Hydroxyapatite(HA) prepared by co-precipitation and hydrothermal methods was used for the adsorption of metal ions Ni~(2+).Their phase compositions and crystal structures were analyzed by XRD,TEM and FTIR,the specific surface area was also determined by BET.The results show that the HA prepared by co-precipitation exhibits poor crystalline and high specific surface area,maximum adsorption capacity for Ni~(2+)(60.57 mg/g),which was much higher than that of the HA prepared by hydrothermal method.The work also...