(79b) Development of Cationic Hydrogel PAC Composites for Pfas Remediation in Aqueous Solutions

Decades of production of per- and polyfluoroalkyl substances (PFAS), anthropogenic surfactants developed for a plethora of applications, have since plagued the environment as a result of their prevalence and persistent nature. Some PFAS have been connected to a myriad of harmful health impacts including dyslipidemia, birth defects in newborns, and increased risks to several types of cancers. Current treatments for PFAS remediation in the environment and water sources include granular activated carbon (GAC) adsorption, reverse osmosis and nanofiltration membrane separation, and anion exchange resins (AER) with each having advantages and disadvantages (e.g., limited selectivity, cost, etc.). Hence, the need for new cost-effective and efficient technologies for PFAS removal is of utmost importance. Novel materials based synthetic sorbents (i.e., hydrogels and hydrogel composites) have recently gained attention for remediation of these contaminants due to their high-water retention capacity and ability to be functionalized to target PFAS sorption. Herein, acrylamide-based hydrogel composites were synthesized using two cationic co-monomers, N-[3-(dimethylamino)propyl] acrylamide methyl chloride quaternary (DMAPAQ) and diallyldimethylammonium chloride (DADMAC), with powdered activated carbon (PAC) and characterized to determine their affinity for PFAS. Physicochemical characterization included Fourier-Transform infrared spectroscopy (FTIR) to identify chemical compositions, thermogravimetric analysis (TGA) to confirm PAC loading percentages, and aqueous swelling for expansibility behavior. Finally, aqueous sorption studies were performed to determine the affinity of two legacy PFAS compounds, perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonic acid (PFOS), and two short-chain analytes, perfluorobutanoic acid (PFBA) and perfluorobutanesulfonic acid (PFBS) to compare impacts of long-chain and short-chain compounds, as well as sulfonic versus carbonic functionality of PFAS. FTIR confirmed expected functionalization with observation of carbonyl and amine groups, and TGA analysis also confirmed the loading of various concentrations of PAC within the network. Congruently, the swelling ratio decreased with increasing crosslinking density and increased with the inclusion of cationic co-monomers, as expected. Finally, sorption of PFAS was analyzed via liquid chromatography tandem mass spectrometry (LM-MS/MS) where PFAS binding increased with increasing cationic functionality and PAC loading density.