Understanding of the impact of ultrasound on chemical system is termed as sonochemistry
- Remove kidney stone without surgery
- Treat cartilage injuries
- Image fetal development during pregnancy
- Another widespread application of ultrasonic instruments is in root canal surgery – known as endodontic.
Chemistry associated with ultra sound is called sonochemistry.
Unlike electromagnetic radiation, acoustic waves don‘t change the electronic, vibrational or rotational molecular states. The chemical effect of ultrasound arises due to cavitation phenomenon. It is reported that there is no direct interaction taking place between the sound wave and the solute particle when it is irradiated with ultra sound. This indicates that there are some other phenomena taking place when it is irradiated. Generally sound wave causes the vibrational motion of the molecule. When the frequency increases the vibrational motion, cannot hold the molecule intact as a result a cavity is formed. When ultra sound passes through a liquid medium Positive and negative pressure is exerted on a liquid, breaks the van der waals forces which maintain the liquid molecules together. Thus gas-filled microbubles starts growing.
Under the action of destabilizing forces, the bubbles collapse. For example, as shown in Fig 1, a bubble is formed and it grows in successive cycles. When it reaches an unstable state it collapses and it will produce an unusual environment for the reaction. This is termed as cavitation. The formation, growth and collapsing of bubbles are called acoustic cavitation. This increases the temperature and pressure. Bubbles are formed during the rarefaction stage and undergo compression during compression stage. But the rate of expansion during rarefaction stage is more compared to its contraction during compression stage. This is the major mechanism behind the sonochemistry.
STABLE AND TRANSIENT CAVITATION
THEORIES OF CAVITATION
The temperature and pressure generated in stable cavitation is
LOCAL ELECTRIFICATION THEORY
- Nucleation- formation of bubbles
- Growth – growth of bubbles
- Collapse- collapse of bubbles.
MAJOR REACTIONS DURING ULTRASOUND IRRADIATION,
Eg: chloroform, carbon tetra chloride.
SITES OF CHEMICAL REACTIONS IN CAVITATION BUBBLE
SONO PHOTO CATALYSIS
Kyuichi Yasui (2011) Fundamentals of Acoustic Cavitation and sonochemistry Pankaj and M Ashokkumar (ed) Theoretical and Experimental Sonochemistry Involving Inorganic systems Springer Dordrecht Heidelberg London New York pp 1-25
Low-frequency ultrasound in biotechnology: state of the art Ekaterina V. Rokhina1Piet Lens2 and Jurate Virkutyte1
Industrial & Engineering Chemistry Research 2001, 40: 4681-4715.
Environmental Science & Technology 2005, 39: 3409-3420.
Green Chemistry 1999, 1: 115
Science of The Total Environment 2009, 407: 2474-2492
Ultrasonics Sonochemistry 2009, 16: 583–589
Applied Catalysis B: Environmental 74 (2007) 63–72