Effects of surface structural disorder and surface coverage on isotopic fractionation during Zn(II) adsorption onto quartz and amorphous silica surfaces

Metal ion-mineral surface interactions and the attendant isotopic fractionation depend on the properties of the mineral surface and the local atomic-level chemical environment. However, these factors have not been systematically examined for phases of the same composition with different levels of su...

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Bibliographic Details
Published in:Geochimica et cosmochimica acta 2017-10, Vol.215 (C), p.354-376
Main Authors: Nelson, Joey, Wasylenki, Laura, Bargar, John R., Brown, Gordon E., Maher, Kate
Format: Article
Language:English
Subjects:
Adsorption
Amorphous silica
GEOSCIENCES
Isotope fractionation
Quartz
Surface coverage
Surface structural disorder
Zinc
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Summary:Metal ion-mineral surface interactions and the attendant isotopic fractionation depend on the properties of the mineral surface and the local atomic-level chemical environment. However, these factors have not been systematically examined for phases of the same composition with different levels of surface disorder. We present pH-dependent adsorption edges, X-ray absorption spectra, and isotopic measurements to illustrate the effects of surface structural disorder and surface coverage on zinc(II) (Zn(II)) surface complexation and isotope fractionation. Our results demonstrate that Zn(II) surface complexes on quartz and amorphous silica (SiO2(am)) transition from octahedral to tetrahedral coordination by oxygen as surface coverage increases. In low ionic strength solutions (I=0.004M) and at low surface loadings (Γ
ISSN:0016-7037
1872-9533
DOI:10.1016/j.gca.2017.08.003