Exploring the influence of pH on the structural intricacies of uranium oxide hydrates containing both Cd(ii) and K(i) ions

Abstract

We report the synthesis of two new dual-cation uranium oxide hydrate (UOH) materials, containing both Cd2+ and K+ ions, along with their characterisation by means of single-crystal X-ray diffraction and...

Filling the gaps of uranium oxide hydrates with magnesium(ii) ions: unique layered structures and the role of additional sodium(i) ions

“…It is essential to understand the alteration chemistry of uranium oxides in the presence of transition metal ions given their abundance in the environment. With only a few UOH materials containing transition metal ions being reported, 31–34 there is an obvious need for further work. Many bivalent 3d/4d-transition metal ions (M 2+ = Mn, Co, Ni, Cu, Zn, Cd) have ionic radii ranging from 0.69 to 0.95 Å with the corresponding r (M 2+ )/ r (O 2− ) ratios in the range 0.73–0.41, characteristic of the octahedral coordination geometry for M 2+ ions.…”

“…Hydrolysed uranyl species such as [UO 2 (OH)] + , [(UO 2 )(OH) 2 ], [(UO 2 ) 2 (OH) 2 ] 2+ and [(UO 2 ) 3 (OH) 5 ] + increase when the solution pH is above 5. 33 Most of the UOH phases were synthesised hydrothermally with solution pH values from 3 to 6. However, UOH phase formation in slightly alkaline solutions has been less investigated.…”

“…19–22 In addition, the uranyl oxide hydroxide layer topologies for various UOH minerals have been comprehensively reviewed. 23 In addition, synthetic UOH materials with a wide range of secondary cations including alkali, 24,25 alkaline earth, 26–29 lead, 30 transition metals 31–33 and lanthanide ions 34–36 have been reported. Furthermore, synthetic UOH phases with interlayer anions are also possible, although less studied.…”

Capturing ammonium nitrate in a synthetic uranium oxide hydrate phase: revealing the role of ammonium ions and anion inclusions

“…11 In terms of secondary cations for the synthetic UOH materials, alkali and alkaline earth metal ions dominate. 12–18 However, UOHs with transition metals, 19–22 lead 23 and lanthanide ions 24–26 have also been studied and reported recently.…”

Investigation of uranium oxide hydrates with barium(ii) ions: structural diversity, uranium valences and implications

“…22 Hydrothermal synthesis in the laboratory has been used to assist the formation of the UOH compounds in a simulated natural environment. To date, more than two dozen of synthetic UOH compounds have been made with interlayer cations including alkali, 23,24 alkaline earth, 25,26 lead, 27 limited 3d transition metal [28][29][30] and lanthanide ions. [31][32][33][34] Complicating these UOH systems are a further number of compounds which have a slightly different structure where the apical oxygen of the uranyl ions on the layer shares the equatorial oxygen with an interlayer uranyl ion acting as a pillar, resulting in an open three-dimensional (3D) framework structure typically incorporating various cations in the framework channels.…”