THERMODYNAMIC MODEL OF IONIC AND NONIONIC SURFACTANT ADSORPTION ABSTRACTION ON HETEROGENEOUS SURFACES

The general concept of adsorption-abstraction of surfactants on heterogeneous surfaces may be described by taking into account (1) the lateral bonds which favor the formation of aggregates through a cooperative process on surfaces, (2) the intensity of normal adsorbate-adsorbent bonds that favor (a) when the interaction is strong the formation of two-dimensional aggregates at monolayer concentrations or bilayer formation at higher concentrations or when the temperature is less than the Krafft point and (b) for weak normal interactions the formation of micelles at the solid surface if the temperature is greater than the Krafft point, (3) the surface heterogeneity which controls the size of two-dimensional aggregates, and (4) the possible association of ionic surfactants with ions in solution that leads to bulk or surface precipitation (three-dimensional condensation on substrate). The importance of the selection of a reference phase and the specific methods to determine the nature of the adsorbed-abstracted phase are also discussed. The presented general approach is verified by discussion of the available experimental data.