Prediction of Solution Behavior via Calorimetric Measurements Allows for Detailed Elucidation of Polyoxometalate Transformation.

The solution behavior of a polyoxometalate cluster, LiNa-UPp (LiNa[(UOO)(PO)]) that consists of 24 uranyl ions, peroxide groups, and 12 pyrophosphate linkers, was successfully predicted based on new thermodynamic results using a calorimetric method recently described for uranyl peroxide nanoclusters (UPCs), molybdenum blues, and molybdenum browns. The breakdown of LiNa-UPp and formation of U (Li[UOOOH]) was monitored via Raman spectroscopy using a custom heating apparatus. A combination of analytical techniques confirmed the simultaneous existence of UPp and U midway through the conversion process and U as the single end product.

In situ Raman spectroscopy of uranyl peroxide nanoscale cage clusters under hydrothermal conditions.

Aqueous solutions containing the nanoscale uranyl peroxide cage clusters U, [(UO)(O)(OH)], and UOx, [{(UO)(O)}(CO)], were monitored by in situ Raman spectroscopy during stepwise heating to 180 °C. In solutions containing U, clusters persist to 120 °C, although conversion of U to U, [(UO)(O)(OH)], occurs above 100 °C. UOx persisted in solutions heated to 150 °C, although partial conversion to smaller uranyl peroxide clusters species was observed beginning at 100 °C.

Transformation of Uranyl Peroxide Studtite, [(UO)(O)(HO)](HO), to Soluble Nanoscale Cage Clusters.

The dissolution behavior of uranyl peroxide studtite, [(UO)(O)(HO)](HO), was examined under a wide range of alkaline aqueous environments with and without the addition of hydrogen peroxide. In the absence of added HO, studtite dissolved in aqueous solutions with a tetraethylammonium hydroxide to uranium molar ratio greater than 0.5, and the resulting species in solution characterized by Raman spectroscopy and electrospray ionization mass spectrometry (ESI-MS) is the uranyl peroxide nanocluster U, [(UO)(O)(OH)].

Uranyl Peroxide Cage Cluster Solubility in Water and the Role of the Electrical Double Layer.

Uranium concentrations as high as 2.94 × 10 parts per million (1.82 mol of U/1 kg of HO) occur in water containing nanoscale uranyl cage clusters.

Structure and Reactivity of X-ray Amorphous Uranyl Peroxide, U2O7.

Recent accidents resulting in worker injury and radioactive contamination occurred due to pressurization of uranium yellowcake drums produced in the western U.S.A.