Efficient purification of a nitrate and chlorate mixture in water via photoredox activated intermediate coupling-decoupling pathway

Weiping Yang; Xin Li; Ruimin Chen; Shujie Shen; Lei Xiao; Jieyuan Li; Fan Dong

doi:10.1016/j.jhazmat.2023.131964

Efficient purification of a nitrate and chlorate mixture in water via photoredox activated intermediate coupling-decoupling pathway

J Hazard Mater. 2023 Sep 15:458:131964. doi: 10.1016/j.jhazmat.2023.131964. Epub 2023 Jun 29.

Authors

Weiping Yang¹, Xin Li¹, Ruimin Chen¹, Shujie Shen¹, Lei Xiao¹, Jieyuan Li², Fan Dong¹

Affiliations

¹ Research Center for Carbon-Neutral Environmental & Energy Technology, Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China.
² Research Center for Carbon-Neutral Environmental & Energy Technology, Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China. Electronic address: jieyli@uestc.edu.cn.

PMID: 37399724
DOI: 10.1016/j.jhazmat.2023.131964

Abstract

Nitrate (NO₃^-) is a widespread contaminant that threatens human health and ecological safety. Meanwhile, the disinfection byproducts chlorate (ClO₃^-) is generated inevitably in conventional wastewater treatment. Therefore, the contaminants mixture of NO₃^- and ClO₃^- are universal in common emission units. Photocatalysis technology is a feasible approach for the synergistic abatement of contaminant mixture, where matching suitable oxidation reactions is a potential strategy to improve the photocatalytic reduction reactions. Herein, formate (HCOOH) oxidation is introduced to facilitate the photocatalytic reduction of the NO₃^- and ClO₃^- mixture. As a result, high purification efficiency of NO₃^- and ClO₃^- mixture are achieved, evidenced by 84.6% e^--dependent removal of the mixture at a reaction time of 30 min, with 94.5% N₂ selectivity and 100% Cl^- selectivity, respectively. Specifically, by the close combination of in-situ characterizations and theoretical calculations, the detailed reaction mechanism is revealed, in which the intermediate coupling-decoupling route from NO₃^- reduction and HCOOH oxidation is established by the chlorate-induced photoredox activation, leading to the significantly enhanced efficiency for the wastewater mixture purification. The practical application of this pathway is established for simulated wastewater to show its wide applicability. This work provides new insights into photoredox catalysis technology for its environmental application.

Keywords: Contaminants mixture; Coupling-decoupling pathways; In-situ characterizations; Nitrate reduction; Photoredox catalysis.