Optical spectroscopic studies of the sorption of UO[sub 2][sup 2+] species on a reference smectite

Journal Article · Thu Sep 01 04:00:00 EDT 1994 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(94)90153-8· OSTI ID:6556892

Morris, D E; Barr, M E; Eller, P G ^[1]

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1. Los Alamos National Lab., NM (United States)

The speciation of UO[sub 2][sup 2+] (uranyl) on a reference smectite (SAz-1 from Cheto, Arizona, USA) has been investigated by electronic emission and Raman vibrational spectroscopies. The spectroscopic studies have been done on uranyl-bearing clays prepared from aqueous solutions of uranyl nitrate in the pH range from [approximately]2.5 to 7 and high initial ionic strength ([approximately]0.1-0.3 M). The uranyl loading levels in these samples ranged from [approximately]0.1% to [approximately]53% of the reported cation exchange capacity ([approximately]1.2 meq/g). Vibronically resolved emission spectra have been obtained for all samples. These spectra vary significantly in intensity and band-shape as a function of uranyl concentration in the clays and the equilibrium pH of the solutions from which the clays were prepared. For most clay samples the measured emission spectrum is a composite of spectra from multiple uranyl emitters. At the lowest loading levels a uranyl sorption complex with an apparent vibronic spacing of [approximately]750 cm[sup [minus]1] dominates the spectra. At intermediate loading levels an additional uranyl sorption complex also having an apparent vibronic spacing of [approximately]750 cm[sup [minus]1] is present at an approximately constant concentration ratio to the species in the most dilute samples. At the highest loading levels, a uranyl sorption complex with a vibronic spacing of [approximately]850 cm[sup [minus]1] dominates the spectra. Raman spectra have been obtained for the more concentrated uranyl/clay samples. Two distinct bands (855 cm[sup [minus]1] and 883 cm[sup [minus]1]) are seen in the spectral region of the totally symmetric uranyl stretch. The 855 cm[sup [minus]1] band correlates with the dominant high-coverage species, while the 883 cm[sup [minus]1] band arises from an additional sorption complex.

• OSTI ID: 6556892
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 58:17; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400702 -- Radiochemistry & Nuclear Chemistry-- Properties of Radioactive Materials
54 ENVIRONMENTAL SCIENCES
540230* -- Environment
Terrestrial-- Radioactive Materials Monitoring & Transport-- (1990-)
ACTINIDE COMPLEXES
ACTINIDE COMPOUNDS
CLAYS
COMPLEXES
CONTAMINATION
EMISSION SPECTRA
ENVIRONMENTAL TRANSPORT
MASS TRANSFER
MINERALS
PH VALUE
RAMAN SPECTRA
SILICATE MINERALS
SMECTITE
SOILS
SORPTION
SORPTIVE PROPERTIES
SPECTRA
SURFACE PROPERTIES
URANIUM COMPLEXES
URANIUM COMPOUNDS
URANYL COMPLEXES
URANYL COMPOUNDS