Sorption of uranium and other heavy metals on hydroxyapatite

The immobilization of U-VI and Pb-II from aqueous solutions in a solid phase by interaction with calcium hydroxyapatite has been studied in batch experiments with increasing contact times. The results were compared with those previously found for Cd-II. All these elements are able to be efficiently immobilized by such a method. The sorbed quantities vary in the order Pb > U > Cd. The sorption mechanisms are element dependent. The dominant mechanisms are: dissolution-precipitation with formation of an amorphous or microcrystalline phase for UI dissolution-precipitation with the formation of two new crystalline phases and with possible incorporation into the initial apatite for Pb, and intracrystalline diffusion and exchange for Cd.