Effects of heat treatment on the synthesis of hydroxyapatite from eggshell powders

Daily, several million tons of eggshells are being generated as biowaste around the globe. The wide availability and natural-biological origin of the eggshells, containing several trace elements that will remain in the crystalline structure of synthesized hydroxyapatite (HA), make their composition similar to human bone. These advantages will benefit the overall physiological functioning after implantation. In this study, we propose a cost-effective and straight-forward technique for converting calcium carbonate obtained from eggshells into highly pure and crystalline HA via ball milling and subsequent heat treatment. Detailed analysis of the prepared samples confirm the formation of high phase-purity HA by milling dicalcium phosphate dihydrate (DCPD) and eggshell powders for 1 h followed by sintering at 1200 °C for 1 h. Besides, samples composed of biphasic calcium phosphate (HA+β-TCP) can easily be prepared by varying the heating temperature and time. The carbonate peaks observed in the Fourier transform infrared spectrum of the as-received HA powder can be associated with the A- and B-type carbonated structure.