The surface inhomogeneity of ion-exchange membranes by SEM and AFM data

Васильева, В. И.; Kranina, N. A.; Малыхин, М. Д.; Акберова, Э. М.; Zhiltsova, A. V.

doi:10.1134/s1027451013010321

Cited by 44 publications

(24 citation statements)

References 6 publications

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“…For example, the volume fraction of the conductive domains for the studied AEM was 0.45 and its surface fraction only 0.26. Similar results were obtained earlier by Volodina et al [15] and other authors [16]. The reason is that during the hot pressing of heterogeneous membranes, polyethylene, which is more fluid than polystyrene, moves from the membrane bulk on the surface.A membrane can include one or several layers.…”

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confidence: 90%

Modelling of Ion Transport in Electromembrane Systems: Impacts of Membrane Bulk and Surface Heterogeneity

et al. 2018

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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.Recently, Svoboda et al. [13] developed a specific scanning cell for the analysis of heterogeneous IEM structure by micro-computed tomography, which provides volume reconstruction of the studied material. The unique working principle of the cell allows one to scan membranes not only in their dry state but also in fully swollen state. The micro-computed tomography showed that there are profound changes in the structure of the IEM associated with their transition from the dry state into the swollen one. This study applied to the heterogeneous cation-exchange membrane (CEM) coming from Mega a.s., Czech Republic showed that swelling of the membrane is caused by the swelling of the ion-exchange resin. Its volume increased nearly three times after exposure to deionized water, while the overall membrane volume increased by 50%. If the membrane contained approximately 28%vol. of the resin in the dry state, this content increased to 52%vol. after swelling.Micro-computed tomography not only allows one to analyse volumetric composition of the membrane bulk but also to quantify the composition of the surface. By using two different methods, Vobecka et al. [14] evaluated the fraction of the conductive area (e.g., the ion-exchange resin) on the surface of an AEM and CEM in the swollen state. The obtained results showed that the volume fraction of the conductive domains does not correspond to the surface fraction of these domains and thus the volume composition is not reflected on their surface. For example, the volume fraction of the conductive domains for the st...

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confidence: 90%

Modelling of Ion Transport in Electromembrane Systems: Impacts of Membrane Bulk and Surface Heterogeneity

et al. 2018

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“…The SEM images of the surface of a membrane from the reversal electrodialyzer are presented for sides 1 and 2 facing the electrode and the neighboring compartment, respectively. The possibility for pressure control in the chamber with the sample under study made it possible to study membranes in the swollen state in the low-vacuum mode [51,52]. The information about the chemical composition of the surface or section of the membrane was obtained by mapping the elemental composition using an energy dispersive spectrometer.…”

Section: Methods For Investigation Of the Equilibrium Transportmentioning

confidence: 99%

“…By pore radius r is meant the effective radius of the round section modeled by the program which was equivalent in area to a real pore with an arbitrary shape. When calculating the average radius, a average weighted value was used to take into account different fractions of pores with different sizes [51].…”

Section: Methods For Investigation Of the Equilibrium Transportmentioning

confidence: 99%

Diagnostics of the Structural and Transport Properties of an Anion-Exchange Membrane MA-40 after Use in Electrodialysis of Mineralized Natural Waters

Васильева

Акберова

Kostylev

et al. 2019

Membr. Membr. Technol.

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Changes in the structural and transport characteristics of MA-40 anion-exchange membranes after operation in industrial electrodialysis apparatuses have been assessed. Causes for the deterioration of operational properties by the action of various factors in the process of demineralization and concentration of natural waters have been revealed. Samples of the anion-exchange membrane after long-term operation in the working stack of an electrodialysis concentrator, as well as samples taken out from the electrode compartment of the electrodialysis reversal apparatus, have been studied. The most significant change in the structure of the membrane taken out from the electrodialyzer concentrator is an increase in macroporosity, which is the main reason for the growth in the electrical conductivity and water content against the background of a loss of ion-exchange capacity and selectivity. The formation of poorly soluble carbonates and hydroxides both on the surface and in the bulk of a membrane from the electrode compartment of the reversal electrodialyzer leads to the blocking of the functional groups and transport channels, decrease in electrical conductivity, and complication of transport processes.

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“…Исследования структуры и процессов, происходящих в полимерных мембранах при их эксплуатации физическими методами, являются актуальной задачей и в настоящее время [1][2][3]. Методами рентгено-электронной (РЭМ) и атомно-силовой микроскопии (АСМ) проведены исследования влияния структуры и морфологии поверхности, однородных по толщине ионообменных мембран на процессы, происходящие в электродиализных методах [1][2]. В работе [3] изучены влияния электрической неоднородности поверхности гетерогенных ионообменных мембран на электрохимические характеристики.…”

Section: Introductionunclassified

Исследования Сорбционных Свойств Обратноосмоти- Ческой Эфирсульфонполиамидной Мембраны Мето- Дами Рентгенодифрактометрии И Дифференциальной Сканирующей Калориметрии

Golovin¹,

Лазарев²,

Яновская³

et al. 2018

sorpchrom

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Проведены исследования структурных свойств композиционной обратноосмотической эфирсульфонполиамидной мембраны ESPA1 методами рентгенодифрактометрии и дифференциальной сканирующей калориметрии (ДСК). Установлено, что в процессе водо-набухания эфирсульфонполиамидной мембраны наблюдается уменьшение рентгеновской степени кристалличности (СК). Дифференциальная сканирующая калориметрия ДСК надежно фиксирует эндотермический пик бимодальной формы при температурах 250 и 2540 С, отвечающих за плавление кристаллических фаз. Снижение степени кристалличности при сорбции воды, скорее всего, связано с перераспределением соотношения между количеством совершенных по структуре кристаллических фаз в кристаллитах полиамида 6.6, имеющих разные величины энтальпии плавления.

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The surface inhomogeneity of ion-exchange membranes by SEM and AFM data

Cited by 44 publications

References 6 publications

Modelling of Ion Transport in Electromembrane Systems: Impacts of Membrane Bulk and Surface Heterogeneity

Modelling of Ion Transport in Electromembrane Systems: Impacts of Membrane Bulk and Surface Heterogeneity

Diagnostics of the Structural and Transport Properties of an Anion-Exchange Membrane MA-40 after Use in Electrodialysis of Mineralized Natural Waters

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