Sonoluminescence for Groundwater Remediation

University South Carolina Research Foundation, Columbia SC

Investigators

Abstract

0228690, Richard P. Ray, University of South Carolina - Columbia "Sonoluminescence for Groundwater Remediation" This action is to explore the use of sonoluminescence for groundwater remediation Sonoluminescence, the process of turning sound into light, was discovered over 60 years ago. As sound waves propagate through a liquid, dissolved gases are forced out of solution to form bubbles. The wave of rarefaction is succeeded by a wave of compression, which compresses the gases inside the bubble. When sufficient energy is applied at the proper frequency (usually about 20 kHz) sonoluminescence occurs. For a fraction of a second, the temperature in the bubble can reach ~5,000 ?K and pressures of 500-1000 atmospheres. Such conditions turn the bubble's contents into an incandescent plasma of electrically charged ions, neutral atoms and electrons. At the same time, the bulk solution remains near ambient pressure and temperature. The small gas bubbles make it possible to break apart molecules and produce chemical reactions. The cycle repeats itself with each new wave of rarefaction and compression. The project will begin by reproducing the simplest geometry and system, i.e. single-bubble sonoluminescence, and proceed to more complex conditions. At each stage of experimentation, test parameters such as excitation frequencies, wave shapes, and transducer positioning will be performed. Additionally, the amount of energy input to the system will be carefully monitored. Experimental results should show remediation of the groundwater to drinking level standards with decreased remediation time and cost. This study will focus on bench-scale performance, with pilot-scale potential. Experimental work will be preceded and augmented by standard laboratory testing and computational simulations. The simulations will aid in determining test intensities and durations. Presently there exist a wide variety of techniques to remediate contaminated groundwater. These technologies are often limited by borehole placement, and collect media (air, water) indiscriminately. Therefore, a great deal of treatment energy goes toward handling media that is already clean. The method of sonoluminescence is unique in that it produces heat and cavitation bubbles at a distance from its source. If this process can be manipulated, it should be possible to focus the energy within a prescribed field, releasing, transporting, and possibly breaking down contaminants in soil and groundwater insitu. This process may be coupled with other remediation methodologies (for example, vacuum extraction, pump and treat, surfactant injection) to achieve target levels in a more timely and efficient manner. Economies of treatment are further realized when dealing with DNAPLs (dense non-aqueous phase liquids) and recalcitrant compounds as well as vadose or capillary zone contamination.