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A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Physical Chemistry and Chemical Physics".

Deadline for manuscript submissions: closed (15 March 2022) | Viewed by 34033

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Prof. Dr. Victor V. Nikonenko

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Department of Physical Chemistry, Kuban State University, 149 Stavropolskaya st., 350040 Krasnodar, Russia
Interests: ion-exchange membranes; structure-property relationships; transport phenomena; experiment; modelling
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Special Issue Information

Dear Colleagues,

The scope of this Special Issue involves a large number of topics in the field of membrane science. We welcome papers reporting experimental studies and mathematical modeling providing new knowledge on the mechanisms of ion and molecule transport in artificial and living systems; the description of ion and molecule transport through all kinds of membranes, biological, and artificial ones; similarities in behavior of biological and artificial membranes; biomimetic structural features of artificial membranes and their impact on membrane properties and performance for separation processes; generalities and case studies in the field of material structure–properties relationships; physicochemical and chemicophysical aspects of ion and molecule transport; thermodynamics and irreversible thermodynamics description; equilibria and kinetics of transport processes in membrane systems; coupling of ion and molecule transport with chemical reactions and catalysis; impact of forced and natural convection on ion and molecule transport; the mechanisms of electric current-induced convection and its impact on ion and molecule transport across membranes; concentration polarization and coupled effects occurring in membrane systems under the action of external pressure and electric driving forces (external pressure and electric potential gradients applied to a membrane); the physicochemical and chemicophysical aspects of transport, separation, purification, and fractionation of organic acids, bioactive compounds, ampholytes, nutrients in membrane systems.

The purpose of this Special Issue is to collect original research articles and reviews that concern the topic of membrane science. This is the third edition of this topic, and it follows on from past and very successful collection on “Ion and Molecule Transport in Membrane Systems” (https://www.mdpi.com/journal/ijms/special_issues/Ion_Membrane) and "Ion and Molecule Transport in Membrane Systems 2.0" (https://www.mdpi.com/journal/ijms/special_issues/Ion_Membranes). Contributions from different fields of research at a molecular level are welcomed. Our aim is for this new Special Issue to collect more great manuscripts in the membrane area.

Prof. Dr. Victor V. Nikonenko
Guest Editor

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Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

ion and molecular transport
physical chemistry
chemical physics
transport mechanisms
living systems
biological and artificial membranes
biomimetic structure
structure–property relationships
thermodynamics
irreversible thermodynamics
equilibriums
kinetics
catalysis
organic acids
bioactive compounds
ampholytes
nutrients
separation

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Related Special Issues

Ion and Molecule Transport in Membrane Systems in International Journal of Molecular Sciences (22 articles)
Ion and Molecule Transport in Membrane Systems 2.0 in International Journal of Molecular Sciences (19 articles)
Ion and Molecule Transport in Membrane Systems 4.0 in International Journal of Molecular Sciences (7 articles)
Ion and Molecule Transport in Membrane Systems 5.0 in International Journal of Molecular Sciences (5 articles)

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Editorial

Jump to: Research, Review

4 pages, 209 KiB

Open AccessEditorial

Ion and Molecule Transport in Membrane Systems 3.0 and 4.0

by Victor Nikonenko and Natalia Pismenskaya

Int. J. Mol. Sci. 2023, 24(9), 8211; https://doi.org/10.3390/ijms24098211 - 4 May 2023

Cited by 2 | Viewed by 1338

Abstract

This book is a collection of papers published in the 3rd and 4th Special Issues of the International Journal of Molecular Sciences under the standard title, “Ion and Molecule Transport in Membrane Systems” [...] Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

Research

Jump to: Editorial, Review

19 pages, 3148 KiB

Open AccessArticle

Modification of Thin Film Composite PVA/PAN Membranes for Pervaporation Using Aluminosilicate Nanoparticles

by Katsiaryna S. Burts, Tatiana V. Plisko, Vladimir G. Prozorovich, Galina B. Melnikova, Andrei I. Ivanets and Alexandr V. Bildyukevich

Int. J. Mol. Sci. 2022, 23(13), 7215; https://doi.org/10.3390/ijms23137215 - 29 Jun 2022

Cited by 9 | Viewed by 2097

Abstract

The effect of the modification of the polyvinyl alcohol (PVA) selective layer of thin film composite (TFC) membranes by aluminosilicate (Al₂O₃·SiO₂) nanoparticles on the structure and pervaporation performance was studied. For the first time, PVA-Al₂O₃·SiO₂/polyacrylonitrile (PAN) thin film nanocomposite (TFN) membranes for pervaporation separation of ethanol/water mixture were developed via the formation of the selective layer in dynamic mode. Selective layers of PVA/PAN and PVA-Al₂O₃·SiO₂/PAN membranes were formed via filtration of PVA aqueous solutions or PVA-Al₂O₃·SiO₂ aqueous dispersions through the ultrafiltration PAN membrane for 10 min at 0.3 MPa in dead-end mode. Average particle size and zeta potential of aluminosilicate nanoparticles in PVA aqueous solution were analyzed using the dynamic light scattering technique. Structure and surface properties of membranes were studied using scanning electron microscopy (SEM), atomic force microscopy (AFM) and water contact angle measurements. Membrane performance was investigated in pervaporation dehydration of ethanol/water mixtures in the broad concentration range. It was found that flux of TFN membranes decreased with addition of Al₂O₃·SiO₂ nanoparticles into the selective layer due to the increase in selective layer thickness. However, ethanol/water separation factor of TFN membranes was found to be significantly higher compared to the reference TFC membrane in the whole range of studied ethanol/water feed mixtures with different concentrations, which is attributed to the increase in membrane hydrophilicity. It was found that developed PVA-Al₂O₃·SiO₂/PAN TFN membranes were more stable in the dehydration of ethanol in the whole range of investigated concentrations as well as at different temperatures of the feed mixtures (25 °C, 35 °C, 50 °C) compared to the reference membrane which is due to the additional cross-linking of the selective layer by formation hydrogen and donor-acceptor bonds between aluminosilicate nanoparticles and PVA macromolecules. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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16 pages, 5378 KiB

Open AccessArticle

Recovery of Hydrochloric Acid from Industrial Wastewater by Diffusion Dialysis Using a Spiral-Wound Module

by Arthur Merkel, Ladislav Čopák, Daniil Golubenko, Lukáš Dvořák, Matej Vavro, Andrey Yaroslavtsev and Libor Šeda

Int. J. Mol. Sci. 2022, 23(11), 6212; https://doi.org/10.3390/ijms23116212 - 1 Jun 2022

Cited by 6 | Viewed by 2845

Abstract

In the present study, the possibility of using a spiral-wound diffusion dialysis module was studied for the separation of hydrochloric acid and Zn²⁺, Ni²⁺, Cr³⁺, and Fe²⁺ salts. Diffusion dialysis recovered 68% of free HCl from the spent pickling solution contaminated with heavy-metal-ion salts. A higher volumetric flowrate of the stripping medium recovered a more significant portion of free acid, namely, 77%. Transition metals (Fe, Ni, Cr) apart from Zn were rejected by >85%. Low retention of Zn (35%) relates to the diffusion of negatively charged chloro complexes through the anion-exchange membrane. The mechanical and transport properties of dialysis FAD-PET membrane under accelerated degradation conditions was investigated. Long-term tests coupled with the economic study have verified that diffusion dialysis is a suitable method for the treatment of spent acids, the salts of which are well soluble in water. Calculations predict significant annual OPEX savings, approximately up to 58%, favouring diffusion dialysis for implementation into wastewater management. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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22 pages, 3954 KiB

Open AccessArticle

High Diffusion Permeability of Anion-Exchange Membranes for Ammonium Chloride: Experiment and Modeling

by Ekaterina Skolotneva, Kseniia Tsygurina, Semyon Mareev, Ekaterina Melnikova, Natalia Pismenskaya and Victor Nikonenko

Int. J. Mol. Sci. 2022, 23(10), 5782; https://doi.org/10.3390/ijms23105782 - 21 May 2022

Cited by 10 | Viewed by 3281

Abstract

It is known that ammonium has a higher permeability through anion exchange and bipolar membranes compared to K⁺ cation that has the same mobility in water. However, the mechanism of this high permeability is not clear enough. In this study, we develop a mathematical model based on the Nernst–Planck and Poisson’s equations for the diffusion of ammonium chloride through an anion-exchange membrane; proton-exchange reactions between ammonium, water and ammonia are taken into account. It is assumed that ammonium, chloride and OH⁻ ions can only pass through membrane hydrophilic pores, while ammonia can also dissolve in membrane matrix fragments not containing water and diffuse through these fragments. It is found that due to the Donnan exclusion of H⁺ ions as coions, the pH in the membrane internal solution increases when approaching the membrane side facing distilled water. Consequently, there is a change in the principal nitrogen-atom carrier in the membrane: in the part close to the side facing the feed NH₄Cl solution (pH < 8.8), it is the NH₄⁺ cation, and in the part close to distilled water, NH₃ molecules. The concentration of NH₄⁺ reaches almost zero at a point close to the middle of the membrane cross-section, which approximately halves the effective thickness of the diffusion layer for the transport of this ion. When NH₃ takes over the nitrogen transport, it only needs to pass through the other half of the membrane. Leaving the membrane, it captures an H+ ion from water, and the released OH⁻ moves towards the membrane side facing the feed solution to meet the NH₄⁺ ions. The comparison of the simulation with experiment shows a satisfactory agreement. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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22 pages, 3080 KiB

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Mathematical Modeling of Monovalent Permselectivity of a Bilayer Ion-Exchange Membrane as a Function of Current Density

by Andrey Gorobchenko, Semyon Mareev and Victor Nikonenko

Int. J. Mol. Sci. 2022, 23(9), 4711; https://doi.org/10.3390/ijms23094711 - 24 Apr 2022

Cited by 16 | Viewed by 2429

Abstract

Modification of an ion-exchange membrane with a thin layer, the charge of which is opposite to the charge of the substrate membrane, has proven to be an effective approach to obtaining a composite membrane with permselectivity towards monovalent ions. However, the mechanism of permselectivity is not clear enough. We report a 1D model based on the Nernst–Planck–Poisson equation system. Unlike other similar models, we introduce activity coefficients, which change when passing from one layer of the membrane to another. This makes it possible to accurately take into account the fact that the substrate membranes usually selectively sorb multiply charged counterions. We show that the main cause for the change in the permselectivity coefficient, P_1/2, with increasing current density, j, is the change in the membrane/solution layer, which controls the fluxes of the competing mono- and divalent ions. At low current densities, counterion fluxes are controlled by transfer through the substrate membrane, which causes selective divalent ion transfer. When the current increases, the kinetic control goes first to the modification layer (which leads to the predominant transfer of monovalent ions) and then, at currents close to the limiting current, to the depleted diffusion layer (which results in a complete loss of the permselectivity). Thus, the dependence P_1/2 − j passes through a maximum. An analytical solution is obtained for approximate assessment of the maximum value of P_1/2 and the corresponding fluxes of the competing ions. The maximum P_1/2 values, plotted as a function of the Na⁺ ion current density at which this maximum is reached, gives the theoretical trade-off curve between the membrane permselectivity and permeability of the bilayer monovalent selective ion-exchange membrane under consideration. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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15 pages, 2042 KiB

Open AccessArticle

Mathematical Description of the Increase in Selectivity of an Anion-Exchange Membrane Due to Its Modification with a Perfluorosulfonated Ionomer

by Anton Kozmai, Natalia Pismenskaya and Victor Nikonenko

Int. J. Mol. Sci. 2022, 23(4), 2238; https://doi.org/10.3390/ijms23042238 - 17 Feb 2022

Cited by 7 | Viewed by 2142

Abstract

In this paper, we simulate the changes in the structure and transport properties of an anion-exchange membrane (CJMA-7, Hefei Chemjoy Polymer Materials Co. Ltd., China) caused by its modification with a perfluorosulfonated ionomer (PFSI). The modification was made in several stages and included keeping the membrane at a low temperature, applying a PFSI solution on its surface, and, subsequently, drying it at an elevated temperature. We applied the known microheterogeneous model with some new amendments to simulate each stage of the membrane modification. It has been shown that the PFSI film formed on the membrane-substrate does not affect significantly its properties due to the small thickness of the film (≈4 µm) and similar properties of the film and substrate. The main effect is caused by the fact that PFSI material “clogs” the macropores of the CJMA-7 membrane, thereby, blocking the transport of coions through the membrane. In this case, the membrane microporous gel phase, which exhibits a high selectivity to counterions, remains the primary pathway for both counterions and coions. Due to the above modification of the CJMA-7 membrane, the coion (Na⁺) transport number in the membrane equilibrated with 1 M NaCl solution decreased from 0.11 to 0.03. Thus, the modified membrane became comparable in its transport characteristics with more expensive IEMs available on the market. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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23 pages, 6237 KiB

Open AccessArticle

Experimental and Theoretical Study of an Autowave Process in a Magnetic Fluid

by Vladimir Chekanov and Anna Kovalenko

Int. J. Mol. Sci. 2022, 23(3), 1642; https://doi.org/10.3390/ijms23031642 - 31 Jan 2022

Cited by 6 | Viewed by 2317

Abstract

Magnetic fluid (MF) is a colloidal system consisting of ferromagnetic particles (magnetite) with a diameter of ~10 nm suspended in a dispersion medium of a carrier fluid (for example, kerosene). A distinctive feature of magnetic fluid is the fact that when an electric field is applied to it using two electrodes, thin layers consisting of close-packed particles of the dispersed phase are formed in the regions near the surface of both electrodes. These layers significantly affect the macroscopic properties of the colloidal system. In this work, the interpretation of the near-electrode layer is for the first time given as a new type of liquid membrane, in which the particles of the dispersed phase become charged with the opposite sign. On the basis of experimental studies, we propose a physicochemical mechanism of the autowave process in a cell with a magnetic fluid. It is based on the idea of oppositely recharging colloidal particles of magnetite in a liquid membrane. A mathematical model of an autowave process, which is described by a system of coupled partial differential equations of Nernst–Planck–Poisson and Navier–Stokes with appropriate boundary conditions, is proposed for the first time. One-dimensional, two-dimensional, and three-dimensional versions of the model are considered. The dependence of the frequency of concentration fluctuations on the stationary voltage between the electrodes was obtained, and the time of formation of a liquid membrane was estimated. Qualitative agreement between theoretical and experimental results has been established. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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9 pages, 23696 KiB

Open AccessArticle

Gas-Transport Characteristics of PdCu–Nb–PdCu Membranes Modified with Nanostructured Palladium Coating

by Iliya Petriev, Polina Pushankina, Nikita Shostak and Mikhail Baryshev

Int. J. Mol. Sci. 2022, 23(1), 228; https://doi.org/10.3390/ijms23010228 - 25 Dec 2021

Cited by 9 | Viewed by 2663

Abstract

A method for obtaining composite gas-diffusion PdCu–Nb–PdCu membranes modified with a nanostructured crystalline coating was developed to increase the performance of Nb-based membranes. A modifying functional layer with a controlled size and composition was synthesized by electrochemical deposition, which made it possible to determine a certain geometric shape for palladium nanocrystallites. Developed PdCu–Nb–PdCu membranes have demonstrated flux values up to 0.232 mmol s⁻¹ m⁻² in the processes of diffusion purification of hydrogen at 400 °C. A very significant difference in the hydrogen fluxes through the modified and non-modified composite PdCu–Nb–PdCu membranes reached 1.73 times at the lower threshold temperature of 300 °C. Cu doping of protective layer did not affect the selective properties of the membranes, which was confirmed by the obtained high selectivity values up to 1323, and made it possible to reduce the noble metal content. The research data indicate that the modification of the membrane surface significantly accelerates the hydrogen transfer process at sufficiently low temperatures due to the acceleration of dissociative–associative processes on the surface. The reported approach demonstrates new possibilities for creating productive and cost-efficient membranes based on niobium. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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23 pages, 3373 KiB

Open AccessArticle

Influence of Electroconvection on Chronopotentiograms of an Anion-Exchange Membrane in Solutions of Weak Polybasic Acid Salts

by Natalia Pismenskaya, Olesya Rybalkina, Ilya Moroz, Semen Mareev and Victor Nikonenko

Int. J. Mol. Sci. 2021, 22(24), 13518; https://doi.org/10.3390/ijms222413518 - 16 Dec 2021

Cited by 13 | Viewed by 2307

Abstract

Visualization of electroconvective (EC) vortices at the undulated surface of an AMX anion-exchange membrane (Astom, Osaka, Japan) was carried out in parallel with the measurement of chronopotentiograms. Weak polybasic acid salts, including 0.02 M solutions of tartaric (NaHT), phosphoric (NaH₂PO₄), and citric (NaH₂Cit) acids salts, and NaCl were investigated. It was shown that, for a given current density normalized to the theoretical limiting current calculated by the Leveque equation (i/i_lim^theor), EC vortex zone thickness, d_EC, decreases in the order NaCl > NaHT > NaH₂PO₄ > NaH₂Cit. This order is inverse to the increase in the intensity of proton generation in the membrane systems under study. The higher the intensity of proton generation, the lower the electroconvection. This is due to the fact that protons released into the depleted solution reduce the space charge density, which is the driver of EC. In all studied systems, a region in chronopotentiograms between the rapid growth of the potential drop and the attainment of its stationary values corresponds to the appearance of EC vortex clusters. The amplitude of the potential drop oscillations in the chronopotentiograms is proportional to the size of the observed vortex clusters. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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15 pages, 2903 KiB

Open AccessArticle

Study on the Effectiveness of Simultaneous Recovery and Concentration of 1-Ethyl-3-methylimidazolium Chloride Ionic Liquid by Electrodialysis with Heterogeneous Ion-Exchange Membranes

by Dorota Babilas, Anna Kowalik-Klimczak and Piotr Dydo

Int. J. Mol. Sci. 2021, 22(23), 13014; https://doi.org/10.3390/ijms222313014 - 1 Dec 2021

Cited by 2 | Viewed by 1967

Abstract

Due to the extensive range of ionic liquids (ILs) used in industry, an efficient recovery method is needed. In this study, the effectiveness of a simultaneous concentration and recovery method was investigated for 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), an IL that was recovered using electrodialysis (ED). The optimal operational parameters for electrodialytic recovery were determined empirically. The variables that were investigated included the concentration of IL, applied voltage, linear flow velocity and the diluate-to-concentrate volume ratio. The recovery of [Emim]Cl, the concentration degree, the [Emim]Cl flux across membranes, the current efficiency, as well as the energy consumption were determined. The results of the experiments confirmed that [Emim]Cl concentration and recovery can be achieved using ED. The highest ED efficiency was obtained when a 2 V electric potential per one membrane pair was applied, using a 2 cm/s linear flow velocity, and by adjusting to 0.2 M IL in the feed solution. By using ED, a 2.35-fold concentration of [Emim]Cl with a recovery of 90.4% could be achieved when the diluate-to-concentrate volume ratio was 2. On the other hand, a 3.35-fold concentration of [Emim]Cl with a recovery of 81.7% could be obtained when the diluate-to-concentrate volume ratio was increased to 5. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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14 pages, 15633 KiB

Open AccessArticle

Semi-Continuous Desalination and Concentration of Small-Volume Samples

by David Tichý and Zdeněk Slouka

Int. J. Mol. Sci. 2021, 22(23), 12904; https://doi.org/10.3390/ijms222312904 - 29 Nov 2021

Cited by 3 | Viewed by 1733

Abstract

Electrodialysis is an electric-field-mediated process separating ions exploiting selective properties of ion-exchange membranes. The ion-exchange membranes create an ion-depleted zone in an electrolyte solution adjacent to the membrane under DC polarization. We constructed a microfluidic system that uses the ion-depleted zone to separate ions from the processed water solution. We tested the separation performance by desalting a model KCl solution spiked with fluorescein for direct observation. We showed both visually and by measuring the conductivity of the output solutions that the system can work in three modes of operation referred to as continuous desalination, desalination by accumulation, and unsuccessful desalination. The mode of operation can easily be set by changing the control parameters. The desalination factors for the model KCl solution reached values from 80 to 100%, depending on the mode of operation. The concentration factor, given as a ratio of concentrate-to-feed concentrations, reached zero for desalination by accumulation when only diluate was produced. The water recovery, therefore, was infinite at these conditions. Independent control of the diluate and concentrate flow rates and the DC voltage turned our system into a versatile platform, enabling us to set proper conditions to process various samples. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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21 pages, 3384 KiB

Open AccessArticle

Midazolam’s Effects on Delayed-Rectifier K⁺ Current and Intermediate-Conductance Ca²⁺-Activated K⁺ Channel in Jurkat T-lymphocytes

by Ning-Ping Foo, Yu-Fan Liu, Ping-Ching Wu, Chung-Hsi Hsing, Bu-Miin Huang and Edmund-Cheung So

Int. J. Mol. Sci. 2021, 22(13), 7198; https://doi.org/10.3390/ijms22137198 - 4 Jul 2021

Cited by 3 | Viewed by 2987

Abstract

Midazolam (MDZ) could affect lymphocyte immune functions. However, the influence of MDZ on cell’s K⁺ currents has never been investigated. Thus, in the present study, the effects of MDZ on Jurkat T lymphocytes were studied using the patch-clamp technique. Results showed that MDZ suppressed the amplitude of delayed-rectifier K⁺ current (I_K(DR)) in concentration-, time-, and state-dependent manners. The IC₅₀ for MDZ-mediated reduction of I_K(DR) density was 5.87 μM. Increasing MDZ concentration raised the rate of current-density inactivation and its inhibitory action on I_K(DR) density was estimated with a dissociation constant of 5.14 μM. In addition, the inactivation curve of I_K(DR) associated with MDZ was shifted to a hyperpolarized potential with no change on the slope factor. MDZ-induced inhibition of I_K(DR) was not reversed by flumazenil. In addition, the activity of intermediate-conductance Ca²⁺-activated K⁺ (IK_Ca) channels was suppressed by MDZ. Furthermore, inhibition by MDZ on both I_K(DR) and IK_Ca-channel activity appeared to be independent from GABAA receptors and affected immune-regulating cytokine expression in LPS/PMA-treated human T lymphocytes. In conclusion, MDZ suppressed current density of I_K(DR) in concentration-, time-, and state-dependent manners in Jurkat T-lymphocytes and affected immune-regulating cytokine expression in LPS/PMA-treated human T lymphocytes. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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15 pages, 3366 KiB

Open AccessArticle

Modeling the Formation of Gas Bubbles inside the Pores of Reactive Electrochemical Membranes in the Process of the Anodic Oxidation of Organic Compounds

by Semyon Mareev, Ekaterina Skolotneva, Marc Cretin and Victor Nikonenko

Int. J. Mol. Sci. 2021, 22(11), 5477; https://doi.org/10.3390/ijms22115477 - 22 May 2021

Cited by 5 | Viewed by 1798

Abstract

The use of reactive electrochemical membranes (REM) in flow-through mode during the anodic oxidation of organic compounds makes it possible to overcome the limitations of plate anodes: in the case of REM, the area of the electrochemically active surface is several orders of magnitude larger, and the delivery of organic compounds to the reaction zone is controlled by convective flow rather than diffusion. The main problem with REM is the formation of fouling and gas bubbles in the pores, which leads to a decrease in the efficiency of the process because the hydraulic resistance increases and the electrochemically active surface is shielded. This work aims to study the processes underlying the reduction in the efficiency of anodic oxidation, and in particular the formation of gas bubbles and the recharge of the REM pore surface at a current density exceeding the limiting kinetic value. We propose a simple one-dimensional non-stationary model of the transport of diluted species during the anodic oxidation of paracetamol using REM to describe the above effects. The processing of the experimental data was carried out. It was found that the absolute value of the zeta potential of the pore surface decreases with time, which leads to a decrease in the permeate flux due to a reduction in the electroosmotic flow. It was shown that in the solution that does not contain organic components, gas bubbles form faster and occupy a larger pore fraction than in the case of the presence of paracetamol; with an increase in the paracetamol concentration, the gas fraction decreases. This behavior is due to a decrease in the generation of oxygen during the recombination reaction of the hydroxyl radicals, which are consumed in the oxidation reaction of the organic compounds. Because the presence of bubbles increases the hydraulic resistance, the residence time of paracetamol—and consequently its degradation degree—increases, but the productivity goes down. The model has predictive power and, after simple calibration, can be used to predict the performance of REM anodic oxidation systems. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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Review

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40 pages, 22594 KiB

Open AccessReview

Ion and Molecular Transport in Solid Electrolytes Studied by NMR

by Vitaly I. Volkov, Alexander V. Chernyak, Nikita A. Slesarenko and Irina A. Avilova

Int. J. Mol. Sci. 2022, 23(9), 5011; https://doi.org/10.3390/ijms23095011 - 30 Apr 2022

Cited by 7 | Viewed by 2660

Abstract

NMR is the method of choice for molecular and ionic structures and dynamics investigations. The present review is devoted to solvation and mobilities in solid electrolytes, such as ion-exchange membranes and composite materials, based on cesium acid sulfates and phosphates. The applications of high-resolution NMR, solid-state NMR, NMR relaxation, and pulsed field gradient ¹H, ⁷Li, ¹³C, ¹⁹F, ²³Na, ³¹P, and ¹³³Cs NMR techniques are discussed. The main attention is paid to the transport channel morphology, ionic hydration, charge group and mobile ion interaction, and translation ions and solvent mobilities in different spatial scales. Self-diffusion coefficients of protons and Li⁺, Na⁺, and Cs⁺ cations are compared with the ionic conductivity data. The microscopic ionic transfer mechanism is discussed. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 3.0)

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