Synthesis, structure, and properties of new difficultly soluble complex compounds of technetium with diethylenetriaminepentaacetic acid

To elucidate the causes of formation of difficultly soluble compounds of Tc with diethylenetriaminepentaacetic acid (DTPA) used in the extraction technology for spent nuclear fuel reprocessing, these compounds were studied by X-ray diffraction, IR, Raman, UV-visible, EXAFS, and ESR spectroscopy. The features of the Tc reduction in nitric acid solutions under the action of hydrazine, preceding the precipitate formation, were considered. The compound studied contains polyaminocarboxy ligands with mixed coordination. It is polymeric and polynuclear. Aging of the precipitate is accompanied by its gradual evolution toward formation of hydrated TcO2. The Tc: DTPA ratio in the precipitate is close to 1: 1, and the prevalent valence state of Tc is IV. A possible structure of the compound was suggested on the basis of the results obtained, and ways to exclude the precipitate formation were suggested. © 2011 Pleiades Publishing, Ltd.