Diferencias entre los valores de la tensión interfacial dinámica de gotas de agua en CO2 y burbujas de CO2 en agua

The dynamic interfacial tension of water in a gaseous environment of CO2 was determined at 20, 30, 40 and 50 o C and pressures of 0, 1, 2, 3, 4, and 5 MPa. It was also calculated the interfacial tension of CO2 bubbles in water at 30, 40 and 50 o C and pressures of 2 and 3 MPa. For the determination of these interfacial tensions the pendant drop method was used (water as dispersed phase and carbon dioxide as a continuous phase) or its variation of the emergent bubble method (carbon dioxide as dispersed phase and water as a continuous phase), keeping both pressure and temperature constant and varying only the volume of the dispersed phase. The values obtained from the equilibrium surface tension of the drop ranged from 33.1 and 68.5 mN/m, while for the case of the bubble these values ranged between 26.6 and 41.7 mN/m. For both cases, the bubble and the drop, the interfacial tension values showed a decreasing tendency over time for each condition of temperature and pressure selected. In the case of bubble, the value of interfacial tension decreases as the temperature increases, but in the case of the water drop at high pressures, interfacial tension increases as temperature increases. The interfacial tension values obtained were different in cases where continuous and dispersed phases changed: 93 When the CO2 was the dispersed phase (bubbles of CO2) the value of interfacial tension was smaller than when the gas was the continuous phase (drops of water) at the same temperature and pressure. These differences are due to this system behaves as a non-ideal one. When CO2 is dissolved in the water phase causes a swelling of the mixture (a notorious change in volume) and the interfacial forces have a different behaviour depending on which are the dispersed phase and the direction of mass flow between the two phases.