Adsorption kinetics of sodium dodecyl sulfate on perturbed air-water interfaces

A pendant bubble tensiometer was used to measure the relaxation of the surface tensions of aqueous sodium dodecyl sulfate (SDS) solutions for four different perturbed air-water interfaces under surface rinsing, sudden surface compression, continuous surface expansion and compression. The complete set of surface tension (ST) relaxations was monitored to study the adsorption kinetics of SDS. The ST increased in the surface rinsing experiment, and this increase indicated that the SDS that was adsorbed at the air-water interface desorbed from the interface. The ST relaxed continuously after sudden surface compression, and this continuous ST relaxation indicated that the desorption rate of SDS molecules was faster than the surface compression rate. The ST remained a constant value during the continuous surface expansion and surface compression, and this constant ST data indicated that the adsorption and desorption rates were faster than the surface perturbation rate in this study.