Sorption of PFAS on Natural and Engineered Materials for Waste Containment

Per- and polyfluorinated alkyl substances (PFAS) are widely used surfactant chemicals that present engineering challenges due to their persistence in the environment and toxicity concerns for human health. PFAS enters landfills through consumer waste and can be present in landfill leachates at concentrations orders of magnitude greater than drinking water standards. The review serves as a starting point to assess the efficacy of engineered barrier systems to contain PFAS in landfill leachate by critically reviewing existing knowledge of PFAS sorption onto earthen and polymeric materials used in landfill liner systems.
Sorption of PFAS occurs through a combination of hydrophobic interactions from the fluorinated carbon chain and electrostatic interactions from the PFAS functional group. Factors influencing PFAS sorption include organic matter concentration, solution pH, ionic strength, soil minerology, and PFAS structure. Sorption of long chain PFAS (i.e. greater than 7 carbons) is primarily controlled by hydrophobic partitioning into organic matter, whereas sorption of short chain PFAS is primarily dependent on electrostatic interactions with charged surfaces. Bentonite clay used in geosynthetic clay liners (GCLs) may not be effective at sorbing PFAS, but polymeric components such as geomembranes and geotextiles may provide significant sorption of PFAS. Certain cross-linked and cationic polymer additives may be used in bentonite polymer composite GCLs for enhanced PFAS sorption.
An experimental method was developed to quantify PFAS sorption to typical landfill liner components using sorption batch tests. The PFAS analysis method was developed using a Thermo Scientific Altis LC-MS/MS. Experiments were unable to be fully conducted, but the developed method should provide guidance for future research.