Drastically enhanced ultrasonic decolorization of methyl orange by adding CCl4

Effects of CCl4 were investigated on the ultrasonic decolorization of azo dye methyl orange (MO). The decolorization of MO was observed to behave as a pseudo-first reaction in kinetics under all the conditions tested in the present work. The apparent rate constant of the decolorization was demonstrated to be dependent on CCl4 concentration, MO concentration and the solution pH value. Under appropriate conditions, the rate constant of the ultrasonic decolorization of MO was able to be increased more than 100 times by adding CCl4 into the MO solution. A reaction mechanism was proposed to explain the promoting effect of CCl4 on the ultrasonic decolorization of MO, which was attributed to the generation of highly-oxidizing such as Cl radical and HClO species, and then their attack at the azo bond of MO.