High-valent metal-oxo species transformation and regulation by co-existing chloride: Reaction pathways and impacts on the generation of chlorinated by-products

Hongyu Zhou; Yong-Li He; Jiali Peng; Xiaoguang Duan; Xiaohui Lu; Heng Zhang; Yang Liu; Chuan-Shu He; Zhaokun Xiong; Tianyi Ma; Shaobin Wang; Bo Lai

doi:10.1016/j.watres.2024.121715

High-valent metal-oxo species transformation and regulation by co-existing chloride: Reaction pathways and impacts on the generation of chlorinated by-products

Water Res. 2024 May 2:257:121715. doi: 10.1016/j.watres.2024.121715. Online ahead of print.

Authors

Hongyu Zhou¹, Yong-Li He², Jiali Peng³, Xiaoguang Duan⁴, Xiaohui Lu³, Heng Zhang², Yang Liu², Chuan-Shu He², Zhaokun Xiong², Tianyi Ma⁵, Shaobin Wang³, Bo Lai⁶

Affiliations

¹ State Key Laboratory of Hydraulics and Mountain River Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China; School of Chemical Engineering, The University of Adelaide, Adelaide, SA 5005, Australia; Sino-German Centre for Water and Health Research, Sichuan University, Chengdu 610065, 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.
³ College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
⁴ School of Chemical Engineering, The University of Adelaide, Adelaide, SA 5005, Australia. Electronic address: xiaoguang.duan@adelaide.edu.au.
⁵ School of Science, STEM College, RMIT University, Melbourne, VIC, 3000, Australia.
⁶ 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: laibo@scu.edu.cn.

PMID: 38728779
DOI: 10.1016/j.watres.2024.121715

Abstract

High-valent metal-oxo species (HMOS) have been extensively recognized in advanced oxidation processes (AOPs) owing to their high selectivity and high chemical utilization efficiency. However, the interactions between HMOS and halide ions in sewage wastewater are complicated, leading to ongoing debates on the intrinsic reactive species and impacts on remediation. Herein, we prepared three typical HMOS, including Fe(IV), Mn(V)-nitrilotriacetic acid complex (Mn(V)NTA) and Co(IV) through peroxymonosulfate (PMS) activation and comparatively studied their interactions with Cl^- to reveal different reactive chlorine species (RCS) and the effects of HMOS types on RCS generation pathways. Our results show that the presence of Cl^- alters the cleavage behavior of the peroxide OO bond in PMS and prohibits the generation of Fe(IV), spontaneously promoting SO₄^•- production and its subsequent transformation to secondary radicals like Cl^• and Cl₂^•-. The generation and oxidation capacity of Mn(V)NTA was scarcely influenced by Cl^-, while Cl^- would substantially consume Co(IV) and promote HOCl generation through an oxygen-transfer reaction, evidenced by density functional theory (DFT) and deuterium oxide solvent exchange experiment. The two-electron-transfer standard redox potentials of Fe(IV), Mn(V)NTA and Co(IV) were calculated as 2.43, 2.55 and 2.85 V, respectively. Due to the different reactive species and pathways in the presence of Cl^-, the amounts of chlorinated by-products followed the order of Co(II)/PMS > Fe(II)/PMS > Mn(II)NTA/PMS. Thus, this work renovates the knowledge of halide chemistry in HMOS-based systems and sheds light on the impact on the treatment of salinity-containing wastewater.

Keywords: Chlorinated by-products; High-valent metal-oxo species; Mechanism; Peroxymonosulfate; Water treatment.