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 λmax = 592 nm. 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 SO4−2 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.