T199 Beneath Da Vinci’s Feet: The Multidisciplinary World of Soil Science

Tuesday, 27 September 2016
8:00 AM - 12:00 PM
Room 402

DENSITY FUNCTIONAL THEORY MODELING OF FERRIHYDRITE NANOPARTICLE OXYANION ADSORPTION

Paper number: T199-12
Program: Technical Sessions
Time: 10:45 AM – 11:00 AM

Authors

Abstract

Ferrihydrite is a critical substrate for adsorption of oxyanion species in the environment1. The nanoparticulate nature of ferrihydrite is inherent to its formation, and hence it has been called a “nano-mineral”2. The nano-scale size and unusual composition of ferrihydrite has made structural determination of this phase problematic. Michel et al.3 have proposed an atomic structure for ferrihydrite, but this model has been controversial4,5. Recent work has shown that the Michel et al.3 model structure may be reasonably accurate despite some deficiencies6-8. An alternative model has been proposed by Manceau9.

This work utilizes density functional theory (DFT) calculations to model both the structure of ferrihydrite nanoparticles based on the Michel et al. 3 model as refined in Hiemstra8 and the modified akdalaite model of Manceau9. Adsorption energies of carbonate, phosphate, sulfate, chromate, arsenite and arsenate are calculated. Periodic projector-augmented planewave calculations were performed with the Vienna Ab-initio Simulation Package (VASP10) on an approximately 1.7 nm diameter Michel nanoparticle (Fe38O112H110) and on a 2 nm Manceau nanoparticle (Fe38O95H76). After energy minimization of the surface H and O atoms. The model will be used to assess the possible configurations of adsorbed oxyanions on the model nanoparticles.

  1. Brown G.E. Jr. and Calas G. (2012) Geochemical Perspectives, 1, 483-742.
  2. Hochella M.F. and Madden A.S. (2005) Elements, 1, 199-203.
  3. Michel, F.M., Ehm, L., Antao, S.M., Lee, P.L., Chupas, P.J., Liu, G., Strongin, D.R., Schoonen, M.A.A., Phillips, B.L., and Parise, J.B., 2007, Science, 316, 1726-1729.
  4. Rancourt, D.G., and Meunier, J.F., 2008, American Mineralogist, 93, 1412-1417.
  5. Manceau, A., 2011, American Mineralogist, 96, 521-533.
  6. Maillot, F., Morin, G., Wang, Y., Bonnin, D., Ildefonse, P., Chaneac, C., Calas, G., 2011, Geochimica et Cosmochimica Acta, 75, 2708-2720.
  7. Pinney, N., Kubicki, J.D., Middlemiss, D.S., Grey, C.P., and Morgan, D., 2009, Chemistry of Materials, 21, 5727-5742.
  8. Hiemstra T. (2013) Geochimica et Cosmochimica Acta, 105, 316-325.
  9. Manceau A. (2014) American Mineralogist, 99, 102-108.
  10. Kresse, G., and Furthmuller, J., 1996, Physical Review B, 54, 11169-11186.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-281499

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