Silver(I) catalyzed oxidation kinetics of the crystal violet dye by peroxydisulfate in aqueous and micellar media

Hameed, Salem A; Hameed, Salem A; Ewais, Hassan A

Abstract

The kinetics of the oxidative decolcorization of crystal violet (CV+) as a cationic dye by peroxydisulfate using silver(I) catalyst in aqueous acidic medium were studied. The effects of different parameters like hydrogen ion, silver(I), reactants concentration, micelles and temperatures were investigated. The reaction between [CV]+ and persulfate was investigated under pseudo-first-order kinetics by taking a large excess of [S2O82-] over [CV+]. A plausible mechanism for the silver(I) enhanced decolcorization of [CV]+ by persulfate is suggested and rate law obeyed the following equation:

Rate = (k2 +     k3[Ag+])  [CV+] [S2O82-]

The effect of surfactant micelles such as SDS and Triton X-100 on the reaction rate is investigated. The rate of reaction decreases with increasing [SDS] but had no effect with Triton X-100. Heats of activation DH* and DS* were calculated. An outer-sphere process for the electron transfer is the proposed mechanism for this reaction.


Keyword(s)

Crystal violet, Catalysis by silver(I), Oxidative decolcorization, Outer-sphere mechanism, Pseudo phase model


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