Facile-prepared Fe/Mn co-doped biochar is an efficient catalyst for mediating the degradation of aqueous ibuprofen via catalytic ozonation

The fabrication of efficient, stable, and low-cost catalysts is crucially important for the catalytic ozonation process for the removal of recalcitrant pollutants. In this study, we present a facile impregnation-pyrolysis method for the preparation of novel porous Fe/Mn co-doped biochar (Fe-Mn-C) with excellent catalytic activity and reusability for the catalytic ozonation of ibuprofen (IBP). The incorporation of Fe/Mn heteroatoms into the carbon skeleton of biochar not only produced more defective sites and promoted the charge transfer on the materials surface but also created active Fe/Mn species with multi-valence states for ozone activation. As a result, >95% of IBP (50 mg/L) and 80.5% of total organic carbon can be rapidly removed within 9 min in the Fe-Mn-C/O3 process at a pH of 7, ozone dosage of 4.93 mg/min, and Fe-Mn-C dosage of 0.5 g/L. The catalytic reaction rate in Fe-Mn-C/O3 was 6.58 times higher than that of sole ozonation and 2.3–4.1 times higher than that of catalytic ozonation with other catalysts (e.g., biochar, Fe-doped biochar, Mn-doped biochar, activated carbon, Fe3O4 and MnO2). Moreover, the obtained Fe-Mn-C can be reused for multiple cycles; the performance is not significantly reduced in subsequent cycles, and there is no significant metal leaching. Further studies suggested that the radical pathways (superoxide radicals and hydroxyl radicals) were mainly responsible for the degradation of IBP in the Fe-Mn-C/O3 system. Furthermore, the contributions of the surface functional groups, doped atoms, and delocalized π electrons of Fe-Mn-C to the decomposition of ozone and the formation of reactive species were identified by correlation analysis between the catalytic ozonation rate and the physiochemical properties of Fe-Mn-C to clarify the mechanism underlying the improved performance.