Synthesis of Fe-Loaded Biochar Obtained from Rape Straw for Enhanced Degradation of Emerging Contaminant Antibiotic Metronidazole

In this study, magnetic (Fe)-loaded biochar was successfully prepared by a simple impregnation pyrolysis method. Meanwhile, its degradation capability and mechanism for typical antibiotic metronidazole (MNZ) were systematically investigated under different conditions. The characterization of the synthesized material showed that the specific surface area, pore diameter, and pore volume changed significantly. Also, functional groups and metal element Fe were introduced on the surface of the biochar, leading to its better capability to activate peroxymonosulfate (PMS). The degradation experiments showed that the removal of MNZ in the Fe-BC/PMS system can reach up to 95.3% in 60 min under optimal conditions. Free-radical capture experiments showed that there were several active species of •OH, SO4•−, •O2−, and 1O2 present in the catalyst to synergistically degrade MNZ, among which SO4•− played a major role; it was also found that the material can be easily recycled and was still effective after several uses. Further, the main degradation pathways of MNZ include nitrohydroxylation, hydroxyethyl functional group deletion, carboxylation of the amino functional group of •OH, demethylation, oxidation, and carboxylation. It is obvious that the synthesized magnetic-loaded biochar, Fe-BC, generated from waste rape straw crops, shows high catalytic performance in pollutant degradation, providing an insight into the recycling potential of waste biomass in the catalytic field for pollutant removal.