Hydrothermal Synthesis and Characterization of the Thorium Phosphate Hydrogenphosphate, Thorium Hydroxide Phosphate, and Dithorium Oxide Phosphate

Because of its low solubility in water and high thermal stability, thorium phosphate diphosphate (TPD), Th4(PO4)4P2O7, seems to be a very good matrix for radionuclide immobilization. During the leaching studies of this compound the formation of a new phase, different from the TPD was observed. In order to identify this phase, two other thorium phosphates: thorium phosphate–hydrogenphosphate (TPHP), Th2(PO4)2HPO4·H2O, and thorium hydroxide phosphate (THOP), Th(OH)PO4, were synthesized in hydrothermal conditions then characterized. It appeared that the neoformed phase was identical to the TPHP.