The Mechanisms of Collector Adsorption-Abstraction (Ionic and Non-Ionic Surfactants) on Heterogeneous Surfaces

The mechanisms of adsorption-abstraction of surfactants on heterogeneous surfaces can be described by taking into account: 1) the importance of lateral bonds that favour the formation of aggregates through a cooperative process on surfaces, 2) the intensity of normal adsorbate- adsorbent bonds that favour either the formation of two-dimensional aggregates in the monolayer range and at higher concentration the formation of a bilayer, if the interaction with the solid is strong or if the temperature is lower than the Krafft point, or the formation of micelles in the case of weak interaction with the solid surface (T > T_K), 3) the importance of energetic surface hetero- geneity 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 discussed.