Effect of temperatures and residence time of calcinations on substitution process during enrichment of Tunisian phosphorites

Authors

  • EL Gharbi Sarra
  • Horchani-Naifer Karima
  • Fetteh Nabil
  • Ferid Mokhtar

Abstract

The present study deals with the effects of temperature and residence time of calcinations on substitution process. The upgrading of sedimentary phosphorites coming from the Ras-Dhraa deposit which belongs to the Gafsa-Metlaoui basin (Tunisia) was conducted. The characterization of raw and calcined phosphorites and the evolution of rare earth elements and yttrium (REEs+Y) content and associated gangue were evaluated with different techniques (X-ray powder diffraction (XRD), scanning electron microscopy (SEM/EDX), Fourier transform infrared (FT-IR) and inductively coupled plasma mass spectrometry (ICP-MS)). The effect of increasing residence time and temperature of calcinations on phosphate structure were determined. FT-IR spectroscopy indicates that PO43- was substituted by SiO44- and SO42- and these substitutions cause a worsening of phosphorites properties for sulfuric acid production. A temperature of calcination approximately of 900°C and a period of 30 minutes is sufficient, because higher temperature and longer residence times accentuate these substitutions. Indeed, in these conditions we obtain a phosphate with a better grade of P2O5. It permits to increase the phosphate content from 29.58% to 33.07%. Moreover, REEs+Y contents increased by 5%. 

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Published

2015-10-01

Issue

Vol. 4 No. 5 (2015)

Section

Engineering Chemistry

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