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Crystal Structures, Surface Stability, and Water Adsorption Energies of La-Bastnäsite via Density Functional Theory and Experimental Studies [electronic resource].

Published:
Washington, D.C. : United States. Dept. of Energy. Office of Energy Efficiency and Renewable Energy, 2016.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
Physical Description:
16,767-16,781 : digital, PDF file
Additional Creators:
Oak Ridge National Laboratory, United States. Department of Energy. Office of Energy Efficiency and Renewable Energy, United States. Department of Energy. Office of Science, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary:
Bastnasite is a fluoro-carbonate mineral that is the largest source of rare earth elements such as Y, La and Ce. With increasing demand for REE in many emerging technologies, there is an urgent need for improving the efficiency of ore beneficiation by froth flotation. In order to design improved flotation agents that can selectively bind to the mineral surface, a fundamental understanding of the bulk and surface properties of bastnasite is essential. Density functional theory calculations using the PBEsol exchange correlation functional and the DFT-D3 dispersion correction reveal that the most stable form of La bastnsite is isomorphic to the structure of Ce bastnasite belonging to the P2c space group, while the Inorganic Crystal Structure Database structure in the P2m space group is ca. 11.3 kJ/mol higher in energy per LaFCO3 formula unit. We report powder X-ray diffraction measurements on synthetic of La bastnasite to support these theoretical findings. Six different surfaces are studied by DFT, namely [100], [0001], [101], [102], [104] and [112]. Among these, the [100] surface is the most stable with a surface energy of 0.73 J/m2 in vacuum and 0.45 J/m2 in aqueous solution. We predicted the shape of a La bastnasite nanoparticle via thermodynamic Wulff construction to be a hexagonal prism with [100] and [0001] facets, chiseled at its ends by the [101] and [102] facets. The average surface energy of the nanoparticle in the gas phase is estimated to be 0.86 J/m2, in good agreement with a value of 1.11 J/m2 measured by calorimetry. The calculated adsorption energy of a water molecule varies widely with the surface plane and specific adsorption sites on a given surface. Moreover, the first layer of water molecules is predicted to adsorb strongly on the La-bastnasite surface, in agreement with water adsorption calorimetry experiments. Our work provides an important step towards a detailed atomistic understanding of the bastnasite water interface and designing collector molecules that can bind specifically to bastnasite.
Report Numbers:
E 1.99:1286987
Subject(s):
Note:
Published through SciTech Connect.
07/11/2016.
Journal of Physical Chemistry. C 120 30 ISSN 1932-7447 AC
Sriram Goverapet Srinivasan; Radha Shivaramaiah; Paul R. C. Kent; Andrew G. Stack; Alexandra Navrotsky; Richard Riman; Andre Anderko; Vyacheslav S. Bryantsev.
Funding Information:
AC05-00OR22725
AC02-05CH11231
AC0500OR22725
View MARC record | catkey: 24055767