Perfluorooctane sulfonate (PFOS) is one of the persistent organic pollutants (POPs) included in the Stockholm Convention and hard to degrade due to its high stability. The removal of PFOS from an aqueous phase often involves non-specific adsorptions, such as anion exchange and hydrophobic interactions. However, adsorbents, such as activated carbon, zeolites, and sludge do not show any selectivity for PFOS. To enhance the specificity and map interaction mechanisms of PFOS adsorption, two gold nanoparticle (GNP) libraries consisting of 18 members are designed and synthesized with diversified hydrophobic, electrostatic and fluorine-fluorine interaction components for PFOS bindings. The GNPs have an average size of 5.0 nm and are decorated with ligands of various lengths of the poly/perfluoroalkyl chain (for studying of hydrophobic and fluorine-fluorine interaction) and amino groups of various pKa values (for studying of electrostatic interaction). We demonstrate that electrostatic and F-F interactions between PFOS and GNPs are complementary. When F-F attractions are relatively weak, the electrostatic interactions are dominant. As F-F interactions increase, the electrostatic contributions are reduced to as low as 20%. Computational analysis indicates that F-F interactions (28% -79% binding efficiency) are two-fold stronger than regular hydrophobic interactions (15% - 39% binding efficiency) for PFOS adsorption. The conclusion is confirmed by the result that GNPs are superior to the traditional materials, such as granular activated carbon (GAC), powder activated carbon (PAC), and an anion-exchange resin (AI400), in terms of adsorption rate and binding efficiency. The success of this approach opens an avenue for discovering novel binders for pollutants and for mapping complicated interaction mechanisms between pollutants and binding matrices.<br/>

Mapping interaction mechanism of PFOS adsorption by a nanoparticle library approach

256th National Meeting (2018)

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