On the Physical Insight into the Barotropic Effect in the Interfacial Behavior for the H2O + CO2 Mixture

Practice-based experimental reviews have unambiguously shown that the experimental efforts for determining and understanding in detail the dependence of the interfacial tension (IFT) of the H2O + CO2 system at high pressure are limited by the well-known mass density inversion. This phenomenon entails that the CO2-rich phase becomes denser than the H2O-rich phase. Additionally, there are often inconsistencies among the existing literature data, thereby making it challenging to propose predictive models to complement densities and IFT in the regions where experimental measurements are difficult or even impossible to access. In this contribution, the mass density inversion effect on IFT is corroborated by coarse-grained molecular dynamics simulations employing the SAFT-gamma-Mie force field, combined with the density gradient theory. The mass density inversion due to gas enrichment is revealed to be an important switch that controls the slope in the IFT curve and also the conformation of minimum and maximum accumulation on the interfacial population of species, which interestingly implies simultaneous desorption and adsorption along the interfacial zone.