International Journal of Molecular Sciences

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4 pages, 196 KiB

Open AccessEditorial

Ion and Molecule Transport in Membrane Systems

by Victor Nikonenko and Natalia Pismenskaya

Int. J. Mol. Sci. 2021, 22(7), 3556; https://doi.org/10.3390/ijms22073556 - 30 Mar 2021

Cited by 9 | Viewed by 1749

Abstract

Membranes plays enormous role in our life [...] Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

Research

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12 pages, 1932 KiB

Open AccessArticle

Correlations of Ion Composition and Power Efficiency in a Reverse Electrodialysis Heat Engine

by Fabao Luo, Yang Wang, Maolin Sha and Yanxin Wei

Int. J. Mol. Sci. 2019, 20(23), 5860; https://doi.org/10.3390/ijms20235860 - 22 Nov 2019

Cited by 6 | Viewed by 3018

Abstract

The main objective of this study is to explore the influence of ion composition on the trans-membrane potential across the ion exchange membrane (IEM), and thus offers a reference for the deep insight of “reverse electrodialysis heat engine” running in the composite systems. [...] Read more.

The main objective of this study is to explore the influence of ion composition on the trans-membrane potential across the ion exchange membrane (IEM), and thus offers a reference for the deep insight of “reverse electrodialysis heat engine” running in the composite systems. In comparison to the natural system (river water | seawater), the performance of the reverse electrodialysis (RED) stack was examined using NaHCO₃, Na₂CO₃, and NH₄Cl as the supporting electrolyte in the corresponding compartment. The effect of flow rates and the concentration ratio in the high salt concentration compartment (HCC)/low salt concentration compartment (LCC) on energy generation was investigated in terms of the open-circuit voltage (OCV) and power density per membrane area. It was found that the new system (0.49 M NaCl + 0.01 M NaHCO₃|0.01 M NaHCO₃) output a relatively stable power density (0.174 W·m⁻²), with the open-circuit voltage 2.95 V under the low flow rate of 0.22 cm/s. Meanwhile, the simulated natural system (0.5 M NaCl|0.01 M NaCl) output the power density 0.168 W·m⁻², with the open-circuit voltage 2.86 V under the low flow rate of 0.22 cm/s. The findings in this work further confirm the excellent potential of RED for the recovery of salinity gradient energy (SGP) that is reserved in artificially-induced systems (wastewaters). Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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21 pages, 3833 KiB

Open AccessArticle

Ion Transport Study in CS: POZ Based Polymer Membrane Electrolytes Using Trukhan Model

by Shujahadeen B. Aziz, Wrya O. Karim, M. A. Brza, Rebar T. Abdulwahid, Salah Raza Saeed, Shakhawan Al-Zangana and M. F. Z. Kadir

Int. J. Mol. Sci. 2019, 20(21), 5265; https://doi.org/10.3390/ijms20215265 - 23 Oct 2019

Cited by 53 | Viewed by 3379

Abstract

In this work, analysis of ion transport parameters of polymer blend electrolytes incorporated with magnesium trifluoromethanesulfonate (Mg(CF₃SO₃)₂) was carried out by employing the Trukhan model. A solution cast technique was used to obtain the polymer blend electrolytes [...] Read more.

In this work, analysis of ion transport parameters of polymer blend electrolytes incorporated with magnesium trifluoromethanesulfonate (Mg(CF₃SO₃)₂) was carried out by employing the Trukhan model. A solution cast technique was used to obtain the polymer blend electrolytes composed of chitosan (CS) and poly (2-ethyl-2-oxazoline) (POZ). From X-ray diffraction (XRD) patterns, improvement in amorphous phase for the blend samples has been observed in comparison to the pure state of CS. From impedance plot, bulk resistance (R_b) was found to decrease with increasing temperature. Based on direct current (DC) conductivity (σ_dc) patterns, considerations on the ion transport models of Arrhenius and Vogel–Tammann–Fulcher (VTF) were given. Analysis of the dielectric properties was carried out at different temperatures and the obtained results were linked to the ion transport mechanism. It is demonstrated in the real part of electrical modulus that chitosan-salt systems are extremely capacitive. The asymmetric peak of the imaginary part (M_i) of electric modulus indicated that there is non-Debye type of relaxation for ions. From frequency dependence of dielectric loss (ε″) and the imaginary part (M_i) of electric modulus, suitable coupling among polymer segmental and ionic motions was identified. Two techniques were used to analyze the viscoelastic relaxation dynamic of ions. The Trukhan model was used to determine the diffusion coefficient (D) by using the frequency related to peak frequencies and loss tangent maximum heights (tanδ_max). The Einstein–Nernst equation was applied to determine the carrier number density (n) and mobility. The ion transport parameters, such as D, n and mobility (μ), at room temperature, were found to be 4 × 10⁻⁵ cm²/s, 3.4 × 10¹⁵ cm⁻³, and 1.2 × 10⁻⁴ cm²/Vs, respectively. Finally, it was shown that an increase in temperature can also cause these parameters to increase. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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13 pages, 3213 KiB

Open AccessArticle

Confined Dynamics of Water in Transmembrane Pore of TRPV1 Ion Channel

by Yury A. Trofimov, Nikolay A. Krylov and Roman G. Efremov

Int. J. Mol. Sci. 2019, 20(17), 4285; https://doi.org/10.3390/ijms20174285 - 1 Sep 2019

Cited by 8 | Viewed by 2918

Abstract

Solvation effects play a key role in chemical and biological processes. The microscopic properties of water near molecular surfaces are radically different from those in the bulk. Furthermore, the behavior of water in confined volumes of a nanometer scale, including transmembrane pores of [...] Read more.

Solvation effects play a key role in chemical and biological processes. The microscopic properties of water near molecular surfaces are radically different from those in the bulk. Furthermore, the behavior of water in confined volumes of a nanometer scale, including transmembrane pores of ion channels, is especially nontrivial. Knowledge at the molecular level of structural and dynamic parameters of water in such systems is necessary to understand the mechanisms of ion channels functioning. In this work, the results of molecular dynamics (MD) simulations of water in the pore and selectivity filter domains of TRPV1 (Transient Receptor Potential Vanilloid type 1) membrane channel are considered. These domains represent nanoscale volumes with strongly amphiphilic walls, where physical behavior of water radically differs from that of free hydration (e.g., at protein interfaces) or in the bulk. Inside the pore and filter domains, water reveals a very heterogeneous spatial distribution and unusual dynamics: It forms compact areas localized near polar groups of particular residues. Residence time of water molecules in such areas is at least 1.5 to 3 times larger than that observed for similar groups at the protein surface. Presumably, these water “blobs” play an important role in the functional activity of TRPV1. In particular, they take part in hydration of the hydrophobic TRPV1 pore by localizing up to six waters near the so-called “lower gate” of the channel and reducing by this way the free energy barrier for ion and water transport. Although the channel is formed by four identical protein subunits, which are symmetrically packed in the initial experimental 3D structure, in the course of MD simulations, hydration of the same amino acid residues of individual subunits may differ significantly. This greatly affects the microscopic picture of the distribution of water in the channel and, potentially, the mechanism of its functioning. Therefore, reconstruction of the full picture of TRPV1 channel solvation requires thorough atomistic simulations and analysis. It is important that the naturally occurring porous volumes, like ion-conducting protein domains, reveal much more sophisticated and fine-tuned regulation of solvation than, e.g., artificially designed carbon nanotubes. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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19 pages, 6720 KiB

Open AccessArticle

Selective Separation of Acetic and Hexanoic Acids across Polymer Inclusion Membrane with Ionic Liquids as Carrier

by Bao-Ying Wang, Na Zhang, Zhen-Yu Li, Qiao-Lin Lang, Bing-Hua Yan, Yang Liu and Yang Zhang

Int. J. Mol. Sci. 2019, 20(16), 3915; https://doi.org/10.3390/ijms20163915 - 12 Aug 2019

Cited by 22 | Viewed by 4135

Abstract

This paper first reports on the selective separation of volatile fatty acids (VFAs) (acetic and hexanoic acids) using polymer inclusion membranes (PIMs) containing quaternary ammonium and phosphonium ionic liquids (ILs) as the carrier. The affecting parameters such as IL content, VFA concentration, and [...] Read more.

This paper first reports on the selective separation of volatile fatty acids (VFAs) (acetic and hexanoic acids) using polymer inclusion membranes (PIMs) containing quaternary ammonium and phosphonium ionic liquids (ILs) as the carrier. The affecting parameters such as IL content, VFA concentration, and the initial pH of the feed solution as well as the type and concentration of the stripping solution were investigated. PIMs performed a much higher selective separation performance toward hexanoic acid. The optimal PIM composed of 60 wt% quaternary ammonium IL with the permeability coefficients for acetic and hexanoic acid of 0.72 and 4.38 µm s⁻¹, respectively, was determined. The purity of hexanoic acid obtained in the stripping solution increased with an increase in the VFA concentration of the feed solution and decreasing HCl concentration of the stripping solution. The use of Na₂CO₃ as the stripping solution and the involvement of the electrodialysis process could dramatically enhance the transport efficiency of both VFAs, but the separation efficiency decreased sharply. Furthermore, a coordinating mechanism containing hydrogen bonding and ion exchange for VFA transport was demonstrated. The highest purity of hexanoic acid (89.3%) in the stripping solution demonstrated that this PIM technology has good prospects for the separation and recovery of VFAs from aqueous solutions. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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17 pages, 1663 KiB

Open AccessArticle

Poly(2,6-Dimethyl-1,4-Phenylene Oxide)-Based Hydroxide Exchange Separator Membranes for Zinc–Air Battery

by Ali Abbasi, Soraya Hosseini, Anongnat Somwangthanaroj, Ahmad Azmin Mohamad and Soorathep Kheawhom

Int. J. Mol. Sci. 2019, 20(15), 3678; https://doi.org/10.3390/ijms20153678 - 26 Jul 2019

Cited by 49 | Viewed by 5772 | Correction

Abstract

Rechargeable zinc–air batteries are deemed as the most feasible alternative to replace lithium–ion batteries in various applications. Among battery components, separators play a crucial role in the commercial realization of rechargeable zinc–air batteries, especially from the viewpoint of preventing zincate (Zn(OH)₄²⁻ [...] Read more.

Rechargeable zinc–air batteries are deemed as the most feasible alternative to replace lithium–ion batteries in various applications. Among battery components, separators play a crucial role in the commercial realization of rechargeable zinc–air batteries, especially from the viewpoint of preventing zincate (Zn(OH)₄²⁻) ion crossover from the zinc anode to the air cathode. In this study, a new hydroxide exchange membrane for zinc–air batteries was synthesized using poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) as the base polymer. PPO was quaternized using three tertiary amines, including trimethylamine (TMA), 1-methylpyrolidine (MPY), and 1-methylimidazole (MIM), and casted into separator films. The successful synthesis process was confirmed by proton nuclear magnetic resonance and Fourier-transform infrared spectroscopy, while their thermal stability was examined using thermogravimetric analysis. Besides, their water/electrolyte absorption capacity and dimensional change, induced by the electrolyte uptake, were studied. Ionic conductivity of PPO–TMA, PPO–MPY, and PPO–MIM was determined using electrochemical impedance spectroscopy to be 0.17, 0.16, and 0.003 mS/cm, respectively. Zincate crossover evaluation tests revealed very low zincate diffusion coefficient of 1.13 × 10⁻⁸, and 0.28 × 10⁻⁸ cm²/min for PPO–TMA, and PPO–MPY, respectively. Moreover, galvanostatic discharge performance of the primary batteries assembled using PPO–TMA and PPO–MPY as initial battery tests showed a high specific discharge capacity and specific power of ~800 mAh/g_Zn and 1000 mWh/g_Zn, respectively. Low zincate crossover and high discharge capacity of these separator membranes makes them potential materials to be used in zinc–air batteries. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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22 pages, 2809 KiB

Open AccessArticle

Partial Fluxes of Phosphoric Acid Anions through Anion-Exchange Membranes in the Course of NaH₂PO₄ Solution Electrodialysis

by Olesya Rybalkina, Kseniya Tsygurina, Ekaterina Melnikova, Semyon Mareev, Ilya Moroz, Victor Nikonenko and Natalia Pismenskaya

Int. J. Mol. Sci. 2019, 20(14), 3593; https://doi.org/10.3390/ijms20143593 - 23 Jul 2019

Cited by 36 | Viewed by 4975

Abstract

Electrodialysis (ED) with ion-exchange membranes is a promising method for the extraction of phosphates from municipal and other wastewater in order to obtain cheap mineral fertilizers. Phosphorus is transported through an anion-exchange membrane (AEM) by anions of phosphoric acid. However, which phosphoric acid [...] Read more.

Electrodialysis (ED) with ion-exchange membranes is a promising method for the extraction of phosphates from municipal and other wastewater in order to obtain cheap mineral fertilizers. Phosphorus is transported through an anion-exchange membrane (AEM) by anions of phosphoric acid. However, which phosphoric acid anions carry the phosphorus in the membrane and the boundary solution, that is, the mechanism of phosphorus transport, is not yet clear. Some authors report an unexpectedly low current efficiency of this process and high energy consumption. In this paper, we report the partial currents of H₂PO₄⁻, HPO₄²⁻, and PO₄³⁻ through Neosepta AMX and Fujifilm AEM Type X membranes, as well as the partial currents of H₂PO₄⁻ and H⁺ ions through a depleted diffusion layer of a 0.02 M NaH₂PO₄ feed solution measured as functions of the applied potential difference across the membrane under study. It was shown that the fraction of the current transported by anions through AEMs depend on the total current density/potential difference. This was due to the fact that the pH of the internal solution in the membrane increases with the growing current due to the increasing concentration polarization (a lower electrolyte concentration at the membrane surface leads to higher pH shift in the membrane). The HPO₄²⁻ ions contributed to the charge transfer even when a low current passed through the membrane; with an increasing current, the contribution of the HPO₄²⁻ ions grew, and when the current was about 2.5 i_lim^Lev (i_lim^Lev was the theoretical limiting current density), the PO₄³⁻ ions started to carry the charge through the membrane. However, in the feed solution, the pH was 4.6 and only H₂PO₄⁻ ions were present. When H₂PO₄⁻ ions entered the membrane, a part of them transformed into doubly and triply charged anions; the H⁺ ions were released in this transformation and returned to the depleted diffusion layer. Thus, the phosphorus total flux, j_P (equal to the sum of the fluxes of all phosphorus-bearing species) was limited by the H₂PO₄⁻ transport from the bulk of feed solution to the membrane surface. The value of j_P was close to i_lim^Lev/F (F is the Faraday constant). A slight excess of j_P over i_lim^Lev/F was observed, which is due to the electroconvection and exaltation effects. The visualization showed that electroconvection in the studied systems was essentially weaker than in systems with strong electrolytes, such as NaCl. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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13 pages, 2281 KiB

Open AccessArticle

Behavior of Embedded Cation-Exchange Particles in a DC Electric Field

by Lucie Vobecká, Tomáš Belloň and Zdeněk Slouka

Int. J. Mol. Sci. 2019, 20(14), 3579; https://doi.org/10.3390/ijms20143579 - 22 Jul 2019

Cited by 13 | Viewed by 3824

Abstract

Electrodialysis and electrodeionization are separation processes whose performance depends on the quality and properties of ion-exchange membranes. One of the features that largely affects these properties is heterogeneity of the membranes both on the macroscopic and microscopic level. Macroscopic heterogeneity is an intrinsic [...] Read more.

Electrodialysis and electrodeionization are separation processes whose performance depends on the quality and properties of ion-exchange membranes. One of the features that largely affects these properties is heterogeneity of the membranes both on the macroscopic and microscopic level. Macroscopic heterogeneity is an intrinsic property of heterogeneous ion-exchange membranes. In these membranes, the functional ion-exchange component is dispersed in a non-conductive binder. The functional component is finely ground ion-exchange resin particles. The understanding of the effect of structure on the heterogeneous membrane properties and behavior is thus of utmost importance since it does not only affect the actual performance but also the cost and therefore competitiveness of the aforementioned separation processes. Here we study the electrokinetic behavior of cation-exchange resin particle systems with well-defined geometrical structure. This approach can be understood as a bottom up approach regarding the membrane preparation. We prepare a structured cation-exchange membrane by using its fundamental component, which is the ion exchange resin. We then perform an experimental study with four different experimental systems in which the number of used cation-exchange particles changes from 1 to 4. These systems are studied by means of basic electrochemical characterization measurements, such as measurement of current–voltage curves and direct optical observation of phenomena that occur at the interface between the ion-exchange system and the adjacent electrolyte. Our work aims at better understanding of the relation between the structure and the membrane properties and of how structure affects electrokinetic behavior of these systems. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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16 pages, 2335 KiB

Open AccessArticle

Highly Conductive and Water-Swelling Resistant Anion Exchange Membrane for Alkaline Fuel Cells

by Qianqian Ge, Xiang Zhu and Zhengjin Yang

Int. J. Mol. Sci. 2019, 20(14), 3470; https://doi.org/10.3390/ijms20143470 - 15 Jul 2019

Cited by 11 | Viewed by 4206

Abstract

To ameliorate the trade-off effect between ionic conductivity and water swelling of anion exchange membranes (AEMs), a crosslinked, hyperbranched membrane (C-HBM) combining the advantages of densely functionalization architecture and crosslinking structure was fabricated by the quaternization of the hyperbranched poly(4-vinylbenzyl chloride) (HB-PVBC) with [...] Read more.

To ameliorate the trade-off effect between ionic conductivity and water swelling of anion exchange membranes (AEMs), a crosslinked, hyperbranched membrane (C-HBM) combining the advantages of densely functionalization architecture and crosslinking structure was fabricated by the quaternization of the hyperbranched poly(4-vinylbenzyl chloride) (HB-PVBC) with a multiamine oligomer poly(N,N-Dimethylbenzylamine). The membrane displayed well-developed microphase separation morphology, as confirmed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Moreover, the corresponding high ionic conductivity, strongly depressed water swelling, high thermal stability, and acceptable alkaline stability were achieved. Of special note is the much higher ratio of hydroxide conductivity to water swelling (33.0) than that of most published side-chain type, block, and densely functionalized AEMs, implying its higher potential for application in fuel cells. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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13 pages, 6428 KiB

Open AccessArticle

Simple Preparation of LaPO₄:Ce, Tb Phosphors by an Ionic-Liquid-Driven Supported Liquid Membrane System

by Jianguo Li, Hongying Dong, Fan Yang, Liangcheng Sun, Zhigang Zhao, Ruixi Bai and Hao Zhang

Int. J. Mol. Sci. 2019, 20(14), 3424; https://doi.org/10.3390/ijms20143424 - 12 Jul 2019

Cited by 5 | Viewed by 3331

Abstract

In this work, LaPO₄:Ce, Tb phosphors were prepared by firing a LaPO₄:Ce, Tb precipitate using an ionic-liquid-driven supported liquid membrane system. The entire system consisted of three parts: a mixed rare earth ion supply phase, a phosphate supply phase, [...] Read more.

In this work, LaPO₄:Ce, Tb phosphors were prepared by firing a LaPO₄:Ce, Tb precipitate using an ionic-liquid-driven supported liquid membrane system. The entire system consisted of three parts: a mixed rare earth ion supply phase, a phosphate supply phase, and an ionic-liquid-driven supporting liquid membrane phase. This method showed the advantages of a high flux, high efficiency, and more controllable reaction process. The release rate of PO₄³⁻ from the liquid film under different types of ionic liquid, the ratio of the rare earth ions in the precursor mixture, and the structure, morphology, and photoluminescence properties of LaPO₄:Ce, Tb were investigated by inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, Raman spectra, scanning electron microscopy, and photoluminescence emission spectra methods. The results showed that a pure phase of lanthanum orthophosphate with a monoclinic structure can be formed. Due to differences in the anions in the rare earth supply phase, the prepared phosphors showed micro-spherical (when using rare earth sulfate as the raw material) and nanoscale stone-shape (when using rare earth nitrate as the raw material) morphologies. Moreover, the phosphors prepared by this method had good luminescent properties, reaching a maximum emission intensity under 277 nm excitation with a predominant green emission at 543 nm which corresponded to the ⁵D₄-⁷F₅ transition of Tb³⁺. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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26 pages, 6223 KiB

Open AccessArticle

Development of Polymer Blend Electrolyte Membranes Based on Chitosan: Dextran with High Ion Transport Properties for EDLC Application

by Shujahadeen B. Aziz, Muhamad H. Hamsan, Mohd F. Z. Kadir, Wrya O. Karim and Ranjdar M. Abdullah

Int. J. Mol. Sci. 2019, 20(13), 3369; https://doi.org/10.3390/ijms20133369 - 9 Jul 2019

Cited by 102 | Viewed by 5879

Abstract

Solid polymer blend electrolyte membranes (SPBEM) composed of chitosan and dextran with the incorporation of various amounts of lithium perchlorate (LiClO₄) were synthesized. The complexation of the polymer blend electrolytes with the salt was examined using FTIR spectroscopy and X-ray diffraction [...] Read more.

Solid polymer blend electrolyte membranes (SPBEM) composed of chitosan and dextran with the incorporation of various amounts of lithium perchlorate (LiClO₄) were synthesized. The complexation of the polymer blend electrolytes with the salt was examined using FTIR spectroscopy and X-ray diffraction (XRD). The morphology of the SPBEs was also investigated using field emission scanning electron microscopy (FESEM). The ion transport behavior of the membrane films was measured using impedance spectroscopy. The membrane with highest LiClO₄ content was found to exhibit the highest conductivity of 5.16 × 10⁻³ S/cm. Ionic (t_i) and electronic (t_e) transference numbers for the highest conducting electrolyte were found to be 0.98 and 0.02, respectively. Electrochemical stability was estimated from linear sweep voltammetry and found to be up to ~2.3V for the Li⁺ ion conducting electrolyte. The only existence of electrical double charging at the surface of electrodes was evidenced from the absence of peaks in cyclic voltammetry (CV) plot. The discharge slope was observed to be almost linear, confirming the capacitive behavior of the EDLC. The performance of synthesized EDLC was studied using CV and charge–discharge techniques. The highest specific capacitance was achieved to be 8.7 F·g⁻¹ at 20th cycle. The efficiency (η) was observed to be at 92.8% and remained constant at 92.0% up to 100 cycles. The EDLC was considered to have a reasonable electrode-electrolyte contact, in which η exceeds 90.0%. It was determined that equivalent series resistance (R_esr) is quite low and varies from 150 to 180 Ω over the 100 cycles. Energy density (E_d) was found to be 1.21 Wh·kg⁻¹ at the 1st cycle and then remained stable at 0.86 Wh·kg⁻¹ up to 100 cycles. The interesting observation is that the value of P_d increases back to 685 W·kg⁻¹ up to 80 cycles. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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10 pages, 2689 KiB

Open AccessArticle

Improving Wettability: Deposition of TiO₂ Nanoparticles on the O₂ Plasma Activated Polypropylene Membrane

by Babak Jaleh, Ehsan Sabzi Etivand, Bahareh Feizi Mohazzab, Mahmoud Nasrollahzadeh and Rajender S. Varma

Int. J. Mol. Sci. 2019, 20(13), 3309; https://doi.org/10.3390/ijms20133309 - 5 Jul 2019

Cited by 30 | Viewed by 3704

Abstract

Radio frequency plasma is one of the means to modify the polymer surface namely in the activation of polypropylene membranes (PPM) with O₂ plasma. Activated membranes were deposited with TiO₂ nanoparticles by the dip coating method and the bare sample and [...] Read more.

Radio frequency plasma is one of the means to modify the polymer surface namely in the activation of polypropylene membranes (PPM) with O₂ plasma. Activated membranes were deposited with TiO₂ nanoparticles by the dip coating method and the bare sample and modified sample (PPM5-TiO₂) were irradiated by UV lamps for 20–120 min. Characterization techniques such as X-ray diffraction (XRD), Attenuated total reflection technique- Fourier transform infrared spectroscopy (ATR-FTIR), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM) and water contact angle (WCA) measurements were applied to study the alteration of ensuing membrane surface properties which shows the nanoparticles on the sample surface including the presence of Ti on PPM. The WCA decreased from 135° (PPM) to 90° (PPM5-TiO₂) and after UV irradiation, the WCA of PPM5-TiO₂ diminished from 90° to 40°. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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14 pages, 2222 KiB

Open AccessArticle

A Simulation Study on the Interaction Between Pollutant Nanoparticles and the Pulmonary Surfactant Monolayer

by Kai Yue, Xiaochen Sun, Jue Tang, Yiang Wei and Xinxin Zhang

Int. J. Mol. Sci. 2019, 20(13), 3281; https://doi.org/10.3390/ijms20133281 - 4 Jul 2019

Cited by 19 | Viewed by 3241

Abstract

A good understanding of the mechanism of interaction between inhaled pollutant nanoparticles (NPs) and the pulmonary surfactant monolayer is useful to study the impact of fine particulate matter on human health. In this work, we established coarse-grained models of four representative NPs with [...] Read more.

A good understanding of the mechanism of interaction between inhaled pollutant nanoparticles (NPs) and the pulmonary surfactant monolayer is useful to study the impact of fine particulate matter on human health. In this work, we established coarse-grained models of four representative NPs with different hydrophilicity properties in the air (i.e., CaSO₄, C, SiO₂, and C₆H₁₄O₂ NPs) and the pulmonary surfactant monolayer. Molecular dynamic simulations of the interaction during exhalation and inhalation breathing states were performed. The effects of NP hydrophilicity levels, NP structural properties, and cholesterol content in the monolayer on the behaviors of NP embedment or the transmembrane were analyzed by calculating the changes in potential energy, NP displacement, monolayer orderliness, and surface tension. Results showed that NPs can inhibit the ability of the monolayer to adjust surface tension. For all breathing states, the hydrophobic C NP cannot translocate across the monolayer and had the greatest influence on the structural properties of the monolayer, whereas the strongly hydrophilic SiO₂ and C₆H₁₄O₂ NPs can cross the monolayer with little impact. The semi-hydrophilic CaSO₄ NP can penetrate the monolayer only during the inhalation breathing state. The hydrophilic flaky NP shows the best penetration ability, followed by the rod-shaped NP and spherical NP in turn. An increase in cholesterol content of the monolayer led to improved orderliness and decreased fluidity of the membrane system due to enhanced intermolecular forces. Consequently, difficulty in crossing the monolayer increased for the NPs. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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15 pages, 2140 KiB

Open AccessArticle

Effects of Cholesterol on Water Permittivity of Biomimetic Ion Pair Amphiphile Bilayers: Interplay between Membrane Bending and Molecular Packing

by Wu-jhao Tien, Kun-you Chen, Fong-yin Huang and Chi-cheng Chiu

Int. J. Mol. Sci. 2019, 20(13), 3252; https://doi.org/10.3390/ijms20133252 - 2 Jul 2019

Cited by 6 | Viewed by 2883

Abstract

Ion pair amphiphile (IPA), a molecular complex composed of a pair of cationic and anionic amphiphiles, is an inexpensive phospholipid substitute to fabricate vesicles with various pharmaceutical applications. Modulating the physicochemical and permeation properties of IPA vesicles are important for carrier designs. Here, [...] Read more.

Ion pair amphiphile (IPA), a molecular complex composed of a pair of cationic and anionic amphiphiles, is an inexpensive phospholipid substitute to fabricate vesicles with various pharmaceutical applications. Modulating the physicochemical and permeation properties of IPA vesicles are important for carrier designs. Here, we applied molecular dynamics simulations to examine the cholesterol effects on the structures, mechanics, and water permittivity of hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS) and dodecyltrimethylammonium- hexadecylsulfate (DTMA-HS) IPA bilayers. Structural and mechanical analyses indicate that both IPA systems are in gel phase at 298 K. Adding cholesterol induces alkyl chain ordering around the rigid sterol ring and increases the cavity density within the hydrophilic region of both IPA bilayers. Furthermore, the enhanced alkyl chain ordering and the membrane deformation energy induced by cholesterol increase the permeation free energy penalty. In contrast, cholesterol has minor effects on the water local diffusivities within IPA membranes. Overall, the cholesterol reduces the water permittivity of rigid IPA membranes due to the synergistic effects of increased alkyl chain ordering and enhanced membrane mechanical modulus. The results provide molecular insights into the effects of molecular packing and mechanical deformations on the water permittivity of biomimetic IPA membranes, which is critical for designing IPA vesicular carriers. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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29 pages, 21478 KiB

Open AccessArticle

Electro-Kinetic Instability in a Laminar Boundary Layer Next to an Ion Exchange Membrane

by Pierre Magnico

Int. J. Mol. Sci. 2019, 20(10), 2393; https://doi.org/10.3390/ijms20102393 - 14 May 2019

Cited by 7 | Viewed by 3001

Abstract

The electro-kinetic instability in a pressure driven shear flow near an ion exchange membrane is considered. The electrochemical system, through which an electrical potential drop is applied, consists in a polarization layer in contact with the membrane and a bulk. The numerical investigation [...] Read more.

The electro-kinetic instability in a pressure driven shear flow near an ion exchange membrane is considered. The electrochemical system, through which an electrical potential drop is applied, consists in a polarization layer in contact with the membrane and a bulk. The numerical investigation contained two aspects: analysis of the instability modes and description of the Lagrangian transport of fluid and ions. Regarding the first aspect, the modes were analyzed as a function of the potential drop. The analysis revealed how the spatial distribution of forces controls the dynamics of vortex association and dissociation. In particular, the birth of a counter-clockwise vortex between two clockwise vortices, and the initiation of clusters constituting one or two envelopes wrapping a vortex group, were examined. In regards to the second aspect, the trajectories were computed with the fourth order Runge Kutta scheme for the time integration and with the biquadratric upstream scheme for the spatial and time interpolation of the fluid velocity and the ion flux. The results for the periodic mode showed two kinds of trajectories: the trochoidal motion and the longitudinal one coupled with a periodic transverse motion. For the aperiodic modes, other mechanisms appeared, such as ejection from the mixing layer, trapping by a growing vortex or merging vortices. The analysis of the local velocity field, the vortices’ shape, the spatial distribution of the forces and the ion flux components explained these trajectories. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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15 pages, 2255 KiB

Open AccessArticle

How Charge and Triple Size-Selective Membrane Separation of Peptides from Salmon Protein Hydrolysate Orientate their Biological Response on Glucose Uptake

by Loïc Henaux, Jacinthe Thibodeau, Geneviève Pilon, Tom Gill, André Marette and Laurent Bazinet

Int. J. Mol. Sci. 2019, 20(8), 1939; https://doi.org/10.3390/ijms20081939 - 20 Apr 2019

Cited by 20 | Viewed by 3802

Abstract

The valorization of by-products from natural organic sources is an international priority to respond to environmental and economic challenges. In this context, electrodialysis with filtration membrane (EDFM), a green and ultra-selective process, was used to separate peptides from salmon frame protein hydrolysate. For [...] Read more.

The valorization of by-products from natural organic sources is an international priority to respond to environmental and economic challenges. In this context, electrodialysis with filtration membrane (EDFM), a green and ultra-selective process, was used to separate peptides from salmon frame protein hydrolysate. For the first time, the simultaneous separation of peptides by three ultrafiltration membranes of different molecular-weight exclusion limits (50, 20, and 5 kDa) stacked in an electrodialysis system, allowed for the generation of specific cationic and anionic fractions with different molecular weight profiles and bioactivity responses. Significant decreases in peptide recovery, yield, and molecular weight (MW) range were observed in the recovery compartments depending on whether peptides had to cross one, two, or three ultrafiltration membranes. Moreover, the Cationic Recovery Compartment 1 fraction demonstrated the highest increase (42%) in glucose uptake on L6 muscle cells. While, in the anionic configuration, both Anionic Recovery Compartment 2 and Anionic Recovery Compartment 3 fractions presented a glucose uptake response in basal condition similar to the insulin control. Furthermore, Cationic Recovery Compartment 3 was found to contain inhibitory peptides. Finally, LC-MS analyses of the bioassay-guided bioactive fractions allowed us to identify 11 peptides from salmon by-products that are potentially responsible for the glucose uptake improvement. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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11 pages, 1286 KiB

Open AccessCommunication

An Investigation on the Application of Pulsed Electrodialysis Reversal in Whey Desalination

by Arthur Merkel and Amir M. Ashrafi

Int. J. Mol. Sci. 2019, 20(8), 1918; https://doi.org/10.3390/ijms20081918 - 18 Apr 2019

Cited by 33 | Viewed by 3930

Abstract

Electrodialysis (ED) is frequently used in the desalination of whey. However, the fouling onto the membrane surface decreases the electrodialysis efficiency. Pulsed Electrodialysis Reversal (PER), in which short pulses of reverse polarity are applied, is expected to decrease the fouling onto membrane surface [...] Read more.

Electrodialysis (ED) is frequently used in the desalination of whey. However, the fouling onto the membrane surface decreases the electrodialysis efficiency. Pulsed Electrodialysis Reversal (PER), in which short pulses of reverse polarity are applied, is expected to decrease the fouling onto membrane surface during ED. Three (PER) regimes were applied in the desalination of acid whey (pH ≤ 5) to study their effects on the membrane fouling and the ED efficiency. The PER regimes were compared to the conventional ED as the control. For each regime, two consecutive runs were performed without any cleaning step in-between to intensify the fouling. After the second run, the membranes were subjected to the Scanning electron microscope (SEM) imaging and contact angle measurement to investigate the fouling on the membrane surface in different regimes. The ED parameters in the case of conventional ED were almost the same in the first and the second runs. However, the parameters related to the ED efficiency including ED capacity, ash transfer, and ED time, were deteriorated when the PER regimes were applied. The contact angle values indicated that the fouling on the diluate side of anion exchange membranes was more intensified in conventional ED compared to the PER regimes. The SEM images also showed that the fouling on the diluate side of both cation and anion exchange membranes under PER regimes was reduced in respect to the conventional ED. However, the back transfer to the diluate compartment when the reverse pulse was applied is dominant and lowers the ED efficiency slightly when the PER is applied. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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22 pages, 6843 KiB

Open AccessArticle

Membrane Deformation and Its Effects on Flow and Mass Transfer in the Electromembrane Processes

by Giuseppe Battaglia, Luigi Gurreri, Girolama Airò Farulla, Andrea Cipollina, Antonina Pirrotta, Giorgio Micale and Michele Ciofalo

Int. J. Mol. Sci. 2019, 20(8), 1840; https://doi.org/10.3390/ijms20081840 - 13 Apr 2019

Cited by 21 | Viewed by 3963

Abstract

In the membrane processes, a trans-membrane pressure (TMP) may arise due to design features or operating conditions. In most applications, stacks for electrodialysis (ED) or reverse electrodialysis (RED) operate at low TMP (<0.1 bar); however, large stacks with non-parallel flow patterns and/or asymmetric [...] Read more.

In the membrane processes, a trans-membrane pressure (TMP) may arise due to design features or operating conditions. In most applications, stacks for electrodialysis (ED) or reverse electrodialysis (RED) operate at low TMP (<0.1 bar); however, large stacks with non-parallel flow patterns and/or asymmetric configurations can exhibit higher TMP values, causing membrane deformations and changes in fluid dynamics and transport phenomena. In this work, integrated mechanical and fluid dynamics simulations were performed to investigate the TMP effects on deformation, flow and mass transfer for a profiled membrane-fluid channel system with geometrical and mechanical features and fluid velocities representative of ED/RED conditions. First, a conservatively high value of TMP was assumed, and mechanical simulations were conducted to identify the geometry with the largest pitch to height ratio still able to bear this load without exhibiting a contact between opposite membranes. The selected geometry was then investigated under expansion and compression conditions in a TMP range encompassing most practical applications. Finally, friction and mass transfer coefficients in the deformed channel were predicted by computational fluid dynamics. Significant effects of membrane deformation were observed: friction and mass transfer coefficients increased in the compressed channel, while they decreased (though to a lesser extent) in the expanded channel. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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17 pages, 3150 KiB

Open AccessArticle

Positive Impact of Pulsed Electric Field on Lactic Acid Removal, Demineralization and Membrane Scaling during Acid Whey Electrodialysis

by Guillaume Dufton, Sergey Mikhaylin, Sami Gaaloul and Laurent Bazinet

Int. J. Mol. Sci. 2019, 20(4), 797; https://doi.org/10.3390/ijms20040797 - 13 Feb 2019

Cited by 50 | Viewed by 3720

Abstract

The drying of acid whey is hindered by its high mineral and organic acid contents, and their removal is performed industrially through expensive and environmentally impacting serial processes. Previous works demonstrated the ability to remove these elements by electrodialysis alone but with a [...] Read more.

The drying of acid whey is hindered by its high mineral and organic acid contents, and their removal is performed industrially through expensive and environmentally impacting serial processes. Previous works demonstrated the ability to remove these elements by electrodialysis alone but with a major concern—membrane scaling. In this study, two conditions of pulsed electric field (PEF) were tested and compared to conventional DC current condition to evaluate the potential of PEF to mitigate membrane scaling and to affect lactic acid and salt removals. The application of a PEF 25 s/25 s pulse/pause combination at an initial under-limiting current density allowed for decreasing the amount of scaling, the final system electrical resistance by 32%, and the relative energy consumption up to 33%. The use of pulsed current also enabled better lactic acid removal than the DC condition by 10% and 16% for PEF 50 s/10 s and 25 s/25 s, respectively. These results would be due to two mechanisms: (1) the mitigation of concentration polarization phenomenon and (2) the rinsing of the membranes during the pause periods. To the best of our knowledge, this was the first time that PEF current conditions were used on acid whey to both demineralize and deacidify it. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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Review

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16 pages, 1055 KiB

Open AccessReview

Casting a Wider Net: Differentiating between Inner Nuclear Envelope and Outer Nuclear Envelope Transmembrane Proteins

by Mark Tingey, Krishna C. Mudumbi, Eric C. Schirmer and Weidong Yang

Int. J. Mol. Sci. 2019, 20(21), 5248; https://doi.org/10.3390/ijms20215248 - 23 Oct 2019

Cited by 19 | Viewed by 5004

Abstract

The nuclear envelope (NE) surrounds the nucleus with a double membrane in eukaryotic cells. The double membranes are embedded with proteins that are synthesized on the endoplasmic reticulum and often destined specifically for either the outer nuclear membrane (ONM) or the inner nuclear [...] Read more.

The nuclear envelope (NE) surrounds the nucleus with a double membrane in eukaryotic cells. The double membranes are embedded with proteins that are synthesized on the endoplasmic reticulum and often destined specifically for either the outer nuclear membrane (ONM) or the inner nuclear membrane (INM). These nuclear envelope transmembrane proteins (NETs) play important roles in cellular function and participate in transcription, epigenetics, splicing, DNA replication, genome architecture, nuclear structure, nuclear stability, nuclear organization, and nuclear positioning. These vital functions are dependent upon both the correct localization and relative concentrations of NETs on the appropriate membrane of the NE. It is, therefore, important to understand the distribution and abundance of NETs on the NE. This review will evaluate the current tools and methodologies available to address this important topic. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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15 pages, 4708 KiB

Open AccessReview

Profiled Ion Exchange Membranes: A Comprehensible Review

by Sylwin Pawlowski, João G. Crespo and Svetlozar Velizarov

Int. J. Mol. Sci. 2019, 20(1), 165; https://doi.org/10.3390/ijms20010165 - 4 Jan 2019

Cited by 77 | Viewed by 6783

Abstract

Profiled membranes (also known as corrugated membranes, micro-structured membranes, patterned membranes, membranes with designed topography or notched membranes) are gaining increasing academic and industrial attention and recognition as a viable alternative to flat membranes. So far, profiled ion exchange membranes have shown to [...] Read more.

Profiled membranes (also known as corrugated membranes, micro-structured membranes, patterned membranes, membranes with designed topography or notched membranes) are gaining increasing academic and industrial attention and recognition as a viable alternative to flat membranes. So far, profiled ion exchange membranes have shown to significantly improve the performance of reverse electrodialysis (RED), and particularly, electrodialysis (ED) by eliminating the spacer shadow effect and by inducing hydrodynamic changes, leading to ion transport rate enhancement. The beneficial effects of profiled ion exchange membranes are strongly dependent on the shape of their profiles (corrugations/patterns) as well as on the flow rate and salts’ concentration in the feed streams. The enormous degree of freedom to create new profile geometries offers an exciting opportunity to improve even more their performance. Additionally, the advent of new manufacturing methods in the membrane field, such as 3D printing, is anticipated to allow a faster and an easier way to create profiled membranes with different and complex geometries. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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Other

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4 pages, 535 KiB

Open AccessCorrection

Correction: Abbasi, A. et al. Poly(2,6-dimethyl-1,4-phenylene oxide)-Based Hydroxide Exchange Separator Membranes for Zinc-Air Battery. Int. J. Mol. Sci. 2019, 20, 3678

by Ali Abbasi, Soraya Hosseini, Anongnat Somwangthanaroj, Ahmad Azmin Mohamad and Soorathep Kheawhom

Int. J. Mol. Sci. 2020, 21(2), 377; https://doi.org/10.3390/ijms21020377 - 7 Jan 2020

Cited by 3 | Viewed by 2302

Abstract

The authors would like to make the following corrections to their paper published in the International Journal of Molecular Science [...] Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems)

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