Understanding the nonradical activation of peroxymonosulfate by different crystallographic MnO2: The pivotal role of MnIII content on the surface

Shitai Shen; Xinquan Zhou; Qindi Zhao; Wang Jiang; Jia Wang; Liuyang He; Yongfei Ma; Lie Yang; Zhuqi Chen

doi:10.1016/j.jhazmat.2022.129613

Understanding the nonradical activation of peroxymonosulfate by different crystallographic MnO₂: The pivotal role of Mn^III content on the surface

J Hazard Mater. 2022 Oct 5:439:129613. doi: 10.1016/j.jhazmat.2022.129613. Epub 2022 Jul 16.

Authors

Shitai Shen¹, Xinquan Zhou², Qindi Zhao³, Wang Jiang³, Jia Wang³, Liuyang He¹, Yongfei Ma¹, Lie Yang⁴, Zhuqi Chen⁵

Affiliations

¹ Hubei Key Laboratory of Mineral Resources Processing and Environment, School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, China.
² Chemical Engineering & Pharmaceutical College, Henan University of Science and Technology, Luoyang 471023, China.
³ Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
⁴ Hubei Key Laboratory of Mineral Resources Processing and Environment, School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, China. Electronic address: yanglie612@whut.edu.cn.
⁵ Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. Electronic address: zqchen@hust.edu.cn.

PMID: 35863233
DOI: 10.1016/j.jhazmat.2022.129613

Abstract

Manganese oxide-activated persulfate plays a critical role in water purification and in situ chemical oxidation processes, but the underlying mechanism needs to be further revealed. Herein, the detailed mechanism of MnO₂ with various crystallographic structures (α-, β-, γ-, and δ-MnO₂) towards peroxymonosulfate (PMS) activation was investigated. PMS activated by tunnel structured α-, β-, and γ-MnO₂ showed higher acetaminophen (ACE) removal than layer structured δ-MnO₂ with the removal efficiency following an order of α-MnO₂ (85%) ≈ γ-MnO₂ (84%) > β-MnO₂ (65%) > δ-MnO₂ (31%). Integrated with chemical quenching experiments, electron paramagnetic resonance, Raman spectra, X-ray photoelectron spectroscopy, and Langmuir-Hinshelwood model on kinetic data, both surface-bound PMS complexes and direct oxidation by surface manganese species (Mn^{(Ⅳ, Ⅲ)}_(s)) were disclosed as the dominant oxidation mechanism for ACE degradation in α-, β-, and γ-MnO₂/PMS, which were rarely observed in previous reports. Moreover, the catalytic activity of α-, β-, and γ-MnO₂ was positively correlated to the Mn^III_(s) content on the catalyst surface. Higher content of Mn^III_(s) would stimulate the generation of more oxygen vacancies, which was conducive to the adsorption of PMS and the formation of reactive complexes. Overall, this study might provide deeper insight into the nonradical activation mechanism of PMS over different crystallographic MnO₂.

Keywords: Acetaminophen; MnO(2); Non-radical mechanism; Oxygen vacancies; Peroxymonosulfate.