The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Joseph W. Stucki - One of the best experts on this subject based on the ideXlab platform.
-
Clay Fraction mineralogy of a Cambisol in Brazil
Hyperfine Interactions, 2006Co-Authors: A. S. Anastacio, José Domingos Fabris, Joseph W. Stucki, F. S. Coelho, I. V. Pinto, J. H. M. VianaAbstract:Clay minerals having a 2:1 (tetrahedral:octahedral sheet) structure may be found in strongly weathering soils only if the local pedo-climatic environment prevents them from further weathering to other minerals such as iron oxides. The Clay minerals impart important chemical properties to soils, in part by virtue of changes in the redox state of iron in their crystal structures. Knowing the chemical nature of soil Clays is a first step in evaluating their potential reactivity with other soil constituents and processes, such as the chemical decomposition of organic substrates to be potentially used in environmental remediation. The purpose of this work was to characterize the iron oxides and iron-bearing Clay minerals from a B horizon of a Cambisol developed on tuffite in the State of Minas Gerais, Brazil, using chemical analysis, powder X-ray difFraction, Mossbauer spectroscopy, and thermal analysis. The iron oxides of this NaOH-treated Clay-Fraction were found to contain mainly maghemite (γFe2O3) and superparamagnetic goethite (αFeOOH). Kaolinite (Al2Si2O5(OH)4), smectite, and minor portions of anatase (TiO2) were identified in the CBD-treated sample.
-
changes in the cec of a soil smectite kaolinite Clay Fraction as induced by structural iron reduction and iron coatings dissolution
Applied Clay Science, 2006Co-Authors: F. Favre, Christian Bogdal, S. Gavillet, Joseph W. StuckiAbstract:Abstract Studies of the effects of changes in iron (Fe) redox status on cation exchange capacity (CEC) and other physical and chemical properties of Clays have typically focused on purified Clays or Clay Fractions, but little attention has been given to systems with mixed mineralogy, which is more typical of natural soils. The objective of this study was to measure and establish any correlation between changes in CEC and Fe mineralogy that occurs in a mixed-mineral Clay system undergoing chemical reduction. The Clay Fraction (SE1089) of a soil containing a mixture of smectite, kaolinite, and Fe oxide was investigated using variable-temperature Mossbauer spectroscopy, chemical analyses, and reductive dissolution in CBD media. This study revealed that in the unreduced Clay Fraction half of the total Fe was structural iron (FeStr) in the smectite and half was in goethite. The goethite particles were estimated to be 9 nm in mean crystal diameter (MCD) and to contain 9% Al substituted isomorphously for Fe. An evolution of the different Fe pools and changes in CEC of the mixture were observed. The CEC of SE1089 smectite Fraction sharply increased upon reduction, similar to the SWa-1 reference Clay, even though the FeStr content of SE1089 is much less. Results revealed a correlation of the increase in CEC with FeStr reduction and oxide dissolution, giving a direct connection between the total coating content and the rate of dissolution. For this reason, dissolution kinetics appears to be a key factor in understanding the control of CEC by iron coated material. In particular, in natural media governed by bacterial activity, different dissolution kinetics are expected.
-
Changes in the CEC of a soil smectite–kaolinite Clay Fraction as induced by structural iron reduction and iron coatings dissolution
Applied Clay Science, 2006Co-Authors: F. Favre, Christian Bogdal, S. Gavillet, Joseph W. StuckiAbstract:Abstract Studies of the effects of changes in iron (Fe) redox status on cation exchange capacity (CEC) and other physical and chemical properties of Clays have typically focused on purified Clays or Clay Fractions, but little attention has been given to systems with mixed mineralogy, which is more typical of natural soils. The objective of this study was to measure and establish any correlation between changes in CEC and Fe mineralogy that occurs in a mixed-mineral Clay system undergoing chemical reduction. The Clay Fraction (SE1089) of a soil containing a mixture of smectite, kaolinite, and Fe oxide was investigated using variable-temperature Mossbauer spectroscopy, chemical analyses, and reductive dissolution in CBD media. This study revealed that in the unreduced Clay Fraction half of the total Fe was structural iron (FeStr) in the smectite and half was in goethite. The goethite particles were estimated to be 9 nm in mean crystal diameter (MCD) and to contain 9% Al substituted isomorphously for Fe. An evolution of the different Fe pools and changes in CEC of the mixture were observed. The CEC of SE1089 smectite Fraction sharply increased upon reduction, similar to the SWa-1 reference Clay, even though the FeStr content of SE1089 is much less. Results revealed a correlation of the increase in CEC with FeStr reduction and oxide dissolution, giving a direct connection between the total coating content and the rate of dissolution. For this reason, dissolution kinetics appears to be a key factor in understanding the control of CEC by iron coated material. In particular, in natural media governed by bacterial activity, different dissolution kinetics are expected.
Robert Moritz - One of the best experts on this subject based on the ideXlab platform.
-
the geochemical behavior of f and cl during the weathering diagenesis metamorphism anatexis cycle insights from the Clay Fraction of fine sands from the amazon river mouth and metapelititic rocks from the serido belt brazil
Chemical Geology, 2019Co-Authors: Ricardo Sallet, Jonathan D Price, Helenice Vital, Robert MoritzAbstract:Abstract The average contents F = 788 ppm and Cl 10 of the Clay Fraction from Amazon River sediments are comparable only to Cl-poor MORB and evolved granite and rhyolite. The high content Cl = 180 ppm and low F/Cl = 3 of average shale is due to interaction of the sediments with high salinity diagenetic fluids. The Serido schist belt is used to assess the behavior of F and Cl during shale metamorphism and anatexis. Its ratio F/Cl >10 ppm is high compared to average shale and is related to the strong partitioning of Cl into metamorphic fluids. The obtained data suggest that the Cl partitioned into shales during diageneses is released back into fluids produced during metamorphic conditions. The experimental data indicate that anatexis of mica schist significantly Fractionates F/Cl ratios producing schist residue with F/Cl > 38 and peraluminous melts with F/Cl = 6.
-
The geochemical behavior of F and Cl during the weathering–diagenesis–metamorphism–anatexis cycle. Insights from the Clay Fraction of fine sands from the Amazon River mouth and metapelititic rocks from the Seridó Belt, Brazil
Chemical Geology, 2019Co-Authors: Ricardo Sallet, Jonathan D Price, Helenice Vital, Robert MoritzAbstract:Abstract The average contents F = 788 ppm and Cl 10 of the Clay Fraction from Amazon River sediments are comparable only to Cl-poor MORB and evolved granite and rhyolite. The high content Cl = 180 ppm and low F/Cl = 3 of average shale is due to interaction of the sediments with high salinity diagenetic fluids. The Serido schist belt is used to assess the behavior of F and Cl during shale metamorphism and anatexis. Its ratio F/Cl >10 ppm is high compared to average shale and is related to the strong partitioning of Cl into metamorphic fluids. The obtained data suggest that the Cl partitioned into shales during diageneses is released back into fluids produced during metamorphic conditions. The experimental data indicate that anatexis of mica schist significantly Fractionates F/Cl ratios producing schist residue with F/Cl > 38 and peraluminous melts with F/Cl = 6.
Ricardo Sallet - One of the best experts on this subject based on the ideXlab platform.
-
the geochemical behavior of f and cl during the weathering diagenesis metamorphism anatexis cycle insights from the Clay Fraction of fine sands from the amazon river mouth and metapelititic rocks from the serido belt brazil
Chemical Geology, 2019Co-Authors: Ricardo Sallet, Jonathan D Price, Helenice Vital, Robert MoritzAbstract:Abstract The average contents F = 788 ppm and Cl 10 of the Clay Fraction from Amazon River sediments are comparable only to Cl-poor MORB and evolved granite and rhyolite. The high content Cl = 180 ppm and low F/Cl = 3 of average shale is due to interaction of the sediments with high salinity diagenetic fluids. The Serido schist belt is used to assess the behavior of F and Cl during shale metamorphism and anatexis. Its ratio F/Cl >10 ppm is high compared to average shale and is related to the strong partitioning of Cl into metamorphic fluids. The obtained data suggest that the Cl partitioned into shales during diageneses is released back into fluids produced during metamorphic conditions. The experimental data indicate that anatexis of mica schist significantly Fractionates F/Cl ratios producing schist residue with F/Cl > 38 and peraluminous melts with F/Cl = 6.
-
The geochemical behavior of F and Cl during the weathering–diagenesis–metamorphism–anatexis cycle. Insights from the Clay Fraction of fine sands from the Amazon River mouth and metapelititic rocks from the Seridó Belt, Brazil
Chemical Geology, 2019Co-Authors: Ricardo Sallet, Jonathan D Price, Helenice Vital, Robert MoritzAbstract:Abstract The average contents F = 788 ppm and Cl 10 of the Clay Fraction from Amazon River sediments are comparable only to Cl-poor MORB and evolved granite and rhyolite. The high content Cl = 180 ppm and low F/Cl = 3 of average shale is due to interaction of the sediments with high salinity diagenetic fluids. The Serido schist belt is used to assess the behavior of F and Cl during shale metamorphism and anatexis. Its ratio F/Cl >10 ppm is high compared to average shale and is related to the strong partitioning of Cl into metamorphic fluids. The obtained data suggest that the Cl partitioned into shales during diageneses is released back into fluids produced during metamorphic conditions. The experimental data indicate that anatexis of mica schist significantly Fractionates F/Cl ratios producing schist residue with F/Cl > 38 and peraluminous melts with F/Cl = 6.
R. J. Gilkes - One of the best experts on this subject based on the ideXlab platform.
-
Scanning and transmission analytical electron microscopy (STEM-EDX) identifies minor minerals and the location of minor elements in the Clay Fraction of soils
Applied Clay Science, 2017Co-Authors: Araína Hulmann Batista, Vander De Freitas Melo, R. J. GilkesAbstract:Abstract Chemical analysis and element mapping of Clay-size grains using scanning and transmission electron microscopy (STEM-EDX) greatly facilitates investigations of minor minerals and the location (speciation) of minor elements in the Clay Fraction. STEM-EDX was used to identify minor minerals and determine the composition of grains in the Clay Fraction of three soils developed from marble, phyllite, mica-schist and granite in southern Brazil. Before STEM-EDX analysis the Clay was treated with citrate-bicarbonate-dithionite or NaOH to remove iron oxides and kaolin respectively. Chemical formulas of Clay-size grains were calculated based on EDX analyses. Minerals that were not detected by XRD in the Clay Fraction were identified from STEM-EDX analyses, including fluorophlogopite, baileychlore, saponite-sauconite, gorceixite and crandallite. Partly weathered (altered) particles of fluorophlogopite had reduced F, K and Mg concentrations. High Zn concentrations in phyllite and mica-schist parent rocks were associated with the presence of baileychlore in the Clay. Barium occurred in K-feldspar, smectite and illite. Small amounts of Ti were allocated in octahedral layer of smectite and illite. The chemical analyses of Clay size particles supplied by high resolution STEM-EDX has great potential for investigating the location of elements within minerals in the Clay Fraction.
-
Impact of Clay mineralogy on stabilisation of organic matter in the Clay Fraction of a Neo-Luvisol and a Cambisol.
2010Co-Authors: L. Caner, Claire Chenu, F. Hubert, C. Moni, R. J. Gilkes, N. PrakongkepAbstract:This study was focused on the identification and quantification of the Clay mineral assemblage of the Clay Fraction of two surface soil samples from a Neo8Luvisol on loess deposit in the Parisian basin (France), and a Cambisol on ancient ferrallitic soil in south8west France in relation to their organic carbon content. The two soil samples exhibit contrasted mineralogy. In order to better characterize the Clay mineralogy the < 2 Em Fraction was subsequently Fractionated in sub8micronic Fractions. The < 0.04 Em Fraction of the Neo8Luvisol is rich is smectite both as discrete and mixed layers while in the Cambisol, kaolinite is the dominant species. However the carbon content is larger in the < 0.04 Em Fraction of the Cambisol compared to the Neo8 Luvisol. In the 0.2 – 2 Em Fraction organic carbon content is larger for the Neo8Luvisol. These preliminary results support the hypothesis that in the Cambisol the poorly crystallised kaolinite exhibits a large specific surface area that allow important organic matter sorption, and that in the Neo8Luvisol smectite favours, in addition to sorption, organic matter stabilisation within micro8aggretates that leads to larger content in organic carbon of the < 2 Em Fraction.
-
The kinetics of potassium release to sodium tetraphenylboron solution from the Clay Fraction of highly weathered soils
Applied Clay Science, 2010Co-Authors: Timtong Darunsontaya, Anchalee Suddhiprakarn, Irb Kheoruenromne, R. J. GilkesAbstract:Abstract Thirty six soil Clay samples from surface and subsurface horizons of 18 Thai upland Oxisols and Ultisols under a tropical monsoonal environment were characterized for chemical composition, mineralogy and K release to 0.3 M sodium tetraphenylboron (NaTPB) solution for periods up to 168 h. The Clay Fraction was dominated by kaolinite with various amounts of accessory minerals and analytical TEM showed that most Clays contained small amounts of illite. The amounts of K released to the NaTPB solution from illite-containing Clays were higher than from Clays containing kaolinite and inhibited vermiculite with no detectable illite. Potassium release kinetics for all samples are adequately described by the parabolic diffusion (r = 0.91–0.99), power function (r = 0.87–0.99) and Elovich equations (r = 0.86–0.99). The intercept constants of the equations are strongly positively related to the ratio of illite to kaolinite and total K and Mg contents of the Clays. These relationships indicate that minor amounts of illite in these Clays strongly affect the kinetics of K release. The slope constants of the parabolic and Elovich equations are also positively related to these Clay properties. Some kaolinite particles contained K which may be present in residual micaceous layers interleaved in kaolinite crystals. XRD patterns from samples extracted with NaTPB show a decrease in illite peak intensity with a concomitant increase in vermiculite peak intensity due to K removal from illite by NaTPB.
F. Favre - One of the best experts on this subject based on the ideXlab platform.
-
changes in the cec of a soil smectite kaolinite Clay Fraction as induced by structural iron reduction and iron coatings dissolution
Applied Clay Science, 2006Co-Authors: F. Favre, Christian Bogdal, S. Gavillet, Joseph W. StuckiAbstract:Abstract Studies of the effects of changes in iron (Fe) redox status on cation exchange capacity (CEC) and other physical and chemical properties of Clays have typically focused on purified Clays or Clay Fractions, but little attention has been given to systems with mixed mineralogy, which is more typical of natural soils. The objective of this study was to measure and establish any correlation between changes in CEC and Fe mineralogy that occurs in a mixed-mineral Clay system undergoing chemical reduction. The Clay Fraction (SE1089) of a soil containing a mixture of smectite, kaolinite, and Fe oxide was investigated using variable-temperature Mossbauer spectroscopy, chemical analyses, and reductive dissolution in CBD media. This study revealed that in the unreduced Clay Fraction half of the total Fe was structural iron (FeStr) in the smectite and half was in goethite. The goethite particles were estimated to be 9 nm in mean crystal diameter (MCD) and to contain 9% Al substituted isomorphously for Fe. An evolution of the different Fe pools and changes in CEC of the mixture were observed. The CEC of SE1089 smectite Fraction sharply increased upon reduction, similar to the SWa-1 reference Clay, even though the FeStr content of SE1089 is much less. Results revealed a correlation of the increase in CEC with FeStr reduction and oxide dissolution, giving a direct connection between the total coating content and the rate of dissolution. For this reason, dissolution kinetics appears to be a key factor in understanding the control of CEC by iron coated material. In particular, in natural media governed by bacterial activity, different dissolution kinetics are expected.
-
Changes in the CEC of a soil smectite–kaolinite Clay Fraction as induced by structural iron reduction and iron coatings dissolution
Applied Clay Science, 2006Co-Authors: F. Favre, Christian Bogdal, S. Gavillet, Joseph W. StuckiAbstract:Abstract Studies of the effects of changes in iron (Fe) redox status on cation exchange capacity (CEC) and other physical and chemical properties of Clays have typically focused on purified Clays or Clay Fractions, but little attention has been given to systems with mixed mineralogy, which is more typical of natural soils. The objective of this study was to measure and establish any correlation between changes in CEC and Fe mineralogy that occurs in a mixed-mineral Clay system undergoing chemical reduction. The Clay Fraction (SE1089) of a soil containing a mixture of smectite, kaolinite, and Fe oxide was investigated using variable-temperature Mossbauer spectroscopy, chemical analyses, and reductive dissolution in CBD media. This study revealed that in the unreduced Clay Fraction half of the total Fe was structural iron (FeStr) in the smectite and half was in goethite. The goethite particles were estimated to be 9 nm in mean crystal diameter (MCD) and to contain 9% Al substituted isomorphously for Fe. An evolution of the different Fe pools and changes in CEC of the mixture were observed. The CEC of SE1089 smectite Fraction sharply increased upon reduction, similar to the SWa-1 reference Clay, even though the FeStr content of SE1089 is much less. Results revealed a correlation of the increase in CEC with FeStr reduction and oxide dissolution, giving a direct connection between the total coating content and the rate of dissolution. For this reason, dissolution kinetics appears to be a key factor in understanding the control of CEC by iron coated material. In particular, in natural media governed by bacterial activity, different dissolution kinetics are expected.