Insight into the electron transfer regime of periodate activation on MnO2: The critical role of surface Mn(IV)

Liwei Yang; Fashan Yang; Heng Zhang; Hongyu Zhou; Mengfan Luo; Yunmei Liu; Chuanliang Zhao; Lu Zheng; Bo Lai

doi:10.1016/j.jhazmat.2023.131479

Insight into the electron transfer regime of periodate activation on MnO₂: The critical role of surface Mn(IV)

J Hazard Mater. 2023 Jul 15:454:131479. doi: 10.1016/j.jhazmat.2023.131479. Epub 2023 Apr 24.

Authors

Liwei Yang¹, Fashan Yang¹, Heng Zhang², Hongyu Zhou³, Mengfan Luo³, Yunmei Liu³, Chuanliang Zhao¹, Lu Zheng¹, Bo Lai³

Affiliations

¹ School of Civil Engineering, Key Laboratory of Water Supply & Sewage Engineering of Ministry of Housing and Urban-rural Development, Chang'an University, Xi'an 710061, China.
² State Key Laboratory of Hydraulics and Mountain River Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China; Sino-German Centre for Water and Health Research, Sichuan University, Chengdu 610065, China. Electronic address: zhangheng01@scu.edu.cn.
³ State Key Laboratory of Hydraulics and Mountain River Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China; Sino-German Centre for Water and Health Research, Sichuan University, Chengdu 610065, China.

PMID: 37104949
DOI: 10.1016/j.jhazmat.2023.131479

Abstract

At present, the potential mechanism of manganese oxide (MnO₂) activation of PI and the key active sites of PI activation are still unclear and controversial. To this end, three different crystal forms of MnO₂ were prepared in this study and used to activate PI to degrade pollutants. The results showed that different crystal types of MnO₂ showed different catalytic abilities, and the order was γ-MnO₂ > α-MnO₂ > β-MnO₂. Through quenching experiments, EPR tests, Raman experiments and in situ electrochemical experiments, it has been confirmed that electron transfer-mediated non-free radical process is the main mechanism of pollutant degradation, in which the active substance is the highly active metastable intermediate complex (MnO₂/PI*). Hydroxyl radical (HO^•), superoxide radical (O₂^•-), singlet oxygen (¹O₂) and iodine radical (IO₃^•) did not participate in pollutant degradation. The quantitative structure-activity relationship analysis confirmed that the catalytic performance of MnO₂ was highly positively correlated with the surface Mn(IV) content, which indicated that the surface Mn(IV) site was the main active site. Overall, this study will be of great help to the design and application of manganese dioxide activation for periodate degradation of pollutants.

Keywords: Crystal forms; Electron transfer; MnO(2); Periodate; Surface Mn(IV) content.