Sonochemical Destruction of Chlorinated C1 and C2 Volatile Organic Compounds in Dilute Aqueous Solution

Bhatnagar, Ashish; Cheung, H. Michael

doi:10.1021/es00057a016

Cited by 131 publications

(74 citation statements)

References 10 publications

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“…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: 97%

“…Sonication of aqueous chloroform with phenol present produced chlorophenols, and with benzene present produced phenol, chlorobenzene, and chlorophenols [Kruus et al, 1998]. Bhatnagar and Cheung [1994] reported no chlorinated organic by-products being observed from sonolysis of C1 and C2 chlorinated compounds.…”

Section: Comparison Of Concentration Of Tca Remaining Usingmentioning

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: Treatmentmentioning

confidence: 97%

Section: Comparison Of Concentration Of Tca Remaining Usingmentioning

confidence: 99%

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

Peters

Manning

Ayyıldız

et al. 2005

ACS Symposium Series

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“…Thus, there is no consistent report on the impact of temperature on the degradation of organic compounds in literature. Bhatnagar and Cheung (1994) reported that the degradation of trichloroethylene and carbon tetrachloride remained constant between -7 to 20 and 20-60°C, respectively. In contrast, Destaillats et al (2000) indicated that the sonochemical degradation of chlorobenzene and TCE, respectively, increased with increasing temperature.…”

Section: Effect Of Sonochemical Reaction Temperaturementioning

confidence: 99%

Ultrasonic removal of pyridine from wastewater: optimization of the operating conditions

Elsayed

2014

Appl Water Sci

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In this study, a fundamental research had been carried out to explore the removal of pyridine in wastewater by ultrasound radiation. The effects of initial pyridine concentration, radiation time, pH, aeration, and the reaction temperature on the pyridine removal efficiency were investigated. The removal rates of pyridine at 180 min sonication time were found to decrease from 53 to 15 % with increasing the initial concentration from 10 to 100 mg/L. However, the total amount of pyridine degraded after 60 min at 100 mg/L was as much as three times larger than that degraded at 10 mg/L. The optimal pH was found to be 9 which resulted in 25 % pyridine removal after 180 min ultrasound radiation. By observing the change of pH value with the sonication time up to 60 min, it was observed that, pH of the sonicated pyridine aqueous mixture has decreased from 9.2 to 6.2 during the irradiation. The decrease in the pH may be attributed due to the formation of peroxy radicals in the solution and subsequently formation of oxygen free radicals. The simultaneous aeration could improve pyridine removal efficiency of ultrasound irradiation by 24 %. With increasing media temperatures, the removal efficiencies of pyridine increased in the temperature range in this study. In the end, it could be proposed that ultrasound radiation was an effective method for the removal of pyridine from wastewater.

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Section: Introductionunclassified

“…A decomposição sonoquímica de CCl 4 em solução aquosa é baseada neste fundamento, ou seja, moléculas de CCl 4 migram para as bolhas de cavitação e, devido à alta energia gerada no colapso, as ligações C-Cl são homoliticamente rompidas, originando os radicais •CCl 3 e •Cl. Os efeitos da sonólise do CCl 4 vêm sendo objeto de diversos estudos [11][12][13][14][15][16][17] .O CCl 4 e outros solventes orgânicos clorados são empregados em procedimentos de análise química para a solubilização de alguns reagentes cromogênicos 18 e de outras espécies como tetracloreto de titânio 19 , extração por solvente 20 , para gerar cloretos voláteis em atomização em forno de grafite 21 e para algumas determinações espectrofotométricas nas regiões do ultravioleta, visível e infravermelho.Os produtos iniciais da sonólise do CCl 4 abrem uma nova perspectiva de aplicação analítica para compostos orgânicos halogenados voláteis, devido ao elevado poder oxidante dos radicais formados. Neste trabalho foi avaliada a produção de oxidantes provenientes da degradação sonoquímica do CCl 4 , empregando sonicador de baixa potência, pela variação do pH do meio e oxidação dos íons Fe 2+ e I -.…”

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Geração sonoquímica de oxidantes em solução aquosa saturada de tetracloreto de carbono

Borges¹,

Korn²

2002

Quím. Nova

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Recebido em 11/6/01; aceito em 8/11/01 SONOCHEMICAL PRODUCTION OF OXIDIZING SPECIES IN WATER SOLUTION SATURATED WITH CARBON TETRACHLORIDE. In this work the CCl 4 degradation in aqueous solution by sonication with 40 kHz commercial ultrasonic bath was investigated. Sonochemical degradation of CCl 4 occur by the cleavage of C-Cl bond into the cavitation bubbles. Oxidation reactions and the pH decreasing in the bulk solution during sonication were attributed to chlorine radicals produced by CCl 4 sonolysis, leading to increase the chloride concentration. The formation of oxidizing agents was evaluated employing I -and Fe 2+ ion solutions, converted to I 2 and HIO, and Fe 3+ , respectively. The amount of chloride and hydronium ions produced after 3 min of irradiation was 11.52 and 12.19 mmol, respectively, suggesting that the same reaction was involved to produce these ions. Fe 2+ oxidation and the pH variation were monitored to estimate chlorine radical formation rate in the presence (0.107 mmol s -1 ) and absence (0.092 mmol s -1 ) of metallic ion during the first minute of sonication.Keywords: sonochemical reactions; oxidizing species generation; carbon tetrachloride sonolysis. INTRODUÇÃOOs efeitos químicos provocados pelos ultra-sons ocorrem devido ao fenômeno da cavitação acústica, que é o processo de nucleação, crescimento e colapso de bolhas transientes em líquidos expostos a ondas ultra-sônicas de baixa frequência (< 1 MHz) 1 . As ondas ultrasônicas se propagam através de um líquido em ciclos alternados de compressão e expansão, porém, caso a onda acústica tenha pressão suficientemente alta, pode vencer as forças intermoleculares num ponto do líquido, criando uma cavidade para a qual podem se difundir, durante a etapa de expansão, os gases e vapores presentes no líquido. Na etapa de compressão os gases e vapores não retornam completamente para o líquido, resultando em aumento efetivo do tamanho da cavidade durante os ciclos seguintes de compressão e expansão até que seja atingido seu diâmetro crítico, entrando em violento colapso 2 . O colapso das bolhas transientes provoca a liberação de grande quantidade de energia, gerando temperaturas locais instantâneas muito elevadas (5200 K) e pressões da ordem de centenas de atmosferas 3,4 .O processo de cavitação e as temperaturas geradas no colapso são fortemente dependentes da pressão de vapor do solvente. Assim, moléculas de solventes com altas pressões de vapor (e.g. moléculas de água) podem penetrar nas cavidades e, no momento do colapso, sofrerem sonólise, resultando na formação de novos produtos (e.g. H 2 e H 2 O 2 ).Propriedades físico-químicas dos gases dissolvidos (condutividade térmica, capacidade calorífica, pressão parcial e solubilidade no solvente) garantirão a eficiência da cavitação e, conseqüentemen-te, da sonólise 5,6 . Em outra aproximação, sabe-se que a eficiência de cavitação depende da freqüência e amplitude das ondas acústicas, potência do sonicador, bem como da tensão superficial, força iônica e temperatura do meio solvente 7 . Também, a pre...

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Sonochemical Destruction of Chlorinated C1 and C2 Volatile Organic Compounds in Dilute Aqueous Solution

Cited by 131 publications

References 10 publications

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

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

Ultrasonic removal of pyridine from wastewater: optimization of the operating conditions

Geração sonoquímica de oxidantes em solução aquosa saturada de tetracloreto de carbono

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