Adsorption of Surfactants

Abstract

One of the most striking physicochemical characteristics of surfactants is their ability to reduce interfacial tension at low concentration. Surface-active agents are defined by this property. Unlike surfactants, inorganic salts increase the interfacial tension. This difference between surfactants and inorganic salts depends on the way the solute is adsorbed at an interface: surfactants show positive adsorption, whereas inorganic salts show negative adsorption. The extent of positive adsorption of a surfactant depends entirely on its chemical structure and on the solvent. This chapter develops the physical meaning of interfacial tension and the relation between interfacial tension change and surfactant concentration in order to elucidate the nature of surface activity.^1–4