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Surface Chemistry of Almandine Garnet
journal contribution
posted on 2020-02-25, 17:49 authored by Jeffrey Poon, David C. Madden, Mary H. Wood, Ron van Tol, Hans Sonke, Stuart M. ClarkeAlmandine garnet
is used commonly in abrasive blasting processes
to prepare metallic surfaces for painting. However, there is evidence
that the process leads to significant amounts of abrasive embedded
in the “cleaned” surface, and hence the surface chemistry
of garnet will affect the binding of any coatings subsequently applied.
In addition, in marine environments seawater aerosol droplets are
expected to impact the exposed surface prior to coating application,
depositing both water and dissolved inorganic ions. In this work,
we provide in-depth analysis of the chemistry of the almandine garnet
surface using angle-resolved X-ray photoelectron spectroscopy (XPS)
and note a correlation for several elemental oxides between literature
values of the binding energy of the surface oxygen 1s XPS peak and
the basicity of the hydroxyl group that forms on the surface. We also
consider the adsorption to almandine garnet powder of seawater-relevant
inorganic ions (sodium, magnesium, and calcium): Binding constants
have been determined using titration measurements, solution-depletion
isotherms, and numerical modeling, with calcium observed to bind more
strongly than magnesium. The relevance of Langmuir-type fits to constant-pH
adsorption isotherms is discussed. By contrast, sodium either binds
very weakly or is effectively inert toward the garnet surface under
the experimental conditions. The complex adsorption behavior observed
emphasizes the necessity of using multiple techniques to characterize
mineral surfaces.
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marine environments seawater aerosol dropletsbinding energysurface chemistrymineral surfacesgarnet surfaceXPS peakSurface Chemistryangle-resolved X-ray photoelectron spectroscopyhydroxyl groupliterature valuesalmandine garnet surfacealmandine garnet powdertitration measurementssolution-depletion isothermsadsorption behaviorcoating applicationsurface oxygen 1constant-pH adsorption isothermsAlmandine Garnet Almandine garnet
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