The potential application of available
adsorbents for in situ polyfluoroalkyl
substances (PFAS) sequestration, including the release of previously
sequestered PFAS under changing groundwater chemistries, was investigated
using batch studies. Injectable adsorbent suspensions (IASs) were
prepared from 2 anion-exchange resins (A-IXR and L-IXR), a powdered
activated carbon, an activated charcoal, a surface-modified organoclay–carbon
composite (NMC+
n
), and a carbonaceous-clay-organic
material (ROAC). The IAS was amended to water-saturated sand after
which multicomponent PFAS sorption and desorption with deionized water
and simulated groundwater were investigated. PFAS sorption was instantaneous
and chain-length-dependent, reaching approximately 100% in the IAS-amended
sand, except for ROAC. In general, PFAS sorption isotherms were nonlinear,
with larger sorption capacities of the long-chain than short-chain
PFAS. The sorption capacity of the A-IXR (IAS) amendment was 2.5 times
the capacities of the other amendments. In simulated groundwater (AGW),
PFAS were released (5–100%) from the IAS amendments, especially
from A-IXR, affecting mostly the short-chain PFAS and the perfluorocarboxylic
acids. The release was attributed to anion exchange and electrical
double-layer compression effects driven by the coexisting ions in
AGW. Such a considerable release of short- and long-chain PFAS especially
from anion-exchange resins should not be overlooked during decision-making
regarding in situ PFAS sequestration.