Molecular simulation study of speciation in supercritical aqueous NaCl solutions

Molecular simulation of dilute NaCl aqueous solutions are performed to study the thermodynamics and kinetics of Na+/Cl- speciation at high temperature. Using the SPC, the Pettitt-Rossky, and the Fumi-Tosi models for the water-water, the ion-water, and the ion-ion interactions respectively, we determine the enthalpy and volume of association at the reduced conditions of T-r = 1.05 and p(r) = 1.5, and compare with the corresponding predictions of a recent correlation based on conductance measurements at high temperature. The forward and backward (transition state theory) kinetic rate constants for the interconversion between contact and solvent-shared ion pair configurations along the reduced isotherm of T-r = 1.05, and the transmission coefficient at T-r = 1.05 and p(r) = 1.0 are assessed by simulation and compared with the corresponding quantities at ambient conditions.