Surfactant sorption on a single air bubble in an ultrasonic standing acoustic wave field

Ultrasound application presents a promising non-intrusive way to enhance and facilitate mass transfer in aqueous systems. This enhanced mass transfer can influence the sorption processes in multiphase flows. Previous studies investigating the impact of ultrasound on sorption, have reported an increase in either desorption due to the rise in liquid temperature or adsorption due to the additional convective mass transfer resulting from acoustic streaming. In this study, low intensity ultrasound with a frequency of 36kHz was deployed to evaluate the sorption process of Triton X-100 on the surface of a single bubble, placed along the standing acoustic wave using profile analysis tensiometry. Furthermore, microscopic particle image velocimetry was used to understand the role acoustic streaming might play during different stages of the sorption process. Contrary to expectations, the results showed no considerable change in surface tension and sorption dynamics after sonicating both fresh and surfactant-loaded bubbles. The results of this study suggest that the observations from previous studies may be attributed to the additional energy input of the acoustic wave into the system rather than the presence of an external acoustic field.