A Comparative Study on Synthesis and Characterization of Hydroxyapatite Nanoparticles from Different Industrial and Bio-Wastes

Hydroxyapatite (HAP), as a bioceramic substance, is indispensable for medical bone repair and replacement. As a result, it has a wide range of research and application opportunities in materials science and biomedicine. This study spotlights the feasibility production of sustainable HAP from diverse waste sources to showcasing their potential utilities for environmentally friendly applications and reduced ecological impacts. Thus, cement kiln dust, eggshell and buffalo bone wastes were applied for preparing main HAP precursors such as calcium sulfate, calcium nitrate and non pure HAP in bone, respectively. During reaction of diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) with extracted calcium sulfate; HAP was obtained via microwave and hydrothermal routes, while chemical precipitation route was performed in case of calcium nitrate extracted from eggshell. Non pure HAP in bone was treated by three methods; i.e., subcritical water process, alkaline hydrothermal hydrolysis and thermal decomposition to produce pure HAP samples. Characterization of HAP obtained was performed using XRD, FTIR, XPS, TGA, N ₂ adsorption-desorption at -196 ^o C and SEM analyses. CaSO ₄ -CKD and Ca(NO ₃ ) ₂ -eggshell were successfully prepared HAP samples with rough surfaces composed of spherical particles into porous HAP with a high total surface area (93.8-150.3 m ² /g), whereas HAP obtained from buffalo bone exhibited the lowest porosity (12.9–34 m ² /g). The prepared samples outperformed the purchased HAP sample in terms of surface and textural qualities, with a Ca/p ratio of around 1.66, comparable to natural HAP. Conclusively, the calcium supplies derived from CKD and eggshells are superior suited to produce highly porous HAP samples than calcium sources derived from buffalo bones.