The interactions of Al(III), La(III), and Sc(III) with the muscovite-water interface were investigated using second harmonic generation (SHG), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). The SHG non-resonant ?3 technique, when paired with the Gouy-Chapman model, provides real-time information regarding the change in interfacial potential as a result of the interactions of metal species interacting with the muscovite surface and elucidates the reversibility of these interactions. In instances where precipitation reactions occur at the muscovite surface deposits were characterized by XPS and EDS. Our SHG results suggest that Sc(III) binds irreversibly to the muscovite surface forming Sc2O3 and/or ScOOH deposits as confirmed by XPS. An EDS analysis of the surface revealed that these deposits are evenly dispersed across the mineral surface. La(III) adsorption to the muscovite surface is partially reversible, and after increased exposure of the muscovite surface the formation of La2O3 deposits were detected. Finally, Al(III) adsorption traces showed drastic changes in the interfacial potential with increasing Al(III) concentration in solution that suggest, along with previous studies that gibbsite (Al(OH)3) growth occurs on the muscovite surface. To our knowledge this is the first study to observe the growth of La(III) and Sc(III) (hydr)oxides on the muscovite surface, i.e. the conversion of a mica mineral to an amphoteric oxide, and exemplifies the need for investigating and accounting for heterogeneous mineral surfaces when predicting the fate and transport of metal contaminants.

Al(III), La(III), and Sc(III) adsorption at the muscovite-water interface studied by second harmonic generation, XPS, and EDS

248th National Meeting (2014)

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