Transport of per-polyfluoroalkyl substances (PFAS) in high-density polyethylene (HDPE) geomembrane liners

The objective of this study is to investigate the fate and transport of per-polyfluoroalkyl substances (PFAS) through a high-density polyethylene (HDPE) geomembrane (GM) that is commonly used in landfill composite liner systems. Tests were conducted to measure the sorption and diffusion of four per-polyfluoroalkyl substances (PFAS) with varying numbers of carbons in chain and functional groups on HDPE GM. Perfluoroalkyl carboxyl acids (PFCAs), and perfluoroalkyl sulphonic acids (PFSAs) were investigated in this study. The partition coefficients (Kd) on HDPE GM ranged from 5 to 12 L/Kg. Kd showed an increasing trend with chain length and were found to be sensitive to functional groups of PFAS. Molecular weight directly affected the Kd. The diffusion coefficients (Dg) of PFCAs and PFSAs through 0.1-mm HDPE GM were found to be in the orders of 10-18 to 10-17 m2/s. The Dg decreased with increasing molar mass and were also observed to be dependent on the functional group. Dg of PFSAs was lower than that of PFCAs for a similar number of carbons in the chain.