Mixture Of Montmorillonite Research Articles

Mineralogy of the Tertiary Clay Deposits in Makkah and Rabigh Quadrangles, West Central Arabian Shield, Saudi Arabia

The mineralogy of the Tertiary clay deposits in Makkah and Rabigh quadrangles was thoroughly investigated by X-ray diffraction and differential thermal and thermogravimetric analyses in addition to other techniques. Results show that the investigated samples are predominantly composed of montmorillonite (Ca++ and/or Mg++ rich variety) and kaolinite, associated with subordinate illite and minor chlorite. Mixed layer montmorillonite-illite is recorded only in two samples. The relative abundance of these minerals by X-ray diffraction analysis showed that the studied clay deposits are of three types. The first, which is the most common, is highly montmorillonitic, the second is made up of a mixture of montmorillonite followed by kaolinite and illite and the third is highly kaolinitic with some montmorillonite. Generally, kaolinite shows a southward increase in Makkah quadrangle while chlorite, as a minor component, shows a northward increase in Rabigh quadrangle.

Laboratory observations and mathematical modeling of colloid‐facilitated contaminant transport in chemically heterogeneous systems

In the work reported here, I examine colloid‐facilitated solute transport through a natural porous medium that exhibits grain‐scale heterogeneity in chemical composition. I conducted six column experiments using the contaminant hydroxyatrazine (HA) and either homogeneous clay‐colloid suspensions or mixtures of clay colloids and dissolved organic matter. The transport of colloids composed of illite and montmorillonite, although not conservative, is only slightly affected by rate‐limited mass transfer reactions with the oxide‐coated aquifer material. Coinjection of HA with monomineralogic suspensions of illite colloids produces modest increases in effluent concentrations of HA relative to experiments performed with colloid‐free influent solutions. Montmorillonite colloids have a much higher capacity to bind HA than illite colloids and substantially increase the transport rate of HA in the column experiments. Suwannee River humic acid (SRHA) does not strongly complex aqueous phase HA, but its addition to column influent mixtures that contain HA and montmorillonite suppresses HA adsorption to the clay colloids and promotes a decline in HA mobility. A model for colloid‐facilitated transport, formulated to account for nonuniformity in the kinetics of colloid deposition and HA adsorption, closely describes HA transport in experiments performed with monomineralogic clay‐colloid suspensions, heterogeneous suspensions made of both illite and montmorillonite, and mixtures of montmorillonite and SRHA.

Specific interaction governing the melt intercalation of clay with poly(styrene‐co‐acrylonitrile) copolymers

AbstractIn the melt intercalation of cation‐exchange clay, mixtures of montmorillonite and poly(styrene‐co‐acrylonitrile) (SAN) with various acrylonitrile contents were studied to examine the effect of specific interaction. When organic molecules with hydroxyl groups were used as intercalants for the clay, the amount of SAN penetrating the gallery of the layered structure of the clay and the corresponding increase in the gallery height occurred at a much higher rate because of the attractive specific interaction between acrylonitrile groups and polar groups on the clay surface. However, there was a limit to the increase in the gallery height, and the tendency for the gallery height to increase with the acrylonitrile group content disappeared when the acrylonitrile content was greater than 30 wt %, implying that excessive attractive interaction on the clay surfaces and polymer molecules glued the two adjacent silicate layers together; consequently, the increase in the gallery height could not be accomplished. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2430–2435, 2001

Protein fractionation using selective adsorption on clay surface before filtration

Protein fractionation by membrane filtration has been investigated through the selective adsorption on clay particles. The micro-filtration of bovine serum albumin, haemoglobin and montmorillonite mixtures was carried out. Both proteins have similar molecular weights, bovine serum albumin (BSA) has an isoelectric point at pH 4.8 while haemoglobin (Hb) is positively charged up to pH 7.0. The aim was to improve the selectivity of the separation by exploiting the different electrostatic interactions and in the meantime to reduce membrane fouling by proteins, thanks to the formation of a secondary membrane by the clay particles on top of the original membrane. We have studied the effects of suspension characteristics (pH, ionic strength, protein and clay concentrations) on adsorption isotherms of protein on clay particles and on separation performances such as micro-filtration limiting flux, protein transmission and separation factor. The optimum results were obtained with an ionic strength of 10 −3 M and a pH value around 7.0. In these conditions, only Hb was adsorbed on clay particles while BSA stayed free in solution.

Monolayer Coverage–Sorbate Area Relationship for Mixtures of Sorbents

The adsorption of molecules of different sizes, at monolayer coverages, was determined for binary mixtures of montmorillonite and hydroxy-Al montmorillonite in order to test the applicability of the general equation (NAz = k) relating the number of sorbate units at monolayer coverage (N) with their areas (A). The effect of the proportions of the components in the mixture on the value of the exponent z was also evaluated. The data obtained confirm the validity of the equation and indicate that the value of z for the mixtures assumes intermediate values between the two z values of the components, depending on their proportions. It is also demonstrated that the z exponent could have a value of unity (a value supposed to indicate surface uniformity) for certain mixtures of sorbents having z values different from unity, i.e., possessing nonuniform surfaces.

Nickel Sorption Mechanisms in a Pyrophyllite–Montmorillonite Mixture

Nickel sorption on pyrophyllite, montmorillonite and a 1:1 pyrophyllite–montmorillonite mixture was studied at pH 7.5 and a reaction time of 40 min. The main modes of Ni uptake under these reaction conditions are adsorption on montmorillonite and surface precipitation on pyrophyllite. For the clay mixture, where adsorption on the montmorillonite component and surface precipitation on the pyrophyllite component compete for Ni uptake, X-ray absorption fine structure spectroscopy (XAFS) was used to estimate the distribution of Ni over the mixture components. This was done by comparison to pyrophyllite–montmorillonite mixtures with known Ni distributions over the mixture components. Nickel uptake on singly reacted pyrophyllite was slightly higher than on singly reacted montmorillonite. This was consistent with the XAFS results for the clay mixture, which suggested that the pyrophyllite component sorbed slightly more Ni than the montmorillonite component. Our findings suggested that both adsorption and surface precipitation were important mechanisms in the overall Ni uptake in the clay mixture, and that neither sorption mechanism truly out-competed the other in the reaction time of 40 min employed. Therefore, both mechanisms should be considered when modeling Ni sorption in similar systems.

Zinc adsorption by lime‐treated montmorillonite clay

In this research, lime‐treated montmorillonite clay is used to adsorb Zn(II) in a wide range of Zn(II) concentrations. Batch test results show that the adsorption of Zn(II) by montmorillonite appears to be dominated by different adsorption mechanisms. At low Zn(II) concentrations, chemisorption affects the amount of Zn(II) adsorbed by montmorillonite. When lime is added, physisorption becomes increasingly important. At high Zn(II) concentrations, physisorption is the dominant mechanism for Zn(II) adsorption. Lime also enhances the ability of montmorillonite to adsorb Zn(II) at low initial Zn(II) concentrations, and does not significantly affect the ability of montmorillonite to adsorb Zn(II) at high initial Zn(II) concentrations. In chemisorption, montmorillonite provides cation exchange sites for the adsorption of Zn(II). In physisorption, montmorillonite acts as not only nucleation center to adsorb zinc hydroxide‐oxides but also helps to coagulate the zinc hydroxide‐oxides. Lime‐treated clay can therefore be an effectively used to adsorb metals such as zinc even at very high metal concentrations. The significance of these findings is in the design of landfill liner. A mixture of montmorillonite (bentonite) clay and lime is shown to have characteristics that would make this material a superior landfill liner. The lime‐treated clay has low hydraulic conductivity, enhanced metal removal capability, and better resistance to penetration by sharp objects.

Influences of salt concentration, loading and pH on strontium adsorption

The adsorption of Sr on clay which contains zeolites and montmorillonite mixtures was investigated in solutions of NaCl by means of a batch technique. Sr retention was reduced with increasing NaCl concentration from 5·10−4 to 5·10−1M. Distribution coefficients (Kd) linearly increased with pH in the acidic region but they were almost independent of pH in neutral and alkaline solutions. By fitting the data of the Dubinin-Radushkevich (D-R) isotherm, the mean energies of adsorption and adsorption capacities of Sr at different pH values were calculated. The results showed that the mode of adsorption below pH 4.5 is ion exchange, while above that value a multilayer adsorption occurs. Adsorption data were fitted to the Freundlich isotherm and from empirical Freundlich parameters a site distribution function was calculated.

Effect of Gravel on Pumping Behavior of Compacted Soil

Pumping can occur when clay is compacted wet of optimum. Rather than densifying, the clayey soil squeezes out from underneath the compaction equipment. Adding gravel to the clayey soil creates a granular skeleton that increases the undrained shear strength. The results of this study show that even a partial gravel skeleton can prevent pumping of a clayey soil. Pumping occurred during the modified proctor compaction test when the undrained shear strength was less than 14 kPa (290 psf) and the initial tangent modulus was less than 1,600 kPa. To prevent pumping, the tested clayey soil (sand and montmorillonite mixture) had to contain at least 63% rounded gravel or 54% angular gravel. A lower percentage of angular gravel prevented pumping because it more effectively interlocked and created the necessary gravel skeleton at a lower density than the rounded gravel.

Vibratory Extraction of Clay Fines from Subsurface

This paper presents results from laboratory investigations on utilizing ultrasonic and subsonic vibrations to facilitate removal of fine clay particles from the subsurface. A sonicator and a laboratory vibrator were used to vibrate mixtures of sand and pure clay minerals as well as a sample of natural soil from New Jersey. In column experiments, particle extraction resulted in an enhancement in the hydraulic conductivity. Effluent slurries from kaolinite mixtures contained more fine particles than those from montmorillonite mixtures. When subsonic vibrations were applied after ultrasonic treatment, additional quantities of fines were extracted. Abrasion and/or fracturing of sand‐ and silt‐sized grains occurred near the vibrating source. The formation of low‐permeability layers because of particle migration and accumulation may have occurred in the experiments. Experiments conducted in 90‐cm‐ and 120‐cm‐diameter tanks showed that the zone of influence of vibrations extended as far as the tank walls. These results suggested that in‐situ implementation of localized vibrations to enhance hydraulic conductivity of clayey soils, and to facilitate controlled mobilization of clay fines and the associated contaminants, may be feasible.

Description of titration curves of mixed materials with variable and permanent charge by a mathematical model. 3. Influence of the nature of the permanent charge mineral

SUMMARYA mathematical model, previously developed, is tested here for various clay minerals and their mixtures with iron oxides. The model yields good predictions of the permanent charge for non‐swelling clay minerals, but clearly underestimates the permanent charge of montmorillonite. This result is interpreted as being caused by partial accessibility of the internal surface of the mineral.In all cases, the values estimated for the permanent charge of the clay minerals fit the data for their mixtures with iron oxides. Nevertheless, important differences are found between the values of maximum densities of adsorption sites of potential‐determining ions of the various minerals estimated when they are alone and when they are in mixtures, particularly in the case of montmorillonite mixtures. The differences are explained in terms of an intimate association between the particles in the mixtures, and some SEM and EDX results point to the same conclusion.

Strength and consistency of artificial clay — carbonate mixtures: Simulation of natural sediments

Marl, a common rock within carbonate sequences in Israel, occurs as an intimate mixture of varying proportions of clay and carbonate. The diagenetic process involved in the formation of the rock is controlled by the physical and chemical properties of the material as it progresses from sedimentation through diagenesis to lithification. To provide a better understanding of the formation of these rocks, natural sediments were simulated in the laboratory. This was done by mixing varying proportions of Upper Cretaceous smectites (bentonite and montmorillonite clay) and Jurassic kaolinite from Makhtesh Ramon with Eocene chalk from the northern Negev. The strength and consistency of these mixtures was then determined. The relationship of Plasticity Index to Liquid Limit, with a correlation coefficient of 0.945–0.982, shows that the bentonite mixtures are of medium to high compressibility in comparison to the kaolinite mixtures, which have a low plasticity. The montmorillonite mixtures have a medium plasticity. Free swell of the bentonite and montmorillonite mixtures is in general twice that of the kaolinite mixtures and decreases in all cases as the carbonate content increases. The effective range in friction angle, under drained conditions similar to those occurring in the natural environment, and saturation of up to 80%, is generally consistent with increasing carbonate, being only slightly higher in the montmorillonite mixtures. Cohesion is higher in the bentonite mixtures. Marls containing bentonite or montmorillonite undergo relatively higher volume changes than kaolinite muds. They also deform plastically, being more sensitive to changes in natural water content. Generally, kaolinite muds are more stable and less deformed during lithification.

Apparent and Partial Specific Sorption of Oxine by Montmorillonite and Silica Gel in Binary Mixtures

AbstractOxine sorption by binary mixtures of montmorillonite and silica gel was studied at pH 5 as a function of oxine concentration and mixture composition. The investigation was made to resolve the problem of the determination of the oxine sorbed by each substance, inasmuch as the total amount sorbed by the mixture is the only value accessible experimentally. By the application of the thermodynamic method of partial quantities, the apparent and partial specific sorption by the clay and by the gel were calculated. These sorption values were found to increase with oxine concentration and to decrease as the proportion of the clay increased in the mixtures.

A porous material prepared from the layer-type complex consisting of montmorillonite and α-naphthylamine

Aqueous mixtures of montmorillonite and α-naphthylamine with various mixing ratios were kept at 353 K for 3 days with stirring to convert them into the layer-type complex (MNC) consisting of both components, and then dried at 403 K. The resulting blocks, several centimetres in size, were heated below 1473 K under nitrogen. The addition of α-naphthylamine (NA) in the equivalent amount to the cation exchange capacity of montmorillonite resulted in the most attractive porous material which includes homogeneous pores of ∼35nm radius and exhibits a maximum pore volume of 0.8 ml g−1 at 873 K. The samples containing greater and lesser amounts of NA gave a very brittle block and a less porous block after heating to high temperature, respectively. The materials obtained were also characterized by the waved card-house structure. The amount of NA added and the heat-treatment temperature did not vary the pore size so widely.

Quantitative Analysis of Mineral Mixtures Using Linear Programming

AbstractThe approximate maximum and minimum amounts of any phase in a complex mineral mixture can be determined by solving a linear programming problem involving chemical mass balance and X-ray powder diffraction (XRD) data. The chemical information necessary is the bulk composition of the mixture and an estimation of the compositional range of each of the minerals in the mixture. Stoichiometric constraints for the minerals may be used to reduce their compositional variation. If only a partial chemical analysis for the mixture is available, the maximum amounts of the phases may still be estimated; however, some or all of the stoichiometric constraints may not apply. XRD measurements (scaled using an internal standard) may be incorporated into the linear programming problem using concentration-intensity relations between pairs of minerals. Each XRD constraint added to the linear programming problem, in general, reduces the difference between the calculated maximum and minimum amounts of each phase. Because it is necessary to define weights in the objective function of the linear programming problem, the proposed method must be considered a model. For many mixtures, however, the solution is relatively insensitive to the objective function weights.An example consisting of a mixture of montmorillonite, plagioclase feldspar, quartz, and opal-cristobalite illustrates the linear programming approach. Chemical information alone was used to estimate the mineral abundances. Because quartz and opal-cristobalite are not chemically distinct, it was only possible to determine the sum, quartz + opal-cristobalite, present in the mixture.

Interactions between crystalline medicinals and porous clay.

The physicochemical properties of drug molecules in a mixture with montmorillonite or pillar interlayer montmorillonite (PILM) were studied by using differential scanning calorimetry (DSC), powder X-ray diffraction and infrared (IR) spectroscopy. The DSC and IR data indicated that benzoic acid was converted to ionic species by heating to 400K in PILM200 and PILM400 mixtures, whereas benzoic acid molecules partially existed in an amorphous state in both montmorillonite and PILM600 mixtures.The decomposition rate of aspirin in the montmorillonite mixtures was studied at 40°C and 0, 31.3 and 79% relative humidities (RH). Asprin was decomposed rapidly at 0% RH as compared with 79% RH in the PILM mixtures. This result indicates that the aspirin did not react with the bulk water but with active water adsorbed on the internal pore surfaces of PILM.

Spectral properties of mixtures of montmorillonite and dark carbon grains: Implications for remote sensing minerals containing chemically and physically adsorbed water

The spectral properties from 0.4 to 3μm of montmorillonite plus dark carbon grains (called opaques) of various sizes are studied as a function of the weight fraction of opaques present. The reflectance level and band depths of the 1.4‐, 1.9‐, 2.2‐, and 2.8‐μm water and/or OH absorption features are analyzed using derived empirical relationships and scattering theory. It is found that the absorption band depths and reflectance level are a very nonlinear function of the weight fraction of opaques present but can be predicted in many cases by simple scattering theory. The 2.8‐μm bound water fundamental band is the most difficult absorption feature to suppress. The overtone absorptions are suppressed a greater amount than the fundamental but are still apparent even when 10–20 wt% opaques are present. Thus the band depth ratio of one overtone by the fundamental or other lower overtone varies as a function of the weight fraction of opaques present. The relationships observed and the simple scattering theory presented show that quantitative compositional remote sensing studies are feasible for surfaces containing complex mineral mixtures. The question of the uniqueness of quantitative remote sensing is discussed.

Mineralogy of the Major Soils of the Gezira Scheme (Sudan)

AbstractThe major soil series comprising the Gezira scheme are Hosh, Suleimi, and Laota. These soils are calcareous, dark brown to grayish brown clays with low organic matter contents (< 1%). The mineralogical properties of these soils were studied by X‐ray diffraction (XRD), dissolution, and Ca/Mg and K/NH4 cation exchange capacities. Some complementary data were obtained using infrared (IR) spectroscopy. The results of the study reveal that these soils have similar sand, silt, and clay mineralogy. The sand fractions are composed of quartz, plagioclase, K feldspars, anatase, and amphiboles. The silt fractions contain, in addition to the above minerals, kaolinite, mica, and chlorite. The coarse clay is composed of chlorite, kaolinite, smectite, plagioclase and K‐feldspars, quartz, and mica. The fine clay is predominantly smectite (a mixture of montmorillonite and beidellite), kaolinite, and mica. Calcite is the dominant mineral in the gray hard nodules. The uniform physiographic position and similar mineralogy of these soils suggest that they have a common origin. The similarity in mineralogical composition to that of the recent sediments of the Blue Nile and its tributaries, supports the contention that the Gezira soils have inherited their mineralogical properties from the source area of the sediments in Ethiopia.

Geochemistry of the Dakota Formation of Northwestern New Mexico: Relevance to Radioactive Waste Studies

The Dakota Formation of the San Juan Basin in northwestern New Mexico consists predominantly of well-cemented sandstones and arenaceous mudstones. Clay mineral-rich rocks, derived from volcanic ash, are mapped as bentonites. The likely physical conditions during burial were temperatures between 35 to 60/sup 0/C and a pressure of about 0.5 kbar. X-ray studies reveal a mixture of montmorillonite, kaolinite, illite, and mixed layer clay minerals. The typical cation exchange capacities range from 20 to 40 meq/100 g for most samples. Radiometric age determinations of clay minerals by the K-Ar method yield 90 to 94 millions of years before present (MYBP) and Rb-Sr ages yield 93 + or - 8 MYBP. These dates agree with paleontological ages and indicate closed-system conditions for potassium, argon, rubidium, and strontium in these rocks. Closed-system conditions for cesium are inferred based on its greater retentivity than rubidium and potassium in clay-rich rocks. Neutron activation analysis (NAA) of the Dakota samples indicates normal lanthanide abundances and distribution in the bentonitic rocks; local lanthanide enrichment is noted where local uranium accumulations are noted. The uranium has been derived from several sources and fixed in the Dakota Formation at various times from roughly 60 to near 0.25 MYBP.more » The chalcophile elements copper, antimony, and lead are often fixed with uranium in organic-rich rocks and apparently have not migrated since fixation, even under oxidizing conditions. No mobilization for the lanthanides and barium is noted either. Collectively, the radiometric ages and NAA data indicate the bentonite and bentonite-sand mix to be suitable for overpack in radioactive waste repositories.« less

Hydrothermal Interactions of Cement or Mortar with Zeolites or Montmorillonites

ABSTRACTConcretes, grouts, clays and/or zeolites are candidate borehole, shaft or tunnel plugging materials for any nuclear waste repository. Interactions between these plugging materials may take place under mild hydrothermal conditions during the life of a repository. Class H cement or mortar (PSU/WES mixture) was reacted with one of two montmorillonites, clinoptilolite or mordenite at 100° and 200°C for different periods under a confining pressure of 30 MPa. The solid reaction products were characterized by x-ray powder diffraction and scanning electron microscopy after the hydrothermal treatments. When zeolites were in contact (not intimate mixture) with class H cement, they did not seem to alter but clinoptilolite altered to analcime, and mordenite became poorly crystalline in the presence of mortar (containing NaCl) at both 100° and 200°C. When cement or mortar was intimately mixed with zeolites or montmorillonites and reacted hydrothermally, the reaction resulted in the formation of Al substituted tobermorite (11Å type) in all cases (this type of reaction is expected at the interface) at both 100° and 200°C. The mechanism of tobermorite formation includes the decomposition of zeolites or montmorillonites in the presence of alkaline (pH ≃ 12) cement or mortar and recrystallization to form Al substituted tobermorite. Cesium sorption measurements in 0.01N CaCl2on the reaction products revealed that selective Cs sōrption increased in most cases, even though little or none of the original zeolites and montmorillonites remained in the products. For example, Cs sorption Kd(mL/g) increased from 80 in the untreated mortar + Ca montmorillonite mixture to 1700 in the interaction product which is Al substituted tobermorite. Thus, we discover here that Al substituted tobermorite has good selectivity for Cs.