Conventionally employed technologies like activated carbon adsorption might fall short in meeting the new US EPA standard, due to its limited efficacy for removing short-chain compounds like HFPO-DA, PFHxS, and PFBS. Reverse osmosis and ion exchange technologies are more successful in removing short-chain compounds but are challenged by large amounts of highly contaminated concentrate (e.g., 15-30% of all treated water for reverse osmosis) or solid wastes (spent ion exchange resins). All above systems are furthermore characterized by limited suitability for end users at commercial level, due to their complex operations, large footprints, short adsorption media lifetime, and hazardous waste generation.
The physicochemical characteristics of PFAS molecules render them highly persistent and mobile, and the PFAS plumes are large, so meeting cleanup goals of extremely low concentration levels (ppt) using cost-effective industrial adoptable strategies is arduous. For ex-situ removal, an effective strategy to separate/sequester PFAS from contaminated water relies on adsorbent technologies such as granular activated carbon (GAC), powdered activated carbon, ion exchange resin, molecularly imprinted polymers, and mineral materials. While many adsorbents and resins are effective, maintaining cost-effectiveness with GAC is a significant challenge. In all cases, managing regeneration, reuse, and disposal of adsorbents is essential for any closed-loop treatment train. In addition, producing highly concentrated waste streams can be costly and impractical for large scale applications.
Electrochemical adsorbent-wafer separation technology (EAST) is an Argonne proprietary technology platform that provides electrochemical adsorption/desorption simultaneously to separate/extract target ions from the feed liquid and collect/concentrate in separate recycled stream. The advantages of EAST over currently employed removal technologies (e.g., granular activated carbon, conventional ion exchange, or membrane filtration) include (i) high efficiency for both long- and short-chain PFAS, (ii) in-situ adsorbent regeneration for stable performance with no need for ex-situ regeneration/disposal, and (iii) minimal concentrate PFAS capture stream of less than 1% of all treated water.
The process cost and performance in demonstrating >99.7% removal of long and short acids of perfluorooctanoic acid (PFOA) and perfluorobutane sulfonic acid (PFBS) will be discussed in the presentation.