title: Zn2Al layered double hydroxides intercalated and adsorbed with anionic blue dyes: a physico-chemical characterization.
abstract: 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.
authors.affiliation: Centro de Pesquisas em Química Aplicada, Departamento de Química, Universidade Federal do Paraná, UFPR, CP 19081, 81531-990, Curitiba, Paraná, Brazil.
authors.forename: Rafael
authors.initials: R
authors.lastname: Marangoni
authors.forename: Mustapha
authors.initials: M
authors.lastname: Bouhent
authors.forename: Christine
authors.initials: C
authors.lastname: Taviot-Guého
authors.forename: Fernando
authors.initials: F
authors.lastname: Wypych
authors.forename: Fabrice
authors.initials: F
authors.lastname: Leroux
mesh_terms: D000327:Adsorption; D017607:Aluminum Compounds / Q000737:chemistry*; D000838:Anions / Q000737:chemistry; D004396:Coloring Agents / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry*; D015394:Molecular Structure; D013499:Surface Properties; D013696:Temperature; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D017607:Aluminum Compounds; D000838:Anions; D004396:Coloring Agents; D006878:Hydroxides; D017967:Zinc Compounds