Due to its production in mass transfer, heat transfer and chemical reaction, ultrasonic has become a research hotspot all over the world, especially in the United States, Britain, France and other countries. With the development and popularization of ultrasonic power equipment, Japan, Russia and other countries have made some progress in industrialization. The development of science and technology in China has become a new interdisciplinary - sonochemistry. Its development is influenced by the fact that many researchers have done a lot of work in theory and application.
The so-called ultrasonic wave generally refers to the sound wave with frequency range of 20K ~ 10MHz, and its application power in the chemical field mainly comes from ultrasonic cavitation. With the strong shock wave and the micro jet whose velocity is higher than 100 m / s, the high gradient shear of shock wave and micro jet can produce hydroxyl radicals in aqueous solution. The corresponding physicochemical effects are mainly mechanical effects (acoustic shock wave, micro jet, etc.), thermal effects (local high temperature and high pressure, overall temperature rise), optical effects (sonoluminescence) and activation effects (self generated hydroxyl radicals in aqueous solution) The four effects are not isolated, but interact and promote each other to speed up the reaction process.