Natural bentonite clay was treated in order to remove impurities to increase the cation exchange capacity of the montmorillonite
and to obtain a more effective radioactive cesium sorption. It was found that the treatment of the clay determines the amount
of sorbed cesium. On the other hand it was shown that montmorillonites may retain cesium through several mechanisms which
provide strongly retained cations occupying cationic sites into the clay structure or sorbed cesium which may be lost by purification
Authors:R. Castro, S. Prasad, R. Gomes, I. Lima, A. Souza, T. Melo, and S. Lima
Co80Nb14B6, Co80Nb12B8 and Co80Nb10B10 amorphous alloys were obtained through the melt-spinning process. The ribbons structure was investigated by X-ray diffractometry
and the crystallization process and the thermal stability were studied by means of differential thermal analysis and thermomechanical
technique. It was observed that the crystallization temperature depends on the alloy composition and occurs in a temperature
range between 420 and 730C. The coercive field of all alloys was determined by magnetic susceptibility measurements, the
values of which range from 2.78 to 5.95 A m-1.
Authors:M. Barroso, T. Melo, S. Prasad, R. Gomes, I. Lima, A. Souza, and S. Lima
The crystallization behavior of Co75-xFexGe15B10 (x=3.0, 4.6 and 6.0) amorphous alloys was monitored by differential thermal analysis and thermo-mechanical analysis. The crystallization
process of the melt spun ribbons was interrupted at 450, 525, 650, 800 and 900C and their microstructures were investigated
by X-ray diffractometry. It was observed that the crystallization occurs in a sequential mode attributed to the formation
of different types of precipitates. It was shown that the crystallization products change as a function of Fe content. After
full crystallization, GeFe, Co3B, FeGe2 and Co2Ge compounds were found as well as a Co rich solid solution.
Authors:J. Santana, L. Lima, J. Torres, F. Martínez, and S. Olivares
Vegetable tannin sorbent is evaluated as ion exchange resin using a multitracer study on the adsorption behavior of various elements. Lisiloma latisiliqua L. tannins, polycondensated into spherical pellets were chosen as sorbent resin material. Sorption evaluation of Ce, Cu(II), U(VI), Eu, Fe(III), Th, Nd as representatives of different classes of metal ions were done at different pH values. The distribution ratio of the studied elements was calculated from laboratory experiments. Tannic ion exchange material shows excellent ability for actinides and rare earth elements adsorption from waters. Using radiotracers, the number of catechins subunits involve in each tannin-metal complex was determined.
Authors:J. Torres, S. Olivares, D. De La Rosa, L. Lima, F. Martínez, C. Munita, and D. Favaro
Adsorption of mercury(II) and methylmercury by two tannin sorbents was investigated using radiotracers. High sorption capacities
for mercury are registered for both sorbents at pH 7. ForEucaliptus Saligna Sm sorbent (ETS) the maximum sorption capacity was 1.2±0.2 mmol/g and forLysiloma latisiliqua sorbent (LTS) was 8.5±0.2 mmol/g. Methylmercury adsorption maximum was recorded at pH 4 and in buffered solutions at pH2.
This species can be recovered in the presence of mercury(II). Influence of different ions present in water was examined. High
recoveries were reported for ETS in tap water samples but a decrease of uptake is observed for seawater.
Authors:L. Lima, S. Olivares, F. Martínez, J. Torres, D. de la Rosa, and C. Sepúlveda
Adsorption of Cr(VI) by two tannin sorbents is evaluated using radiotracers. Evaluation of the sorption process shows that
the Cr(VI)-tannin molecule binding is the principal responsible for chromium adsorption. High sorption capacities were registered
for both sorbents at pH 2. ForEucaliptus Saligna Sm sorbent (ETS) sorption capacity is 0.92±0.03 mmol/g and forLysiloma latisiliqua sorbent (LTS) is 3.8±0.3 mmol/g. Influence of different ions present in water is examined. High sorption capacity is reported
for LTS in sea and tap water samples. It represents 90–94% of adsorption in distillated water.
Authors:C. T. Carvalho, F. J. Caires, L. S. Lima, and M. Ionashiro
Solid-state M-2-MeO-CP compounds, where M represents bivalent Mn, Fe, Co, Ni, Cu, Zn and 2-MeO-CP is 2-methoxycinnamylidenepyruvate, were synthesized for the first time. Simultaneous thermogravimetry and differential thermal analysis, differential scanning calorimetry, X-ray powder diffractometry, infrared spectroscopy, TG-FTIR system, elemental analysis and complexometry have been used to characterize and to study the thermal behaviour of the compounds. The dehydration in all the compounds, except for iron occurs in a single step. The thermal decomposition of the anhydrous compounds occurs in two or three steps with the formation of the respective oxides, Mn3O4, Fe2O3, Co3O4, NiO, CuO and ZnO, as final residue. The results also provided information concerning the thermal behaviour and identification of the gaseous products evolved during the heating of these compounds.
Authors:E. Y. Ionashiro, F. J. Caires, A. B. Siqueira, L. S. Lima, and C. T. Carvalho
Characterization, thermal stability and thermal decomposition of light trivalent lanthanide fumarates, as well as, the thermal behaviour of fumaric acid and its sodium salt were investigated employing simultaneous thermogravimetry and differential thermal analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), TG–FTIR techniques, elemental analysis and complexometry. On heating, sublimation of fumaric acid is observed, while the thermal decomposition of the sodium fumarate occurs with the formation of a mixture of sodium carbonate and carbonaceous residue. The thermal decomposition of light trivalent lanthanide fumarates occurs in consecutive and/or overlapping steps with the formation of the respective oxides: CeO2, Pr6O11, and Ln2O3 (Ln = La, Nd, Sm, Eu, Gd).
Authors:Sonia de Almeida, Giseli Bernabé, Marisa S. Crespi, Clóvis A. Ribeiro, and Evaneide Nascimento Lima
The organic fraction of urban solid residues disposed of in sanitary landfills during the decomposition yields biogas and leachate, which are sources of pollution. Leachate is a resultant liquid from the decomposition of substances contained in solid residues and it contains in its composition organic and inorganic substances. Literature shows an increase in the use of thermoanalytical techniques to study the samples with environmental interest, this way thermogravimetry is used in this research. Thermogravimetric studies (TG curves) carried out on leachate and residues shows similarities in the thermal behavior, although presenting complex composition. Residue samples were collected from landfills, composting plants, sewage treatment stations, leachate, which after treatment, were submitted for thermal analysis. Kinetic parameters were determined using the Flynn–Wall–Ozawa method. In this case they show little divergence between the kinetic parameter that can be attributed to different decomposition reaction and presence of organic compounds in different phases of the decomposition with structures modified during degradation process and also due to experimental conditions of analysis.