(321f) Chemically Modular Polymers for PFAS Remediation

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals that exhibit high thermal and chemical stability, rendering them valuable in various applications like non-stick coating, water-resistant clothes, cosmetics, paints, firefighting foam, etc. Unfortunately, these compounds are also known to bioaccumulate and exhibit long-term toxicity. PFAS are divided into major categories based on the structural differences of carbon chain and cationic head groups. Moreover, these compounds are known to transform into other PFAS compounds creating thousands of different PFAS. Two of the most ubiquitous PFAS are PFOA and PFOS that contain 8 carbon chain and a carboxylic and sulfonic head group, respectively.

In recent years, researchers have explored various methods for PFAS remediation, including activated carbon, ion-exchange resins, advanced oxidation processes, and filtration membranes. However, there remains a deficiency in adsorbents capable of effectively removing both long and short-chain PFAS compounds at environmentally relevant concentrations. While certain commercial sorption media exhibit efficiency in PFAS removal, they often suffer from drawbacks such as slow uptake kinetics and low sorption removal percentages for short chain PFAS.

To overcome these shortcomings of sorption media, we have developed chemically tunable polymer hydrogels that can effectively capture short and long-chain PFAS from aqueous media. These hydrogels are synthesized from poly (ethylene glycol) diacrylate and different monomer units of poly (ethylene glycol) methyl ether acrylate (PEGMEA), dodecyl acrylate, and pentafluoro phenyl acrylate (PFPA). Using active ester ‘click chemistry’, we can efficiently post-functionalize these polymers with Lewis base ligands by substituting PFPA groups in the networks. These ligands provide tunable acid-base interactions with anionic PFAS head groups. Quantification of the sorption efficiency and sorption isotherms has been performed using liquid chromatography-mass spectroscopy (LC-MS), with functionalized hydrogels showing as high as ~99% removal of PFOA from aqueous solutions. Sorption efficiency is further observed to be a function of the basicity of the grafted ligands. This chemically tunable approach will ultimately enable future structure-property studies for development of efficient polymer sorbents for PFAS remediation from surface and groundwater.