Degradation of antibiotics in aqueous media using manganese nanocatalyst-activated peroxymonosulfate

ε-MnO 2 effectively activates peroxymonosulfate (PMS) for the efficient degradation of emerging pollutants. ε-MnO 2 was synthesized by a facile thermal-treatment method and its long-term stability and efficiency for the elimination of emerging pollutants, including sulfamethoxazole (SMX), sulfachloropyridazine (SCP), sulfamethazine (SMT), ciprofloxacin (CIP), and azithromycin (AZI), from aqueous media were evaluated. ε-MnO 2 was found to activate PMS more efficiently than α-MnO 2 , β-MnO 2 , or δ-MnO 2 , owing to its high − OH-group content, unique structure, and high surface area. Sulfate (SO 4 •− ), hydroxyl (•OH), and superoxide (O 2 •− ) radicals, as well as singlet oxygen ( 1 O 2 ) were generated, with O 2 •− acting as the 1 O 2 precursor. The ε-MnO 2 /PMS system proved to be effective in the pH range of 3.5–9.0 and the rate of SMX degradation was not significantly affected by the presence of inorganic anions or natural organic matter. The proposed pathway for the activation of PMS by ε-MnO 2 includes inner-sphere interactions between ε-MnO 2 and PMS, and electron transfer to PMS via the MnIII ↔ MnIV redox cycle, which generates reactive oxygen species. These findings provide new insight into PMS activation by less-toxic metal oxides as catalysts and demonstrate that Mn-based materials can be used to effectively treat water matrices containing emerging pollutants.