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121.
122.
Eliana Aparecida Nonato Knupp Camilla Gonçalves Bof Silva Kerley Alberto Pereira de Oliveira Flávia Regina de Amorim Maria Célia Siqueira Maria Helena Tirollo Taddei Milton Batista Franco Helena Eugênia Leonhardt Palmieri Vanusa Maria Feliciano Jacomino 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(1):321-327
Phosphogypsum (PG) is a by-product of the phosphate fertilizer industry, which is produced by precipitation during the wet process of phosphate rocks. While commercial uses, in agriculture and in manufacturing gypsum board and Portland cement, consume less than a few percent of this by-product, the vast majority is disposed of on land in gypsum. In Brazil, three main industries are responsible for the production and storage of about 5.5 × 106 tons per year. PG may contain trace metals, non-metals, fluorides and natural radionuclides. Since, in Brazil, PG has been used for many years as soil amendment, it is important to know its availability, mainly in aquatic environments used for human consumption. In this case, more restrictive limits must be adopted. This work aimed to evaluate the mobility of metals in sand and clayey soils and, consequently, the contamination of drainage water through greenhouse-scale leaching and transport of toxic elements and radionuclides from soils fertilized with PG to crops. In general, it was observed that elemental concentrations were below the actual detection limit of the equipment for all conditions of interest, indicating a low mobility of the analyzed elements in the soil. 相似文献
123.
In this work we consider the Wulff construction at zero temperature for a class of Gibbs models and study the shape of the obtained droplets. Considering zero temperature we avoid all difficulties connected with the competition between energy and entropy. It allows us to study a quite wide class of models which provides a variety of shapes. The motivations of the study come from attempts to describe isotropic properties of some models on 2D lattice at zero temperature. The studied models are binary (the spin space is 0,1) with a ferromagnetic behavior such that the potential functions are not equal to zero only for some tiles with size 3×3. In fact, we study herein droplet shapes of a subclass of the ferromagnetic models with potential functions as mentioned above. This subclass of models is defined by a condition called regularity. We call the model classified here as having regular micro-boundaries. Several examples of non-regular models are also presented. 相似文献
124.
Birgit Daus Rainer Wennrich Peter Morgenstern Holger Weiß Helena Eugênia Leonhardt Palmieri Hermínio Arias Nalini Liliam Viana Leonel Roberto Pellacani Guedes Monteiro Rubens Martins Moreira 《Mikrochimica acta》2005,151(3-4):175-180
Several plants, especially ferns, have been shown to tolerate and accumulate high arsenic concentrations in soils. The leaves
and roots of the ferns Pteris vittata (Chinese brake) and Pityrogramma calomelanos as well as a medical plant (Baccharis trimera) were sampled together with their associated soils in a region impacted by ore mining, the Iron Quadrangle in Brazil, where
arsenic concentrations in the soils vary sharply (6–900 μg g−1). The bioaccumulation factors were found to be low compared to the literature data, which can be explained by the low water-soluble
fraction of arsenic in soil. The arsenic species in the plants were mainly arsenite. In comparison to the rhizoid samples,
the concentrations of arsenic were higher in the leaves of the fern samples. The medical plant behaved differently. The bioaccumulation
factor was low (0.7), and trimethylarsine oxide was detected as the third arsenic species beside arsenite and arsenate in
both the roots and the leaves. 相似文献
125.
Newton Carlos Santos Raphael Lucas Jacinto Almeida Shênia Santos Monteiro Eugênia Telis de Vilela Silva Vírgínia Mirtes de Alcântara Silva Anastácia Maria M.C. N. André Victor Herbert de Alcântara Ribeiro Ana Carla Oliveira de Brito 《印度化学会志》2022,99(7):100542
This study aimed to evaluate the use of ethanol (ET) and ultrasound (US) in convective drying of strawberry slices, as well as the effect on physicochemical, bioactive, and antioxidant parameters. For this, strawberry slices with a thickness of 0.005 m were pretreated with ET (in different volume fractions), US, and a combination of both. Drying kinetics were performed for control strawberry slices (without ET and US) and pretreated with 50% ethanol (ET50), 50% ethanol and ultrasonic (ET50US), 100% ethanol (ET100), and 100% ethanol and ultrasonic (ET100US) at a temperature of 60 °C. Empirical and diffusive models were fitted to the experimental data to describe the drying kinetics, and the fresh and dried slices were analyzed according to the parameters of water activity (aw), water content, total phenolic compounds (TPC), total anthocyanins (ATS), vitamin C and antioxidant activity (AA) (ABTS?+, DPPH?, and FRAP). The use of the ET100US combination provided an increase in the moisture transport process, higher drying rate, shorter process time (570 min), and reduction of aw to a safe value (aw <0.5), however, it sharply degraded the TPC, ATS, and AA. The ET50US pre-treatment even with a drying time of 690 min was the most efficient, since the values of TPC, ATS, and vitamin C suffered smaller reductions, where the AA varied in only 10.32%, 13.78% and 6.54% for the methods ABTS?+, DPPH?, and FRAP, respectively when compared to fresh strawberry. In this sense, it can be stated that the pre-treatment with 50% ethanol and ultrasound (ET50US) showed less reduction in the degradation of bioactive and antioxidant properties, and in the minimization of drying time for strawberry slices. 相似文献
126.
Eug Grandmougin 《Fresenius' Journal of Analytical Chemistry》1909,48(1):56-57
Ohne Zusammenfassung 相似文献
127.
Noelia Calvar Begoña González Ángeles Domínguez Eugénia A. Macedo 《The Journal of chemical thermodynamics》2009,41(5):617-622
Measurements of osmotic coefficients of BMimMSO4 (1-butyl-3-methylimidazolium methylsulfate) and MMimMSO4 (1,3-dimethylimidazolium methylsulfate) with ethanol, 1-propanol, and 2-propanol at T = 323.15 K are reported in this work. Vapour pressure and activity values for the binary systems studied are obtained from experimental results. The osmotic coefficients are correlated using the extended Pitzer model modified by Archer and the modified NRTL (MNRTL) model. The standard deviations obtained with both models are lower than 0.013 and 0.060, respectively. The parameters obtained with the extended Pitzer model of Archer are used to calculate the mean molal activity coefficients and the excess Gibbs free energy of the binary mixtures. 相似文献
128.
Gregor F. Friedl Gustavo Mockaitis José A. D. Rodrigues Suzana M. Ratusznei Marcelo Zaiat Eugênio Foresti 《Applied biochemistry and biotechnology》2009,159(1):95-109
A mechanically stirred anaerobic sequencing batch reactor containing anaerobic biomass immobilized on polyurethane foam cubes, treating low-strength synthetic wastewater (500 mg COD L?1), was operated under different operational conditions to assess the removal of organic matter and sulfate. These conditions were related to fill time, defined by the following feed strategies: batch mode of 10 min, fed-batch mode of 3 h and fed-batch mode of 6 h, and COD/[SO4 2?] ratios of 1.34, 0.67, and 0.34 defined by organic matter concentration of 500 mg COD L?1 and sulfate concentrations of 373, 746, and 1,493 mg SO4 2? L?1 in the influent. Thus, nine assays were performed to investigate the influence of each of these parameters, as well as the interaction effect, on the performance of the system. The reactor operated with agitation of 400 rpm, total volume of 4.0 L, and treated 2.0 L synthetic wastewater in 8-h cycles at 30?±?1°C. During all assays, the reactor showed operational stability in relation to the monitored variables such as COD, sulfate, sulfide, sulfite, volatile acids, bicarbonate alkalinity, and solids, thus demonstrating the potential to apply this technology to the combined removal of organic matter and sulfate. In general, the results showed that the 3-h fed-batch operation with a COD/[SO4 2?] ratio of 0.34 presented the best conditions for organic matter removal (89%). The best efficiency for sulfate removal (71%) was accomplished during the assay with a COD/[SO4 2?] ratio of 1.34 and a fill time of 6 h. It was also observed that as fill time and sulfate concentration in the influent increased, the ratio between removed sulfate load and removed organic load also increased. However, it should be pointed out that the aim of this study was not to optimize the removal of organic matter and sulfate, but rather to analyze the behavior of the reactor during the different feed strategies and applied COD/[SO4 2?] ratios, and mainly to analyze the interaction effect, an aspect that has not yet been explored in the literature for batch reactors. 相似文献
129.
Elena Gómez Noelia Calvar Ángeles Domínguez Eugénia A. Macedo 《The Journal of chemical thermodynamics》2011,43(6):908-913
Measurement of osmotic coefficients of binary mixtures containing several primary and secondary alcohols (1-propanol, 2-propanol, 1-butanol, 2-butanol, and 1-pentanol) and the pyridinium-based ionic liquid 1,3-dimethylpyridinium methylsulfate were performed at T = 323.15 K using the vapor pressure osmometry technique, and from experimental data, vapor pressure, and activity coefficients were determined. The extended Pitzer model modified by Archer, and the NRTL model modified by Jaretun and Aly (MNRTL) were used to correlate the experimental osmotic coefficients, obtaining standard deviations lower than 0.017 and 0.054, respectively. From the parameters obtained with the extended Pitzer model modified by Archer, the mean molal activity coefficients and the excess Gibbs free energy for the studied binary mixtures were calculated. The effect of the cation is studied comparing the experimental results with those obtained for the ionic liquid 1,3-dimethylimidazolium methylsulfate. 相似文献
130.
Sara C. Silvério Oscar Rodríguez José A. Teixeira Eugénia A. Macedo 《The Journal of chemical thermodynamics》2010,42(8):1063-1069
The Gibbs free energy of transfer of a suitable hydrophobic probe can be regarded as a measure of the relative hydrophobicity of the different phases. The methylene group (CH2) can be considered hydrophobic, and thus be a suitable probe for hydrophobicity. In this work, the partition coefficients of a series of five dinitrophenylated-amino acids were experimentally determined, at 23 °C, in three different tie-lines of the biphasic systems: (UCON + K2HPO4), (UCON + potassium phosphate buffer, pH 7), (UCON + KH2PO4), (UCON + Na2HPO4), (UCON + sodium phosphate buffer, pH 7), and (UCON + NaH2PO4). The Gibbs free energy of transfer of CH2 units were calculated from the partition coefficients and used to compare the relative hydrophobicity of the equilibrium phases. The largest relative hydrophobicity was found for the ATPS formed by dihydrogen phosphate salts. 相似文献