Uranyl surface complexation on smectites: Combining optical spectroscopic studies with modeling

Conference · Wed Dec 31 04:00:00 EST 1997

OSTI ID:560049

Morris, D E; McKinley, J P; Smith, S C; Zachara, J M ^[1]

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

The surface complexation reactions of aqueous UO{sub 2}{sup 2+} (uranyl) species with reference smectites (SAz-1 and SWy-1) and a smectitic isolate from soil (LK-1) have been investigated by a combination of thermodynamic modeling of batch sorption reactions and optical luminescence spectroscopy of the uranyl surface species. From a comparison of the spectroscopic data derived from the reference clays and model systems (e.g., aqueous species and sorption complexes on simple oxide phases), and constraints in surface complexation imposed by the solution conditions of the sorption reactions, we have established unambiguous luminescence signatures for monomeric uranyl surface complexes in fixed-charge basal plane sites and inner-sphere edge (Al-O and SiO) sites. These spectroscopic data have provided a mechanism to distinguish between several plausible surface complexation schemes suggested by modeling under reaction conditions that allow for many possible surface complexes. Recent results for the LK-1 system as a function of pH (4 to 8) and ionic strength (0.001 to 0.1 M) will be highlighted.

• OSTI ID: 560049
• Report Number(s): CONF-970443--
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
54 ENVIRONMENTAL SCIENCES
CHEMICAL BONDS
CLAYS
LUMINESCENCE
PH VALUE
SMECTITE
SORPTION
URANIUM DIOXIDE
URANYL COMPLEXES