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 (1st Langmuir) where PFAS occupy the charged interlayers, and finally phase IV (2nd 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).
