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Three different anionic blue organic dyes have been intercalated into the structure of Zn(2)Al layered double hydroxides, using the co-precipitation method at constant pH. Using the same synthetic procedure, Zn(2)Al-Cl has been prepared and used as an adsorptive phase to retain the blue dyes from an aqueous solution. All the organic/inorganic (O/I) hybrid LDH compounds were analyzed by X-ray powder diffraction (XRPD), thermal analysis (TG/DTA), elemental analysis, solid state (13)C nuclear magnetic resonance (CPMAS (13)C NMR), and Fourier transform infrared spectroscopy (FTIR). In the adsorption experiments, Gibbs free energy DeltaG values for the temperatures in a range between 10 and 40 degrees C were found to be negative, which indicates that the nature of adsorption is spontaneous and shows the affinity of LDH material towards the blue anionic dyes. Additionally a decrease in DeltaG values at higher temperature further indicates that this process is even more favorable at these conditions. The enthalpy DeltaH values were between physisorption and chemisorption, and it may be concluded that the process was a physical adsorption enhanced by a chemical effect, characterized by a combined adsorption/intercalation reaction, making these O/I assemblies reminiscent of the Maya blue.

The reaction of natural chrysotile fibers with phenylphosphonic acid leads to a new grafted material. The layered material, with an interplanar basal distance of 15.2 A ˚, was characterized by powder X-ray diffraction, thermal analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and energy dispersive X-ray analysis. The experimental data are consistent with the grafting of phenylphosphonate groups to the surface of the layered silica sheets, obtained by the in situ acidic leaching of brucite sheets, from chrysotile.

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