RESUMEN
Sorption of aspartic and glutamic aminoacids by regeneration of calcined hydrotalcite is reported. Hydrotalcite was synthesized by coprecipitation and calcined at 773 K. Sorption experiments were performed at 298 K and 310 K, and the results reveal that at low aminoacids equilibrium concentrations, intercalation of hydroxyl anions takes place while at high equilibrium concentrations, the sorption process occur by means re-hydration and aminoacids intercalation of hydrotalcite. The results also suggested that Asp and Glu sorption is a temperature dependent process. The amount of sorbed amino acid decreases as the temperature increase. The effect is more pronounced for Glu sorption probably due to its higher hydrophobic character, which makes the sorption more difficult in comparison with sorption of Asp at higher temperature.
RESUMEN
Zn(II)-Cr(III)-LDHs (layered double hydroxides) containing sulfated or sulfonated surfactants as the interlamellar anion were synthesized by the coprecipitation method. The syntheses were conducted under various different experimental conditions, such as the Zn : Cr ratio, pH, and aging time. In each of the prepared materials, unlike previously reported data, the interlayer anion arrangement did not change, being consistent with a perpendicular monolayer. The thermal decomposition process of the prepared materials was studied by a set of analysis methods, such as TG/DTA, TG/MS, PXRD, and FT-IR. From the results obtained it was possible to conclude that, in an air atmosphere, the anions decomposed by a partial combustion, leading to the formation of sulfide. The results also showed that sulfonated surfactants containing LDHs are much more stable than those containing sulfated surfactants. A mechanism was proposed for the thermal decomposition of such LDHs based on the experimental results.