Kinetics of the oxidative decolorization of Reactive Blue-19 by acidic bromate in homogeneous and heterogeneous media

The kinetics of the oxidative decolorization of Reactive Blue dye (C.I.19) (RB-19) with KBrO3 acidified by both the H2SO4 and cation-exchange resins (H+-form) were followed up by monitoring the decrease of the absorbance of RB-19 at lambda(max) = 592 run. In homogenous medium, the reaction was carried out under pseudo-first-order conditions. The [BrO3-] was ca 600 greater than that of [RB-19]. The rate of reaction increased with decreasing [H2SO4] and [BrO3-], while it decreased with increasing [RB-19]. The effects of the ions, Cl-, Br, Mo(IV), and So(4)(-2) were investigated and the reaction rate increased with increasing concentrations of the former three, while it decreased with increasing [SO42-] In heterogeneous medium the reaction exhibited the zero-order kinetics with respect to [RB-19]. The homogeneous system gave a higher rate compared with the heterogeneous one. The reaction is entropy controlled. A reaction mechanism has been proposed. (c) 2005 Elsevier Ltd. All rights reserved.