Trichloroethene

Perfluorooctanoic acid (CAS#335–67-1; of 98% purity) was purchased from AIKE Reagent. Sodium perfluorooctanoate (CAS#335–95-5; 97%) was purchased from Manchester Organics. Sodium perfluoropentanoate (CAS#2706–89-0; >99%) was purchased from Synquest Laboratories. Potassium perfluorooctanesulfonate CAS# 2795–39-3; 98%) was purchased from Matrix Scientific. Perfluorotridecanoic acid (CAS# 72629–94-8; 97%), perfluorooctanesulfonic acid (CAS# 1763–23-1, 98%), sodium dodecylbenzene sulfate (CAS# 25155–30-0; technical grade), trichloroethene (CAS# 79–01-6; >99.5%), and humic acid (CAS#1415–93-6; technical grade) were purchased from Sigma Aldrich. Ethanol (CAS# 64–17-5; 99.9%) was purchased from Aaper Alcohol.
Different background electrolyte solutions were used to test the influence of solution ionic composition on surface tension. These included deionized water, 0.01 M NaCl, 0.1 M NaCl, 0.01 M KCl, 0.01 M CaCl₂, and a synthetic groundwater (SGW). The SGW (concentration, mg/L) consists of the following cations: Na⁺¹ (50), Ca⁺² (36), Mg⁺² (25), and anions: NO₃⁻¹ (6), Cl⁻¹ (60), CO₃⁻²/HCO₃⁻¹ (133), and SO₄⁻² (99). The pH and ionic strength of the groundwater solution are 7.7 and 0.01M, respectively. Solutions were prepared using distilled, deionized water.

PFOS (CAS# 1763-23-1, Sigma-Aldrich, 98% purity) and PFOA (CAS# 335-67-1, Alfa Aesar, 95%) were used as representative PFAS in the experiments. Additionally, perfluoropentanoic acid (PFPeA) was used for interfacial-tension measurements (CAS# 2706-96-3, TCI America, 98%). Pentafluorobenzoic acid (Strem Chemicals, 99% purity), which is not a PFAS, was used as the nonreactive tracer (NRT). Trichloroethene (CAS# 79-01-6, Sigma-Aldrich, >99.5% purity) and decane (CAS # 124-15-5, Sigma-Aldrich, 99% purity) were used as representative dense (DNAPL) and light (LNAPL) NAPLs, respectively. Experiments were conducted with either 0.01 M NaCl or synthetic groundwater (SGW) solutions. A commercial quartz sand (Accusand, Unimin Corp., Ottawa, Mn) was used in the column experiments. SGW and sand characteristics are detailed in section S1 of the SI.