An Investigation of Homogeneous and Heterogeneous Sonochemistry for Destruction of Hazardous Waste - Final Report - 09/15/1996 - 09/14/2000

During the last 20 years, various legislative acts have mandated the reduction and elimination of water and land pollution. In order to fulfill these mandates, effective control and remediation methods must be developed and implemented. The drawbacks of current hazardous waste control methods motivate the development of new technology, and the need for new technology is further driven by the large number of polluted sites across the country. This research explores the application and optimization of ultrasonic waves as a novel method by which aqueous contaminants are degraded. The primary objective of the investigation is to acquire a deeper fundamental knowledge of acoustic cavitation and cavitation chemistry, and in doing so, to ascertain how ultrasonic irradiation can be more effectively applied to environmental problems. Special consideration is given to the types of problems and hazardous chemical substrates found specifically at Department of Energy (DOE) sites. The experimental work is divided into five broad tasks, to be completed over a period of three years. The first task is to explore the significance of physical variables during sonolysis, such as ultrasonic frequency. The second aim is an understanding of sonochemical degradation kinetics and by-products, complemented by information from the detection of reactive intermediates with electron paramagnetic resonance. The sonolytic decomposition studies will focus on polychlorinated biphenyls (PCBs). Investigation of activated carbon regeneration during ultrasonic irradiation extends sonochemical applications in homogeneous systems to heterogeneous systems of environmental interest. Lastly, the physics and hydrodynamics of cavitation bubbles and bubble clouds will be correlated with sonochemical effects by performing high-speed photographic studies of acoustically cavitating aqueous solutions. The most important benefit will be fundamental information which will allow a more optimal application of ultrasonic irradiation to environmental problems