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

Hydroxyapatite (HAP), as a bioceramic substance, has a wide range of research and application opportunities in materials science and biomedicine. This study spotlights the feasibility production of sustainable HAPs from diverse waste sources to showcasing their potential utilities for environmentally friendly applications and reduced ecological impacts. Thus, cement kiln dust (CKD), 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 ((NH4)2HPO4) with extracted calcium sulfate, HAP samples were obtained via microwave and hydrothermal routes. Chemical precipitation route was performed in case of calcium nitrate extracted from eggshell to prepare a HAP. 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, N2 adsorption-desorption at ‒196 oC and SEM analyses. Porous HAP samples were successfully prepared using CaSO4-CKD and Ca(NO3)2-eggshell with rough surfaces composed of spherical particles and high total surface areas (93.8-150.3 m2/g), whereas HAP obtained from buffalo bone exhibited the lowest porosity (12.9-34 m2/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 precursors to produce highly porous HAP samples than calcium sources derived from buffalo bones.