Fenton degradation of malachite green catalyzed by aromatic additives

Fenton degradation of malachite green (MG) catalyzed by various kinds of aromatic additives was examined. It was found that the aromatic additives exhibited catalysis immediately or after an induction period to accelerate the MG degradation in the Fenton reaction. EPR, GC-MS, and redox potential measurements were employed to obtain details of the reaction process. A reaction mechanism is proposed for the interaction between Fenton reagents (Fe2+/Fe3+, H2O2) and the aromatic compounds, which involves the generation and redox cycle of hydroquinone-like intermediates in the Fenton reaction. The Fenton reaction rates of MG after addition of various kinds of aromatic additives were. in the following order: hydroquinone > salicylic acid > p-hydroxylbenzoic acid > m-hydroxylbenzoic acid > p-benzoquinone > carboxylic aromatics > amido aromatics, which is also quite consistent with their ability to be transformed into hydroquinone-like compounds. Hydroquinone-like compounds can react with ferric ions to regenerate ferrous ions and are regenerated continuously from quinone or semiquinone by reacting with HO2. which accelerates the Fenton reaction.