RESUMO Neste trabalho, compósito Fe2O3/grafite foi preparado e usado como um catalisador em reação foto-Fenton para a descoloração de solução aquosa contendo o corante amaranto sob irradiação de luz visível. Amostras com diferentes teores de Fe2O3 suportados sobre grafite foram preparadas e caracterizadas por difração de raios-X (DRX), adsorção-dessorção de N2 e microscopia eletrônica de varredura (MEV). O aumento do teor de ferro nos compósitos resultou em uma superior área de superfície específica. Através da metodologia de superfície de respostas gerada a partir do Delineamento Composto Central Rotacional (DCCR), verificou-se uma eficiência máxima de descoloração da solução de corante de 93% nas condições experimentais ótimas de reação foto-Fenton (pH = 2,5, quantidade de catalisador = 0,35 g L-1 e razão molar H2O2/Ʃ elementos mineralizáveis: 4,7). Portanto, o compósito Fe2O3/grafite pode ser utilizado como um potencial catalisador foto-Fenton para a degradação do corante amaranto em efluentes líquidos.

ABSTRACT In this work, Fe2O3/graphite composite was prepared and used as a catalyst in photo-Fenton reaction for the decolorization of amaranth dye from aqueous solution under visible light irradiation. Samples with different Fe2O3 contents supported on graphite were prepared and characterized by X-ray diffraction (XRD), N2 adsorption-desorption and scanning electron microscopy (SEM). The increase of the iron content in the composites resulted in a superior specific surface area. The response surface methodology generated from the Rotational Central Composite Design (RCCD) showed a maximum efficiency in the decolorization of the dye solution of 93% under the optimal experimental conditions of photo-Fenton reaction (pH = 2.5, amount of catalyst = 0.35 g L-1 and molar ratio H2O2/Ʃ mineralizable compounds: 4.7). Therefore, the Fe2O3/graphite composite can be used as a potential photo-Fenton catalyst for the degradation of amaranth dye from liquid effluents.

RESUMO Neste trabalho, ferrita de cobalto (CoFe2O4) foi sintetizada sobre aluminato de magnésio (MgAl2O4) e zeólita ZSM-5 e a atividade catalítica desses materiais na reação foto-Fenton visando a decomposição de um poluente orgânico em solução aquosa foi avaliada. Ferrita de cobalto foi sintetizada sobre os suportes pela rota solvotérmica. Os materiais magnéticos foram caracterizados por difração de raios-X, isotermas de adsorção/dessorção de nitrogênio, microscopia eletrônica de varredura e espectroscopia de energia dispersiva de raios-X. Os catalisadores foram avaliados na degradação de corante amaranto sob irradiações visível artificial e solar. Os sistemas produzidos CoFe2O4/MgAl2O4 e CoFe2O4/ZSM-5 apresentaram satisfatórias atividades catalíticas, sendo superior comparado a ferrita de cobalto pura. As atividades catalíticas para ambos os sistemas foram superiores quando do uso de irradiação solar, atingindo 95 % de descoloração e 80 % de mineralização em 30 e 240 min de reação, respectivamente. Portanto, MgAl2O4 e ZSM-5 como suportes para a ferrita de cobalto apresentam-se como materiais promissores para a degradação de poluentes orgânicos em soluções aquosas através da reação foto-Fenton heterogênea.

ABSTRACT In this work, cobalt ferrite (CoFe2O4) was synthesized on magnesium aluminate (MgAl2O4) and ZSM-5 zeolite and the catalytic activity of these materials in the photo-Fenton reaction for the decomposition of an organic pollutant in aqueous solution was evaluated. Cobalt ferrite was synthesized on the supports by the solvothermal route. The magnetic materials were characterized by X-ray diffraction, adsorption/desorption isotherms of nitrogen, scanning electron microscopy and X-ray dispersive energy spectroscopy. The catalysts were evaluated for the degradation of amaranth dye under artificial visible and solar irradiations. The produced materials CoFe2O4/MgAl2O4 and CoFe2O4/ZSM-5 presented satisfactory catalytic activities, being superior compared to pure cobalt ferrite. Both the systems showed higher catalytic activity when solar irradiation was used, reaching 95% of decoloration and 80% of mineralization at 30 and 240 min of reaction, respectively. Therefore, MgAl2O4 and ZSM-5 as supports for the cobalt ferrite are promising materials aiming the degradation of organic pollutants in aqueous solutions through the heterogeneous photo-Fenton reaction.

In this work, cobalt ferrite (CoFe2O4) was synthesized by solvothermal route for application as a catalyst in the ozonation reaction for the decolorization and mineralization of melanoidin from aqueous solution. The structural properties of CoFe2O4 sample were investigated by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, Fourier-transform infrared spectroscopy (FTIR), particle-size distribution, scanning electron microscopy (SEM) and X-ray dispersive energy spectroscopy (EDS). Single-phase CoFe2O4 particles with a predominantly mesoporous structure containing a high specific surface area were obtained. Results showed that the CoFe2O4-catalyzed ozonation reaction has higher activity for the decolorization and mineralization of melanoidin when compared with the ozonation reaction without the presence of catalyst. Therefore, this material can be very promising for the application in catalytic ozonation systems for the melanoidin removal from liquid effluents.

This study investigated the potential of Brazilian kaolin as a low-cost adsorbent for the removal of Malachite Green (MG) from colored effluents. The morphology, chemical structure and surface properties of the adsorbent were investigated by characterization techniques such as X-ray diffraction, N2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy, X-ray fluorescence spectrometry, scanning electron microscopy, thermogravimetric analysis and particle size distribution. A possible technological application of raw kaolin is the MG removal from aqueous media, which was investigated using batch adsorption experiments. The adsorption kinetics was studied using the pseudo-first order, pseudo-second order and Elovich models. The adsorption isotherms were studied using the Langmuir, Freundlich and Sips models. The Elovich model was the more adequate to represent the adsorption kinetic, while the equilibrium was well represented by the Langmuir model. The maximum adsorption capacity, at pH of 6.3 and temperature of 25ºC, was 128 mg g-1, and this satisfactory result may be associated with some adsorbent properties. Therefore, the results revealed that raw kaolin can be utilized as a promising low-cost adsorbent to remove MG from colored effluents.

Nickel ferrite/multi-walled carbon nanotubes (NiFe2O4/MWCNTs) composite has been rapidly synthesized via microwave irradiation technique. The structural properties of the product was investigated by X-ray diffraction (XRD), N2 adsorption/desorption isotherms, thermogravimetric analysis (TGA), Raman spectroscopy and, scanning electron microscopy (SEM). Catalytic behavior of the composite material on the advanced photo-Fenton degradation of Amaranth dye was evaluated. The synthesis conditions employed on the microwave system were: temperature (235 °C), power (500 W), pressure (600 psi) and irradiation time (30 min). Characterization results showed the formation of hybrid material, containing a predominantly microporous structure, with surface area and total pore volume of 54 m2 g-1 and 0.2249 cm3 g-1, respectively. The composite exhibited higher catalytic activity compared to the pure NiFe2O4, reaching 100% of decolorization at 60 min of reaction, which can be attributed to a synergism between NiFe2O4 and MWCNTs. Therefore, NiFe2O4/MWCNTs composite can be used as a promising photo-Fenton catalyst to degrade Amaranth dye from aqueous solutions.

Mesoporous Fe2O3-supported ZSM-5 zeolites were prepared by carbon-templating and subsequently evaluated as photo-Fenton catalysts to degrade a dye used as a model heavy organic pollutant. The synthesis procedure of the mesoporous ZSM-5 zeolites was performed employing a nucleating gel and carbon particles as mesopores template. Thereafter, the precursor salt of the iron oxide (Fe2O3) was impregnated and then calcined to obtain the final catalyst. For comparison purposes, a conventional Fe2O3-supported ZSM-5 zeolite was also prepared. The results showed that the amount of intracrystalline mesopores formed in the ZSM-5 crystals was influenced by the amount of carbon added into the synthesis mixture. In comparison to the conventional prepared catalyst, the mesoporous Fe2O3/ZSM-5 ones showed an improved performance in the degradation of the target organic pollutant by the photo-Fenton reaction, which was attributed to the improvement of their textural properties as consequence of the mesopores generation.

ZnWO4 particles were synthesized as a single-phase by a simple and easy solvo-hydrothermal technique using water-ethylene glycol mixture as solvent, without using surfactant. Physical properties of produced particles were analyzed by X-ray diffraction (XRD), infrared spectroscopy (FTIR), surface area (BET), particles size distribution and atomic force microscopy (AFM). This material was used as support for inulinase immobilization by physical adsorption and the influence of temperature (30 and 50 ºC) was evaluated. Material with mesoporous characteristic and with a surface area of 35.5 m2.g-1 was obtained. According to the findings, ZnWO4 present a satisfactory inulinase adsorption, and the better result was 605 U.g-1 support at 30 ºC. Therefore, ZnWO4 particles prepared by one-step solvo/hydrothermal route provide a new potential support for inulinase immobilization.

Este estudio evaluó experimentalmente el comportamiento de una columna de destilación de etanol/agua a pequeña escala. Se realizó análisis estadístico utilizando el software Statistica® 7,0, considerando un nivel de significación del 90% (p < 0,10), para evaluar si las variables independientes (concentración de etanol y caudal de alimentación) influencian la producción de etanol de acuerdo con la legislación brasileña, i.e., etanol combustible con concentración de etanol entre 92,5 y 93,8 % en masa. Los resultados demostraron que la influencia de la concentración de etanol y el caudal de alimentación fueron significativos para la concentración del producto destilado y la tasa de recuperación. La tasa de recuperación de etanol fue mayor que 80%, lo que señala que el rendimiento de la columna a pequeña escala fue satisfactorio.

This research assessed experimentally the performance of a small-scale ethanol/water distillation column. Statistical analysis was performed using Statistica® 7.0, considering a significance level of 90% (p < 0.10), to evaluate if the independent variables (feed stream ethanol concentration and flow rate) influence on the production of ethanol in accordance with the Brazilian legislation, i.e., a Hydrous Ethanol Fuel with ethanol content between 92.5 and 93.8 wt%. The results demonstrated that the influence of the feed stream ethanol concentration and flow rate were significant for both the top product concentration and the recovery ratio. The recovery ratio of ethanol was above 80%, demonstrating that the performance of the small-scale column is satisfactory.

AbstractCopper and cobalt aluminates were obtained through the use of chitosan as template. In this synthesis route, chitosan is eliminated by heating, and a porous material is produced. These oxides were used as supports for inulinase immobilization by adsorption process. Physical properties of produced particles were analyzed by X-ray diffraction (XRD) and nitrogen adsorption-desorption isotherms. Both oxides presented particles containing mesoporous characteristics and high surface area, which is desirable for applications in enzyme immobilization processes. The results revealed that the copper and cobalt aluminates exhibit high inulinase immobilization efficiencies, which makes them promising supports for enzyme immobilization.

Este estudio investigó la influencia de NaCl sobre el punto de niebla de los tensioactivos polietoxilados de la familia de polietoxilatos de alcohol laurílico y polietoxilatos de nonilfenol. Se representaron gráficamente las curvas de equilibrio líquido-líquido de los sistemas acuosos con tensioactivos anteriormente mencionados con presencia de NaCl, surgiendo los parámetros termodinámicos basados en el modelo de Flory-Huggins. El uso del método visual determinó el punto de niebla. Se prepararon soluciones con concentraciones de surfactante entre 0,5 y 20% (por peso) y NaCl entre 4,9 y 12,1% (por peso). La sal tenía un efecto salino, disminuyendo la solubilidad surfactante en agua. Además, el punto de niebla disminuyó al aumentar la concentración de NaCl. El modelo de Flory-Huggins describió satisfactoriamente los datos experimentales para todas las misturas acuosas de surfactante + NaCl estudiadas.

In this study, the influence of NaCl on the cloud point of polyethoxylate surfactants from the family of lauryl alcohol polyethoxylates (C12EOn) and nonylphenol polyethoxylates (NPEOn) was investigated. Liquid-liquid equilibrium curves of the aforementioned aqueous surfactant systems with the presence of NaCl were plotted and thermodynamic parameters based on the Flory-Huggins model were obtained. The visual method was used to determine the cloud point. Solutions containing surfactant concentrations between 0.5 and 20% (by weight) and NaCl between 4.9 and 12.1% (by weight) were prepared. Salt had a salting-out effect, decreasing surfactant solubility in water. Furthermore, the cloud point decreased with an increase of NaCl concentration. The Flory-Huggins model satisfactorily described the experimental data for all surfactant + NaCl aqueous mixtures studied.

ZnAl2O4 spinel was synthesized by co-precipitation using ammonia as precipitating agent, followed by thermal treatment at 750 ºC. The structural properties of particles were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), differential thermal analysis (DTA), and N2 adsorption/desorption isotherms (BET) techniques. The photocatalytic activity was evaluated in the degradation of organic pollutant in aqueous solution under sunlight. The results showed that the ZnAl2O4 particles exhibited a mesoporous structure, and a promising photocatalytic activity for the degradation of pollutant molecules.

Radiação micro-ondas em sistema fechado foi utilizada para a remoção de sedimentos de emulsão de petróleo para a posterior caracterização em laboratório. O programa de aquecimento do forno de micro-ondas foi otimizado através da avaliação do tempo de aquecimento (5 a 30 s) e da potência de micro-ondas (300 a 1400 W). O teor de sedimentos foi determinado usando um procedimento de filtração com membrana conforme recomendado pela norma ASTM D 4807-05, antes e após a remoção de sedimentos. Os teores de água e cloreto foram determinados no óleo obtido após a remoção de sedimentos. Até oito amostras de 20 g puderam ser processadas simultaneamente. A eficiência de remoção de sedimentos foi superior a 95%. Foi possível a obtenção de petróleo virtualmente isento de água, sal e sedimentos, permitindo a determinação de parâmetros como gravidade API, densidade, viscosidade e número de acidez total sem interferências causadas por sedimentos ou mesmo sal e água.

Microwave radiation in closed vessels was applied for removal of sediments from crude oil allowing the subsequent crude oil characterization in laboratory. Heating time and microwave power were evaluated in the range of 5 to 30 s and 300 to 1400 W, respectively. Sediment content was determined using the method recommended by ASTM D 4807-05 based on a filtration step in a membrane before and after sediment removal. Water and chloride contents were determined in the oil phase obtained after sediment removal. Up to eight samples of 20 g of crude oil could be simultaneously processed. Sediment removal efficiency was better than 95%. It was possible to obtain crude oil in a suitable condition for determination of routine parameters as API gravity, density, viscosity and total acid number without interferences caused by sediments or even water and salt.

In this work was investigated the influence of pH on the synthesis of struvite using cola beverage waste as source of phosphorus. The process was operated in a batch reactor. The reaction time was 20 minutes, and the chemicals MgCl2.6H2O and NH4Cl were used in the experiment, with a molar ratio of Mg+2:NH4+:PO4(3-) = 1:1:1. The products were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), surface area (BET), thermogravimetric analysis (TGA) and infra-red (IR). From the results was verified the formation of a crystalline phase at pH 9.5, with a surface area of 6.59 m² g-1 and a particle size of about 0.25 µm.

Sodium silicate is used as raw material for several purposes: silica gel production, preparation of catalysts, inks, load for medicines, concrete hardening accelerator, component of detergents and soaps, refractory constituent and deflocculant in clay slurries. In this work sodium silicate was produced by reacting rice hull ash (RHA) and aqueous sodium hydroxide, in open and closed reaction systems. The studied process variables were time, temperature of reaction and composition of the reaction mixture (expressed in terms of molar ratios NaOH/SiO2 and H2O/SiO2). About 90% silica conversion contained in the RHA into sodium silicate was achieved in closed system at 200 °C. The results showed that sodium silicate production from RHA can generate aggregate value to this residue.

Currently, the accumulation of rice husk is a serious environmental problem. The burning of rice husk generates a considerable volume of ash, that falls to the ground and gets into the air and the rivers, causing a disequilibrium in the ecosystem. This motived research into solutions that aim to exploit the husks for energy generation and the ashes for developing diverse technological products. This work presents the possibilities of using rice husks and their ashes after burning.