Modeling the CO₂ Solubility in Aqueous Electrolyte Solutions Using ePC-SAFT

Carbon dioxide (CO 2 ) solubility in aqueous electrolyte solutions is of special interest for carbon capture and storage and for biochemical processes, particularly at moderate to high temperatures, pressures, and electrolyte concentrations. Unfortunately, experimental determination at such conditions is rather laborious. Therefore, the ion-based model ePC-SAFT was used in this work to model the CO 2 solubility in such systems over a broad range of conditions. The mixtures under investigation were the basis system CO 2 + water and higher systems containing either NaCl, KCl, MgCl 2, CaCl 2, NaNO 3, KNO 3, Mg(NO 3 ) 2, or NaHCO 3 . In the pH range considered in this work (pH < 7), CO 2 dissociation reactions were found to be negligible; thus, only physical interactions were considered. Assuming induced association for CO 2, binary interaction parameters between CO 2 –water and CO 2 –ion species were determined by fitting to literature data. For this purpose, different literature data sets were compared, and only the most reliable data were used to estimate the binary parameters. ePC-SAFT was found to be able to accurately model the CO 2 solubility in water as well as in aqueous systems containing electrolytes over a broad range of temperatures, pressures, and salt concentrations.