Resumo O objetivo deste trabalho foi avaliar a degradação do corante rodamina B em solução aquosa por reação foto-Fenton sob irradiação visível utilizando uma bentonita rica em ferro como catalisador. O material foi tratado termicamente a baixa temperatura (200 ºC) e caracterizado por DRX, isotermas de adsorção-dessorção de N2, FTIR, MEV-EDS e FRX. A lixiviação do ferro na solução aquosa após a reação foto-Fenton foi avaliada por espectroscopia de absorção atômica. O material exibiu uma estrutura mesoporosa, apresentando uma área de superfície específica de 99 m2.g-1. Os resultados catalíticos mostraram alta eficiência na degradação do corante, atingindo 95% de descoloração e 72% de mineralização em 300 min de reação. O catalisador apresentou alta estabilidade química em quatro ciclos de reação. Portanto, esta bentonita rica em Fe tratada termicamente pode ser considerada como um promissor catalisador na reação foto-Fenton heterogênea para a degradação da rodamina B em solução aquosa.

Abstract The objective of this work was to evaluate the degradation of rhodamine B dye from aqueous solution by photo-Fenton reaction under visible irradiation using a Fe-rich bentonite as a catalyst. The material was thermally treated at a low temperature (200 °C) and characterized by XRD, N2 adsorption-desorption isotherms, FTIR, SEM-EDS and XRF. Iron leaching in aqueous solution after the photo-Fenton reaction was evaluated by atomic absorption spectroscopy. The material exhibited a mesoporous structure, containing a specific surface area of 99 m2.g-1. The catalytic results showed significant dye degradation, reaching 95% of decolorization and 72% of mineralization at 300 min of reaction. The catalyst showed high chemical stability in four reaction cycles. Therefore, this thermally treated Fe-rich bentonite can be considered as a promising catalyst in the heterogeneous photo-Fenton reaction for the degradation of rhodamine B from aqueous solution.

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.

Resumo Aluminato de níquel (NiAl2O4) foi preparado utilizando quitosana como precursor polimérico e uma solução amoniacal como um agente de precipitação. Além disso, sais de nitrato de níquel e de nitrato alumínio foram empregados como fontes de Ni e Al, em quantidades estequiométricas (razão molar Ni:Al = 1:2). Partículas de NiAl2O4 foram preparadas em diferentes temperaturas de calcinação e as suas propriedades foram investigadas. Os sólidos sintetizados foram caracterizados por difração de raios X, espectroscopia de infravermelho, microscopia de força atômica, análise termogravimétrica e isotermas de adsorção-dessorção de nitrogênio. Os resultados mostraram que o processo de tratamento térmico influencia fortemente sobre formação da fase espinélio NiAl2O4. Partículas de aluminato de níquel, com uma estrutura porosa e com alta área superficial, foram obtidas em temperaturas superiores a 700 °C.

Abstract Nickel aluminate oxide (NiAl2O4) was prepared using chitosan as polymeric precursor and ammonia solution as a precipitating agent. In addition, nickel nitrate and aluminum nitrate salts were used as sources of Ni and Al, under stoichiometric amounts (molar ratio Ni:Al = 1:2). NiAl2O4 particles were prepared at different calcination temperatures and their properties were investigated. The synthesized materials were characterized by X-ray diffraction, infrared spectroscopy, atomic force microscopy, thermogravimetric analysis and nitrogen adsorption-desorption isotherms. The results showed that the thermal treatment process strongly influence on the formation of a single-phase structure of NiAl2O4 spinel. Nickel aluminate spinel with a porous structure and high surface area was obtained at temperatures above 700 ºC.

En este trabajo se investigó la hidrólisis enzimática de salvado de arroz por ultrasonido para obtener glucosa. Se evaluaron variables del proceso tales como la temperatura, la concentración de enzima y la humedad para la hidrólisis enzimática con y sin la aplicación de la irradiación ultrasónica. La enzima utilizada fue una mezcla de amilasa de Trichoderma reesei. Se evaluó la cinética de la hidrólisis enzimática de salvado de arroz en el período constante de la velocidad de reacción. Los mejores resultados para la hidrólisis enzimática con la aplicación de ultrasonidos fueran utilizando 3% de enzima, 60 ° C y 65% de humedad, el rendimiento obtenido fue 0,38 g de azúcar / g de salvado de arroz, mientras que el más alto rendimiento de la hidrólisis en ausencia de ultrasonido fue 0,20 g de azúcar / g de salvado de arroz utilizando 3 % de enzima, 60 ° C y 50 % de humedad. El uso de ultrasonido mejora la hidrólisis enzimática permitiendo obtener 74 % más azúcares fermentables que en la ausencia de ultrasonidos, lo que demuestra que el uso de ultrasonido es una promisora tecnología que se puede utilizar en las reacciones enzimáticas y como una alternativa de intensificación de procesos.

In this work ultrasound-assisted solid-state enzymatic hydrolysis of rice bran to obtain fermentable sugars was investigated. For this purpose, process variables such as temperature, enzyme concentration and moisture content were evaluated during the enzymatic hydrolysis with and without ultrasound irradiation. The enzyme used is a blend of amylases derived from genetically modified strains of Trichoderma reesei. Kinetic of the enzymatic hydrolysis of rice bran at the constant-reaction rate period were measured. The best results for the ultrasound-assisted enzymatic hydrolysis was obtained using 3 wt % of enzyme, 60 ºC and moisture content of 65 wt %, yielding 0.38 g sugar/g rice bran, whereas for the hydrolysis in the absence of ultrasound the highest yield was 0.20 g sugar/g rice bran using 3 wt % of enzyme, 60 ºC and moisture content of 50 wt % . The use of ultrasound-assisted enzymatic hydrolysis of rice bran was intensified, obtaining around 74 % more fermentable sugar than in the absence, showing that the use of ultrasound is a promising technology to be used in enzymatic reaction as an alternative of process intensification.

La destilación diferencial aplicada a la producción de etanol hidratado combustible (EHC) a pequeña escala todavía requiere condiciones de operación que aseguren la calidad del producto destilado y la productividad óptimas. El objetivo de esta investigación es validar estadísticamente la destilación diferencial mediante el empleo de la metodología de superficie de respuesta (MSR). Parámetros operacionales y de productividad se han formulado con el objetivo de garantizar el cumplimiento de la calidad de los requisitos legales para la concentración del producto destilado, además de proporcionar información de apoyo para el control de la producción de EHC a pequeña escala. El control de las temperaturas del rehervidor y deflegmador, mantenidos dentro del intervalo de 97,5 a 99,5 °C y de 60 a 70°C, respectivamente, en combinación con una relación de reflujo variable fueron satisfactorios en la obtención de una concentración del producto destilado en conformidad con las normas legales, así como una alta productividad. Los resultados de este estudio pueden contribuir al montaje de un sistema de control de destilación diferencial simplificado y de bajo costo.

Batch distillation applied to hydrous ethanol fuel (HEF) production on a small scale still requires operating conditions that ensure optimal top product quality and productivity. The aim of this study is to statistically validate a batch still through the employment of response surface methodology (RSM). Operational and productivity parameters were formulated in order to guarantee quality compliance with the legal requirements for the top product concentration, besides providing support information to control the production of HEF on a small scale. The reboiler control and dephlegmator temperatures maintained within the range of 97.5 to 99.5°C and 60 to 70°C, respectively, combined with a variable reflux ratio, was satisfactory in obtaining a top product concentration, in accordance with legal regulations, as well as high productivity. The results of this study may contribute to the assembly of a simple and low-cost batch distillation control system.

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

En este trabajo se investigó la aplicabilidad de la ecuación de estado cúbica, de Van der Waals, con translación en volumen (vdWt). Para la regla de mezcla, se aplicó el método de Huron-Vidal modificado (MHV2), con el modelo UNIFAC (UNIQUAC funcional coeficiente de actividad) para describir datos del equilibrio de fases y la densidad para una serie de sistemas complejos; en amplias gamas de temperatura (T) y presión (P). Se encontraron algunas limitaciones en la predicción de los datos experimentales recogidos, por ejemplo, en los sistemas con componentes altamente asociativos, la ecuación vdWt+MHV demostró capacidad para representar de manera satisfactoria, tanto el equilibrio de fases como el comportamiento volumétrico.

This work investigated the applicability of the van der Waals cubic equation of state (EoS) with volume translation (vdWt), using the modified Huron-Vidal (MHV2) mixing rule with the UNIFAC (UNIQUAC Functional Activity Coefficients) model for describing phase equilibrium and density data for a series of complex systems over wide ranges of temperature (T) and pressure (P). Some limitations were identified in the prediction of the experimental data collected, e.g., systems with highly associating components, but in general, the EoS vdWt+MHV was able to satisfactorily represent both phase equilibrium and volumetric behavior.

Este trabalho teve por objetivo avaliar a impregnação de diferentes catalisadores na superfície de um material cerâmico de alumina. Para a confecção do material cerâmico, foi utilizada a rota de processamento de espumas cerâmicas pelo método da réplica, no qual uma esponja de poliuretano com porosidade de 60 ppi foi mergulhada em uma suspensão de alumina a fim de produzir uma cerâmica com a mesma morfologia que o material precursor. Inicialmente foram obtidas espumas cerâmicas de alumina com resistência mecânica média de 0,7 MPa e porosidade aparente de 80%.Três diferentes catalisadores (ZnAl2O4,ZnFe2O4 e Zn2SnO4) foram impregnados sobre esse suporte por meio do método dip coating.Os resultados mostraram que os catalisadores foram imobilizados sobre o suporte em baixas concentrações.

This study aimed to evaluate the immobilization of different catalysts on the surface of ceramic alumina foam. The ceramic material was produced by the replica method, where a polyurethane sponge with a porosity of 60 ppi was poured into a slurry containing alumina to produce a ceramic support with the same morphology of the precursor material. Alumina ceramic foams with an average strength of 0.7MPa and apparent porosity of 80% were obtained. Three different catalysts (ZnAl2O4,ZnFe2O4 and Zn2SnO4) were impregnated on this support by the dip coating method. The results showed that the catalysts were immobilized on the substrate at low concentrations.

A ZnO film was electrodeposited onto a gold substrate obtained from a recordable compact disc and tested as photocatalyst in degradation of dye in aqueous solution. X-ray diffractometry and atomic force microscopic analysis showed a pure ZnO phase with particle sizes in the nanometric scale. The results showed that the photocatalytic activity of the film is significant, with more than 90 % degradation of the dye in under 6 h sunlight irradiation. The photocatalytic process in sunlight follows first-order kinetics.

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.

Spent bleaching clay from the oil refining industry was subjected to heat regeneration in a box furnace with air. The heat reactivation was conducted without previous extraction of residual oil and with previous extraction of oil using organic solvent. The experimental temperature ranged from 723 at 873 K. A model for the kinetic of thermal reactivation of spent adsorbent has been proposed. The activation energy involved on the desorption phenomenon was determined.

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.

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).