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Experimental observation of phenomena developing on ion-exchange systems during current-voltage curve measurement

Citace:
BELLOŇ, T., POLEZHAEV, P., VOBECKÁ, L., SVOBODA, M., SLOUKA, Z. Experimental observation of phenomena developing on ion-exchange systems during current-voltage curve measurement. JOURNAL OF MEMBRANE SCIENCE, 2019, roč. 572, č. JAN 15 2019, s. 607-618. ISSN: 0376-7388
Druh: ČLÁNEK
Jazyk publikace: eng
Anglický název: Experimental observation of phenomena developing on ion-exchange systems during current-voltage curve measurement
Rok vydání: 2019
Autoři: Tomáš Belloň , Petr Polezhaev , Lucie Vobecká , Ing. Miloš Svoboda Ph.D. , Doc. Ing. Zdeněk Slouka Ph.D.
Abstrakt CZ: Iontově výměnné systémy, představované například iontově výměnnými membránami nebo iontově výměnnými částicemi, vykazují nelineární proudo-napěťové charakteristiky s třemi rozlišitelnými oblastmi. Tyto tři oblasti se nazývají podlimitní, limitní a nadlimitní. Každá z těchto oblastí reprezentuje jevy zodpovědné za transport iontů v daném proudovém režimu. V této publikaci sledujeme rozhraní mezi kationtově výměnným systémem a elektrolytem na iontově vyčerpané straně membrány v průběhu měření proudo-napěťové charakteristiky, pomocí fluorescence a optického pozorování.
Abstrakt EN: Ion-exchange systems represented, for example, by ion-exchange membranes or ion-exchange resin particles exhibit nonlinear current-voltage curves on which one finds three distinct regions. These regions are referred to as underlimiting, limiting and overlimiting ones. Each of these regions reflects proceeding phenomena responsible for the ion transport. It is known that all important transport processes take place on the depletion side of the ion-exchange systems. Here, we capture the situation at the interface between a cation-exchange system and an electrolyte on the depletion side as it develops during the measurement of a current-voltage curve by using fluorescent and optical observations. Our observations allow to describe qualitatively transport phenomena occurring in ion-exchange systems and to assign their onset to the particular points on the currentvoltage curve. We show that current-voltage curves for the studied systems, namely a single cation-exchange particle and a heterogeneous cation-exchange membrane, have a shape typical for ion-exchange systems, i.e. we can clearly recognize underlimiting, limiting and overlimiting region. Interestingly, the overlimiting region of both systems can be divided into two parts based on the slope of the currentvoltage curve in this region. We show that there is a qualitative and quantitative change in the developed electroconvection as the major mechanism governing the overlimiting current when the system transitions from the first part of the overlimiting region to the second one. This transition of electroconvection causes its mixing effect to change from local to global.
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