Sites of Lu(III) sorbed to and coprecipitated with hectorite.
The Lu(III) binding mechanisms by trioctahedral smectite hectorite in aqueous systems were investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy. Coprecipitated hectorite (Lu755Hec), its precursor phase (Lu/Brucite), and the surface sorbed hectorite (Lu/SHCa1) were prepared as oriented samples to collect polarized EXAFS (P-EXAFS) data. EXAFS analysis indicated that Lu(III) is 6-fold coordinated by oxygen in Lu/Brucite and in Lu755Hec, and surrounded by Mg/Si shells. The angular dependence of the O and Mg coordination numbers for Lu/Brucite hinted an Lu(III) incorporation in brucite layers. Mg and Si cationic shells were detected at distances suggesting a clay-like octahedral environment in Lu755Hec. EXAFS data for Lu/SHCa1 were consistent with Lu(III) forming inner-sphere surface complexes at hectorite platelets edges, but slightly above/below the octahedral plane. Finally, Lu(III) polyhedra share edge(s) and corner(s) with Si tetrahedra upon sorption to silica (Lu/Silica). Lu(III) binding to silicate oligomers or to silicate groups of the clay basal planes and formation of Lu(III) surface complexes during the coprecipitation experiment are marginal.
Finck
Nicolas
N
Institut fur Nukleare Entsorgung (INE), Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany. Nicolas.finck@ine.fzk.de
Schlegel
Michel L
ML
Bosbach
Dirk
D
D000327:Adsorption; D011232:Chemical Precipitation; D008187:Lutetium / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D056928:X-Ray Absorption Spectroscopy; D014961:X-Ray Diffraction
D017640:Silicates; C013547:hectorite; D008187:Lutetium