Thermodynamic and Dynamic Interfacial Properties of Binary Carbon Dioxide−Water Systems

We have measured the interfacial tension (γ) between H 2 O and CO 2 with a drop tensiometer that permitted us to regulate the drop area and to perform elasticity measurements. We observed that γ decreased with time and with the CO 2 pressure. We first analyzed the adsorption of CO 2 onto surface water by plotting the initial interfacial tension (γ 0 ) versus CO 2 fugacity and applied Gibbs and then Langmuir-Freundlich equations. We have calculated the interfacial area occupied by CO 2 molecules onto H 2 O as well as the equilibrium constant and the thermodynamics parameters of adsorption. This permitted us to understand that the CO 2 was adsorbed onto the surface water by formation of a one-to-one H-type complex with H 2 O. Second, we attributed the kinetics phenomena to the formation of interfacial clusters between water and CO 2, which gave interfacial quasi-crystalline structure as shown by compression of the drop area at the end of the adsorption kinetics. We studied this interfacial organization by measuring the apparent elasticity versus time and CO 2 pressure. This measurement allowed us to propose an interfacial organization based on the formation of small blocks, which grow to fill the interface, as already observed by Teng and al. 1 Then we determined the filling of the clusters cavities by analyzing the difference between γ 0 and γ eq (Δγ) by means of the Hill equation. This permitted us to determine that this filling depended on temperature and was cooperative.