Peroxymonosulfate activation by Co-doped magnetic Mn 3 O 4 for degradation of oxytetracycline in water.

Co-doped magnetic Mn ₃ O ₄ was synthesized by the solvothermal method and adopted as an effective catalyst for the degradation of oxytetracycline (OTC) in water. Synergistic interactions between Co-Mn ₃ O ₄ and Fe ₃ O ₄ not only resulted in the enhanced catalytic activity through the activation of peroxymonosulfate (PMS) to degrade OTC but also made Fe ₃ O ₄ /Co-Mn ₃ O ₄ easy to be separated and recovered from aqueous solution. 94.2% of OTC could be degraded within 60 min at an initial OTC concentration of 10 mg L ^-1 , catalyst dosage of 0.2 g L ^-1 , and PMS concentration of 10 mM. The high efficiency of OTC removal was achieved in a wider pH range of 3.0-10.0. Co (II), Co (III), Fe (II), Fe (III), Mn (II), Mn (III), and Mn (IV) on Fe ₃ O ₄ /Co-Mn ₃ O ₄ were identified as catalytic sites based on XPS analysis. The free radical quenching experiments showed that O ₂ ^•- radicals and ¹ O ₂ played the main role in the degradation process and the catalytic degradation of OTC involved both free radical and non-free radical reactions. Eventually, the intermediates of OTC degradation were examined, and the possible decomposition pathways were proposed. The excellent catalytic performances of Fe ₃ O ₄ /Co-Mn ₃ O ₄ came from the fact that the large specific surface area could provide abundant active sites for the activation of PMS and the redistribution of inter-atomic charges accelerated the redox reactions of metal ions. The high degradation efficiency and rate constant of OTC in actual water samples indicated that Fe ₃ O ₄ /Co-Mn ₃ O ₄ had a good practical application potential.
(© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)