The mesoporous material Al-Mobil Composition of Matter No. 41 (Al-MCM-41) was successfully obtained from kaolin, a low cost raw material, by means of hydrothermal route. The process of synthesis of Al-MCM-41 was based on calcination of kaolin, dealumination by acid treatment, hydrothermal synthesis in alkaline medium and surfactant extraction. The characterization of the obtained mesoporous material was carried out by techniques such as: X-ray diffraction, infrared vibrational spectroscopy, 29 Si and 27 Al solid state nuclear magnetic resonance, scanning electron microscopy, transmission electron microscopy and N 2 adsorption-desorption. The X-ray diffraction at low angles allowed the determination of the cell parameter, which was 4.02 nm. The analyses of scanning and transmission electron microscopy revealed important morphological properties of the synthesized material. N 2 adsorption/desorption showed a Brunauer-Emmett-Teller (BET) specific surface area of 1,303 m 2 g-1 , pore volume of 1.23 cm 3 g-1 and average diameter of 2.45 nm. The mesoporous material presented a maximum adsorption capacity of 316 mg g-1 for the cationic dye methylene blue (MB) in a concentration typical of industrial effluents, which makes it a potential adsorbent for MB removal from wastewaters.
Este trabalho objetivou desenvolver um compósito a base de celulose, melamina e sílica. A celulose foi obtida dos resíduos de poda da Mangifera indica para o tratamento primário quimicamente assistido de efluentes da indústria têxtil. O compósito foi caracterizado por FT-IR, MEV, MET, TG-DTG e Potencial Zeta. O planejamento composto central foi aplicado para otimização da massa de compósito e tempo de contato na remoção de azul de metileno. O FT-IR mostrou que o compósito apresentou a banda para a melamina em 815 cm-1. O MEV e MET revelaram que na superfície do compósito há Nitrogênio da melamina, Silício e Sódio oriundos do catalisador. O TG-DTG mostrou que o compósito é termicamente mais estável que a celulose, com 65% de degradação. Pelo potencial zeta, valores de pH acima de 5 propiciam maior estabilização e incremento do caráter aniônico do compósito. Escolheu-se como a melhor condição para a aplicação 60 mg de compósito e 30 minutos de tempo de contato, com remoção de 88,6 ± 3,5% do azul de metileno. O estudo do pH revelou que acima de 5, o compósito é mais eficiente. O processo de adsorção do corante pelo material apresentou-se coerente ao modelo de Langmuir (R2 = 0,9921). Assim, o compósito de celulose-melamina-sílica desenvolvido foi eficaz na remoção do corante azul de metileno, apresentando-se como um material de baixo custo, biodegradável e eficiente, com potencialidades para a aplicação no tratamento dos efluentes da indústria têxtil.
Melamine-formaldehyde based composites are versatile and can be applied in the treatment of contaminated effluents such as landfill leachate that have a high pollutant load, as they are rich in nitrogen atoms, the sites allow interaction with molecules, atoms or ions of interest. Aiming compares the efficiency of two materials based on the same precursors, evaluating the efficiency of two composites, melamine-silica (PMF-Si) and melamine-silica-cellulose (Cel-M-Si) in removing iron and ammonia nitrogen in landfill leachate. Adsorption kinetics showed that PMF-Si and Cel-M-Si composites adsorb iron from 30 min, with an average removal of ~ 93.4%. Application of Cel-M-Si to removed leachate ca. 75.7% iron and 76.6% ammonia nitrogen. In contrast, it was observed that PMF-Si had a removal efficiency of 70.9% for iron and 55.0% for ammonia nitrogen. The comparative tests allowed to conclude that the composites PMF-Si and Cel-M-Si have potential for the treatment of landfill leachate, being low cost materials and easy synthesis.
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