The sonochemical decolorisation of textile azo dye CI Reactive Orange 127

In the present study, Fenton and sono-Fenton processes were applied to the oxidative decolorisation of synthetic textile wastewater including CI Reactive Orange 127 and polyvinyl alcohol. Process optimisation [pH, ferrous ion (Fe2+) and hydrogen peroxide (H2O2)], kinetic studies and their comparison were carried out for both of the processes. The sono-Fenton process was performed by indirect sonication in an ultrasonic water bath, which was operated at a fixed 35-kHz frequency and 80 W power. The optimum conditions were determined as [Fe2+] = 20 mg l−1, [H2O2] = 15 mg l−1 and pH = 3 for the Fenton process and [Fe2+] = 25 mg l−1, [H2O2] = 5 mg l−1 and pH = 3 for the sono-Fenton process. The colour removals were 89.9% and 91.8% by the Fenton and sono-Fenton processes, respectively. The highest decolorisation was achieved by the sono-Fenton process because of the production of some oxidising agents as a result of sonication. Consequently, ultrasonic irradiation in the sono-Fenton process slightly increased the colour removal to 91.8%, while decreasing the hydrogen peroxide dosage to one-third of that of the Fenton process.