Thermal transformations in phosphorites

R. Knubovets, Y. Nathan, S. Shoval, J. Rabinowitz

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The thermal transformations in phosphorites during flash calcination were investigated by FT-IR spectroscopy, X-ray diffraction and chemical analyses. During flash calcination changes occur, both in the composition of the phosphorite and in the crystallochemistry of the fluor-carbonate-apatite (francolite). The former changes include: decomposition of a great part of the calcite in the rock and oxidation of organic matter. The latter changes include: partial removal of the structural carbonate; partial relocation of the remaining carbonate ions in the apatite structure; a new arrangement of hydroxyl groups and fluorine on the hexagonal axis; partial condensation of the orthophosphate groups and increase of crystallite sizes. Isomorphous substitution of PO4-3 in apatite by SO4-2 and SiO4-4 may take place.

Original languageEnglish
Pages (from-to)229-239
Number of pages11
JournalJournal of Thermal Analysis
Issue number1-2
StatePublished - 1997


  • Apatite
  • Calcination
  • Crystallinity
  • FT-IR
  • Phosphorite
  • XRD


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