title: Heat-activated persulfate oxidation of PFOA, 6:2 fluorotelomer sulfonate, and PFOS under conditions suitable for in-situ groundwater remediation.
abstract: PFOA (perfluorooctanoic acid) oxidation (0.121-6.04 μM) by heat-activated persulfate was evaluated at 20-60 °C with 4.2-84 mM [Formula: see text] and in the presence of soluble fuel components to assess feasibility for in-situ remediation of groundwater. 6:2 fluorotelomer sulfonic acid/sulfonate (6:2 FTSA) and PFOS (perfluorooctanesulfonic acid) persulfate oxidation was also evaluated in a subset of conditions given their co-occurrence at many sites. High performance liquid chromatography electron spray tandem mass spectrometry was used for organic analysis and fluoride was measured using a fluoride-specific electrode. PFOA pseudo-1st order transformation rates (k1,PFOA) increased with increasing temperature (half-lives from 0.1 to 7 d for 60 to 30 °C) sequentially removing CF2 groups ('unzipping') to shorter chain perfluoroalkyl carboxylic acids (PFCAs) and F(-). At 50 °C, a 5-fold increase in [Formula: see text] led to a 5-fold increase in k1,PFOA after which self-scavenging by sulfate radicals decreased the relative rate of increase with more [Formula: see text] . Benzene, toluene, ethylbenzene and xylene did not affect k1,PFOA even at 40 times higher molar concentrations than PFOA. A modeling approach to explore pathways strongly supported that for 6:2 FTSA, both the ethyl linkage and CF2-CH2 bond of 6:2 FTSA oxidize simultaneously, resulting in a ratio of ∼25/75 PFHpA/PFHxA. The effectiveness of heat-activated [Formula: see text] on PFOA oxidation was reduced in a soil slurry; therefore, repeated persulfate injections are required to efficiently achieve complete oxidation in the field. However, PFOS remained unaltered even at higher activation temperatures, thus limiting the sole use of heat-activated persulfate for perfluoroalkyl substances removal in the field.
authors.affiliation: Purdue University, Department of Agronomy, Ecological Science and Engineering, West Lafayette, IN 47907-2054, USA.
authors.forename: Saerom
authors.initials: S
authors.lastname: Park
authors.affiliation: Purdue University, Department of Agronomy, Ecological Science and Engineering, West Lafayette, IN 47907-2054, USA. Electronic address: lslee@purdue.edu.
authors.forename: Linda S
authors.initials: LS
authors.lastname: Lee
authors.affiliation: U.S. Army Engineer Research and Development Center, Vicksburg, MS 39180-6199, USA.
authors.forename: Victor F
authors.initials: VF
authors.lastname: Medina
authors.affiliation: Purdue University, Department of Agronomy, Ecological Science and Engineering, West Lafayette, IN 47907-2054, USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Zull
authors.affiliation: U.S. Army Engineer Research and Development Center, Vicksburg, MS 39180-6199, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Waisner
mesh_terms: D002210:Caprylates / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry; D052918:Environmental Restoration and Remediation; D005466:Fluorocarbons / Q000737:chemistry*; D060587:Groundwater / Q000737:chemistry; D006358:Hot Temperature; D017670:Sodium Compounds / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry*; D013451:Sulfonic Acids / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D002210:Caprylates; D002264:Carboxylic Acids; D005466:Fluorocarbons; D017670:Sodium Compounds; D013431:Sulfates; D013451:Sulfonic Acids; D014874:Water Pollutants, Chemical; C069025:sulfate radical; C023036:perfluorooctanoic acid; C024625:sodium persulfate
keywords: 6:2 FTSA; Heat-activated persulfate; Oxidation; PFOA; PFOS