Reactive dyestuff degradation by combined sonolysis and ozonation

The degradation of a reactive dye by combined sonolysis (520 kHz) and ozonation was studied using C.I. Reactive Black 5 as a model dye. It was found that the joint action of ultrasound and ozone induced a synergistic effect on both the decolorization of the dye and the overall degradation process. Due to the inefficiency of ultrasonic irradiation by itself to render any significant degradation under the conditions employed, the synergy was attributed mainly to mechanical effects of ultrasound to enhance the mass transfer of ozone in solution. The radical chain reactions taking place during thermolysis of water and ozone in collapsing cavities may also have contributed chemically to the synergy by providing additional decomposition pathways for ozone, and an excess of electron-deficient chemicals in solution.