The hydrothermal reaction of PuCl3 or CeCl3 with TeO2 in the presence of sulfuric acid under the comparable conditions results in the crystallization of Pu(TeO3)(SO4) or Ce2(Te2O5)(SO4)2, respectively. Pu(TeO3)(SO4) and its isotypic compound Th(TeO3)(SO4) are characterized by a neutral layer structure with no interlamellar charge-balancing ions. However, Ce2(Te2O5)(SO4)2 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. Pu(TeO3)(SO4), Th(TeO3)(SO4), and Ce2(Te2O5)(SO4)2 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.

The incorporation of neptunium(VI) into the layered uranyl selenite Cs[(UO(2))(HSeO(3))(SeO(3))] has yielded the highest level of neptunium uptake in a uranyl compound to date with an average of 12(±3)% substitution of Np(VI) for U(VI). Furthermore, this is the first case in nearly 2 decades of dedicated incorporation studies in which the oxidation state of neptunium has been determined spectroscopically in a doped uranyl compound and also the first time in which neptunium incorporation has resulted in a structural transformation.

Neptunium incorporation in the torbernite/meta-torbernite [Cu-(UO 2 ) 2 (PO 4 ) 2 •nH 2 O] system has been investigated in this study under both hydrothermal and slow diffusion conditions (at room temperature and 90 °C) to examine the role synthetic conditions play on neptunium uptake by uranyl phases and whether hydrothermal incorporation studies feasibly model environmental incorporation. The hydrothermally prepared crystals contained approximately 19 ± 2 and 73 ± 3 times more neptunium on average than crystals grown during slow diffusion at room temperature and elevated temperature, respectively. UV−vis spectroscopy on the mother solution showed that, on average, 51.53(±0.04)% of the original neptunium-(V) remains in solution following hydrothermal synthesis versus 37.24(±0.04)% following slow diffusion at room temperature and 73.62(±0.07)% at 90 °C. Additionally, solid-state UV−vis-NIR indicated that the incorporated neptunium was predominantly present in the +6 oxidation state in the hydrothermal samples despite the fact that the initial oxidation state of neptunium in solution was +5 and no oxidizing species were present in the reactions. The oxidation state of neptunium in the slow diffusion samples was not able to be determined due to the low incorporation levels. These results suggest that neptunium(VI) may play a more significant role than previously expected in geological repositories.

To promote student involvement in the reduction of chemical waste generated by teaching laboratories, a method published by Flinn Scientific for the treatment of waste sodium molybdate has been modified for use in treating waste generated by the popular molybdenum blue method for the analysis of phosphate in natural water samples. In this teaching laboratory, students convert molybdenumcontaining anions in their phosphate lab waste to the corresponding insoluble calcium salts for disposal of the precipitate in the trash and disposal of the filtrate down the drain. Determination of a percent yield is offered as an additional experiment. Considerable evidence is presented that this revised method for waste treatment decreases molybdenum levels in the filtrate to levels well below stated limits for sink/sewer disposal.