Crystal Chemistry and High-Temperature Behaviour of Ammonium Phases NH4MgCl3 center dot 6H(2)O and (NH4)(2)Fe3+Cl5 center dot H2O from the Burned Dumps of the Chelyabinsk Coal Basin

Andrey A. Zolotarev, Elena S. Zhitova, Maria G. Krzhizhanovskaya, Mikhail A. Rassomakhin, Vladimir V. Shilovskikh, Sergey V. Krivovichev

Research output

Abstract

The technogenic mineral phases NH4MgCl3 center dot 6H(2)O and (NH4)(2)Fe3+Cl5 center dot H2O from the burned dumps of the Chelyabinsk coal basin have been investigated by single-crystal X-ray diffraction, scanning electron microscopy and high-temperature powder X-ray diffraction. The NH4MgCl3 center dot 6H(2)O phase is monoclinic, space group C2/c, unit cell parameters a = 9.3091(9), b = 9.5353(7), c = 13.2941(12) angstrom, beta = 90.089(8)degrees and V = 1180.05(18) angstrom(3). The crystal structure of NH4MgCl3 center dot 6H(2)O was refined to R-1 = 0.078 (wR(2) = 0.185) on the basis of 1678 unique reflections. The (NH4)(2)Fe3+Cl5 center dot H2O phase is orthorhombic, space group Pnma, unit cell parameters a = 13.725(2), b = 9.9365(16), c = 7.0370(11) angstrom and V = 959.7(3) angstrom(3). The crystal structure of (NH4)(2)Fe3+Cl5 center dot H2O was refined to R-1 = 0.023 (wR(2) = 0.066) on the basis of 2256 unique reflections. NH4MgCl3 center dot 6H(2)O is stable up to 90 degrees C and then transforms to the less hydrated phase isotypic to beta-Rb(MnCl3)(H2O)(2) (i.e., NH4MgCl3 center dot 2H(2)O), the latter phase being stable up to 150 degrees C. (NH4)(2)Fe3+Cl5 center dot H2O is stable up to 120 degrees C and then transforms to an X-ray amorphous phase. Hydrogen bonds provide an important linkage between the main structural units and play the key role in determining structural stability and physical properties of the studied phases. The mineral phases NH4MgCl3 center dot 6H(2)O and (NH4)(2)Fe3+Cl5 center dot H2O are isostructural with natural minerals novograblenovite and kremersite, respectively.

Original languageEnglish
Article number486
Pages (from-to)486
Number of pages16
JournalMinerals
Volume9
Issue number8
DOIs
Publication statusPublished - 14 Aug 2019

Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geology

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