The objective of this proof-of-concept project is to develop an innovative, robust and efficient passive sampler that can quantify a wide spectrum of per- and polyfluoroalkyl substances (PFAS) that include perfluoroalkyl acids and emerging polyfluoroalkyl substances in environmentally relevant water matrices. The passive sampling technology under study couples two core components, including (1) periodic mesoporous organosilica (PMO)-based sorbent receiving phase with efficient and selective uptake of a range of PFAS and (2) ceramic membrane barrier with improved stability, anti-fouling property and tunable PFAS diffusion coefficients. As the first step of the passive sampler development, this project aims to address the following specific technical objectives:

• Develop tailored PMO materials with enhanced adsorption of PFAS.
• Develop robust ceramic membrane barriers with tunable PFAS mass transfer.
• Investigate PFAS uptake by the integrated passive sampler.

This project is broken into three research tasks corresponding to the specific research objectives. A suite of relevant anionic, cationic, zwitterionic and nonionic PFAS will be included in this project to represent the vast library of PFAS structures. In Task 1, a novel class of multifunctional PMO sorbent media tailored for PFAS adsorption will be developed, characterized and evaluated. The impact of key environmental variables on the sorbent performance and determine the sorbent-water partition coefficient for PFAS will be investigated. In Task 2, a series of asymmetric ceramic membranes will be prepared consisting of a macroporous substrate coated with a mesoporous thin-film top layer with controllable pore sizes and thin-film thicknesses. A combination of ceramic processing, sol-gel method and atomic layer deposition (ALD) technique will be applied to tune the membrane structure and property to modulate PFAS mass transfer, minimize PFAS uptake by membrane, and enhance membrane resistance to biofouling. Prototype passive samplers will be developed and evaluated in Task 3 based on the polar organic chemical integrative sampler (POCIS) design using the most promising sorbent receiving phase and ceramic membrane barriers. Sampling rates for PFAS will be determined in laboratory calibration studies.

This proof-of-concept project will provide a crucial first step and strong basis for the development of a new generation of passive sampling technology that can be tailored for both short-term (e.g., weeks) and long-term (e.g., months) quantitative assessment of PFAS to meet the specific needs of different field monitoring activities. Deployment of an improved and robust passive sampling technology can provide a significant advancement for PFAS monitoring and analysis at Department of Defense (DoD) sites, which would facilitate the development of improved and cost-effective PFAS management practices for such sites. Fundamental information also will be obtained on (1) material design for PFAS adsorption and (2) membrane design to control PFAS mass transfer. Because of the widespread presence of PFAS in nature, results will have broader implications on PFAS management in many other PFAS contamination scenarios. (Anticipated Project Completion - 2023)

Min, X. 2021. Silica-Based Materials for Water Treatment Applications: Adsorption and Supported Noble Metal-Based Catalysis (Ph.D. Dissertation). University of Wisconsin, Milwaukee. dc.uwm.edu/etd/2816.