Introduction

The concept of the generation of ultrasound was established and it dates back to the early 1880s, with the discovery of the piezoelectric effect by the Curies. Wood and Loomis were the first to note the advantages of using ultrasound in chemistry. They observed that chemical reactions were not a consequence of the heat but a consequence of sonic energy. The term "sonochemistry" is used to describe the applications of ultrasound in diverse fields such as food processing, stabilization of oil emulsions, particle size reduction, filtering systems for suspended particles, homogenization, atomization and environmental protection. Chemical reactions in homogeneous systems proceed via radical intermediates. It means that sonication is able to affect reactions proceeding via radical formations and it does not affect ionic reactions. Most of the modern ultrasonic devices rely on transducers, which are composed of piezoelectric materials. A bath or ultrasonic horn is used to carry out sonochemical reactions.