A new method for synthesizing hydroxyapatite from eggshell and sludge and its calcination exploration

This study presents a novel low-cost synthesis methodology for hydroxyapatite (HAP). HAP was successfully synthesized via a simplified chemical process utilizing eggshells as a calcium source and sludge as a phosphorus source. This approach not only addresses the dual challenges of eggshell and sludge disposal but also establishes an innovative pathway for sustainable and economically viable HAP production. The influence of calcination parameters (The optimal conditions are 600^oC for 3 h) on the microstructure of HAP was systematically investigated, revealing that optimized calcination conditions significantly enhance crystallinity and porosity. Comprehensive characterization of the synthesized HAP was performed using X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Post-calcination characterization revealed significant crystallographic refinement, accompanied by a 95% enhancement in Brunauer-Emmett-Teller (BET) surface area (57.23 m²/g) compared to precursor materials. Analytical results confirmed the high purity and exceptional physicochemical properties of the synthesized HAP, demonstrating substantial potential for applications in environmental remediation and biomedical engineering. This work advances a green and cost-effective strategy for HAP synthesis while pioneering a resource-efficient utilization route for waste-derived eggshells and sludge.