Comparative Study on the Structural and Compositional Analysis of Hydroxyapatite(HA) Synthesized from Corbicula Fluminea and Pholas Orientalis Shells under Different Synthesis Parameters

The utilization of shell-derived hydroxyapatite (HA) as a sustainable biomaterial has gained increasingattention however, comparative studies involving different shell sources and synthesis conditions remain limited.This study investigated the effects of shell source, reaction pH and sintering treatment on the structural,compositional and morphological properties of HA synthesized from Corbicula Fluminea and Pholas Orientalis shells using a chemical precipitation method. HA samples were prepared at pH 10 and pH 11, with and without sintering at 500°C and characterized using Fourier Transform Infrared (FTIR) spectroscopy, X-ray Diffraction(XRD), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray (EDX)spectroscopy. FTIR analysis confirmed the successful formation of HA and revealed stronger carbonate substitution in Pholas Orientalis-derived samples, indicating the presence of type-B carbonated HA. XRD results showed that all synthesized samples exhibited the characteristic hexagonal HA phase with crystallite sizes ranging from 4.20 to 15.47 nm. HA derived from Pholas Orientalis exhibited slightly lower crystallinity (41.70%) compared to Corbicula Fluminea-derived HA (44.95%). FESEM observations demonstrated that increasing the synthesis pH from 10 to 11 produced finer and more homogeneous particles, while sintering promoted particle densification and crystal growth. EDX analysis revealed Ca/P ratios of 1.42-1.51 for Corbicula Flumineaderived HA and 1.59-2.13 for Pholas Orientalis-derived HA. The findings indicate that shell source and synthesis parameters significantly influence HA characteristics and can be tailored to develop sustainable biomaterials for bone tissue engineering and other biomedical applications.