Crystal chemistry of vanadium-bearing ellestadite waste forms

Crystal chemistry of vanadium-bearing ellestadite waste forms

Vanadate ellestadites Ca10(SiO4) x(VO4)6-2 x(SO4) xCl2, serving as prototype crystalline matrices for the fixation of pentavalent toxic metals (V, Cr, As), were synthesized and characterized by powder X-ray and neutron diffraction (PXRD and PND), electron probe microanalysis (EPMA), Fourier transfor...

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Bibliographic Details
Main Authors: Fang, Yanan, Page, Sam J., Rees, Gregory J., Avdeev, Maxim, Hanna, John V., White, Tim J.
Other Authors: School of Materials Science and Engineering
Format: Article
Language:English
Published: 2020
Subjects:
Engineering::Materials
Wastes
Anions
Online Access:https://hdl.handle.net/10356/142691
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Institution: Nanyang Technological University
Language: English
Description
Summary:Vanadate ellestadites Ca10(SiO4) x(VO4)6-2 x(SO4) xCl2, serving as prototype crystalline matrices for the fixation of pentavalent toxic metals (V, Cr, As), were synthesized and characterized by powder X-ray and neutron diffraction (PXRD and PND), electron probe microanalysis (EPMA), Fourier transform infrared spectroscopy (FTIR), and solid-state nuclear magnetic resonance (SS-NMR). The ellestadites 0.19 < x < 3 adopt the P63/ m structure, while the vanadate endmember Ca10(VO4)6Cl2 is triclinic with space group P1̅. A miscibility gap exists for 0.77 < x < 2.44. The deficiency of Cl in the structure leads to short-range disorder in the tunnel. Toxicity characteristic leaching testing (TCLP) showed the incorporation of vanadium increases ellestadite solubility, and defined a waste loading limit that should not exceed 25 atom % V to ensure small release levels.

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