Kinetics and Mechanism of the Sonolytic Degradation of Chlorinated Hydrocarbons:  Frequency Effects

Hung, Hsin-Chia; Hoffmann, Michael R.

doi:10.1021/jp9845930

Cited by 172 publications

(162 citation statements)

References 34 publications

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“…The initial concentration was held constant in their experiments at 0.20 " 0.05 mM (~300 mg/L). Loss of CCl 4 due to volatilization was found to be less than 2% in separately run control experiments conducted in the absence of sonication [Hung and Hoffmann, 1999]. The pH after sonolytic degradation of CCl 4 were near 3.5; the principal products observed were OCl -, Cl -, C 2 Cl 4 , and C 2 Cl 6 [Hung and Hoffmann, 1999].…”

Section: Task 4 Conduct Continuous-flow Experiments For Degradation mentioning

confidence: 88%

“…Even with a small headspace in their reactor, loss of CCl 4 due to volatilization during sonolysis was negligible [Hua and Hoffmann, 1996a]. 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].…”

Section: Treatmentmentioning

confidence: 94%

“…Loss of CCl 4 due to volatilization was found to be less than 2% in separately run control experiments conducted in the absence of sonication [Hung and Hoffmann, 1999]. The pH after sonolytic degradation of CCl 4 were near 3.5; the principal products observed were OCl -, Cl -, C 2 Cl 4 , and C 2 Cl 6 [Hung and Hoffmann, 1999]. The distribution of products and chemical intermediates after 90 minutes of ultrasonic treatment is summarized in Table 6 below.…”

Section: Task 4 Conduct Continuous-flow Experiments For Degradation mentioning

confidence: 96%

“…The distribution of products and chemical intermediates after 90 minutes of ultrasonic treatment is summarized in Table 6 below. In more recent work, Hung and Hoffmann [1999] monitored the degradation products of CCl 4 and CHCl 3 degradation under sonolysis. Using a 0.2 mM solution of CCl 4 , the highest concentrations of C 2 Cl 4 and C 2 Cl 6 observed were 80 nM and 25 nM, respectively, accounting for ~0.04% of CCl 4 appearing as C 2 Cl 4 and <0.0125% of CCl 4 appearing as C 2 Cl 6 , respectively.…”

Section: Task 4 Conduct Continuous-flow Experiments For Degradation mentioning

confidence: 99%

“…The extent of degradation of CCl 4 exceeded 99% after 90 minutes of sonolysis [Hung and Hoffmann, 1999]. Hung and Hoffmann [1999] noted that C 2 Cl 6 and C 2 Cl 4 , produced as intermediates during the sonolytic degradation of CCl 4 , are also readily degraded during aqueous-phase sonication.…”

Section: Task 4 Conduct Continuous-flow Experiments For Degradation mentioning

confidence: 99%

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

Peters

Manning

Ayyıldız

et al. 2005

ACS Symposium Series

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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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Section: Task 4 Conduct Continuous-flow Experiments For Degradation mentioning

confidence: 88%

Section: Treatmentmentioning

confidence: 94%

Section: Task 4 Conduct Continuous-flow Experiments For Degradation mentioning

confidence: 96%

Section: Task 4 Conduct Continuous-flow Experiments For Degradation mentioning

confidence: 99%

Section: Task 4 Conduct Continuous-flow Experiments For Degradation mentioning

confidence: 99%

See 3 more Smart Citations

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

Peters

Manning

Ayyıldız

et al. 2005

ACS Symposium Series

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Sonophotocatalytic reactors for wastewater treatment: A critical review

2004

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Mechanistic features of the sonochemical degradation of organic pollutants

Sivasankar

Moholkar

2008

AIChE Journal

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This work considers the mechanistic features of sonochemical degradation of volatile (chlorobenzene) and nonvolatile (phenol) organic pollutants. The sonochemical degradation of pollutant occurs in two pathways: thermal pyrolysis and hydroxylation. By coupling experimental results to bubble dynamics model, we have tried to establish relative contribution of these pathways to degradation of two kinds of pollutants. It is revealed that degradation of volatile pollutants occurs primarily by thermal pyrolysis while hydroxylation is the predominant mechanism of degradation of nonvolatile pollutants. The simulation results also help explain some interesting trends observed in degradation with reaction parameters such as initial pollutant concentration and salt addition to solution. These parameters are found to influence both pathways of degradation that leads to enhancement in degradation. However, the extent of this influence on hydroxylation and pyrolysis pathways is different for phenol and chlorobenzene. This is attributed to different partitioning behavior and solubility of the two pollutants.

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Kinetics and Mechanism of the Sonolytic Degradation of Chlorinated Hydrocarbons: Frequency Effects

Cited by 172 publications

References 34 publications

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

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

Sonophotocatalytic reactors for wastewater treatment: A critical review

Mechanistic features of the sonochemical degradation of organic pollutants

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