Simple design strategy for bath-type high-frequency sonoreactors

Abstract

In this study, the effect of liquid height on sonochemical oxidation reactions was investigated for two sizes of bath-type sonoreactors under very similar electrical power inputs for 291kHz (74.5W±2.1W and 74.9W±4.4W) and 448kHz (87.2W±4.6W and 92.4W±4.7W). Calorimetry, the H2O2 measurement method, KI dosimetry, and the luminol method were applied to 53 experimental cases, and the results were quantitatively and qualitatively compared. The highest cavitational yields for H2O2 and I3− were observed at liquid heights of 26mm and 17mm for 291kHz and 448kHz, respectively, and these liquid heights are equivalent to a wavelength of 5λ for both frequencies. Moreover, it was found that the optimal liquid heights for the maximum cavitational yields could be roughly determined as the liquid height where the maximum calorimetric power was obtained. Interestingly, there were no significant differences between the two sonoreactors in terms of calorimetric powers or cavitational yields. This similarity occurred because the boundaries, i.e., reactor side walls, provided no significant inhibition for the sonochemically active zone, which was visually confirmed using sonochemiluminescence image analysis. It was also found that the reaction kinetics should be considered to geometrically optimize sonochemical processes for the removal of aqueous pollutants such as bisphenol-A. Using results obtained in this study and those reported previously, brief guidelines for the geometric optimization of sonochemical oxidation reactions in bath-type high-frequency sonoreactors are provided.