Dynamic surface tension of mixed oxyethylated surfactant solutions

The adsorption kinetics of mixed non-ionic surfactants can be described by a diffusion controlled adsorption when the correct model is used, i.e. when for each adsorbing species the corresponding thermodynamic model for the adsorption equilibrium is applied. For non-ionic surfactants, such as oxyethylated alcohols C12EO5 and C14EO8 and Tritons X-n, the reorientation model is the appropriate model. The dynamic surface tensions measured by bubble profile tensiometry are described very well by an efficient diffusion coefficient decreasing with the total surfactant bulk concentration. The physical reason for the change in Deff is the effect of convection in the system becoming more pronounced with the increasing in adsorption time. Equimolar mixtures of Triton X-45 and X-165 mimic the adsorption behaviour of Triton X-100.