Catalytic ozonation of 4-nitrophenol over an mesoporous α-MnO2 with resistance to leaching

• α-MnO2 is obtained from reduction of KMnO4 with assistance of surfactant.
• CTAB works both as a morphology directing agent and reduction initiator.
• α-MnO2 with high surface area is active in catalytic ozonation of 4-nirtrophenol.
• α-MnO2 is more stable and resistant to leaching than the commercial one.
• 4-Nitrophenol is mainly oxidized by superoxide radicals, not hydroxyl radicals.

Two series of α-MnO2 materials were prepared via a similar method with surfactant cetyltrimethylammonium bromide (CTAB) and sodium dodecyl benzene sulfate (SDBS). The surfactants work both as shape directing agent and reduction initiator. The α-MnO2 synthesized with 0.2 M of CTAB showed a mesoporous structure with high surface area of 387.7 m2/g. It is very active in catalytic ozonation of 4-nitrophenol (4-NP) and total organic carbon removal, with higher catalytic stability than commercial MnO2. Using tert-butanol and p-benzoquinone as scavengers of different oxidative species, we found that superoxide radicals, rather than hydroxyl radicals, were mainly responsible for the degradation of 4-NP.

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