Leaching of calcined phosphate ore particles with phosphoric and acetic acid solutions at 25°C : kinetic curves and related textural changes

Abstract : The reactivity of calcined Tunisian phosphate ore was studied in both phosphoric and acetic solutions. Phase analysis from X-ray diffraction and IR absorption data indicate that carbonate apatite, or francolite, and fluorapatite are the main phases. However, it was observed that the calcium oxide phase, evident at the most intense peak (d=2.401Å401˚401Å;2θ= 37.42 •) and at the adsorbant band at around 700 cm −1 disappeared or were weakly defined for the solid leached in acetic medium. Nitrogen adsorption-desorption analysis shows a rising of mesopores at the surface of the leached particles and then an increase of their specific surface area, SBET. The scanning electron microscope micrographs of the particles and their size distribution show a constancy of their outer dimensions during attack.