissue realized by culturing human hepatocytes over and between PCL HF membranes parallel assembled at a distance of 250 µm, and endothelial cells compartmentalized in the lumen of the fibers. The cells were in communication through the porous wall of the membranes.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) pictures of: (<b>a</b>) cross-section, (<b>b</b>) wall thickness, (<b>c</b>) extracapillary surface, and (<b>d</b>) lumen surface of PCL HF membranes.</p> Full article ">Figure 3
<p>(<b>a</b>) Hydraulic permeation measurements of PCL HF membranes at different transmembrane pressures <b>Δ</b>P<span class="html-italic"><sup>™</sup></span>. Experimental values were averaged on 10 measurements; the interpolation of experimental data is reported as a solid line: slope (hydraulic permeance): 0.238 L/m<sup>2</sup>·h mbar; R-squared value: 0.98. Concentration appearance profiles of (<b>b</b>) glucose, (<b>c</b>) albumin, and (<b>d</b>) apotransferrin permeating PCL HF membranes at constant transmembrane pressure <b>Δ</b>P<span class="html-italic"><sup>™</sup></span> 40 mbar.</p> Full article ">Figure 4
<p>Mechanical properties of PCL HF membranes in dry and wet conditions. The values are the means of 10 measurements per sample ±SD.</p> Full article ">Figure 5
<p>SEM pictures of primary human hepatocytes and human endothelial cells after 18 days of culture in PCL HF membrane bioreactor: (<b>a</b>,<b>c</b>,<b>e</b>) endothelial cells in the intraluminal compartment; (<b>b</b>,<b>d</b>,<b>f</b>) hepatocytes over and between fibers in the extraluminal compartment.</p> Full article ">Figure 6
<p>Confocal Laser Scanning Microscopy (CLSM) images of primary human hepatocytes and human endothelial cells after 18 days of culture in PCL HF membrane bioreactor. Endothelial cells in the intraluminal compartment were visualized for CD31 (red); hepatocytes over and between the fibers in the extraluminal compartment were stained for actin (green), CK19 (magenta), and nuclei (blue).</p> Full article ">Figure 7
<p>Glucose consumption (<b>a</b>), albumin (<b>b</b>) and urea (<b>c</b>) synthesis by primary human hepatocytes cultured in the PCL HF membrane bioreactor with human endothelial cells (EC-hep) in comparison to homotypic culture of only hepatocytes (hep). The values are the mean ± standard deviations of three experiments per configurations. Data statistically significant according Student <span class="html-italic">t</span>-test: (*) <span class="html-italic">p</span> &lt; 0.05; (§) <span class="html-italic">p</span> &lt; 0.01.</p> Full article ">Figure 8
<p>Diazepam biotransformation by primary human hepatocytes cultured in the PCL HF membrane bioreactor with human endothelial cells: temazepam (TMZ), nordiazepam (NDZ), 4-hydroxydiazepam (4-OH) and oxazepam (OXZ). The values are the mean ± standard deviations of three experiments.</p> Full article ">
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