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

ε-MnO2 effectively activates peroxymonosulfate (PMS) for the efficient degradation of emerging pollutants. ε-MnO2 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-MnO2 was found to activate PMS more efficiently than α-MnO2, β-MnO2, or δ-MnO2, owing to its high - OH-group content, unique structure, and high surface area. Sulfate (SO4•-), hydroxyl (•OH), and superoxide (O2•-) radicals, as well as singlet oxygen (1O2) were generated, with O2•- acting as the 1O2 precursor. The ε-MnO2/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-MnO2 includes inner-sphere interactions between ε-MnO2 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.