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Title: Lead and selenite adsorption at water–goethite interfaces from first principles

Abstract

Here, the complexation of toxic and/or radioactive ions on to mineral surfaces is an important topic in geochemistry. We apply periodic-boundary-conditions density functional theory (DFT) molecular dynamics simulations to examine the coordination of Pb(II), $${\rm SeO}_3^{2-}$$ , and their contact ion pairs to goethite (1 0 1) and (2 1 0) surfaces. The multitude of Pb(II) adsorption sites and possibility of Pb(II)-induced FeOH deprotonation make this a complex problem. At surface sites where Pb(II) is coordinated to three FeO and/or FeOH groups, and with judicious choices of FeOH surface group protonation states, the predicted Fe–Pb distances are in good agreement with EXAFS measurements. Trajectories where Pb(II) is in part coordinated to only two surface Fe–O groups exhibit larger fluctuations in Pb–O distances. Pb(II)/$${\rm SeO}_3^{2-}$$ contact ion pairs are at least metastable on goethite (2 1 0) surfaces if the $${\rm SeO}_3^{2-}$$ has a monodentate Se–O–Fe bond. Our DFT-based molecular dynamics calculations are a prerequisite for calculations of finite temperature equilibrium binding constants of Pb(II) and Pb(II)/$${\rm SeO}_3^{2-}$$ ion pairs to goethite adsorption sites.

Authors:
 [1];  [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:
1406368
Report Number(s):
SAND-2017-11359J
Journal ID: ISSN 0953-8984; 657957; TRN: US1703132
Grant/Contract Number:
AC04-94AL85000
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physics. Condensed Matter
Additional Journal Information:
Journal Volume: 29; Journal Issue: 36; Journal ID: ISSN 0953-8984
Publisher:
IOP Publishing
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; density functional theory molecular dynamics; water-material interface; ion adsorption; deprotonation

Citation Formats

Leung, Kevin, and Criscenti, Louise J. Lead and selenite adsorption at water–goethite interfaces from first principles. United States: N. p., 2017. Web. doi:10.1088/1361-648x/aa7e4f.
Leung, Kevin, & Criscenti, Louise J. Lead and selenite adsorption at water–goethite interfaces from first principles. United States. doi:10.1088/1361-648x/aa7e4f.
Leung, Kevin, and Criscenti, Louise J. 2017. "Lead and selenite adsorption at water–goethite interfaces from first principles". United States. doi:10.1088/1361-648x/aa7e4f.
@article{osti_1406368,
title = {Lead and selenite adsorption at water–goethite interfaces from first principles},
author = {Leung, Kevin and Criscenti, Louise J.},
abstractNote = {Here, the complexation of toxic and/or radioactive ions on to mineral surfaces is an important topic in geochemistry. We apply periodic-boundary-conditions density functional theory (DFT) molecular dynamics simulations to examine the coordination of Pb(II), ${\rm SeO}_3^{2-}$ , and their contact ion pairs to goethite (1 0 1) and (2 1 0) surfaces. The multitude of Pb(II) adsorption sites and possibility of Pb(II)-induced FeOH deprotonation make this a complex problem. At surface sites where Pb(II) is coordinated to three FeO and/or FeOH groups, and with judicious choices of FeOH surface group protonation states, the predicted Fe–Pb distances are in good agreement with EXAFS measurements. Trajectories where Pb(II) is in part coordinated to only two surface Fe–O groups exhibit larger fluctuations in Pb–O distances. Pb(II)/${\rm SeO}_3^{2-}$ contact ion pairs are at least metastable on goethite (2 1 0) surfaces if the ${\rm SeO}_3^{2-}$ has a monodentate Se–O–Fe bond. Our DFT-based molecular dynamics calculations are a prerequisite for calculations of finite temperature equilibrium binding constants of Pb(II) and Pb(II)/${\rm SeO}_3^{2-}$ ion pairs to goethite adsorption sites.},
doi = {10.1088/1361-648x/aa7e4f},
journal = {Journal of Physics. Condensed Matter},
number = 36,
volume = 29,
place = {United States},
year = 2017,
month = 8
}

Journal Article:
Free Publicly Available Full Text
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  • Abstract not provided.
  • Kinetics and mechanisms of selenate and selenite adsorption/desorption at the goethite/water interface were studied by using pressure-jump (p-jump) relaxation with conductivity detection at 298.15 K. A single relaxation was ascribed to SeO{sub 4}{sup 2{minus}} on a surface site through electrostatic attraction accompanied simultaneously by a protonation process. The intrinsic rate constant for adsorption (log k{sub 1}{sup int} = 8.55) was much larger than that for desorption (log k{sub 1{minus}}{sup int} = 0.52). The intrinsic equilibrium constant obtained from the kinetic study (log K{sub kinetic}{sup int} = 8.02) was of the same order of magnitude as that obtained from the equilibriummore » study (log K{sub model}{sup int} = 8.65). Unlike SeO{sub 4}{sup 2{minus}}, selenite adsorption on goethite produced two types of complexes, XHSeO{sub 3}{sup 0} and XSeO{sub 3}{sup {minus}}, via a ligand-exchange mechanism. Double relaxations were attributed to two reaction steps. The first step was the formation of an outer-sphere surface complex through electrostatic attraction. In the second step, the adsorbed selenite ion replaced a H{sub 2}O from the protonated surface hydroxyl group and formed an inner-sphere surface complex.« less
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