Degradation of dibutyl phthalate by ozonation in the ultrasonic cavitation-rotational flow interaction coupled-field: performance and mechanism.

Abstract

Dibutyl phthalate (DBP) is present in hydraulic fracturing flowback and produced water. Degradation of DBP in aqueous by means of ozonation in ultrasonic cavitation-rotational flow interaction coupled-field (UC-RF coupled-field) was studied. The effect of ozone dosage, ozone intake flow, operating temperature, initial pH, DBP initial concentration, liquid flow rate, and ultrasonic power on the DBP removal was investigated. Results indicated that the DBP degradation rate was strongly influenced by the liquid flow rate and the ultrasonic power over the range investigated. HCO3- and Cl- revealed an inhibitory effect on the DBP removal. SO42- seemed to have no effect on DBP removal. The ozone utilization efficiencies in the UC-RF coupled-field were 2.77 and 1.13 times higher than those in the conventional microporous aeration (CMA) and rotating-flow microbubble aeration (RFMA), respectively. The DBP degradation rate was diminished in the presence of tert-butyl alcohol. Cavitation bubbles are considered as innumerable microreactors. Degradation of DBP by direct ozonation, hydroxyl radical (·OH) oxidation, high pressure, and high-temperature pyrolysis was demonstrated. Finally, a possible degradation pathway of DBP is obtained on the basis of the main reaction intermediates.