Synthetic alkaline-earth hydroxyapatites: Influence of their structural, textural, and morphological properties over Co²⁺ ion adsorption capacity

This work addresses the synthesis of nanocrystalline barium, strontium, and calcium hydroxyapatites (Ca-HAps) via the chemical precipitation method, followed by calcination. To give a coherent picture of the most important structural, textural, and morphological properties of these materials and to investigate the influence of these characteristics over Co²⁺ ion adsorption capacity from aqueous solutions, the powders prepared were systematically characterized by X-ray diffraction, N₂-physisorption measurements, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry, and Fourier Transformed Infrared spectroscopy (FTIR). The results clearly showed that the Ca-HAp obtained exhibits better nanocrystallinity, greater structural stability, high surface area, high total pore volume, and mesoporosity, compared with the other synthesized hydroxyapatites, and that these physicochemical properties share a direct correlation with favorable Co²⁺ ion adsorption capacity at room temperature and pressure. The results proved that the physicochemical features of resulting alkaline-earth hydroxyapatites, prepared via the chemical precipitation method, played a fundamental role during the adsorption of heavy metal (with high toxicity) from aqueous solutions.