PHYSICOCHEMICAL CHARACTERIZATION OF AYUQUDUQ PHOSPHORITE BY XRF, FTIR AND XRD METHODS

The chemical, molecular and phase composition of a phosphorite sample from the Ayuquduq area was studied by energy-dispersive X-ray fluorescence (EDXRF), Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The sample contains 25.84 % P2O5, 45.0 % CaO, 8.1 % SiO2, 3.97 % Al2O3, 2.49 % Fe2O3, 2.12 % MgO and 1.28 % K2O, and the CaO/P2O5 mass ratio is 1.74. The FTIR spectrum shows phosphate bands at 605 and 571 cm-1 and a strong ν3 PO4 absorption near 1040–1100 cm-1, together with carbonate bands at 1797, 1430–1450, 876 and 714 cm-1 and a quartz band at 799 cm-1. XRD reflections of quartz and calcite were identified, while the apatite reflections were weak. The results indicate a carbonate-rich phosphorite in which a carbonate-fluorapatite phase coexists with calcite and quartz. The high CaO/P2O5 ratio and the 0.25 ratio of (Al2O3 + Fe2O3) to P2O5 should be considered when choosing acid processing routes.

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