Prediction of Equilibrium Interfacial Tension between CO2 and Water Based on Mutual Solubility

In this paper, an interfacial tension (IFT) correlation (i.e., Model #2) between CO2 and water is generalized as a function of their mutual solubility and the reduced pressure of CO2 in a temperature range of 278.2-469.2 K and a pressure range of 0.10-69.10 MPa. Two sets of correlation coefficients are respectively regressed for pressures lower and higher than the critical pressure of CO2 (i.e., 7.38 MPa). Such a newly developed correlation is calculated to yield an absolute average relative deviation (AARD) of 4.5%, a maximum absolute relative deviation (MARD) of 32.3%, and a maximum absolute deviation (MAD) of 1.65 mN/m, respectively. The newly developed model is found to greatly outperform the four existing correlations as a function of temperature, pressure, or CO2 solubility in water. A higher CO2 solubility in water (i.e., x(CO2)) leads to a lower IFT for all pressures, while a higher water solubility in the CO2 phase (i.e., y(w)) results in a lower IFT mainly at lower pressures. Both pressure and temperature exert effects on IFT mainly through regulating the x(CO2) and y(w). Since the addition of inorganic salt can decrease the CO2 solubility in water, a higher salinity leads to a higher IFT. The developed model in this work can be a good estimate for the IFT between CO2 and brine if salinity is not too high.