salt ions, molecular-dynamics, miscible system


Molecular-dynamics simulations were performed to model the effect of added salt ions on the liquid-liquid interface in a partially miscible system. Simulations of the interface between saturated phases of a model 1-hexanol + water system show a bilayer structure of 1-hexanol molecules at the interface with OH heads of the first layer directed into the water phase and the opposite orientation for the second layer. The alignment of the polar OH groups at the interface stabilizes a charge separation of sodium and chloride ions when salt is introduced into the aqueous phase, producing an electrical double layer. Chloride ions aggregate nearer the interface and sodium ions move toward the bulk water phase, consistent with the explanation that the OH alignment presents a region of partial positive charges to which the hydrated chloride atoms are attracted. Ions near the interface were found to be less solvated than those in the bulk phase. An electric field was also applied to drive ions through the interface. Ions crossing the interface tended to shed water molecules as they entered the hexanol bilayer, leaving a trail of water molecules. Stabilization and facilitated transport of the ion by interactions with the second layer of hexanol molecules appeared to be an important step in the mechanism of sodium ion transport.

Original Publication Citation

Wardle, Kent E., Eric Carlson, Douglas Henderson, and Richard L. Rowley. "Molecular-dynamics simulation of the effect of ions on a liquid-liquid interface for a partially miscible mixture." The Journal of Chemical Physics 12 (24): 7681-7688

Document Type

Peer-Reviewed Article

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Ira A. Fulton College of Engineering and Technology


Chemical Engineering