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Instruments / Technical Area	Publication Details	Published
I11-High Resolution Powder Diffraction	Mechanistic insights into Cs-ion exchange in the zeolite chabazite from in situ powder X-ray diffraction Daniel S. Parsons , Antony Nearchou , Ben L. Griffiths , Sharon E. Ashbrook , Joseph A. Hriljac The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.4c02145 Diamond Proposal Number(s): [26242, 33971] Open Access Show Abstract ▼ Abstract: Zeolites contain extraframework cations that are exchangeable under favorable aqueous conditions; this is the fundamental feature for their application in water purification and necessary to produce cation forms for other applications such as catalysis. Optimization of the process is common, but there is little fundamental understanding based on real-time experiments of the mechanism of exchange for most zeolites. The sodium and potassium forms of zeolite chabazite selectively uptake Cs+ by ion exchange, leading to its application in removing radioactive 137Cs+ from industrial nuclear waste streams, as well as from contaminated environments in the aftermath of the Fukushima and Three Mile Island accidents. In this study, in situ synchrotron powder X-ray diffraction patterns have been collected on chabazite as it undergoes Cs-ion exchange. Applying Rietveld refinement to these patterns has revealed the time-resolved structural changes that occur in the zeolite as exchange progresses, charting the changes in the spatial distribution of the extraframework cations and water molecules in the structure during the reaction. Ultimately, a detailed mechanistic understanding of how this dynamic ion-exchange reaction occurs has been obtained.	May 2024
	The synthesis of gmelinite microspheres and their post-synthetic modification for improved defluoridation Daniel Parsons , Andrew Ingram , Joseph A. Hriljac Separation Science And Technology 27, 1 - 12 DOI: 10.1080/01496395.2023.2212853 Open Access Show Abstract ▼ Abstract: A method for synthesizing microspheres of the zeolite gmelinite (GME) with mean diameter 8 µm, and narrow dispersion, has been developed and establishes the key role of aging the gel prior to heating to produce a narrow size distribution. Fluoride adsorption from acidic media has been evaluated for GME microspheres following post-synthetic modifications by calcium ion exchange, iron(III) surface modification, and dealumination. In each instance, the post-synthetic modification leads to appreciable equilibrium fluoride loadings, with the highest loadings observed for dealuminated GME microspheres, capable of 97.4% fluoride removal from acidified 22 ppm fluoride solutions at equilibrium. Accordingly, dealuminated GME microspheres show promise as a potential adsorbent for reducing the aqueous fluoride content in dangerously high natural sources (up to 30 ppm) to safe drinking levels (≤1.5 ppm) in one treatment.	May 2023
	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
	The influence of intrapore cation on the fluorination of zeolite Y Daniel S. Parsons , David C. Apperley , Andrew Ingram , Joseph A. Hriljac Microporous And Mesoporous Materials DOI: 10.1016/j.micromeso.2020.110470 Open Access Show Abstract ▼ Abstract: The influence of the intrapore cation on the fluorination of zeolite Y from dilute fluoride solutions has been studied, revealing fluoride reacts with the zeolite framework in the presence of a Brønsted acid to form [SiO3F] and [AlO3F] moieties. 29Si{1H} Cross-polarised MAS NMR indicates the reaction proceeds by the substitution of surface hydroxide moieties for fluoride. The fluorination reaction is strongly influenced by the nature of the intrapore cation. Intrapore Brønsted acids facilitate fluorination of the framework by in situ ion-exchange, releasing the acidic ions to the zeolite surface. The fluorination reaction may be further promoted by the presence of intrapore alkaline earth cations (viz. Mg2+, Ca2+, Sr2+ and Ba2+). The conclusions of this work are significant to the preparation of fluorinated zeolite catalysts, the application of zeolites in defluoridation and the labelling of zeolite-based tracers with 18F for application in positron imaging techniques.	Jul 2020
I11-High Resolution Powder Diffraction	Sn6SiO8, a tin(II) silicate with a zinc blende related structure and high thermal stability Daniel S. Parsons , Savvaki N. Savva , Wai Chi Tang , Andrew Ingram , Joseph A. Hriljac Inorganic Chemistry DOI: 10.1021/acs.inorgchem.9b02615 Diamond Proposal Number(s): [12092] Open Access Show Abstract ▼ Abstract: The crystal structure of a novel cubic tin(II) silicate, Sn6SiO8 (space group F4̅3m, a = 10.40708(2) Å, and Z = 4), synthesized by microwave-assisted hydrothermal synthesis has been solved by Rietveld refinement of the powder X-ray diffraction (PXRD) data. The structure, analogous to zinc blende, comprises a face-centered-cubic array of [Sn6O8]4– anions, with Si4+ occupying half of the tetrahedral holes. The tin(II) silicate has been further characterized by variable-temperature PXRD, demonstrating stability of the structure and resistance to SnII oxidation up to ∼600 °C, when the compound begins to thermally decompose.	Dec 2019

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