Abstract:

Purpose: To investigate the adsorption capacity of hydroxyapatite prepared from clam shell for Pb2+. Methods:
Hydroxyapatite was prepared from clam shell by precipitation method under room temperature, and its crystal phase
composition, morphology and chemical composition were characterized by employing X-ray diffraction (XRD), scanning
electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR). Adsorption of Pb2+ solution models by the
hydroxyapatite adsorbent was investigated with respect to various parameters such as adsorption time, pH, temperature and
initial Pb2+ concentration and the adsorption kinetics and thermodynamics were also explored. Results: The best adsorption
capacity was found at pH 3.0. An acidic environment favored Pb2+ adsorption, and the adsorption capacity of hydroxyapatite
was gradually reduced with increasing pH. The adsorption process reached equilibrium in 30 min. The adsorption capacity was
directly proportional to initial Pb2+ concentration. Higher temperatures were favorable for the adsorption reaction. Conclusion:
The hydroxyapatite prepared in this study has good adsorption capacity for Pb2+, and the adsorption process can be described by
the Langmuir model and follows pseudo-second-order kinetic equation as a spontaneous endothermic process.

Key words: clam shell, hydroxyapatite, Pb2+, adsorption