Abstract: Conventional processes for heavy metal removal are costly. Natural and modified clay with quaternary ammonium salt were used as adsorbent for the removal of Cr (VI) from aqueous solutions. Clays were characterized using Fourier transform infrared spectroscopy FTIR, thermal analysis (TG/DTA) and X-ray diffraction (XRD). Cr (VI) determination was conducted by ultraviolet-visible spectrophotometry, using complexation with 1,5-diphenylcarbazide. Absorbance was measured at the wavelength of 540 nm. The experiments were conducted at 25 ± 1 °C; initial Cr (VI) concentration of 4 to 25 mg L-1; initial pH of 2, agitation of 150 rpm; contact time of 120 minutes and clay mass of 0.1 g. Natural and modified clays exhibited a maximum adsorption capacity of 2.548 mg g-1 and 17.24 mg g-1, respectively, in accordance with the Langmuir isotherm model. X-ray diffraction analysis of clay indicated that the sample consists mainly of kaolinite and montmorillonite.
Abstract: In this work were synthesized new catalysts of stoichiometries Sr0.8K0.2TiCu0.10O3, Sr0.7K0.3TiCu0.15O3 and Sr0.5K0.5TiCu0.25O3 by spray pyrolysis method. The synthesis conditions were optimized to obtain single phase powder of titanates of double perovskite structure, with an ultrasound vibration frequency of 1.3 MHz at 700 °C under air flow. The average crystallite size of the powders, determined by the Scherrer equation and using the Jade Plus 8 software, was at around 9 nm. The powder morphology was analyzed by scanning electron microscopy (SEM). The Sr0.5K0.5TiCu0.25O3 system showed particles with smooth surfaces, spherical and with smaller agglomerates than Sr0.8K0.2TiCu0.10O3, Sr0.7K0.3TiCu0.15O3 systems. This phenomenon suggests that the stoichiometry changes the aspect of the particle surface, which may influence in the catalytic activity. Thus, particles without roughening and smaller size can act as promising catalysts.
Abstract: This study was prepared by the secondary growth method the zeolite membrane Y and evaluate its use in the emulsion removal of oil / water. The prepared materials: zeolite Y, zeolite membrane alpha-alumina ceramic membrane and Y were characterized by the techniques of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). powder pressing method for compression of alpha-alumina ceramic membrane and the secondary growth method for the preparation of zeolitic membranes Y/alpha-alumina was used. Through XRD analysis, it was observed that the method was effective in the synthesis of zeolite membrane. By spectrophotometric analysis it was possible to observe a significant reduction in oil concentration in the permeate for the Y zeolite membrane / alpha-alumina, thus showing that they have the potential for this application.
Abstract: Ceramic pyrochlores, the basis of Bi2O3-ZnO-Nb2O5 (BZN), have dielectric properties of great interest, such a high dielectric constant (ε), a low dielectric loss tangent (tan δ) and a low coefficient of capacitance with temperature (TCC). The system has two main phases, Bi1,5ZnNb1,5O7 (α) and Bi2Zn0,67Nb1,33O7 (β) with cubic and orthorhombic crystal structures, and very different dielectric properties. The purpose of this article was to synthesize chemically homogeneous ceramic pyrochlores BZN-α and BZN-β, using the ceramic method in obtaining nanopowders and their characterizations by scanning electron microscopy (SEM), X-Ray Diffraction (XRD), and the Rietveld refinement method of the structures. The powders were weighed in stoichiometric proportions and calcined at 700 °C/2h, they were sintered at 900, 950 and 1000 °C/2h. A pure BZN-α phase was obtained, while the BZN-β has remained in phases as Bi5Nb3O15 and BiNbO4.
Abstract: This study is aimed to verify the influence of adding SiO2 and CaO in the sintering temperature of hexaferrite, obtained by standard ceramic methods. The powders were weighed in stoichiometric amounts, milled for 1 hour under a high energy mill and calcined at 1000 °C/24h. To study the effect of concentration of additives on the microstructure of the hexaferrite samples were prepared without additives, and with simultaneous addition of SiO2 and CaO, wherein the total concentration of the additive was 1%. The morphology and particle size of the samples were determined by SEM and the crystal structure was determined by XRD and the phases were quantified by the Rietveld method. The XRD data showed the predominance of magnetoplumblico structure with hexagonal symmetry and space group P63/mmc. All samples have distributed grain heterogeneously, clustered in different masses, with acute forms and some of them featuring hexagonal shapes with different sizes.
Abstract: The development of ceramic matrix composites (CMCs) is currently of great importance in the field of ballistic protection. For that purpose, alumina, silicon carbide and boron carbide are usually used in civil and military armor. Combination of different materials results in increasingly lighter and tougher composite materials, which replace conventional materials in many applications, including aviation, aerospace, military, naval, and sports industry. The production of nanoparticle powders and nanostructured bodies may find many uses in CMCs. In this study, pseudoboehmite powders was synthesized through the sol-gel method. The main goal of this work was to obtain alpha-alumina from nanosized pseudoboehmite particles, aiming to improve the densification and reduction of sintering temperature of alumina. Both pseudoboehmite and alpha-alumina obtained might be used also as raw material for CMCs. The gel of pseudoboehmite, which was derived from aluminum nitrate and ammonium hydroxide, was calcined, thus originating the alpha-alumina used in this study. The powders were characterized by: X-ray diffraction (XRD), nitrogen adsorption isotherm, with specific surface area measured by BET method, thermogravimetric analysis (TG) and differential thermal analysis (DTA). The data show that the alpha-alumina obtained by burning the pseudoboehmite was highly pure.
Abstract: The mordenite zeolite is one of the most important industrially zeolites, used as a solid catalyst for various reactions hydrocracking, hydroisomerization, alkylation, reforming, alkane oxidation, Fischer-Tropsch reaction. The aim of this study was to hydrothermal synthesis mordenite zeolite in its sodium form under hydrothermal conditions, in organic-free synthesis. The form HMOR of the zeolite mordenite was obtained by an ion exchange. For the preparation of the catalysts precursor salts were used: ammonium heptamolybdate, nickel nitrate, cobalt nitrate dispersed from the impregnation by incipient wetness impregnation, such impregnated supports were calcined at 550 °C/4h to obtain the catalyst. The zeolite synthesized in the sodium form NaMOR in its ammonium form NH4MOR in form acid HMOR and their catalysts MoO3/HMOR, NiO/HMOR and Co2O3/HMOR were characterized by X-ray diffraction (XRD) and Fluorescence Spectroscopy of by Energy X-ray dispersive (FRX-ED). From the results it was possible to observe the formation of zeolite phase mordenite in its sodium and acid form and the effective impregnation and formation of the proposed catalysts.
Abstract: Molecular sieves have been applied to the triacylglycerides processing in the production of biodiesel through transesterification reaction. The purpose of obtain a material that has characteristics favorable to higher biodiesel conversion, this paper aims to synthesize molecular sieves SBA-15 and Al-SBA-15 on two reasons Si/Al (Si/Al= 10 and 100) evaluated in the transesterification reaction of soybean oil and investigate the potential of Si/Al ratios in the reaction over the acid each material. The catalysts were prepared by conventional hydrothermal method by varying the composition of the aluminum consequently altering the acidity of the material, since this reaction takes place in acid medium. The samples were characterized by X-Ray Diffraction (XRD), scanning electron microscopy (SEM), Spectroscopy in the infrared region by Fourier transform (FTIR). The results of the characterization of the catalysts have shown that the materials were successfully obtained, from the characterization observed. The biodiesel syntheses were conducted with soybean oil using ethyl alcohol 12: 1 relative to the oil and 5% of catalyst in the reactor with autogenous pressure. Were realized viscosity analyzes as conversion parameter of the vegetable oil into biodiesel. From the results of biodiesel viscosity was obtained a yield of 13% on average by using the Al-SBA-15. However, even not have remained within the specifications the standards of the National Petroleum, Natural Gas and Biofuels, catalysts showed efficiency compared with the SBA-15 in biodiesel synthesis.
Abstract: This study focuses in the synthesis of ceramic pigments based on the crystal structure of willemite (Zn2SiO4). The willemite obtained from the combination of commercial zinc oxide and rice husk ash is produced in a conventional ceramic process without the use of mineralizer agent and with the addition of cobalt oxide or nickel oxide as the source of chromophore ions. The synthesis temperature used was 1200°C. The characterization of pigments involves the use of X-ray diffraction and scanning electron microscopy. The pigments applied in matte enamel and sintered at 1100°C or 1200°C developed color between blue and beige. The construction of absorbance curves showed the color development behavior of each pigment. The results showed the possibility of obtaining willemite, from rice husk ash and the color development efficiency of the material, besides showing the interference of chromophore ion (Ni and Co) in color development.