In situ powder X-ray diffraction studies of Cs-exchange in the zeolite chabazite

Authors: Dan Parsons (Diamond Light Source) , Antony Nearchou (University of Birmingham) , Joseph Hriljac (Diamond Light Source; University of Birmingham)
Co-authored by industrial partner: No

Type: Conference Paper
Conference: 2022 MRS Fall Meeting
Peer Reviewed: No

State: Published (Approved)
Published: November 2022

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.

Journal Keywords: Cs; in situ; zeolite

Subject Areas: Materials, Chemistry, Environment

Instruments: I11-High Resolution Powder Diffraction

Added On: 30/11/2022 08:26

Discipline Tags:

Zeolites Earth Sciences & Environment Radioactive Materials Physical Chemistry Chemistry Materials Science Nuclear Waste

Technical Tags:

Diffraction X-ray Powder Diffraction