Deformation of fluid interfaces under double-layer forces stabilizes bubble dispersions

A theoretical study of the colloidal interaction between two identical fluid drops (i.e., gas bubbles) forms the basis for the proposal of a possible mechanism by which salt inhibition of bubble coalescence occurs. Recent speculations attempting to describe this phenomenon were founded on the assumption that electrostatic double-layer forces are not relevant. In complete contradiction to this claim, the present results indicate that double-layer forces between the deformable bubble interfaces infer precisely the same behavior observed with salt addition: bubble coalescence is predicted to occur in water or in low electrolyte solutions, but is hindered once the electrolyte concentration is increased sufficiently. In other words, low-salt solutions favor large bubbles, high-salt solutions favor small bubbles. In this symmetric system, assuming fixed but physically appropriate conditions, a given bubble size determines a critical electrolyte concentration above which coalescence is not possible.