Membranes

34 pages, 3611 KiB

Open AccessReview

Ceramic Microfiltration Membranes in Wastewater Treatment: Filtration Behavior, Fouling and Prevention

by Mohammed Wali Hakami, Abdullah Alkhudhiri, Sirhan Al-Batty, Myrto-Panagiota Zacharof, Jon Maddy and Nidal Hilal

Membranes 2020, 10(9), 248; https://doi.org/10.3390/membranes10090248 - 22 Sep 2020

Cited by 68 | Viewed by 11708

Abstract

Nowadays, integrated microfiltration (MF) membrane systems treatment is becoming widely popular due to its feasibility, process reliability, commercial availability, modularity, relative insensitivity in case of wastewater of various industrial sources as well as raw water treatment and lower operating costs. The well thought [...] Read more.

Nowadays, integrated microfiltration (MF) membrane systems treatment is becoming widely popular due to its feasibility, process reliability, commercial availability, modularity, relative insensitivity in case of wastewater of various industrial sources as well as raw water treatment and lower operating costs. The well thought out, designed and implemented use of membranes can decrease capital cost, reduce chemical usage, and require little maintenance. Due to their resistance to extreme operating conditions and cleaning protocols, ceramic MF membranes are gradually becoming more employed in the drinking water and wastewater treatment industries when compared with organic and polymeric membranes. Regardless of their many advantages, during continuous operation these membranes are susceptible to a fouling process that can be detrimental for successful and continuous plant operations. Chemical and microbial agents including suspended particles, organic matter particulates, microorganisms and heavy metals mainly contribute to fouling, a complex multifactorial phenomenon. Several strategies, such as chemical cleaning protocols, turbulence promoters and backwashing with air or liquids are currently used in the industry, mainly focusing around early prevention and treatment, so that the separation efficiency of MF membranes will not decrease over time. Other strategies include combining coagulation with either inorganic or organic coagulants, with membrane treatment which can potentially enhance pollutants retention and reduce membrane fouling. Full article

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

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9 pages, 1609 KiB

Open AccessArticle

Simultaneous Quantification of Protein Binding Kinetics in Whole Cells with Surface Plasmon Resonance Imaging and Edge Deformation Tracking

by Wenwen Jing, Ashley Hunt, Nongjian Tao, Fenni Zhang and Shaopeng Wang

Membranes 2020, 10(9), 247; https://doi.org/10.3390/membranes10090247 - 22 Sep 2020

Cited by 9 | Viewed by 2735

Abstract

Most drugs work by binding to receptors on the cell surface. Quantification of binding kinetics between drug and membrane protein is an essential step in drug discovery. Current methods for measuring binding kinetics involve extracting the membrane protein and labeling, and both have [...] Read more.

Most drugs work by binding to receptors on the cell surface. Quantification of binding kinetics between drug and membrane protein is an essential step in drug discovery. Current methods for measuring binding kinetics involve extracting the membrane protein and labeling, and both have issues. Surface plasmon resonance (SPR) imaging has been demonstrated for quantification of protein binding to cells with single-cell resolution, but it only senses the bottom of the cell and the signal diminishes with the molecule size. We have discovered that ligand binding to the cell surface is accompanied by a small cell membrane deformation, which can be used to measure the binding kinetics by tracking the cell edge deformation. Here, we report the first integration of SPR imaging and cell edge tracking methods in a single device, and we use lectin interaction as a model system to demonstrate the capability of the device. The integration enables the simultaneous collection of complementary information provided by both methods. Edge tracking provides the advantage of small molecule binding detection capability, while the SPR signal scales with the ligand mass and can quantify membrane protein density. The kinetic constants from the two methods were cross-validated and found to be in agreement at the single-cell level. The variation of observed rate constant between the two methods is about 0.009 s⁻¹, which is about the same level as the cell-to-cell variations. This result confirms that both methods can be used to measure whole-cell binding kinetics, and the integration improves the reliability and capability of the measurement. Full article

(This article belongs to the Special Issue Protein-Lipid Interactions as Key Regulators of Cell Function)

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16 pages, 4837 KiB

Open AccessArticle

Viscosity Modification of Polymerizable Bicontinuous Microemulsion by Controlled Radical Polymerization for Membrane Coating Applications

by Ephraim Gukelberger, Christian Hitzel, Raffaella Mancuso, Francesco Galiano, Mauro Daniel Luigi Bruno, Roberto Simonutti, Bartolo Gabriele, Alberto Figoli and Jan Hoinkis

Membranes 2020, 10(9), 246; https://doi.org/10.3390/membranes10090246 - 21 Sep 2020

Cited by 6 | Viewed by 2202

Abstract

Membrane modification is becoming ever more relevant for mitigating fouling phenomena within wastewater treatment applications. Past research included a novel low-fouling coating using polymerizable bicontinuous microemulsion (PBM) induced by UV-LED polymerization. This additional cover layer deteriorated the filtration capacity significantly, potentially due to [...] Read more.

Membrane modification is becoming ever more relevant for mitigating fouling phenomena within wastewater treatment applications. Past research included a novel low-fouling coating using polymerizable bicontinuous microemulsion (PBM) induced by UV-LED polymerization. This additional cover layer deteriorated the filtration capacity significantly, potentially due to the observed high pore intrusion of the liquid PBM prior to the casting process. Therefore, this work addressed an innovative experimental protocol for controlling the viscosity of polymerizable bicontinuous microemulsions (PBM) before casting on commercial ultrafiltration (UF) membranes. Prior to the coating procedure, the PBM viscosity modulation was carried out by controlled radical polymerization (CRP). The regulation was conducted by introducing the radical inhibitor 2,2,6,6-tetramethylpiperidine 1-oxyl after a certain time (CRP time). The ensuing controlled radical polymerized PBM (CRP-PBM) showed a higher viscosity than the original unpolymerized PBM, as confirmed by rheological measurements. Nevertheless, the resulting CRP-PBM-cast membranes had a lower permeability in water filtration experiments despite a higher viscosity and potentially lower pore intrusion. This result is due to different polymeric structures of the differently polymerized PBM, as confirmed by solid-state nuclear magnetic resonance (NMR) investigations. The findings can be useful for future developments in the membrane science field for production of specific membrane-coating layers for diverse applications. Full article

(This article belongs to the Section Membrane Chemistry)

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14 pages, 1505 KiB

Open AccessArticle

Electrodialytic Desalination of Tobacco Sheet Extract: Membrane Fouling Mechanism and Mitigation Strategies

by Shaolin Ge, Zhao Zhang, Haiyang Yan, Muhammad Irfan, Yingbo Xu, Wei Li, Huangying Wang and Yaoming Wang

Membranes 2020, 10(9), 245; https://doi.org/10.3390/membranes10090245 - 21 Sep 2020

Cited by 15 | Viewed by 2833

Abstract

In the papermaking industry (reconstituted tobacco), a large number of tobacco stems, dust, and fines are discharged in the wastewater. This high salinity wastewater rich in ionic constituents and nicotine is difficult to be degraded by conventional biological treatment and is a serious [...] Read more.

In the papermaking industry (reconstituted tobacco), a large number of tobacco stems, dust, and fines are discharged in the wastewater. This high salinity wastewater rich in ionic constituents and nicotine is difficult to be degraded by conventional biological treatment and is a serious threat that needs to be overcome. Electrodialysis (ED) has proved a feasible technique to remove the inorganic components in the papermaking wastewater. However, the fouling in ion exchange membranes causes deterioration of membranes, which causes a decrease in the flux and an increase in the electrical resistance of the membranes. In this study, the fouling potential of the membranes was analyzed by comparing the properties of the pristine and fouled ion exchange membranes. The physical and chemical properties of the ion exchange membranes were investigated in terms of electrical resistance, water content, and ion exchange capacity, as well as studied by infrared spectroscopy (IR) spectra, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analyses. The results indicated that the membrane fouling is caused by two different mechanisms. For the anion exchange membranes, the fouling is mainly caused by the charged organic anions. For the cation exchange membrane, the fouling is caused by minerals such as Ca²⁺ and Mg²⁺. These metal ions reacted with OH⁻ ions generated by water dissociation and precipitated on the membrane surface. The chemical cleaning with alkaline and acid could mitigate the fouling potential of the ion exchange membranes. Full article

(This article belongs to the Special Issue Membrane Technologies for Sustainable Biofood Production Lines)

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8 pages, 2265 KiB

Open AccessCommunication

Lactic Acid Permeation through Deep Eutectic Solvents-Based Polymer Inclusion Membranes

by Michiaki Matsumoto, Sae Takemori and Yoshiro Tahara

Membranes 2020, 10(9), 244; https://doi.org/10.3390/membranes10090244 - 19 Sep 2020

Cited by 9 | Viewed by 2801

Abstract

Lactic acid that is prepared by fermentation is a compound in food, cosmetic pharmaceutical, and chemical industries. Since a simple technique is desired that separates lactic acid from the cultures, we propose lactic acid permeation through a poly(vinyl chloride)(PVC)-based membrane that contains deep [...] Read more.

Lactic acid that is prepared by fermentation is a compound in food, cosmetic pharmaceutical, and chemical industries. Since a simple technique is desired that separates lactic acid from the cultures, we propose lactic acid permeation through a poly(vinyl chloride)(PVC)-based membrane that contains deep eutectic solvents (DESs) as a carrier. Lactic acid was successfully permeated through polymer inclusion membranes (PIMs) containing hydrophilic DESs, urea-choline chloride and glucose-choline chloride. The permeation behavior was explained by the facilitated transport mechanism based on the solution-diffusion model. Simple preparation of thinner membranes in the PIM process and higher permeation rates are advantages over the supported liquid membrane process. The PVC-based membrane process containing environmentally benign hydrophilic DESs is promising for lactic acid separation on an industrial scale. Full article

(This article belongs to the Special Issue Polymer Inclusion Membranes)

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16 pages, 2430 KiB

Open AccessArticle

Effect of Membrane Fouling on Fertilizer-Drawn Forward Osmosis Desalination Performance

by Majeda Khraisheh, Mona Gulied and Fares AlMomani

Membranes 2020, 10(9), 243; https://doi.org/10.3390/membranes10090243 - 18 Sep 2020

Cited by 8 | Viewed by 3366

Abstract

Fertilizer-drawn forward osmosis (FDFO) has garnered immense attention for its application in the agricultural field and its potential to reuse wastewater sustainably. Membrane fouling, however, remains to be a challenge for the process. This study aims to investigate the influence of membrane fouling [...] Read more.

Fertilizer-drawn forward osmosis (FDFO) has garnered immense attention for its application in the agricultural field and its potential to reuse wastewater sustainably. Membrane fouling, however, remains to be a challenge for the process. This study aims to investigate the influence of membrane fouling on the performance of the FDFO process. Synthetic wastewater (SWW) and multi-component fertilizer (MCF) were used as feed solution (FS) and draw solution (DS) with cellulose triacetate (CTA) forward osmosis (FO) membrane orientation. The performance was evaluated through water flux (WF), percentage recovery and percentage of salt reject. The WF declined from 10.32 LMH (L/m²·h) to 3.30 LMH when ultra-pure water as FS was switched with concentration FS indicating the dependence of the performance on the type of FS used. Accelerated fouling experiments conducted to verify the fouling behavior showed a decline in the water flux from 8.6 LMH to 3.09 LMH with SWW and 13.1 LMH to 3.42 LMH when deionized water was used as FS. The effects of osmotic backwashing and in situ flushing as physical cleaning methods of the foul membrane were studied through water flux and salt recovery percentage. Both cleaning methods yielded a WF close to the baseline. Osmotic backwashing yielded better results by eliminating foulant–foulant and foulant–membrane adhesion. The cleaning methods were able to recover 75% of phosphate and 60% of nitrate salts. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) results validated the effectiveness of the methods for the physical cleaning of foul membranes. This study underlines the importance of the FS used in FDFO and the effectiveness of osmotic backwashing as a cleaning method of FO membranes. Full article

(This article belongs to the Special Issue Membrane Surface Modification and Functionalization)

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46 pages, 4504 KiB

Open AccessReview

Cu Homeostasis in Bacteria: The Ins and Outs

by Andreea Andrei, Yavuz Öztürk, Bahia Khalfaoui-Hassani, Juna Rauch, Dorian Marckmann, Petru-Iulian Trasnea, Fevzi Daldal and Hans-Georg Koch

Membranes 2020, 10(9), 242; https://doi.org/10.3390/membranes10090242 - 18 Sep 2020

Cited by 56 | Viewed by 7859

Abstract

Copper (Cu) is an essential trace element for all living organisms and used as cofactor in key enzymes of important biological processes, such as aerobic respiration or superoxide dismutation. However, due to its toxicity, cells have developed elaborate mechanisms for Cu homeostasis, which [...] Read more.

Copper (Cu) is an essential trace element for all living organisms and used as cofactor in key enzymes of important biological processes, such as aerobic respiration or superoxide dismutation. However, due to its toxicity, cells have developed elaborate mechanisms for Cu homeostasis, which balance Cu supply for cuproprotein biogenesis with the need to remove excess Cu. This review summarizes our current knowledge on bacterial Cu homeostasis with a focus on Gram-negative bacteria and describes the multiple strategies that bacteria use for uptake, storage and export of Cu. We furthermore describe general mechanistic principles that aid the bacterial response to toxic Cu concentrations and illustrate dedicated Cu relay systems that facilitate Cu delivery for cuproenzyme biogenesis. Progress in understanding how bacteria avoid Cu poisoning while maintaining a certain Cu quota for cell proliferation is of particular importance for microbial pathogens because Cu is utilized by the host immune system for attenuating pathogen survival in host cells. Full article

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

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11 pages, 4926 KiB

Open AccessArticle

A Molecular Dynamics Investigation of the Temperature Effect on the Mechanical Properties of Selected Thin Films for Hydrogen Separation

by Sunday Temitope Oyinbo and Tien-Chien Jen

Membranes 2020, 10(9), 241; https://doi.org/10.3390/membranes10090241 - 18 Sep 2020

Cited by 3 | Viewed by 2327

Abstract

In this study, we performed nanoindentation test using the molecular dynamic (MD) approach on a selected thin film of palladium, vanadium, copper and niobium coated on the vanadium substrate at a loading rate of 0.5 Å/ps. The thermosetting control is applied with temperature [...] Read more.

In this study, we performed nanoindentation test using the molecular dynamic (MD) approach on a selected thin film of palladium, vanadium, copper and niobium coated on the vanadium substrate at a loading rate of 0.5 Å/ps. The thermosetting control is applied with temperature variance from 300 to 700 K to study the mechanical characteristics of the selected thin films. The effects of temperature on the structure of the material, piling-up phenomena and sinking-in occurrence were considered. The simulation results of the analysis and the experimental results published in this literature were well correlated. The analysis of temperature demonstrated an understanding of the impact of the behaviour. As the temperature decreases, the indentation load increases for loading and unloading processes. Hence, this increases the strength of the material. In addition, the results demonstrate that the modulus of elasticity and thin-film hardness decreases in the order of niobium, vanadium, copper and palladium as the temperature increases. Full article

(This article belongs to the Section Inorganic Membranes)

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24 pages, 6986 KiB

Open AccessArticle

Ionic Polyureas—A Novel Subclass of Poly(Ionic Liquid)s for CO₂ Capture

by Sofia M. Morozova, Elena I. Lozinskaya, Haritz Sardon, Fabian Suárez-García, Petr S. Vlasov, Régis Vaudemont, Yakov S. Vygodskii and Alexander S. Shaplov

Membranes 2020, 10(9), 240; https://doi.org/10.3390/membranes10090240 - 18 Sep 2020

Cited by 8 | Viewed by 2776

Abstract

The growing concern for climate change and global warming has given rise to investigations in various research fields, including one particular area dedicated to the creation of solid sorbents for efficient CO₂ capture. In this work, a new family of poly(ionic liquid)s [...] Read more.

The growing concern for climate change and global warming has given rise to investigations in various research fields, including one particular area dedicated to the creation of solid sorbents for efficient CO₂ capture. In this work, a new family of poly(ionic liquid)s (PILs) comprising cationic polyureas (PURs) with tetrafluoroborate (BF₄) anions has been synthesized. Condensation of various diisocyanates with novel ionic diamines and subsequent ion metathesis reaction resulted in high molar mass ionic PURs (M_w = 12 ÷ 173 × 10³ g/mol) with high thermal stability (up to 260 °C), glass transition temperatures in the range of 153–286 °C and remarkable CO₂ capture (10.5–24.8 mg/g at 0 °C and 1 bar). The CO₂ sorption was found to be dependent on the nature of the cation and structure of the diisocyanate. The highest sorption was demonstrated by tetrafluoroborate PUR based on 4,4′-methylene-bis(cyclohexyl isocyanate) diisocyanate and aromatic diamine bearing quinuclidinium cation (24.8 mg/g at 0 °C and 1 bar). It is hoped that the present study will inspire novel design strategies for improving the sorption properties of PILs and the creation of novel effective CO₂ sorbents. Full article

(This article belongs to the Special Issue Ionic Liquid-based Materials for Membrane Processes)

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18 pages, 3423 KiB

Open AccessArticle

Impact of MWCO and Dopamine/Polyethyleneimine Concentrations on Surface Properties and Filtration Performance of Modified Membranes

by Mariane Carolina Proner, Ingrid Ramalho Marques, Alan Ambrosi, Katia Rezzadori, Cristiane da Costa, Guilherme Zin, Marcus Vinícius Tres and Marco Di Luccio

Membranes 2020, 10(9), 239; https://doi.org/10.3390/membranes10090239 - 18 Sep 2020

Cited by 19 | Viewed by 3513

Abstract

The mussel-inspired method has been investigated to modify commercial ultrafiltration membranes to induce antifouling characteristics. Such features are essential to improve the feasibility of using membrane processes in protein recovery from waste streams, wastewater treatment, and reuse. However, some issues still need to [...] Read more.

The mussel-inspired method has been investigated to modify commercial ultrafiltration membranes to induce antifouling characteristics. Such features are essential to improve the feasibility of using membrane processes in protein recovery from waste streams, wastewater treatment, and reuse. However, some issues still need to be clarified, such as the influence of membrane pore size and the polymer concentration used in modifying the solution. The aim of the present work is to study a one-step deposition of dopamine (DA) and polyethyleneimine (PEI) on ultrafiltration membrane surfaces. The effects of different membrane molecular weight cut-offs (MWCO, 20, 30, and 50 kDa) and DA/PEI concentrations on membrane performance were assessed by surface characterization (FTIR, AFM, zeta potential, contact angle, protein adsorption) and permeation of protein solution. Results indicate that larger MWCO membranes (50 kDa) are most benefited by modification using DA and PEI. Moreover, PEI is primarily responsible for improving membrane performance in protein solution filtration. The membrane modified with 0.5:4.0 mg mL⁻¹ (DA: PEI) presented a better performance in protein solution filtration, with only 15% of permeate flux drop after 2 h of filtration. The modified membrane can thus be potentially applied to the recovery of proteins from waste streams. Full article

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

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14 pages, 2039 KiB

Open AccessArticle

Impacts of Natural Organic Matter Adhesion on Irreversible Membrane Fouling during Surface Water Treatment Using Ultrafiltration

by Fangshu Qu, Zhimeng Yang, Shanshan Gao, Huarong Yu, Junguo He, Hongwei Rong and Jiayu Tian

Membranes 2020, 10(9), 238; https://doi.org/10.3390/membranes10090238 - 17 Sep 2020

Cited by 11 | Viewed by 2655

Abstract

To understand impacts of organic adhesion on membrane fouling, ultrafiltration (UF) membrane fouling by dissolved natural organic matter (NOM) was investigated in the presence of background cations (Na⁺ and Ca²⁺) at typical concentrations in surface water. Moreover, NOM adhesion on [...] Read more.

To understand impacts of organic adhesion on membrane fouling, ultrafiltration (UF) membrane fouling by dissolved natural organic matter (NOM) was investigated in the presence of background cations (Na⁺ and Ca²⁺) at typical concentrations in surface water. Moreover, NOM adhesion on the UF membrane was investigated using atomic force microscopy (AFM) with colloidal probes and a quartz crystal microbalance with dissipation monitoring (QCM-D). The results indicated that the adhesion forces at the NOM-membrane interface increased in the presence of background cations, particularly Ca²⁺, and that the amount of adhered NOM increased due to reduced electrostatic repulsion. However, the membrane permeability was almost not affected by background cations in the pore blocking-dominated phase but was aggravated to some extent in the cake filtration-governed phase. More importantly, the irreversible NOM fouling was not correlated with the amount of adhered NOM. The assumption for membrane autopsies is doubtful that retained or adsorbed organic materials are necessarily a primary cause of membrane fouling, particularly the irreversible fouling. Full article

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

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19 pages, 4222 KiB

Open AccessArticle

Antifouling Property of Oppositely Charged Titania Nanosheet Assembled on Thin Film Composite Reverse Osmosis Membrane for Highly Concentrated Oily Saline Water Treatment

by Nor Akalili Ahmad, Pei Sean Goh, Abdul Karim Zulhairun and Ahmad Fauzi Ismail

Membranes 2020, 10(9), 237; https://doi.org/10.3390/membranes10090237 - 16 Sep 2020

Cited by 16 | Viewed by 3748

Abstract

With the blooming of oil and gas industries, oily saline wastewater treatment becomes a viable option to resolve the oily water disposal issue and to provide a source of water for beneficial use. Reverse osmosis (RO) has been touted as a promising technology [...] Read more.

With the blooming of oil and gas industries, oily saline wastewater treatment becomes a viable option to resolve the oily water disposal issue and to provide a source of water for beneficial use. Reverse osmosis (RO) has been touted as a promising technology for oily saline wastewater treatment. However, one great challenge of RO membrane is fouling phenomena, which is caused by the presence of hydrocarbon contents in the oily saline wastewater. This study focuses on the fabrication of antifouling RO membrane for accomplishing simultaneous separation of salt and oil. Thin film nanocomposite (TFN) RO membrane was formed by the layer by layer (LbL) assembly of positively charged TNS (pTNS) and negatively charged TNS (nTNS) on the surface of thin film composite (TFC) membrane. The unique features, rendered by hydrophilic TNS bilayer assembled on TFC membrane in the formation of a hydration layer to enhance the fouling resistance by high concentration oily saline water while maintaining the salt rejection, were discussed in this study. The characterization findings revealed that the surface properties of membrane were improved in terms of surface hydrophilicity, surface roughness, and polyamide(PA) cross-linking. The TFC RO membrane coated with 2-bilayer of TNS achieved >99% and >98% for oil and salt rejection, respectively. During the long-term study, the 2TNS-PA TFN membrane outperformed the pristine TFC membrane by exhibiting high permeability and much lower fouling propensity for low to high concentration of oily saline water concentration (1000 ppm, 5000 ppm and 10,000 ppm) over a 960 min operation. Meanwhile, the average permeability of uncoated TFC membrane could only be recovered by 95.7%, 89.1% and 82.9% for 1000 ppm, 5000 ppm and 10,000 ppm of the oily saline feedwater, respectively. The 2TNS-PA TFN membrane achieved almost 100% flux recovery for three cycles by hydraulic washing. Full article

(This article belongs to the Special Issue Advances in Reverse Osmosis Membranes and Processes)

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12 pages, 2973 KiB

Open AccessArticle

Transmembrane Facilitation of Lactate/H⁺ Instead of Lactic Acid Is Not a Question of Semantics but of Cell Viability

by Annika Bader and Eric Beitz

Membranes 2020, 10(9), 236; https://doi.org/10.3390/membranes10090236 - 15 Sep 2020

Cited by 14 | Viewed by 3377

Abstract

Transmembrane transport of monocarboxylates is conferred by structurally diverse membrane proteins. Here, we describe the pH dependence of lactic acid/lactate facilitation of an aquaporin (AQP9), a monocarboxylate transporter (MCT1, SLC16A1), and a formate–nitrite transporter (plasmodium falciparum FNT, PfFNT) in the equilibrium transport state. [...] Read more.

Transmembrane transport of monocarboxylates is conferred by structurally diverse membrane proteins. Here, we describe the pH dependence of lactic acid/lactate facilitation of an aquaporin (AQP9), a monocarboxylate transporter (MCT1, SLC16A1), and a formate–nitrite transporter (plasmodium falciparum FNT, PfFNT) in the equilibrium transport state. FNTs exhibit a channel-like structure mimicking the aquaporin-fold, yet act as secondary active transporters. We used radiolabeled lactate to monitor uptake via yeast-expressed AQP9, MCT1, and PfFNT for long enough time periods to reach the equilibrium state in which import and export rates are balanced. We confirmed that AQP9 behaved perfectly equilibrative for lactic acid, i.e., the neutral lactic acid molecule enters and passes the channel. MCT1, in turn, actively used the transmembrane proton gradient and acted as a lactate/H⁺ co-transporter. PfFNT behaved highly similar to the MCT in terms of transport properties, although it does not adhere to the classical alternating access transporter model. Instead, the FNT appears to use the proton gradient to neutralize the lactate anion in the protein’s vestibule to generate lactic acid in a place that traverses the central hydrophobic transport path. In conclusion, we propose to include FNT-type proteins into a more generalized, function-based transporter definition. Full article

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

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20 pages, 4201 KiB

Open AccessArticle

Effect of pH on Total Volume Membrane Charge Density in the Nanofiltration of Aqueous Solutions of Nitrate Salts of Heavy Metals

by Agata Marecka-Migacz, Piotr Tomasz Mitkowski, Arkadiusz Nędzarek, Jacek Różański and Waldemar Szaferski

Membranes 2020, 10(9), 235; https://doi.org/10.3390/membranes10090235 - 14 Sep 2020

Cited by 13 | Viewed by 2678

Abstract

The separation efficiencies of aqueous solutions containing nitric salts of Zn, Cu, Fe or Pb at various pH in process of nanofiltration have been investigated experimentally. These results were used to obtain the total volume membrane charge densities, through mathematical modelling based on [...] Read more.

The separation efficiencies of aqueous solutions containing nitric salts of Zn, Cu, Fe or Pb at various pH in process of nanofiltration have been investigated experimentally. These results were used to obtain the total volume membrane charge densities, through mathematical modelling based on the Donnan–Steric partitioning Model. The experimentally obtained retention values of individual heavy metal ions varied between 36% (Zn²⁺ at pH = 2), 57% (Pb²⁺ at pH = 2), 80% (Fe³⁺ at pH = 9), and up to 97% (Cu²⁺ at pH = 9). The mathematical modelling allowed for fitting the total volume membrane charge density (X_d), which yielded values ranging from −451.90 to +900.16 mol/m³ for different non-symmetric ions. This study presents the application of nanofiltration (NF) modelling, including a consideration of each ion present in the NF system—even those originating from solutions used to adjust the pH values of the feed. Full article

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

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25 pages, 3715 KiB

Open AccessArticle

CO₂ Desorption Performance from Imidazolium Ionic Liquids by Membrane Vacuum Regeneration Technology

by Jose Manuel Vadillo, Lucia Gómez-Coma, Aurora Garea and Angel Irabien

Membranes 2020, 10(9), 234; https://doi.org/10.3390/membranes10090234 - 14 Sep 2020

Cited by 12 | Viewed by 2762

Abstract

In this work, the membrane vacuum regeneration (MVR) process was considered as a promising technology for solvent regeneration in post-combustion CO₂ capture and utilization (CCU) since high purity CO₂ is needed for a technical valorization approach. First, a desorption test by [...] Read more.

In this work, the membrane vacuum regeneration (MVR) process was considered as a promising technology for solvent regeneration in post-combustion CO₂ capture and utilization (CCU) since high purity CO₂ is needed for a technical valorization approach. First, a desorption test by MVR using polypropylene hollow fiber membrane contactor (PP-HFMC) was carried out in order to evaluate the behavior of physical and physico-chemical absorbents in terms of CO₂ solubility and regeneration efficiency. The ionic liquid 1-ethyl-3-methylimidazolium acetate, [emim][Ac], was presented as a suitable alternative to conventional amine-based absorbents. Then, a rigorous two-dimensional mathematical model of the MVR process in a HFMC was developed based on a pseudo-steady-state to understand the influence of the solvent regeneration process in the absorption–desorption process. CO₂ absorption–desorption experiments in PP-HFMC at different operating conditions for desorption, varying vacuum pressure and temperature, were used for model validation. Results showed that MVR efficiency increased from 3% at room temperature and 500 mbar to 95% at 310K and 40 mbar vacuum. Moreover, model deviation studies were carried out using sensitivity analysis of Henry’s constant and pre-exponential factor of chemical interaction, thus as to contribute to the knowledge in further works. Full article

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12 pages, 1268 KiB

Open AccessArticle

Beverage–Drug Interaction: Effects of Green Tea Beverage Consumption on Atorvastatin Metabolism and Membrane Transporters in the Small Intestine and Liver of Rats

by Hsien-Tsung Yao, Ya-Ru Hsu and Mei-Ling Li

Membranes 2020, 10(9), 233; https://doi.org/10.3390/membranes10090233 - 14 Sep 2020

Cited by 5 | Viewed by 3371

Abstract

Green tea (GT) beverages are popular worldwide and may prevent the development of many chronic diseases including cardiovascular disease and cancer. To investigate whether the consumption of a GT beverage causes drug interactions, the effects of GT beverage consumption on atorvastatin metabolism and [...] Read more.

Green tea (GT) beverages are popular worldwide and may prevent the development of many chronic diseases including cardiovascular disease and cancer. To investigate whether the consumption of a GT beverage causes drug interactions, the effects of GT beverage consumption on atorvastatin metabolism and membrane transporters were evaluated. Male rats were fed a chow diet with tap water or the GT beverage for 3 weeks. Then, the rats were given a single oral dose (10 mg/kg body weight (BW)) of atorvastatin (ATV), and blood was collected at various time points within 6 h. The results show that GT consumption increased the plasma concentrations (AUC_0–6h) of ATV (+85%) and 2-OH ATV (+93.3%). GT also increased the 2-OH ATV (+40.9%) and 4-OH ATV (+131.6%) contents in the liver. Decreased cytochrome P450 (CYP) 3A enzyme activity, with no change in P-glycoprotein expression in the intestine, was observed in rats treated with GT. Additionally, GT increased hepatic CYP3A-mediated ATV metabolism and decreased organic anion transporting polypeptides (OATP) 2 membrane protein expression. There was no significant difference in the membrane protein expression of OATP2B1 and P-glycoprotein in the intestine and liver after the GT treatment. The results show that GT consumption may lower hepatic OATP2 and, thus, limit hepatic drug uptake and increase plasma exposure to ATV and 2-OH ATV. Full article

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

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17 pages, 6281 KiB

Open AccessArticle

The Synthesis and Characterization of Novel Bi-/Trimetallic Nanoparticles and Their Nanocomposite Membranes for Envisaged Water Treatment

by Lwazi Ndlwana, Keneiloe Sikhwivhilu, Richard Motlhaletsi Moutloali and Jane Catherine Ngila

Membranes 2020, 10(9), 232; https://doi.org/10.3390/membranes10090232 - 14 Sep 2020

Cited by 9 | Viewed by 2523

Abstract

The impact of worldwide water scarcity, further exacerbated by environmental pollution, necessitates the development of effective water treatment membranes. Herein, we report the synthesis and characterization of nanocomposite membranes containing hyperbranched polyethyleneimine (HPEI) stabilized bi-and trimetallic nanoparticles. These membranes were prepared by blending [...] Read more.

The impact of worldwide water scarcity, further exacerbated by environmental pollution, necessitates the development of effective water treatment membranes. Herein, we report the synthesis and characterization of nanocomposite membranes containing hyperbranched polyethyleneimine (HPEI) stabilized bi-and trimetallic nanoparticles. These membranes were prepared by blending a pre-grafted Polyethersulfone (PES) powder with the Pd@Fe@HPEI and Pd@FeAg@HPEI nanoparticles followed by phase inversion. The membranes, together with stabilized nanoparticles, were characterized by several analytical techniques, such as attenuated total reflectance–Fourier transform infra-red spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), optical contact angle (OCA), scanning electron microscopy (SEM), atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HRTEM). These techniques revealed the elemental composition, zerovalent nature of the nanoparticles, and their small and even size distribution. Surface analysis showed chemical bonding between the polymeric functional groups and the supported nanoparticles. Furthermore, the nanocomposite membranes were found to be hydrophilic. Additionally, the membranes were investigated for swelling (water uptake), porosity, pore size, pure water permeation fluxes, and they indicated a decreased protein adhesion property. As such, the membranes fabricated in this work indicate the required properties for application in water treatment. Full article

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

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11 pages, 2491 KiB

Open AccessArticle

Long-Term Investigation into the Membrane Fouling Behavior in Anaerobic Membrane Bioreactors for Municipal Wastewater Treatment Operated at Two Different Temperatures

by Yi Ding, Zhansheng Guo, Zhenlin Liang, Xuguang Hou, Zhipeng Li, Dashuai Mu, Changzi Ge, Chunpeng Zhang and Chao Jin

Membranes 2020, 10(9), 231; https://doi.org/10.3390/membranes10090231 - 13 Sep 2020

Cited by 13 | Viewed by 2687

Abstract

In this study, the characteristics of activated sludge flocs were investigated and their effects on the evolution of membrane fouling were considered in the anaerobic membrane bioreactors (AnMBR), which were operated at 25 and 35 °C for municipal wastewater treatment. It was found [...] Read more.

In this study, the characteristics of activated sludge flocs were investigated and their effects on the evolution of membrane fouling were considered in the anaerobic membrane bioreactors (AnMBR), which were operated at 25 and 35 °C for municipal wastewater treatment. It was found that the membrane fouling rate of the AnMBR at 25 °C was more severe than that at 35 °C. The membrane fouling trends were not consistent with the change in the concentration of soluble microbial product (SMP). The larger amount of SMP in the AnMBR at 35 °C did not induce more severe membrane fouling than that in the AnMBR at 25 °C. However, the polysaccharide and protein concentration of extracellular polymeric substance (EPS) was higher in the AnMBR at 25 °C in comparison with that in the AnMBR at 35 °C, and the protein/polysaccharide ratio of the EPS in the AnMBR at 25 °C was higher in contrast to that in the AnMBR at 35 °C. Meanwhile, the fouling tendencies measured for the AnMBRs could be related to the characteristics of loosely bound EPS and tightly bound EPS. The analysis of the activated sludge flocs characteristics indicated that a smaller sludge particle size and more fine flocs were observed at the AnMBR with 25 °C. Therefore, the membrane fouling potential in the AnMBR could be explained by the characteristics of activated sludge flocs. Full article

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

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15 pages, 10782 KiB

Open AccessArticle

Is the Bacterial Cellulose Membrane Feasible for Osteopromotive Property?

by Ana Paula Farnezi Bassi, Vinícius Ferreira Bizelli, Leticia Freitas de Mendes Brasil, Járede Carvalho Pereira, Hesham Mohammed Al-Sharani, Gustavo Antonio Correa Momesso, Leonardo P. Faverani and Flavia de Almeida Lucas

Membranes 2020, 10(9), 230; https://doi.org/10.3390/membranes10090230 - 12 Sep 2020

Cited by 17 | Viewed by 2865

Abstract

Guided bone regeneration was studied to establish protocols and develop new biomaterials that revealed satisfactory results. The present study aimed to comparatively evaluate the efficiency of the bacterial cellulose membrane (Nanoskin^®) and collagen membrane Bio-Gide^® in the bone repair of [...] Read more.

Guided bone regeneration was studied to establish protocols and develop new biomaterials that revealed satisfactory results. The present study aimed to comparatively evaluate the efficiency of the bacterial cellulose membrane (Nanoskin^®) and collagen membrane Bio-Gide^® in the bone repair of 8-mm critical size defects in rat calvaria. Seventy-two adult male rats were divided into three experimental groups (n = 24): the CG—membrane-free control group (only blood clot, negative control), BG—porcine collagen membrane group (Bio-Guide^®, positive control), and BC—bacterial cellulose membrane group (experimental group). The comparison periods were 7, 15, 30, and 60 days postoperatively. Histological, histometric, and immunohistochemical analyses were performed. The quantitative data were subjected to 2-way ANOVA and Tukey’s post-test, and p < 0.05 was considered significant. At 30 and 60 days postoperatively, the BG group showed more healing of the surgical wound than the other groups, with a high amount of newly formed bone (p < 0.001), while the BC group showed mature connective tissue filling the defect. The inflammatory cell count at postoperative days 7 and 15 was higher in the BC group than in the BG group (Tukey’s test, p = 0.006). At postoperative days 30 and 60, the area of new bone formed was greater in the BG group than in the other groups (p < 0.001). Immunohistochemical analysis showed moderate and intense immunolabeling of osteocalcin and osteopontin at postoperative day 60 in the BG and BC groups. Thus, despite the promising application of the BC membrane in soft-tissue repair, it did not induce bone repair in rat calvaria. Full article

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

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11 pages, 2256 KiB

Open AccessArticle

Graphene Oxide Membrane Immobilized Aptamer as a Highly Selective Hormone Removal

by Siham Chergui, Khaled Rhili, Sujittra Poorahong and Mohamed Siaj

Membranes 2020, 10(9), 229; https://doi.org/10.3390/membranes10090229 - 12 Sep 2020

Cited by 8 | Viewed by 3074

Abstract

Three-dimensional (3D) reduced graphene oxide (rGO) modified by polyethyleneimine (PEI) was prepared and functionalized by fluorophore-labeled dexamethasone-aptamer (Flu-DEX-apt) via π–π stacking interaction. The rGO/PEI/Flu-DEX-apt was used as a selective membrane for dexamethasone hormone removal from water. The prepared rGO/PEI/Flu-DEX-apt membranes were stable, insoluble, [...] Read more.

Three-dimensional (3D) reduced graphene oxide (rGO) modified by polyethyleneimine (PEI) was prepared and functionalized by fluorophore-labeled dexamethasone-aptamer (Flu-DEX-apt) via π–π stacking interaction. The rGO/PEI/Flu-DEX-apt was used as a selective membrane for dexamethasone hormone removal from water. The prepared rGO/PEI/Flu-DEX-apt membranes were stable, insoluble, and easily removable from liquid media. The membrane was characterized by Raman spectroscopy, scanning electron spectroscopy, and FTIR spectroscopy. The rGO/PEI/Flu-DEX-apt membrane showed high sensitivity and specificity toward the dexamethasone hormone in the presence of other steroid hormone analogs, such as progesterone, estrone, estradiol, and 19-norethindrone. The fluorescence and UV–visible spectroscopy were used to confirm the membranes performance and the quantification of hormones removal. The resulting data clearly show that the graphene oxide concentration influence the aptamers and analytes interaction (π–π stacking interaction). It was found that by varying the graphene oxide concentration yields to different porosities of rGO/PEI/Flu-DEX-apt membranes affects the adsorption recovery rate, as well as the specificity and selectivity toward the dexamethasone hormone. Full article

(This article belongs to the Special Issue Advancements of 2D Materials-Based Membranes)

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19 pages, 4534 KiB

Open AccessArticle

Alkali Attack on Cation-Exchange Membranes with Polyvinyl Chloride Backing and Binder: Comparison with Anion-Exchange Membranes

by Shoichi Doi, Nobuya Takumi, Yuriko Kakihana and Mitsuru Higa

Membranes 2020, 10(9), 228; https://doi.org/10.3390/membranes10090228 - 11 Sep 2020

Cited by 9 | Viewed by 2434

Abstract

Systematic alkali immersion tests of cation-exchange membranes (CEM) with polyvinyl chloride (PVC) as their backing and binder were conducted to compare that of an Anion-exchange membrane (AEM) with the same PVC materials to investigate the mechanism of dehydrochlorination. In the immersion tests, originally [...] Read more.

Systematic alkali immersion tests of cation-exchange membranes (CEM) with polyvinyl chloride (PVC) as their backing and binder were conducted to compare that of an Anion-exchange membrane (AEM) with the same PVC materials to investigate the mechanism of dehydrochlorination. In the immersion tests, originally colorless and transparent AEM turned violet, and chemical structure analysis showed that polyene was produced by the dehydrochlorination reaction. However, the CEM did not change in color, chemical structure or membrane properties during the test with less than 1M alkali solutions. According to the Donnan equilibrium theory and the experiments using CEM and AEM, the hydroxide ion concentration in the CEM was much lower than that in the AEM under the same conditions. However, when the alkali immersion test was performed using the CEM under more severe conditions (6 M for 168 h at 40 °C), there was a slight change in the color and chemical structure of the CEM, clearly indicating that not only AEMs, but also CEMs with PVC matrixes were deteriorated by alkali, depending on the conditions. Full article

(This article belongs to the Special Issue Modelling and Experiment of Anion-Exchange Membranes)

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22 pages, 3003 KiB

Open AccessArticle

Comparison between a Conventional Anti-Biofouling Compound and a Novel Modified Low-Fouling Polyethersulfone Ultrafiltration Membrane: Bacterial Anti-Attachment, Water Quality and Productivity

by Norhan Nady, Noha Salem, Ranya Amer, Ahmed El-Shazly, Sherif H. Kandil and Mohamed Salah El-Din Hassouna

Membranes 2020, 10(9), 227; https://doi.org/10.3390/membranes10090227 - 10 Sep 2020

Cited by 3 | Viewed by 2450

Abstract

In this work, the efficiency of a conventional chlorination pretreatment is compared with a novel modified low-fouling polyethersulfone (PES) ultrafiltration (UF) membrane, in terms of bacteria attachment and membrane biofouling reduction. This study highlights the use of membrane modification as an effective strategy [...] Read more.

In this work, the efficiency of a conventional chlorination pretreatment is compared with a novel modified low-fouling polyethersulfone (PES) ultrafiltration (UF) membrane, in terms of bacteria attachment and membrane biofouling reduction. This study highlights the use of membrane modification as an effective strategy to reduce bacterial attachment, which is the initial step of biofilm formation, rather than using antimicrobial agents that can enhance bacterial regrowth. The obtained results revealed that the filtration of pretreated, inoculated seawater using the modified PES UF membrane without the pre-chlorination step maintained the highest initial flux (3.27 ± 0.13 m³·m⁻²·h⁻¹) in the membrane, as well as having one and a half times higher water productivity than the unmodified membrane. The highest removal of bacterial cells was achieved by the modified membrane without chlorination, in which about 12.07 × 10⁴ and 8.9 × 10⁴ colony-forming unit (CFU) m⁻² bacterial cells were retained on the unmodified and modified membrane surfaces, respectively, while 29.4 × 10⁶ and 0.42 × 10⁶ CFU mL⁻¹ reached the filtrate for the unmodified and modified membranes, respectively. The use of chlorine disinfectant resulted in significant bacterial regrowth. Full article

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

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22 pages, 1396 KiB

Open AccessReview

The Role of Lipid Environment in Ganglioside GM1-Induced Amyloid β Aggregation

by Vladimir Rudajev and Jiri Novotny

Membranes 2020, 10(9), 226; https://doi.org/10.3390/membranes10090226 - 09 Sep 2020

Cited by 26 | Viewed by 5576

Abstract

Ganglioside GM1 is the most common brain ganglioside enriched in plasma membrane regions known as lipid rafts or membrane microdomains. GM1 participates in many modulatory and communication functions associated with the development, differentiation, and protection of neuronal tissue. It has, however, been demonstrated [...] Read more.

Ganglioside GM1 is the most common brain ganglioside enriched in plasma membrane regions known as lipid rafts or membrane microdomains. GM1 participates in many modulatory and communication functions associated with the development, differentiation, and protection of neuronal tissue. It has, however, been demonstrated that GM1 plays a negative role in the pathophysiology of Alzheimer’s disease (AD). The two features of AD are the formation of intracellular neurofibrillary bodies and the accumulation of extracellular amyloid β (Aβ). Aβ is a peptide characterized by intrinsic conformational flexibility. Depending on its partners, Aβ can adopt different spatial arrangements. GM1 has been shown to induce specific changes in the spatial organization of Aβ, which lead to enhanced peptide accumulation and deleterious effect especially on neuronal membranes containing clusters of this ganglioside. Changes in GM1 levels and distribution during the development of AD may contribute to the aggravation of the disease. Full article

(This article belongs to the Special Issue Protein-Lipid Interactions as Key Regulators of Cell Function)

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13 pages, 1834 KiB

Open AccessArticle

The Water Flux Dynamic in a Hybrid Forward Osmosis-Membrane Distillation for Produced Water Treatment

by Normi Izati Mat Nawi, Muhammad Roil Bilad, Ganeswaran Anath, Nik Abdul Hadi Nordin, Jundika Candra Kurnia, Yusuf Wibisono and Nasrul Arahman

Membranes 2020, 10(9), 225; https://doi.org/10.3390/membranes10090225 - 09 Sep 2020

Cited by 15 | Viewed by 3378

Abstract

Standalone membrane distillation (MD) and forward osmosis (FO) have been considered as promising technologies for produced water treatment. However, standalone MD is still vulnerable to membrane-wetting and scaling problems, while the standalone FO is energy-intensive, since it requires the recovery of the draw [...] Read more.

Standalone membrane distillation (MD) and forward osmosis (FO) have been considered as promising technologies for produced water treatment. However, standalone MD is still vulnerable to membrane-wetting and scaling problems, while the standalone FO is energy-intensive, since it requires the recovery of the draw solution (DS). Thus, the idea of coupling FO and MD is proposed as a promising combination in which the MD facilitate DS recovery for FO—and FO acts as pretreatment to enhance fouling and wetting-resistance of the MD. This study was therefore conducted to investigate the effect of DS temperature on the dynamic of water flux of a hybrid FO–MD. First, the effect of the DS temperature on the standalone FO and MD was evaluated. Later, the flux dynamics of both units were evaluated when the FO and DS recovery (via MD) was run simultaneously. Results show that an increase in the temperature difference (from 20 to 60 °C) resulted in an increase of the FO and MD fluxes from 11.17 ± 3.85 to 30.17 ± 5.51 L m⁻² h⁻¹, and from 0.5 ± 0.75 to 16.08 L m⁻² h⁻¹, respectively. For the hybrid FO–MD, either MD or FO could act as the limiting process that dictates the equilibrium flux. Both the concentration and the temperature of DS affected the flux dynamic. When the FO flux was higher than MD flux, DS was diluted, and its temperature decreased; both then lowered the FO flux until reaching an equilibrium (equal FO and MD flux). When FO flux was lower than MD flux, the DS was concentrated which increased the FO flux until reaching the equilibrium. The overall results suggest the importance of temperature and concentration of solutes in the DS in affecting the water flux dynamic hybrid process. Full article

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

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16 pages, 3504 KiB

Open AccessArticle

Poly[3-ethyl-1-vinyl-imidazolium] diethyl phosphate/Pebax^® 1657 Composite Membranes and Their Gas Separation Performance

by Irene R. Mazzei, Daria Nikolaeva, Alessio Fuoco, Sandrine Loïs, Sébastien Fantini, Marcello Monteleone, Elisa Esposito, Saeed Jamali Ashtiani, Marek Lanč, Ondřej Vopička, Karel Friess, Ivo F. J. Vankelecom and Johannes Carolus Jansen

Membranes 2020, 10(9), 224; https://doi.org/10.3390/membranes10090224 - 08 Sep 2020

Cited by 6 | Viewed by 4409

Abstract

Poly(ionic liquid)s are an innovative class of materials with promising properties in gas separation processes that can be used to boost the neat polymer performances. Nevertheless, some of their properties such as stability and mechanical strength have to be improved to render them [...] Read more.

Poly(ionic liquid)s are an innovative class of materials with promising properties in gas separation processes that can be used to boost the neat polymer performances. Nevertheless, some of their properties such as stability and mechanical strength have to be improved to render them suitable as materials for industrial applications. This work explored, on the one hand, the possibility to improve gas transport and separation properties of the block copolymer Pebax^® 1657 by blending it with poly[3-ethyl-1-vinyl-imidazolium] diethyl phosphate (PEVI-DEP). On the other hand, Pebax^® 1657 served as a support for the PIL and provided mechanical resistance to the samples. Pebax^® 1657/PEVI-DEP composite membranes containing 20, 40, and 60 wt.% of PEVI-DEP were cast from solutions of the right proportion of the two polymers in a water/ethanol mixture. The PEVI-DEP content affected both the morphology of the dense membranes and gas transport through the membranes. These changes were revealed by scanning electron microscopy (SEM), time-lag, and gravimetric sorption measurements. Pebax^® 1657 and PEVI-DEP showed similar affinity towards CO₂, and its uptake or solubility was not influenced by the amount of PIL in the membrane. Therefore, the addition of the PIL did not lead to improvements in the separation of CO₂ from other gases. Importantly, PEVI-DEP (40 wt.%) incorporation affected and improved permeability and selectivity by more than 50% especially for the separation of light gases, e.g., H₂/CH₄ and H₂/CO₂, but higher PEVI-DEP concentrations lead to a decline in the transport properties. Full article

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

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12 pages, 2021 KiB

Open AccessArticle

Removal of Bacteria and Organic Carbon by an Integrated Ultrafiltration—Nanofiltration Desalination Pilot Plant

by Zahid Ur Rehman, Bayan Khojah, TorOve Leiknes, Safiya Alsogair and Mona Alsomali

Membranes 2020, 10(9), 223; https://doi.org/10.3390/membranes10090223 - 04 Sep 2020

Cited by 6 | Viewed by 3195

Abstract

Fouling caused by organic matter and bacteria remains a significant challenge for the membrane-based desalination industry. Fouling decreases the permeate quality and membrane performance and also increases energy demands. Here, we quantified the amount of organic matter and bacteria at several stages along [...] Read more.

Fouling caused by organic matter and bacteria remains a significant challenge for the membrane-based desalination industry. Fouling decreases the permeate quality and membrane performance and also increases energy demands. Here, we quantified the amount of organic matter and bacteria at several stages along the water-treatment train of an integrated ultrafiltration–nanofiltration seawater treatment pilot plant. We quantified the organic matter, in terms of Total Organic Carbon (TOC) and Assimilable Organic Carbon (AOC), and evaluated its composition using Liquid Chromatography for Organic Carbon Detection (LC-OCD). The bacterial cells were counted using Bactiquant. We found that ultrafiltration (UF) was effective at removing bacterial cells (99.7%) but not TOC. By contrast, nanofiltration (NF) successfully removed both TOC (95%) and bacterial cells. However, the NF permeate showed higher amounts of AOC than seawater. LC-OCD analysis suggested that the AOC was mostly composed of low molecular weight neutral substances. Furthermore, we found that the cleaning of the UF membrane using chemically enhanced backwash reduced the amount of AOC released into the UF permeate. By implementing the cleaning-in-place of the NF membrane, the pressure drop was restored to the normal level. Our results show that the UF and NF membrane cleaning regimes investigated in this study improved membrane performance. However, AOC remained the hardest-to-treat fraction of organic carbon. AOC should, therefore, be monitored closely and regularly to mitigate biofouling in downstream processes. Full article

(This article belongs to the Special Issue New Perspectives on Membrane Bioreactors)

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14 pages, 1165 KiB

Open AccessArticle

Light Scattering as an Easy Tool to Measure Vesicles Weight Concentration

by Giulia Di Prima, Fabio Librizzi and Rita Carrotta

Membranes 2020, 10(9), 222; https://doi.org/10.3390/membranes10090222 - 03 Sep 2020

Cited by 7 | Viewed by 2651

Abstract

Over the last few decades, liposomes have emerged as promising drug delivery systems and effective membrane models for studying biophysical and biological processes. For all applications, knowing their concentration after preparation is crucial. Thus, the development of methods for easily controlling vesicles concentration [...] Read more.

Over the last few decades, liposomes have emerged as promising drug delivery systems and effective membrane models for studying biophysical and biological processes. For all applications, knowing their concentration after preparation is crucial. Thus, the development of methods for easily controlling vesicles concentration would be of great utility. A new assay is presented here, based on a suitable analysis of light scattering intensity from liposome dispersions. The method, tested for extrusion preparations, is precise, easy, fast, non-destructive and uses a tiny amount of sample. Furthermore, the scattering intensity can be measured indifferently at different angles, or even by using the elastic band obtained from a standard spectrofluorimeter. To validate the method, the measured concentrations of vesicles of different matrix compositions and sizes, measured by light scattering with different angles and instruments, were compared to the data obtained by the standard Stewart assay. Consistent results were obtained. The light scattering assay is based on the assessment of the mass fraction lost in the preparation, and can be applied for methods such as extrusion, homogenization, French press and other microfluidic procedures. Full article

(This article belongs to the Section Biological Membrane Dynamics and Computation)

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72 pages, 17395 KiB

Open AccessEditor’s ChoiceReview

Electrodialytic Processes: Market Overview, Membrane Phenomena, Recent Developments and Sustainable Strategies

by Laurent Bazinet and Thibaud R. Geoffroy

Membranes 2020, 10(9), 221; https://doi.org/10.3390/membranes10090221 - 02 Sep 2020

Cited by 88 | Viewed by 8712

Abstract

In the context of preserving and improving human health, electrodialytic processes are very promising perspectives. Indeed, they allow the treatment of water, preservation of food products, production of bioactive compounds, extraction of organic acids, and recovery of energy from natural and wastewaters without [...] Read more.

In the context of preserving and improving human health, electrodialytic processes are very promising perspectives. Indeed, they allow the treatment of water, preservation of food products, production of bioactive compounds, extraction of organic acids, and recovery of energy from natural and wastewaters without major environmental impact. Hence, the aim of the present review is to give a global portrait of the most recent developments in electrodialytic membrane phenomena and their uses in sustainable strategies. It has appeared that new knowledge on pulsed electric fields, electroconvective vortices, overlimiting conditions and reversal modes as well as recent demonstrations of their applications are currently boosting the interest for electrodialytic processes. However, the hurdles are still high when dealing with scale-ups and real-life conditions. Furthermore, looking at the recent research trends, potable water and wastewater treatment as well as the production of value-added bioactive products in a circular economy will probably be the main applications to be developed and improved. All these processes, taking into account their principles and specificities, can be used for specific eco-efficient applications. However, to prove the sustainability of such process strategies, more life cycle assessments will be necessary to convince people of the merits of coupling these technologies. Full article

(This article belongs to the Special Issue Membrane Technologies for Sustainable Biofood Production Lines)

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16 pages, 3603 KiB

Open AccessArticle

Micellar-Enhanced Ultrafiltration Using a Plant-Derived Surfactant for Dye Separation in Wastewater Treatment

by Nita Aryanti, Aininu Nafiunisa, Tutuk Djoko Kusworo and Dyah Hesti Wardhani

Membranes 2020, 10(9), 220; https://doi.org/10.3390/membranes10090220 - 02 Sep 2020

Cited by 11 | Viewed by 4091

Abstract

Micellar-enhanced ultrafiltration (MEUF) is one of several membrane methods used for the removal of trace organic pollutants from aqueous streams. In this process, a surfactant is added to a polluted aqueous solution at a concentration higher than its critical micelle concentration (CMC). Unlike [...] Read more.

Micellar-enhanced ultrafiltration (MEUF) is one of several membrane methods used for the removal of trace organic pollutants from aqueous streams. In this process, a surfactant is added to a polluted aqueous solution at a concentration higher than its critical micelle concentration (CMC). Unlike synthetic surfactants, natural surfactants, from plants such as the saponin, while ecologically adaptable as surfactants in MEUF systems, are also biodegradable, renewable, and environmentally safe. This study applied Sapindus rarak extract as the natural surfactant in MEUF for Remazol dye separation. It was found that the presence of Sapindus rarak extract increased separation of Remazol red and blue dyes by up to 97.02% and 99.42%, respectively. However, the addition of surfactant decreased permeate fluxes due to membrane fouling and concentration polarization. In addition, loading micelle (Lm), representing the performance of the surfactant micelle for dye separation, as well as the blocking mechanism, was investigated. Lm was found to be in the range of 0.002–0.068 mM dyes/mM saponin. Ultrafiltration blocking mechanisms, as confirmed by the Hermia model, were: standard blocking, for cases without the addition of surfactant; cake formation, for cases with surfactant below the CMC; and complete blocking, for cases with surfactant above the CMC. Full article

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13 pages, 2378 KiB

Open AccessArticle

Tailoring and Remotely Switching Performance of Ultrafiltration Membranes by Magnetically Responsive Polymer Chains

by Anh Vu, Arijit Sengupta, Emily Freeman, Xianghong Qian, Mathias Ulbricht and S. Ranil Wickramasinghe

Membranes 2020, 10(9), 219; https://doi.org/10.3390/membranes10090219 - 01 Sep 2020

Cited by 2 | Viewed by 2101

Abstract

Magnetically responsive ultrafiltration membranes were prepared by grafting poly(2-hydroxyethyl methacrylate) chains from the outer surface of 100-kDa regenerated cellulose ultrafiltration membranes. Surface-initiated atom transfer radical polymerization was used to graft the polymer chains. Grafting from the internal pore surface was suppressed by using [...] Read more.

Magnetically responsive ultrafiltration membranes were prepared by grafting poly(2-hydroxyethyl methacrylate) chains from the outer surface of 100-kDa regenerated cellulose ultrafiltration membranes. Surface-initiated atom transfer radical polymerization was used to graft the polymer chains. Grafting from the internal pore surface was suppressed by using glycerol as a pore-filling solvent during initiator immobilization at varied densities. Glycerol suppresses the initiator attachment to the pore surface. Polymerization times of up to four hours were investigated. Superparamagnetic nanoparticles were covalently attached to the chain end. Membrane performance was determined using bovine serum albumin and dextran as model solutes. Increasing the grafted polymer chain density and length led to a decrease in the permeate flux and an increase in the apparent rejection coefficient. In an oscillating magnetic field, movement of the grafted polymer chains led to a decrease in the permeate flux, as well as an increase in the apparent rejection coefficient of the model solutes. Full article

(This article belongs to the Section Membrane Analysis and Characterization)

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