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Abstract  

Enhanced oil recovery process is based on the injection of chemical products (e.g. polymers, surfactants, gases) or thermal energy (originating from the injection of e.g. steam, hot water, in situ combustion) to recover crude oil. One of these processes use polymer solution to mobilize the oil in the reservoir. In this work the thermal decomposition kinetic of xanthan gum, guar gum and a blend (50/50 mass/mass%) was studied according to Ozawa–Flynn–Wall method. According to the kinetic analysis, the studied systems were copmpatible. The rheological behavior of the samples was studied in distilled water and seawater at different temperatures. Only the blend was studied in distilled water presented synergism (enhancement in material properties like stability and viscosity) which was confirmed through rheology.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: F. Tagliaferro, E. De Nadai Fernandes, M. Bacchi, P. Bode, and E. Joacir De França

Abstract  

Depending on the harvest conditions, coffee beans can be contaminated by soil when dropped to the ground. It is well known that agricultural soils act as sinks for agrochemicals applied to the crops. While coffee is brewed, substances present in the roasted and ground coffee beans are extracted by hot water, emphasizing the need to assess the possible transfer of impurities from the soil to the beverage. Soil-contaminated samples of roasted coffee beans were split into 2 groups according to the treatments: (a) washed and ground and (b) only ground. Brewing was performed in a household espresso machine for both coffees. The resulting beverage was freeze-dried and the elemental composition determined by instrumental neutron activation analysis (INAA). The mass fractions of the terrigenous elements Fe, La, Sc, Sm and Th in the freeze-dried non-washed coffee beverages were, at least, 2 times higher than in the washed samples. These elements are tracers of the soil, indicating that the impurities from the soil reached the beverage.

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Abstract  

The citrus variegated chlorosis (CVC) disease results in serious economical losses for the Brazilian citriculture. The influence of CVC disease on the elemental composition of citrus plants was investigated. Leaves of sweet orange varieties Hamlin, Pera Rio and Valencia were collected from healthy and CVC-affected trees for chemical characterization by instrumental neutron activation analysis (INAA). Significant differences between healthy and CVC-affected leaves were identified for Ca, Ce, Co, Eu, Fe, K, La, Na, Nd, Rb, Sc and Sm. Rare earth elements presented consistently higher mass fractions in the healthy leaves.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: E. Joacir De França, E. De Nadai Fernandes, M. Bacchi, F. Tagliaferro, and M. Saiki

Abstract  

Soil analysis could improve environmental studies since soil is the main source of chemical elements for plants. In this study, soil samples collected at 0–10 cm depth under tree crown projection were analyzed by INAA. Using the chemical composition of the leaf previously determined, the leaf-soil transfer factors of chemical elements could be estimated for the Atlantic Forest. Despite the variability of the intra-species, the transfer factors were specific for some plant species due to their element accumulation in the leaves. Similar Br-Zn combined transfer factors were obtained for the species grouped according to habitats in relation to their position (understory or dominant species) in the forest canopy.

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Abstract  

The effectiveness of a Compton suppression system (CSS) for instrumental neutron activation analysis of plant materials was evaluated. Suppression factors were measured with 137Cs sources. Five certified reference materials were analyzed and the detection limits calculated from both suppressed and unsuppressed spectra were compared. The CSS demonstrated to be useful for lowering the detection limits of ten out of sixteen elements tested, showing a maximum improvement factor of 3.9. The system performance was strongly influenced by the sample composition and also by the measurement conditions, indicating the importance of testing each individual sample type and analytical protocol.

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