Enhancement of sonochemical oxidation reactions using air sparging in a 36 kHz sonoreactor.

The effect of air sparging on sonochemical oxidation reactions was investigated using a relatively large reactor equipped with a 36 kHz transducer module at the bottom. KI dosimetry and luminol techniques were used for quantitative and qualitative analysis of the reactions. The cavitation yield increased and then varied minimally as the liquid height increased from 1λ (42 mm) to 8λ (333 mm) with no air sparging. The flow rate of the air used for sparging and the position of the sparger significantly affected the extent of the sonochemical oxidation reactions. A significant enhancement in the sonochemical oxidation by air sparging was observed for higher liquid height and higher flow rate conditions at a constant input power. This enhancement is attributed to the violent mixing effect and the significant change in the sound field and cavitation-active zone in the liquid. Higher sonochemical activity was obtained when air sparging was applied closer to the transducer module at a higher flow rate. Imaging the motion of the liquid surface and sonochemiluminescence revealed that the instability of the liquid body was directly related to the sonochemical activity.