Oxidative degradation of phenols in sono-Fenton-like systems upon high-frequency ultrasound irradiation

• Published in: Russian Journal of Physical Chemistry A Vol. 91; no. 12; pp. 2331 - 2336
• Main Authors: Aseev, D. G., Sizykh, M. R., Batoeva, A. A.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.12.2017; Springer Nature B.V
• Subjects: Cavitation; Chemical Kinetics and Catalysis; Chemistry; Chemistry and Materials Science; Chlorophenol; Conversion; Degradation; Hydrogen peroxide; Irradiation; Low concentrations; Oxidation; Phenols; Physical Chemistry; Pollutants; Reaction kinetics; Trichlorophenols; Ultrasonic imaging; sulfate radical anion; advanced oxidation processes; hydroxyl radical; reactive oxygen species; high frequency ultrasound; chlorophenols; sonochemical oxidation
• ISSN: 0036-0244; 1531-863X
• DOI: 10.1134/S0036024417110024

The kinetics of oxidative degradation of phenol and chlorophenols upon acoustic cavitation in the megahertz range (1.7 MHz) is studied experimentally in model systems, and the involvement of in situ generated reactive oxygen species (ROSs) is demonstrated. The phenols subjected to high frequency ultrasound (HFUS) are ranked in terms of their rate of conversion: 2,4,6-trichlorophenol > 2,4-dichlorophenol ~ 2-chlorophenol > 4-chlorophenol ~ phenol. Oxidative degradation upon HFUS irradiation is most efficient at low concentrations of pollutants, due to the low steady-state concentrations of the in situ generated ROSs. A dramatic increase is observed in the efficiency of oxidation in several sonochemical oxidative systems (HFUS in combination with other chemical oxidative factors). The system with added Fe 2+ (a sono-Fenton system) derives its efficiency from hydrogen peroxide generated in situ as a result of the recombination of OH radicals. The S 2 O 8 2- /Fe 2+ /HFUS system has a synergetic effect on substrate oxidation that is attributed to a radical chain mechanism. In terms of the oxidation rates, degrees of conversion, and specific energy efficiencies of 4-chlorophenol oxidation based on the amount of oxidized substance per unit of expended energy the considered sonochemical oxidative systems form the series HFUS < S 2 O 8 2- /HFUS < S 2 O 8 2- /Fe 2+ /HFUS.