Promoted permanganate activation by nano TiO2 as Lewis acid catalysts for efficient degradation of levofloxacin

The heterogeneous activation of permanganate (KMnO 4 ) with redox or non-redox metal oxides to degrade toxic pollutants in aqueous solution has garnered increased attention recently. However, how Lewis acid (LA) site in metal oxides interacts with KMnO 4 to enhance its reactivity remains unclear. To clarify the mechanism of KMnO 4 activation with LA catalysts, the degradation of levofloxacin (LEVO) by KMnO 4 with titanium dioxide (TiO 2 ), a water-resistant solid acid catalyst, was investigated in this study. An improved degradation efficiency, a low activation energy of 25.2 kJ/Mol, and a high KMnO 4 utilization of 61.6% were observed with KMnO 4 /TiO 2 system, compared with KMnO 4 alone. The presence of strong Lewis acidity on TiO 2 surface was confirmed by various technologies, and the density functional theory calculation and electrochemical experiments further revealed that the coordinatively unsaturated Ti 4+ species interacted with KMnO 4 as LA sites to stretch its Mn O bonds and increase its oxidation potential, thereby achieving a high electron transfer reactivity. The system also showed high adaptability under various conditions including recycling experiments, treatment of several pollutants and various solution pH, and a decreased toxicity of the products. These findings provided an improved understanding of LA sites in KMnO 4 activation and its application to degrade pollutants • The degradation rate of LEVO via KMnO 4 activation was increased 9.7 times with TiO 2 . • A high KMnO 4 utilization of 61.6% was observed with KMnO 4 /TiO 2 system. • The oxidation potential and electron transfer reactivity of KMnO 4 increased • The role of TiO 2 as LA catalysts for KMnO 4 activation was demonstrated by DFT. • The decreased toxicity of the intermediate products was observed with the system.