Cobalt-Modified Biochar from Rape Straw as Persulfate Activator for Degradation of Antibiotic Metronidazole

A cobalt-loaded magnetic biochar (Co-MBC) catalyst was synthesized to enhance the removal of metronidazole (MNZ). Study explored the performance and mechanism of MNZ degradation by Co-MBC activated permonosulfate (PMS). Results showed that cobalt oxides were effectively deposited onto the biochar surface, new oxygen functional groups were added to the modified biochar, and the presence of the metallic element Co enhanced the efficiency of PMS activation in the composite. More than 90% of MNZ was removed after 60 min with a catalyst dosage of 0.2 g/L and a PS concentration of 1 mM. After four reuses, Co-MBC still showed excellent catalytic performance to degrade over 75% of MNZ. The reaction system performed well even in the presence of inorganic anions and organic macromolecules. However, the degradation rate was inhibited under alkaline conditions. The quenching experiment indicated that •SO4−, •OH, 1O2, and •O2− synergistically degraded MNZ, and that•SO4− played a dominant role. LC-MS was applied to assess intermediate degradation products, in which CO2, H2O, and NO3− were the final degradation products, and potential degradation pathways were suggested. In conclusion, Co-MBC was an efficient and stable catalytic material, and its ability to activate PMS was improved to effectively degrade antibiotics, a typical priority pollutant.