New Insights into the Combination of Permanganate and Bisulfite as a Novel Advanced Oxidation Process: Importance of High Valent Manganese-Oxo Species and Sulfate Radical
2019
Gao, Yuan | Zhou, Yang | Pang, Su-Yan | Jiang, Jin | Yang, Zhifeng | Shen, Yongming | Wang, Zhen | Wang, Pan-Xin | Wang, Li-Hong
Recently, it has been reported that the combination of permanganate (Mn(VII)) and bisulfite can lead to a rapid degradation of organic contaminants, where soluble Mn(III) is proposed to be responsible. Interestingly, in this work, we demonstrated the involvement of high-valent Mn-oxo species (possibly Mn(V)) as well as sulfate radical in the Mn(VII)/bisulfite system, by using methyl phenyl sulfoxide (PMSO) as a chemical probe. It was found that the combination of Mn(VII) and bisulfite resulted in appreciable degradation of PMSO under various conditions, while negligible PMSO was degraded by manganese dioxide (MnO₂) in the presence of bisulfite under similar conditions. This result indicated that Mn(III) intermediate formed in situ in both Mn(VII)/bisulfite and MnO₂/bisulfite systems as proposed in literature exhibited sluggish reactivity toward PMSO. In parallel, the formation of methyl phenyl sulfone (PMSO₂) product in the Mn(VII)/bisulfite system was observed, suggesting the role of high-valent Mn-oxo species as an oxygen-atom donor in conversion of PMSO to PMSO₂. Moreover, the yield of PMSO₂ (i.e., mole of PMSO₂ produced per mole of PMSO degraded) was quantified to be 20–100%, strongly depending on the [Mn(VII)]/[bisulfite] ratio as well as solution pH. The competitive contribution of sulfate radical, which oxidized PMSO to hydroxylated and/or polymeric products but not to PMSO₂, accounted for the yield of PMSO₂ less than 100%. This work advances the fundamental understanding of a novel class of oxidation technology based on the combination of Mn(VII) and bisulfite for environmental decontamination.
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