Reactive complexes mediated singlet oxygen production by MnO2 catalyzed peracetic acid: Characterization and DFT study

Advanced oxidation technology based on peracetic acid (PAA) has been a hot issue in the remediation of refractory organic pollutants. Here, we investigated manganese dioxide (alpha-MnO2) effectively activate the in-situ generated PAA by rapid perhydrolysis of sodium percarbonate (SPC) and tetraacetylethylenediamine (TAED) to degrade sulfamethoxazole (SMX). This system followed non-radical pathway only dominated by singlet oxygen (1O2), which can exhibit excellent anti-interference capacity. The generation of metastable manganese intermediates (Mn-PAA*) is a key step in the formation of 1O2. The formation of Mn-PAA* is confirmed by electrochemical and in-situ Raman tests. With the help of density functional theory (DFT), we have probed the behavior of PAA activation on different crystal planes to produce 1O2, with O-H cleavage to generate MnIV- OOOCCH3 being the decisive step for the formation of 1O2. This study is the first to investigate the mechanism of non-radical mediated PAA activation by alpha-MnO2 and in-depth research the role of Mn-PAA* in the 1O2 generation. The proposed new insights into non-radical process of PAA activation by transition metal will further advance the application of PAA-based AOPs.