The degradation of a reactive azo dye, Direct Red 81 (DR81), by Fenton process and in conjunction with sonolysis (SonoFenton) was studied. The synergistic effect of Fenton process and sonolysis enhanced the degradation of Direct Red 81 in aqueous solutions and the reaction followed the mechanism of hydroxyl radical (HO) oxidation. The influence of the initial substrate concentration, pH and catalyst loading on the rate of decolorisation were studied. The dye decolorisation followed apparent first order kinetics. The optimum conditions for decolorisation were pH=3.0, [Fe(2+)]=0.2 g/l, [H2O2]=5.1×10(-3) mol/l and ultrasonic frequency=120 kHz, 60 W. These conditions yielded 99% decolorisation of DR81 within 75 min. The sonolytic degradation products of DR81 were identified using Electrospray Ionization-Mass Spectrometry (ESI-MS). The presence of CO3(2-), HCO3(-), Cl(-), NO3(-), and SO4(2-) ions in the dye solution did not have a considerable effect on the decolorisation efficiency. This study demonstrates that Fenton and SonoFenton methods can effectively decolorize DR81 dye in waste water. The dye concentration used in this study is higher compared to earlier studies illustrating the effective mineralization by the SonoFenton process. The mechanism of dye degradation is also proposed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.