Non-swelling Clay Minerals Research Articles

Direct Exchange Mechanism for Interlayer Ions in Non-Swelling Clays.

The mobility of radiocesium in the environment is largely mediated by cation exchange in micaceous clays, in particular Illite-a non-swelling clay mineral that naturally contains interlayer K+ and has high affinity for Cs+. Although exchange of interlayer K+ for Cs+ is nearly thermodynamically nonselective, recent experiments show that direct, anhydrous Cs+-K+ exchange is kinetically viable and leads to the formation of phase-separated interlayers through a mechanism that remains unclear. Here, using classical atomistic simulations and density functional theory calculations, we identify a molecular-scale positive feedback mechanism in which exchange of the larger Cs+ for the smaller K+ significantly lowers the migration barrier of neighboring K+, allowing exchange to propagate rapidly once initiated at the clay edge. Barrier lowering upon slight increase in layer spacing (∼0.7 Å) during Cs+ exchange is an example of "chemical-mechanical coupling" that likely explains the observed sharp exchange fronts leading to interstratification. Interestingly, we find that these features are thermodynamically favored even in the absence of a heterogeneous layer charge distribution.

STABILIZATION OF SOIL SWELLING FOR CONSTRUCTION PURPOSES, USING PHOSPHOGYPSUMAND SODIUM CHLORID

This paper deals with the improvement of soil swelling for purposes of constructions by adding industrial waste Phosphogypsum (PG), in addition to the chemical additive sodium chloride (NaCl) to reduce its expansiveness and improve its characteristics for many earth work construction, the test results showed significant decrease in the swelling properties and pronounced reduction in the liquid limit, plastic limit and plasticity index of the clay by increasing the ratios of PG and NaCl. Also the results from x-ray diffraction (XRD) analyses of bentonit only and the mixture (1.2% PG+3% NaCl+95.8% Bent.) showed that, large amounts of Montmoronite clay mineral were approximately transformed to other phases during the reaction. Reaction products are non-swelling clay mineral commonly Kaolinite this is because, the mineralogy of both clay minerals reflects that, Montmoronite is an immature clay mineral while Kaolinite is a mature clay mineral. This maturity state may be attained through the chemical reaction with these additives. So, the PG industrial waste helps to improve the physical characteristics of soil swelling and the results present a very important factor for constructions purposes.

Influence of Nonswelling Clay Minerals (Illite, Kaolinite, and Chlorite) on Nonaqueous Solvent Extraction of Bitumen

Artificial mixtures of bitumen with three natural clay standards, dominated by illite, kaolinite, and chlorite, were reacted for several days and washed three times each with cyclohexane to remove bitumen from the clays. The main goal was to determine and better understand the effect of nonswelling clay minerals (illite, kaolinite, and chlorite) on nonaqueous solvent bitumen extraction. The experimental results showed that the total amount of residual cyclohexane insoluble organic carbon (CIOC) measured for clay–bitumen mixtures after nonaqueous solvent bitumen removal is a function of intrinsic resistance of high molecular weight (MW) organic compounds to cyclohexane extraction and the nature of nonswelling clays. The intrinsic resistance of high MW organic compounds to cyclohexane extraction accounted for 42–80% of the total CIOC content. The nonswelling clays retained from 20 to 58% of CIOC of the total CIOC content primarily on the external surfaces (basal planes and edges) of clay mineral particles i...

Thermodynamic and fully-coupled reactive transport models of a steel–bentonite interface

Engineered barrier system (EBS) designs for the geological disposal of high-level radioactive waste often include a bentonite buffer, the primary function of which is to protect metal waste containers or overpacks from mechanical shearing. The buffer also acts as a barrier to solute transport. One potentially deleterious process that may occur in the buffer is the alteration of swelling clay to iron-rich minerals, some of which have a limited capacity to swell. There is a dearth of relevant natural analogues of iron–bentonite interactions, and experimental data do not provide an unequivocal indication of the conditions that will promote non-swelling clay minerals (such as berthierine) to form rather than swelling clays (such as iron-rich saponite). In addition, many of the previously-published reactive transport models of iron–bentonite or iron–claystone interfaces have not considered how evolution of mineral–fluid equilibria in the bentonite buffer could affect the nature and rate of steel corrosion. In this study, new thermodynamic models of iron-rich clay minerals are presented which suggest that the activities of major ions, especially Fe2+, Fe3+, Al3+, H+ and SiO2(aq), act as key controls on the relative stabilities of iron-rich clay minerals. In particular, they suggest that Fe-saponite is stabilised under low fO2(g) conditions when SiO2(aq) activities are buffered by quartz or more soluble silica polymorphs (e.g. chalcedony). Iron-rich 1:1 clay minerals, such as berthierine, tend to be stabilised in fluids that are quartz under-saturated. The thermodynamic models were used to inform the development of three fully-coupled reactive transport models of a steel–bentonite interface: (1) steel corrosion reaction applied on a boundary directly in contact with bentonite at a fixed rate; (2) steel corrosion reaction applied on a boundary directly in contact with bentonite at a diffusion-limited rate; and (3) a ‘corrosion cell’ representation with a fixed steel corrosion rate.The extent and nature of the alteration predicted by the models was found to be sensitive to model conceptualisation. The corrosion cell assumption leads to steel corrosion products including magnetite and siderite and the alteration of primary minerals to berthierine (∼2cm thick layer forming over 100000years, with partial loss of montmorillonite to a depth of ∼9cm). In contrast, the boundary corrosion assumption with a fixed steel corrosion rate leads to quicker alteration to iron-rich clay minerals. If the diffusion-limited corrosion rate assumption is made, the steel corrosion rate varies over time as the bentonite porewater composition evolves, and the spatial extent of alteration is much more limited (millimetre scale). Although much progress has been made, a number of uncertainties associated with modelling bentonite evolution remain, especially with regard to ion transport through smectite interlayers and the potential for complex couplings between chemical and physical processes.

Adsorption of tetracycline on 2:1 layered non-swelling clay mineral illite

The removal of tetracycline (TC) from aqueous environment by illite (IMt-2) was studied in a batch system at different pH and ionic strength conditions. Adsorbent characterizations were determined by XRD and FTIR. The TC adsorption capacity on IMt-2 was 32mg/g at pH 5–6 and the adsorption equilibrium data obeyed the Freundlich isotherm. The kinetics of TC adsorption was moderately fast and almost reached equilibrium in 8h and the results followed pseudo-second-order kinetic model and Elovich model. The X-ray diffraction patterns before and after TC adsorption revealed no changes in basal spacing and intensity under two kinetic adsorption and a few initial TC concentration conditions, indicating that the adsorbed TC molecules were on the external surface of the mineral in contrast to intercalation of TC into swelling clay minerals, such as montmorillonite and rectorite. In spite of its low TC adsorption capacity, the results suggested that IMt-2 could be a good candidate to remove TC from wastewater containing higher amounts of TC and illite would be an important environmental sink for the fate and transport of TC in soils.

Alteration of cameroonian clays under acid treatment. Comparison with industrial adsorbents

In view to evaluate an alternative local cheaper source for vegetable oil refiners, three cameroonian clays containing swelling (smectites) and non-swelling (kaolinite) clay minerals were treated with sulphuric acid solutions at concentrations of 1, 2, 4 and 8 N at 80 °C for 2 h. Their alteration and resulting products were characterized by XRD, FT-IR-spectroscopy, chemical analyses, along with TEM-EDS, nitrogen adsorption isotherms at 77 K, and compared with industrial bleaching earths. Acid treatment of Cameroonian clays leads to the classically observed cristallochemical and textural modifications. The plot of TEM-EDS data in Al 2O 3/SiO 2 and Fe 2O 3/Al 2O 3 diagrams indicate that upon acid treatment, clay particles principally move towards the SiO 2 pole, consistent with the formation of an amorphous compound mainly siliceous as the result of acid activation. Concomitantly, a progressive decrease in cation exchange capacity (CEC) was observed with increasing sulphuric acid concentrations while both specific surface area and mesoporosity of the studied materials increase. Elemental analyses, X-ray and spectroscopy data reveal that acid activation affects both the octahedral and the tetrahedral sheets. The analysis of their reactivity shows that clays with high amounts of smectite are more sensitive to acid leaching than those with relative large kaolinite contents. Further, upon acid treatment, most trace and rare earth elements are leached, and the amount of toxic elements (e.g. Cd, Pb, Ni, Cu, As, Zn) in the by-products is low (< 50 mg/kg). Mineralogy, chemical analyses and textural properties of the activated products match the specifications of industrial adsorbents. Therefore, activated Cameroonian clays are expected to perform well in respect with decolorization of vegetable oils.

Alteration of non-swelling clay minerals and magadiite by acid activation

The bulk material of three kaolins, a sepiolite, an illite and one magadiite were treated with 1, 5 and 10 M H 2SO 4 at 80 °C for several hours. The alteration of the non-swelling clay mineral structures was controlled by the individual character of each mineral (chemical composition and initial particle size). The reaction resulted in a successive dissolution of the octahedral sheets by edge attack. The number of substitutions by Mg or Fe in the octahedral sheet promoted the dissolution of these layers and the formation of a silica phase. High amounts of Al in the tetrahedral sheet of the clay minerals caused partial dissolution of these sheets. The dissolution of the octahedral cations occurred in the following order: Mg > Fe > Al. Thus, dioctahedral clay minerals were more stable against acid attack than trioctahedral clay minerals. The release of the octahedral cations caused the lightening of the material together with a development of micropores and an increasing specific surface. Dissolution and splitting of the particles required longer reaction times compared to swellable smectites and vermiculites. Acid activation of non-swelling clay minerals can be used to produce layered materials with simple chemical composition and high specific surface area.

Moisture spreading in a multi-layer hydraulic sealing system (HTV-1)

An important function of the multi-barrier system in the concept of geologic disposal of hazardous or radioactive waste is to limit water flow through the repository. The sealing system of geotechnical barriers consists commonly of bentonite with a very low hydraulic conductivity and high swelling and sorption capacity. Uniform wetting of the bentonite is a prerequisite of a high performance, but preferential flow paths partially inhibit the swelling process and increase the hydraulic conductivity of the material. We developed a new sealing system (sandwich) that combines layers of different soil hydraulic properties. Layers with a sealing function are combined with equipotential layers (ES), that are characterized by a hydraulic conductivity several orders of magnitude higher than the bentonite. A penetrating waterfront will be homogenized in ES which supports a more homogeneous swelling process. The HTV-1 was a perpendicular semi-technical scale experiment that reflects a typical shaft sealing construction with respect to orientation. A natural Ca/Mg-rich bentonite (Calcigel) was used for the sealing elements and a combination of fine sand together with an artificial mixture of fine sand, limestone and non-swelling clay minerals (kaolinite) was used for the equipotential layers. A rock salt brine of 1.15 g/ml was chosen to simulate natural brines. The moisture spreading was monitored by time domain reflectometry (TDR) sensors. Artificial induced disturbance within the sealing layers forced enhanced water flow for demonstration. The moisture moved faster in this artificially disturbed region of the column than in the undisturbed part. After moisture reached an ES it spread evenly over the column cross section and wetted the lower bentonite layer from the back. Thus the HTV-1 demonstrated the functionality of the multi-layer hydraulic sealing system even under the inflow of rock salt brine, which makes it adjustable to different kinds of surrounding rocks and pore waters. All applied sensors (TDR and pressure) displayed no sign of corrosion after more than one year of operation. Therefore the sensors are suitable for intermediate to long-term monitoring.

Effect of heavy metal and alkali contamination on the swelling properties of kaolinite

One of the most important factors that determine engineering properties of soils are the type and the amount of clay present in soil. Kaolinite being a very common and non-swelling clay mineral in soil was chosen as the medium, and significance of the change in swelling property of kaolinite due to contaminant-clay interaction was investigated. The amount of change in swelling percentages of the kaolinite due to contamination with 10,000 ppm solutions of Pb(NO3)2 and Zn(NO3)2 was determined using oedometers. For uncontaminated kaolinite, the amount of swell was determined as 2.2%. For Pb-contaminated and Zn-contaminated kaolinite, these values reached to 5.8 and 5.3%, respectively. Besides heavy metals, kaolinite was also contaminated with 4 N NaOH. The biggest change in the amount of swelling was obtained from NaOH-contaminated kaolinite which is 13.9%. In addition to swelling percentages, swelling pressures were also determined. The swelling pressure of the uncontaminated kaolinite was found as 1.06 N/cm2. For Zn and Pb-contaminated kaolinite, this value reached up to 2.0 and 2.6 N/cm2. The NaOH-contaminated kaolinite has the greatest swelling pressure which was 230 N/cm2.

Limitations in the use of electrical conductivity to monitor the behaviour of soil solution

Solutions of KBr and K2SO4 of various concentrations were separately displaced by deionised water through 2 contrasting saturated materials, inert solid particles (glass ballotini), and a reactive but non-swelling aggregated clay mineral (sepiolite) over a wide range of flow rates. The concentration of the individual ions in the effluent was analysed (Br– and K+ with ion-specific electrodes, SO42+ by ion chromatography) and that of bulk solution was measured by electrical conductivity (EC). For each displacement, the individual breakthrough curves (BTCs) for the anion, the cation, and the bulk solution were optimised by CXTFIT 2.0. In ballotini, the BTCs of the anion, cation, and solution were always congruent, the retardation factors did not differ significantly from unity, and the coefficients of hydrodynamic dispersion were identical. For sepiolite, the ions were separated; the bulk solution eluted faster than the cation, slower than the anions. Retardation factors were always less than unity for the anions, greater than unity for the cation, and close to but less than unity for the bulk solution, and became more extreme as the concentration of solute decreased. Dispersion coefficients were, however, unaffected by type of solute, concentration range, or particular ion/EC. The separation of ions means that the composition as well as the concentration of a solution changes continuously during flow through a reactive soil. Estimates of solution concentration from measurements of EC may thus fail to characterise adequately the movement of the individual components of the solution in such materials. This has implications for the interpretation of any leachate monitoring in reactive soils by methods based on the measurement of EC, such as time-domain reflectometry.

AFM and low-pressure argon adsorption analysis of geometrical properties of phyllosilicates

The distribution of edge and basal surface areas of phyllosilicate particles is an essential parameter for understanding the interaction mechanisms at solid/gas or solid/liquid interfaces. Among the techniques proposed to determine the geometrical heterogeneities of flat solids, low-pressure argon adsorption and AFM analysis are the most promising to derive the weight-averaged values of specific surface areas. A series of publications have recently been dedicated to the combination of both methods showing the correlation between the two approaches. As obtaining a large set of high-resolution AFM images is time-consuming, it is necessary to test the ability of AFM routine analysis to derive surface areas and aspect ratio systematically and statistically, with all possible experimental and instrumental artefacts. In the present study, the expected agreement was found between AFM and argon adsorption determination for total, basal, and edge-specific surface areas of nonswelling clay minerals, except for one kaolinite, which is very heterogeneous in size. In addition, it was observed that for a given sample, individual particles present similar shapes, whatever their size, making it possible to derive a statistical relationship between AFM basal and total surface areas. On the basis of the obtained results, recommendations are given to derive accurate edge, basal, and total specific surface areas of phyllosilicates by combining conventional gas adsorption (nitrogen BET) and routine AFM techniques.

Interpretation of the infrared spectrum of the -clays: application to the evaluation of the layer charge

AbstractThe IR spectra of -saturated smectites were examined in terms of their charge characteristics. The υ4 band near 1440 cm-1, observed in the DRIFTS spectra (obtained without use of a KBr matrix), was assigned to the vibrations of ions compensating the negative charge of the clays. When KBr was used as a diluting matrix, the υ4 band was located at 1400 and/or 1440 cm-1. The band at 1400 cm-1, related to NH4Br, originated from the replacement of in the clay by K+ from the KBr. For swelling clay minerals this band indicates that layers have permanent low charge density and/or variable charge. For non-swelling clay minerals, the 1400 cm-1 band characterizes the presence of variable charges only. The υ4 band at 1440 cm-1 suggests that in the clay was not replaced by K+ from KBr and remains in the interlayer space of the clay minerals. This absorption is due to compensating only permanent charge in the interlayers, or part of the interlayers with a high charge density. The presence of both bands at 1400 cm-1 and 1440 cm-1 in the IR spectrum suggests that the clays studied have a heterogeneous interlayer charge.

Adsorption of polyvinylpyrrolidone on kaolinite

The adsorption of the uncharged polymer polyvinylpyrrolidone (PVP) with molecular weights from 5000 to 600 000 g mol −1 on the non-swelling clay mineral kaolinite has been studied. The effects of the adsorbent concentration, solution pH and PVP molecular weight on the binding isotherms were investigated. The varying affinity character of the binding isotherms with the kaolinite concentration can be related to some molecular weight fractioning of the synthetic polymer samples. An adsorption decrease of about 20% in the pH range 3.5–10.3 indicates that the protonation of kaolinite edge surfaces may also be involved in the adsorption process. At pH 5.5, the maximum amount adsorbed varies with PVP molecular weight ⩽44 000 g mol −1. At higher molecular weights, a levelling-off of the adsorption is found at 1.2 mg m −2. The electrokinetic thickness, δ e , of PVP layers on the kaolinite surface was determined by microelectrophoresis. At ionic strengths ⩽10 −4 M, δ e tends to a limit which can be put equal to the hydrodynamic layer thickness, δ h . The molecular weight dependence of δ h in the presence of a fixed PVP concentration and the adsorbed amount dependence of δ h for various PVP molecular weights are discussed. At high PVP concentrations for surface kaolinite saturation, it can be shown that the molecular weight dependence of the polymer expansion in solution does not change greatly after adsorption. Thus, at high surface coverage, a relatively large increase of δ h up to 100 nm with a PVP molecular weight of 600 000 g mol −1 can be related to a high fraction of segments in loops. On the other hand, at low PVP surface coverages, ⩽0.6 mg m −2, a fairly constant δ h of about 10–14 nm regardless of the PVP molecular weight is found. The build-up of a condensed PVP layer which results from the flattening of the polymer coil structure can be suggested.

Determination of the acid-base characteristics of clay mineral surfaces by contact angle measurements-implications for the adsorption of organic solutes from aqueous media

The apolar and the polar (electron-acceptor and electron-donor, or Lewis acid-base) surface tension components and parameters of solid surfaces can be determined by contact angle measurements using at least three different liquids, of which two must be polar. With swelling clay minerals (e.g. smectite clay minerals), smooth contiguous membranes can be fabricated, upon which contact angles can be measured directly. With non-swelling clay minerals (e.g. talc), contact angles can be determined by wicking, i.e. by the measurement of the rate of capillary rise of the liquids in question through thin layers of clay powder adhering to glass plates. The apolar and polar (acid-base) surface tension components and parameters thus found for various untreated and quaternary ammonium base-treated clays allowed the determination of the net interfacial free energy of adhesion of human serum albumin onto the various clay particle surfaces immersed in water. The free energies of adhesion, thus found, correlate well with t...

Sorption and immersional wetting on clay minerals having modified surface. I. Surface properties of nonswelling clay mineral organocomplexes

Adsorption of methanol-benzene mixtures and the immersional wetting properties have been investigated on nonswelling clay minerals with lamellar structure (kaolinite and illite) and on their organocomplexes obtained by hexadecyl-pyridinium cations (HDP +). It has been found that the surface modification can influence the selective liquid adsorption. To interpret unambiguously the extent of the surface modification the nonpolar-polar surface area ratio can be calculated from the sorption data. From the excess isotherms and the enthalpy of immersion the surface thermodynamic potential functions have been calculated. The changes of these functions and the equilibrium constant of the adsorption with the surface polarity is given. Adsorption capacity data and immersional wetting experiments indicate that the surface extension of these organocomplexes can change in some degree.

A model system for studying the biochemistry and biology of the root-soil interface

Calcined attapulgite, a non-swelling clay mineral, has been used as a medium for plant growth when mixed with a nutrient solution in the proportion of 0.95 ml g −1. Attapulgite is an ideal model “soil” for ultrastructural studies, enabling large intact thin sections through root, rhizoplane and soil. Transmission electron micrographs are presented which illustrate the value of attapulgite for in situ studies of rhizosphere populations, for the demonstration of enzyme activities in individual bacteria and for specific staining of extracellular polysaccharide. A standard fumigation-respiration technique widely used for estimating soil microbial biomass is shown to give unreliable results for rhizosphere samples and should not be used to measure microbial biomass in close asssociation with living roots. The addition of a dilute soil suspension to the attapulgite medium caused a stimulation of root growth without any increase in shoot growth.

Frost damage to stone and concrete: geological considerations

Frost damage to stone and concrete is due to expansion during freezing of water. This process is presented in the p—v—t diagram of ice which is updated and lines of density added for the phases water and ice I. Water also expands 0.4% at 1 atm when heated from 4 to 30°C, and 0.6% at 1 atm, if undercooled from 4 to —20°C. A modified diagram with t on the abscissa and the density change in percent on the ordinate gives expansion curves for 1, 25, 50, 75, and 100 atm. Water is enough compressible that no expansion can take place from 4 to 30°C, if the capillaria walls can resist stresses to 100 atm which are insufficient to break up sound rock. The efficiency of water transportation to the zone of freezing in soils and rocks depends on the size and distribution of capillaria, and the presence of non-swelling clay minerals which act like water pumps along the channels without closing the channels. Water in micropores, however, is unfreezable and much less mobile than water in larger channels, if only a few molecules thick, oriented, and stressed. Engineering geological applications of the p-v-t ice diagram are as follows: (a) the frost stability of stone, if strength, climate, and capillaria size are known; (b) the stability of point-bearing piles in muddy frozen sediments; (c) the knowledge of the rock strength in estimates of minimum Pleistocene rock temperatures of felsenmeers. The freezing process of water is known to produce a spontaneous expansion from a density of about 1.000–0.9165. The expansion pressure (or crystallization pressure) may be of considerable importance as it aids in the mechanical disintegration of natural rock, structural stone and concrete. The interest in the process of freezing started at the beginning of the 19th century when the expansion as well as the contraction of ice at increased pressures was recognized. Only recently we have learned that the damaging frost action does not depend on the expansion of ice alone, but rather on a variety of processes which diagram of ice may find an application in engineering geology. The discussion also extends to the implications which the lithology may have in the frost safety of rocks and soils. It is the hope that the previous discussion will be helpful to both the geologist and the engineer.

Clay Content and Capillary Behavior of Wyoming Reservoir Sands

Published in Petroleum Transactions, AIME, Volume 210, 1957, pages 414–416. Abstract Samples of four reservoir sands having different degrees of water sensitivity were subjected to several laboratory tests to determine differences in capillary behavior attributable table to clay-mineral effects. The degree of water sensitivity was estimated by the difference between gas and water permeability. Unsaturated pore volumes determined with mercury injection were comparable to irreducible water saturations determined with the semipermeable barrier method only for the non-sensitive sands that contained small amounts of non-swelling clay minerals. Irreducible saturations were independent of salinity of the water, which suggests that most residual water is adsorbed as a film over solid surfaces and that internal retention by clay minerals is relatively insignificant. The water-sensitive sands imbibed water to higher saturations than did non-sensitive sands, and this result is believed to be a combination of the effects of clay minerals and preferential wettability; however, the relative importance of each of these effects is not determinable. Thus it is concluded that the semipermeable barrier method is the best of the laboratory methods used for estimating formation water saturations in the sands studied. Introduction This investigation is a continuation of studies of the role of clay minerals in petroleum production in the Rocky Mountain area. Previous work has shown large differences in gas and water permeability in numerous reservoir sands; these water-sensitivity effects observed in the laboratory have been correlated with well behavior in the field, and the degree of water sensitivity imparted to reservoirs by the various clay minerals has been determined. The effect of interstitial clay minerals on formation water saturations is not so well known. It has been reported that formation water saturations probably are higher in clayey than clean sands, but this effect has not been evaluated in the laboratory, and the relative effect of the various types of clay minerals on formation water saturation has not been determined.