Extraction of Hydroxyapatite from Fish Bones and Its Application in Nickel Adsorption

Precious materials obtained from biowaste have risen the attentions toward extracting and using these materials in various applications to address both economic and environmental demands. In the present study, we focused on the extraction of hydroxyapatite (HA) from fish bones through the thermal calcination method. The primary tests were carried out to characterize the fish bone-derived materials in terms of chemical composition, morphology, and viability. Therefore, series of characterizing tests including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and inductively coupled plasma (ICP) were carried out. Also, secondary electron microscopy equipped with energy-dispersive spectroscopy (EDS) was performed to determine morphology and elemental analysis of the obtained powder. Furthermore, the cell viability of fish bone-derived hydroxyapatite (FHA) along with its cell differentiation capability was evaluated by performing MTT and ALP assays and the results were compared with those of the commercial type of hydroxyapatite (CHA). The secondary phase of the current study relates to the capability of FHA and CHA on adsorbing nickel, as a model heavy metal, from aqueous solutions by performing bath adsorption experiments and considering initial concentration of nickel, adsorbent dosage, and contact time as the variables. In order to investigate kinetic model and adsorption mechanism, first-order, pseudo-second-order, and intraparticle diffusion kinetic models were used. Also, the equilibrium data were analyzed using Langmuir, Freundlich, and DKR adsorption isotherm models. The XRD and FT-IR results confirmed the successful extraction of HA from fish bones. Besides, ICP and EDS results revealed that the Ca/P ratio of FHA was higher than that of stoichiometric ratio (1.67). In addition, the MTT and ALP results indicated that FHA seemed to be a viable material for cell proliferation and differentiation. Besides, the adsorption outcomes indicated that FHA was sufficiently capable of adsorbing nickel. It was observed that the adsorption data were fitted well with pseudo-second-order and Langmuir isotherm models with maximum adsorption capacities of 50.25 and 48.78 mg g−1on FHA and CHA, respectively.