Water and Remediation Catalog.

Authors: Bei Yan, Jian Wang, Jinxia Liu

DOI: https://doi.org/10.1016/j.watres.2021.117371Get rights and content

Synopsis:

• Molecular mechanism of surface modified clay (SMC) adsorbent with anionic and neutral Per- and polyfluoroalkyl substances (PFAS) in AFFF contaminated groundwater were evaluated with synchrotron based scanning transmission X-ray microscopy (STXM) coupled with X-ray absorption near edge structure spectroscopy (XANES)
• Adsorption isotherms for FLUORO-SORB® were developed piecewise with four phases because a single model was not suitable across concentrations of 1x10^-9 to 1x10^-5 mol/L. The variability in isotherm trends at different concentrations indicate that adsorption mechanisms were significantly impacted by minor perturbations suggesting SMC heterogeneity
• Isotherms were classified as follows: Phase I (Linear) where PFAS occupy charged edges of the clay platelet interlayers, phase II + III (1^st Langmuir) where PFAS occupy the charged interlayers, and finally phase IV (2^nd Langmuir) where platelet expansion occurs to allow for higher concentration of PFAS to be sequestered by the SMC adsorbent. Phases I-III are characterized as low concentration isotherms, while phase IV displays adsorption capacity at high concentrations
• FLUORO-SORB® binding mechanisms were elucidated in this study and include charge-charge, charge-dipole, and dipole-dipole interactions, varying by PFAS structure

Brief: Binding mechanisms of FLUORO-SORB® SMC adsorbent with PFAS have been elucidated using STXM and XANES in a recent study. Piecewise adsorption isotherms (from PFAS concentrations of 1x10^-9 to 1x10^-5 mol/L) were established and defined as phase I: binding to charged platelet edges (linear isotherm), phase II+III: adsorption to charged platelet interlayers (Langmuir isotherm), phase IV: expansion of the platelets allowing more PFAS to be captured within the charged interlayers at high concentrations (Langmuir isotherm).