Removal of divalent heavy metal ions, i.e., Pb²⁺, Cu²⁺, Zn²⁺and Cd²⁺, respectively, from their chloride or nitrate aqueous solutions was studied by the addition of hydroxyapatite in a batch system. The isotherms for heavy metal ions were of the rectangular type so that the amounts removed from aqueous phase were constant irrespective of the concentration of solutions. The selectivity for the cations on hydroxyapatite can be explained in terms of the ionic radii and the its electronegativities. Kinetic experiments were carried out in an agitated tank adsorber. Effective diffusivities of cupric chloride, zinc chloride and cadmium chloride inside hydroxyapatite were 2.88×10^-10m²/s, 2.77×10^-10m²/s and 2.95×10^-10m²/s, respectively, Pb²⁺ was also exchanged very quickly with Ca²⁺ and easily removed by hydoxyapatite.