Kinetics of Oxidation of Triaryl Methane Dye, Brilliant Blue-R with Chlorine Dioxide

The fast decolourization of multi-purpose dye, Brilliant blue (BB-) oxidized by chlorine dioxide was investigated using the stopped flow technique under varied pH conditions by monitoring its oxidation kinetics. The products were identified and reaction mechanism is described, which is confirmed by kinetic simulations. Under [ClO2]0 > [OH-]0 > [BB-]0 conditions, the oxidation kinetics showed first-order dependence on BB- and chlorine dioxide. The overall second-order rate coefficient enhanced with increasing pH, and values were 30.2 ± 0.2 M-1 s-1,42.5 ± 0.8 M-1 s-1 and 117.9 ± 0.8 M-1 s-1 at pH 7.0,8.0 and 9.0, respectively. In the pH range 7.0 to 9.0, the catalytic constant for [OH-] catalyzed reaction was 9.0 X 106 M-2 s-1 with energy of activation of 50.06 kJ mol-1. Observed negative entropy of activation of -658.73 J K-1 mol-1 suggests the formation a compact transient activated complex.