Sorption and diffusion of per-polyfluoroalkyl substances (PFAS) in high-density polyethylene geomembranes

• Published in: Waste management (Elmsford) 2024-02, Vol.174, p.15-23
• Main Authors: Ahmad, Aamir, Tian, Kuo, Tanyu, Burak, Foster, Gregory D
• Format: Article
• Language: English
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/j.wasman.2023.11.015

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 per-polyfluoroalkyl substances (PFAS) with varying number of carbons in chain and functional groups on HDPE GM. Perfluoroalkyl carboxyl acids (PFCAs), perfluoroalkyl sulphonic acids (PFSAs), alkyl-sulfonamidoacetic acids (FOSAAs), fluorotelomer sulfonic acids (FtSAs), alkane sulfonamides (FOSA) and ether carboxylic acids (Gen X) were investigated in this study. The partition coefficients (K ) on HDPE GM ranged from 3.8 to 98.3 L/kg. PFAS with amide and sulfonic functional groups showed stronger sorption than that of PFAS with carboxylic acid functional groups. Molecular weight directly affected the K for long-chained PFAS whereas the K of short-chained PFAS was not sensitive to molecular weight. The diffusion coefficients (D ) of PFCAs and PFSAs through 0.1-mm HDPE GM were found to be in the orders of 10 to 10 m /s. The D decreased with increasing molar mass and were also observed to be dependent on the functional group. D of PFSAs was lower than that of PFCAs for similar number of carbons in the chain. The estimated mass flux for PFAS in an intact 1.5-mm HDPE GM varied from 38.7 to 2080.8 ng/m /year whereas the estimated diffusive breakthrough time for PFAS in intact 1.5-mm HDPE was 1526 years or longer.