Investigation of the structural and mineralogical changes of Tunisian phosphorite during calcinations

Abstract

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.

Effect of the calcinations temperatures of phosphate washing waste on the structural and mechanical properties of geopolymeric mortar

“…It extracts an average of about 8 million of rocks in recent years [7]. Tunisian phosphate ore is composed by fluorapatite, silica, carbonate (calcite), gypsum, organic and aluminosilicates materials [7][8][9]. This ore is used in the production of phosphoric acid and as fertilizer to be used in agriculture and other fields [10].…”

Raman Spectroscopy Study of Phosphorites Combined with PCA-HCA and OPLS-DA Models

“…The peak near 1100 cm −1 corresponds to the C-O vibration of dolomite CaMg(CO 3 ) 2 [23]. The two peaks near 1340 cm −1 and 1445 cm −1 are disordered carbon D bands, and the peak near 1580 cm −1 corresponds to disordered carbon G bands [21,23]. The peak near 300 cm −1 belongs to hematite [28].…”

“…Apatite Ca 5 (PO 4 ) 3 (F, Cl, and OH) is the main mineral containing phosphorus in phosphorite [23]. PO 4 3− is a tetrahedral pentaatomic group with four vibrational modes, namely, symmetrical stretching vibration (V 1 ), double degenerate bending vibration (V 2 ), triple nonsymmetrical stretching vibration (V 3 ), and triple degenerate bending vibration (V 4 ) [20,21,23]. In Figure 1a, the strong peak near 960 cm −1 belongs to the V 1 mode; the weak peak near 430 cm −1 can be assigned to the V 2 mode; the weak peaks near 1035 cm −1 and 1050 cm −1 correspond to the V 3 modes; and the weak peak near 585 cm −1 is correlated with the V 4 mode [20][21][22][23].…”

“…Raman spectroscopy is a powerful, fast, and nondestructive experimental technique, which has been extensively applied not only in basic scientific researches, but also for practical applications. It can provide physical, chemical, and structural characteristics of investigated samples [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. In the past decade, Raman spectroscopy has been applied for quantitative and qualitative studies of various types of minerals.…”

“…Antonakos et al [20] studied the differences between biological apatite and different types of natural apatite and synthetic apatite. Elgharbi et al [21] found the structure and composition of the Tunisian phosphorite after calcination at different temperatures. Wang et al [22] analyzed the structural changes of synthetic carbonate apatite and natural bone minerals.…”