The characterisation by luminescence spectroscopy of uranium(VI) incorporated into zeolites and aluminas

Abstract

Luminescence spectroscopy of solids at 77 K has been used to characterise the uranium(VI) species incorporated into [alpha]-alumina, [gamma]-alumina and zeolites Y and ZSM-20 by adsorption from solution and into ZSM-5 by chemical synthesis. With uranyl adsorbed from nitrate solutions onto [alpha]- and [gamma]-aluminas, the luminescence measurements show the dominant uranium species is schoepite, UO3·xH2O, in agreement with results from X-ray diffraction and Raman spectroscopy. With uranyl acetate, there are indications that a crystalline acetate species is also present. With zeolite-Y and ZSM-20, the main species is a dimer. In addition, some monomeric [UO2(H2O)5]2+ is also present. With ZSM-5, although this is not observed in X-ray diffraction, the luminescence spectrum shows the presence of a species, similar to the schoepite seen with the aluminas. It is suggested that this may be due both to closely related polymeric species, and to uranyl anions, such as [UO2(OH)4]2- and [UO2(OH)3]-.