Resumo Neste trabalho, zeólita ZSM-5 mesoestruturada foi preparada usando quitina como um novo auxiliar de síntese para produzir mesoporosidade. Foram utilizadas diferentes quantidades de quitina para a síntese de ZSM-5, a fim de verificar a sua influência na formação de mesoporos. Todas as amostras foram preparadas por processo hidrotérmico convencional. Para fins de comparação, a zeólita ZSM-5 também foi sintetizada sem a presença de quitina. As amostras foram caracterizadas por difração de raios X, microscopia eletrônica de varredura e isotermas de adsorção-dessorção de N2. Os resultados experimentais mostraram que o volume de mesoporos das amostras obtidas aumentou com a quantidade crescente de quitina na mistura reacional. Portanto, a quitina mostrou ser um auxiliar de síntese promissor para a obtenção da ZSM-5 com propriedade mesoporosa.

Abstract In this work, mesostructured ZSM-5 zeolite was prepared using chitin as a new template to produce mesoporosity. Different amounts of chitin were used for the synthesis of ZSM-5 in order to verify its influence on the formation of mesopores. All samples were prepared by conventional hydrothermal process. For comparison purposes, ZSM-5 zeolite has also been synthesized without a presence of chitin. The samples were characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption techniques. Experimental results showed that the mesopores volume of the obtained samples increased with increasing amount of chitin in the reaction mixture. Therefore, chitin showed to be a promising template for obtaining the ZSM-5 with mesoporous property.

Resumo Este trabalho objetivou a preparação da zeólita ZSM-5 suportada com nanopartículas de óxido de ferro para uso como catalisador na degradação de um poluente orgânico em solução aquosa a partir do processo foto-Fenton. A zeólita foi preparada usando gel nucleante como indutor de formação da estrutura tipo MFI. Nanopartículas de óxido de ferro foram suportadas sobre a zeólita através da técnica de impregnação incipiente. Além disso, nanopartículas de óxido de ferro foram preparadas para fins de comparação entre as atividades catalíticas na reação foto-Fenton. Os materiais produzidos foram caracterizados por difração de raios X, microscopia eletrônica de varredura e análise de adsorção/dessorção de nitrogênio. Os resultados revelaram a formação do sistema Fe2O3/ZSM-5 com propriedades intrínsecas que resultaram em satisfatória atividade catalítica, sendo superior ao óxido de ferro. Além disso, esse sistema apresentou excelente atividade e estabilidade após três ciclos de reuso. O material Fe2O3/ZSM-5 produzido neste trabalho apresenta-se como um catalisador promissor para uso na reação foto-Fenton para a degradação de poluentes orgânicos em soluções aquosas.

Abstract The aim of this work was to prepare ZSM-5 zeolite-supported iron oxide nanoparticles for use as a catalyst in the degradation of an organic pollutant in aqueous solution through the photo-Fenton process. ZSM-5 zeolite was prepared using nucleation gel to induce the formation of MFI-type structure. Iron oxide nanoparticles were supported on the zeolite by incipient wetness impregnation technique. Moreover, iron oxide nanoparticles were prepared for comparison purposes of the catalytic activities in photo-Fenton reaction. The produced materials were characterized by X-ray diffraction, scanning electron microscopy, and analysis of nitrogen adsorption-desorption isotherms. The results revealed the formation of Fe2O3/ZSM-5 system containing intrinsic properties that resulted in a satisfactory catalytic activity, higher than the iron oxide. In addition, the system presented excellent activity and stability after three reuse cycles. The Fe2O3/ZSM-5 system prepared in this work is a promising catalyst for use in photo-Fenton reaction for the degradation of organic pollutants in aqueous solutions.

In this work, ZnAl2O4 spinel was used as photocatalyst for dye degradation in aqueous solutions under UV irradiation. This material was prepared by a route with chitosan as template. The effects of process variables, such as, initial dye concentration and photocatalyst concentration were investigated. Kinetic parameters were obtained and the reaction order was determined. The results revealed that both studied variables presented strong influence on the dye degradation efficiency, which attained 100% in some cases. It was found that the dye photocatalytic degradation under UV irradiation followed a first order kinetic behavior. The results indicated that ZnAl2O4 spinel can be used to treat dye containing effluents

The present study describes the adsorption of textile dye on rice hull. The adsorption parameters were obtained from Langmuir and Freundlich isotherms utilizing linear regression plots to fit the data. The results showed that Langmuir equation was more suitable than the Freundlich one to predict the experimental adsorption isotherms, indicating that the adsorption of dye molecules is localized in a monolayer on the surface of the adsorbent. Thermodynamic parameters such as ΔHa, ΔSa and ΔGa were determined in this work. The heat evolved during adsorption is endothermic. The maximum sorption capacity of rice husk was satisfactory when compared to capacities of other low-cost adsorbent materials.

This work investigates the influence of reaction time (ranging from 12 to 96 h) on the characteristics of zinc stannate (Zn2SnO4) nanoparticles obtained by the hydrothermal method at 200°C. The nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area measurements (BET) and infrared spectroscopy (IR). The results showed that the reaction time influenced the properties of Zn2SnO4 nanoparticles. The product presented a pure crystalline phase with mean particle size about 20 nm and BET surface area ranging from 34 to 43 m².g-1.

The aim of the present work was to verify the influence of the type of metal used in the presence of niobium pentoxide on the photocatalytic degradation of an industrial leather dye. Niobium oxide alone showed low photocatalytic activity, but with the impregnation of small quantities of metal, this material showed highly activity. It was observed that the type of metal significantly influenced the catalytic activity of niobium oxide. The results indicate that metal/Nb2O5 could be employed for the removal of dyes from wastewater. The order of photocatalytic activity of metal-doped Nb2O5 was as follows: (La, Zn, Ti) > (Sr, Sn, Ag) > (Co, V, Ga) > (Ni, Y, Cu). The metals Ce, Mn and Mo showed not efficient catalytic activity in degrading the leather dye

TiO2 powder was prepared by a hydrothermal process at 200°C for 12 h. The material was characterized by X-ray diffraction and N2 adsorption-desorption isotherm. The synthesized sample presented a pure phase anatase, with nanometric particle size. Its activity was tested for adsorption and degradation of the azo leather dye, Direct Black 38. The adsorption isotherm obtained followed the S-type in terms of the classification of Giles. Thermodynamic parameters were calculated, and the results revealed that the adsorption process is endothermic in nature. The material showed highly photocatalytic activity in the degradation of the dye, similar to that of the TiO2 (P25 Degussa) photocatalyst.

An investigation was carried out on the synthesis of titanium dioxide nanopowders via the hydrothermal method, examining the influence of temperature (150ºC and 200ºC) and reaction time (6 to 36 h). The resulting powders were characterized by X-ray diffraction, infrared absorption spectrophotometry, transmission electron micrographs and surface area. The X-ray diffraction revealed that there was formation of a pure crystalline phase, consisting only of anatase for all conditions of synthesis. Both temperature and reaction time proved to have a slight influence on the crystallite size (from 9 to 17 nm) and a significant influence on the surface area (from 86 to 168 m².g-1).

Pd-Ag alloy membranes (with different silver contents) have been prepared by electroless plating technique for hydrogen separation. The surface morphology and phase structures of the composite membranes were investigated using a scanning electron microscope and a X-ray diffractometer, respectively. Hydrogen permeation experiments through the membranes synthesized at different hydrogen pressures (50 - 250 kPa) and temperatures (623 - 823 K) are reported. The experimental results reveal that the membranes showed a considerable enhancement in the hydrogen permeation and that the contribution of surface process for permeation was significant at high temperatures.

O espinélio aluminato de magnésio MgAl2O4 é um material que apresenta uma combinação de propriedades de grande interesse tecnológico, tais como alto ponto de fusão (2135 ºC), alta resistência ao ataque químico e ao choque térmico, baixa constante dielétrica, boas propriedades ópticas e catalíticas. Neste trabalho, sintetizou-se o espinélio MgAl2O4 por meio da hidrólise de alcóxidos metálicos de Mg e Al. O precursor formado foi calcinado em temperaturas entre 600 ºC e 1100 ºC, por 4 h. Da análise por difração de raios X observou-se a formação da fase espinélio em temperaturas acima de 700 ºC, e através das análises de microscopia eletrônica de varredura observou-se que as partículas de MgAl2O4 apresentam tamanho muito pequeno.

The spinel MgAl2O4 has a specific combination of desirable properties such as: high melting point (2135 ºC), high resistance to chemical attack, good mechanical resistance at room temperature and high temperatures, low dielectric constant, excellent optical properties and good catalytic properties. In this work, the spinel MgAl2O4 was synthesized through hydrolysis of metallic alkoxides of Mg and Al. The formed spinel precursor phase was calcined at temperatures between 600 and 1100 ºC for 4 h. It was observed through X-ray diffraction the formation of the spinel phase at temperatures above 700 ºC, and through microscopy (SEM) it was observed that MgAl2O4 particles present very small size.