Enhancing the Abatement of Permanganate-inert Micropollutants: Multiple Roles of Nascent Manganese Dioxide in Permanganate Oxidation

Sining Wu; Kaiheng Guo; Ruijie Xie; Shaoxiong He; Wenrui Wei; Jingyun Fang

doi:10.1016/j.watres.2023.120562

Enhancing the Abatement of Permanganate-inert Micropollutants: Multiple Roles of Nascent Manganese Dioxide in Permanganate Oxidation

Water Res. 2023 Oct 15:245:120562. doi: 10.1016/j.watres.2023.120562. Epub 2023 Aug 31.

Authors

Sining Wu¹, Kaiheng Guo², Ruijie Xie¹, Shaoxiong He¹, Wenrui Wei³, Jingyun Fang¹

Affiliations

¹ Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, 510275, P. R. China.
² Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, 510275, P. R. China. Electronic address: guokh3@mail.sysu.edu.cn.
³ Guangzhou Environmental Protection Investment Group Co., Ltd., Guangzhou, 510170, China.

PMID: 37708775
DOI: 10.1016/j.watres.2023.120562

Abstract

Permanganate (Mn(VII)) is widely used as an oxidant in water treatment and usually reduced to nascent manganese dioxide (MnO₂), which could promote Mn(VII) oxidation for the Mn(VII)-reactive compounds such as phenols and anilines. However, the removal of micropollutants containing diverse functional groups and the underlying mechanisms remain largely unexplored. This study reveals that Mn(VII)/nascent MnO₂ was effective for the degradation of Mn(VII)-inert micropollutants, including sulfonamide antibiotics, β-blockers and trimethoprim, with observed first-order rate constants (k'_obs) of 0.126 ∼ 9 min^-1 at pH 4.0. The synergetic effect of Mn(VII) and nascent MnO₂ on the degradation of Mn(VII)-inert micropollutants decreased significantly when pH increased from 4.0 to 9.5. MnO₂ played multiple roles in micropollutant degradation, which acted as a catalyst to promote the Mn(VII) oxidation of trimethoprim and propranolol, as well as an oxidant in propranolol degradation. Besides, Mn(III) oxidation accounted for 58% of the overall degradation of propranolol, but was not important for trimethoprim oxidation. Hydroxylated products were common products formed in Mn(VII)/MnO₂. Differently, trimethoprim tended to form single-ring products via MnO₂-catalyzed Mn(VII) oxidation, while propranolol preferentially formed dimers via in situ formed MnO₂ oxidation. This study is the first to report that MnO₂ enhances the abatement of Mn(VII)-inert micropollutants during Mn(VII)-based water treatment and unravels the multiple roles of MnO₂ in micropollutant degradation by Mn(VII)/MnO₂.

Keywords: Permanganate; manganese dioxide; micropollutants; oxidation; water treatment.