ABSTRACT
This chapter deals with the adsorption of surfactants at the air/liquid and liquid/liquid interfaces, since the same equations can be applied for treating adsorption of surfactants at both these interfaces. It also deals with the adsorption of surfactants and polymers at the solid/liquid interface. This is key to understanding how surfactants and polymers function as stabilizers and flocculants. There are generally two approaches for treating surfactant adsorption at the air/liquid (A/L) and liquid/liquid (L/L) interface. The first approach, adopted by Gibbs, treats adsorption as an equilibrium phenomenon whereby the second law of thermodynamics may be applied using surface quantities. The second approach, referred to as the equation of state approach, treats the surfactant film as a two-dimensional layer with a surface pressure p that may be related to the surface excess G. In principle, surfactant adsorption may be described in terms of the surfactant/surface, surfactant/solvent, and surface/solvent interaction parameters.
