Catalytic oxidation kinetics and mechanisms of commercial dyes by H2O2/iron powder system

The oxidation kinetics and mechanisms of commercial dyes by H202 and iron powder system were investigated in a well-mixed batch reactor. The three dyes studied are Reactive Red 120, Direct Blue 160 and Acid Blue 40. There are three major processes involved in the oxidation: iron powder dissolution to Fe2+, dye adsorption by iron powder and dye oxidation by Fenton\u27s reagent. Dissolution of iron powder was the initial step of adsorption and oxidation of the dyes. Dye adsorption obeyed the Langmuir adsorption isotherm. Both dissolution and adsorption were favorable at pH 2.0 to 2.5. Oxidation by Fenton\u27s reagent was the major process contributed to decolorization. The optimal pH ranged from 3.0 to 3.5. The optimal ratio of H202 to iron metal was 0.001 M to 1.0 g/L. The initial oxidation rate followed pseudo-first-order kinetics. The mechanisms of iron dissolution, dye adsorption and oxidation were proposed in order to explain the experimental phenomena