Defluorination of Per- and Polyfluoroalkyl Substances (PFASs) with Hydrated Electrons: Structural Dependence and Implications to PFAS Remediation and Management
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Open Access
- 15 March 2019
- journal article
- research article
- Published by American Chemical Society (ACS) in Environmental Science & Technology
- Vol. 53 (7), 3718-3728
- https://doi.org/10.1021/acs.est.8b06648
Abstract
This study investigates critical structure–reactivity relationships within 34 representative per- and polyfluoroalkyl substances (PFASs) undergoing defluorination with UV-generated hydrated electrons. While CnF2n+1–COO– with variable fluoroalkyl chain lengths (n = 2 to 10) exhibited a similar rate and extent of parent compound decay and defluorination, the reactions of telomeric CnF2n+1–CH2CH2–COO– and CnF2n+1–SO3– showed an apparent dependence on the length of the fluoroalkyl chain. Cross comparison of experimental results, including different rates of decay and defluorination of specific PFAS categories, the incomplete defluorination from most PFAS structures, and the surprising 100% defluorination from CF3COO–, leads to the elucidation of new mechanistic insights into PFAS degradation. Theoretical calculations on the C–F bond dissociation energies (BDEs) of all PFAS structures reveal strong relationships among (i) the rate and extent of decay and defluorination, (ii) head functional groups, (iii) fluoroalkyl chain length, and (iv) the position and number of C–F bonds with low BDEs. These relationships are further supported by the spontaneous cleavage of specific bonds during calculated geometry optimization of PFAS structures bearing one extra electron, and by the product analyses with high-resolution mass spectrometry. Multiple reaction pathways, including H/F exchange, dissociation of terminal functional groups, and decarboxylation-triggered HF elimination and hydrolysis, result in the formation of variable defluorination products. The selectivity and ease of C–F bond cleavage highly depends on molecular structures. These findings provide critical information for developing PFAS treatment processes and technologies to destruct a wide scope of PFAS pollutants and for designing fluorochemical formulations to avoid releasing recalcitrant PFASs into the environment.Keywords
Funding Information
- University of California, Riverside
- Division of Chemistry (CHE-1709286, CHE-1709719)
- National Science Foundation
- Strategic Environmental Research and Development Program (ER-1497, ER-1289)
This publication has 56 references indexed in Scilit:
- Electrochemical Transformations of Perfluoroalkyl Acid (PFAA) Precursors and PFAAs in Groundwater Impacted with Aqueous Film Forming FoamsEnvironmental Science & Technology, 2018
- High Performance Nanofiltration Membrane for Effective Removal of Perfluoroalkyl Substances at High Water RecoveryEnvironmental Science & Technology, 2018
- Advanced Oxidation/Reduction Processes treatment for aqueous perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) – A review of recent advancesChemical Engineering Journal, 2018
- Emerging poly- and perfluoroalkyl substances in the aquatic environment: A review of current literatureWater Research, 2017
- Sorption of Poly- and Perfluoroalkyl Substances (PFASs) Relevant to Aqueous Film-Forming Foam (AFFF)-Impacted Groundwater by Biochars and Activated CarbonEnvironmental Science & Technology, 2017
- Electrochemical treatment of perfluorooctanoic acid and perfluorooctane sulfonate: Insights into mechanisms and application to groundwater treatmentChemical Engineering Journal, 2017
- Degradation and Removal Methods for Perfluoroalkyl and Polyfluoroalkyl Substances in WaterEnvironmental Engineering Science, 2016
- Behaviour and fate of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in drinking water treatment: A reviewWater Research, 2014
- Monitoring of Perfluorinated Compounds in Aquatic Biota: An Updated ReviewEnvironmental Science & Technology, 2011
- Efficient Electrochemical Oxidation of Perfluorooctanoate Using a Ti/SnO2-Sb-Bi AnodeEnvironmental Science & Technology, 2011