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  • Author or Editor: A. Vasconcelos x
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Abstract  

This study deals with the influence of the exposure conditions on biological uptake, by looking into concentrations of Ni and V in lichen thalli and tree bark after continuous and discontinuous field trials at littoral sites impacted by anthropogenic emissions. Biomonitors were assessed by k 0-INAA and AAS. Correlations at Sines are more apparent than at Viana or Lisboa. When data from all sites are pooled, V shows correlations for practically every situation while Ni shows none, which may indicate a dissimilar uptake mechanism for each element. At Sines, V/Ni ratios reach values that comply with emissions from oil-related industries.

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Abstract  

In a biomonitoring study aiming to find alternatives to lower epiphytes as air-quality monitors, lichens and tree bark were exposed at different sites for discontinuous periods of 2 months and continuously. Native lichens were collected as well. The contents for 22 elements were obtained by both instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS). Quality control as asserted by analyzing ISE-921, NIST-1547 and TL-1 was good Losses of As and Se by volatilization during sample digestion and neutron irradiation were evident, Ca contents by ICP-MS appeared underestimated probably due to the formation of the insoluble fluoride. ICP-MS featured a better precision than INAA. Nonparametric statistics were applied to the ICP-MS replicates, to those determined by INAA, and to compare the results of both techniques. High or even excellent correlations were found between replicates in INAA, whereas, in ICP-MS, Cr and Ta were just fairly or not correlated. As an overall comparison of the techniques, biased results were found for As, Ba, Ce, Cr, Cs, Hf, La, Sc, Se, Ta, and Zn, unbiased results could be found for Ca, Co, Fe, K, Na, Rb, Sb, Sm, Tb, Th, and U.

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Journal of Thermal Analysis and Calorimetry
Authors: A. Vasconcelos, M. Dantas, M. Filho, R. Rosenhaim, E. Cavalcanti, N. Antoniosi Filho, F. Sinfrônio, I. Santos, and A. Souza

Abstract  

The influence of drying processes in the biodiesel oxidation was investigated by means of the oxidative induction time obtained from differential scanning calorimetry data. For this purpose, corn biodiesel was dried by different methods including: chemical (anhydrous sodium sulfate) and thermal (induction heating, heating under vacuum and with microwave irradiation). The drying efficiency was evaluated by monitoring IR absorption in the 3,500–3,200 cm−1 range and by the AOCS Bc 2-49 method. In general, the oxidative induction times increased inversely to the heating degree, except that of microwave irradiation, which was selective to water evaporation and caused low impact over the unsaturation of biodiesel. The DSC technique was shown to be a powerful tool to evaluate with high level of differentiation the influence of the drying process on the oxidative stability of biodiesel.

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Journal of Thermal Analysis and Calorimetry
Authors: O. S. Monteiro, A. G. Souza, L. E. B. Soledade, N. Queiroz, A. L. Souza, V. E. Mouchrek Filho, and A. F. F. Vasconcelos

Abstract

The vegetal species Pimenta dioica Lindl, popularly known as Jamaican pepper, is a 6–15 m tall tree, which belongs to the Mirtaceae family. Its fruits have an essential oil of great economic value in the international market, due to its high level of eugenol (its major compound), which is largely used in chemical and pharmaceutical industries. In this work, the extraction of the essential oil from the fruits of Pimenta dioica Lindl was carried out by the hydrodistillation method, using a modified Clevenger system. It was observed that the volume of the extracted oil reaches a maximum at 4 h, with a yield of 2.7% (m/m). The essential oil was characterized by physico-chemical analyses, such as density, refraction index, ethanol solubility, color, and appearance, besides UV–vis and infrared spectroscopy and gas chromatography/mass spectrometry. Thus, eugenol was confirmed as the major component of the essential oil of Pimenta dioica Lindl (77%). The technique of differential scanning calorimetry (DSC) was used for the determination of boiling point of the sample of essential oil from the fruits of Pimenta dioica (L.).

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Cleanio L. Lima, Hélvio S. A. de Sousa, Santiago J. S. Vasconcelos, Josué M. Filho, Alcemira C. Oliveira, Francisco F. de Sousa, and Alcineia C. Oliveira

Abstract

Sulfated molecular sieves were synthesized and characterized by XRD, FTIR, chemical analyses, acidity measurements and N2 adsorption–desorption isotherms. Sulfatation led to structural changes in the solid framework by increasing the acidity and accessibility of the acid sites. Br⊘nsted and Lewis acid sites of mild to high strength improved the conversion of alcohols, but the selectivity was modest over sulfated FAU type Y, ZSM-5 and γ-Al2O3 solids at temperatures lower than 200 °C. The characteristics of the sulfated AlSBA-15 molecular sieve in terms of acidity, textural properties and accessibility possibly make this solid useful for catalytic reactions involving bulky organic compounds.

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