10 Effect of liquid height and surface for sonochemical reactor(Basic Science of Sonochemistry)

Volume dependence of chemical effect has been investigated for laboratory scale reaction vessel. However, for sonochemical reactor designed for practical usages, few studies have been carried out. In this work, we constructed the cylinder type sonochemical reaction vessel whose volume was in 1 dm^3 order and investigated the effect of liquid height and liquid surface on the chemical effects of the ultrasound. The height of the reactor was 150 cm and the inner diameter was 7 cm. The Langevin type transducer provided from Honda Electronics Co. Ltd. was attached at the bottom face. The driving frequency was 128.9 kHz and the driving voltage was ca. 200V. A moving reflector can be attached the other side of the surface. The chemical effect was estimated by the concentration of I_3^- produced from the sonochemical oxidation of the aqueous solution of the potassium iodide. At the liquid height below about 25 cm, the concentration of I_3^- strongly depended on the liquid height in related with the standing wave condition. The concentration of I_3^- produced by the sonochmical oxidation for the reaction vessel without reflector was larger than that with reflector. We took the photograph of luminol fluorescence induced by the ultrasound with and without reflector. The contrast corresponding to the node and anti-node of the standing wave was observed. The contrast for the reaction vessel with the reflector was stronger than that without the reflector. The brightness of photograph without the reflector was higher than that with the reflector. The vibration of the liquid surface was observed for the reaction vessel without the reflector. This vibration may affect the standing wave condition and thus gives the different results with or without reflector. When the liquid height was higher than 40 cm, no distinct difference was observed with ant without the reflector.