Ultrasonic waste-water treatment: incidence of ultrasonic frequency on the rate of phenol and carbon tetrachloride degradation

Abstract

Organic compounds in aqueous solution submitted to an ultrasonic irradiation behave differently according to their physical and chemical properties. In this work, hydrogen peroxide formation and the degradation rate of phenol and carbon tetrachloride have been studied at different frequencies: 20, 200, 500 and 800 kHz. Whatever the frequency, it is easier to decompose CCl4 than phenol by means of ultrasonic wave. It is shown that the rates of reactions involving hydroxyl radicals (hydrogen peroxide formation and phenol degradation) have a maximum value at 200 kHz. The best yield observed at 200 kHz for the phenol degradation may be the result of better HO radicals availability outside of the bubble of cavitation. The degradation rate for carbon tetrachloride which decomposes into the bubble of cavitation increases with frequency. Calculating the reaction rate for one ultrasonic period shows that the efficiency of one ultrasonic cycle decreases as frequency increases.

Sonochemical Treatment of Water Polluted by Chlorinated Organocompounds. A Review

“…Conversely, even if the low-frequency collapse is more productive, there are less collapses per second at low frequency than at high frequency. An optimum is therefore expected, and is indeed observed experimentally [79]. This is of course dependent on the size of the bubbles involved.…”

Influence of ultrasonic waves on the removal of different oil components from oily sludge

“…[16,17] Ultrasonic pressure was measured using a CS-3 hydrophone (sensitivity, 2.2 μV/Pa; Institute of Acoustics, Chinese Academy of Sciences). The ultrasonic intensity I (W/m 2 ) was calculated using the following equation [18]:…”

Sonochemical degradation of Basic Red 29 in aqueous media

“…23 Accordingly, the sonochemical degradation of an organic compound can occur in gasphase pyrolysis and oxidation for volatile substrates and by reaction with HO • radicals at the bubble/liquid interface and in the aqueous phase for nonvolatile substrates. 24 In the absence of solutes in the solution, the primary active species of sonolysis mostly recombine at the bubble solution interface to form hydrogen peroxide (Eqs. (1) and (2)).…”

“…(1) and (2)). 24 Cavitation bubbles due to the very high temperatures generated at the final stages of bubble collapse emit light that is known as sonoluminescence.…”