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

Luminescence spectroscopy of solids at 77 K has been used to characterise t he uranium(VI) species incorporated into cr-alumina, gamma -alumina and zeo lites Y and ZSM-20 by adsorption from solution and into ZSM-5 by chemical s ynthesis. With uranyl adsorbed from nitrate solutions onto alpha- and gamma -aluminas, the luminescence measurements show the dominant uranium species is schoepite, UO3. xH(2)O: in agreement with results from X-ray diffractio n and Raman spectroscopy. With uranyl acetate, there are indications that a crystalline acetate species is also present. With zeolite-Y and ZSM-20. th e 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 diffracti on, the luminescence spectrum shows the presence of a species, similar to t he schoepite seen with the aluminas. It is suggested that this may be due b oth to closely related polymeric species, and to uranyl anions, such as [UO 2(OH)(4)](2-) and [UO2(OH)(3)](-). (C) 2001 Elsevier Science B.V.. All righ ts reserved.