3 research outputs found
Structural and Morphological Influences on Neptunium Incorporation in Uranyl Molybdates
No full textThe in situ incorporation of pentavalent
neptunium has been studied
in the structurally related uranyl molybdate frameworks (NH<sub>4</sub>)<sub>4</sub>[(UO<sub>2</sub>)<sub>5</sub>(MoO<sub>4</sub>)<sub>7</sub>]Â(H<sub>2</sub>O)<sub>5</sub> and (NH<sub>4</sub>)<sub>2</sub>[(UO<sub>2</sub>)<sub>6</sub>(MoO<sub>4</sub>)<sub>7</sub>]Â(H<sub>2</sub>O)<sub>2</sub> prepared under similar synthetic conditions. The presence
of NpÂ(V) was confirmed by UV–vis–NIR spectroscopy in
the first compound, whereas NpÂ(VI) was identified in the second based
on the observation of a unit-cell contraction and the lack of a spectral
signature for NpÂ(V). The incorporation of neptunium does not affect
the overall structure of the host compound based on the crystallographic
unit-cell parameters. Neptunium appears to preferentially incorporate
in the structure of (NH<sub>4</sub>)<sub>2</sub>[(UO<sub>2</sub>)<sub>6</sub>(MoO<sub>4</sub>)<sub>7</sub>]Â(H<sub>2</sub>O)<sub>2</sub> due to the formation of NpÂ(VI) during synthesis, although higher
total uptakes were observed in (NH<sub>4</sub>)<sub>4</sub>[(UO<sub>2</sub>)<sub>5</sub>(MoO<sub>4</sub>)<sub>7</sub>]Â(H<sub>2</sub>O)<sub>5</sub> due to a higher initial concentration of neptunium in solution
despite maintaining the same ratio of U:Np
Comparisons of Plutonium, Thorium, and Cerium Tellurite Sulfates
No full textThe
hydrothermal reaction of PuCl<sub>3</sub> or CeCl<sub>3</sub> with
TeO<sub>2</sub> in the presence of sulfuric acid under the
comparable conditions results in the crystallization of PuÂ(TeO<sub>3</sub>)Â(SO<sub>4</sub>) or Ce<sub>2</sub>(Te<sub>2</sub>O<sub>5</sub>)Â(SO<sub>4</sub>)<sub>2</sub>, respectively. PuÂ(TeO<sub>3</sub>)Â(SO<sub>4</sub>) and its isotypic compound ThÂ(TeO<sub>3</sub>)Â(SO<sub>4</sub>) are characterized by a neutral layer structure with no interlamellar
charge-balancing ions. However, Ce<sub>2</sub>(Te<sub>2</sub>O<sub>5</sub>)Â(SO<sub>4</sub>)<sub>2</sub> possesses a completely different
dense three-dimensional framework. Bond valence calculation and UV–vis–NIR
spectra indicate that the Ce compound is trivalent whereas the Pu
and Th compounds are tetravalent leading to the formation of significantly
different compounds. PuÂ(TeO<sub>3</sub>)Â(SO<sub>4</sub>), ThÂ(TeO<sub>3</sub>)Â(SO<sub>4</sub>), and Ce<sub>2</sub>(Te<sub>2</sub>O<sub>5</sub>)Â(SO<sub>4</sub>)<sub>2</sub> represent the first plutonium/thorium/cerium
tellurite sulfate compounds. Our study strongly suggests that the
chemistries of Pu and Ce are not the same, and this is another example
of the failure of Ce as a surrogate
Comparisons of Plutonium, Thorium, and Cerium Tellurite Sulfates
No full textThe
hydrothermal reaction of PuCl<sub>3</sub> or CeCl<sub>3</sub> with
TeO<sub>2</sub> in the presence of sulfuric acid under the
comparable conditions results in the crystallization of PuÂ(TeO<sub>3</sub>)Â(SO<sub>4</sub>) or Ce<sub>2</sub>(Te<sub>2</sub>O<sub>5</sub>)Â(SO<sub>4</sub>)<sub>2</sub>, respectively. PuÂ(TeO<sub>3</sub>)Â(SO<sub>4</sub>) and its isotypic compound ThÂ(TeO<sub>3</sub>)Â(SO<sub>4</sub>) are characterized by a neutral layer structure with no interlamellar
charge-balancing ions. However, Ce<sub>2</sub>(Te<sub>2</sub>O<sub>5</sub>)Â(SO<sub>4</sub>)<sub>2</sub> possesses a completely different
dense three-dimensional framework. Bond valence calculation and UV–vis–NIR
spectra indicate that the Ce compound is trivalent whereas the Pu
and Th compounds are tetravalent leading to the formation of significantly
different compounds. PuÂ(TeO<sub>3</sub>)Â(SO<sub>4</sub>), ThÂ(TeO<sub>3</sub>)Â(SO<sub>4</sub>), and Ce<sub>2</sub>(Te<sub>2</sub>O<sub>5</sub>)Â(SO<sub>4</sub>)<sub>2</sub> represent the first plutonium/thorium/cerium
tellurite sulfate compounds. Our study strongly suggests that the
chemistries of Pu and Ce are not the same, and this is another example
of the failure of Ce as a surrogate
