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Title: Concerted Metal Cation Desorption and Proton Transfer on Deprotonated Silica Surfaces

Abstract

The adsorption equilibrium constants of monovalent and divalent cations to material surfaces in aqueous media are central to many technological, natural, and geochemical processes. Cation adsorption–desorption is often proposed to occur in concert with proton transfer on hydroxyl-covered mineral surfaces, but to date this cooperative effect has been inferred indirectly. This work applies density functional theory-based molecular dynamics simulations of explicit liquid water/mineral interfaces to calculate metal ion desorption free energies. Monodentate adsorption of Na +, Mg 2+, and Cu 2+ on partially deprotonated silica surfaces are considered. Na + is predicted to be unbound, while Cu 2+ exhibits binding free energies to surface SiO groups that are larger than those of Mg 2+. The predicted trends agree with competitive adsorption measurements on fumed silica surfaces. As desorption proceeds, Cu 2+ dissociates one of the H 2O molecules in its first solvation shell, turning into Cu 2+(OH )(H 2O) 3, while Mg remains Mg 2+(H 2O) 6. The protonation state of the SiO– group at the initial binding site does not vary monotonically with cation desorption

Authors:
ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1473940
Report Number(s):
SAND-2018-10050J
Journal ID: ISSN 1948-7185; 667842
Grant/Contract Number:  
AC04-94AL85000
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry Letters
Additional Journal Information:
Journal Volume: 9; Journal Issue: 18; Journal ID: ISSN 1948-7185
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Leung, Kevin, Criscenti, Louise J., Knight, Andrew W., Ilgen, Anastasia G., Ho, Tuan A., and Greathouse, Jeffery A. Concerted Metal Cation Desorption and Proton Transfer on Deprotonated Silica Surfaces. United States: N. p., 2018. Web. doi:10.1021/acs.jpclett.8b02173.
Leung, Kevin, Criscenti, Louise J., Knight, Andrew W., Ilgen, Anastasia G., Ho, Tuan A., & Greathouse, Jeffery A. Concerted Metal Cation Desorption and Proton Transfer on Deprotonated Silica Surfaces. United States. doi:10.1021/acs.jpclett.8b02173.
Leung, Kevin, Criscenti, Louise J., Knight, Andrew W., Ilgen, Anastasia G., Ho, Tuan A., and Greathouse, Jeffery A. Fri . "Concerted Metal Cation Desorption and Proton Transfer on Deprotonated Silica Surfaces". United States. doi:10.1021/acs.jpclett.8b02173. https://www.osti.gov/servlets/purl/1473940.
@article{osti_1473940,
title = {Concerted Metal Cation Desorption and Proton Transfer on Deprotonated Silica Surfaces},
author = {Leung, Kevin and Criscenti, Louise J. and Knight, Andrew W. and Ilgen, Anastasia G. and Ho, Tuan A. and Greathouse, Jeffery A.},
abstractNote = {The adsorption equilibrium constants of monovalent and divalent cations to material surfaces in aqueous media are central to many technological, natural, and geochemical processes. Cation adsorption–desorption is often proposed to occur in concert with proton transfer on hydroxyl-covered mineral surfaces, but to date this cooperative effect has been inferred indirectly. This work applies density functional theory-based molecular dynamics simulations of explicit liquid water/mineral interfaces to calculate metal ion desorption free energies. Monodentate adsorption of Na+, Mg2+, and Cu2+ on partially deprotonated silica surfaces are considered. Na+ is predicted to be unbound, while Cu2+ exhibits binding free energies to surface SiO– groups that are larger than those of Mg2+. The predicted trends agree with competitive adsorption measurements on fumed silica surfaces. As desorption proceeds, Cu2+ dissociates one of the H2O molecules in its first solvation shell, turning into Cu2+(OH–)(H2O)3, while Mg remains Mg2+(H2O)6. The protonation state of the SiO– group at the initial binding site does not vary monotonically with cation desorption},
doi = {10.1021/acs.jpclett.8b02173},
journal = {Journal of Physical Chemistry Letters},
number = 18,
volume = 9,
place = {United States},
year = {2018},
month = {8}
}

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