MnFe2O4 decorated graphene as a heterogeneous catalyst for efficient degradation of di-n-butyl phthalate using catalytic ozonation in water

Abstract Magnetic, stable graphene-MnFe2O4 hybrids were synthesized by co-precipitation method for efficient degradation of di-n-butyl phthalate (DBP) using catalytic ozonation in water. The various synthesized catalysts were systematically characterized, and the catalytic activities in catalytic ozonation system were investigated. Moreover, a detailed mechanism of catalytic ozonation by synergistic function of graphene oxide (GO) and magnetic MnFe2O4 was proposed. Results showed that catalytic ozonation by 5-rGO-MFO-200 (MnFe2O4 calcined at 200°C after 5 wt% GO doped) could significant boost the DBP degradation, which illustrated by the apparent rate constant (k=0.0058) being nearly 4.2 times than that in ozone alone (k=0.0241). The increased activities of 5-rGO-MFO-200 for the catalytic ozonation was attributed to its rich concentration of surface hydroxyl sites (SHSC), better charge electron transfer ability, favorable lattice structure and nanoparticles diffusion in contrast to bare MnFe2O4. All catalysts presented good recycling and stability in the repeated batch experiment, and the removal efficiency of DBP only decreased 3% after 5 times. The radical quenching tests verified that hydroxyl radicals (·OH) was the dominant reactive oxygen species responsible for DBP degradation. Electrons cycling between Mn2+ and Mn3+ led to the decomposition of ozone to produce ·OH, which attacked DBP molecules to degrade into small molecular species and then further mineralized into CO2 and H2O. The synergistic function between magnetic MnFe2O4 and GO induced efficient ozone decomposition and more ·OH production.