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

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 degrees C, 500 degrees C, 600 degrees 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 MnxZn1-xFe2O4 calcined at 500 degrees C (500-Z(0.5)) 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-Z(0.5) 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)-O-center dot) was the primary radical species responsible for DBP degradation. A synergistic function between Mn, Zn and oxygen ensured efficient ozone decomposition and more (OH)-O-center dot generation.