| Abstract: | Formation conditions, compositions and structures of precipitates or “the third phase” were systematically examined in the systems of Zr and radiation depleted products of TBP, such as HDBP, H2MBP, H3PO4, by means of elemental analysis, X-ray diffraction, infrared spectra and 1H-NMR. It was confirmed that one of the most important origins for the third phase is a complexation between Zr ion and the depleted products of TBP. Followings were also elucidated: (1) When the depleted products co-exist with each other, the cooperative effects on the precipitate formation appear in low acid solutions. (2) Precipitate formation depends on the mole ratio of HDBP/Zr. The amount of precipitate reaches the maximum at the mole ratio of approximately 2 and decreases with increasing concentration of HDBP and finally disappears at approximately 10. (3) Precipitate formed at the mole ratio of approximately 2 has the chemical formula, Zr (NO3)2 (HDBP)2 (OH)2. (4) Precipitates of the Zr-H2MBP system begin to appear at the concentration of H2MBP in one order of magnitude smaller than that of HDBP in Zr-HDBP system. (5) Precipitates of Zr-H2MBP system have no NO3 ion and a basic structure of Zr-(HMBP)2(OH)2 with an interlayer distance of 16 Å. |
