Prediction of gas solubilities in aqueous electrolyte systems using the predictive Soave-Redlich-Kwong model

The predictive Soave-Redlich-Kwong (PSRK) model widely used for the prediction of vapor-liquid equilibria and gas solubilities of nonelectrolyte systems was extended to electrolyte systems by the incorporation of the LIFAC model (electrolyte group contribution g(E) model) used to calculate the excess Gibbs energy of electrolyte systems in the gE mixing rule. Four new groups (charged or ionic groups Na+, NH4+, Ca2+, and Cl-) were added to the already existing 73 noncharged UNIFAC and PSRK main groups. The group interaction parameters between the new and already existing groups were fitted using gas solubility data for electrolyte solutions stored in the Dortmund Data Bank. Typical results for CO2, N-2, and CH4 solubilities predicted by the PSRK model are presented for various saltwater systems over a wide temperature and pressure range and different salt concentrations.