How Ionic Polarization Affects Stern Potential: An Insight into Hofmeister Effects

Soil Sci. Soc. Am. J.

Xinmin Liu

The Stern potential of nano-colloidal particles in aqueous solution has significant effects on chemical, physical, and biological processes. In this study, a modified theory for the Stern potential considering ionic polarization was established, and then the contributions of the ionic polarization to the Stern potential were quantified. The ionic polarization was strongly enhanced by the strong electric field from the surface charges of nano-colloidal particles. The polarization energy (depending on the structure of the electron cloud) could even be comparable with the Coulomb energy; the ratio of polarization to Coulomb effect is 11.0% for Na+, 69.9% for K+, 34.0% for Mg2+ and 103.4% for Ca2+. The ionic polarization at solid–liquid interfaces dramatically decreased the Stern potential. An important origin of Hofmeister effects was found and successfully verified by experments.