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

epsilon-MnO2 effectively activates peroxymonosulfate (PMS) for the efficient degradation of emerging pollutants. epsilon-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. epsilon-MnO2 was found to activate PMS more efficiently than alpha-MnO2, beta-MnO2, or delta-MnO2, owing to its high - OH-group content, unique structure, and high surface area. Sulfate (SO4 center dot), hydroxyl (center dot OH), and superoxide (O-2(center dot)) radicals, as well as singlet oxygen (O-1(2)) were generated, with O-2(center dot) acting as the O-1(2) precursor. The epsilon-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 epsilon-MnO2 includes inner-sphere interactions between epsilon-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. (C) 2021 Published by Elsevier Inc.

Automated summary

epsilon-MnO2 efficiently activates peroxymonosulfate (PMS) for the degradation of emerging pollutants, generating sulfate, hydroxyl, superoxide, and singlet oxygen radicals. The system is effective in a wide pH range and the degradation of pollutants is not significantly influenced by the presence of inorganic anions or natural organic matter. The proposed activation pathway involves inner-sphere interactions and electron transfer, leading to the generation of reactive oxygen species.