Hofmeister Effects in Surface Tension of Aqueous Electrolyte Solution

Abstract

The surface tension of electrolyte solns. shows marked specific ion effects. We here show an important role for both ionic solvation energies and ionic dispersion potentials in detg. this ion sp. surface tension of salt solns. The ion self-free energy changes when an ion moves from bulk soln. into the interfacial region, with its decreasing water d. profile. We will show that the solvation energies of different ions correlate very well with the surface tension of salt solns. Inclusion of this distance-dependent self-free energy contribution brings qual. agreement with expts. and the right Hofmeister series. This is so not only for surface tension changes but also for measured surface potentials. The inclusion of ionic dispersion interaction potentials further improves the agreement with expts. We discuss how further progress in the theory of the surface tension of salts can be achieved.