In situ measurements on surfactant–mineral interactions by polarographic adsorption kinetics

Abstract

Adsorption of surfactants at the mercury/electrolyte interface causes changes in electrode capacity. This phenomenon can be used for surfactant analysis in low and ultra-low concentration ranges. Tensammetry is carried out by alternating current or potential pulse techniques. Time-dependent concentration changes can be determined by adsorption kinetics at the mercury/electrolyte interface. As the interaction of surfactants with the mercury/electrolyte interface strongly depends on the potential of the electrode, repeated potential jumps can be used to generate adsorption–desorption cycles. This permits rapid determination of constant or time-dependent concentration. The adsorption kinetics of cationic and non-ionic surfactants on clay minerals were determined by Kalousek polarography. These two types of surfactant exhibit different behaviour. Many other adsorption phenomena might also be investigated by using the method described here.