Degradation of C.I. Direct Black 168 from aqueous solution by fly ash/H2O2 combining ultrasound

Degradation of C.I. Direct Black 168 from aqueous solution using Fenton-like reactions combining ultrasound was investigated. In the presence of H2O2, the effect of the heterogeneous catalysts, such as fly ash, kaolinite or diatomaceous earth on the degradation of Direct Black 168 was observed under ultrasound. The fly ash was the most efficient catalyst. It is apparent that ultrasound can prompt the reaction to take place and give in higher degradation. In the combination of ultrasound and fly ash/H2O2, the effect of different system variables namely concentration of the dye, dosage of fly ash, concentration of H2O2, pH of solution and the addition of NaCl were studied. 99.0% removal ratio was achieved at initial concentration 100 mg/L, pH 3.0, and dosage of fly ash 2.0 g/L, as well as 2.94 mM H2O2. NaCl exhibited only a minor effect on the dye removal.