Degradation of CI Acid Orange 7 by ultrasound enhanced ozonation in a rectangular air-lift reactor

The combination of 20 kHz ultrasound and ozone for the degradation of C.I. Acid Orange 7 was studied. The effect of power density, gas flow rate, initial pH, hydroxyl radical scavenger, and initial dye concentration on the decolorization of C.I. Acid Orange 7 was investigated. The decolorization of C.I. Acid Orange 7 fits the pseudo-half-order kinetic model under most of the operating conditions. The decolorization rate increased with the increase of power density and gas flow rate, but decreased with the increasing initial dye concentration. Either pH or sodium chloride has little effect on the decolorization rate, indicating that the low frequency ultrasound enhanced ozonation process for the decolorization of C.I. Acid Orange 7 is mainly a direct reaction rather than radical reaction. Moreover, the decolorization rate increased with sodium carbonate to dye moalr ratio. The synergistic effect of C.I. Acid Orange 7 mineralization by ultrasound enhanced ozonation was significant when the system temperature was raised due to the heat effect of ultrasonic irradiation. (C) 2007 Elsevier B.V. All rights reserved.