Showing papers in "Clay science in 2006"
TL;DR: In this article, 39 samples were analyzed and classified into four groups based on their properties: coefficient of linear extensibility (COLE), pH, cation exchange capacity (CEC), organic carbon, microbial content and x-ray diffraction (XRD) spacings.
Abstract: Smectite clay has been shown to sorb aflatoxin B1 (AfB1) in animal feed 2) and thereby reduce its toxic influence on animals and its entrance to the human food chain. In an effort to find effective adsorbents, 39 samples proposed to adsorb aflatoxin were analyzed and classified into four groups based on their properties: coefficient of linear extensibility (COLE), pH, cation exchange capacity (CEC), organic carbon, microbial content and x-ray diffraction (XRD) spacings. A subset of 20 bentonite samples from commercial sources and reference minerals from 6 US-states and 2 sites in Mexico was selected for sorption determinations. A 10-fold difference in sorption based on the Langmuir equation was observed. Yet clay properties were mostly clustered and it is not clear which properties influence this variation. The basal spacing of AfB1 saturated smectites exhibited greater resistance to collapse on heating than untreated smectites indicating that AfB1 entered the interlayer galleries of the smectites. After heating the mycotoxin-clay complex the desorbed mycotoxin was altered indicating a reaction of the molecules with the clay surface. The most effective sorbent smectite samples were from three US-states (MS, ID, TX).
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TL;DR: In this article, low levels of mixed layering of smectite were observed in the kaolinite and illite phases using synchrotron x-ray diffraction, in addition, heavy minerals undetectable using a laboratory rotating anode xray source.
Abstract: Conventional laboratory x-ray diffraction techniques are generally used to characterize minerals in oil sand ores and other extraction process streams and can usually provide mineralogical insight into reasons for poor processability. Often, however, a greater level of detail is required to quantify low levels of mixed layering in clay minerals and the multitude of non-clay minerals in the ores. The more intense x-ray sources available at synchrotrons with their inherent high resolution and tunable wavelength can often help in providing this level of detail. In addition, x-ray microscopy can help to characterize the organic contaminants that commonly affect clay behaviour in industrial processes. In this study, low levels of mixed layering of smectite were observed in the kaolinite and illite phases using synchrotron x-ray diffraction, in addition to heavy minerals undetectable using a laboratory rotating anode x-ray source. Using scanning transmission x-ray microscopy, the speciation of carbon components adsorbed on clay minerals after bitumen extraction suggests a preferential affinity of the clay minerals for high-molecular-weight aromatics in bitumen.
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TL;DR: Sauconites were synthesized hydrothermally from a homogeneous gel with stoichiometric chemical composition in a temperature range of 100-200°C for up to 14 d at autogenous pressure.
Abstract: Sauconites were synthesized hydrothermally from a homogeneous gel with stoichiometric chemical composition in a temperature range of 100-200°C for up to 14 d at autogenous pressure The synthetic products were characterized by XRD, SEM, TEM, ICP-AES, FT-IR and XPS The well-crystallized sauconite without impurities was obtained after 100°C treatment At 150 and 200°C, sauconite coexisted with small amount of hemimorphite (Zn 4 Si 2 O 7 (OH) 2 H 2 0) and willemite (Zn 2 SiO 4 ) The octahedral coordination of Zn in synthesized sauconite was confirmed by FT-IR and XPS spectra, comparing with those of natural mica containing Zn in the octahedral layer (hendricksite) The FT-IR spectra of synthetic sauconite showed the characteristic bands at 660 cm -1 for Zn-O vibration and 3635 cm -1 for 3Zn-OH stretching in the octahedral sheets, which are comparable to those of hendricksite The Zn(3p) peak of sauconite in XPS spectrum was observed which corresponded with that of hendricksite These results indicated that Zn in sauconite was coordinated octahedrally as Zn in hendricksite
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TL;DR: The results are consistent with the epidemiological reports indicating mesothelioma can develop in individuals with exposures to riebeckite (crocidolite) asbestos described as brief and/or slight.
Abstract: This report focuses on identifying the important asbestos fiber- type(s) in the etiology of the asbestos-related cancer mesothelioma. In the last century all three of the commercial fiber types grunerite (amosite) asbestos, chrysotile asbestos and riebeckite (crocidolite) asbestos- were mined, milled and used to fabricate asbestos-containing products in South Afiica. The cases are a consecutive series of occupational and environmental mesotheliomas referred to South Afiica's National Institute for Occupational Health. The authors recovered the inorganic particles from the lung parenchyma in 43 human mesothelioma cases and used analytical transmission electron microscopy to determine the types and concentrations of fibrous minerals present. The predominant, often the only asbestos fiber-type, found in the pulmonary tissues was riebeckite (crocidolite) asbestos. The highest concentration of riebeckite (crocidolite) asbestos found was 10,500,000 fibers per gram of dned lung tissue. The mean concentration was 0.27 million fibers per gram of dned lung tissue which is between 4 to 59-fold below the concentration of chrysotile asbestos in general population where asbestos is found without asbestos-related disease. The results are consistent with the epidemiological reports indicating mesothelioma can develop in individuals with exposures to riebeckite (crocidolite) asbestos described as brief and/or slight.
TL;DR: A comparative study on the intercalation of the hexadecyltrimethylammonium (C16TMA) cations into two montmorillonites with different cation exchange capacity (CEC) values, is reported in this paper.
Abstract: A comparative study on the intercalation of the hexadecyltrimethylammonium (C16TMA) cations into two montmorillonites with different cation exchange capacity (CEC) values, is reported. The effect of selected counterions (Br-, Cland OH-) on the adsorption of C16TMA was investigated. The aim of this study is to gain further insight into the influence of the type of surfactant solutions and the physicochemical properties of raw clays on their intercalation behaviors. The intercalated amounts depended on the CEC values of the starting clays and the type of C16TMA solutions. The content of surfactants was higher in the raw clay with higher CEC, and followed the trend C16TMABr>C16TMACl>C16TMAOH. The expansion of the basal distance in the range of 1.8nm to 3.7 nm, was related to the starting raw clay and to the starting concentrations of bromide and chloride surfactant solutions. However, the interlayer spacing was almost independent of the starting raw clay-and the concentrations of C16TMA hydroxide solution, related to a difficult swelling behavior of clay sheets in basic solutions.
TL;DR: In this article, the ion exchange reactions of Na-magadiite with metal cations such as H+, K+, Mg2+, Ca2+, Sr2+, Ba2+, Cu2+ and Zn2+ were studied in an aqueous medium.
Abstract: The ion-exchange reactions of Na-magadiite with metal cations such as H+, K+, Mg2+, Ca2+, Sr2+, Ba2+, Cu2+ and Zn2+ were studied in an aqueous medium. The H+ ion and all divalent metal ions except Mg2+ exchanged with Na+ in an aqueous solution with a stoichiometric amount of the metal ion. K+ and Mg2+ showed poor reactivity with the Na-magadiite. Na+ was not fully replaced even with a K+ or Mg2+ concentration that was 100 times the Na+ concentration. The pH dependence of Cu2+ for the ion-exchange reaction was different from that of other metal ions. XRD analysis revealed that the structure of the Na-magadiite differed from the Cuor H-magadiite. These differences arose from structural changes in the silicate sheet due to the H+ or Cu2+ adopting a different geometry in interaction with the oxygen atoms in the silicate sheet. Ethylene diamine (en) and pentaethylene hexamine (pentaen) react with Cu2+ to form stable cationic complexes: Cu(en)2, which has a planar structure, and Cu(pentaen), which has an octahedral structure. The XRD patterns all revealed a difference between the basal spacings of the metal-magadiite and the sum of the crystalline ionic diameter of the metal and basal spacing of the H-magadiite. Na remained in the interlayer of the magadiite in the presence of excess complexes. The degree of dehydration of the metal cation depends on the ion-exchange reactivity of the magadiite.
TL;DR: In this article, the authors observed the aqueous suspension of kGa-1 kaolinite from Birdwood (South Australia) and Georgia (USA) and found that most particles have edge-to-face (EF) contacts building cardhouse structure.
Abstract: SEM observation of the aqueous suspension of kaolinite from Birdwood (South Australia) and Georgia (USA) show noticeable differences in microstructure. Birdwood kaolinite dispersion gels at very low solid loadings in comparison with Georgia KGa-1 kaolinite dispersion which remains fluid at higher solids loading. To explain this behaviour, particle interactions in the colloidal size fraction of Birdwood kaolinite have been proposed. These interactions may be brought about by the presence of nano-bubbles on clay crystal edges and may force clay particles to aggregate by bubble coalescence. This may explain the predominance of edge-edge (EE) contacts in suspension of Birdwood kaolinite. Such mostly EE linked particles build long strings that form a spacious cell structure. Hydrocarbon contamination of colloidal kaolinite particles and poor crystallisation are discussed as possible explanation of the unusual behaviour of Birdwood kaolinite. In Georgia KGa-1 kaolinite dispersions instead of EE contact between platelets displayed in Birdwood kaolinite, most particles have edge to face (EF) contacts building cardhouse structure. Such an arrangement is much less voluminous in comparison with the Birdwood kaolinite cellular honeycomb structure observed before in smectite aqueous suspensions. Such structural characteristics of KGa-1 kaolinite particles enables higher solid volume fractions pulps to form before significantly networked gel consistency is attained.
TL;DR: In this paper, the effect of sample temperature on the CL intensity of kaolinite and dickite can not be interpreted on the basis of a temperature quenching theory; however, it is rather a possibility of applying TL of sepiolite to the dating.
Abstract: Cathodoluminescence (CL) measurements of clay minerals were performed at both room temperature and low temperature. Panchromatic CL images of kaolinite and dickite show blue emission at room temperature. Their CL spectra exhibit an intense broad band peak at around 375 nm. This emission band related to radiation induced defect centers (RID) disappears at low temperature. Effect of sample temperature on CL intensity of kaolinite and dickite can not be interpreted on the basis of a temperature quenching theory. In halloysite, serpentine minerals, sericite and sepiolite, the intensity of a broad band between 400 and 450 nm is higher at low temperature than at room temperature. CL spectra of serpentine minerals are characterized by a broad band centered at 720 nm, which can be assigned to Fe 3+ impurity center. Natural TL glow curve of sepiolite presents two glow peaks around at 210 and 260°C in the high temperature region, of which intensities are weak. This implies that it is rather a possibility of applying TL of sepiolite to the dating. The other minerals show no emission in natural TL measurements. X-ray induced TL of kaolin minerals exhibit intense several TL glow peaks below room temperature. Serpentine minerals have glow curves with a relative large peak between 70 and 90°C. Sericite, montmorillonite and sepiolite show a combination of emission peaks in their TL glow curves, while their intensities are weak compared to kaolin and serpentine minerals. Clay minerals might have characteristic TL related to their crystal structure.
TL;DR: In this article, a nano-scale aluminum germanate tubular material with a similar structure of clay mineral imogolite was synthesized from a concentrated inorganic solution using GeO 2 dissolved in NaOH as the source of germanium.
Abstract: We synthesized a nano-scale aluminum germanate tubular material with a similar structure of clay mineral imogolite. This nano-tubular material can be obtained from a concentrated inorganic solution using GeO 2 dissolved in NaOH as the source of germanium. The IR spectrum, powder X-ray diffraction profile and TEM image are similar to those of previously reported aluminum germanate tubular material prepared using GeCl 4 . Tapping mode atomic force microscopy revealed that our novel material had tubes which were shorter in length and wider in diameter than those of synthetic imogolite.
TL;DR: In this article, the tabular-like inclusions correspond to APS (aluminium phosphate sulphate) minerals, such as florencite, formed at early stages before alunite crystallization from a solution with a high phosphorous/sulphur ratio.
Abstract: Chemical bulk analyses of intermediate alunite-natroalunite minerals indicate anomalous high contents of REE, Sr, Ba, Ca and P. Alunite occurs as veinlets or nodules cross-cutting hydrothermal clay deposits, containing pyrophyllite, kaolinite and sericite in the west Barker area (Dristas & Frisicale 1983(5), 1992(6)). Petrographic studies reveal a pseudocubic habit for the alunite. No significant zoning has been detected in this mineral by EPMA backscattered images. Additionally, EPMA and EDX studies indicate that the tabular-like inclusions in cores of alunite contain significant amounts of P, Ba, Sr, REE, Ca and Fe. Alunite shows epitaxial growth on the inclusion mineral. These tabular-like inclusions correspond to APS (aluminium phosphate sulphate) minerals, such as florencite, formed at early stages before alunite crystallization from a solution with a high phosphorous/sulphur ratio. The crystal structure of APS minerals are suitable for REE, Sr and Ba substitution since metal cations are situated in large cavities formed by 6-membered rings of M(O, OH)6 octahedra. A later increase of solution sulfurization would favor the formation of alunite that constrained the REE, P, Sr, Fe, Ca and Ba fixation.
TL;DR: In this paper, the diffision of water in weakly-hydrated samples of the smectite clay Na-fluorohectorite was studied, where the quasi-one-dimensional samples are dry compounds of nano-layered particles consisting of 80 silicate platelets.
Abstract: We study the diffision of water in weakly-hydrated samples of the smectite clay Na-fluorohectorite, The quasi one-dimensional samples are dry compounds of nano-layered particles consisting of 80 silicate platelets. Water diffises into a sample through the mesoporosity in between the particles, and can subsequently intercalate into the adjacent particles. The samples are placed under controlled temperature. They are initially under low humidity conditions, with all particles in a 1 WZ, intercalation state, We then impose a high humidity at one sample end, triggering water penetration along the sample length. We monitor the progression of the humidity front by monitoring the intercalation state of the particles in space and time. This is done by determining the characteristic spacing of the nano-layered particles in situ, from synchrotron wide-angle X-ray scattering measurements. The spatial width of the intercalation front is observed to be smaller than 2mm, while its velocity decreases with time, as expected from a diffusion process,
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