Correlation between sonochemistry and sonoluminescence at various frequencies

Abstract

The development of generic large-scale sonochemical reactors requires a fundamental understanding of how various experimental parameters affect the acoustic cavitation efficiency. With a view to expand the experimental database and knowledge, the changes to acoustic cavitation bubble structures, caused by covering the air-solution interface with a lid at various frequencies and power levels, have been investigated. The accompanying effects have been quantified using sonochemiluminescence and sonoluminescence as probes. It has been observed that the chemically active cavitation bubble population is dominant in the ''open'' (without lid) configuration and the sonoluminescing bubble population is dominant in the ''closed'' (with lid) configuration. A possible reason for such differences is the existence of a well-defined standing wave pattern in the closed system.

A parametric review of sonochemistry: Control and augmentation of sonochemical activity in aqueous solutions

“…Zhou et al proposed that although sonoluminescence is increased with surface stabilisation, sonochemiluminescene activity is lowered due to reflective reinforcement of the standing wave component [156]. However this is dependent upon the frequency; in this groups previous work there was shown a decrease in sonochemical activity of up to 69% with surface stabilisation for 376, 995 and 1179 kHz at low and high powers [42].…”

“…Acoustic streaming localised around the bubble also increases and the rate of dissolution or growth of the bubble can be intensified up to twentyfold due to surface instabilities with bubbles becoming non-spherical in nature [61]. As discussed, quasi acoustic and acoustic streaming are more prevalent at higher frequencies and powers, therefore liquid flow associated with these mechanisms will increase with their increase [44,156,194,195]. Quasi acoustic streaming has been found to cause liquid flow in the 100's of kHz range with travelling waves becoming apparent at 448 kHz and dominating at higher frequencies ~726 kHz [163].…”

“…A reflective plate or surface stabiliser reinforces the standing wave component of the sound field resulting in an increase in pressure amplitude that can effect both sonoluminescence and sonochemiluminescence [42,156,196]. Zhou et al proposed that although sonoluminescence is increased with surface stabilisation, sonochemiluminescene activity is lowered due to reflective reinforcement of the standing wave component [156].…”

“…These waves are often referred to as a (quasi) acoustic streaming phenomenon with flow associated with the travelling part of the sound field [145,157]. The ratio between standing and travelling waves changes as a function of frequency with travelling waves dominating at high frequencies [44,156]. The frequency dependence of the nature of the bubbles, transient or repetitive transient, is difficult to define as it is reliant not only on the frequency but also the power and type of transducer (and transducer configuration) used [47].…”

“…A sound field consists of both standing and travelling wave components, with optimisation of sonochemical yields observed in the presence of travelling waves [42,44,156]. These waves are often referred to as a (quasi) acoustic streaming phenomenon with flow associated with the travelling part of the sound field [145,157].…”