Effects of ultrasound on two-phase systems

As previously explained, the effects of ultrasound on homogeneous systems are dominated by the enormous changes in pressure and temperature created at hot spots on implosion of the cavitation bubbles. However, in two-phase systems a number of other factors must be taken into consideration. The relative contributions of these phenomena have not been conclusively established in any one case. It appears that effects seen in liquid/liquid systems are principally due to emulsification which occurs when the shearing stresses on the liquid are greater than the interfacial surface tension. In a number of cases this enormous increase in surface area of... 

Hydrolysis. Ultrasound assistance to hydrolysis reactions largely involves organic systems — both liquids and solid-liquid systems, which are dealt with here simply to reduce the number of subheadings — but also in inorganic systems — mostly heterogeneous. One example of the latter is the improved photocatalytic activity of titania-only materials fabricated by an ultrasound-assisted hydrolysis process, on which US has an elusive effect [41]. In any case, organic hydrolysis is by far a much common application of US. These reaotions almost invariably require high-intensity ultrasound [42,43]. When two immiscible phases are involved — which is most often — the authors consider the liquid-liquid interphase as interface [44]. 

---