Navegando por Autor "Lopes, Christian W."
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Artigo Fluoride-mediated synthesis of TON and MFI zeolites using 1-butyl-3- methylimidazolium as structure-directing agent(Elsevier, 2017-11-01) Pergher, Sibele Berenice Castellã; Lopes, Christian W.; Hortigüela, Luis Gomez; Rojas, AlexIn this work, 1-butyl-3-methylimidazolium (1B3MI) cation has been employed as a structure-directing agent for the synthesis of pure silica and Ti-containing zeolites in fluoride media. The 1B3MI OSDA exhibited distinct phase selectivity depending on the synthesis conditions, and particularly the concentration of the synthesis gel. Thus, under more diluted conditions (H2O/SiO2 ¼ 14), the 1B3MI cation yielded pure silica TON zeolite with high crystallinity. Attempts to obtain Ti-containing zeolites, however, failed at this diluted condition even after 15 days of synthesis. In contrast, highly crystalline Ti-MFI was the only phase obtained upon reducing the H2O/SiO2 molar ratio from 14 to 7. The presence of Ti in the MFI zeolite framework was confirmed by both infrared and DRS UV-vis spectroscopies. The presence of intact OSDA molecules within the micropores was inferred from elemental analysis and 13C CP-MAS NMR spectroscopy. On the other hand, thermogravimetric analyses showed a different packing of the 1B3MI cation in the pure silica TON and Ti-MFI samples. Moreover, the environments for Si and F species in the as-made materials were investigated by means of 29Si and 19F MAS NMR, respectively. Finally, molecular simulations showed that the most stable arrangement of the 1B3MI cations involves the location of the imidazolium rings on the channel intersections and of the butyl chains on the sinusoidal channelsArtigo Modification of Activated Carbon for the Adsorption of Humic Acid(SAGE Publications, 2015-02-01) Eustáquio, H. M. B.; Lopes, Christian W.; Rocha, Rafael S. da; Cardoso, Brena D.; Pergher, Sibele Berenice CastellãCommercial activated carbon treated with sulphuric and phosphoric acids was used to remove humic acids (HAs) from water. To achieve this goal, the iodine indices of treated and untreated materials were characterized by X-ray diffraction and nitrogen physisorption. Adsorption assays for HAs evaluated the quantities adsorbed after a fixed time. Temporal evolution of HA adsorption was determined from the adsorption kinetics. Experimental results indicated that the sulphuric acid treatment was more efficient and had a higher HA adsorption at each time point evaluated. Evaluating the specific area helped to verify this fact, reflecting the number of mesopores in the used material