Photo-electrochemical oxidation herbicides removal in stormwater: Degradation mechanism and pathway investigation

Zhaozhi Zheng; Ana Deletic; Cui Ying Toe; Rose Amal; Xiwang Zhang; Russell Pickford; Shujie Zhou; Kefeng Zhang

doi:10.1016/j.jhazmat.2022.129239

Photo-electrochemical oxidation herbicides removal in stormwater: Degradation mechanism and pathway investigation

J Hazard Mater. 2022 Aug 15:436:129239. doi: 10.1016/j.jhazmat.2022.129239. Epub 2022 May 27.

Authors

Zhaozhi Zheng¹, Ana Deletic², Cui Ying Toe³, Rose Amal⁴, Xiwang Zhang⁵, Russell Pickford⁶, Shujie Zhou⁴, Kefeng Zhang⁷

Affiliations

¹ Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, New South Wales 2052, Australia. Electronic address: zhaozhi.zheng@unsw.edu.au.
² Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, New South Wales 2052, Australia; School of Civil and Environmental Engineering, Engineering Faculty, Queensland University of Technology, Queensland 4001, Australia.
³ School of Chemical Engineering, University of New South Wales, New South Wales 2052, Australia; School of Engineering, the University of Newcastle, Callaghan, New South Wales 2308, Australia.
⁴ School of Chemical Engineering, University of New South Wales, New South Wales 2052, Australia.
⁵ Department of Chemical Engineering, Monash University, Clayton, Victoria 3800, Australia.
⁶ Bioanalytical Mass Spectrometry Facility, University of New South Wales, New South Wales 2052, Australia.
⁷ Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, New South Wales 2052, Australia.

PMID: 35739758
DOI: 10.1016/j.jhazmat.2022.129239

Abstract

Although advanced oxidation processes (AOPs) such as photoelectrochemical oxidation (PECO), electrochemical oxidation (ECO) and photocatalytic oxidation (PCO), have shown potential for wastewater treatment, their application in urban stormwater has rarely been studied. This paper explored their major degradation mechanisms and possible degradation pathways of herbicides for stormwater applications (with treatment difficulty compared with wastewater). PECO and ECO showed excellent removal performance for diuron (100 %) and moderate for atrazine (around 35 %) under a relatively low potential (2 V). Superoxide radical (·O₂^-) has been found to be the dominant reactive species. Besides, there is evidence to indicate that hydroxyl radical (·OH) and free chlorine (·Cl) also support the degradation reactions. Up to 11 possible intermediate products have been identified during both diuron and atrazine degradation processes under PECO operation. Based on the proposed possible degradation pathways, the intermediates presented during PECO are species with further oxidation. As evidenced by the undetected species of more oxidized intermediates for ECO and PCO, some further degradation steps are missing, which demonstrate their lower oxidation capacity leading to incomplete decomposition of stormwater herbicides. Thus, PECO has a great potential to be developed into a passive stormwater degradation system due to its strong oxidation potential.

Keywords: Electrochemical oxidation (ECO); Mechanism; Photo-electrochemical oxidation (PECO); Photocatalytic oxidation (PCO); Stormwater micropollutants.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Atrazine*
Diuron
Herbicides* / chemistry
Oxidation-Reduction
Water Pollutants, Chemical* / chemistry
Water Purification*

Substances

Herbicides
Water Pollutants, Chemical
Diuron
Atrazine