Understanding the behavior of CO
2, especially its solubility, in electrolyte solutions and brines is of great importance to the design of a CO
2 geologic sequestration project. Since the properties of CO
2 bearing electrolyte solutions are strongly affected by the long-rang Coulomb interactions of ions, an accurate description of ion-ion interactions is important to the modeling of CO
2-H
2O-electrolyte system. In this work, CO
2 solubilities in single and mixed electrolyte solutions as well as synthetic geologic formation brines were correlated or predicted with statistical associating fluid theory (SAFT). [1, 2] In the proposed SAFT equation of state, the ion-ion interactions were represented by an improved mean spherical approximation in the primitive model using a parameter
K to correct the excess energies (â??KMSAâ? for short). [3] The universal correction factor
K was obtained by adjusting the internal and excess energies of mean spherical approximation to Monte Carlo simulation data. With the SAFT-KMSA model, we studied a range of aqueous electrolyte solutions including Na
+, K
+, Ca
2+, Mg
2+, Cl
-, Br
- and SO
42- from 298.15 K to 473.15 K. The cross interactions for CO
2-H
2O and CO
2-ion dispersion interactions were adjusted with binary interaction parameters
kij, which were fitted to CO
2 solubility data in water and single electrolyte solutions. Without additional parameters to fit, the proposed model was conveniently extended to predict CO
2 solubilities in mixed electrolyte solutions, including NaCl+KCl, KCl+CaCl
2, NaCl+KCl+CaCl
2, and in synthetic geologic formation brines. The proposed model shows good predictive power for CO
2 solubility in mixed electrolyte solutions and brines.
[1] Jiang, H.; Panagiotopoulos, A. Z.; Economou, I. G. Geochim. Cosmochim. Acta. 2016, 176, 185.
[2] Tan, S. P.; Ji, X.; Adidharma, H.; Radosz, M. J. Phys. Chem. B. 2006, 110, 16694.
[3] Jiang, H.; Adidharma, H. Mol. Simul. 2015, 41, 727.
