Influence of sonochemical reactor diameter and liquid height on methyl orange degradation under 200 kHz indirect sonication

The relatively high sonochemical activity in the frequency range 200–600 kHz, makes these high frequencies attractive for contaminant remediation. However, high frequency ultrasound also suffers from higher acoustic energy attenuation and inherent low intensity which limits the volume coverage and hence practical application. In this study, in order to clearly understand the relationship between the sonochemical activity and acoustic energy attenuation, calorimetric and degradation studies using methyl orange (MO) as a contaminant surrogate were investigated with indirect sonication at 200 kHz (transducer diameter: 65 mm) with various cylindrical glass reactors of different diameter (20, 48, 65, 95 and 117 mm) and liquid height (21, 58, 81 and 118 mm). It was clear that both reactor diameter and liquid height significantly influenced degradation efficiency. In addition to the inherent acoustic pressure distribution within the reactor due to the transducer acoustic pressure profile, the diameter of the reactor affected mainly attenuation of ultrasound in the radial direction, while attenuation in the axial direction was principally influenced by reactor height. A 95 mm diameter reactor with a ratio (reactor diameter/transducer diameter) of 1.45, exhibited the highest sonochemical efficiency and acoustic energy transfer efficiency across a range of liquid heights.