Effects of Operational Conditions on 1,4-Dioxane Degradation by Combined Use of Ultrasound and Ozone Microbubbles

1,4-Dioxane is regarded as a priority pollutant because it is hardly degraded by conventional methods of wastewater treatment. In this study, the degradation of 1,4-dioxane in water by the combined use of ultrasound and ozone microbubbles has been investigated. 1,4-Dioxane degradation by ultrasound and/or ozone followed a first-order reaction kinetics. The reaction constant for ozone microbubbles was higher than that for ozone millibubbles. The synergistic effect on reaction constant has been observed by the combined use of ultrasound and ozone microbubbles. The effect of hydroxyl radicals on reaction has also been investigated. Compared with the direct reactions of ultrasound and ozone, hydroxyl radicals play a major role in 1,4-dioxane degradation. The synergistic effect is enhanced with increasing ultrasonic input power and ozone concentration. Empirical equations of the relationships between ultrasonic input power, ozone concentration, and reaction rate constant have been established. (C) 2012 The Japan Society of Applied Physics