
26 Foam Fractionation: Principles and Process Design
Before beginning a mechanistic description of the process of molecular
adsorption to a gas–liquid interface, it is necessary to dene one more
concentration: the subsurface concentration. This can be considered the
concentration of the adsorbing species in the liquid directly in contact with
the gas–liquid interface, and the difference in concentration between the
bulk and subsurface concentrations provides the driving force for molecu-
lar diffusion toward the interface. Surfactant adsorption to a gas–liquid
interface is shown schematically in Figure2.4.
The adsorption of a nonionic sur ...