ADSORPTION-KINETICS OF C10E8 AT THE AIR-WATER-INTERFACE

The adsorption of C10E8 onto a clean air-water interface and the desor ption out of an overcrowded interface due to a sudden shrinkage of a p endant bubble in a quiescent surfactant solution are studied. Video-en hanced pendant bubble tensiometry is employed for the measurement of t he relaxation in surface tension. Relaxation profiles of surface tensi on for C10E8 molecules absorbing onto a freshly created air-water inte rface and desorbing out of a compressed air-water interface are obtain ed. The adsorption of C10E8 is found to be anticooperative from the eq uilibrium surface tension data compared with the prediction of the Fru mkin model. The controlling mechanism of the adsorption process change s as a function of bulk concentration; it shifts from diffusion contro l at dilute concentration to mixed diffusive-kinetic control at more e levated bulk concentration. It is also confirmed that the desorption o f C10E8 out Of a compressed interface is a mixed diffusive-kinetic con trolled process. Comparison is made for the entire relaxation period o f the tension data and the model predictions. Values of the diffusivit y and the adsorption/desorption rate constants of C10E8 are calculated from these dynamic surface tension profiles. The values of the kineti c rate constants obtained from the desorption experiment are the same as that obtained from the clean adsorption experiment.