摘要：

Pollutant degradation via periodate ( \({ext{IO}}_{4}^{-}\) ) and transitional metal oxides provides an economical, energy-efficient way for chemical oxidation process in environmental remediation. However, catalytic activation of periodate by manganese dioxide and the associated mechanism were barely investigated. In this study, four MnO 2 polymorphs (α-, β-, γ- and δ-MnO 2 ) were synthesized and tested to activate \({ext{IO}}_{4}^{-}\) for the degradation of sulfamethoxazole (SMX). The reactivity of different MnO 2 structures followed the order of α-MnO 2 >β-MnO 2 >γ-MnO 2 >δ-MnO 2 , suggesting that the particular crystalline structure in α-MnO 2 would exhibit higher activities via \({ext{IO}}_{4}^{-}\) activation. Herein, in α-MnO 2 / \({ext{IO}}_{4}^{-}\) system, 91.1% of SMX was eliminated within 30min with degradation rate constant of 0.0649min 1 , and the neutral pH exhibited higher efficiency in SMX degradation compared with acidic and alkaline conditions. Singlet oxygen ( 1 O 2 ) was unveiled to be the dominant ROS according to the results of electron paramagnetic resonance, chemical probes and radical quenching experiments, whereas \({\mathrm{O}}_{2}^{\bullet -}\) and OH were mainly acted as a free-radical precursor. Six oxidation products were identified by LC–MS, and the elimination of sulfonamide bond, hydroxylation and direct oxidation were found to be the important oxidation pathways. The study dedicates to the mechanistic study into periodate activation over alpha-MnO 2 and provides a novel catalytic activation for selective removal in aqueous contaminants.

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