University of Oulu

Ren, Z., Bergmann, U., & Leiviskä, T. (2021). Reductive degradation of perfluorooctanoic acid in complex water matrices by using the UV/sulfite process. In Water Research (Vol. 205, p. 117676). https://doi.org/10.1016/j.watres.2021.117676

Reductive degradation of perfluorooctanoic acid in complex water matrices by using the UV/sulfite process

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Author: Ren, Zhongfei1; Bergmann, Ulrich2; Leiviskä, Tiina1
Organizations: 1Chemical Process Engineering, University of Oulu, P.O. Box 4300, Oulu FIN-90014, Finland
2Department of Biochemistry and Biocenter, University of Oulu, Oulu FIN-99020, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 4.4 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe2021101851417
Language: English
Published: Elsevier, 2021
Publish Date: 2021-10-18
Description:

Abstract

Hydrated electrons (e⁻aq, E= -2.9 V) generated by advanced reduction processes (ARPs) have been proved to be a promising approach to eliminate various per- and polyfluoroalkyl substances (PFASs) in water. In this study, the decomposition of perfluorooctanoic acid (PFOA) in a complex water matrix by e⁻aq generated from the UV/sulfite process was investigated. The effect of pH (9–12) and co-existing compounds (chloride, nitrate, phosphate, carbonate and humic acid) on PFOA degradation efficiency was studied. In addition, the intermediates and possible degradation pathways were analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS). The results showed that the concentration of PFOA was below the detection limit (10 μg/L) after 1 h (conditions: C0 10 mg/L, initial pH = 10, sulfite 10 mM) while 89% defluorination was achieved after 24 h. Using a higher initial pH (pH = 12) greatly enhanced the PFOA degradation as 100% degradation and 98% defluorination were achieved after 24 h. The presence of carbonate (> 5 mM), nitrate (> 2 mM) and humic acid (> 25 mg/L) showed a significant negative effect on PFOA degradation via a UV blocking effect or quenching of hydrated electrons while the presence of chloride and phosphate had a smaller effect on PFOA degradation. Even at extremely high concentrations of chloride (1.709 M, pH = 11.25), the defluorination ratio reached 97% after 24 h of reaction time. During the process, short-chain perfluorinated carboxylic acids (PFCAs, C < 7) and hydrogen substituted compounds were detected, which implies that chain-shortening and H/F change reactions had occurred. Moreover, this confirmed the generation of sulfonated and unsaturated intermediates during the process, which disclosed valuable new mechanistic insights into PFOA degradation.

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Series: Water research
ISSN: 0043-1354
ISSN-E: 1879-2448
ISSN-L: 0043-1354
Volume: 205
Article number: 117676
DOI: 10.1016/j.watres.2021.117676
OADOI: https://oadoi.org/10.1016/j.watres.2021.117676
Type of Publication: A1 Journal article – refereed
Field of Science: 218 Environmental engineering
Subjects:
Funding: The research has been conducted as part of the Less-PFAS project “Sustainable management of PFAS-contaminated materials”, funded by the European Union program Interreg Nord 2019–2022 and the Regional Council of Lapland.
Copyright information: © 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
  https://creativecommons.org/licenses/by/4.0/