Ion Exchange in Reverse Micelles

Pal, Sandeep and Vishal, G and Gandhi, KS and Ayappa, KG (2005) Ion Exchange in Reverse Micelles. In: Langmuir, 21 (2). pp. 767-778.

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Abstract

The distribution and dynamics of alkali cations inside Na-AOT reverse micelles have been investigated using Monte Carlo and molecular dynamics simulations. Water is modeled using the extended simple point charge (SPC/E) model. Simulations were carried out for alkali salts of $Li^+, Na^+, K^+, and Cs^+$ placed into the aqueous core of the reverse micelle, for situations corresponding to one and three molecules of added salt. In all cases, we observe that the larger $K^+ and Cs^+$ ions exchange with the $Na^+$ counterion; however, the smaller $Li^+$ ion prefers to remains solvated within the core of the reverse micelle. Our study reveals that the oil-water interface of the Na-AOT reverse micelle has the greatest selectivity toward $Cs^+$ followed by $K^+ and Li^+$. A model based on enthalpic contributions illustrates that the solvation energies of the different cations in water control the ion-exchange process. The hydration number of the first water shell for $Li^+$ situated in the aqueous core of the reverse micelle with radius R = 14.1 A was similar to that observed at infinite dilution in bulk water.

Item Type:	Journal Article
Publication:	Langmuir
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to American Chemical Society.
Department/Centre:	Division of Mechanical Sciences > Chemical Engineering
Date Deposited:	21 Feb 2005
Last Modified:	19 Jan 2012 09:59
URI:	http://eprints.iisc.ac.in/id/eprint/2799

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