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Abstract  

Montmorillonite was modified with octadecyltrimethylammonium chloride, under different reaction conditions, as evidenced by TG and XRD. TG curves presented two degradation peaks (295 and 395C). At low salt concentrations, only the 395C-degradation appeared, which increased with reaction time to the limit of 9 g of salt/100 g of clay. The second peak presented a limit at 17/100 m/m of salt/clay ratio. XRD analysis confirmed clay organic modification as the basal distance increased, showing greater reaction time effect than the salt mass effect, and with only one d-spacing. This suggested that an intercalation complex was formed but also that octadecyltrimethylammonium was adsorbed on the external surfaces of clay particles.

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Abstract  

Instrumental neutron activation analysis (INAA) was applied to determine the elements Br, Ca, Cl, Cu, Fe, I, K, Mg, Mn, Na, Rb, S, V, Zn in five varieties of Brazilian corn, resulting from the studies carried out in order to increase their protein contents. The accuracy of the method was evaluated by means of reference material analysis. In general, the precision of the method was lower than 15%, except for Cu, I and S. Sensitivity and detection limit were also determined. Besides, tryptophan contents were determined. It was observed that the tryptophan content in improved corn samples was twice as large as in the normal samples. However, the same ratio was not observed in the inorganic element contents.

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Microalgae are promising alternatives to sequestration of carbon and reduction of environmental problems, e.g. the greenhouse effect and industrial water pollution. Depending on the growth conditions, microalgae can differ in their metabolism products, leading them to grow at different rates. Intracellular reactions and nutritional requirements from cell metabolism, as well as biomass composition, may vary in function of the temperature. In this study, the biotechnological potential of three microalgae strains from the species was evaluated in terms of growth, biomass composition, fatty acid profile, and chlorophyll and carotenoids contents. Each of the three species demonstrated different potential depending on their metabolisms: Scenedesmus spinosus presented fastest growth and had the highest protein content (52.99%), Pseudokirchneriella subcapitata presented the highest content of lipid extracted (26.51%), and Scenedesmus acuminatus showed increased production of chlorophyll (5.25 mg l–1) and carotenoid (1.02 mg l–1) pigments.

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Abstract  

A method for simultaneous determination of Cr, Fe, Co, Ni, Cu, Zn, As e Pb in liquid chemical waste using Energy Dispersive X-Ray Fluorescence (EDXRF) technique was evaluated. A small sample amount (200 μL) was dried on a 6.35 μm thickness Mylar film at 60 °C and the analyses were carried out using an EDXRF spectrometer operated with an X-ray Mo tube (Zr filter) at 30 kV/20 mA. The acquisition time was 300 s and the Ga element was utilized as internal standard at 25 mg/L for quantitative analysis. The method trueness was assessed by spiking and the detection limit for those elements ranged from 0.39 to 1.7 mg/L. This method is notable because it assists the choice of the more appropriated waste treatment procedure, in which inter elemental interference is a matter of importance. In addition, this inexpensive method allows a non-destructive determination of the elements from 19K to 92U simultaneously.

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Abstract

It is well established that gallium insertion into the hydroxiapatite matrix as practiced in orthopedics protects bone from resorbtion and improves the biomechanical properties of the skeletal system. The research presented in this article is an investigation into the thermal decomposition of gallium nitrate, which is part of a complex process leading to the preparation of a hybrid matrix. It was demonstrated that after melting of the hexahydrate in its own water there occurs a simultaneous condensation of 4 mol of initial monomer Ga(NO3)3·6H2O into a tetramer Ga4O4(NO3)4. The resulting inorganic cycle gradually loses N2O5 and, through the formation of unstable oxynitrates, is transformed into gallium oxide. The use of molecular mechanics for comparing the potential energies of consecutive products of thermal decomposition permitted an evaluation of their stability and an appropriate interpretation of the experimental data.

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Abstract  

This study aimed to evaluate minor and trace elements in the water during different water purification steps of a deionized water production plant, located at CENA, by total-reflection X-ray fluorescence (TXRF) technique, using Ga as internal standard for elemental quantification. This approach was capable of determining Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, As, Se, Br, Rb at concentrations higher than 40–100 μg L−1, and for K, Ca, Sc, Ti, V and Sr at concentrations higher than sub mg L−1 in the water samples. TXRF spectrometer encompasses an X-ray tube with a Mo target with a Zr filter. The elemental characteristic X-rays were recorded by a Si(Li) semiconductor detector and the X-ray spectra deconvoluted by AXIL software.

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Summary  

This paper presents the first measurement of the elemental composition of the suspended particulate matter in the atmosphere of Londrina city (Paraná State, Brazil). The sampling was accomplished in the summer of 2003 and in the winter of 2002, with a stacker filter holder, collecting simultaneously the fine particulates (PM2.5) and the coarse particulates (PM10). The concentration of K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br and Pb associated with particulate matter was determined by energy dispersive X-ray fluorescence. The results of the grouping analysis suggested that the elements in the aerosol particles came from two sources: soil re-suspension and industrial or anthropogenic activities.

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Abstract  

Ten rum (aguardente) samples commercialized in Piracicaba region, São Paulo State, Brazil Southeast, were analysed by energy-dispersive X-ray fluorescence (EDXRF) using ammonium pyrrolidinedithiocarbamate (APDC) preconcentration in order to determine Fe, Cu and Zn concentrations. The effect of sucrose (2%) was also studied in this methodology, using a multielemental standard solution (40% ethanol). Copper concentrations in two samples were higher than the value allowed by Brazilian law. Limits of detection for these elements were in the ng.ml-1 range.

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