A step-wise ion hydration model of aqueous electrolyte solution: The 1:1 punch

Abstract

In prior work we showed that the current step-wise hydration framework shows promise for modeling the concentration-activity relationship in aqueous solutions of electrolytes, alcohols, and sugars, and accurately predicting the partitioning of the water between the bound (hydrated) pool and an unbound (free) pool. In the current work, we continue developing this framework by applying it to ions in electrolyte solutions. To a large extent, hydration of the ions along with either the mean spherical approximation or the Pitzer-Simon characterization of the long-range electrostatic interactions together yield a decently accurate model of the electrolytes without the need for ion-ion interaction parameters. The accuracy of the model degrades at high concentrations for highly hydrated ions when the number of water molecules per electrolyte in the free water pool becomes depleted.