New insights into the mechanism of Fered-Fenton treatment of industrial wastewater with high chloride content: Role of multiple reactive species

Zehong Chen; Pan Xia; Dazhi Wang; Xiaodong Niu; Lixin Ao; Qiang He; Sha Wang; Zhihong Ye; Ignasi Sirés

doi:10.1016/j.scitotenv.2023.163596

New insights into the mechanism of Fered-Fenton treatment of industrial wastewater with high chloride content: Role of multiple reactive species

Sci Total Environ. 2023 Jul 15:882:163596. doi: 10.1016/j.scitotenv.2023.163596. Epub 2023 Apr 19.

Authors

Zehong Chen¹, Pan Xia¹, Dazhi Wang², Xiaodong Niu², Lixin Ao³, Qiang He¹, Sha Wang², Zhihong Ye⁴, Ignasi Sirés⁵

Affiliations

¹ Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing 400045, China.
² Environmental Protection Research Institute, Southwest Ordnance Industry, Chongqing 400042, China.
³ Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing 400045, China; Environmental Protection Research Institute, Southwest Ordnance Industry, Chongqing 400042, China.
⁴ Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing 400045, China. Electronic address: yezhihong@cqu.edu.cn.
⁵ Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Ciència de Materials i Química Física, Secció de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain. Electronic address: i.sires@ub.edu.

PMID: 37084916
DOI: 10.1016/j.scitotenv.2023.163596

Abstract

Hydroxyl radical (OH) is considered the dominant reactive species in the electro-Fenton (EF) and Fered-Fenton (EF-Fere) processes for wastewater treatment. However, in chloride-rich media, this is arguable due to the obscure mechanisms for the oxidant speciation and pollutant degradation. Herein, the role of active chlorine and Fe(IV)-oxo species (Fe^IVO²⁺) as primary oxidizing agents in HClO-mediated Fered-Fenton (EF-Fere-HClO) process is discussed, along with the dependence of their contribution on the pollutant structure. HClO generated from anodic oxidation of Cl^- can be consumed by added H₂O₂ to form singlet oxygen (¹O₂), which is detrimental because this species is quickly deactivated by water. The reaction between HClO and Fe²⁺ was proved to generate Fe^IVO²⁺, rather than OH or Cl suggested in the literature. The yield of Fe^IVO²⁺ species was proportional to the Cl^- concentration and barely affected by solution pH. The long-lived HClO and Fe^IVO²⁺ can selectively react with electron-rich compounds, which occurs simultaneously to the non-selective attack of OH formed from Fenton's reaction. The Fe^IVO²⁺ and OH concentration profiles were successfully modelled. Although the accumulation of toxic chlorinated by-products from HClO-mediated oxidation might cause new environmental concerns, the toxicity of pesticide wastewater with 508 mM Cl^- was halved upon EF-Fere-HClO treatment.

Keywords: Active chlorine production; Fe(IV)O(2+); Fered-Fenton process; Hydroxyl radical; Industrial wastewater.