An improved model for CO2 solubility in aqueous electrolyte solution containing Na+, K+, Mg2 +, Ca2 +, Cl− and SO42 − under conditions of CO2 capture and sequestration

- A model is developed for CO2 solubility in aqueous NaCl-free electrolyte solutions.
- The model can predict CO2 solubility in aqueous electrolyte solutions with six ions.
- The model shows good accuracy under conditions of CO2 capture and sequestration.

Based on the Pitzer electrolyte theory for activity coefficient and an accurate equation of state for vapor fugacity, an improved activity-fugacity model is developed to calculate CO2 solubility in aqueous KCl, MgCl2, CaCl2, Na2SO4, K2SO4 and MgSO4 solutions, respectively. The valid range of temperature, pressure and ion strength is up to 450 K, 500 bar and 5 mol kg− 1. Average absolute deviation of CO2 solubility is about 5% compared to a large number of experimental data available, within or close to experimental uncertainties. By combining the interaction parameters of CO2 and ions developed here with those of CO2 and Na+ and Cl− from an earlier study of Mao et al. (2013), this model can be used to accurately predict CO2 solubility in aqueous mixed-salt solution containing Na+, K+, Mg2 +, Ca2 +, Cl− and SO2-4under conditions of CO2 capture and sequestration (generally less than 423 K and 500 bar). Computer code of the application program can be obtained from the corresponding author (maoshide@163.com).