Efficient decolorization of Malachite Green in the Fenton reaction catalyzed by [Fe(III)-salen]Cl complex

The catalysis effect of [Fe(III)-salen]Cl complex on the decolorization and degradation of Malachite Green in the Fenton system was investigated in this study. A significant decolorization enhancement was observed in the presence of only trace amount of the complex without additional equipment or external energy. The effects of reaction parameters were studied and the results showed that the increase of [Fe(III)-salen]Cl complex, molar ratio of salen ligand to Fe(III) and initial concentration of H2O2 favor the increase of decolorization rate. The increase of initial concentration of the dye leads to the decrease of decolorization rate and the optimum pH was the original pH of Malachite Green solution. Under the optimal condition, the decolorization and TOC removal rates after 24 min treatment were 97.94% and 54.35% respectively. Hydroxyl radical was identified as the main active oxidant species in the [Fe(III)-salen]Cl complex catalyzed Fenton system. The degradation intermediates of Malachite Green were analyzed and a possible reaction mechanism was proposed. The decolorization of Malachite Green obeyed the pseudo-first order equation and the activation energy was calculated by the related kinetic constants, which was only 49.13% of Fe(III) Fenton system.

• Fe(III)-salenCl complex was successfully used in the treatment of Malachite Green. • 3.5 folds reaction speed and a little higher decolorization rate were obtained. • Main active oxidation specie was confirmed and the reaction mechanism was deduced. • The decolorization of Malachite Green obeyed the pseudo-first order kinetics. • The pseudo-activated energy was calculated and compared.