Effect of Process Variables on Sonochemical Destruction of Aqueous Trichloroethylene

Suri, Rominder; Paraskewich, M. R.; Qi-bin, Zhang

doi:10.1089/ees.1999.16.345

Cited by 13 publications

(8 citation statements)

References 12 publications

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“…Sonolysis of TCE (aq). The sonolytical degradation of TCE has been reported recently ( − ). The proposed mech anisms for the sonochemical action are based on gas-phase high-temperature pyrolytic initiation steps involving cleavage of the relatively weak C−Cl bond (338 kJ/mol): The chlorinated organic intermediates generated are unstable and disappear from aqueous solution at faster rates than the substrate molecule ().…”

Section: Resultsmentioning

confidence: 99%

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

Destaillats

Alderson

Hoffmann

2001

Environ. Sci. Technol.

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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 degrees 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 microM 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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Section: Resultsmentioning

confidence: 99%

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

Destaillats

Alderson

Hoffmann

2001

Environ. Sci. Technol.

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“…Studies have shown that the streaming and heating generated by ultrasound are able to degrade harmful substances such as estrogen hormones and other chemicals in water (e.g. Suri et al 1999; Fu et al 2007). A limiting underlying assumption of most industrial sono-chemistry applications to the acoustic streaming flows is the spatial homogeneity of the reaction process.…”

Section: Discussionmentioning

confidence: 99%

“…This initial transient process might be the critical period for various applications of environmental sonochemistry as some chemical reactions occur over short time scales at the beginning of the ultrasound treatment, during which the heating and fluid dynamics are not well understood (Suri et al 1999; Fu et al 2007). In this study, understanding of the vortex structure and heating distribution is sought through the identification of developing vortical regions.…”

Section: Introductionmentioning

confidence: 99%

A synchronized particle image velocimetry and infrared thermography technique applied to an acoustic streaming flow

et al. 2011

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Subsurface coherent structures and surface temperatures are investigated using simultaneous measurements of particle image velocimetry (PIV) and infrared (IR) thermography. Results for coherent structures from acoustic streaming and associated heating transfer in a rectangular tank with an acoustic horn mounted horizontally at the sidewall are presented. An observed vortex pair develops and propagates in the direction along the centerline of the horn. From the PIV velocity field data, distinct kinematic regions are found with the Lagrangian coherent structure (LCS) method. The implications of this analysis with respect to heat transfer and related sonochemical applications are discussed.

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“…Loss of CCl 4 due to vapor stripping was found to be less than 2% in separate run control experiments conducted in the absence of ultrasonic irradiation [Hung and Hoffmann, 1999]. Performing control experiments conducted in the absence of ultrasonic irradiation, Suri et al [1999] observed negligible loss of TCE over a 25-minute period at 45 o C. Under ultrasonic irradiation, two experiments were conducted with 0-and 10-mL headspace, respectively; comparison of their results indicated that loss of TCE by volatilization was negligible (<2%) over a 20-minute period [Suri et al, 1999]. Bhatnagar and Cheung [1994], Francony and Petrier [1996], and Hua and Hoffmann [1996a] have also reported negligible loss of TCE during sonolysis.…”

Section: Treatmentmentioning

confidence: 92%

Use of Sonication for in-Well Softening of Semivolatile Organic Compounds

Peters

2000

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EXECUTIVE SUMMARYThis project investigates the in-situ degradation of semivolatile organic compounds (SVOCs) and volatile organic compounds (VOCs) using in-well sonication, in-well vapor stripping, and bioremediation. Pretreating groundwaters with sonication techniques in-situ would form VOCs that can be effectively removed by in-well vapor stripping and bioremediation. The mechanistic studies focus on the coupling of megasonics and ultrasonics to "soften" (i.e., partially degrade) the SVOCs; oxidative reaction mechanism studies; surface corrosion studies (on the reactor walls/well); enhancement due to addition of oxidants, quantification of the hydroxyl radical formation; identification/quantification of degradation products; volatility/degradability of the treated waters; development of a computer simulation model to describe combined in-well sonication/in-well vapor stripping/bioremediation; systems analysis/economic analysis; large laboratory-scale experiment verification; and field demonstration of the integrated technology. Benefits of this approach include: (1) Remediation is performed in-situ; (2) The treatment systems complement each other; their combination can drastically reduce or remove SVOCs and VOCs; (3) Ability to convert hard-to-degrade organics into more volatile organic compounds; (4) Ability to remove residual VOCs and "softened" SVOCs through the combined action of in-well vapor stripping and biodegradation; (5) Does not require handling or disposing of water at the ground surface; and (6) Cost-effective and improved efficiency, resulting in shortened clean-up times to remediate a site.This study examined the ability of an integrated treatment system involving combined sonication and vapor stripping to remove/destroy chlorinated organic compounds from groundwater.The chlorinated solvents studied included carbon tetrachloride (CCl 4 ), trichloroethylene (TCE), trichlorethane (TCA), and tetrachloroethylene (PCE). Contaminant concentrations studied ranged from ~1 to ~100 mg/L. Sonication/vapor stripping experiments were performed in a reactor used to treat the chlorinated organic contaminants in groundwater employing sonication alone, vapor stripping alone, and combined sonication/vapor stripping. The sonicator has an ultrasonic frequency of 20-kHz; the applied power intensity was 12.3-, 25.3-, and 35.8-W/cm 2 . The batch reactions were operated normally for up to 10 minutes treatment time, with samples drawn for GC analysis every 2 minutes. Air injection rates (for the vapor stripping) were nominally 0-(sonication alone), 500-, 1000-, and 1500-mL/min. In the continuous flow studies, the residence time in the reactor was set at 5, 8, and 10 minutes.Results were obtained from batch experiments performed on the various chlorinated organic contaminants (CCl 4 , TCE, TCA, and PCE) using sonication alone, vapor stripping alone, and combined sonication/vapor stripping. For all four chlorinated solvent species, the first order rate constants were in the range of 0.02 to 0.06 min -1 , 0.23 to 0.53 min ...

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Effect of Process Variables on Sonochemical Destruction of Aqueous Trichloroethylene

Cited by 13 publications

References 12 publications

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

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

A synchronized particle image velocimetry and infrared thermography technique applied to an acoustic streaming flow

Use of Sonication for in-Well Softening of Semivolatile Organic Compounds

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