Didenko Tatiana, Lau Almond, Purohit Anmol L, Feng Ji, Pinkard Brian, Ateia Mohamed, Novosselov Igor V
University of Washington, Mechanical Engineering Department, Seattle, WA, 98195, USA.
University of Washington, Mechanical Engineering Department, Seattle, WA, 98195, USA.
Chemosphere. 2025 Feb;370:143986. doi: 10.1016/j.chemosphere.2024.143986. Epub 2024 Dec 23.
Granular activated carbon (GAC) is widely used to treat contaminated per- and polyfluoroalkyl substances (PFAS) waste streams, resulting in the accumulation of large quantities of spent GAC that need to be landfilled or regenerated. A novel modified supercritical CO (scCO) extraction for regeneration of spent GAC is developed. With the addition of organic solvents and acid modifiers, the procedure yielded >99% perfluorooctanoic acid (PFOA) desorption after a 60-min treatment in a continuous flow reactor. The mild extraction conditions at T ∼100 °C do not trigger the formation of volatile organic fluorine or changes in GAC sorbent properties. Mechanistically, the high miscibility of co-solvent/scCO eliminates diffusion transport limitations, enabling rapid reagent and PFAS transport in a single-phase (gas-like) medium. The introduction of organic co-solvent and the absence of water reverses hydrophobic interactions between GAC and the PFAS. The acid modifier minimizes the electrostatic PFOA/GAC interactions by protonating the perfluorooctanoate ion and providing competition for active GAC sites. The approach offers an economically effective regeneration scheme, enabling the reuse of sorbents and yielding effluent with a high loading of PFAS that is amenable to subsequent end-of-life treatment technologies.
颗粒活性炭（GAC）被广泛用于处理受污染的全氟和多氟烷基物质（PFAS）废物流，导致大量废GAC的积累，这些废GAC需要填埋或再生。开发了一种用于再生废GAC的新型改性超临界CO（scCO）萃取方法。通过添加有机溶剂和酸改性剂，在连续流动反应器中处理60分钟后，该方法的全氟辛酸（PFOA）解吸率>99%。在T ∼100 °C的温和萃取条件下，不会引发挥发性有机氟的形成或GAC吸附剂性能的变化。从机理上讲，助溶剂/scCO的高混溶性消除了扩散传输限制，使试剂和PFAS能够在单相（类气体）介质中快速传输。有机助溶剂的引入和水的缺失逆转了GAC与PFAS之间的疏水相互作用。酸改性剂通过使全氟辛酸根离子质子化并竞争GAC活性位点，将静电PFOA/GAC相互作用降至最低。该方法提供了一种经济有效的再生方案，能够使吸附剂重复使用，并产生高负载PFAS的流出物，便于后续的终末处理技术。
