Characterization and Application of New Apatitic Materials Synthesized from Hahotoé-Kpogamé Phosphate Rock

Abstract

Aims: Phosphorus and phosphate are broadly used in many areas ranging from advance researches to manufacturing companies for regular use purposes. In Togo, the raw phosphate is exploited and exported to serve as an ingredient in chemical fertilizers, detergents, phosphoric acid synthesis, etc. The aim of the present work is an investigation of alternative valuation of the raw phosphate of Hahotoé-Kpogamé in Togo. Methodology: The study consists of the transformation of the raw phosphate into hydroxyapatite by dissolution followed by a precipitation. The hydroxyapatite thus obtained can be used, for example as a conditioning matrix of industrial waste, as a catalyst support, or for the depollution of water etc. The characterization was carried out by Fourier Transform Infrared Spectroscopy, X-Ray Diffraction, Thermogravimetric Analysis coupled to Thermal Differential Analysis and Inductively Coupled Plasma Atomic Emission Spectroscopy. Results: These analyses revealed that the materials are predominantly of non-stoichiometric hydroxyapatite and minority of phosphate tricalcium and impurities. The synthesized materials (calcined and uncalcined) were applied as adsorbent and as coadsorbent of a photocatalyst (TiO2) for methylene blue removal. The study of the adsorption of the methylene blue was carried out in a batch mode. The adsorption of methylene blue on the synthesized materials gave a low yield (15 to 20%). However, used as in the mixture with titanium dioxide, the adsorption rate of methylen blue was increased significantly (57% of removal rate with 0.5 g synthesized materials + 2 g of TiO2 P25). Conclusion:  uncalcined hydroxyapatite obtained from raw phosphate can be used as an efficient co-adsorbent of titanium dioxide leading to an alternative valorization of this natural phosphate.