Elevated removal of di-n-butyl phthalate by catalytic ozonation over magnetic Mn-doped ferrospinel ZnFe2O4 materials: Efficiency and mechanism

Abstract

Magnetic Mn-doped ZnFe2O4 (MnxZn1-xFe2O4, x = 0, 0.2, 0.5, 0.8) were synthesized by a sol-gel method at different calcination temperature (400 °C, 500 °C, 600 °C). The as-synthesized MnxZn1-xFe2O4 were systematically characterized and evaluated as heterogeneous catalysts for the ozonation of di-n-butyl phthalate (DBP) degradation in water. Importantly, a detailed mechanism of catalytic ozonation occurring on the surface of MnxZn1-xFe2O4 was proposed. The results showed that Mn0.5Zn0.5Fe2O4 calcined at 500 °C (500-Z0.5) could greatly enhance the degradation of DBP in the presence of ozone, which indicated by the first-order kinetic constant (k = 0.086 min−1) being approximately 5.73 times than that in the ozone alone (k = 0.015 min−1) system. The improved activity of 500-Z0.5 for the catalytic ozonation was attributed to its rich active sites of surface hydroxyl groups, better electron transfer ability, and more Mn2+ content. All catalysts presented favorable recycling and stability in the repeated batch experiment. In situ Raman spectroscopy and the radical quenching tests verified that hydroxyl radical (OH) was the primary radical species responsible for DBP degradation. A synergistic function between Mn, Zn and oxygen ensured efficient ozone decomposition and more OH generation.