Adsorption dynamics of surfactants at the air/water interface: a critical review of mathematical models, data, and mechanisms

This review covers equilibrium and dynamic aspects of surface tension and adsorption, primarily of single nonmicellar or premicellar surfactants at the air/water interface. Equilibrium tension data have been related to the Langmuir adsorption equilibrium isotherm and the Gibbs isotherm. A set of Langmuir isotherm parameters has been compiled. Dynamic adsorption models with the diffusion-controlled and mixed-kinetic mechanisms are discussed in some detail and applied to several sets of data. Apparent diffusion coefficients, inferred from dynamic tension data, and kinetic adsorption parameters, derived from application of the models to the data, are presented and critically evaluated. The adsorption of most of the surfactants examined is slower than predicted by diffusion-controlled models. Exceptions are mostly non-ionic surfactants and certain alcohols.