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Applications of Ultrasound in NAPL Remediation: Sonochemical Degradation of TCE in Aqueous Surfactant Solutions

Destaillats, Hugo and Alderson, Thomas W., II and Hoffmann, Michael R. (2001) Applications of Ultrasound in NAPL Remediation: Sonochemical Degradation of TCE in Aqueous Surfactant Solutions. Environmental Science and Technology, 35 (14). pp. 3019-3024. ISSN 0013-936X. doi:10.1021/es0018926.

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Surfactant-enhanced pump-and-treat technologies increase the efficiency of nonaqueous-phase liquids (NAPLs) removal from soils. However, high concentrations of surfactants in groundwater impose severe limitations to water treatment. In this paper, we explore the applicability of ultrasonic irradiation as an alternative method for surfactant recovery and contaminant degradation. The combined effects of temperature, initial substrate concentration, and concentration of added surfactant (sodium dodecyl sulfate, SDS) were analyzed for the sonolysis of trichloroethylene (TCE) in batch experiments at an ultrasonic frequency of 500 kHz and 77 W/L applied power density. In the range of 5−30 °C, TCE sonolysis becomes faster at higher temperatures, both in the absence and in the presence of surfactant. This indicates that gas-phase pyrolysis prevails over other chemical reactions in the liquid phase. Inhibition of TCE sonolysis was observed in the presence of surfactant at all SDS concentrations. Changes in the initial TCE concentration (from 250 μM to 1.2 mM) showed no effect on the degradation rates in the presence of SDS. For surfactant levels below its critical micelle concentration (cmc), the inhibition of TCE sonolysis exhibited a highly nonlinear dependence with increasing SDS concentration. A correlation was observed in this range between the relative inhibition of sonolysis and the decreasing surface tension of the solutions. Above the cmc up to an SDS concentration of 5%, the reaction rate decreased less markedly. Micellar sequestration of the contaminant seems to be the main reason for this additional inhibition. Bubble growth prior to collapse may incorporate some of the TCE dissolved in the micelles through their adsorption in the expanding bubble walls, thus partially overcoming the scavenging effect due to micellar entrapment of the contaminant.

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Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 2001 American Chemical Society. Received for review November 20, 2000. Revised manuscript received April 3, 2001. Accepted April 19, 2001. Publication Date (Web): June 9, 2001. Financial support provided by the Department of Energy (DOE 1963472402) and the U.S. Navy (N 47408-99-M-5049) is gratefully acknowledged. The authors also thank Dr. A. J. Colussi for helpful discussions.
Funding AgencyGrant Number
Department of Energy (DOE)DOE 1963472402
Office of Naval Research (ONR)N 47408-99-M-5049
Issue or Number:14
Record Number:CaltechAUTHORS:20150807-092336931
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Official Citation:Applications of Ultrasound in NAPL Remediation:  Sonochemical Degradation of TCE in Aqueous Surfactant Solutions Hugo Destaillats, Thomas W. Alderson II, and Michael R. Hoffmann Environmental Science & Technology 2001 35 (14), 3019-3024 DOI: 10.1021/es0018926
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59309
Deposited By: Ruth Sustaita
Deposited On:07 Aug 2015 18:43
Last Modified:10 Nov 2021 22:18

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