Estimating CO2 Solubility in Aqueous Na+–K+–Mg2+–Ca2+–Cl––SO42– Solutions with Electrolyte NRTL–PC-SAFT Model

A comprehensive thermodynamic model based on electrolyte nonrandom two-liquid (eNRTL) equation in conjunction with PC-SAFT equation-of-state has been developed for estimating CO2 solubility in aqueous solutions of NaCl, KCl, MgCl2, CaCl2, Na2SO4, K2SO4, MgSO4 and their mixtures. The eNRTL binary interaction parameters for CO2–electrolyte pairs are regressed using the experimental vapor–liquid equilibrium data for the CO2 + H2O + salt ternary systems in the temperature range of 273.15 to 433.15 K, and pressure up to 71 MPa. The model gives an accurate representation of the phase behavior including the salting-out effect of different electrolytes for CO2 solubility covering temperatures up to 473.15 K, pressures up to 120 MPa, and salt concentrations up to saturation. With the CO2–H2O interaction parameters set to zero, and the H2O–electrolyte, CO2–electrolyte and electrolyte–electrolyte pair interaction parameters identified, the model is capable of accurately estimating CO2 solubility in aqueous brine solutions without regressing any additional interaction parameters.