Decolorization of reactive orange 16 via ferrate(VI) oxidation assisted by sonication

Abstract

The decolorization of azo dye C.I. reactive orange 16 (RO 16) via ferrate(VI) and sono-ferrate(VI) methods, which is the combination of the ferrate(VI) oxidation method with sonication, has been achieved in the present study. The influences of some important operating parameters, which are the initial pH, the concentration of potassium ferrate(VI) (K$_{2}$FeO$_{4})$ and the RO 16 dye, and ultrasonic density (for only the sono-ferrate(VI) method), on the color removal have been investigated. The optimum conditions have been determined as pH = 7 and [K$_{2}$FeO$_{4}$] = 50 mg L$^{-1}$ for the individual ferrate(VI) oxidation method and pH = 7 and [K$_{2}$FeO$_{4}$] = 50 mg L$^{-1}$ by direct sonication at 0.50 W mL$^{-1}$ ultrasonic density and 20 kHz fixed frequency for the sono-ferrate(VI) method. The color removal efficiencies were 85% by ferrate(VI) method and 91% by sono-ferrate(VI) method. Kinetic studies were also performed for the decolorization of RO 16 under the optimized conditions at room temperature. It was seen that the oxidative decolorization of RO 16 via the sono-ferrate(VI) method happened more rapidly because of the production of OH$^{\bullet }$ radical through sonication compared to the individual ferrate(VI) method.