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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.

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.

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

We report the first experimental investigation of porous organic cages (POCs) for the demanding challenge of SO 2 capture.T hree structurally related N-containing cage molecular materials were studied. An imine-functionalized POC (CC3) showed modest and reversible SO 2 capture,while as econdary-amine POC (RCC3) exhibited high but irreversible SO 2 capture.Atertiary amine POC (6FT-RCC3) demonstrated very high SO 2 capture (13.78 mmol g À1 ; 16.4 SO 2 molecules per cage) combined with excellent reversibility for at least 50 adsorption-desorption cycles.T he adsorption behavior was investigated by FTIR spectroscopy, 13 CCP-MAS NMR experiments,a nd computational calculations.

Manganese partial substitution reveals a drastic improvement in the electrochemical stability of Li2CuO2 during the charge/discharge processes, this is attributed to the increase in the superexchange interaction between copper sites and manganese.

The rehydration process of calcined MgAl-layered double hydroxides (LDHs), with different Mg/Al molar ratios (2.0, 2.5, 3.0, 3.5, and 4.0), was analyzed at different temperatures and relative humidities. Kinetic results clearly showed that LDHs with Mg/Al molar ratios of 2.5 and 3.0 have the fastest H2O absorption. This behavior was attributed to the cations’ structural ordering and to thermodynamic factors. In addition, results allowed obtaining the activation enthalpies for the LDH regeneration of the different samples as a function of the relative humidity. The different activation enthalpies, for each LDH and independently of the Mg/Al molar ratio, showed that the H2O absorption process is more dependent on temperature if the relative humidity is low. Finally, when we analyzed the activation enthalpies as a function of the Mg/Al molar ratio at a defined temperature, their values did not behave linearly. The water absorption process proved to be more dependent on temperature for the LDHs with molar ratios equal to 2.5 and 3.0.