Mechanism of nitro-byproducts formation during persulfate-based electrokinetic in situ oxidation for remediation of anthracene contaminated soil

Longgang Chu; Long Cang; Zhaoyue Sun; Xinghao Wang; Hong Chen; Guodong Fang; Juan Gao

doi:10.1016/j.jhazmat.2023.131396

Mechanism of nitro-byproducts formation during persulfate-based electrokinetic in situ oxidation for remediation of anthracene contaminated soil

J Hazard Mater. 2023 Jul 5:453:131396. doi: 10.1016/j.jhazmat.2023.131396. Epub 2023 Apr 12.

Authors

Longgang Chu¹, Long Cang², Zhaoyue Sun², Xinghao Wang², Hong Chen², Guodong Fang², Juan Gao³

Affiliations

¹ Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
³ Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences Nanjing College, Nanjing 210008, China. Electronic address: juangao@issas.ac.cn.

PMID: 37058937
DOI: 10.1016/j.jhazmat.2023.131396

Abstract

Persulfate-based electrokinetic (EK) chemical oxidation appears to be a novel and viable strategy for the in situ remediation of polycyclic aromatic hydrocarbons (PAHs) polluted soil; however, the possible toxic byproducts of PAHs have been overlooked. In this study, we systematically investigated the formation mechanism of the nitro-byproducts of anthracene (ANT) during the EK process. Electrochemical experiments revealed that NH₄⁺ and NO₂^- originating from nitrate electrolyte or soil substrates were oxidized to NO₂^• and NO^• in the presence of SO₄^•-. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS/MS) analysis with ¹⁵N labeling revealed the formation of nitro-byproducts (14 kinds), including 1-hydroxy-4-nitro-anthraquinone and its similar derivatives, 4-nitrophenol, and 2,4-dinitrophenol. The nitration pathways of ANT have been proposed and described, mainly including the formation of hydroxyl-anthraquinone-oxygen and phenoxy radicals and the subsequent addition of NO₂^• and NO^•. ANT-based formation of nitro-byproducts during EK, which is usually underestimated, should be further investigated due to their enhanced acute toxicity, mutagenic effects, and potential threat to the ecosystem.

Keywords: Inorganic nitrogen; Nitro-byproducts; Nitrogen dioxide radical; Persulfate; Polycyclic aromatic hydrocarbons.