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Impact of dissolved O2 on phenol oxidation by δ-MnO2

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Abstract

Although redox reactions of organic contaminants with manganese oxides have been extensively studied, the role of dissolved O2 in these processes has largely been overlooked. In this study, the oxidative degradation of phenol by δ-MnO2 was investigated under both oxic and anoxic conditions. Dissolved O2 inhibited phenol degradation due to its promoting role in the reoxidation and precipitation of reduced Mn(II) to Mn(III) on the δ-MnO2 surface, resulting in partial transformation of δ-MnO2 to “c-disordered” H+-birnessite at pH 5.5 and feitknechtite, manganite, and hausmannite at pH 7.0 and 8.5. The reformed Mn(III) phases could reduce phenol oxidation by blocking reactive sites of δ-MnO2. In addition, dissolved O2 caused a higher degree of particle agglomeration and a more severe specific surface area decrease, and hence lower reactivity of δ-MnO2. These findings revealed that after reductive dissolution by phenol and reoxidation by dissolved O2 throughout continuous redox cycling, δ-MnO2 became less reactive rather than being regenerated. These results can provide new insights into the understanding of the oxidation of organic contaminants by manganese oxides in the natural environment.

Graphical abstract: Impact of dissolved O2 on phenol oxidation by δ-MnO2

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Publication details

The article was received on 25 Aug 2019, accepted on 23 Oct 2019 and first published on 24 Oct 2019


Article type: Paper
DOI: 10.1039/C9EM00389D
Environ. Sci.: Processes Impacts, 2019, Advance Article

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    Impact of dissolved O2 on phenol oxidation by δ-MnO2

    E. Hu, S. Pan, W. Zhang, X. Zhao, B. Liao and F. He, Environ. Sci.: Processes Impacts, 2019, Advance Article , DOI: 10.1039/C9EM00389D

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