Papers by Keyword: Anionic Clays

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Authors: Laura Dartu, Carmen Zaharia, Gabriela Carja
Abstract: This work reports hydrotalcite and zinc-substituted hydrotalcite (MeAlLDHs) anionic clays as novel catalytic formulations for some environmental applications regarding specific industrial coloured effluents. In this context, layered double hydroxides, covered or with tailored compositions, were synthesized, characterized using advanced analytical analysis techniques (XRD, FTIR, SEM) and tested in specific environmental applications. More specifically, LDHs samples were tested as catalysts for different treatments of coloured effluents, especially some advanced oxidation processes (i.e. heterogeneous advanced oxidation processes with H2O2 of Orange 16 dye-containing effluent). The influence of some operating factors such as catalyst type, concentration of hydrogen peroxide, presence of ferrous ions or UV light, contact time was studied, and the adequate operating values were established. Results show that Orange 16 removal is more than 70%, in specific operating conditions, for two of new tested materials (ZnAlLDH 3:1, and MgAlLDH 3:1). Moreover, the action of UV radiation was found efficient in decomposition of Orange 16 dye in the presence of all four tested catalytic materials, improving with more than 40-50% the color removal.
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Authors: Salah Bahah, Saci Nacef, Derradji Chebli, Brahim Djellouli, Abdallah Bouguettoucha
Abstract: In order to search the correlation between textural properties and geometrical heterogeneity in clays, as characterized by the surface fractal dimension, we used, three different cationic clays; namely Kaolin of Hamam Dbagh, Montmorillonite (Mt) of Maghnia and a sample prepared from Sodium Montmorillonte (Na-Mt)) and three different synthetic anionic clays, ZnAlCO3, MgAlCO3 at a molar ratio equal to three (R=3), and NiAlCO3 with different molar ratios (R=2, R=3 and R= 4). This DS parameter was evaluated from nitrogen (N2) analysis gas. the fractal Frenkel-Halsey-Hill (FHH) (DS) models was used to estimate the surface fractal dimensions at two ranges of relative pressure, the first between 0.08 and 0.22, which were found Ds to be 2.59, 2.53 and 2.68 from Kaolin, Montmorillonite and Sodium Montmorillonte clays respectively and 2.33, 2.61, 2.53, 2.56 and 2.56 for ZnAlCO3 and MgAlCO3, NiAlCO3 (2, 3 and 4) respectively, and other at medium relative pressure, which there was an excellent linear adjustment for F-H-H equation within the range between 0.37 and 0.82, which were found Ds to be 2.77, 2.64 and 2.82 for Kaolinite, Montmorillonite and Sodium Montmorillonte clays respectively, and 2.68, 2.64, 2.40, 2.60, 2.47 for ZnAlCO3, MgAlCO3, NiAlCO3 (2, 3 and 4) respectively. SEM Characterization confirmed the heterogeneous distribution of the particles and the BET analysis confirmed the fractal nature of the surface of these materials. The zeta potential of the sample which is most used as an indicator of dispersion stability, show a proportionality between increases of zeta potential with increase of dimension fractal (DS), for the same type of clays ( (NiAlCO3) with (R=2, 3 and 4) and Mt, Na-Mt). Key words: Anionic clays; Cationic clays; Fractal dimension; geometrical heterogeneity; Frenkel-Halsey-Hill model.
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