Phase equilibrium and interfacial properties of water + CO2 mixtures

Carbon dioxide (CO2) has a high industrial relevance. From all these, the mixtures of CO2 with water show great importance due to their potential in carbon capture and storage systems. It is therefore important to be able to model both phase equilibrium and interfacial properties of this system in a proper manner. In order to do this, the density gradient theory can be combined with a suitable equation of state. This leads to calculations of both phase equilibrium and interfacial properties of the mixture. In this particular case, the polar perturbed chain statistical associating fluid theory (PCP-SAFT) was used for this work. The proposed framework allows the inclusion of some relevant properties of the compounds, such as association of water and the orientation effects of molecules due to the quadrupole moment of CO2. Phase and interfacial properties (e.g. interfacial tension) are then calculated and compared with data from the literature, in vapor–liquid (VLE) and liquid–liquid (LLE) equilibrium systems. The calculations show good agreement with the experimental data from other authors.

► The model can be used to calculate vapor–liquid and liquid–liquid equilibria.
► The binary interaction parameter shows a linear temperature dependency.
► An additional binary parameter is required for modeling of the interfacial tension.
► CO2 will be enriched on the interface.