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Date of Award


Degree Name

Doctor of Philosophy




The relationships between the lanthanide complex formation equilibria and the lanthanide-actinide separation application of three radius sensitive ligands have been studied. The consecutive stepwise formation constants of the 1:1, 2:1, and 3:1 chelate species formed by the interaction of the 2,3-dihydroxy-2,3-dimethylbutanoate anion (DHDMB) and the tripositive lanthanides and yttrium were determined potentiometrically at 0.1 M ionic strength and 25(DEGREES)C. The results indicate that three different coordination modes, one tridentate and two bidentate are in evidence;Tracer level ('241)Am - ('155)Eu cation-exchange experiments utilizing DHDMB eluents have indicated that this dihydroxycarboxylate does not form a sufficiently strong americium complex to elute that actinide ahead of europium. The overall stability of the americium 3:1 complex appears to be intermediate between samarium and europium;Cation-exchange elutions of ('241)Am, ('155)Eu, and ('160)Tb mixtures with 2,2'-diaminodiethylether-N,N,N',N'-tetraacetic acid (EEDTA) solutions prove that the EEDTA ligand is capable of eluting americium ahead of all of the tripositive lanthanide cations. The minimum separation occurs with terbium, where the Am-Tb separation factor is 1.71;The successful synthesis of 1,5-diaminopentane-N,N,N',N'-tetraacetic acid (PMDTA) was accomplished by the use of cation-exchange purification techniques. A new mathematical method was developed to calculate the formation constants of the protonated and unprotonated lanthanide-PMDTA complexes from potentiometric data. The results for both cases display a monotonic increase across the entire lanthanide series;Cation-exchange elutions of tracer quantities of Am, Eu, and Tb revealed that terbium is eluted ahead of both americium and europium. This elution order illustrates that the mid-chain chelating groups of related aminocarboxylates are necessary to their actinide selectivity;*DOE Report IS-T-940. This work was performed under contract W-7405-eng-82 with the Department of Energy.



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Michael Wayne Potter



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136 pages