| Abstract: | This dissertation focuses on key intergroup and intragroup separations found in the back end of the nuclear fuel cycle, specifically americium from lanthanides and americium from other actinides, most importantly americium from curium. Our goal is to implement a liquid-solid separation process to reduce waste and risk of contamination by the development of metal(IV) phosphate phosphonate inorganic organic hybrid ion exchange materials with the ideal formula of M(O₆P₂C₆H₄)0.5(O₃POA) * nH₂O, where M = Zr or Sn, A = H or Na. These materials have previously shown to have high affinity for Ln, this work will expand on the previous studies and provide methods for the above target separation, exploiting oxidation state and ion charge to drive the separation process. The optimum hydrothermal reaction conditions were determined by adjusting parameters such as reaction temperature and time, as well as the phosphonate to phosphate (pillarto-spacer) ligands ratio. Following these results four bulk syntheses were performed and their ion exchange properties were thoroughly examined. Techniques such as inductively coupled mass spectrometry and liquid scintillation counting were used to determine the affinity of the materials towards Na⁺, Cs⁺, Ca2+, Sr²⁺, Ni²⁺, Nd³⁺, Sm³⁺, Ho³⁺, Yb³⁺, NpO₂⁺, Pu⁴⁺, PuO₂²⁺, Am³⁺, AmO₂⁺, and Cm₃⁺. Separation factors in the thousands have been observed for intergroup separations of the Ln from the alkali, alkaline earth, and low valent transition metals. A new method for Am oxidation was developed, which employed Na₂S₂O₈ as the oxidizing agent and Ca(OCl)₂ as the stabilizing agent for AmO₂⁺ synthesis. Separation factors of 30-60 for Nd³⁺ and Eu³⁺ from AmO₂⁺, as well as 20 for Cm³⁺ from AmO₂⁺ were observed at pH 2. The work herein shows that a liquid-solid separation can be carried out for these difficult separations by means of oxidation and ion exchange. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148358 |
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