Abstract：To investigate the use of egg shells and sodium silicate to regulate the hydrothermal crystallization of silicon-substituted carbonate hydroxyapatite (Si-CHAP, (Ca10(PO4)6-x-y(SiO4)x(CO3)y(OH)2-x-y). The obtained Si-CHAP was characterized by BET surface area, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) and investigated as metal adsorption for Pb2+ from aqueous solutions. The effect of various parameters on the adsorption process such as contact time, solution pH, and temperature was studied to optimize the conditions for maximum adsorption. The results showed that the Si-CHAP was mesoporous material with high surface area, and its BET surface area was 323.25m2/g. The removal efficiency and adsorption capacity of Pb2+ by Si-CHAP could reach 99.39% and 149.09mg/g, respectively, when the initial Pb2+ concentration was 300 mg/L and the solid/liquid ratio was 2 g/L at 90 min and room temperature. The adsorption of Pb2+ onto Si-CHAP was well described by the Langmuir equation. The kinetics of adsorption was well fitted by the pseudo-second order kinetic model. Thermodynamic parameters indicated that the adsorption is spontaneous, endothermic accompanied by increase in entropy. This research is expected to provide novel functional materials for treating the heavy metal waste water.
