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Density functional theory of electrolyte solutions in slit-like nanopores II. Applications to forces and ion exchange
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.ORCID iD: 0000-0002-9629-2196
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
KTH, Superseded Departments, Chemical Engineering and Technology.ORCID iD: 0000-0001-8241-2225
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
2016 (English)In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 132, 561-570 p.Article in journal (Refereed) Published
Abstract [en]

An extended reference fluid density approach/weighted correlation approximation (RFD/WCA) of density functional theory (DFT) for size-asymmetric electrolytes presented in part I is applied to calculate the forces and the ion exchange for Ca- and Na-montmorillonite systems in equilibrium with salt solutions. Our modeling shows that the DFT calculations are in excellent agreement with Monte Carlo simulations and experimental results. The results indicate that the ion size plays an important role in force-distance relation. Due to the excluded volume effect, the osmotic pressure curve predicted by DFT is shifted towards larger separation distances with increasing the diameter of counterions. Additionally, the interaction can be switched from attraction to repulsion with increasing diameter of counterions from standard to hydrated ionic size. Furthermore, the quantitative characterization of the exchange of calcium for sodium at room temperature on Wyoming bentonite is investigated with the DFT modeling in aqueous solutions at pH 7.0. It is found that a significant variation of the selectivity coefficient could be observed with the surface charge density, ionic diameter and interlayer separations. This implies that ion selectivity in compacted bentonite differs from that in dilute smectite dispersions.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 132, 561-570 p.
Keyword [en]
Density functional theory, Montmorillonite, Ion exchange, Osmotic pressure, Swelling pressure
National Category
Theoretical Chemistry
URN: urn:nbn:se:kth:diva-196377DOI: 10.1016/j.clay.2016.08.006ISI: 000385600600065ScopusID: 2-s2.0-84991585055OAI: diva2:1050637

QC 20161129

Available from: 2016-11-29 Created: 2016-11-14 Last updated: 2016-11-29Bibliographically approved

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Yang, GuominNeretnieks, IvarsMoreno, LuisWold, Susanna
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