Abstract The adsorption kinetics of anionic surfactant Aerosol-OT (AOT) in 10 mM NaCl solution was investigated by measuring and simulating the dynamic and equilibrium surface tension (ST) data. The relaxation of… Click to show full abstract
Abstract The adsorption kinetics of anionic surfactant Aerosol-OT (AOT) in 10 mM NaCl solution was investigated by measuring and simulating the dynamic and equilibrium surface tension (ST) data. The relaxation of ST for AOT molecules adsorbing onto a freshly created bubble surface was measured using a video-enhanced pendant bubble tensiometer at eighteen AOT concentrations. The partially ionized Langmuir model was applied to best-fit the dynamic/equilibrium ST data. The subsequent findings revealed that the model with a dissociation degree α of 0.1 − 0.2 described the dynamic and equilibrium ST data very well. This implied that AOT behaved as a partially ionized surfactant in 10 mM NaCl solution. The adsorption for AOT onto a clean air–water interface was found to be either (i) diffusion-controlled with a diffusivity value that varied [between 2.5 and 4.6 (10−6 cm2/s)] depending on the bulk concentration or (ii) mixed-controlled with an adsorption rate constant of 2.4 ± 0.8 (107 cm3/mol.s).
               
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