Thermal decomposition of Australian uranium ore concentrates: characterisation of speciation and morphological changes following thermogravimetric analysis

Phase Analysis of Australian Uranium Ore Concentrates Determined by Variable Temperature Synchrotron Powder X-ray Diffraction

“…Mass balance calculations, based on the quantitative phase analysis and ideal stoichiometry for the phases, gave the following water contents: Olympic Dam mine 3.6 wt % H 2 O, Ranger mine 4.6 wt % H 2 O, and Beverley mine 10.7 wt % H 2 O. These results are in broad agreement with the thermogravimetric analyses of Ditcham et al 10 The results presented in Structural Refinement of Metastudtite. We are unaware of any previous high-resolution structural studies of metastudtite.…”

“…Interestingly, the differences are more significant than evident in the results obtained 2 years prior to using a conventional Cu source (Bruker D8 diffractometer) reported by Ditcham. 10 These differences are highlighted in the supplementary Figures S1−S3. It appears that during a prolonged storage, U 3 O 8 has reacted with the atmosphere and partially converted to α-UO 2 (OH) 2 and α-(UO 2 ) 4 O(OH) 6 •5H 2 O.…”

“…The Beverley mine UOC is nominally UO 4 ·2H 2 O and was yellow/orange in color on receipt at ANSTO and in 2017. Further details and the production methods for the UOC samples are given elsewhere. , The samples were stored in the containers in which they were collected at the respective mine sites, either plastic screw-top bottles or zip-lock bags. Each container was placed within secondary containment (another zip-lock bag) and stored in a cupboard in an air-conditioned laboratory (22 °C, relative humidity 40%), and only opened for subsampling on several occasions over the ∼10 year period.…”

“…Keegan et al 9 determined the concentrations of 40 minor and trace elements in UOC from these three Australian mines and was able to use this information to build characteristic elemental and isotope signatures for the samples. Ditcham and co-workers, 10 working with the same bulk samples as Keegan,9 demonstrated that a combination of differential thermal analysis, thermogravimetric analysis, and powder X-ray diffraction (PXRD) could be used to differentiate between the original sources; however, a number of minor phases in the UOCs could not be fully characterized. An interesting observation in that work was that the temperature at which various intermediate phases formed during the thermal decomposition measurements depended on the origin of the sample.…”

“…Samples were adhered onto double-sided carbon tape and mounted on Si single crystals in preparation for XRD analysis. 10 Finely ground subsamples of the UOC samples were placed in 0.2 mm quartz glass capillaries that were then flame sealed. Synchrotron X-ray diffraction (S-XRD) data were measured on the powder diffraction (PD) beamline at the Australian Synchrotron operating at around 16 keV (0.728938 Å based on calibrations using a NIST LaB 6 (660b) standard reference) using an array of 16 MYTHEN II microstrip detectors.…”