Microwave-assisted synthesis of nanocrystalline hydroxyapatite using calcium supplies from green mussel shells with synthesis time optimization

Nanocrystalline hydroxyapatite (HA) is utilized widely in biomaterials due to its capacity to enhance bone growth and compatibility with various manufacturing techniques. Traditional hydrothermal methods for synthesizing HA from green mussel shells (Perna viridis) typically involve long synthesis times, high temperatures, and elevated costs. This study explores a microwave-based hydrothermal method as a more cost-effective and efficient alternative for synthesizing HA from green mussel shell waste. The synthesis involves blending calcined green mussel shells with diammonium hydrogen phosphate [(NH4)₂HPO₄], followed by microwave irradiation for 1, 3, 5, and 7 minutes at 80, 240, and 400 watts. Analysis of the synthetic powder used analytical techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX). The synthesis conditions were optimized using a microwave power of 240 watts and a 3-minute synthesis duration, yielding HA with a nano-crystallite size of 1.5–1.7 nm and a HA crystalline weight percentage of 90.7 %. FTIR analysis confirmed functional groups such as phosphate (PO₄³), hydroxyl (OH⁻), and carbonate (CO₃), indicating the formation of a carbonated nanocrystalline HA phase. The synthesized powder displayed an irregular structure with agglomeration containing nanocrystalline HA and demonstrated potential for biomaterial applications.