Valorization of Fish Bone Waste into High-Purity Hydroxyapatite Nanoparticles

Abstract

The increasing generation of fish processing waste has created environmental concerns while simultaneously presenting opportunities for the recovery of valuable biomaterials. This study investigated the synthesis and characterization of calcium hydroxyapatite (CHA) nanoparticles from fish bone waste using a direct calcination method without the addition of chemical reagents. Cleaned and dried fish bones were calcined at 700 °C for 3 h and subsequently milled to obtain nanoparticulate hydroxyapatite. The synthesized material was characterized using Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-ray Spectroscopy (EDX), Scanning Electron Microscopy (SEM), Ultraviolet–Visible (UV–Vis) spectroscopy, and point of zero charge (pHpzc) analysis. EDX results showed that the nanoparticles contained 42.09 wt% Ca, 13.02 wt% P, and 36.38 wt% O, corresponding to a Ca/P ratio of 3.23, indicating a calcium-rich hydroxyapatite phase with minor impurities including Al (1.11 wt%), Si (0.70 wt%), Fe (0.19 wt%), and Sn (0.20 wt%). FTIR analysis confirmed the formation of hydroxyapatite through characteristic phosphate bands at 959.79 and 1013.83 cm⁻¹, hydroxyl absorption at 3572.65 cm⁻¹, and carbonate bands at 879.65, 1086.52, 1410.80, and 1457.39 cm⁻¹, indicating carbonate-substituted hydroxyapatite. SEM micrographs obtained at 500× and 1000× magnifications revealed irregular, porous, and agglomerated particles with rough surface morphology, providing abundant active sites for adsorption processes. UV–Vis spectroscopy showed broad absorption within the 350–750 nm wavelength range, suggesting favorable optical properties associated with nanoscale hydroxyapatite particles. The pHpzc analysis indicated a predominantly basic surface character, with surface charge transition occurring within the alkaline region. The combined results demonstrate that fish bone waste can be successfully transformed into carbonate-containing calcium hydroxyapatite nanoparticles through a simple, low-cost, and environmentally sustainable process. The porous morphology, calcium-rich composition, and reactive surface functional groups suggest strong potential for environmental remediation applications, particularly in the adsorption of dyes and other aqueous pollutants.