(152ac) Development of Cationic Hydrogels and Hydrogel Composites for Removal of Pfas from Aqueous Systems

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic surfactants developed for various applications and have since accumulated in the environment and within our drinking water as a result of their persistent nature. Legacy PFAS compounds including perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonic acid (PFOS) have been connected to a myriad of harmful health impacts including decreased response to antibodies, dyslipidemia, and increased risks to several types of cancers. The most exercised methods of PFAS remediation treatments within the environment and our water sources include granular activated carbon (GAC) adsorption, separation by reverse osmosis and nanofiltration membrane systems, and binding through ionic interactions between anion exchange resins (AER) and negatively charged PFAS. Although these methods have high sorption capacity, their disadvantages which include lack of selectivity, susceptibility to fouling, and dependency on material properties, create the need for new cost-effective and efficient technologies for PFAS removal. Novel materials based on synthetic sorbents including hydrogels and hydrogel composites have recently gained attention for remediation of these contaminants due to their high-water retention capacity and ease of tunability for increased PFAS affinity. Herein, cationic acrylamide-based hydrogels were synthesized using two cationic co-monomers, N-[3-(dimethylamino)propyl] acrylamide methyl chloride quaternary (DMAPAQ) and diallyldimethylammonium chloride (DADMAC), while composites incorporated two particulates including powdered activated carbon (PAC) and calcium montmorillonite clay within the network. Materials were then characterized to confirm successful polymerization, where physicochemical analysis included Fourier-Transform infrared spectroscopy (FTIR) to discern its chemical composition, thermogravimetric analysis (TGA) to identify varying particulate loading percentage, and aqueous swelling for expansibility behavior. Sorbents were then subject to aqueous sorption studies to determine the affinity of PFOA and PFOS, and two short-chain analytes, perfluorobutanoic acid (PFBA) and perfluorobutanesulfonic acid (PFBS), to compare the impacts in sorption between long-chain and short-chain compounds, as well as measure influence of sulfonic versus carbonic functionality. FTIR confirmed expected functionalization of cationic materials, TGA analysis confirmed the varying concentrations of PAC and clay within the network, and the swelling ratio decreased with increasing crosslinking density and increased with the inclusion of DADMAC and DMAPAQ, as expected. Finally, sorption of PFAS was detected via liquid chromatography tandem mass spectrometry (LM-MS/MS) where binding of PFAS was enhanced with increasing cationic functionality and particulate loading density.