Bubbling in carbon dioxide aqueous solutions containing fine air bubbles

Abstract

Bubbling in carbon dioxide (CO2) aqueous solutions initiated by pre-existing fine air bubbles, rather than CO2 gas cavities, has been theoretically investigated. As the bubbling of CO2 gas progressed more rapidly than the dissolution of air in the solutions, the CO2 bubbles were assumed to be at thermodynamic partial equilibrium, in which the equilibria with respect to the pressure (Young–Laplace equation) and chemical potential of CO2 (Henry’s law) were attained, but the equilibrium with respect to the chemical potential of air was not attained between the bubbles and the aqueous solution. It has been shown that the radii of CO2 bubbles in unsaturated CO2 solutions are in stable equilibrium, whereas they have two equilibrium states in weakly supersaturated CO2 solutions: a stable state with small bubble radii and an unstable state with large bubble radii. In highly supersaturated CO2 solutions, CO2 bubbles cannot satisfy the equilibrium of the chemical potential of CO2, and they assume a growing state that satisfies only the pressure equilibrium.