Synthesis and Characterization of Hydroxyapatite from Duck Eggshell by Wet Precipitation Process

ABST CT: Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) is the most stable form of calcium phosphate and widely used in various medical applications, mainly in orthopedics and dentistry due to its close similarities with the inorganic mineral component of bone and teeth. is study aims to synthesize hydroxyapatite from duck eggshell using the precipitation method. e duck eggshell was calcined, hydrated (slaking) and underwent carbonation to form Precipitated Calcium Carbonate (PCC). A erwards, (NH4)2HPO4 was added to produce HAp by varying the molar ratio of Ca/P by 1.67, 1.77 and 1.87 and stirring speed by 200, 250, 300rpm under basic condition (pH 10 – 11). e best results were obtained at a molar ratio of 1.77 with 200rpm stirring speed. Furthermore, the X-ray Diffraction (XRD) analysis showed that its crystals were hexagonal with sizes of 23.062nm, in the absence of other crystalline phases. erefore, the hydroxyapatite was obtained in the agglomerates form with a speci c surface area of 55.929m2/g.


INTRODUCTION
Hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 , is the main inorganic compound present in hard tissues such as human bone. Consequently, it is readily considered as a bioactive material for arti cial bone and teeth substitution because of its biocompatibility, osteoconductivity, chemical and biological affinity with human bone tissues and teeth. Furthermore, it is widely used in biomedical application as ller, coating on bone and dental implants. Hydroxyapatite is derived from natural resources rich in calcium carbonate (CaCO 3 ) like limestone [1], cockle shells [2], egg shells [3,4], animal bone [5] or coral [6,7]. In this study, it was synthesized from duck egg shells using precipitation method. e selection of duck egg shells as a source of calcium was due to its abundance in Indonesia. Buasri et al (2013) reported that the content of calcium in the form of calcium oxide (CaO) in duck egg shells was 98,925%.
ere are quite number of methods that can be used to produce synthetic nanoparticle HAp such as : precipitation [8,9], hydrothermal [2,6], mechanochemical [10] and sol-gel [3,11]. e precipitation method was chosen in this study due to its simple and low-cost processing technique in industrial scale. is method generally produces particles in the nano-scale region and less than 100nm [12]. However, the hydroxyapatite obtained using this method contains considerable contaminant. erefore, to solve this problem, HAp was synthesized from duck egg shells through the formation of Precipitated Calcium Carbonate (PCC) using modi ed carbonation method.
In our previous research, hydroxyapatite was synthesized from cockle shells and eggshells PCC's using hydrothermal and sol gel methods [2,3]. PCC is a calcium carbonate compound (CaCO 3 ), which is processed from natural resources containing calcium carbonate through a series of chemical reactions. Its particles are homogenous i.e. same size with micro-scale particles and have high purity (99.8%). Azis et al, [2] obtained a highly puri ed hydroxyapatite from PCC cockle shells without any other crystalline phase by using hydrothermal method. Meanwhile, synthesis of hydroxyapatite from PCC duck egg shells using precipitation method has never been previously reported. Fig. 1 were collected from Pekanbaru, Indonesia. Other materials used include diammonium hydrogen phosphate ((NH 4 ) 2 HPO 4 ), (Merck), 2M nitric acid (HNO3), 65% ammonium hydroxide (NH 4 OH) (Merck), CO 2 and aquadest. e duck egg shell samples were thoroughly washed, cleaned and air-dried for two days. A erwards, they were crushed and grounded to ne powder consistency using a blender. 2.2. Process of forming precipitated calcium carbonate (PCC) from duck egg shells e procedure for the formation of PCC from duck egg shells was carried out using the modi ed carbonation method, referred from Azis et al. [2]. PCC is the main material used in synthesizing hydroxyapatite via precipitation method. e reaction for the formation of PCC using modi ed carbonation method is represented by the following equations [13]. Calcination :

Materials Preperation e duck egg shells
Hydration : Precipitation : 2.3 Synthesis of hydroxyapatite from PCC duck egg shells using precipitation method Because the solubility of PCC in water is very low, its usually dissolved in mineral acid. erefore, in this study 5gram of PCC powder from duck egg shells were dissolved in 200ml of 0.3M HNO 3 solution. Furthermore, 360ml of (NH 4 ) 2 HPO 4 solution was prepared by varying the molar ratio of Ca and P reactant by 1.67; 1.77 and 1.87. A erwards, it was added in drops to the PCC solution at a rate of 6ml/min for 24h and stirred at 300rpm. e pH was monitored at 10-11 using 33% NH 4 OH. e precipitate object was stirred by using magnetic stirrer at 200, 250 and 300rpm for 24h at room temperature (27 0 C) and aged for 24h. Subsequently, it was ltered with a lter paper and repeatedly washed with aquadest until the pH of solution was 7. A erwards, the precipitates were dried at 110 0 C for 24h and sintered at 500 0 C for 1h. e chemical equations for the reaction are shown below:

RESULTS AND DISCUSSION
e FTIR spectrum of HAp powder (Fig. 2 a,b,c) showed the sharpen bands of PO 4 -3 at 1025-1029 cm -1 . According to Stanciu et al. [14], the sharpen peaks of PO 4 -3 implies that the crystallinity of the hydroxyapatite powder is good. Unfortunately, from Fig. 2 (a) and (b), it is seen that the broad bands at 3370 and 3379cm -1 were ascribed to the N-H asymmetric stretching mode [15]. However, it was assumed that O-H stretching mode corresponded to H 2 O at bands 3800-2500cm -1 .  (Fig. 3).
e morphology and content of element present in the synthesized hydroxyapatite at molar ratio of Ca and P reactant : 1.67; 1.77 and 1.87 and stirring speed of 200rpm, were con rmed from the SEM micrograph data as shown in Fig. 4.   Table 2. Table 2 Ca, P and microelement content and Ca and P ratio in HAp product e ratio molar of Ca and P hydroxyapatite was synthesized from PCC of duck egg shells was 1.699. e surface area of hydroxyapatite powder was characterized using BET analysis and the value obtained was 55.929m2/g.

CONCLUSION
In this study, hydroxyapatite nanoparticle powder was successfully synthesized from the PCC of duck egg shells using precipitation method. e variation of stirring speed did not have a signi cant in uence on the synthesized