Cavitation-Induced Degradation of Phenol by Ultrasound

Abstract

Aqueous solution of phenol was irradiated with ultrasonic waves of sufficient intensity to induce cavitation. The phenol was exponentially degradated, because of the formation of reactive species produced by water decomposition and reaction with water and oxygen. The degradation pathway for phenol was similar to that of the phenol oxidation with ozone.

<b>Degradation and toxicity reduction of phenol by ultrasound waves</b>

“…For sonication, many researchers have found the sonochemical degradation rate increases with decreasing solution pH [3,16]. In the present study, the ionic species of phenol is predominant when the pH exceeds 10.0 (equal to pK a value of phenol at 25 ºC), but the molecular species predominates when pH is less than the pK a .…”

Degradation of phenol by mechanical activation of a rutile catalyst

“…Consequently, this mechanism has been widely investigated during photocatalytic oxidation [22][23][24]51,46,53,62], oxidation with UV radiation and ozone [64] or hydrogen peroxide [65], sonocatalytic oxidation [25,26,[66][67][68][69], pulsed corona discharge degradation [32,41,70,71], and other advanced oxidation processes. Then, if some of the first intermediates of the reaction, i.e., hydroquinone, catechol, or benzoquinone, are identified in our case, this fact indicates that the Å OH radical, is involved in the degradation pathways.…”

Effects of dissolved gases and pH on sonolysis of 2,4-dichlorophenol

“…Many researchers have found that the sonochemical degradation rate decrease as the solution pH increases [23][24][25]. Lower pH leads to a more amount of the neutral form, represented by HA, which can enter into the cavitation bubble if it has a finite vapor pressure.…”