1000-Fold Preconcentration of Per- and Polyfluorinated Alkyl Substances within 10 Minutes via Electrochemical Aerosol Formation

Abstract

We present a simple and efficient method for preconcentrating per- and polyfluorinated alkyl substances (PFAS) in water. Our method was inspired by the sea-spray aerosol enrichment in nature. Gas bubbles in the ocean serve to scavenge surface active material, carrying it to the air-ocean interface, where the bubbles burst and form a sea-spray aerosol. These aerosol particles are enriched in surface-active organic compounds such as free fatty acids and anionic surfactants. In our method, we in situ generate H2 microbubbles by electrochemical water reduction using a porous Ni foam electrode. These H2 bubbles pick up PFAS as they rise through the water column that contains low concentration PFAS. When these bubbles reach the water surface, they burst and produce aerosol droplets that are enriched in PFAS. Using this method, we demonstrated ∼1000-fold preconcentration for ten common PFAS in the concentration range from 1 pM to 1 nM (or ∼0.5 ng/L to 500 ng/L) in 10 min. We also developed a diffusion-limited adsorption model that is in quantitative agreement with the experimental data. In addition, we demonstrated using this method to preconcentrate PFAS in tap water, indicating its potential use for quantitative analysis of PFAS in real-world water samples.

Aqueous Film-Forming Foams Exhibit Greater Interfacial Activity than PFOA, PFOS, or FOSA

“…Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are water-soluble substances that spontaneously concentrate at the air–water interface . The rapid transfer of PFOA or PFOS from bulk water to air–water interfaces can be used to remove or degrade these substances and also has implications for their fate and transport in the environment.…”

“…Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are water-soluble substances that spontaneously concentrate at the air−water interface. 1 The rapid transfer of PFOA or PFOS from bulk water to air−water interfaces can be used to remove 2 or degrade 3 these substances and also has implications for their fate and transport in the environment. For example, the mass of PFOA concentrated at the air−water interface, rather than adsorbed to solids, was reported to be a major sink for the retention of PFOA in flow-through columns containing quartz sand, with water saturations ranging from 0.68 to 0.86.…”

Selectivity of Per- and Polyfluoroalkyl Substance Sensors and Sorbents in Water

“…They achieved 1000-fold enrichment of 10 common PFAS in 10 min at the concentration range of pM to nM. 70 While the pretreatment method is improving, how to integrate it with the sensing device and how to optimize the process for on-site use are also important considerations. Selectivity is another key issue to be addressed in order to achieve practical application.…”

“…Recently, Cao et al invented a rapid and convenient preconcentration method based on electrochemical aerosol formation. They achieved 1000-fold enrichment of 10 common PFAS in 10 min at the concentration range of pM to nM . While the pretreatment method is improving, how to integrate it with the sensing device and how to optimize the process for on-site use are also important considerations.…”

Rapid detection of perfluorinated sulfonic acids through preconcentration by bubble bursting and surface‐assisted laser desorption/ionization

“…The amino acids in the collected aerosols were enhanced 10‐ to 100‐fold. In a 2019 study by Cao, et al 15 perfluorinated and polyfluoroalkyl substances were enriched 1000‐fold after preconcentration, resulting in electrochemical aerosols. The process was as follows: hydrogen microbubbles were produced from nickel electrodes in electrochemical water.…”