Ethers as pollutants in groundwater: the role of reaction parameters during the aquasonolysis

Lifka, Jan; Hofmann, Jörg; Ondruschka, Bernd

doi:10.2166/wst.2001.0271

Cited by 7 publications

(8 citation statements)

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“…Over the past decade or so, there has been growing interest in the effect of frequency on acoustic cavitation and its associated sonochemical effects. ,,− The main reason for this lies in the potential for enhancing a sonochemical effect for a given energy input to the system, with the wider aim of gaining a better understanding of the underlying cavitation process at different frequencies. However, many aspects of cavitation in the multibubble field change when the frequency of sonolysis is altered.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Surfactants at the Gas/Solution Interface of Cavitation Bubbles: An Ultrasound Intensity-Independent Frequency Effect in Sonochemistry

2002

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A major limitation in determining the effects of ultrasound frequency in sonochemistry in relation to cavitation is that no reliable relationship exists between the energy supplied to the system and the energy converted by the cavitation process in producing a sonochemical effect. However, the current study presents a frequency effect that is independent of the energy supplied to the system. Spin-trapping of secondary carbon radicals with 3,5-dibromo-4-nitrosobenzenesulfonic acid-d 2 (DBNBS-d 2 ) and electron paramagnetic resonance (EPR) have been used to determine the relative ability of two nonvolatile surfactants [sodium 1-pentanesulfonic acid (SPSo) and sodium dodecyl sulfate (SDS)] to scavenge • H atoms and • OH radicals at the gas/solution interface of cavitation bubbles. The results obtained at 354 and 1057 kHz are compared to those observed previously at 47 kHz (Sostaric, J. Z.; Riesz, P. J. Am. Chem. Soc. 2001, 123, 11010-11019). At particular bulk surfactant concentrations, both surfactants reached a limiting plateau value in radical scavenging ability. At 354 kHz (and 47 kHz), the magnitude of this plateau was greater for SPSo compared to that for SDS. However, at 1057 kHz, no difference in the plateau value was observed between SPSo and SDS. Decreasing the ultrasound intensity at constant frequency during the sonolysis of SPSo and SDS resulted in a decrease in the -• CH-radical yield. However, there was no change in the relative plateau yield of -• CH-radicals between SPSo and SDS. Thus, at plateau concentrations, the relative ability of these n-alkyl chain surfactants to scavenge radicals at the gas/solution interface of cavitation bubbles depends on the frequency of sonolysis but is independent of ultrasound intensity. The results were interpreted in terms of a decrease in the rate of change of the surface area of "high-energy-stable cavitation bubbles" at higher frequencies. This would affect the relative adsorption and hence radical scavenging efficiencies of SPSo and SDS at the gas/solution interface of these types of cavitation bubbles.

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Section: Introductionmentioning

confidence: 99%

Adsorption of Surfactants at the Gas/Solution Interface of Cavitation Bubbles: An Ultrasound Intensity-Independent Frequency Effect in Sonochemistry

2002

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“…Recent studies of various treatment approaches have appeared in the literature (Keller et al, 2000). Chemical treatment technologies include the use of ozone-hydrogen peroxide mixtures (i.e., peroxone) (Mitani et al, 2002;Safarzadeh-Amiri, 2001), catalytic oxidation (Mitani et al, 2001), UV-hydrogen peroxide (Cater et al, 2000;, and sonolysis (Kang and Hoffmann, 1998;Kang et al, 1999;Lifka et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

The Sonolytic Destruction of Methyl tert‐Butyl Ether Present in Contaminated Groundwater

Hung

Kang

Hoffmann

2002

Water Environment Research

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Ultrasonic irradiation in the presence of ozone was used to efficiently eliminate methyl tert-butyl ether (MTBE) from groundwater. The sonolytic degradation of MTBE was investigated in three different reactor configurations and frequencies: vibrating-plate reactor (VPR, 358 kHz), near-field acoustical processor (NAP 20 and 16 kHz), and radial-tube resonator (RTR, 20 kHz). The sonochemical reactors can be ordered in terms of their efficiency with respect to the degradation of MTBE in the following way: VPR Ͼ RTR Ͼ NAP. The higher elimination rates of MTBE in groundwater by combined ultrasound-ozone systems are attributed to the effective conversion of ozone to the OH radical, even in the presence of high alkalinity. Carbonate radicals, which were formed from the oxidation of bicarbonate by hydroxyl radicals, are shown to react with MTBE via a hydrogen-atom abstraction pathway. Methyl-tert-butyl ether was also rapidly eliminated from the groundwater underlying a major international airport by direct chemical oxidation with a mixture of hydrogen peroxide and ozone. Water Environ. Res., 74, 545 (2002).

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“…Analyses of the first sample compared to subsequent samples enabled an estimate of the mass conservation to be performed. Of particular interest is whether the application of ultrasound results in degradation of the reactant cinnamaldehyde into (undesirable) products such as carbon dioxide, hydrogen, and water, as has been observed for aqueous organic solutions previously [18,19].…”

Section: Reactant and Product Sample Analysesmentioning

confidence: 99%

Ultrasound-assisted hydrogenation of cinnamaldehyde

Disselkamp

Hart

Williams

et al. 2005

Ultrasonics Sonochemistry

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The hydrogenation, employing hydrogen gas, of cinnamaldehyde was performed using Pd-black and Raney Ni catalysts at 298+/-3 K in a water-cooled (jacketed) reaction vessel. Sampling at pre-determined time intervals and GC/MS analysis yielded time-dependent product state distribution information. A kinetic modeling of the data revealed that cinnamaldehyde was both hydrogenated directly to the final product benzenepropanol, as well as a fraction being converted to the intermediate benzenepropanal, where the latter was subsequently hydrogenated to benzenepropanol. Comparing the ultrasound-assisted and blank (stirred) experiments revealed that a higher maximum relative concentration of the intermediate benzenepropanal was formed in the ultrasound experiments compared to the stirred experiment. The activity of the ultrasound experiments compared to blank were 9-fold and 20-fold greater for the Pd-black and Raney Ni catalysts, respectively. Finally, an application of the Bell-Evans-Polanyi principle to yield an estimate of the ratio of rate coefficients for benzenepropanal and benzenepropanol formation was performed by considering chemical group energy differences and surface adsorption energy differences in the first mechanistic step of hydrogenation.

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Ethers as pollutants in groundwater: the role of reaction parameters during the aquasonolysis

Cited by 7 publications

References 0 publications

Adsorption of Surfactants at the Gas/Solution Interface of Cavitation Bubbles: An Ultrasound Intensity-Independent Frequency Effect in Sonochemistry

Adsorption of Surfactants at the Gas/Solution Interface of Cavitation Bubbles: An Ultrasound Intensity-Independent Frequency Effect in Sonochemistry

The Sonolytic Destruction of Methyl tert‐Butyl Ether Present in Contaminated Groundwater

Ultrasound-assisted hydrogenation of cinnamaldehyde

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