Insight into electrochemically boosted trace Co(II)-PMS catalytic process: Sustainable Co(IV)/Co(III)/Co(II) cycling and side reaction blocking

Zizeng Wang; Bingzhi Liu; Changhao Ji; Lei Tang; Baorong Huang; Li Feng; Yong Feng

doi:10.1016/j.jhazmat.2023.130905

Insight into electrochemically boosted trace Co(II)-PMS catalytic process: Sustainable Co(IV)/Co(III)/Co(II) cycling and side reaction blocking

J Hazard Mater. 2023 Apr 15:448:130905. doi: 10.1016/j.jhazmat.2023.130905. Epub 2023 Feb 1.

Authors

Zizeng Wang¹, Bingzhi Liu², Changhao Ji¹, Lei Tang¹, Baorong Huang¹, Li Feng¹, Yong Feng³

Affiliations

¹ School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou 510006, Guangdong, China.
² School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou 510006, Guangdong, China. Electronic address: lbz@gdut.edu.cn.
³ SCNU Environmental Research Institute, Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety & MOE Key Laboratory of Theoretical Chemistry of Environment, South China Normal University, Guangzhou 510006, China; School of Environment, South China Normal University, University Town, Guangzhou 510006, China.

PMID: 36738620
DOI: 10.1016/j.jhazmat.2023.130905

Abstract

A novel homogeneous electrocatalytic system was constructed by current-assisted trace Co(II) activating PMS (ECP) to remove reactive blue 19 (RB19). More than 93 % of RB19 was rapidly removed with only a trace dose, and the PMS was 98.35 % utilized during the reaction. By exploring the active species and analyzing the PMS consumption, it was found that current strongly accelerated the Co(III)/Co(II) redox cycle by providing electrons to Co(III), and inhibited the side reaction thus improving the PMS utilization. Electric energy per order was very low, only 0.26 kWh·m³. Radicals (SO₄^•-) and non-radicals (Co(III), Co(IV) and ¹O₂) participated in ECP system, in which SO₄^•- was dominant. By excluding the other three precursors (PMS, •OH and O₂^•-), the side reaction product SO₅^•- was identified as the source of ¹O₂ in ECP system. Combining chelating agent EDTA and chemical probe PMSO, Co(IV) was considered formed by single and double charge transfer. Five degradation pathways of RB19 were proposed using mass spectrometry and DFT calculation. The ecotoxicity and mutagenicity of RB19 and its transformation products were predicted using software simulation. These studies provided an interesting insights into the synergistic Co(II)-PMS systems and offered a new strategy for electrochemical processes.

Keywords: Electrochemical oxidation; High-valent cobalt species; Peroxymonosulfate; Pollutants elimination; Reactive oxygen species.