Sonochemical degradation of dilute aqueous solutions of 2-, 3- and 4-chlorophenol and pentachlorophenol has been investigated under air or argon atmosphere. The degradation follows first-order kinetics in the initial state with rates in the range 4.5-6.6 microM min-1 under air and 6.0-7.2 microM min-1 under argon at a concentration of 100 microM of chlorophenols. The rate of OH radical formation from water is 19.8 microM min-1 under argon and 14.7 microM min-1 under air in the same sonolysis conditions. The sonolysis of chlorophenols is effectively inhibited, but not completely, by the addition of t-BuOH, which is known to be an efficient OH radical scavenger in aqueous sonolysis. This suggests that the main degradation of chlorophenols proceeds via reaction with OH radicals; a thermal reaction also occurs, although its contribution is small. The addition of appropriate amounts of Fe(II) ions accelerates the degradation. This is probably due to the regeneration of OH radicals from hydrogen peroxide, which would be formed from recombination of OH radicals and which may contribute a little to the degradation. The ability to inhibit bacterial multiplication of pentachlorophenol decreases with ultrasonic irradiation.
Ultrasonic inactivation of Escherichia coli XL1-Blue has been investigated by high-intensity ultrasonic waves from horn type sonicator (27.5 kHz) utilizing the "squeeze-film effect". The amplitude of the vibration face contacting the sample solution was used as an indication of the ultrasonic power intensity. The inactivation of the E. coli cells by ultrasonic irradiation shows pseudo first-order behavior. The inactivation rate constant gradually increased with increasing amplitude of the vibration face and showed rapid increase above 3 microm (p-p). In contrast, the H2O2 formation was not observed below 3 microm (p-p), indicating that the ultrasonic shock wave might be more important than indirect effect of OH radicals formed by ultrasonic cavitation in this system. The optimal thickness of the squeeze film was determined as 2 mm for the E. coli inactivation. More than 99% of E. coli cells was inactivated within 180-s sonication at the amplitude of 3 microm (p-p) and 2 mm of the thickness of the squeeze film.
We have investigated the inactivation of Saccharomyces cerevisiae (yeast cells) by ultrasonic irradiation. The amplitude on the vibration face contacting the sample solution was used as an indication of the ultrasonic power intensity. The effects of the amplitude on the vibration face and the initial cell numbers on the sonolytic inactivation of yeast cells have been investigated using a horn-type sonicator (27.5 kHz). The inactivation of the yeast cells by ultrasonic irradiation shows pseudo first-order behavior. The inactivation rate constant varied from 0.0007 to 0.145 s(-1) when the amplitude on the vibration face was in the range of 1-7 microm(p-p). The change in the inactivation rate constant as a function of the amplitude on the vibration face was similar to that of the OH radical formation rate under the same conditions. The threshold of this sonicator was 3 microm(p-p) with the amplitude on the vibration face. The initial cell numbers (from 10(2) to 10(5) mL(-1)) had an influence on the inactivation of the yeast cells by ultrasonic irradiation. The inactivation rate constants varied from 0.023 to 6.4 x 10(-3) s(-1), and the inactivation by ultrasonic irradiation was fastest at the lowest initial cell numbers. In a squeeze-film-type sonicator (26.6 kHz), 90% inactivation of the yeast cells was achieved by ultrasonic irradiation for 60 min.
The degradation of phthalic acid esters in an aqueous solution by sonochemical action was performed at an ultrasonic frequency of 200 kHz. The sonochemical degradation of phthalic acid esters followed pseudo first-order kinetics. The OH radical reaction was found to be a predominant factor of the degradation of diethyl phthalate in the pH range 4−11. However, over pH 11, the degradation rate was accelerated with an increased pH due to the increased hydrolysis. From experiments involving stirring and ultrasonic irradiation, the accelerated degradation by hydrolysis in the presence of ultrasound was also established. The accelerated hydrolysis of phthalic acid esters by sonochemical action may be due to the existence of a sphere in which a temperature higher than that in the bulk solution is present.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.