Cavitation Process :
Cavitation is described as the formation of microbubbles in solution that implode violently after reaching a critical resonance size. These microbubbles can be produced by a number of mechanisms:
- Local increase in water velocity as in eddies or vortices, or over boundary contours
- Rapid vibration of the boundary through sonication
- Separation or parting of a liquid column owing to water hammer
- An overall reduction in static pressure
The rapid implosion of cavitation microbubbles results in high temperatures at the bubble/water interface, which can trigger thermal decomposition of the MTBE in solution or thermal dissociation of water molecules to form extremely reactive radicals. The extreme conditions generated during cavitation decomposes water to create both oxidizing (•OH) and reducing (•H) radical species. As in other AOPs, the primary mechanism for organic removal by cavitation is through reaction with hydroxyl radicals.
Methods of producing OH radicals via cavitaion:
- Ultrasonic Irradiation or Sonication
- Formation of microbubbles through successive ultrasonic frequency cycles until the bubbles reach a critical resonance frequency size that results in their violent collapse.
- Pulse Plasma Cavitation
- High voltage discharge through water to create microbubbles
- Hydrodynamic Cavitation
- High velocity or pressure gradients to generate microbubbles