Facet-engineered activation of peracetic acid by α-MnO2 for chlortetracycline wastewater decontamination: Oxygen vacancy-induced electron transfer

Remediation of antibiotic contamination by manganese oxides via peracetic acid (PAA) activation is an emerging wastewater treatment process. However, the role of exposed facets of manganese oxides in PAA activation and the corresponding activation mechanism remain to be understood. In this work, highly active alpha-MnO2 was selected as a typical manganese oxide, and alpha-MnO2 with {100}, {110} and {310} facets were synthesized via facet engineering. The degradation performance of different facets of alpha-MnO2 in the PAA activation system towards chlortetracycline (CTC) was compared. The results suggested that the {310} facet exhibited the highest catalytic activity, with 96.20 % of CTC being degraded within 30 min, which was better than the {100} (81.06 %) and {110} (65.39 %) facets. Besides, the {310} facet exhibited superior anti-interference to inorganic anions and complex water matrices in the degradation of CTC. The identification of active species and active sites confirmed that the electron transfer process induced by the active complex---Mn(II)-PAA* formed by the PAA bond with the reactive Mn(II) on the alpha-MnO2 surface is the main contributor to CTC degradation. Characterization and density functional theory calculations jointly revealed that the oxygen vacancy density otherness caused by the difference in atomic arrangement is the facet-dependent PAA activation mechanism. This work provides a new approach for designing efficient PAA activation catalysts and their application in antibiotic wastewater purification.