Thermodynamic modeling and molecular simulations of solubility of water in supercritical carbon dioxide at high pressures

We model the solubility of water in supercritical CO 2 at temperatures from 288.20 to 473.15 K and pressures between 40.5 and 500 bar using the Soave–Redlich–Kwong (SRK) cubic equation of state (EoS). For these temperature and pressure conditions, we show that fitting a single binary interaction parameter, k i j is sufficient to match the experimental data, precluding the need for a more complex EoS with many fitting parameters. The k i j obtained from two mixing rules, van der Waals 1 (vdW1) and co-volume dependent (CVD), varies linearly with temperature, making the model predictive. When a two-parameter mixing rule, vdW2 is used, the second fitting parameter is statistically insignificant. Therefore, we propose to use the CVD mixing rule for predicting water solubility in CO 2 under these conditions. Additionally, we perform direct interfacial molecular dynamics simulations to determine the mutual solubilities of CO 2 and water, with CO 2 and water modeled using the TraPPE and TIP4P2005 force fields, respectively. Water solubility in CO 2 from the simulations matches well with the experiments. However, CO 2 solubility in water is underpredicted. We modify the Lorentz-Berthelot mixing rule for the cross-interaction energy term of CO 2 and water, which improves the prediction of CO 2 solubility at high pressures. • Water solubility in CO2 modeled using cubic equation of state. • Single fitting parameter for the model sufficient to predict water solubility. • vdW and co-volume dependent mixing rules show predictive temperature dependence. • Molecular interactions between CO2 and water fine-tuned to match experiments. • Single fitting parameter needed to match simulation results to experiments.