Polyoxometalates for Radioactive Waste Treatment - Final Report - 06/15/1996 - 09/14/2000

Pope, Michael T.

Georgetown University, Washington, DC (United States)

关键词: Lanthanides;    Organometallic Compounds Polyoxometalate;    Tank Wastes;    Waste Forms;    Actinides;   

DOI  :  10.2172/790202
RP-ID  :  DOE/ER/14695
RP-ID  :  FG07-96ER14695
RP-ID  :  790202

美国|英语

来源: UNT Digital Library

【 摘 要 】

The research was directed primarily towards the use of polyoxometalate complexes for separation of lanthanide, actinide, and technetium species from aqueous waste solutions, such as the Hanford Tank Wastes. Selective binding of these species responsible for much of the high level waste (HWL) activity, can reduce the volume of material to be subsequently vitrified or otherwise converted for long-term storage. A secondary objective was to explore the direct conversion of the polyoxometalate complexes into possible waste forms, oxide bronzes, thereby avoiding additional handling and energy-intensive vitrification procedures. Although the advantages of polyoxometalate anions (POMs) lie in their high thermal and radiolytical stabilities, that has been no attempt to exploit the remarkable variety of these complexes beyond the use of the two anions mentioned above. Our broad knowledge of POM chemistry has allowed us to address and rectify this omission. The innovative aspects of the project are: (a) the selective sequestration of lanthanide and actinide cations by a POM system in the presence of excess alkali and transition metal cations; (b) the formation of the first examples of POM complexes of UO2-2+ and their extraction into nonaqueous solvents; (c) the thermal conversion of ammonium salts of lanthanide and actinide POM complexes into inert oxide bronzes at relatively low temperatures; and (d) the direct formation of highly thermally-robust niobate and tantalate complexes of Re (surrogate for Tc) in highly basic solutions.