Synthesis and FTIR Characterization of Mg-Hydroxylapatite Derived from Dolostone with High Dolomite Mineral Content
Wilson Mahene, Charles Gervas, Askwar Hilonga, Revocatus L. Machunda
Abstract
We present the synthesis of magnesium-substituted hydroxylapatite starting from locally available dolostone. The apatite was prepared by a reaction between heat pre-treated dolostone powder with phosphoric acid, maintained at the pH of 12.5 using sodium hydroxide. The resultant material was then calcined at 500 °C, 600 °C, 700 °C, 800 °C and 900 °C. The precursor dolostone was characterized by organic elemental analyser (CHNS-O analyser), X-ray fluorescence (XRF) and Fourier transform infrared spectroscopy (FTIR), while the synthesized material was characterized by using FTIR. Results indicated that the dominant mineral in the carbonate rock materials was near-stoichiometric dolomite, while the synthesized material was found to be (carbonate, magnesium)-substituted hydroxylapatite. The synthesized material did not exhibit hydroxylapatite diagnostic peaks until after being calcined at 600 °C. The peaks became more distinct with increase in calcination temperature. The prepared material exhibited a low degree of crystallinity and low conversion temperature to beta-tricalcium phosphate, 700–800 °C. These characteristics are typical of a magnesium-substituted hydroxylapatite (Mg-substituted β-tricalcium phosphate). This work has demonstrated the feasibility of synthesizing magnesium-substituted hydroxylapatite (Mg-HA), with potential applications in water purification, using dolostone as a calcium/magnesium source. Keywords: Dolostone; crystallinity; magnesium-substituted hydroxylapatite; magnesium-substituted beta-tricalcium phosphate;