Thermal transformations in phosphorites |
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Authors: | R Knubovets Y Nathan S Shoval J Rabinowitz |
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Institution: | (1) The Open University of Israel, 16 Klausner St., 61392 Tel-Aviv;(2) Geological Survey of Israel, 95501 Jerusalem;(3) Rotem-Amfert-Negev, 77051 Ashdod, Israel |
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Abstract: | 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 PO
4
–3
in apatite by SO
4
–2
and SiO
4
–4
may take place.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthdayThe financial support from Rotem-Amfert-Negev Phosphate Co. is gratefully acknowledged. We thank Dr. B. Pregerson of the Rotem-Amfert-Negev for supplying samples |
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Keywords: | apatite calcination crystallinity FT-IR phosphorite XRD |
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