Thermodynamics and kinetics of ion speciation in supercritical aqueous solutions: a molecular-based study

Molecular simulation of infinitely dilute NaCl aqueous solutions are performed to study the Na+/Cl− ion pairing in a polarizable and a non-polarizable solvent at supercritical conditions. The simple point charge (SPC), the Pettitt–Rossky and the Fumi–Tosi models for the water–water, the ion–water, and the ion–ion interactions are used in the determination of the degree of dissociation, its temperature and density dependence, and the kinetics of the interconversion between ion-pair configurations in a non-polarizable medium. To assess the effect of the solvent polarizability on the stability of the ion-pair configurations we replace the SPC by the polarizable point charge (PPC) water model and determine the anion–cation potential of mean force at Tr=1.20 at ρr=1.5.