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- Author or Editor: E. Araújo x
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Abstract
Abstract
A study of Pu recovery at trace level from U solutions by ion exchange technique is presented. Plutonium retention >99.5% onto strong anionic resin, AG-X8, from nitric acid solutions and a 92% recovery using 0.4M HNO3 at 60°C as eluent, were obtained. Uranium interference in Pu sorption from mixed U/Pu nitrate solutions with low U/Pu ratio (
25) was not verified. However, for high U/Pu ratio solutions (10000), uranium interference in Pu retention on the resin, decreases to 59%. Selecting the loading conditions and using AG-X4 resin, 99% Pu retention was achieved. The Pu product is still contaminated with U and another purification cycle is recomended. A scheme for U/Pu first cycle separation is proposed.
Abstract
Environmental quality assessment studies have been conducted with tree species largely distributed in the Atlantic Forest. Leaf and soil samples were collected in the conservation unit Parque Estadual da Serra do Mar (PESM) nearby the industrial complex of Cubatão, São Paulo State, Brazil, and analyzed for chemical elements by instrumental neutron activation analysis. Results were compared to background values obtained in the Parque Estadual Carlos Botelho (PECB). The higher As, Fe, Hg and Zn mass fractions in the tree leaves of PESM indicated anthropogenic influence on this conservation unit.
Polystyrene/thermoplastic starch blends with different plasticizers
Preparation and thermal characterization
Abstract
Conventional plastics has a large impact in increasing the environment’s pollution. That’s why the interest has turned towards novel partially and completely biodegradable polymers. In this work, blends of polystyrene and thermoplastic starch with glycerol and Buriti (Mauritia flexuosa L.) oil as plasticizers were prepared. Samples were analyzed using TG/DTG and DSC techniques. The TG results indicated that the blends with Buriti oil are thermally more stable than those with glycerol. The DSC analysis that Buriti oil provides a higher degree of plasticization of PS, compared to the blends plasticized using glycerol under the studied conditions.
Abstract
The aim of this work was to obtain membranes from polyamide 6/montmorillonite clay nanocomposites through the phase inversion technique. The nanocomposites and membranes from polyamide 6/montmorillonite clay were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). Microporous and asymmetric membranes were successfully obtained from nanocomposites and the results showed that the salts were incorporated by intercalation between the organoclay layers and, apparently that the nanocomposites and membranes were thermally more stable than the pure polyamide.
Abstract
Polyethylene/montmorillonite clay nanocomposites were obtained via direct melt intercalation. The clay was organically modified with four different types of quaternary ammonium salts. The objective of this work is to study the use of montmorillonite clay in the production of nanocomposites by means on rheological, mechanical and crystallization properties of nanocomposites and to compare to the properties of the matrix and PE/unmodified clay nanocomposites. In general, the tensile test showed that the yield strength and modulus of the nanocomposites are close to the pure PE. Apparently, the mixture with Dodigen salt seems to be more stable than the pure PE and PE/unmodified clay.
Abstract
Vezetknv
Abstract
Nanocomposites containing both polyethylene and montmorillonite clay organically modified with four different types of quaternary ammonium salts were obtained via direct melt intercalation. Thus, the main purpose of this work was to evaluate the effect of the organoclay on the thermal stability of polyethylene. The organoclays were characterized by XRD, FTIR, DSC and TG. The polyethylene/organoclay nanocomposites were studied by XRD, TEM, TG, besides an evaluation of their mechanical properties. The results showed that the salts were incorporated by intercalation between the layers of the organoclay and, apparently that the nanocomposites were more thermally stable than pure polyethylene.
Abstract
The aim of this study was to use DSC and X-ray diffraction measurements to determine the pore size and pore wall thickness of highly ordered SBA-15 materials. The DSC curves showed two endothermic events during the heating cycle. These events were due to the presence of water inside and outside of mesopores. The results of pore radius, wall thickness and pore volume measurements were in good agreement with the results obtained by nitrogen adsorption measurement, XRD and transmission electron microscopy.
Abstract
The capture of carbon dioxide was carried out using MCM-41 and SBA-15 as adsorbents. These mesoporous materials were synthesized by the hydrothermal method, and subsequently functionalized with the di-iso-propylamine (DIPA). Then, they were characterized by XRD, BET, and TG/DTG. The X-ray diffraction patterns of the synthesized samples showed the characteristic peaks of MCM-41 and SBA-15, indicating that the structures of these materials were obtained. The functionalized samples presented a decrease of the intensities of these peaks, suggesting a decreasing in the structural organization of the material; however, the mesoporous structure was preserved. For the adsorption capacity measurements, the materials were previously saturated with carbon dioxide at 75 °C, and then desorbed in a thermobalance in the temperature range of 25–900 °C, under helium atmosphere. Desorption tests showed that the functionalized MCM-41 presented a weight loss of 7.5 wt%, against 5.9 wt% for SBA-15. The obtained values indicate that these nanostructured materials can be used as adsorbent for carbon dioxide capture.
