Practical implications of perfluoroalkyl substances adsorption on bottle materials: Isotherms

To assess the practical implications of various bottle materials used in anion exchange (IX) or granular activated carbon (GAC) isotherm experiments, adsorption of seven per- and polyfluoroalkyl substances (PFAS) onto three common bottle materials (silanized glass, polypropylene, and high-density polyethylene [HDPE]) were screened. Results were similar between bottle materials; therefore, only HDPE was used in a detailed bottle material isotherm study with 11 PFAS. For each PFAS, an HDPE bottle isotherm was generated with equilibrium liquid phase concentrations relevant to drinking water (<2000 ng/L). Percent PFAS recoveries between 90% and 103%, 85% and 114%, and 54% and 108% were determined for perfluoro-2-propoxypropanoic acid (GenX), five perfluoroalkyl carboxylic acids, and five perfluoroalkyl sulfonic acids (PFSA), respectively. These results indicated only the five PFSA adsorbed to the HDPE bottles in a concentration-dependent manner. Furthermore, linear isomer versions of two PFSA exhibited greater adsorption. For each PFSA studied, a linear isotherm was generated and used to develop guidance for conducting future IX and GAC isotherm studies. Specifically, the minimum initial isotherm concentration was established such that a maximum 1% loss would be expected to the HDPE bottles, resulting in required initial concentrations of the five PFSA between 21 and 75 times that of the design isotherm liquid equilibrium concentration.