Research on Adsorption Capacity for Ni2+ and Mechanism of Nano-hydroxyapatite

Nano-hydroxyapatite was prepared by chemical precipitation with Ca(NO3)(2) and (NH3)(2)HPO4 as reagent. The phase composition, crystal morphology and specific surface area were characterized by XRD, TEM and BET. The results indicate that n-HA synthesized shows needle-like morphology with uniform average size of 31.9nm x 21.3nm, week crystallinity, high surface energy, and die specific surface area of 135m(2)/g. Ni2+ is selected as adsorption object ion, the Langmuir adsorption isotherm is applicable when NI 2, initial concentration is lower than 0.1 mol/L, whereas when Ni2+ initial concentration is higher than 0.1 mol/L, Ni2+ substitutes Ca2+ and hinds with atom O on the Surface. The adsorption of Ni2+ on n-HA concludes ion exchange, electrostatic adsorption and dissolution-precipitation processes, This result is proved by the change on surface potential, crystal phase composition and binding energy of surface elements of n-HA before and after adsorption, which are analyzed by Zeta potential, XRD and XPS.