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| Registros recuperados: 17 | |
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| Mietta, Francesca; Chassagne, Claire; Verney, Romaric; Winterwerp, Johan C.. |
| In this paper, we study a population balance equation (PBE) where flocs are distributed into classes according to their mass. Each class i contains i primary particles with mass m p and size L p. All differently sized flocs can aggregate, binary breakup into two equally sized flocs is used, and the floc’s fractal dimension is d 0 = 2, independently of their size. The collision efficiency is kept constant, and the collision frequency derived by Saffman and Turner (J Fluid Mech 1:16–30, 1956) is used. For the breakup rate, the formulation by Winterwerp (J Hydraul Eng Res 36(3):309–326, 1998), which accounts for the porosity of flocs, is used. We show that the mean floc size computed with the PBE varies with the shear rate as the Kolmogorov microscale, as... |
| Tipo: Text |
Palavras-chave: Flocculation; Population balance equation; Discretization into classes; Kaolinite; Natural mud; Zeta-Potential. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00028/13875/11033.pdf |
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| Vendrame,Pedro Rodolfo Siqueira; Marchão,Robélio Leandro; Brito,Osmar Rodrigues; Guimarães,Maria de Fátima; Becquer,Thierry. |
| The objective of this work was to assess the relationship between macrofauna, mineralogy and exchangeable calcium and magnesium in Cerrado Oxisols under pasture. Twelve collection points were chosen in the Distrito Federal and in Formosa municipality, Goiás state, Brazil, representing four soil groups with varied levels of calcium + magnesium and kaolinite/(kaolinite + gibbsite) ratios. Soil macrofauna was collected in triplicate at each collection point, and identified at the level of taxonomic groups. Macrofauna density showed correlation with contents of kaolinite, gibbsite and exchangeable Ca + Mg in the soils. Mineralogy and exchangeable Ca + Mg had significant effects on taxonomic groups and relative density of soil macrofauna. The termites... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Gibbsite; Kaolinite; Soil fauna; Soil fertility; Total carbon. |
| Ano: 2009 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-204X2009000800031 |
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| Kummer,Larissa; Melo,Vander de Freitas; Barros,Yara Jurema. |
| In addition to the more reactive forms, metals can occur in the structure of minerals, and the sum of all these forms defines their total contents in different soil fractions. The isomorphic substitution of heavy metals for example alters the dimensions of the unit cell and mineral size. This study proposed a method of chemical fractionation of heavy metals, using more powerful extraction methods, to remove the organic and different mineral phases completely. Soil samples were taken from eight soil profiles (0-10, 10-20 and 20-40 cm) in a Pb mining and metallurgy area in Adrianópolis, Paraná, Brazil. The Pb and Zn concentrations were determined in the following fractions (complete phase removal in each sequential extraction): exchangeable; carbonates;... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Isomorphic substitution; Sequential analysis; Iron oxide; Kaolinite. |
| Ano: 2013 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832013000200015 |
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| Mateus,Ana Carolina Campos; Oliveira,Fábio Soares de; Varajão,Angélica Fortes Drummond Chicarino; Soares,Caroline Cibele Vieira. |
| ABSTRACT Pedological studies using X-ray diffraction (XRD), X-ray fluorescence (XRF), optical microscopy, and scanning electron microscopy (SEM-EDS) showed a Xanthic Ferralsol formed from the degradation of bauxite on a slope in the Caparaó region, in southeastern Brazil. We found a decrease in the number and size of bauxite fragments toward the top of the profiles, bauxite fragments that were more degraded at the top of the profiles, transformation of gibbsite into kaolinite, and absolute enrichment in silicon in the mass balance. These indicators suggest that resilication could be the major process responsible for formation of the soil; detailed studies are needed to verify the origin of the silica. The reintroduction of silica into the system occurs by... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Pedogenesis; Ferralsol; Kaolinite; Micromorphology. |
| Ano: 2017 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100314 |
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| Camargo,Livia Arantes; Marques Júnior,José; Pereira,Gener Tadeu. |
| A good knowledge of the spatial distribution of clay minerals in the landscape facilitates the understanding of the influence of relief on the content and crystallographic attributes of soil minerals such as goethite, hematite, kaolinite and gibbsite. This study aimed at describing the relationships between the mineral properties of the clay fraction and landscape shapes by determining the mineral properties of goethite, hematite, kaolinite and gibbsite, and assessing their dependence and spatial variability, in two slope curvatures. To this end, two 100 × 100 m grids were used to establish a total of 121 regularly spaced georeferenced sampling nodes 10 m apart. Samples were collected from the layer 0.0-0.2 m and analysed for iron oxides, and kaolinite and... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Iron oxides; Kaolinite; Gibbsite; Goethite; Hematite; Relief. |
| Ano: 2013 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832013000200001 |
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| Oliveira,Marisa T.G. de; Furtado,Sandra M.A.; Formoso,Milton L.L.; Eggleton,Richard A.; Dani,Norberto. |
| Kaolin at Campo Alegre Basin, Santa Catarina State, Brazil was formed from alteration of volcanic acid rocks. Halloysite clays dominate the clay fraction of the matrix of the kaolin body, whereas a poorly crystalline kaolinite is abundant in veins. Some primary blocky structures have high amounts of illite, in one mine, but in general, only low contents of illite-smectite, illite, chlorite-vermiculite, vermiculite and quartz were identified in the clay fraction of the samples. Toward the top of the mines, hematite and lepidocrocite appear in horizontal red and ochre colored levels and the amount of kaolinite increases compared to halloysite. The vertical zoning of alteration levels, the changes in mineralogy, the positive correlation between depth and... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Kaolinite; Halloysite; Halloysite morphology; Kaolin; Weathering; Clay genesis. |
| Ano: 2007 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000400008 |
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| Pires,Ana Christina Duarte; Melo,Vander de Freitas; Lima,Valmiqui Costa; Motta,Antônio Carlos Vargas. |
| The aim of this work was to evaluate the mineralogical and chemical characteristics of most representative soils of the Region of Curitiba, Paraná State. Samples were collected at different depths. The results showed: (a) the quartz was the only identified mineral at the silt and sand fractions. The dominant clay mineral was Kaolinite, with contents ranging from 676.7 to 820.8 g kg-1. The gibbsite was also an important constituent of the most weathered horizons and the hematite and goethite contents were low, mainly in the Histosol; (b) at the C horizon of the Inceptisol, high intensity of vermiculite/smectite reflections were detected (X-ray diffraction), justifying the high capacity of expansion and contraction, normally showed for this soil horizon; (c)... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Kaolinite; Crystalline and amorphous Fe and Al oxides; 2:1 minerals; XRD. |
| Ano: 2007 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132007000200001 |
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| Registros recuperados: 17 | |
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