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Instruments / Technical Area	Publication Details	Published
	Doped umbite materials for selective abatement of cesium radionuclides from nuclear waste streams Antony Nearchou , Tzu-Yu Chen , Daniel S. Parsons , Luke O’brien , Nicholas A. Hodge , Liam Abrahamsen-Mills , Phoebe K. Allan , Jospeh A. Hriljac Apl Materials 11 DOI: 10.1063/5.0134977 Open Access Show Abstract ▼ Abstract: Sb- and Nb-doped Zr and Sn-umbites have been prepared using hydrothermal synthesis with both high purity and yield. All four materials display excellent removal of Cs+ cations from acidic, neutral, and basic solutions, abating at least 80% of the Cs present. This performance is retained in the presence of competing Na+ cations as well as across the pH range. The most sustained selectivity is observed in acidic media, with evidence of a minor reduction in selectivity under basic conditions. The umbites have successfully been shaped into pellets, introducing macroporosity and retaining the selective uptake of Cs in the presence of excess Na. Through thermal treatment, samples of partially Cs-exchanged umbite can be converted into dense silicate phases where radioactive Cs can be immobilized in a potential wasteform for long term storage. These findings present doped umbites as prospective materials for industrial use with selective abatement properties and capabilities for deployment followed by end of life geological disposal.	Jan 2023
I11-High Resolution Powder Diffraction	In situ powder X-ray diffraction studies of Cs-exchange in the zeolite chabazite Dan Parsons , Antony Nearchou , Joseph Hriljac 2022 MRS Fall Meeting Show Abstract ▼ Abstract: The sequestration of relatively long-lived radionuclides such as 137Cs (t½ = 30.2 years) from aqueous nuclear waste streams, or from aqueous environments contaminated with nuclear waste, is significant in nuclear waste management. A favoured option for the removal of radioactive cations are zeolites: porous crystalline aluminosilicates adopting framework structures comprising corner-shared [SiO4] and [AlO4] tetrahedra, with exchangeable cations occupying the hydrated pores and cages of the framework. Chabazite is a particular zeolite that is efficacious in the selective removal of aqueous Cs+ by ion exchange and has been applied in decontamination efforts at Fukushima. The crystallographic positions occupied by extraframework cations, such as Na, K and Cs, within the chabazite crystal structure are well established when the material contains exclusively one type of cation; however, the mechanism by which ion exchange occurs in these materials has not been previously probed despite the inherent advantages to enhancing the understanding of this process. In this study, powder X-ray diffraction (PXRD) patterns have been collected, on beamline I11 at the Diamond Light Source synchrotron, on chabazite samples as ion exchange occurs, facilitated by a liquid flow cell which elutes a dilute Cs-containing solution through the chabazite sample as data is recorded in situ. Cs-ion exchange has been studied for two chabazite samples, one containing sodium (Na-CHA) and the other potassium (K-CHA). Through applying Rietveld refinement to the in-situ PXRD datasets, time-resolved structural changes are observed as the constitution of extraframework cations changes within the zeolite, providing a mechanistic understanding of how Cs-ion exchange occurs in these materials.	Nov 2022
I11-High Resolution Powder Diffraction	Crystal structures of a cubic tin(II) germanate, α-Sn6GeO8, and a tetragonal tin(II) silicate, γ-Sn6SiO8 Daniel S. Parsons , Antony Nearchou , Joseph A. Hriljac Inorganic Chemistry DOI: 10.1021/acs.inorgchem.2c02053 Diamond Proposal Number(s): [26234, 31055] Open Access Show Abstract ▼ Abstract: A cubic tin(II) germanate, α-Sn6GeO8 (space group F4̅3m, a = 10.52521(2) Å, and Z = 4), has been synthesized by both regular hydrothermal and microwave-assisted hydrothermal methods, and the crystal structure of this material has been solved by Rietveld refinement of synchrotron powder X-ray diffraction (PXRD) data. The crystal structure is analogous to α-Sn6SiO8 and is therefore related to the zinc blende structure comprising a face-centered cubic array of [Sn6O8]4– anionic clusters with Ge4+ cations occupying half of the tetrahedral holes. Variable-temperature PXRD has revealed that tin(II) germanate has high thermal stability: remaining stable at 950 K and mostly decomposing over the range 984–1034 K. The tin(II) germanate has been further characterized by X-ray fluorescence (XRF), Raman, and diffuse reflectance (DR) UV–vis spectroscopies. In addition, variable-temperature PXRD studies have revealed the formation of a tetragonal tin(II) silicate polymorph, γ-Sn6SiO8 (space group I4̅, a = 7.30414(6) Å, c = 10.53731(6) Å, and Z = 2), at temperatures below 170 K. The crystal structure of γ-Sn6SiO8 has been elucidated by Rietveld refinement. While a transition to a tetragonal polymorph is observed upon cooling α-Sn6SiO8, no corresponding transition is observed for α-Sn6GeO8, which retains its cubic structure over the probed temperature range.	Sep 2022

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