Effects of calcination on synthesis of hydroxyapatite derived from oyster shell powders

Abstract

Oysters abound on the west coast of Taiwan and waste oyster shell production exceeds 0.12 million tons per year. The wide availability and natural-biological origin of oyster shells, containing several trace elements that will remain in the crystalline structure of synthesized HA making its composition alike human bone, will benefit the overall physiological functioning after implantation. In this study, solid-state reactions between oyster shell powders (CaCO3) and dicalcium phosphate dihydrate (DCPD) were performed through ball milling and subsequently calcining at various temperatures (900, 1000, 1100, and 1200 °C) and durations (1, 3, 5, and 10 h). The XRD results showed that we have successfully synthesized high phase-purity HA from DCPD and oyster shell powders through 1 h of milling and then calcined at 1000 °C for 10 h or at 1200 °C for 1 h. The crystallite size of as-prepared HA was around 45.3 nm, while the particle sizes were 2.23 and 2.59 μm, respectively. According to the FTIR analysis of as-prepared HA powders calcined at 1000 °C for 10 h or at 1200 °C for 1 h, the carbonate ion peaks observed for the specimen closely matched those of A- and B-type carbonates. It is worth noting that the final products composed of single-phase HA or biphasic calcium phosphate (HA+β-TCP) can easily be prepared by using different calcination temperatures and times, although we intended to produce pure HA from oyster shell powders.