Solubility of CO2 in salty water: adsorption, interfacial tension and salting out effect

Abstract

In this work, we performed Molecular Dynamics simulations to investigate the solubility of CO 2 in both pure water and NaCl aqueous solutions, employing various force fields for water and NaCl. We first focussed on the solubility of CO 2 in TIP4P/2005 and TIP4P/Ice water models. We found that it was necessary to apply positive deviations to the energetic Lorentz-Berthelot combining rules for the cross interactions of water and CO 2 in both models to accurately replicate the experimental solubility of the gas. Then we found a negative adsorption of ions at the NaCl solution– CO 2 interface. We also observed an increase of the interfacial tensions of the system when adding salt which is related with the observed negative adsorption of the ions at the interface. Furthermore, we found that unit charge models tend to highly overestimate the change in the interfacial tension compared to scaled charge models. Finally, we also explored the salting out effect of CO 2 using different force fields for NaCl. Our findings indicate that unit charge force fields significantly overestimate the salting out effect of CO 2 while the scaled charge model Madrid-2019 accurately reproduces the experimental salting out effect of CO 2 in NaCl solutions.