Synthesis of eggshell derived hydroxyapatite via chemical precipitation and calcination method

Abstract

Abstract It had been reported that around 250, 000 tons of eggshells waste were produced annually worldwide. It is possible to transform the eggshell wastes to useful biomaterials such as hydroxyapatite (HAp). In this research, HAp was produced from eggshell waste. The main objectives of this study are to synthesis the natural HAp from eggshell waste using combination of chemical precipitation and calcination method. The characterisation of the sample was done by using X-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectrometry (EDS), and scanning electron microscopy (SEM). At first, the calcination of raw eggshell was done to convert the CaCO3 of the eggshell to CaO before being subjected to the chemical precipitation process. The calcined powder was then mixed with distilled water and the pH of the solution mixture was set at 8.5 using 0.6 M of phosphoric acid prior to the 24-hour ageing phase. Subsequently, the precipitates were calcined at various temperatures; 300 °C, 500 °C, 700 °C, 900 °C and 1100 °C. The XRD results showed that 700 °C was the optimum calcination temperature for HAp, while the sample at 900 °C and 1100 °C shows the formation of biphasic HAp and β-tricalcium phosphate (β-TCP) compound. In addition, the EDS analysis showed that the 700 °C calcined sample had a Ca/P of 1.67 which is identical to stoichiometric HAp. As a result, the study showed that by using the precipitation and calcination technique, HAp was able to be synthesised from the eggshell waste.