Synergistic effects of ultrasonic-assisted ozonation on the formation of hydrogen peroxide

Abstract Ultrasonic (US) - assisted ozonation process is an efficient way to enhance the mineralization of organic pollutants in water treatment, in which radical-mediated chain reactions from the ozone (O3) initiation and propagation are enhanced by ultrasonic irradiation. In this work, the evolution and dissociation of H2O2 under different initial pH, in the presence of different active oxidation species scavengers were investigated in the ultrasonic-assisted ozonation process. Variation of H2O2 concentration in ultrapure water, reverse osmosis water, tap water and seawater was also explored. The results showed that HO2¯ was involved in the initiation and propagation of ozone decomposition, and the synergistic effect of ultrasonic irradiation promoted the generation of H2O2 by 54.8%. More than 90% of H2O2 was largely inhibited by the addition of •OH and •O2¯ scavengers, indicating that the primary work of H2O2 generation did not directly involved ozone irradiation by ultrasound. In reverse osmosis treated water, the moderate organic predecessors (0.08 mg/L TOC) promoted H2O2 generation by 26% in O3 process and 29% in O3+US process. This study investigated factors that influence H2O2 evolution during ultrasonic ozonation, leading to methods for enhancing the transformation of ozone and producing hydroxyl radical during water treatment.