Preparation and characterization of bio-waste derived chitosan hydroxyapatitepectin green biocomposite

This study focuses on the synthesis and structural analysis of biocomposites comprising chitosan (Cs), hydroxyapatite (HA), and pectin (Pe). Cs was extracted from shrimp skin, HA from bovine teeth and bones, and Pe from orange peel and apple. The biocomposites were prepared via a freeze-drying method using glutaraldehyde (GA) as a cross-linking agent. FTIR, XRD, FE-SEM, EDS-EDAX and BET were employed to characterize the chemical structure, crystallinity, morphology, surface area, and elemental composition. The extracted Cs had a molecular weight of 4.1 × 10⁵ Da, a 70% degree of  deacetylation, and an extraction yield of 31.2%. The results confirmed biocomposite formation with  a near-stoichiometric Ca/P ratio (1.67) in HA. Biocomposites containing HA calcined at 1000 °C and Pe  from orange peel with 72% galacturonic acid, exhibited enhanced crystallinity (up to 70.61%), uniform  dispersion, and high porosity. While an increased HA content improved morphology and surface area (up to 12.5 m2/g), it also reduced crystallinity after reaching the maximum point, possibly due to weakened intermolecular interactions between Cs and Pe.