Ozonalytic kinetic order of dye decoloration in aqueous solution

The intrinsic kinetic order of reaction between a dye (Acid Blue 9) and dissolved ozone in aqueous phase was measured by a pulse-ejection microreactor (PEMR) in this research. The reaction orders and reaction rate constants were evaluated by the variation of initial slope method, the half-life method, and the general order equation. Results of this study indicated that the commonly literature-cited pseudo-first-order may not be suitable for all ozonation conditions. The pseudo-first-order was only valid with an ozone to dye molar ratio (Z) between 5.57 and 9.31. When the value of Z increased from 13.91 to 30.83, the reaction order increased rapidly from 1.03 to 1.76. On the other hand, when the value of Z was smaller than 1.74, the reaction order seemed closer to zero order. Furthermore, the reaction order may not be constant throughout the treatment process. It might vary with variation of ozone to dye ratio as the reaction is proceeding.