Sonochemical Degradation of Pollutants

Abstract

The term sonochemistry describes all chemical processes in which ultrasound irradiation is involved. The interaction of an acoustical field with the irradiated fluid provides new reaction pathways and alters existing chemical processes in the system, usually yielding an enhancement of reaction rates. A distinction should be pointed out between the effects of ultrasound in homogeneous and in heterogeneous media. In the first case, sonochemical reactions are related to new chemical species produced during acoustical cavitation, whereas the enhancement of heterogeneous reactions can also be related to mechanical effects induced in the fluid system by sonication. These effects include an increase in the surface area between the reactants, a faster renovation of catalyst surfaces, and accelerated dissolution and mixing. Although this chapter focuses only on the uses of ultrasound related to the degradation of organic pollutants, we should mention that many other sonochemical processes exist, such as organic and organometallic synthesis, and polymer synthesis and modifications.