The XRD patterns of the HA synthesized from calcinations original oyster shell powders reacted with HNO3
(NH4)2HPO4 and NH4OH solution with different pH, which was varied from 8 to 10 (Fig. 6 (e)-(g)) and powders of
commercial CaO as starting reagent (Fig. 6 (b)-(d)), are the same. The HA synthesized at pH 9 was the nearly same
as that prepared at pH 10, many sharp peaks appeared, indicating that the samples have high crystallinity. At pH 10,
the crystalline sizes at 2 theta (25-26