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- Author or Editor: A. Souza x
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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+.
Abstract
The present study describes the aerobic biodegradation process of a mixture of sanitary sewage sludge and lubricating oil. TG/DTG curves confirmed that the applied aerobic biological treatment decreased the organic material content and caused significant modifications in the thermal behavior of the studied substrates after the functioning period.
Abstract
The present study was carried out for evaluating the retention behavior of sanitary sewage in relation to cadmium and cobalt ions in an ascendant continuous-flow reactor. It was found that the studied sludge presented a high assimilation of the metals, probably due to the presence of anionic groups, which favors adsorption and complexation processes. Thermal analyses of the samples showed a shift in the thermal decomposition of the ‘in natura’ sludge, when compared with those of the samples spiked with the metals, confirming the possibility of interactions between the heavy metals and the anionic groups present in the sludge.
Abstract
Diesel oil has an important role in the field of urban traffic as well as in the transportation of products. However, the amount of the non-renewable sources is continuously decreasing. This fact and the environmental requirements brought the necessity to search for other, renewable sources. This paper aimed the dynamic kinetic calculation of thermal decomposition of castor oil, methanol biodiesel and ethanol biodiesel using Coats–Redfern, Madhusudanan and Ozawa methods. On the base of the thermogravimetric curves the following thermal stability order could be established: castor oil>ethanol biodiesel>methanol biodiesel. Kinetic data presented coherent results. Methanol biodiesel presented lower activation energy than ethanol biodiesel, suggesting that methanol biodiesel has a better quality for combustion.
Abstract
Biodiesel is a non-toxic biodegradable fuel that consists of alkyl esters produced from renewable sources, vegetal oils and animal fats, and low molecular mass alcohols, and it is a potential substitute for petroleum-derived diesel. Depending on the raw materials used, the amount of unsaturated fatty acids can vary in the biodiesel composition. Those substances are widely susceptible to oxidation processes, yielding polymeric compounds, which are harmful to the engines. Based on such difficulty, this work aims to evaluate the antioxidant activity of cashew nut shell liquid (cardanol), as additive for cotton biodiesel. The oxidative stability was investigated by the pressure differential scanning calorimetry (PDSC) and UV/Vis spectrophotometer techniques. The evaluated samples were: as-synthesized biodiesel — Bio T0, additivated and heated biodiesel — Bio A (800 ppm L−1 of hydrogenated cardanol, 150°C for 1 h), and a heated biodiesel — Bio B (150°C, 1 h). The oxidative induction time (OIT) analyses were carried out employing the constant volume operation mode (203 psi oxygen) at isothermal temperatures of 80, 85, 90, 100°C. The high pressure OIT (HPOIT) were: 7.6, 15.7, 22.7, 64.6, 124.0 min for Bio T0; 41.5, 77.0, 98.6, 106.6, 171.9 min for Bio A and 1.7, 8.2, 14.8, 28.3, 56.3 min for Bio B. The activation energy (E) values for oxidative processes were 150.0±1.6 (Bio T0), 583.8±1.5 (Bio A) and 140.6±0.1 kJ mol−1(Bio B). For all samples, the intensities of the band around 230 nm were proportional to the inverse of E, indicating small formation of hyper conjugated compounds. As observed, cardanol has improved approximately four times the cotton biodiesel oxidative stability, even after the heating process.
Abstract
Poly(3-hydroxybutyrate), PHB, has been structurally modified with maleic anhydride, MA, in the presence of triethylamine, TEA. Glass transition, melting, and crystallization temperature, obtained from DSC curves, and thermal degradation temperatures obtained from TG ones, were employed to evaluate the influence of the MA proportion on the modification in the PHB chain. According to the results, most of chain modification reactions are the 80/20 and 90/10 proportions. Observations suggest that most chain modification reactions occur when the ratio of PHB/MA is 80/20 or 90/10. This suggests that modifications of PHB in the presence of MA involve main chain scission.
The aim of this work was to evaluate, by comet assay, the possible inducing of DNA lesions in peripheral blood mononuclear cells of rats subjected to acute or chronic food deprivation. Wistar male rats were subjected to 72 h of partial (50%), or total acute food deprivation, and then allowed to recover for different time periods (24, 48 and 72 h). In other experiments, comet scores were determined in peripheral blood mononuclear cells of rats subjected to chronic food deprivation (25% and 50%) for 50 days. Blood aliquots were obtained before, during and after food deprivation. Comet assay was carried out, the comet units photographed and scored (class 0 up to 3). Acute and chronic food-deprived rats presented peripheral blood mononuclear cells with DNA lesions (comet classes 1, 2 and 3) and a significant increase ( p < 0.05) in the number of comet units compared with its basal level. The increase was proportional to acute food deprivation time, but after being taken off, it progressively returned to basal level after 48 h (partial group) or 72 h (total group). Chronic food-deprived rats presented a progressive increase of comet score up to 5 days, and a decrease thereafter to reach a basal level. Possible mechanisms of DNA lesions are discussed.
Abstract
Ln(TFA)3⋅3AZA (Ln=La, Sm, Er; TFA=trifluoroacetate and AZA=2-azacyclononanone)compounds were synthesized and characterized by microanalytical procedures, IR spectroscopy, X-ray powder diffraction, and thermal analysis. A kinetic study using La, Sm and Er thermogravimetric curves was carried out aiming to proposing a mechanism for the thermal decomposition of such complexes.
Abstract
The thermogravimetry (TG) is a technique used in the quality control of foods. In this work the moisture and ash contents in the rice and by-products (bran and husk), the thermal stability and the gelatinization process by conventional, thermogravimetric and calorimetric methods were studied. The moisture and ash contents obtained by TG and conventional methods did not present significant differences. The rice presented higher starch content, while the bran presented higher protein content. The thermogravimetric data presented the following thermal stability order: rice>bran>husk. The calorimetric curves indicated the gelatinization of the starch. The kinetic parameters were compatible.
Abstract
The powder and the bran of algaroba pods, submitted to drying temperatures of 55, 65, 75, 85, 95 and 105C, were studied by conventional and thermogravimetric methods. The dynamic thermogravimetric curves of the samples indicated the following thermal stability order: 105>55>65>95>85>75C. The powder and the bran of algaroba pods, dried at 55C, presented protein content higher and isothermal thermogravimetric profiles comparable. The calorimetric curves of samples, dried at 55C, indicated the gelatinization of starch.
