The contamination and availability of safe, potable water is a concern affecting individuals globally. Poly- perfluoroalkyl substances (PFAS) are an example of organic contaminants found in public drinking water systems, natural waters systems, wastewaters, and sludge. This contamination dilemma is attributed to the use of PFAS in a variety of applications industrially and commercially, as the waste can contaminate surface and groundwater. PFAS are composed of a hydrophobic fluorinated carbon chain tail and a hydrophilic head group that is typically a carboxylic or sulfonic acid, and thus offer desired surface properties, such as a water and oil repellent. PFAS are utilized in products ranging from surface coatings, fabrics, non-stick cookware, and fire-fighting foams. Although they allow excellent surface properties, PFAS accumulate in water systems over time due to their inability to degrade by natural elements and most, if not all are toxic. Additionally, PFAS are resistive to heat, harsh chemical conditions, and water, therefore, make them difficult to remove with water and wastewater treatment plants. Current methods for the removal of PFAS from contaminated water include absorption using granular activated carbon (GAC), ion exchange resins, and membrane filtration using reverse osmosis (RO) and nanofiltration (NF). However, due to the high energy required and concentrated waste streams produced, as well as the long process time of GAC and ion exchange resins, the use of a porous polymer membrane is a more efficient method of PFAS adsorption. Careful selection of absorber chemistry allows for potential regeneration, unlike GAC and ion exchange resins.
This study investigated using amine modified ultrafiltration (UF) membranes to capture a PFAS mimic. Dodecylbenzenesulfonic acid (DBSA) was used instead of PFAS due to its of concentration detection using UV-Vis spectroscopy. Polyethersulfone (PES) membranes were modified using UV photopolymerization with vinyl amine monomers to create membrane adsorbers. We investigated the use of diallyldimethylammonium chloride (DADMAC), 1-vinylimidazole (1-VM), 2-[methacryloyloxy)ethyl]trimethylammonium chloride (MOETMA), and butyl acrylate (BA) as monomers. These amine polymers interact with the acidic head group of the DBSA molecules leading to adsorption. The membranes were characterized with ATR-FTIR. Static adsorption tests with DBSA were used to determine the adsorption capacity and adsorption kinetics of each membrane. A base rinse was tested to regenerate the adsorption capacity. The initial pH of the feed solution was tested to investigate the effect of solution pH on adsorption capacity. The results of this study indicate that 1-VM is a promising chemistry for PFAS adsorption.
