Lead and selenite adsorption at water–goethite interfaces from first principles. (4th August 2017)

• Record Type: Journal Article
• Authors: Leung, Kevin; Criscenti, Louise J
• Is Part Of: Journal of physics. Volume 29:Number 36(2017)
• Publication Date: 2017-08-04
• Subjects: density functional theory molecular dynamics -- water-material interface -- ion Adsorption -- deprotonation; Condensed matter -- Periodicals; Matière condensée -- Périodiques; Vaste stoffen; Vloeistoffen; Natuurkunde; Electronic journals; Computer network resources; 530.4105
• DOI: 10.1088/1361-648X/aa7e4f
• Languages: English
• ISSNs: 0953-8984

Abstract

Abstract: 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), S e O 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)/ S e O 3 2 − contact ion pairs are at least metastable on goethite (2 1 0) surfaces if the S e O 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)/ S e O 3 2 − ion pairs to goethite adsorption sites.