Structural incorporation of Cm(III) in trioctahedral smectite hectorite: A time-resolved laser fluorescence spectroscopy (TRLFS) study

Sorption of Cm(III) and Gd(III) onto gibbsite, α-Al(OH)3: A batch and TRLFS study

“…Complete loss of the hydration sphere is reported for Cm included in various mineral structures with lifetimes exceeding 500 μs [22]. However, Cm coprecipitation with another solid hydroxide, brucite, Mg(OH) 2 , resulted in a shift of the Cm fluorescence emission to 610.8 nm and a lifetime of only 165 μs [24], similar to our observations. Lifetimes at 180-200 μs may be interpreted by insertion of Cm species into the gibbsite or coprecipitated structure keeping 2.4-2.7 H 2 O/OH − entities in its primary hydration sphere.…”

Am(III) coprecipitation with and adsorption on the smectite hectorite

“…Syntheses of the magnesian smectite hectorite in the presence of An(III) or Ln(III) (used as non-radioactive chemical surrogates of actinides) have been reported. Luminescence data collected for hectorite crystallized in the presence of Cm(III) (Brandt et al, 2007) or Eu(III) (Finck et al, 2008) were consistent with incorporation in the bulk structure. Recent X-ray absorption spectroscopy (XAS) data also showed the possibility of incorporating Lu(III) in the octahedral sheet of hectorite (Finck et al, 2009).…”

“…In the Am coprecipitation experiment (sample AmCopHec), part of the magnesium was replaced by americium and the synthesis protocol was adapted as follows. The freshly precipitated and washed Am-containing brucite was aged in the presence of the reactants (LiF, silica sol) for 6 days at 90°C (Brandt et al, 2007) in a tightly closed Teflon inner-coated vessel. After synthesis, AmCopHec was also washed at pH~3 prior to further analyses.…”

Stability of lanthanum-saturated montmorillonite under high pressure and high temperature conditions

“…Due to isomorphic substitutions in the octahedral and tetrahedral sheets, a net negative charge is established in the structure; this charge is balanced through cation adsorption, usually in the interlayer spaces, which results in a high cation exchange capacity (CEC) (Bergaya et al, 2006). In addition to the adsorption of mono-and divalent cations such as Na + , K + , and Ca 2+ , smectite can also adsorb trivalent elements (e.g., trivalent rare earth elements (REE 3+ ) and trivalent actinides), as has been shown in several studies (Takahashi et al, 1998;Stumpf et al, 2001;Bradbury and Baeysns, 2002;Coppin et al, 2002;Stumpf et al, 2002;Coppin et al, 2003;Stumpf et al, 2004;Rabung et al, 2005;Brandt et al, 2007;Tan et al, 2010). Due to these and other features, smectites are used as geochemical barriers in different contexts including secondary barriers for deep nuclear waste disposal (Pusch, 1998), where smectites are employed to adsorb actinide trivalent cations.…”

“…The different reaction mechanisms between clay minerals and cations are as follows: outer-sphere interaction, inner-sphere interaction, cation exchange within the interlayer spaces, and structure incorporation in the octahedral layer (Takahashi et al, 1998;Strawn and Sparks, 1999;Stumpf et al, 2001;Bradbury and Baeysns, 2002;Coppin et al, 2002;Stumpf et al, 2002;Coppin et al, 2003;Stumpf et al, 2004;Rabung et al, 2005;Brandt et al, 2007;Tan et al, 2010). The different modes of clay mineral-cation interaction are highly dependent on the pH of the surrounding environment.…”