Mechanistic approach to enhancement of the yield of a sonochemical reaction

In this study, a mechanistic approach has been taken to enhance yield of a sonochemical reaction. Formation of highly reactive free radicals due to the transient collapse of cavitation bubbles is the primary mechanism of a sonochemical reaction. A physical (reduction in dissolved gas concentration) and a chemical (increasing the reactant concentration) technique is used for enhancing yield of a sonochemical reaction using those techniques, which influence the phenomenon of radical formation by the cavitation bubbles. A bubble dynamics model is used for explaining the sonochemical phenomena. In a degassed medium, the ultrasound wave undergoes lesser attenuation; moreover, equilibrium size of a bubble shrinks due to rectified diffusion. Because of this, a bubble undergoes more violent collapse, resulting in greater production of radicals that give higher yield. On the other hand, increasing the initial reactant concentration shows an adverse effect on the sonochemical yield. This is ascribed to reduction in water vapor flux in the bubble due to reduction of vapor pressure of the medium. This study, therefore, demonstrates as how macroscopic manifestation (the sonochemical yield) of the microscopic phenomena (transient collapse of cavitation bubble) is a complicated function of several physical processes. The results of this study shed light on the complex and multifaceted physical mechanism of a sonochemical reaction, which may be useful in maximization of yield of other sonochemical systems. (c) 2007 American Institute of Chemical Engineers.