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

摘要

The kinetics of the oxidative decolorization of Reactive Blue dye (C.I.19) (RB-19) with KBrO_3 acidified by both the H_2SO_4 and cation-exchange resins (H~+-form) were followed up by monitoring the decrease of the absorbance of RB-19 at lambda_(max)=592 nm.In homogenous medium,the reaction was carried out under pseudo-first-order conditions.The [BrO_3~-] was ca 600 greater than that of [RB-19].The rate of reaction increased with decreasing [H_2SO_4] and [BrO_3~-],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 [SO_4~(2-)].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.