An oscillating bubble technique to determine surfactant mass transfer kinetics

Abstract

In this paper, an oscillating bubble method is introduced as a spherical analog of the longitudinal wave method. In the longitudinal wave method, amplitude ratios and phase angles between surface tension variations at two locations on the interface are related to the surfactant mass transfer kinetics. In the analogous oscillating bubble method, by forcing small-amplitude radial perturbations about an equilibrium base state, and measuring the phase angle between the bubble radius and the gas phase pressure, the surfactant diffusion and sorption kinetics can be determined. In this communication, data are presented for n-decanol at the aqueous-gas interface. The phase angle is measured as a function of bulk concentration and forcing frequency. By minimizing the error between theoretical and experimental phase angle profiles, the diffusivity and desorption coefficients of n-decanol are obtained.