Hydrotalcite-like compounds were synthesized by coprecipitation using a constant-pH method. Aluminum was introduced in the form of an octahedral aluminum fluorine complex during the synthesis. Controlling the pH during the synthesis ensured that aluminum fluorine did not decompose to tetrahedral species but remained in the octahedral (AlF(6))(3-) form to be incorporated into brucite-like sheets. The physicochemical, thermal, and spectroscopic characterizations showed significant modifications by fluorine introduction regarding structural, textural, and adsorption properties. The memory effect of fluorinated hydrotalcites differed from the memory effect commonly observed in fluorine-free hydrotalcites. Nitromethane adsorption showed that the basicity of hydrotalcite was greatly modified by the fluorine loading.
Maya Blue-like pigments were prepared by two routes using a palygorskite from the Maya region. Synthetic indigo was used as a dye in one case, while the other used the anĩl plant (Indigofera suf fructicosa). Both synthetic and natural Maya Blue pigments were aged and characterized in order to clarify the interaction of the dye-palygorskite. Natural and synthetic fresh Maya Blue pigments were very different; the synthetic ones obviously stabilized the indigo molecule probably at the clay surface and may be in the grooves, but the natural ones stabilized indoxyl molecules in the tunnels and over time oxidized to indigo. The presence of indigo, originating from the anĩl plant, into palygorskite tunnels was evidenced in aged natural pigments by 29 Si, 27 Al, 13 C, and 129 Xe NMR. The persistence of color was evaluated as a function of leaching dye under acidic conditions.
Sodium zeolite X and sodium zeolite A have been exchanged with cesium solutions prepared from three
cesium salts (chloride, nitrate, and acetate). Depending on the solution, the cesium cations were found to be
located in different sites of the zeolite networks. If cesium acetate solution is used, then cesium reaches sites
SII and SIII in the large cavity whereas if nitrate or chloride solutions are put in contact with zeolites, cesium
is positioned only in sites SIII. This distribution determines the leaching behavior of the studied zeolites.
When the samples were thermally treated to encapsulate partially the cesium cations, it was found that their
behavior was different from the one observed in a previous work on cobalt exchanged X and A zeolites
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.