Preparation and Characterization of Hydroxyapatite from Eggshells via a Basic Route Using Attritor Milling

Area of Science:

• Materials Science
• Biomaterials Engineering
• Nanotechnology

Background:

• Hydroxyapatite (HAp) is a crucial biomaterial for bone tissue engineering.
• Developing cost-effective and sustainable synthesis methods for HAp is essential.
• Eggshells are an abundant waste material containing calcium carbonate, a potential precursor for HAp.

Purpose of the Study:

• To synthesize pure hydroxyapatite (HAp) from locally sourced eggshells.
• To investigate the structural, chemical, and morphological properties of the synthesized HAp.
• To evaluate the potential of eggshell-derived HAp for bone tissue engineering applications.

Main Methods:

• Eggshells were calcined to obtain calcium oxide (CaO).
• CaO reacted with diammonium hydrogen phosphate via mechanochemical attritor milling.
• Samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS).
• A subset of samples underwent a second calcination at 900 °C.

Main Results:

• Nanocrystalline HAp with low-intensity reflections was synthesized.
• A second heat treatment at 900 °C resulted in highly crystalline hexagonal HAp with well-defined grains and a macroporous surface.
• EDS confirmed a Ca-P-O rich composition with a Ca/P ratio of 2.28, indicating secondary calcium-rich phases.
• FTIR analysis showed characteristic phosphate bands and a reduction in residual water and carbonates after calcination.

Conclusions:

• Pure hydroxyapatite (HAp) can be successfully synthesized from eggshells.
• The synthesis method allows for control over crystallinity and morphology through post-synthesis heat treatment.
• The resulting eggshell-derived HAp exhibits promising structural and chemical properties for potential applications in bone tissue engineering.
• Further studies are needed to evaluate the biological performance of this HAp material.