CHARACTERIZATION OF NANO-HYDROXYAPATITE SYNTHESIZED FROM SEA SHELLS THROUGH WET CHEMICAL METHOD

Abstract

Nano-hydroxyapatite (HA) was synthesized by a wet chemical reaction using powdered sea shells ( CaO ) as starting material which was converted to calcium hydroxide ( Ca(OH) 2) and subsequently reacted with phosphoric acid (H3PO4) . Initially raw sea shells ( CaCO3 ) were thermally converted to amorphous calcium oxide by heat treatment. Two sets of experiments were done; in the first experiment, HA powder was dried in an electric furnace and in the second experiment, the reactants were irradiated in a domestic microwave oven followed by microwave drying. In each set of experiments, the concentrations of the reactants were decreased gradually. HA was synthesized by slow addition of phosphoric acid (H3PO4) in to calcium hydroxide ( Ca(OH) 2) maintaining the pH of the solution at 10 to avoid the formation of calcium deficient apatites. In both the experiments, Ca:P ratio of 1.67 was maintained for the reagents. The synthesized samples showed X-ray diffraction (XRD) patterns corresponding to hydroxyapatite. The wet chemical process with furnace drying resulted in HA particles of size 7–34 nm, whereas microwave irradiated process yielded HA particles of size 34–102 nm as evidenced from XRD analyses. The above experimental work done by wet chemical synthesis to produce HA powder from sea shells is a simple processing method at room temperature. Microwave irradiation leads to uniform crystallite sizes as evident from this study, at differing concentrations of the reactants and is a comparatively easy method to synthesize HA. The high resolution scanning electron microscopy (HRSEM)/transmission electron microscopic (TEM) analyses revealed the characteristic rod-shaped nanoparticles of HA for the present study.