Permanganate activation with Mn oxides at different oxidation states: Insight into the surface-promoted electron transfer mechanism

Lu Ma; Wenqiang Gong; Qinghong Wu; Xiong Zhou; Shuaiqi Zhao; Aimal Khan; Xiaoxia Li; Aihua Xu

doi:10.1016/j.jhazmat.2023.131746

Permanganate activation with Mn oxides at different oxidation states: Insight into the surface-promoted electron transfer mechanism

J Hazard Mater. 2023 Sep 5:457:131746. doi: 10.1016/j.jhazmat.2023.131746. Epub 2023 May 30.

Authors

Lu Ma¹, Wenqiang Gong², Qinghong Wu², Xiong Zhou², Shuaiqi Zhao², Aimal Khan², Xiaoxia Li², Aihua Xu³

Affiliations

¹ School of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430200, PR China; Hubei Key Laboratory of Biomass Fibers and Eco-Dyeing & Finishing, Wuhan Textile University, Wuhan 430200, PR China.
² School of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430200, PR China.
³ School of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430200, PR China; Hubei Key Laboratory of Biomass Fibers and Eco-Dyeing & Finishing, Wuhan Textile University, Wuhan 430200, PR China. Electronic address: xahspinel@sina.com.

PMID: 37270959
DOI: 10.1016/j.jhazmat.2023.131746

Abstract

The development of new strategies to improve the removal of organic pollutants with permanganate (KMnO₄) is a hot topic in water treatment. While Mn oxides have been extensively used in Advanced Oxidation Processes through an electron transfer mechanism, the field of KMnO₄ activation remains relatively unexplored. Interestingly, this study has discovered that Mn oxides with high oxidation states including γ-MnOOH, α-Mn₂O₃ and α-MnO₂, exhibited excellent performance to degrade phenols and antibiotics in the presence of KMnO₄. The MnO₄^- species initially formed stable complexes with the surface Mn(III/IV) species and showed an increased oxidation potential and electron transfer reactivity, caused by the electron-withdrawing capacity of the Mn species acting as Lewis acids. Conversely, for MnO and γ-Mn₃O₄ with Mn(II) species, they reacted with KMnO₄ to produce cMnO₂ with very low activity for phenol degradation. The direct electron transfer mechanism in α-MnO₂/KMnO₄ system was further confirmed through the inhibiting effect of acetonitrile and the galvanic oxidation process. Moreover, the adaptability and reusability of α-MnO₂ in complicated waters indicated its potential for application in water treatment. Overall, the findings shed light on the development of Mn-based catalysts for organic pollutants degradation via KMnO₄ activation and understanding of the surface-promoted mechanism.

Keywords: Electron transfer; Mn oxides; Oxidation states; Permanganate; Surface-promoted mechanism.