Density Functional Theory Study of Leaching Performance of Different Acids on Pyrochlore (100) Surface
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Pyrochlore leaching using hydrofluoric, sulfuric, and hydrochloric acids has been studied via experimental methods for years, but the interactions between niobium atoms on the pyrochlore surface and different acids have not been investigated. In this work, first-principles calculations based on density functional theory were used to elucidate the leaching performance of these three acids from the viewpoint of geometrical and electronic structures. The calculation results indicate that sulfate, chloride, and fluoride anions influence the geometric structure of pyrochlore (100) to different extents, decreasing in the order: sulfate, fluoride, chloride. Orbitals of O1 and O2 atoms of sulfate hybridized with those of surface niobium atom. Fluorine orbitals hybridized with those of surface niobium atoms. However, no obvious overlap exists between any orbitals of chlorine and surface niobium, revealing that chlorine does not interact chemically with surface niobium atoms.
This work was supported financially by the project of the National Natural Science Foundation of China (No. 51504105), projects of the Science Foundation of Jiangxi Province (Nos. 20161BAB216127, GJJ160673, 20171BBB206023), projects of the Scientific Research Foundation and of Jiangxi University of Science and Technology (Nos. NSFJ2014-G01, JXXJBS13022), and Program for Excellent Young Talents of Jiangxi University of Science and Technology.