Volume 60 - Issue 3 - June 2012
Article
Influence of Synthesis Conditions on the Formation of a Kaolinitemethanol Complex and Simulation of its Vibrational Spectra
- Jakub Matusik, Eva Scholtzová, Daniel Tunega, Elsa H. Rueda
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- Published online by Cambridge University Press:
- 01 January 2024, pp. 227-239
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Kaolinite is often used as a base for the synthesis of new organo-mineral nanomaterials designed for applications in industry and in environmental protection. To make the mineral structure more likely to interact with organic molecules, a kaolinite-methanol complex (KM) can be used. In the present study, different experimental procedures were tested to investigate the formation of the KM. The kaolinitedimethyl sulfoxide intercalation compound (KDS), either wet or dried, was used as a pre-intercalate. The samples obtained were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, CHNS elemental analysis, 13C CP-magic angle spinning nuclear magnetic resonance (MAS NMR), and 27Al and 29Si MAS NMR techniques. The method of density functional theory with dispersion corrections (DFT-D2) was used to explain the structure and to simulate the vibrational spectra of KM. Theoretical results were compared with experimental data. The most effective formation of the KM (d001 = 11.1 Å — wet; d001 = 8.7 Å — dried) was observed when the dried KDS precursor was used. In such conditions the degree of intercalation reached ~98% after 24 h of reaction time. As indicated by the CHNS elemental analysis, ~1/6 of the inner-surface OH groups were grafted by OCH3 groups. The esterification reaction was less efficient at higher temperatures or when wet KDS was used. In the latter case, the excess of very polar dimethyl sulfoxide molecules prevented intercalation of methanol and further grafting. Detailed analysis of the results of theoretical simulations revealed that the reaction of the KDS with methanol led to the formation of kaolinite with both grafted methoxy groups and intercalated methanol, and water molecules in the interlayer space. The spectra calculated revealed the contribution of individual vibrational modes into the complex bands, i.e. the energy of C-H vibrations was in the order: νasCHmet > νasCHmtx > νsCHmet > νsCHmtx.
Clay Mineralogy of the Zhada Sediments: Evidence for Climatic and Tectonic Evolution Since ~9 Ma in Zhada, Southwestern Tibet
- Hanlie Hong, Chaowen Wang, Kefeng Zeng, Kexin Zhang, Ke Yin, Zhaohui Li
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- Published online by Cambridge University Press:
- 01 January 2024, pp. 240-253
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The clay mineralogy of the Zhada sediments was investigated, using X-ray diffraction and scanning electron microscopy, to obtain a better understanding of climatic change and uplift of the Himalayas in the Zhada region of Tibet. The sediments of Zhada basin in the late Miocene to Pliocene consist of lacustrine and fluvial deposits >800 m thick and can be subdivided into five clay assemblage zones based on their clay-mineral composition. The upward zonation is as follows: (1) smectite-kaolinite; (2) illite-chlorite; (3) chlorite-illite-kaolinite; (4) illite-chlorite; and (5) smectite, illite, and kaolinite. The ratio of chlorite + illite to kaolinite + smectite (Ch+I/K+S) and the Kübler index indicate a warm and humid climate from 9.5 to 8.4 Ma, a cold and dry climate from 8.4 to 7.2 Ma, a warm and seasonal arid climate from 7.2 to 4.5 Ma, a cool and humid climate from 4.5 to 3.6 Ma, and a warm and seasonally humid climate from 3.6 to 3.0 Ma. Intense fluctuations in the Kübler index and in the quantities of evaporite minerals dolomite, aragonite, and gypsum, during the period 7.2–4.5 Ma suggest strong climatic fluctuations between humid and seasonally humid conditions in the Zhada basin. Rapid uplift around the Zhada basin occurred at 8.4 and 3.6 Ma, with sharp subsidence at 7.2 and 4.5 Ma. Evolution of the climate at Zhada showed a different model from that of global climate change, and tectonics-led climate change was the major contributor to climate evolution in the area.
Synthesis and Properties of Sn-Containing Magadiite
- Wojciech Supronowicz, Frank Roessner, Wilhelm Schwieger, Mikhail Meilikhov, Daniel Esken
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- 01 January 2024, pp. 254-264
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Hydrothermal syntheses of the magadiite, a layered silicate structure, were conducted in the presence of a heteroatom source (SnCl4.5H2O) with the intention of investigating its influence on the resulting material, as well as the possibility of isomorphous replacement of Si by Sn atoms in the abovementioned structure. For comparison, unmodified magadiite, Al-containing magadiite, and impregnated magadiite were synthesized. The magadiite structure was identified for samples with Sn/Si ratios up to 0.015. Synthetic methods applied to Sn-modified materials were found to be unsuitable for the introduction of Al. The characterization methods used were X-ray diffraction, temperature-programmed reduction, and 29Si magic angle spinning nuclear magnetic resonance and these revealed the substitution of Si by Sn in the silica layers. No additional acid centers on the surfaces of the modified samples were detected, suggesting the presence of the desired four-coordinate Sn in the silica layers.
Mg-Bentonite in the Parnaíba Paleozoic Basin, Northern Brazil
- Simone Patrícia Aranha da Paz, Rômulo Simões Angélica, Roberto de Freitas Neves
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- 01 January 2024, pp. 265-277
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Bentonite deposits are rare in Brazil and most of their production comes from a single region. A new bentonite occurrence, the Formosa bentonite from northern Brazil, is described here. The occurrence is associated with altered Mesozoic volcanic rocks of the Parnaíba Sedimentary Basin, one of the largest continental flood basalt (CFB) provinces on Earth. The purpose of the present study was to evaluate the physical and chemical properties of a new smectite-bearing deposit in Brazil. Analysis has shown that the major mineral present in the Formosa bentonite is a dioctahedral smectite along with minor amounts of hematite, K-feldspar, and kaolinite. Quartz is absent. A Li+-saturation test (Hofmann-Klemen treatment) revealed a montmorillonite smectite; large interlayer-Mg2+ contents revealed by N2 adsorption/desorption and cation exchange capacity results suggested a Mg-bentonite. This characterization helped to explore the structure-functionality (reactivity) relationship and to develop index tests for industrial applications and the research of new materials.
Use of this material as a desiccant-grade bentonite is envisaged (desiccant-grade bentonites contain Mg2+ and/or Ca2+ as the dominant exchangeable cations), or it could be activated with Na+ for use in many industrial applications (e.g. as a drilling fluid or for pelletizing iron ore). The large areal occurrence of the flood basalts suggests the possibility of very large deposits of these bentonites, a promising new exploration target for this class of industrial minerals in northern Brazil.
Mineralogical and Physico-Chemical Characterizations of Ferruginous Beidellite-Rich Clay from Agadir Basin (Morocco)
- L. Bouna, B. Rhouta, L. Daoudi, F. Maury, M. Amjoud, F. Senocq, M. C. Lafont, A. Jada, A. Aït Aghzzaf
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- Published online by Cambridge University Press:
- 01 January 2024, pp. 278-290
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The mechanism of formation of detrital, beidellite-rich clay occurring in the Agadir basin (Morocco) is well documented, but its detailed characterization is incomplete which limits its application. The aim of the present study was to provide further details of the mineralogical and physico-chemical characteristics of this clay. Bulk raw clay and its Na+-saturated, <2 μm fraction were characterized using chemical, structural, and thermal techniques. Measurements of induced streaming potential (e.g. particle charge) and of specific surface area and porous volume are reported. The raw clay contained carbonate and quartz as associated minerals along with phyllosilicates (<2 μm particle size). X-ray diffraction and scanning electron microscopy analyses showed that the <2 μm fraction was dominated by a dioctahedral smectite. Because dehydroxylation of this mineral occurred at 510°C, and because it re-expanded in ethylene glycol after Li+-saturation followed by heating at 240°C for 24 h, the mineral was shown to be a beidellite rather than montmorillonite. This assertion was further supported by 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectra showing predominantly negative charges in the tetrahedral sheets due to notable Al-for-Si substitutions. The chemical composition of the <2 μm fraction showed an Fe2O3 content which was ~7.52 wt.% greater than those of other beidellite occurrences but not so much that it would be identified as a nontronite. The absence of stretching and bending absorption bands corresponding to characteristic (Fe2OH) units in mid-infrared spectra and their corresponding fundamental overtones or combination bands in near-infrared spectra supported this notion. The structural formula of the beidellite in the present study was determined to be (Si7.51Al0.49)(Al2.99Fe0.68Mg0.33) (Ca0.03Na0.54Mg0.11)O20(OH)4, having dioctahedral ferruginous characteristics with almost 60% of the negative charge found in tetrahedral sheets. The cation exchange capacity determined from the structural formula was ~108 meq/100 g. The specific surface area and total pore volume were ~82.2 m2/g and 0.136 cm3/g, respectively. Interestingly, a detrital rather than a hydrothermal-alteration origin, as reported for other beidellite occurrences, explains its natural abundance and emphasizes the great interest in it.
p-Nitrophenol Electro-Oxidation on a BTMA+-Bentonite-Modified Electrode
- A. Abu Rabi-Stanković, A. Milutinović-Nikolić, N. Jović-Jovičić, P. Banković, M. Žunić, Z. Mojović, D. Jovanović
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- Published online by Cambridge University Press:
- 01 January 2024, pp. 291-299
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Phenol and its derivatives are regarded as ‘priority pollutants’ and p-nitrophenol (p-NP), in particular, is of great interest due to its toxicity and frequent presence in waste waters and fresh waters. Straightforward, inexpensive methods to identify p-NP in water, however, is lacking. In the present study, an electrochemical technique using clay-modified electrodes to measure p-NP was investigated as a potentially promising method to fill that gap. A glassy carbon electrode (GCE) was modified with a thin layer of Na-enriched bentonite and a series of benzyltrimethylammonium (BTMA+)-bentonites (BTMA+-B) in order to confirm these materials as p-NP electrosensitive. A series of organobentonites was synthesized using different BTMA+/bentonite ratios. The materials obtained were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, and a low-temperature nitrogen adsorptiondesorption method. A monolayer arrangement of BTMA+ within the interlamellar region of beidellite-rich smectite was confirmed. Deterioration of the textural properties was observed with increase of BTMA+ loading. The electro-oxidation of p-NP in an acidic medium on BTMA+-B-modified GCE was investigated. The cyclic voltammetry method with a three-electrode cell was used. The reference electrode was Ag/AgCl in 3 M KCl and a Pt foil was the counter electrode. For each electrochemical measurement, a different BTMA+ loading in BTMA+-B was used as the material for GCE coating and applied as the working electrode. The electrochemical activity of BTMA+-B-based electrodes increased with BTMA+ loading. The results confirmed that the organophylic character of the BTMA+-B-modified surface was the main influence on the electrochemical activity of the BTMA+-B-based GCE; the influence of textural properties was almost negligible. The increased electrode activity toward p-NP was achieved by the adsorption of p-NP on the electrode surface, the process that commonly precedes the electro-oxidation. The present study showed that synthesized materials could potentially be used in an electrochemical test for the presence of p-NP in water solutions.
Synthesis, Characterization, and Electrokinetic Properties of Polyindene/Colemanite Conducting Composite
- Berrak Cetin, Halil Ibrahim Unal, Ozlem Erol
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- 01 January 2024, pp. 300-314
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The aim of the aqueous electrokinetic experiments in the present study was to assess the relative contribution of the conducting polyindene (PIn) and inorganic colemanite components to the zeta (ζ) potentials of the composite particles, thus providing further insight into their surface composition in the dispersed state and establishing colloidally stable conditions for potential rheological, industrial applications. For this, PIn and a PIn/colemanite composite (containing 5 wt.% colemanite) were synthesized by chemical oxidative polymerization using FeCl3 as an oxidizing agent. Colemanite, PIn, and PIn/colemanite composite samples were characterized by Fourier-transform infrared spectroscopy, elemental analysis, conductivity, dielectric constant, magnetic susceptibility, density, particle-size measurements, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction analysis, and scanning electron microscopy methods. The electrokinetic properties of colemanite and PIn/colemanite composite dispersions were determined by ζ-potential measurements in aqueous medium, taking into account the effects of time, pH, various electrolytes, surfactants, and temperature. The pH was observed to have a greater effect on the ζ potentials of colemanite in water but caused only slight changes in the presence of cationic (NaCl, BaCl2, AlCl3) and anionic (NaCl, Na2SO4) electrolytes. Increased pH values shifted the ζ potentials of PIn/colemanite composite dispersions to more negative values. The most effective surfactant acting on the ζ potentials of colemanite and PIn/colemanite composite dispersions was cetyltrimethylammonium bromide (CTAB), which shifted the ζ potentials to more positive regions. Elevated temperatures caused almost no change to the ζ potentials of either the colemanite or the PIn/colemanite composite dispersions.
Mineral Preferred Orientation and Microstructure in the Posidonia Shale in Relation to Different Degrees of Thermal Maturity
- Waruntorn Kanitpanyacharoen, Frans B. Kets, Hans-Rudolf Wenk, Richard Wirth
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- 01 January 2024, pp. 315-329
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The thermal maturity of samples of the Posidonia Shale collected from the Hils Syncline, northern Germany, varies significantly as a function of location indicating variations in local history. Synchrotron X-ray diffraction was used to document the composition and the preferred orientation of four samples of the Posidonia Shale with different degrees of maturity (0.68–1.45%, Ro) to determine possible effects on diagenesis and preferred orientation. Overall, the degree of preferred orientation of all clay minerals (illite-smectite, illite-mica, and kaolinite) and in all samples is similar, with (001) pole figure maxima ranging from 3.7 to 6.3 multiples of a random distribution (m.r.d.). Calcite displays weak preferred orientation, with c axes perpendicular to the bedding plane (1.1–1.3 m.r.d.). Other constituent phases such as quartz, feldspars, and pyrite have a random orientation distribution. The difference in thermal history, which causes significant changes in the maturity of organic matter, influenced the preferred orientation of clay minerals only marginally as most of the alignment seems to have evolved early in their history. Synchrotron X-ray microtomography was used to characterize the three-dimensional microstructure of a high-maturity sample. Low-density features, including porosity, fractures, and kerogen, were observed to be elongated and aligned roughly parallel to the bedding plane. The volume of low-density features was estimated to be ~7 vol.%, consistent with previous petrophysical measurements of porosity of 8–10 vol.%. Transmission electron microscopy analysis of samples with different degrees of maturity (0.74%Ro and 1.45%Ro) was used to document microstructures at the nanoscale as well as the presence of kerogen. In the high-maturity sample, pores were less abundant while minerals were more deformed as shown by fractured calcite and by kinked and folded illite. Some of the porosity was aligned with clay platelets.
Effects of Mg, Ca, and Fe(II) Doping on the Kaolinite (001) Surface with H2O Adsorption
- Man-Chao He, Jian Zhao
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- 01 January 2024, pp. 330-337
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Kaolinite is often a cause of deformation in soft-rock tunnel engineering, leading to safety problems. The mechanism of the deformation is closely related to the interaction between kaolinite and water molecules. Because kaolinite has multiple defects, the effects of Mg, Ca, and Fe(II) doping on the atomic structure of the kaolinite (001) surface, and the subsequent adsorption and penetration of H2O into the interlayer, were studied systematically using density-functional theory. The results showed that for the Mg-, Ca-, and Fe(II)-doped kaolinites (001), the surface relaxation around the doping layer changed from contraction to expansion, due to the redistribution of electrons. The adsorption energies of the H2O monomer on Mg-, Ca-, and Fe(II)-doped kaolinites (001) were less than on undoped kaolinite (001). The results further revealed that the H2O molecule can also adsorb on the hollow site on the second-layer O surface of the Mg-, Ca-, and Fe(II)-doped kaolinites (001). For the undoped kaolinite, however, the H2O molecule adsorbs on the surface only. The energetic barriers for penetration of H2O from the adsorption site on the surface to the adsorption site on the O surface of Mg-, Ca-, and Fe(II)-doped kaolinites were also calculated: 1.18 eV, 1.07 eV, and 1.41 eV, respectively. The results imply that the influences of Mg, Ca, and Fe(II) doping on kaolinite allow the adsorbed water molecules to penetrate from the on-surface adsorption site to the O-surface site.
Sridhar Komarneni: 2011 Recipient of the Marilyn And Sturges W. Bailey Distinguished Member Award
- Prakash B. Malla
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- Published online by Cambridge University Press:
- 01 January 2024, pp. 338-339
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