Sol-Gel Synthesis and Characterization of Carbonated Hydroxyapatite Nanoparticles from Chicken Bone Waste for the Remediation of Malachite Green Dye Contamination of Water

Abstract

The increasing generation of poultry waste and the growing demand for sustainable biomaterials have stimulated interest in the valorization of animal bone residues as precursors for hydroxyapatite (HA) synthesis. In this study, calcium hydroxyapatite nanoparticles were synthesized from chicken bone waste using a sol–gel method followed by calcination, and the resulting material was comprehensively characterized using pH monitoring, Energy Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), UV–Visible spectroscopy, Brunauer–Emmett–Teller (BET) analysis, and Density Functional Theory (DFT) pore size distribution. The synthesis process showed effective gel formation, with pH increasing from approximately 4.0 to 11.1 during NaOH addition, indicating favorable conditions for hydroxyapatite precipitation. EDX analysis revealed that calcium, phosphorus, and oxygen were the dominant elements, with atomic concentrations of 45.02%, 12.05%, and 36.74%, respectively. The material exhibited a Ca/P ratio of 3.74 and an estimated hydroxyapatite content of approximately 63%, suggesting the coexistence of hydroxyapatite with minor calcium-rich phases. FTIR spectra displayed characteristic phosphate bands at 959.79, 1013.83, and 1086.52 cm⁻¹, carbonate bands at 1410.79 and 1457.39 cm⁻¹, and a hydroxyl stretching band at 3570.79 cm⁻¹, confirming the formation of carbonated hydroxyapatite. SEM micrographs revealed agglomerated nanoparticles with rough and porous surfaces. UV–Visible analysis showed enhanced absorbance across the 200–600 nm wavelength range, indicating increased surface activity and defect-related electronic transitions. DFT pore size distribution demonstrated predominant pore diameters between 1.8 and 2.8 nm, with maximum pore volume occurring within the 2.5–2.7 nm range, confirming a mesoporous structure. The BET adsorption model exhibited excellent linearity (R² ≈ 0.998), indicating significant surface accessibility and adsorption potential. The combined characterization results confirmed the successful conversion of chicken bone waste into mesoporous carbonated hydroxyapatite nanoparticles possessing high surface reactivity, functionalized phosphate and hydroxyl groups, and desirable physicochemical properties. The synthesized material shows strong potential for applications in environmental remediation, adsorption technologies, catalysis, drug delivery, and bone tissue engineering while providing a sustainable route for poultry waste valorization.