Ultrasonic has become a research hotspot in the world due to its production in mass transfer, heat transfer and chemical reaction. With the development and popularization of ultrasonic power equipment, some progress has been made in industrialization in Europe and America. The development of science and technology in China has become a new interdisciplinary – sonochemistry. Its development has been influenced by a great deal of work done in theory and application.

The so-called ultrasonic wave generally refers to the acoustic wave with a frequency range of 20k-10mhz. Its application power in the chemical field mainly comes from ultrasonic cavitation. With strong shock wave and microjet with velocity higher than 100m / s, the high gradient shear of shock wave and microjet can generate hydroxyl radicals in aqueous solution. The corresponding physical and chemical effects are mainly mechanical effects (acoustic shock, shock wave, microjet, etc.), thermal effects (local high temperature and high pressure, overall temperature rise), optical effects (sonoluminescence) and activation effects (hydroxyl radicals are generated in aqueous solution). The four effects are not isolated, Instead, they interact and promote each other to speed up the reaction process.

At present, the research of ultrasound application has proved that ultrasound can activate biological cells and promote metabolism. Low intensity ultrasound will not damage the complete structure of the cell, but it can enhance the metabolic activity of the cell, increase the permeability and selectivity of the cell membrane, and promote the biological catalytic activity of the enzyme. The high-intensity ultrasonic wave can denature the enzyme, make the colloid in the cell undergo flocculation and sedimentation after strong oscillation, and liquefy or emulsify the gel, thus making the bacteria lose biological activity. In addition. The instantaneous high temperature, temperature change, instantaneous high pressure and pressure change caused by ultrasonic cavitation will kill some bacteria in the liquid, inactivate the virus, and even destroy the cell wall of some small emblem organisms. Higher intensity ultrasound can destroy the cell wall and release the substances in the cell. These biological effects are also applicable to the effect of ultrasound on the target. Because of the particularity of algal cell structure. There is also a special mechanism for ultrasonic algae suppression and removal, that is, the air bag in the algal cell is used as the cavitation nucleus of the cavitation bubble, and the air bag is broken when the cavitation bubble is broken, resulting in the algal cell losing the ability to control floating.