The origin of the pozzolanic activity of calcined clay minerals: A comparison between kaolinite, illite and montmorillonite

This paper investigates the decomposition of three clayey structures (kaolinite, illite and montmorillonite) when thermally treated at 600 °C and 800 °C and the effect of this treatment on their pozzolanic activity in cementitious materials. Raw and calcined clay minerals were characterized by the XRF, XRD, ²⁷Al NMR, DTG and BET techniques. Cement pastes and mortars were produced with a 30% substitution by calcined clay minerals. The pozzolanic activity and the degree of hydration of the clinker component were monitored on pastes using DTG and BSE-IA, respectively. Compressive strength and sorptivity properties were assessed on standard mortars. It was shown that kaolinite, due to the amount and location of OH groups in its structure, has a different decomposition process than illite or montmorillonite, which results in an important loss of crystallinity. This explains its enhanced pozzolanic activity compared to other calcined clay–cement blends.     

Polymer–montmorillonite clay nanocomposites. Part 1: Complexation of montmorillonite clay with a vinyl monomer

An organo‐clay complex was formed by the exchange reaction of a quaternary ammonium salt of a derivatized styrene monomer with Na⁺‐montmorillonite clay. The binding of the derivatized styrene monomer with the montmorillonite clay was confirmed by FTIR and the diffused reflectance analysis. The increase of the d‐spacing of the derivatized styrene‐N⁺–montmorillonite clay complex to 1.47 nm, measured by X‐ray diffraction, indicates that a monolayer of the monomer is adsorbed between adjacent montmorillonite layers. A molecular modeling of the monomer suggested a benzene ring tilted to the c‐axis of the montmorillonite clay. The carbon content of the styrene‐N⁺–montmorillonite clay of 11.02 % suggested a complete surface coverage of the clay by the monomer and a surface coverage of 0.74 nm² per exchange site of the montmorillonite. Copyright © 2004 Society of Chemical Industry     

Rates of low-temperature dehydration of montmorillonite and illite

The kinetics of the isothermal dehydration of the clay minerals, montmorillonite and illite, were studied in vacuo as well as in the presence of a constant water vapour pressure. The dehydration followed a first-order law, and the presence of water vapour led to (i) an increase in the extent of dehydration, compared with that in vacuo; (ii) a retardation to the rate of dehydration; and (iii) a great increase in the energy of activation required for the dehydration. Dehydration in vacuo appears to be diffusion-controlled with an activation energy of 2–4 kcal/mole, whereas the desorption of water appears to control dehydration in the presence of water vapour, with an activation energy of 12–15 kcal/mole. The results are discussed in conjunction with the mechanical contraction of the layer structure, and the introduction of diffusion barriers when dehydration in vacuo takes place.     

High-pressure adsorption of methane on montmorillonite,kaolinite and illite

Methane (CH₄) adsorption of Ca^2 +-montmorillonite (Mt), kaolinite (Kaol) and illite (Il) at 60 °C and pressures up to 18.0 MPa was investigated, during which the adsorption capacity was evaluated by the Langmuir adsorption model. The influences of adsorbed water and the interlayer distance of the clay minerals on CH₄ adsorption were explored by using heated Mt products with different interlayer distances as the adsorbent. Mt, Kaol and Il showed high CH₄ adsorption capacities, and their maximum Langmuir adsorption capacities were Mt, 6.01 cm³/g; Kaol, 3.88 cm³/g; and Il, 2.22 cm³/g, respectively. CH₄ was adsorbed only on the external surface of Kaol and Il; however, adsorption also occurred in the interlayer space of Mt, which had a larger interlayer distance than the size of a CH₄ molecule (0.38 nm). CH₄ adsorption in the interlayer space of Mt was supported by the lower CH₄ adsorption capacity of heated Mt products (with the interlayer distance < 0.38 nm) than that of Mt at high pressures despite the higher external surface areas of the heated Mt samples. The entrance of CH₄ into the interlayer space of Mt occurred at low pressures, and more CH₄ molecules entered the interlayer space at high pressures. Moreover, the adsorbed water occupied the adsorption sites of the clay minerals and decreased the CH₄ adsorption capacity. These results indicate that clay minerals play a significant role in CH₄ adsorption of shale and indicate that the structure and surface properties of clay minerals are the important parameters for estimating the gas storage capacity of shale.     

Preparation and evaluation of nanocomposites of polyfuran with Al2O3 and montmorillonite clay

High yield oxidative polymerization of furan was accomplished in CHCl₃ solvent at 0 °C. A nanocomposite of polyfuran (PF)–Al₂O₃ was prepared through polymerization of furan in a suspension of nanodimensional Al₂O₃ in CHCl₃ at 0 °C. High yield polymerization of furan was also achieved in montmorillonite clay (MMT) without any extraneous oxidant. The formation of PF was confirmed by FTIR and elemental analysis. Thermogravimetric analyses revealed the following trends in thermal stability: PF < PF–Al₂O₃ < Al₂O₃ and PF < PF–MMT < MMT. Scanning electron microscopy showed the average particles sizes to be ca 51 nm and ca 40 nm for PF–Al₂O₃ and PF–MMT composites, respectively. The occurrence of a peak at 19.84 Å in the X‐ray diffraction pattern of the PF–MMT composite was indicative of the intercalation of PF in MMT lamellae. Transmission electron microscopic analyses for the PF–MMT composite also showed incorporation of PF moieties in‐between the MMT layers. The dc conductivity values (S cm^?1) of PF–FeCl₃, PF–Al₂O₃–FeCl₃, PF–MMT and PF–MMT–FeCl₃ systems were in the order of 10^?6, 10^?7, 10^?8 and 10^?7, respectively, and the values were significantly enhanced compared to the dc conductivity value of PF homopolymers (10^?11). Copyright © 2004 Society of Chemical Industry     

Thermal and chemical treatments of montmorillonite clay

Montmorillonite clay from a natural deposit was processed to remove impurities and later submitted for thermal and chemical treatments. The sample was first subjected to a thermal treatment at 400 °C, for 1 h, to remove organic components. The chemical treatment was conducted first by using an acid attack with nitric acid and sulfuric acid, then, adding sodium acetate in ethylene glycol clay dispersion, and finally the clay was dispersed in xylene with subsequent addition of silane, N-(b-aminoethyl)-g-aminopropyiltrimethylsilane. The combined thermal and chemical treatment was found to have a significant effect on the final chemical composition of the nanoclay. X-ray diffraction patterns suggested that the combined thermal and chemical treatment resulted in increased interplanar distances, thus favoring exfoliation of the clay lamellae, which was also confirmed by SEM images. Fourier transform infrared (FTIR) spectroscopy analysis suggested that the combined thermal and chemical treatment resulted in removal of water from the montmorillonite, without any modification or destruction of the clay structure. Thus, the combination of thermal and chemical treatments proposed in this work may be a promising approach to process montmorillonite intended for the production of advanced materials.     

Solid acidity of 2 : 1 type clay minerals activated by selective leaching

Various 2 : 1 type clay minerals were activated by H₂SO₄ treatment and their solid acidities were evaluated by NH₃-temperature programmed desorption (TPD). Clay minerals with various degrees of Al substitution in the tetrahedral sheets were used as the starting materials. These included montmorillonite (ideally no tetrahedral Al), saponite (low content of tetrahedral Al), vermiculite (intermediate content of tetrahedral Al) and phlogopite (high tetrahedral Al content). All these samples showed increased solid acidity after selective leaching, the solid acidities varying in the order phlogopite < montmorillonite < vermiculite < saponite. The NH₃-TPD spectra were deconvoluted into two peaks; the L-peak at < 200 °C corresponds to a weak acid site and the H-peak at > 250 °C corresponds to a strong acid site. The temperature of the H-peak was lowest in phlogopite (252 °C) and highest in saponite (305 °C). The generation of solid acidity in these samples is found to be related to the evolution of new tetrahedral Al sites showing a slightly different ²⁷Al MAS NMR chemical shift from the original tetrahedral Al NMR resonance.     

Epoxy‐montmorillonite clay nanocomposites: Synthesis and characterization

Nanocomposites of epoxy resin with montmorillonite clay were synthesized by swelling of different proportions of the clay in a diglycidyl ether of bisphenol‐A followed by in situ polymerization with aromatic diamine as a curing agent. The montmorillonite was modified with octadecylamine and made organophilic. The organoclay was found to be intercalated easily by incorporation of the epoxy precursor and the clay galleries were simultaneously expanded. However, Na‐montmorillonite clay could not be intercalated during the mixing or through the curing process. Curing temperature was found to provide a balance between the reaction rate of the epoxy precursor and the diffusion rate of the curing agent into the clay galleries. The cure kinetics were studied by differential scanning calorimetry. The exfoliation behavior of the organoclay system was investigated by X‐ray diffraction. Thermogravimetric analysis was used to determine the thermal stability, which was correlated with the ionic exchange between the organic species and the silicate layers. The morphology of the nanocomposites was evaluated by scanning electron microscopy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2201–2210, 2004     

Bleaching of alkali-refined vegetable oils with clay minerals

Bleaching efficiencies of bentonites, montmorillonites and sepiolites for alkali-refined rapesseed, soybean, wheatgerm, safflower, corn, cottonseed and sunflower oils were investigated by a batch method at 110°C. The sepiolites with more acid sites at −5.6 < H_o ≥ −3.0 were the most effective in bleaching of each alkali-refined oil. Surface area and acidity at −5.6>H_o ≥ −3.0 were highly significant with bleaching efficiency. The sepiolites (numbers 2 and 3) were more suitable than standard activated clay because they were more effective both in retaining tocopherols and in reducing free fatty acids after bleaching.     

Moisture diffusion through vinyl ester nanocomposites made with montmorillonite clay

Moisture diffusion was studied through vinyl ester samples containing up to 5 wt% of organically treated montmorillonite. Two different kinds of clay surface treatment were employed to make the clay compatible with Derakane^TM 411‐350 vinyl ester resin. The nanocomposites were characterized using differential scanning calorimetry (DSC), mechanical property measurements, X‐ray diffraction (XRD) and transmission electron microscopy (TEM). TEM pictures showed that the clay platelets were either exfoliated or intercalated, and the two different surface treatments resulted in different dispersion characteristics. All the samples were post cured, and the diffusivity of moisture was measured by soaking the samples in 25°C water and noting the increase in weight with increasing time of immersion. It was found that water diffusivity decreased with increasing clay content, and it was reduced to half its value in the neat resin when the clay content was only 1 wt% regardless of the nature of clay surface treatment. However, the equilibrium moisture content, the glass transition temperature, and the elastic modulus all increased with increasing amounts of clay.     

Tritium redistribution between water and clay minerals

Hydrogen-isotope exchange between clay minerals and tritiated water was studied with kaolinite, montmorillonite and palygorskite. At all possible positions, tritium accumulated most intensively during the initial stage (10 to 20 days) but further increase of tritium concentration in experimental systems was much less intensive. Interaction of tritiated water with clay minerals decreased in a similar manner. In all samples, the highest amounts of tritium atoms and the maximum accumulation rates (V) were observed in the surface-adsorbed water (V_surf) over the complete study period. The modes of tritium accumulation in the interlayer space (montmorillonite) and in the channels (palygorskite) (V_inter) are quite similar and both types of structures are very suitable for hydrogen-isotope exchange. Availability of well-developed paths for the access of T⁺ ions to structural OH-groups (V_struct) enables intense tritium accumulation at these positions in montmorillonite and palygorskite (V_inter  V_struct). In kaolinite the access of T⁺ ions to structural OH-groups is more difficult, in spite of the considerable number of potential exchange positions in its structure, therefore resulting in lower tritium adsorption in comparison with the other two clay minerals.     

Formation of high-temperature crystalline phases in ceramic from illite clay and dolomite

The formation of ceramic with the prevailing cordierite/mullite in the crystalline phase is greatly dependent on the raw materials used. In the present work the cordierite and mullite (or their solid—solutions accordingly with spinels and corundum) formation processes from compositions of natural raw materials (illite clay, dolomite) with synthetic additives (MgO, Al(OH)₃, K₂CO₃) are studied. It is shown that the illite clay acts as a low viscosity liquid medium as well as a precursor for cordierite and mullite crystallisation in ceramics.The phase development using XRD—analysis and the SEM is studied. Particles size distribution of staiting powder and some properties of ceramic obtained are also demonstrated. It is shown that formation of the above mentioned phases starts at temperatures 1050–1080 °C and remarkably increases at 1200 °C for mullite and at 1300 °C for cordierite.     

Bleaching with alternative layered minerals: A comparison with acid-activated montmorillonite for bleaching soybean oil

An extensive series of layered minerals including montmorillonite was studied to determine if the fundamental physicochemical properties responsible for pigment adsorption could be identified. Samples were subjected to a uniform preparation regimen to eliminate such secondary effects as particle size, moisture content, level of activation and degree of washing. By doing so, it has been possible to show that both carotene and chlorophyll adsorptions can be described by a rather simple model that employs both surface acidity and pore volume as key variables. Further, it was found that this model provides an adequate fit to the actual data only when specific regions for these variables are considered (i.e., concentration of sites of strong surface acidity, not just total surface acidity; pore volume in region 50\s-200 Å, not just total pore volume). Presented at the AOCS meeting in New Orleans, LA in May 1987.     

黏土类矿物合成多孔分子筛的研究进展

综述了以黏土类矿物合成沸石分子筛的特点,分别介绍了高岭土、膨润土、海泡石的组成、结构及其在合成沸石分子筛时对以上3种黏土的处理改性,并阐述黏土类矿物制备多孔分子筛的应用前景.     

Orientation of montmorillonite clay in dicyclopentadiene/organically modified clay dispersions and nanocomposites

Highly delaminated dispersions of the organically modified clay I‐28 (Nanocor, Inc.) in liquid dicyclopentadiene (DCPD) were prepared. In situ ring‐opening metathesis polymerization of I‐28/DCPD nanodispersions generated I‐28/poly(DCPD) nanocomposites. When clay/DCPD dispersions were cured under shear, alignment of clay platelets, tactoids, and small particles was captured. This orientation was confirmed by X‐ray diffraction and transmission electron microscopy. The Herman's orientation parameters were calculated for the oriented nanocomposites. Viscosities of these liquid nanodispersions exhibited thixotropic flow behavior, prior to curing. The time‐dependent viscosity effects became more pronounced with an increase in delamination. Initial viscosities increased with progressive clay platelet generation during delamination and nanodispersion within the liquid monomer. Viscosity can be used to follow clay exfoliation/delamination. Etching the surface of a 2 wt % I‐28 clay/poly(DCPD) nanocomposite with oxygen plasma eroded the matrix, exposing clay tactoids protruding from the surface. These surfaces were examined by SEM and energy dispersive X‐ray spectroscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2743–2751, 2006     

甘肃凹凸棒矿石的分离与纯化研究

对甘肃临泽出产的凹凸棒矿石进行了纯化、分离实验,确定了高速剪切结合超声波分散的提纯方案,提纯率可达99%以上,且矿浆的悬浮性能大幅提高,并对原矿和提纯矿进行了XRD、FT-IR、SEM、TEM等分析,结果表明经过适当的方法纯化,甘肃凹凸棒矿石的纯度和性能大幅度提高,应用领域和应用价值提高,具备工业化生产的可行性.     

Interaction mechanisms between Na montmorillonite clay and MPEG-based polycarboxylate superplasticizers

Sodium montmorillonite clay is shown to negatively impact the dispersion force of two methacrylate based polycarboxylates (PCEs) in cement paste. The PCEs tested consist of methacrylic acid/MPEG methacrylate-ester with molar ratios of 6:1 and 1.5:1. It was found that the PCEs sorb both chemically and physically onto clay. The sorbed amounts are ~ 100 times more than on cement. Chemisorption occurs via intercalation of the poly(ethylene oxide) side chains into the interlayer region between the alumosilicate layers, while physisorption occurs on clay surfaces which are positively charged through uptake of Ca²⁺. PCEs possessing high grafting density predominantly intercalate and show less surface adsorption, and vice versa. Also, the type of sorption is dosage dependent, whereby side chain intercalation dominates at higher PCE dosages, while electrostatic attraction via the anionic backbone prevails at lower dosages. Polyglycols can be utilised as sacrificial agents when highly grafted PCEs are employed at high dosages.     

Adsorption and intercalation of tetracycline by swelling clay minerals

Many of commonly used pharmaceuticals are hydrophilic. In aqueous solutions, these molecules will have strong interaction with swelling clay minerals, resulting in intercalation of these compounds in the interlayer of the minerals and retention by these minerals. In this research, we studied the intercalation of tetracycline (TC) into swelling clay minerals as represented by montmorillonite and rectorite of different surface charges and different charge densities. The maximum interlayer expansion was seen at a higher pH when the TC molecules adopted an extended conformation, even though, the amount of TC intercalated at higher pH is lower. Under pH 4–5, the intercalated TC produced an interlayer gallery height of 9.2 Å compared to 10.3 Å produced at pH 8.7 in the interlayer space of rectorite. Due to TC intercalation, the full width at half maximum (FWHM) becomes much broader, suggesting that the number of fundamental layers stacking along c axis decreased to 2–3. Depending upon the nature of the swelling clay minerals and the TC concentration, the intercalation process can be transitional, involving in the occurrence of mechanical mixtures, materials of intermediate layer thicknesses, and/or mixed layering of different ordering states.     

Nanocomposites of urethane and montmorillonite clay in emulsion: In situ preparation and characterization

Nanocomposites of polyurethane‐montmorillonite (PU‐MMT) were successfully prepared by in situ emulsion polymerization. The PU‐MMT particles size in emulsion was controlled in nanolevel, which was confirmed by laser scattering size distribution analyzer. The morphology of MMT in PU‐MMT composites was observed by transmission electron microscopy (TEM). Wide angle x‐ray diffraction (WAXD) was also used to detect the dispersion of MMT in composites. The thermal property was evaluated by dynamic mechanical analysis. Mechanical and fracture properties were also been tested. Gas barrier property was discussed on the basis of testing oxygen permeability of PU‐MMT films. The permeability coefficient of the films is found to reduce after composing with MMT, which indicates that the potential application of PU‐MMT could be realized as coating materials to prevent metal rusting. It is also found that dimethyl distearylbenzyl ammonium chloride (DMDSBA) is a better modifier for MMT in PU than dimethyldistearyl ammonium chloride (DMDSA). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Adsorption isotherms of pigments from alkali-refined vegetable oils with clay minerals

Adsorption isotherms of pigments from alkali-refined oils (rapeseed, soybean, wheatgerm, safflower, corn, cottonseed and sunflower) were measured to investigate the applicability of the Langmuir and Freundlich equations and to elucidate the adsorption characteristics of pigments on sepiolites and standard activated clay. The Freundlich equation was more applicable to the experimental adsorption isotherms. The equilibrium amount adsorbed, acidity, pore size distribution and inflection of the Freundlich isotherms could be explained by assuming that pigments were adsorbed on the stronger acid sites in smaller pores at low concentration, and then in the larger ones when the concentration increased. The amount adsorbed increased with a rise in adsorption temperatures from 70 to 110°C, and the heat of adsorption was below 10 kcal/mol. The results indicate that pigments were physically adsorbed on the acid sites activated at higher adsorption temperatures.