[Degradation of malachite green in aqueous solution by Fe3+/H2O2 catalyzed with EDTA]

This study found that the discolorization of malachite green solutions (0.01 mmol/L) was improved by Fe3+/H2O2 catalyzed with EDTA, at pH 7. Oxidation was carried out in presence of various hydrogen peroxide concentrations, in a wide range of temperature and EDTA concentration. It was found that oxidation with EDTA promoted the discolorization of MG from 43% to 98.3% as compared with the cases without EDTA. The discolorization of MG increased by 40% with the increase of EDTA concentration by 5 fold. The H2O2 concentration and temperature are higher, the discolorization of MG better, t-BuOH inhibited the improvement from EDTA. With the same total dosage of applied H2O2, the multiple steps addition did not show a much higher removal efficiency than that obtained by one step. OH free radical or an iron-oxo species may be the highly reactive oxidizing species, the latter may be the major oxidant. With the time, EDTA was a little oxidized.