Predicting CO₂-H₂O Interfacial Tension Using COSMO-RS.

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Geochemistry

Background:

• Interfacial tension (IFT) between fluids and solids is critical for industrial and natural processes, including geological CO2 storage.
• Existing experimental data on CO2-water IFT under supercritical conditions are limited and sometimes conflicting.
• Molecular modeling offers a complementary approach to experimental IFT determination, especially under challenging conditions.

Purpose of the Study:

• To predict the interfacial tension (IFT) of the carbon dioxide-water system using computational methods.
• To investigate the influence of pressure, temperature, and salinity on CO2-water IFT.
• To provide a reliable and efficient computational tool for IFT prediction in CO2 storage applications.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• The COSMO-RS implicit solvent model was integrated with DFT.
• IFT was predicted across a range of pressures (0-50 MPa), temperatures (273-383 K), and NaCl salinities (0-5 M).

Main Results:

• The predicted CO2-water IFT values show good agreement with existing experimental data and molecular dynamics simulations.
• The model successfully captures the dependence of IFT on pressure, temperature, and salinity.
• The computational approach demonstrates accuracy within the uncertainty margins of experimental and simulation data.

Conclusions:

• The combination of DFT and COSMO-RS provides a fast and accurate method for predicting CO2-water IFT.
• This model serves as a valuable alternative to time-consuming experimental measurements and complex simulations.
• The findings support the application of this method for understanding CO2 behavior in geological storage.