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Minerals 2018, 8(3), 91; https://doi.org/10.3390/min8030091

Density Functional Theory Study of Arsenate Adsorption onto Alumina Surfaces

Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA
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Received: 1 February 2018 / Revised: 23 February 2018 / Accepted: 23 February 2018 / Published: 1 March 2018
(This article belongs to the Special Issue Molecular Simulation of Mineral-Solution Interfaces)
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Abstract

Atomistic modeling of mineral–water interfaces offers a way of confirming (or refuting) experimental information about structure and reactivity. Molecular-level understanding, such as orbital-based descriptions of bonding, can be developed from charge density and electronic structure analysis. First-principles calculations can be used to identify weaknesses in empirical models. This provides direction on how to propose more robust representations of systems of increasing size that accurately represent the underlying physical factors governing reactivity. In this study, inner-sphere complex geometries of arsenate on hydrated alumina surfaces are modeled at the density functional theory (DFT)–continuum solvent level. According to experimental studies, arsenate binds to alumina surfaces in a bidentate binuclear (BB) fashion. While the DFT calculations support the preference of the BB configuration, the optimized geometries show distortion from the ideal tetrahedral geometry of the arsenic atom. This finding suggests that steric factors, and not just coordination arguments, influences reactivity. The Osurf–As–Osurf angle for the more favorable arsenate configurations is closest to the ideal tetrahedral angle of 109.5°. Comparing the results of arsenate adsorption using a small cluster model with a periodic slab model, we report that the two model geometries yield results that differ qualitatively and quantitatively. This relates the steric factors and rigidity of the surface models. View Full-Text
Keywords: adsorption; arsenate contamination; computer simulations; DFT; mineral–solution interfaces adsorption; arsenate contamination; computer simulations; DFT; mineral–solution interfaces
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Corum, K.W.; Abbaspour Tamijani, A.; Mason, S.E. Density Functional Theory Study of Arsenate Adsorption onto Alumina Surfaces. Minerals 2018, 8, 91.

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