We encounter surface active chemicals in many spheres of our lives. They are used in ore flotation, as emulsifiers in oil drilling, as adjuvants in pesticide formulations, in textile processing. Furthermore, they are personal care products and, most importantly, detergents. The latter products account for the largest portion of annual use of surfactants, about 8 million tons of synthetic surfactants and 9 million tons of salts of fatty acids (Granados, 1996). The word surfactant is an amalgam of




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. A chemical is surface active when it is enriched at the interface of the solution with adjacent phases. The general structure of surfactants consists of an apolar and a polar moiety, which commonly are referred to as the hydrophobic tail and the hydrophilic headgroup, respectively (Figure 17.1). According to the charge of the headgroup, surfactants can be subdivided into anionic, cationic, nonionic, and amphoteric surfactants, with all but the amphoteric headgroup used in detergents. The hydrophobic tails can be fluorocarbons, methylated silanes, or, most commonly, hydrocarbons. Hence, surfactants are a diverse group of chemicals. The diversity in the headgroups imparts different surfactants with different solute-solvent and solute-sorbent interactions. Table 17.1 explains abbreviations used for surfactants.