Acoustic Emission Spectra from 515 kHz Cavitation in Aqueous Solutions Containing Surface-Active Solutes

Abstract

The effect of adding surface-active solutes to water being insonated at 515 kHz has been investigated by monitoring the acoustic emission from the solutions. At low concentrations (<3 mM), sodium dodecyl sulfate causes marked changes to the acoustic emission spectrum which can be interpreted in terms of preventing bubble coalescence and declustering of bubbles within a cavitating bubble cloud. By conducting experiments in the presence of background electrolytes and also using non-ionic surfactants, the importance of electrostatic effects has been revealed. The results provide further mechanistic evidence for the interpretation of the effect of surface-active solutes on acoustic cavitation and hence on the mechanism of sonochemistry. The work will be valuable to many researchers in allowing them to optimize reaction and process conditions in sonochemical systems.

Influence of Acoustic Cavitation on the Controlled Ultrasonic Dispersion of Carbon Nanotubes

“…When the ionic surfactant concentration is increased to 300% cmc, the concomitant increase in solution ionic strength leads to charge shielding effects, reducing the repulsion between surfactant molecules and resulting in the formation of denser bubble clouds. A similar hypothesis was previously proposed to rationalize acoustic measurements in an anionic surfactant 21 . A contributing factor to the decrease in inertial cavitation with time in pure water and at 30% cmc may be a preference for stable cavitation as the bulk solution temperature increases during ultrasonication 9,11 .…”

“…Inertial cavitation is clearly favored at the higher surfactant concentration, which may be ascribed to more facile formation of bubbles due to the reduced surface tension. Furthermore it is believed that at 30% cmc the distance between bubbles is relatively large due to electrostatic repulsion 21 . When the ionic surfactant concentration is increased to 300% cmc, the concomitant increase in solution ionic strength leads to charge shielding effects, reducing the repulsion between surfactant molecules and resulting in the formation of denser bubble clouds.…”

Quantitative evaluation of hemolysis in bovine red blood cells caused by acoustic cavitation under pulsed ultrasound

“…An unstable transient cavitation bubble with a short lifetime generates a shock wave by collapsing [11]. As the non-exposure time is reduced, transient cavitation bubbles can grow sufficiently to generate broadband shock waves by collapsing [9,15]. On the other hand, stable cavitation bubbles under continuous excitation will maintain a periodic oscillation without collapsing and this behavior will suppress hemolysis.…”

Sonochemical degradation of perfluorinated chemicals in aqueous film-forming foams

“…In the case of 3M AFFF, the effect is not as significant, since the difference in rate of release of F -between the greatest and the least concentration of TOF was less (~ 28%). Rates of degradation observed at greater concentrations of FC can be explained by greater availability of adsorbed FC molecules at the bubble-liquid interface and an increase in electrostatic repulsion between bubbles preventing them from coalescing, which enhances the number density of cavitating bubbles [35].…”