Search Results

You are looking at 11 - 20 of 31 items for

  • Author or Editor: L. Soledade x
  • All content x
Clear All Modify Search
Journal of Thermal Analysis and Calorimetry
Authors: D. Brito, E. Silva, D. Rodrigues, M. Machado, M. Silva, V. Simões, M. Carvalho, L. Soledade, Iêda Santos, and A. Souza

Abstract  

A silico alumino phosphate with AFI structure (SAPO-5) was prepared in a two-phase medium and characterized by XRD, followed by the addition of TEA+. The kinetics of the TEA+/SAPO-5 thermal decomposition reaction was studied by isothermal and dynamic thermogravimetry. Two kinetic models, D3 and D4 based on diffusion processes were found as best to fit the isothermal data. On the other hand, the best fit for the dynamic data is the F1 first order reaction model. According to the apparent activation energy values, the use of the dynamic method indicates a higher temperature dependence than the isothermal method.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: A. M. Ramalho, M. M. Conceiçăo, V. J. Fernandes Jr., J. C. Machado, L. E. B. Soledade, and A. G. Souza
Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: M. Dantas, A. Almeida, Marta Conceição, V. Fernandes Jr, Iêda Santos, F. Silva, L. Soledade, and A. Souza

Abstract  

This work presents the characterization and the kinetic compensation effect of corn biodiesel obtained by the methanol and ethanol routes. The biodiesel was characterized by physico-chemical analyses, gas chromatography, nuclear magnetic resonance and thermal analysis. The physico-chemical properties indicated that the biodiesel samples meet the specifications of the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP) standards. The analyses by IR and 1H NMR spectroscopy indicated the ester formation. Gas chromatography indicated that biodiesel was obtained with an ester content above 97%. The kinetic parameters were determined with three different heating rates, and it was observed that both the methanol and ethanol biodiesel obeyed the kinetic compensation effect.

Restricted access

Abstract  

The conventional treatments of effluents containing heavy metals produce significant quantities of byproducts with recalcitrant characteristics, making necessary looking after alternative techniques in order to avoid the production of new contaminated residues. Sorption process of chromium and zinc in vertical columns loaded with sewage sludge and organic solid waste has been studied in this work. The data from the TG curves of the two sorbents presented significant differences when they were submitted to the metal uptake, being noticed the displacement of the thermal events towards lower temperatures for both types of sorbents studied. As it was expected, for both sorbents, an increase in the mass of samples has been observed at the completion of the thermal tests upon metal uptake. Therefore, these facts demonstrate that during the biosorption process a physico-chemical interaction took place between sorbents and metals, as it was evidenced by the more than 100 K increase in the decomposition temperatures as well as the variation of the ΔH values of the samples.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: F. Vieira, Soraia Souza, A. Oliveira, S. Lima, E. Longo, C. Paskocimas, L. Soledade, A. Souza, and Iêda Santos

Abstract  

In this study undoped and Cr, Sb or Mo doped TiO2 were synthesized by polymeric precursor method and characterized by X-ray diffraction, UV–VIS spectroscopy, infrared spectroscopy and thermogravimetry (TG). The TG curves showed a continuous mass loss assigned to the hydroxyl elimination and Cr6+ reduction. Doped TiO2 samples showed a higher mass loss assigned to water and gas elimination at lower temperatures. In these doped materials a decrease in the anatase–rutile phase transition temperature was observed. After calcination at 1,000 °C, rutile was obtained as a single phase material without the presence of Cr6+.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: H. Dantas, R. Mendes, R. Pinho, L. Soledade, C. Paskocimas, B. Lira, M. Schwartz, A. Souza, and Iêda Santos

Abstract  

Gypsum is a dihydrated calcium sulfate, with the composition of CaSO4⋅2H2O, with large application interest in ceramic industry, odontology, sulfuric acid production, cement, paints, etc. During calcination, a phase transformation is observed associated to the loss of water, leading to the formation of gypsum or anhydrite, which may present different phases. The identification of the phases is not so easy since their infrared spectra and their X-ray diffraction patterns are quite similar. Thus, in this work, temperature modulated differential scanning calorimetry (TMDSC) was used to identify the different gypsum phases, which can be recognized by their different profiles.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: A. G. Souza, I. P. Silva Filho, J. C. O. Santos, L. M. Nunes, I. M. G. Santos, L. E. B. Soledade, and M. M. Conceiçăo
Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: S. L. Porto, M. R. Cassia-Santos, I. M. G. Santos, S. J. G. Lima, L. E. B. Soledade, A. G. Souza, C. A. Paskocimas, and E. Longo
Restricted access
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.).

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Márcia Silva, Lydianne de O. Miranda, Maria Cassia-Santos, S. Lima, L. Soledade, E. Longo, C. Paskocimas, A. Souza, and Iêda Santos

Abstract  

Undoped and/or doped with 1 mol% of Co2+ Mg2TiO4 andMg2SnO4 powders were synthesized by the polymeric precursor method. The influence of the network former (Sn4+ or Ti4+) on the thermal, structural and optical properties was investigated. The recorded mass losses are due to the escape of water and adsorbed gases and to the elimination of the organic matter. Mg2TiO4 crystallizes at lower temperatures and also presents more ordered structure with a smaller unit call and having more intense green color than Mg2SnO4 has.

Restricted access