Coprecipitation of trace metal ions during the synthesis of hectorite

The transformation of synthetic hectorite in the presence of Cu(II)

“…Such sites can occur in the structure or at the inner surface, i.e. interlayers and hexagonal cavities of the hectorite (Clementz et al, 1973;Luca et al, 1991;Karakassides et al, 1999;Spagnuolo et al, 2004). The spectral parameters g || = 2.42 and A || = 10 mT, obtained from low-temperature measurements, are similar to the parameters determined by Luca et al (1991) and assigned to structure-bound Cu(II).…”

“…Decarreau (1981) showed that, during synthesis, Mg(II) can be substituted by Cu(II) to a certain extent. This was confirmed for the co-precipitation of hectorite in the presence of Cu(II) during hydrothermal synthesis, while this was not the case if synthesized hectorite was reacted with a Cu(II) solution at room temperature (Spagnuolo et al, 2004). On the other hand, Mosser et al (1997) postulated, based on electron paramagnetic resonance (EPR) spectra, that heating of Cu(II)-exchanged hectorite to~200À300ºC led to migration of Cu(II) into the structure, and offered the Hofmann-Klemen effect to explain this behavior.…”

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

“…For example, like transition metal ions, the actinides Am or Cm form inner-sphere surface complexes upon interaction with clay minerals in suspension (Geckeis et al, 2013). Because clay octahedral sheets are able to accommodate divalent and trivalent cations of large sizes, such as Cd(II) (Spagnuolo et al, 2004) or Lu(III) (Finck et al, 2009), the size (up to a certain limit) and the charge of the incorporated cation are not limiting factors. The structural incorporation of An(III) may not only result from coprecipitation, but surface retention followed by epitaxial growth may also lead to actinides located within a clay-like structure.…”

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

“…Complementary to natural systems studies, clay minerals can be synthesized under controlled laboratory conditions. Spagnuolo et al (2004) synthesized hectorite from an aqueous solution at 100°C in the presence of various environmentally relevant cations-Cu(II), Zn(II), Pb(II), and Cd(II). Electron paramagnetic resonance (EPR) spectroscopy combined with EDTA extraction procedures indicated that significant fractions of Cu(II) (and Zn(II)) occupy an octahedral lattice site.…”