Catalysed ozonation for removal of an endocrine-disrupting compound using the O3/Fenton reagents system

Abstract

Aqueous solutions of diethyl phthalate (DEP) were oxidized by using ozone combined with Fenton reagents. The effects of operating parameters such as initial pH; initial concentration of DEP, H2O2 and Fe2+; [H2O2]0/[Fe2+]0 ratio and O3 dosage on the degradation rates of DEP were investigated. The results showed that DEP degradation is strongly dependant on the pH; initial concentrations of the phthalate, H2O2 and Fe2+; [H2O2]0/[Fe2+]0 ratio and O3 dosage. The addition of H2O2 and Fe2+ ions was effective to achieve almost 98% degradation of 200 mg L−1 of DEP in about 40 min using a dose of O3 = 45 g m−3 NTP; [H2O2]0 = 2.5 × 10−2 mol L−1 and [Fe(II)]0 = 5 × 10−3 mol L−1, as compared to over 60 min by using O3 and Fenton processes applied separately. DEP degradation followed apparent pseudo-first-order kinetics under ozonation, Fenton's reagents oxidation and the combined ozonation/Fenton reagents oxidation process. The overall reaction rates were significantly enhanced in the O3/Fe2+/H2O2 oxidation system, and allows achieving 100% degradation of DEP (100 mg L−1) in 30 min of reaction time. The notable decrease in DEP removal rate observed in the presence of a radical scavenger indicates that there was an obvious synergetic effect in the combined ozonation/Fenton reagent process most likely because ozonation could accelerate Fenton reagents to generate hydroxyl radical HO•. Thus, the reaction between DEP and HO• proceeds mainly in the bulk of the aqueous phase. Under optimal conditions, the O3/Fe2+/H2O2 system oxidation was the most effective in DEP removal in water.