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Materials Data on Sr(NO3)2 by Materials Project

Sr(NO3)2 crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. Sr2+ is bonded to twelve equivalent O2- atoms to form corner-sharing SrO12 cuboctahedra. There are six shorter (2.75 Å) and six longer (2.90 Å) Sr–O bond lengths. N5+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All N–O bond lengths are 1.27 Å. O2- is bonded in a distorted single-bond geometry to two equivalent Sr2+ and one N5+ atom.

36 MATERIALS SCIENCE↗

Materials Data on Sr(NO5)2 by Materials Project

Sr(NO3)2(O2)2 crystallizes in the monoclinic C2/c space group. The structure is one-dimensional and consists of eight hydrogen peroxide molecules and two Sr(NO3)2 ribbons oriented in the (1, 0, 1) direction. In each Sr(NO3)2 ribbon, Sr is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Sr–O bond distances ranging from 2.57–2.73 Å. N is bonded in a trigonal planar geometry to three O atoms. There are a spread of N–O bond distances ranging from 1.23–1.32 Å. There are three inequivalent O sites. In the first O site, O is bonded in a distorted water-like geometry to one Sr and one N atom. In the second O site, O is bonded in a 1-coordinate geometry to two equivalent Sr and one N atom. In the third O site, O is bonded in a single-bond geometry to one N atom.

36 MATERIALS SCIENCE↗

Madrid-2019 force field: An extension to divalent cations Sr2+ and Ba2+

In this work, we present a parameterization of Sr2+ and Ba2+ cations, which expands the alkali earth set of cations of the Madrid-2019 force field. We have tested the model against the experimental densities of eight different salts, namely, SrCl2, SrBr2, SrI2, Sr(NO3)2, BaCl2, BaBr2, BaI2, and Ba(NO3)2. The force field is able to reproduce the experimental densities of all these salts up to their solubility limit. Furthermore, we have computed the viscosities for two selected salts, finding that the experimental values are overestimated, but the predictions are still reasonable. Finally, the structural properties for all the salts have been calculated with this model and align remarkably well with experimental observations.

Chemistry↗

Strontium Speciation in Relevant Tank Waste Components Examined by Electrospray Ionization Mass Spectrometry

The identification of chemical species formed in complex nuclear waste is crucial for the development and employment of advanced separations technologies to remediate the Hanford site by processing tank waste. The current Tank Side Cesium Removal (TSCR) process deployed at Hanford utilizes crystalline silicotitanate (CST) ion exchange (IX) media to aid in the separation of low-activity waste for proper treatment and disposal. The inorganic IX media is highly selective for Cs but has been shown to also remove Sr from caustic simulants and small-scale IX processing of Hanford tank waste.(Fiskum, Rovira et al. 2019, Fiskum, Campbell et al. 2021, Westesen, Campbell et al. 2022) Quantitative Sr removal has not been observed in all tank waste supernates tested; thus, to better understand Sr removal and effectively predict processing behavior through TSCR, it is necessary to first investigate Sr speciation in tank waste. This work utilized electrospray ionization mass spectrometry (ESI-MS) to identify ionic Sr complexes that form in the presence of NO 3 –, NO 2 –, OH–, and Cl–. Although our results show that NO 3 –, NO 2 –, and OH– are competitive for Sr 2+ binding, previous data from IX studies indicate that [SrOH] + is not the dominant species of concern in tank waste processing schemes.(Fiskum, Campbell and Trang-Le 2020) Our results show that the [Sr(NO3)]+ species and the [Sr(NO2)] + species form in considerable abundances, which may affect the ability to separate Sr using CST in nuclear waste separation processes.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗