Tomer Markovich, David Andelman, Rudi Podgornik
We study the surface tension of electrolyte solutions at the air/water and oil/water interfaces. Employing field-theoretical methods, and considering short-range interactions of anions with the surface, we expand the Helmholtz free energy to first-order in a loop expansion and calculate self-consistently the excess surface tension. We obtain analytically the surface-tension dependence on the ionic strength, ionic size and ion-surface interaction, as a direct generalization of the well-known Onsager-Samaras theory. Our theory fits well a wide range of concentrations for different salts using two fit parameters, reproducing the reverse Hofmeister series for anions at the air/water and oil/water interfaces.
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http://arxiv.org/abs/1305.3142
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