Renata Martins Braga

Síntese e caracterização de argilas organofílicas contendo diferentes teores do surfactante catiônico brometo de hexadeciltrimetilamônio

The major applications of organoclays are in adsorption of organic polluents. The objective of this work was the synthesis and characterization of organoclays using differents amounts of cationic surfactant hexadecyltrimethylammonium bromide. The clays were characterized by low angle x-ray diffraction (XRD), scanning electron microscope (SEM), infrared with Fourier tranformation (FTIR), BET surface area, elemental analysis (CHN), Foster swell and adsorption of methylene blue. The surfactant can adsorb in differents forms in the interlamelar region changed the basal spacing. The presence of the surfactant adsorbed can be favorable or not in adsorption of the methylene blue due the different interactions dye-organoclays.

Comparison of Kinetic Study of CTMA+ Removal of Molecular Sieve Ti-MCM-41 Synthesized with Natural and Commercial Silica

This work aimed to determine and compare the apparent activation energy, involved in thermal decomposition of CTMA+ from the pores of Ti-MCM-41 synthesized by two different source of silica in order to evaluate their influence in the template removal. The molecular sieves Ti-MCM-41 were synthesized using rice husk ash (RHA), as alternative low cost source of silica, and commercial silica gel, obtaining two mesoporous material by hydrothermal synthesis of gel molar composition of: 1.0 CTMABr: 4.0 SiO2: X TiO2: 1.0 Na2O: 200.0 H2O. The samples were characterized to compare its properties by X-ray diffraction, IR spectroscopy, BET method and thermogravimetric analysis (TGA). The kinetic study using the model proposed by Flynn and Wall to determine the apparent activation energy for CTMA+ removal was performed using TGA data. The thermogravimetric analysis results of the material obtained from RHA confirmed intrinsic properties of mesoporous MCM-41 as the synthesized with commercial silica gel, such as high specific area, mesoporous range of pore diameter and hexagonal structure. According to the kinetics results the RHA showed similar chemical interaction to commercial silica gel, which makes it an interesting material, since it is a low cost source of natural silica from agricultural waste.

Adsorção de Cu 2+ e Cr 3+ em efluentes líquidos utilizando a cinza do bagaço da cana-de-açúcar

The liquid effluents of some industries have traces of harmful metals having bioaccumulative property, which contributes to the increase in their toxicity. Given the industrial growth, and the consequent increase in contaminant emissions in wastewater, the adsorption is among the operations applied to decrease the concentrations of metals in order to meet current environmental regulations. The residual biomass has been gaining attention in the treatment of these effluents by a renewable material and cost as compared with conventional adsorbents. The present work aims to evaluate the ashes of the efficiency of sugarcane bagasse (CBC) on the adsorption of metal ions Cu2+ and Cr3+, through isotherm adsorption tests. The CBC was characterized regarding its microstructure, chemical composition, specific surface area and morphology, and the adsorbate was analyzed by flame atomic absorption. The CBC has performed effectively as a bioadsorbent for both synthetic solutions containing Cu2+ and Cr3+ ions present in liquid effluents. The isotherms adsorption showed a growing profile, indicating the average removal efficiency of 97.3% to 96.4% Cr3+, and Cu2+ to, this material can be applied as an adsorbent in industrial effluents.

Nickel catalyst supported on magnesium and zinc aluminates (MgAl2O4 and ZnAl2O4) spinels for dry reforming of methane

Materiais, tais como MgAl2O4 e ZnAl2O4, avaliados em reacoes de reforma a seco de metano para produzir gas de sintese foram sintetizados pelo metodo de combustao assistida por micro-ondas usando ureia como combustivel. As amostras dos oxidos sintetizados foram calcinadas a 800 °C durante 2 h e impregnadas com 5% de niquel. As amostras impregnadas foram calcinadas a 850 °C durante 4 h para se obter as fases desejadas. Os resultados dos testes cataliticos mostraram que os catalisadores sao ativos para as reacoes de reforma a seco de metano, e o catalisador que mostrou o melhor desempenho para a capacidade de conversao de metano foi 5% de Ni/MgAl2O4 calcinado a 850 °C/4 h.

Efeito de diferentes fontes de sílica nos parâmetros texturais da peneira molecular MCM-41

Nas ultimas decadas, pesquisas estao sendo desenvolvidas para obtencao de materiais eficientes e economicamente viaveis para aplicacao em diversos setores da industria. Os materiais mesoporosos da familia MCM-41 estao entre os candidatos eficazes pela facilidade de sintese e estrutura que favorece uma gama de aplicacoes. O objetivo desse trabalho foi apresentar uma abordagem ritica das caracteristicas e propriedades dos materiais mesoporosos do tipo MCM-41, enfocando nos aspectos estruturais. Alem isso, foram discutidas as vantagens e desvantagens do uso de silica comerciais e alternativas. As fontes de silica comerciais analisadas foram silica gel e TEOS; ja as fontes de silica alternativas foram cinza da casca de arroz, quartzo e po de vidro. Os materiais analisados foram sintetizados pelo metodo hidrotermico e caracterizados por DRX, FTIR, BET e TG. Os resultados apresentados comprovam a eficiencia das fontes de silica alternativas na sintese do MCM-41, pois os materiais apresentaram propriedades texturais dentro dos padroes exigidos. Dessa forma, eles estao aptos a serem testados na industria em substituicao aos MCM-41 sintetizados com fonte de silica comercial.