The thermal behavior of Tunisian phosphorite was investigated with X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR), and Raman spectroscopies and DTA-TG measurements. The XRD patterns showed that the chief mineral constituents of calcined samples are calcium oxide and fluorapatite, while those in the raw phosphorite are calcite, dolomite, fluorapatite, and carbonate-fluorapatite. Physicochemical transformations result in the oxidation of organic matter, disappearance of calcite and dolomite crystalline phases, and partial dissociation of structural carbonates. The FT-IR and Raman spectra showed modifications of some bands; a decrease in the intensity of the v 2 and v 3 vibrations of carbonate groups and the appearance of new bands at 520 and 926 cm -1 after calcination of phosphorites at 800°C. These bands were assigned to isomorphous substitutions of PO 4 3-in apatite by SiO 4 4-. Heat treatment alters the qualitative composition of the mineral as a result; the solubility of apatite in dilute citric acid was decreased.

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The proposal of a method for converting the phosphogypsum waste (PG) remains the focus of many researchers since its quantity, growing considerably, is causing serious environmental problems.