Adsorption kinetics at air/solution interface studied by maximum bubble pressure method

A general dynamic surface adsorption equation Γ(t) for maximum bubble pressure method was derived by solving Fick’s diffusion equation for the bubbles under different initial and boundary conditions. Different from the planar surface adsorption(Ward-Tordai equation), the derived dynamic surface adsorption Γ(t) for the short time consists of two terms, one of them reflects the geometric effect caused by the spherical bubble surface. This kind of effect was discussed. The equilibrium surface tension γeq and the dynamic surface tension γ(t) of aqueous C10E8 (CH3(CH2)9(OCH2CH2)8OH) solution at temperature 25 °C were measured by means of Wilhelmy plate method and maximal bubble pressure method respectively. In the region of t→0 (short time limits) a good agreement of experimental results with the theory was reached and the adsorption was controlled by diffusion. However, for the long time limits, a mixed diffusion-kinetics controlled process was proved.