BASELINE STUDIES OF THE CLAY MINERALS SOCIETY SOURCE CLAYS BY X-RAY PHOTOELECTRON SPECTROSCOPY (original) (raw)
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Layered clay systems intercalated with inorganic and organic compounds were analyzed to highlight how XPS can provide information on the different environments surrounding a particular atom as well as provide discernments on the size, coordination, and structural and oxidative transformations of the intercalating/pillaring compounds. XPS data on the intercalation of urea and K-acetate in low- and high-defect kaolinite revealed the interaction of the intercalating group NH2 with the siloxane functional groups in the interlayer surface. The intercalation of HDTMA in Mt demonstrated the use of XPS in monitoring the change in conformation assumed by alkylammonium intercalating compounds in Mt with increasing CEC. Studies on the pillaring of Mt by Al13 and Ga13 by XPS allowed determination of the coordination of the pillaring compound within the Mt layer. Lastly, the intercalation of hexacyanoferrate in hydrotalcite demonstrated the capability of XPS in following changes in the oxidation state of the iron compound. These were gleaned from interpretation of the shifts in binding energies and presence of multiplet splitting in the XPS of the component elements of the minerals or the intercalating compounds.
The application of X-ray photoelectron spectroscopy to clay science
Photo-electron spectroscopy as an analytical tool has only received limited interest in the field of mineral science. Photo-electron spectroscopy, together with Auger electron spectroscopy, gives information about the positions of the energy levels in atoms or molecules. Application of this technique on solid materials will result in information of the band structure of these materials. The principle of photo electron spectroscopy is rather simple: photons with certain energy (wavelength) are allowed to collide with an atom, molecule or a solid material. These photons can then interact with electrons present in the atoms and one of these electrons can be excited from its orbital resulting in a situation similar to a free electron plus a positively charged atom or molecule.
Clay Mineralogy: Spectroscopic and Chemical Determinative Methods
Journal of Environmental Quality, 1995
Of the determinative methods used to study clay minerals, chemical analysis is the oldest and most established. Before the development of the earliest instrumental techniques, such as X-ray diffraction and thermal methods, the identification of clay-mineral phases was accomplished by chemical analysis, supplemented where possible by optical data and physical characteristics such as specific gravity, colour, hardness, etc. However, fine-grained materials cannot be characterized reliably using these methods alone, and misidentifications were common. With the routine application of infrared spectroscopy and electron microscopy, in addition to X-ray diffraction and thermal analysis, instrumental techniques are now unquestionably superior to chemical analysis for clay-mineral identification and a clay is often described and identified without recourse to chemical analysis. Nevertheless, for complete characterization, a chemical analysis is still essential, as this is the only way that a structural formula can be calculated and the distribution of cations in the structure defined directly. A full characterization should include the determination of all the major and minor elements (with the proportion of the iron present in the ferrous and ferric forms) and also the determination of the cation-exchange capacity and, if possible, the anion-exchange capacity. Classification of clay minerals has always depended heavily on chemical data, and many clay-mineral groups, such as smectites, illites and chlorites, are subdivided according to composition. The characterization of a clay mineral as 'dioctahedral' or 'trioctahedral' can be determined from a b-dimension measurement using X-ray or electron-diffraction techniques, but these terms also have a chemical connotation, indicating the valency of the cations occupying the octahedral sheets. The type and Clay Mineralogy: Spectroscopic and Chemical Determinative Methods.
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Intech Open, 2021
Clay minerals such as kaolinite, smectite, chlorite, micas are main components of raw materials of clay and formed in presence of water. A large number of clays used to form the different structure which completely depends on their mining source. They are known as hydrous phyllosilicate having silica, alumina and water with variable amount of inorganic ions like Mg 2+ , Na + , Ca 2+ which are found either in interlayer space or on the planetary surface. Clay minerals are described by presence of two-dimensional sheets, tetrahedral (SiO 4) and octahedral (Al 2 O 3). There are different clay minerals which are categorized based on presence of tetrahedral and octahedral layer in their structure like kaolinite (1:1 of tetrahedral and octahedral layers), smectite group of clay minerals (2:1 of tetrahedral and octahedral layers) and chlorite (2:1:1 of tetrahedral, octahedral and octahedral layers). The particle size of clay minerals is <2microns which can be present in form of plastic in presence of water and solidified when dried. The small size and their distinctive crystal structure make clay minerals very special with their unique properties including high cation exchange capacity, swelling behavior, specific surface area, adsorption capacity, etc. which are described in this chapter. Due to all these unique properties, clay minerals are gaining interest in different fields.
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A qualitative chemical analysjs ofthree reference clay minerals, Mikawa montmorillonitc, synthetic saponite and Naheyarna illite, was performed using a recently developed TEM-EDS setup built around a microcalorimeter device that has a very high encrgy resolution, The spectrum obtained by the microcalorimeter EDS showed the srnall peaks of minor elements present in thcse clay minerals. It was also used to detect the SK6 pealc in sapenite and the SiKB' peak in montmorillonite and saponite whereas by eonventional Si(Li) EDS, these peaks disappearcd er overlappcd. Micrecalorimeter EDS with TEM providcd us with valuable elemental data of clay minerals in this study, and will considerably contribute to the progress ef the study of clay millerals.
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The levels of trace elements concentration of the clay minerals of Pakistan have been determined. Inductively Coupled Plasma (ICP) spectrometer was used for the determination of trace elements. The samples of the clay minerals were digested in the ETHOS microwave oven at 180 ′ 5°C. The trace elements (As, Co, Cu, Cr, Cd, Fe, Mn, Ni, Pb, Se and Zn) in the clay minerals of Pakistan fall within the global range. Except as all the trace elements fall within the technical specification of the medicinal clay. The chemical analysis also shows that (SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, MgO, Na 2 O, and K 2 O) these are within the technical specification of the medicinal clay. Therefore, at present they can be used for external use only. The trace elements (As, Co, Cu, Cr, Cd, Fe, Mn, Ni, Pb, Se and Zn) of clay mineral as well as the activated clay minerals were determined and it is observed that during activation Na, K and Ca ions are leached out. The presence of trace elements of transition ...
Semina: Ciências Exatas e Tecnológicas, 2009
Two Energy Dispersive X-ray Fluorescence equipments have been compared in order to verify its performance for clay characterization and potential application to the study in archaeometric field and industry. Two clay standard reference materials (SRM), IPT-42 and IPT-51 and one IAEA intercomparison sample were analyzed by two different methodologies and equipments. Asentamiento Universitario Zapala laboratory has a Shimadzu EDX-800HS bench top equipment and 13 elements from S to Zr were quantified in the standards. Applied Nuclear Physics Laboratory has a portable EDXRF system. It was possible to quantify K, Ti and Fe and qualitatively to identify Mn, Rb, Zn and Zr.
Quantitative X-ray diffraction analysis of clay-bearing rocks from random preparations
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An internal standard X-ray diffraction (XRD) analysis technique permits reproducible and accurate calculation of the mineral contents of rocks, including the major clay mineral families: Fe-rich chlorites + berthierine, Mg-rich chlorites, Fe-rich dioctahedral 2:1 clays and micas, Al-rich dioctahedral 2:1 clays and micas, and kaolinites. A single XRD pattern from an air-dried random specimen is used. Clays are quantified from their 060 reflections which are well resolved and insensitive to structural defects. Zincite is used as the internal standard instead of corundum, because its reflections are more conveniently located and stronger, allowing for a smaller amount of spike (10%). The grinding technique used produces powders free of grains coarser than 20 ixm and suitable for obtaining random and rigid specimens.