A new and consistent model for dynamic adsorption of CTAB at air/water interface

Abstract

A new and simple equation, with only one parameter, was developed to model the equilibrium surface tension of the air/cetyltrimethylammonium bromide (CTAB) solution interface. The new equilibrium model provides a single best-fitted prediction, instead of several solutions obtained by the conventional Szyszkowski equation. Subsequently, the equation was used to develop a new dynamic model, which does not require a Gibbs adsorption isotherm. The diffusion coefficient of CATB was also independently measured by 1H NMR and used as an input for the new dynamic model. The new model was applied to dynamic surface tension data at 2 different concentrations simultaneously to obtain best-fitted values for adsorption parameters. The modeling result was consistent with all experimental results. In contrast to previous studies in the literature, the new model predicts dynamic surface tension of CTAB successfully by a diffusion-controlled mechanism and a kinetics step was not required. The study provides a new and effective dynamic model for dynamic surface tension at the air/water interface.