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DOE OSTI · 1617653

Nonclassical Behavior in Competitive Ion Adsorption at a Charged Solid–Water Interface

Lee, Sang Soo·Park, Changyong·Sturchio, Neil C.·Fenter, Paul
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Abstract

Ion adsorption at solid-water interfaces is commonly described by interactions between specific surface sites and adsorbed ions in classical models. However, energetic contributions from non-site-specific ion-ion interactions have not been explored systematically. Here, we report non-classical behaviors observed during competitive adsorption between Sr 2+ and Na + /Rb + at the negatively-charged muscovite mica (001)-water interface, revealing apparent controls of adsorbed ion speciation over the interfacial reactivity. In the absence of competing cations, Sr 2+ adsorbs in approximately equivalent proportions of inner-sphere and outer-sphere complexes, whereas it adsorbs predominantly as an outer-sphere complex in the presence of Na + /Rb + . This transformation of adsorbed Sr 2+ speciation significantly decreases its adsorption strength, as indicated by ~15-fold shift in the Sr 2+ adsorption edge concentration, compared to that calculated from a classical Langmuir isotherm model developed based on site-specific interactions. Finally, these observations highlight the importance of non-site-specific interactions in controlling the energetics of chemical reactions at the charged interface.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRYadsorption isothermcompetitive adsorptionelectrical double layerion–ion interactionmuscovite micax-ray reflectivity

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Lee, Sang Soo, Park, Changyong, Sturchio, Neil C., Fenter, Paul. 2020-04-15. Nonclassical Behavior in Competitive Ion Adsorption at a Charged Solid–Water Interface. https://doi.org/10.1021/acs.jpclett.0c00808

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