Special Issue "Electro-membrane Processes for Clean Water and Sustainable Energy"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Chemistry".

Deadline for manuscript submissions: closed (30 September 2018).

Special Issue Editor

Prof. Dr. Svetlozar G. Velizarov
Website
Guest Editor
Laboratory for Green Chemistry (LAQV), Faculty of Science and Technology, New University of Lisbon, 2829-516 Caparica, Portugal
Interests: clean (mainly membrane-assisted) (bio)chemical processes and technologies; electro-membrane processes; water treatment, sustainable salinity gradient-based (“blue”) energy generation and/or storage
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Special Issue Information

Dear Colleagues,

There is an increasing worldwide interest in the use of electro-membrane processes for clean water and renewable electrochemical energy harvesting and storage. These processes range from classical membrane electrolysis and electrodialysis to emerging applications, such as reverse electrodialysis, membrane capacitive deionization, redox flow batteries, microbial and enzymatic fuel cells, and ion exchange membrane (bio)reactors. This interest has inspired fundamental and applied research on improving the properties of their “key” components: The ion exchange membranes, as well as on process modelling, optimization and validation on a laboratory or industrial scale, with the ultimate goal being their practical implementation. The latter has encouraged both academia and various commercial companies in growing activities to develop tailored membrane products best suited to satisfy specific process requirements, such as low electric resistance, monovalent ion perm-selectivity, antifouling properties, hollow-fiber ion exchange membrane arrangement, as well as a number of novel hybrid processes.

This Special Issue of the journal Applied Sciences, “Electro-Membrane Processes for Clean Water and Sustainable Energy”, aims at covering recent advances in the development of these research topics.

Dr. Svetlozar G. Velizarov
Guest Editor

Manuscript Submission Information

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Keywords

  • Ion exchange membrane
  • Membrane electrolysis
  • (Reverse) electrodialysis
  • Salinity gradient power
  • Membrane capacitive deionization
  • Redox flow batteries
  • Membrane fuel cells
  • Donnan dialysis
  • Diffusion dialysis
  • Hybrid processes
  • Ion exchange membrane (bio)reactors

Published Papers (7 papers)

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Research

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Open AccessArticle
A Systematic Performance History Analysis of a Chlor-Alkali Membrane Electrolyser under Industrial Operating Conditions
Appl. Sci. 2019, 9(2), 284; https://doi.org/10.3390/app9020284 - 15 Jan 2019
Cited by 1
Abstract
The history of the potential and electrical current evolution of an industrial chlor-alkali membrane electrolyser is a powerful tool to track its operational efficiency progress over time and for deciding the required maintenance instants. For this reason, the performance of a dedicated industrial [...] Read more.
The history of the potential and electrical current evolution of an industrial chlor-alkali membrane electrolyser is a powerful tool to track its operational efficiency progress over time and for deciding the required maintenance instants. For this reason, the performance of a dedicated industrial NaCl electrolyser was systematically analysed as a function of its service time for about 8 years, recording the cell potential versus current density. The documented potential values were normalized taking into account the initial current density, which allowed to reduce data scattering due to small fluctuations of the current density values. The ohmic overpotential contribution, associated to the ion-exchange membranes, showed an average relative error smaller than 3% and the activation overpotential, related to the electrodes’ performance, displayed an average relative error of 6%. Thus, the proposed approach enables rigorous assessing of the performance of industrial chlor-alkali membrane electrolysers for adequate scheduling of their maintenance, which leads to significant operational and economic improvements of the chlor-alkali process. Full article
(This article belongs to the Special Issue Electro-membrane Processes for Clean Water and Sustainable Energy)
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Open AccessArticle
The Effects of Acidic, Alkaline, and Neutral Anolytes on Electrochemical Seawater Deoxygenation
Appl. Sci. 2018, 8(11), 2280; https://doi.org/10.3390/app8112280 - 18 Nov 2018
Abstract
Electrochemical deoxygenation of seawater has advantages over available chemical and physical methods. For seawater deoxygenation, acidic, neutral, or alkaline anolytes can be used. The effects of acidic, alkaline, and neutral buffered and non-buffered anolytes were studied in two compartment deoxygenation cells. The pH, [...] Read more.
Electrochemical deoxygenation of seawater has advantages over available chemical and physical methods. For seawater deoxygenation, acidic, neutral, or alkaline anolytes can be used. The effects of acidic, alkaline, and neutral buffered and non-buffered anolytes were studied in two compartment deoxygenation cells. The pH, conductivity, H2O2 production, and current were measured throughout the experiments. The optimum applied potentials for oxygen reduction were between 1.9 V–2.2 V, giving water as product; reducing the applied potential also resulted in the formation of H2O2. Analysis after the experiments using a scanning electron microscope with electron-dispersive X-ray spectroscopy showed that both the silver mesh and the cation exchange membrane remained stable during the experiments. The use of alkaline anolytes resulted in the maximum oxygen removal with minimal side reactions in the cell. Full article
(This article belongs to the Special Issue Electro-membrane Processes for Clean Water and Sustainable Energy)
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Open AccessFeature PaperArticle
Inorganic Pseudo Ion Exchange Membranes—Concepts and Preliminary Experiments
Appl. Sci. 2018, 8(11), 2142; https://doi.org/10.3390/app8112142 - 02 Nov 2018
Cited by 2
Abstract
Reverse electrodialysis (RED) is a method to produce electricity from the reversible mixing of two salt solutions with different concentrations. RED was first employed for energy generation using sea and river water. New fields of application are energy storage and heat-to-power conversion. In [...] Read more.
Reverse electrodialysis (RED) is a method to produce electricity from the reversible mixing of two salt solutions with different concentrations. RED was first employed for energy generation using sea and river water. New fields of application are energy storage and heat-to-power conversion. In energy storage applications, a stack operates in ED mode during charge and in RED mode during discharge. In a heat-to-power system, the RED stack produces electricity and the outgoing solutions are returned to their original concentrations in a heat-driven regenerator. In both new applications, the salt solutions are circulated and there is a free choice of the combination of salt and membranes for optimal performance. However, classical polymer-based membranes have some disadvantages: they are less suited for operation at higher temperatures, have reduced permselectivity at higher concentrations, and are rather permeable to water, causing an imbalance of the feed waters. We developed a new concept of pseudo-membrane (PM): a metal sheet (sometimes covered with an insoluble salt) on which opposite electrochemical reactions occur at each side of the metal surface. Because a PM is dissolving at one side and growing at the other side during operation, the current should be inverted periodically. We tested a zinc sheet as a pseudo cation exchange membrane for Zn2+ ions and a silver chloride–covered silver plate as a pseudo anion exchange membrane for Cl ions in three steps. First, a stack was built with Ag/AgCl membranes in combination with normal cation exchange membranes and operated with NaCl solutions. The next stack was based on Zn membranes together with normal anion exchange membranes. This stack was fed with ZnCl2 solutions. Finally, we tested a stack with zinc and Ag/AgCl pseudo-membranes with a ZnCl2 solution. The latter RED system worked; however, after standing for one night, the stack did not function and appeared to be damaged by redox reactions. This failure was the basis for general considerations about the possibilities of ED and RED hybrid stacks, consisting of a combination of classical and pseudo ion exchange membranes. Finally, we consider the possibility of using intercalation electrodes as a pseudo-membrane. Full article
(This article belongs to the Special Issue Electro-membrane Processes for Clean Water and Sustainable Energy)
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Open AccessArticle
Electricity Production from Marine Water by Sulfide-Driven Fuel Cell
Appl. Sci. 2018, 8(10), 1926; https://doi.org/10.3390/app8101926 - 15 Oct 2018
Abstract
While there is a universal trend to replace fossil fuels at least partially, renewable fuels seem to impose new solutions. Hydrogen sulfide, typical for closed water ponds such as the Black Sea, seems to offer one namely, a new sulfide-driven fuel cell providing [...] Read more.
While there is a universal trend to replace fossil fuels at least partially, renewable fuels seem to impose new solutions. Hydrogen sulfide, typical for closed water ponds such as the Black Sea, seems to offer one namely, a new sulfide-driven fuel cell providing for exchange of OH anions across the membrane by use of hydrogen sulfide in natural marine water. When tested in batch and continuous operation modes, this solution showed that the initial sulfide concentration needed to achieve results of practical value was within 200 to 300 mg dm−3. The predominating final products of the energy production process were sulfite and sulfate ions. Very low overpotentials and mass transfer resistances were observed. The mass balance and the electrochemical parameters showed about 30% efficiency in sulfate ions as the final product. Efforts should be made to enhance sulfide to sulfate conversion. The observed current and power density were comparable and even better than some of the results so far reported for similar systems. Three types of ion exchange membranes were tested. Comparison of their ion conductivity to literature data shows good performance. At higher initial sulfide concentrations polysulfides and thio-compounds were formed with considerably low current yield. Full article
(This article belongs to the Special Issue Electro-membrane Processes for Clean Water and Sustainable Energy)
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Open AccessFeature PaperArticle
Mass Transfer Phenomena during Electrodialysis of Multivalent Ions: Chemical Equilibria and Overlimiting Currents
Appl. Sci. 2018, 8(9), 1566; https://doi.org/10.3390/app8091566 - 06 Sep 2018
Cited by 8
Abstract
Electrodialysis is utilized for the deionization of saline streams, usually formed by strong electrolytes. Recently, interest in new applications involving the transport of weak electrolytes through ion-exchange membranes has increased. Clear examples of such applications are the recovery of valuable metal ions from [...] Read more.
Electrodialysis is utilized for the deionization of saline streams, usually formed by strong electrolytes. Recently, interest in new applications involving the transport of weak electrolytes through ion-exchange membranes has increased. Clear examples of such applications are the recovery of valuable metal ions from industrial effluents, such as electronic wastes or mining industries. Weak electrolytes give rise to a variety of ions with different valence, charge sign and transport properties. Moreover, development of concentration polarization under the application of an electric field promotes changes in the chemical equilibrium, thus making more complex understanding of mass transfer phenomena in such systems. This investigation presents a set of experiments conducted with salts of multivalent metals with the aim to provide better understanding on the involved mass transfer phenomena. Chronopotentiometric experiments and current-voltage characteristics confirm that shifts in chemical equilibria can take place simultaneous to the activation of overlimiting mass transfer mechanisms, that is, electroconvection and water dissociation. Electroconvection has been proven to affect the type of precipitates formed at the membrane surface thus suppressing the simultaneous dissociation of water. For some electrolytes, shifts in the chemical equilibria forced by an imposed electric field generate new charge carriers at specific current regimes, thus reducing the system resistance. Full article
(This article belongs to the Special Issue Electro-membrane Processes for Clean Water and Sustainable Energy)
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Open AccessArticle
High-Performance Thin-Film-Nanocomposite Cation Exchange Membranes Containing Hydrophobic Zeolitic Imidazolate Framework for Monovalent Selectivity
Appl. Sci. 2018, 8(5), 759; https://doi.org/10.3390/app8050759 - 10 May 2018
Cited by 3
Abstract
Zeolitic imidazolate framework-8 (ZIF-8) offers good hydrothermal, chemical, and thermal stabilities, and is therefore of interest in membrane synthesis. In this work, an interfacial polymerization (IP) method was applied by anchoring ZIF-8 to the skin layer of thin-film nanocomposite (TFN) membranes in order [...] Read more.
Zeolitic imidazolate framework-8 (ZIF-8) offers good hydrothermal, chemical, and thermal stabilities, and is therefore of interest in membrane synthesis. In this work, an interfacial polymerization (IP) method was applied by anchoring ZIF-8 to the skin layer of thin-film nanocomposite (TFN) membranes in order to obtain monovalent selectivity in electrodialysis. Organic trimesoyl chloride (TMC, 0.1 wt %) solutions and aqueous m-phenyl diamine (MPD, 2% w/v) solutions were used during the interfacial polymerization process. A range of polyamine (PA)/ZIF-8 based membranes was fabricated by varying the concentration of ZIF-8 in the organic solution. The properties of the primary and modified membrane were characterized by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), atomic force microscopy (AFM), water uptake, ion exchange capacity, and contact angle measurements. No significant changes of the surface structure of the PA/ZIF-8 based membranes were observed. Nevertheless, the presence of ZIF-8 under the PA layer plays a key role in the separation process. For single salt solutions that were applied in electrodialysis (ED), faster transport of Na+ and Mg2+ was obtained after introducing the ZIF-8 nanoparticles, however, the desalination efficiency remained constant. When the hybrid membranes were applied to electrodialysis for binary mixtures containing Na+ as well as Mg2+, it was demonstrated that the monovalent selectivity and Na+ flux were enhanced by a higher ZIF-8 loading. Full article
(This article belongs to the Special Issue Electro-membrane Processes for Clean Water and Sustainable Energy)
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Review

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Open AccessFeature PaperReview
Modelling of Ion Transport in Electromembrane Systems: Impacts of Membrane Bulk and Surface Heterogeneity
Appl. Sci. 2019, 9(1), 25; https://doi.org/10.3390/app9010025 - 21 Dec 2018
Cited by 14
Abstract
Artificial charged membranes, similar to the biological membranes, are self-assembled nanostructured materials constructed from macromolecules. The mutual interactions of parts of macromolecules leads to phase separation and appearance of microheterogeneities within the membrane bulk. On the other hand, these interactions also cause spontaneous [...] Read more.
Artificial charged membranes, similar to the biological membranes, are self-assembled nanostructured materials constructed from macromolecules. The mutual interactions of parts of macromolecules leads to phase separation and appearance of microheterogeneities within the membrane bulk. On the other hand, these interactions also cause spontaneous microheterogeneity on the membrane surface, to which macroheterogeneous structures can be added at the stage of membrane fabrication. Membrane bulk and surface heterogeneity affect essentially the properties and membrane performance in the applications in the field of separation (water desalination, salt concentration, food processing and other), energy production (fuel cells, reverse electrodialysis), chlorine-alkaline electrolysis, medicine and other. We review the models describing ion transport in ion-exchange membranes and electromembrane systems with an emphasis on the role of micro- and macroheterogeneities in and on the membranes. Irreversible thermodynamics approach, “solution-diffusion” and “pore-flow” models, the multiphase models built within the effective-medium approach are examined as the tools for describing ion transport in the membranes. 2D and 3D models involving or not convective transport in electrodialysis cells are presented and analysed. Some examples are given when specially designed surface heterogeneity on the membrane surface results in enhancement of ion transport in intensive current electrodialysis. Full article
(This article belongs to the Special Issue Electro-membrane Processes for Clean Water and Sustainable Energy)
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