Bubble dynamics model and its revelation of ultrasonic cavitation behavior in advanced oxidation processes: A review

The use of ultrasonic cavitation combined with advanced oxidation processes to improve the degradation efficiency of pollutants has received widespread attention. Thus far, most of these studies have relied on treatment effects or free radical test results to indirectly demonstrate the role of cavitation, with less analysis at the microscopic level. This study consolidates the mechanism of cavitation-enhanced pollutant degradation by focusing on the behavior of ultrasonic cavitation bubbles and the high-temperature and high-pressure phenomena formed by collapse in conjunction with a modified bubble dynamics model under different conditions. This study analyzes the effects of common variables, such as the ultrasonic effect, solution temperature, and initial radius of bubbles, on cavitation bubbles, cavitation intensity, and pollutant degradation effects during the advanced oxidation process. The simulation results of the numerical model corroborate the theories in the literature of advanced oxidation, which can explain, to a certain extent, the effect of cavitation on the degradation efficiency in the degradation experiments and elucidate the contribution of bubbles to the degradation effect in the cavitation process. This study is expected to provide a reference for the joint use of cavitation and advanced oxidation.