Abstract: Nano-hydroxyapatite was prepared by chemical precipitation with Ca(NO₃)₂ and (NH₃)₂HPO₄ 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×21.3nm, week crystallinity, high surface energy, and the specific surface area of 135m²/g. Ni²⁺ is selected as adsorption object ion, the Langmuir adsorption isotherm is applicable when Ni²⁺ initial concentration is lower than 0.1mol/L, whereas when Ni²⁺ initial concentration is higher than 0.1mol/L, Ni²⁺ substitutes Ca²⁺ and binds 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.

Key words: hydroxyapatite, adsorption mechanism, Ni²⁺ ions