Passive sampling provides an affordable and sensitive option to capture time-weighted average (TWA) concentrations of chemicals in aqueous environments. Detection of per- and polyfluoroalkyl substances (PFAS) by passive sampling devices (PSD), however, has not been widely used due to the lack of effective sorbents selective for PFAS and the limited systematic assessments on how the PSD sampling rate is impacted by environmental factors.

The objectives of this project are to design and synthesize a series of novel sorbents for highly selective PFAS sequestration and evaluate their application in PFAS passive sampling, with the ultimate goal of providing representative spatial and temporal interrogation for accurate and precise assessments of PFAS impact. The overarching hypotheses include (1) by rational incorporation of fluoroalkyl chains and polar functional groups into the sorbents, a fluorophilic microenvironment can be created to facilitate highly selective PFAS sorption; and (2) by co-deployment of passive flow monitors and multi-parameter modeling, PSD built with the innovative sorbents will accurately reflect TWA loading into aquatic systems without the need of expensive field calibration.

This project is a collaborative, interdisciplinary effort supported by the compelling preliminary data and systematic knowledge gained from relevant research experiences. Multiple fundamentally new approaches for sorbent design are suggested to achieve selective PFAS sequestration from real water matrices. The approach generates a chemically diverse range of sorbents with a synergistic combination of fluorophilic and ionic functional groups; these functional groups collectively will create a tunable and balanced microenvironment on the sorbent with physiochemical properties appropriate to sequester PFAS with a wide variety of structures. Three conceptually coherent but distinct synthetic approaches will enable the synthesis and optimization of fluorophilic sorbents. The synthesized sorbents will be evaluated for their selectivity, back-extraction recovery, and kinetic/equilibrium sorption parameters over a broad range of PFAS structures under various environmental-relevant conditions. The optimized sorbents will be used to build PSD for bench-scale tests. The PSD will be deployed in a flow through system simulating variable field conditions, and single-variable tests with multiple variable modeling will be used to predict TWA PFAS concentrations in the aqueous phase. The model results will be validated in a surface water matrix in the same system.  

Successful implementation of the PSD will enable better sampling and analysis of PFAS in the environment, which can be further developed to standard operating procedures for field sampling of environmental water. The direct benefit of this project is the more accurate and precise assessment of the extent of PFAS impact, which will lead to the improved and more cost-effective management of PFAS-impacted sites. Sorbents developed in this project also can be used for other purpose such as PFAS removal from impacted environmental matrices. The scientific insights from the sorbent development will fill the knowledge gaps on the relationship between PFAS structures and sorbent properties beyond the previous design rationale that mainly relied on Coloumbic and hydrophobic interactions. The PSD validation method via single-variable tests with multiple-variable modeling can be transferred to the passive sampling studies for other chemicals of concern. (Anticipated Project Completion - 2024)