Swelling Of Montmorillonite Research Articles

In situ neutron diffraction analysis of the influence of geometric confinement on crystalline swelling of montmorillonite

The swelling properties of a bentonite MX-80 and a Na montmorillonite obtained from MX-80 purification were analyzed as a function of relative humidity in free and constrained conditions. Gravimetric and XRD techniques were used to study the hydration of powder and compacted pellets in non confined conditions whereas hydration under constrained conditions was investigated in situ by neutron diffraction using a cell specifically designed for the present study. MX-80 bentonite and purified montmorillonite were compacted to an apparent density of 1.7 and equilibrated at various relative humidities using P2O5 and solutions saturated with different salts allowing to work in a wide range of relative humidity between 0 and 0.98.At low relative humidity, the hydration of montmorillonite is similar in free and constrained conditions. For relative pressures higher than 50%, swelling in constrained pellets deviates from that observed for free pellets. Reorientation phenomena of clay layers were also observed for bentonite and montmorillonite starting at 65% RH. At 98% RH, two well-defined basal spacings were obtained in the case of confined bentonite. The major peak corresponds to three-layer hydrates (18.6 Å) and the second one to two-layer hydrates (16 Å). In contrast, only the latter peak is observed when hydration is realized in free geometrical conditions. In the case of Na montmorillonite, for the same relative humidity, the confinement cell did not resist swelling pressure. This was explained by the fact that, for the 1.7 density, porosity was too small to allow the formation of the three layer hydrates to compensate for water swelling pressure.

Swelling Inhibition by Polyglycols in Montmorillonite Dispersions#

In this study the inhibition by polyglycols of the swelling of montmorillonite in aqueous solutions was investigated through linear swelling and particle size distribution experiments. With addition of KCl, polyglycol adsorbing on montmorillonite can complex with K+ and promote clay particles aggregation and efficiently decrease the swelling of montmorillonite. The more hydrophobic copolymer of ethylene oxide and propylene‐oxide induces greater aggregation than the homopolymer of ethylene oxide. #In this paper, polyglycols describe a kind of water soluble nonionic polymer, including homopolymers and copolymers of ethylene oxide and propylene oxide.

Porewater chemistry in compacted re-saturated MX-80 bentonite

Bentonites of various types are being investigated in many countries as backfill materials in high-level radioactive waste disposal concepts. Being able to understand the chemistry of the porewater in compacted bentonite is very important since it is critical to predicting radionuclide solubilities and to the synthesis of sorption data bases, and hence to repository safety studies. In this paper, porewater compositions in compacted bentonites are calculated, taking into consideration such factors as montmorillonite swelling, semi-permeable membrane effects, very low “free water” volumes, and the highly effective buffering characteristics of the exchangeable cations and the amphoteric edge sites. The former buffer the cation concentrations and the latter fix the pH in the porewater of a re-saturated bentonite. The above considerations are used in conjunction with previously measured physico-chemical characterisation data on MX-80 powder to calculate porewater compositions in compacted bentonites. For the MX-80 material specified, the porewaters calculated for initial dry densities between 1200 and 1600 kg m −3 had relatively high ionic strengths (I ∼0.3 M), similar cation concentrations and a pH equal to 8.0. The porewaters changed from being Na 2SO 4-rich at 1200 kg m −3 to a NaCl/Na 2SO 4 type water at 1600 kg m −3.

Monte Carlo simulations of Ca–montmorillonite hydrates

Monte Carlo simulations are performed to investigate the role of the divalent cation Ca on the stability and swelling of montmorillonite. Constant stress simulations (NPzzT ensemble) are used to predict the basal spacing as a function of the water content in the interlayer, and constant chemical potential simulations (μVT ensemble) are used to find the more stable basal spacings of the clay–water systems. Two model clays are considered in this work, namely, Otay and Wyoming montmorillonites. It is found that the equilibrium basal spacings for Otay montmorillonite are D1=11.9 Å and D2=14.4 Å. For Wyoming montmorillonite they are D1=12.2 Å and D2=14.7 Å. It is also found that montmorillonites develop one layer of water at D1, and two layers of water at D2. We found that, for all the water contents considered here, the cations are hydrated.

The Limited Swelling of Montmorillonite

The attraction forces responsible for the occurrence of limited swelling of montmorillonite having divalent counterions were evaluated from (a) the electrostatic attraction between the negative charges of one surface and the effective charges of the counterions of the other interlayer surface and (b) van der Waals attraction between the two interlayer surfaces. Both methods of calculation almost account for the force required to maintain limited swelling of the clay. It is found that a Hamaker constant of 2.25 × 10−13erg in place of 2.72 × 10−13erg and a counterion charge screening factor of 0.82[1 − exp(−κx)] in place of [1 − exp(−κx)] reproduce the true value of the attraction force.

Construction and Application of Clay-Swelling Diagrams by Use of XRD Methods

Clay swelling is one of the major causes of formation damage in hydrocarbon reservoirs and also can cause many drilling operations problems in shaly formations. Clay swelling is controlled primarily by the compositions of aqueous solutions with which the clay comes into contact. This paper presents a method to construct clay-swelling diagrams that can be used to determine the compatibility between swelling clays and aqueous fluids

The effect of temperature on the swelling of montmorillonite

AbstractThe effect of temperature on the swelling of clay was studied by determining (1) the relation between the interlayer spacing, λ, and the swelling pressure,Π, at different values of the temperature, T, using the method of Viani et al. (1983) as modified by Wu et al. (1989); (2) the relation between λ and T at different values of Π; and (3) the relationship between Π and mw/mc, the mass ratio of water to clay, at different values of T using the method of Low (1980). The results showed that λ was essentially independent of T but that mw/mc decreased slightly with T at any value of Π. Such results are not consistent with electric double-layer theory. Therefore, it was concluded that the decrease in mw/mc with increasing T was due primarily to the thermal breakdown and consequent loss of water from the larger pores outside of the interlayer region.

The Prevention Of Resalinization The Reclamation Of Saltwater Spill Sites

Abstract After the initial treatment of a saltwater spill site has effected a reduction of soil salinity, a resalinization due to capillary rise ofsoil water can occur in certain circumstances. As an alternative to successive and costly chemical retreatments, prevention of resalinization by means of an organic trash covering of the spill site was investigated in a field study. The results suggest that such a cover prevents serious resalinization of the topsoil, in contrast to untreated sites, although the trend in sodicity is not as clear. Uneven coverage of the soil can to some extent be tolerated. Some implications for field treatment techniques are discussed. Introduction The initial effect of a saltwater spill on a mineral soil is to exchange calcium, magnesium and other ions for sodium ions, primarily on the surfaces of clays and organic matter(l,2). A subsequent freshwater flush of the soil may then cause the swelling of montmorillonite and dispersion and transport of kaolinite, among other effects, resulting in a permeability reduction. The physical chemistry governing this process is identical to that encountered in formation damage to freshwater sensitive reservoirs. A parameter commonly in use in soil science is the sodium adsorption ratio Equation (Available In Full Paper) with aqueous concentrations of ions expressed in millimole per litre (if milliequivalents per litre are used, the mean, rather than the sum of concentrations in the denominator, needs to be used). Impairment of permeability is to be expected if the S.A.R. exceeds 15(3), although sometimes problems are encountered at values greater than 8. The standard approach to reclamation is the addition of calcium salts such as calcium sulphate(l) or the more soluble calcium nitrate (2), preferably prior to the next rain or snowfall (Organic forest soils are an exception, and freshwater flushing is in most cases indicated(4).) The intent of the calcium amendment is to reverse the ion exchange process. In many cases, however, drainage in the spill area is poor, and the installation of a drainage system, with recovery and disposal of the sodium contaminated drain water, is not always a practical alternative. In such cases, therefore, reclamation programs rely on chemical amendment of the spill site soil, with attempts at early establishment of salt-tolerant vegetation, and the expectation of relatively slow drainage of the contaminating sodium salts. Some years ago, we reported the salinity reduction of the topsoil in a spill site by calcium nitrate amendment and irrigation(2). The site was identified as 9-16-6-11 W2M, in the Midale field (southeastern Saskatchewan) operated by Shell Canada Ltd. The soil electrical conductivity data prior to this treatment ranged from 29 000 - 56 000 microsiemens per centimetre (µS.cm− I)Treatment and leaching reduced this figure to 6900 µS.cm−I. However, by the following spring, it was found that the electrical conductivity had risen to 18 200 µS,cm− I, and the very dry following summer season did not permit a reduction to less than 11 000 µS.cm−l.

Direct measurement of the relation between interlayer force and interlayer distance in the swelling of montmorillonite

Oriented gels of eight Na-montmorillonites having values of the surface charge density, σ, ranging from ≈ 28,000 to 56,000 esu/cm 2 were confined in a close chamber between a N 2-gas piston and a porous ceramic plate in contact with a solution of 10 −4 N NaCl. Successively higher pressures up to 6.9 bars were applied by the N 2-gas piston while the NaCl solution was maintained at atmospheric pressure. After equilibration at each applied pressure, the c axis spacing of the silicate layers was measured by X-ray diffraction. Subsequently, the thickness of a silicate layer was subtracted from this spacing to obtain the corresponding interlayer separation, λ. Since, at equilibrium, the swelling pressure, II, is equal to the applied pressure, it was thus possible to determine II as a function of λ for each montmorillonite. We found that II is an exponential function of 1 λ . Also, at any value of II, the value of λ is independent of the value of σ. Neither of these findings is consistent with the double-layer (i.e., osmotic) theory of swelling. Therefore, an additional force, which is the dominant force at the observed values of λ, must be responsible for swelling. In view of an empirical relation that exists between II and any property of the water in the swollen system, we postulate that this additional force results from the in-depth perturbation of the water by the surfaces of the montmorillonite layers.

Comparison of the Inhibitory Action of KCl and Guanidine Hydrochloride Solutions on Montmorillonite Swelling

Abstract This study compares the effectiveness of potassium chloride with guanidine chlorhydrate in the prevention of clay swelling. The results given on various swelling tests on calcic montmorillonite led to the conclusions that (1) guanidine chlorhydrate is more effective than potassium chloride, especially in low concentrations, and (2) water immersion of samples treated by both solutions shows the permanent feature of the inhibitive action of guanidine chlorhydrate in swelling on one hand and the important increase in swelling of immersed samples treated by potassium chloride on the other. The viscosity measure of montmorillonite suspensions, before and after solution ion elimination by dialysis, confirms these observations.

The Physical Swelling of Clays in Solvents

AbstractThe physical swelling of two illitic clays has been measured, at zero matric potential, in a series of organic solvents with different functional groups. The results show that a significant linear correlation exists between the observed swelling and the static dielectric constant of the liquid. This behavior is compared with the intracrystalline swelling of montmorillonite and is discussed in relation to the mechanism of swelling of clay systems.

Swelling of montmorillonite containing coordination complexes of amines with transition metal cations

Swelling of montmorillonite is inhibited by interlayer organic ammonium ions. The effect of interlayer coordination complexes of ethylene diamine (En) with transition metals depends on the nature of the cations. When a fraction of interlayer Cu2+ or Hg2+ ions is chelated by two En ligands, swelling is inhibited. Zn2+, which forms [ZnEn3]2+ complexes in aqueous solution, coordinates a maximum of two En ligands in interlayer space and permits swelling of the clay up to 1.53 nm. The effect of [NiEn2]2+ and [CdEn2]2+ is similar, whereas [NiEn3]2+ and [CdEn3]2+ ions restrict expansion to about 1.42 nm. Other chelating amines behave similarly, while nonchelating amines sorbed by montmorillonites saturated with complexing cations are hydrolyzed and swelling of the clay is prevented by the formation of ammonium ions.

Change of b-Dimension with Swelling of Montmorillonite

AbstractThe effect of swelling on the b-dimension of Na-saturated, Upton, Wyoming montmorillonite was re-examined using powdered silicon as an internal standard. After being corrected with reference to the internal standard, the b-dimension did not increase through the entire range of swelling as reported previously. It increased up to a water content of ~3.0g/g montmorillonite and remained constant thereafter. However, the diffraction peak of the internal standard shifted towards lower angles at higher water contents. This shift was attributed to a relaxation of the wetter samples away from the knife edge of the diffractometer. Presumably, a similar relaxation occurred in the earlier study and was responsible for the apparent increase in b-dimension at water contents above ~3.0g/g.The b-dimension of Upton montmorillonite saturated with different cations was determined using powdered silicon and a colloidal quartz impurity as internal standards. The water content at maximal swelling decreased as the b-dimension increased.

Swelling of Montmorillonite in Polar Organic Liquids

AbstractThe crystalline and osmotic swelling of Na-, Cs-, Mg- and Ca-montmorillonite has been measured in dimethyl sulphoxide and in formamide, N-methyl formamide, dimethyl formamide, N-methyl acetamide and dimethyl acetamide. These liquids have similar dipole moments but their relative permittivities vary appreciably from values less than water to values greater than water.Na-montmorillonite exhibits osmotic swelling (diffuse double layer development −d(001) ≫ 19 Å) in formamide and N-methyl formamide and Cs gives osmotic swelling behavior in formamide. Cs-montmorillonite in the crystalline swelling region give spacings greater than those found for water with all liquids. Mg- and Ca-montmorillonite did not give spacings greater than 19 Å in any of the liquids studied.The swelling behavior of montmorillonite is affected by relative permittivity but for liquids with a similar relative permittivity methyl substitution in the molecule may prevent the development of diffuse double layers on the particle surfaces.

Flocculation of Bentonite Suspension under Suppression of Swelling with Inorganic Electrolyte

The flocculation behavior of particles iR two kinds of bentonite suspensions has been studied in the presence and the absence of polymer flocculants. Suspension A was prepared by dispersing bentonite in pure water and subsequent addition of iRorganic electrolytes such as Ca(OH)2 and CaCI2. Suspension B was prepared by dispersing bentonite directly in inorganic electrolyte solution.Both the settling and the filtration rates of B were higher than those of A. An extreme difference of settling rate was found between A and B, The addition of polymer flocculant greatly increased settling and filtration rates, but the difference in flocculation behavior between A and B still remained. High settling rate (7 cm/min) was obtained with the addition of Ca(OH)2to 250 ppm Ca and Separan NP 20 to 2 ppm in the case of B (Fig, 7), When kaolin, silica powder, pettery clay or silt rich clay containing no montmorillontite was substituted for bentonite, no appreciable difference was observed in the flocculatioR behavior between two kinds of suspensions. On the other hand, the flocculation behavior of suspensions of coal debris which contained considerable amounts of montmorillonite changed according to the preparation method of suspensions as was the case for bentonite (Fig.2 and Fig.3), Above experimental results suggest that the addition of an adequate amount of inorganic electrolyte such as Ca(OH)2 to the water for dressing or washing of coal, gravel and the like containing montmorillonite facilitates the flocculation treatment of the waste eMuent from these processes through the resultant suppression of the swelling of montmorillonite.

The effect of exchangeable alkylammonium ions on the swelling of montmorillonite in water

AbstractA study has been made of the influence of adsorbed alkylammonium ions on the water sorption and swelling of Na+ and Ca++ montmorillonite, under controlled conditions of temperature and suction. The water uptake and extensive crystalline swelling of Na+ montmorillonite decrease as the proportion of exchangeable alkylammonium/ammonium ions increases. This decrease is more associated with the degree of surface coverage than with the degree of saturation of the exchange sites by the alkylammonium ions. These observations are explained in terms of binding of the organic cation by the clay surface and the collapse of diffuse double layers on interlamellar surfaces. Differences in water uptake betwen complexes saturated with different alkylammonium ions are attributed to differences in the structural arrangement of the clay crystals in the swollen state. Similarly, there is a continual slight decrease in the water uptake and swelling of Ca++ montmorillonite as the amount of alkylammonium ions present increases. However, for alkylammonium ions containing less than five carbon atoms and when only about half of the exchangeable Ca++ ions have been replaced by the organic ions, extensive crystalline swelling sometimes takes place. When this occurs, it is suggested that the alkylammonium ions disrupt the regularity of the water network initially associated with the Ca++ ions, enabling these to participate in the formation of diffuse double layers in the interlamellar space.

Some Physicochemical Properties of the Montmorillonites

The swelling, moisture sorption, particle size, cation-exchange, and drug adsorption properties of selected montmorillonites were studied. The swelling of montmorillonite was found to depend on both adsorptive and osmotic phenomena. The study of the sorption of alkaloidal drugs by the clay showed that brucine was sorbed by both adsorption and ion-exchange reactions, forming a monomolecular layer on the interior surface of the clay; methapyrilene and triethylamine were sorbed by an ion-exchange reaction; and niacinamide was neither adsorbed nor ion-exchanged.

Effect of Hydration of Montmorillonite on the Permeability to Gas of Water-Sensitive Reservoir Rocks

Abstract Laboratory research has been conducted to evaluate the effect of clay hydration on the permeability to gas of water-sensitive reservoir sands. samples of a sandstone containing trace amounts of montmorillonite and a sample of montmorillonite were studied in the laboratory to determine whether swelling or dispersion was the cause of permeability reduction in these samples. Helium, containing various amounts of water vapor, was used to hydrate the clay minerals and to determine the gas permeability at various stages of clay hydration. The amount of water adsorbed by the samples using this method is small. The nonwetting-phase permeability at higher water saturations was investigated by saturating the samples with water and measuring the permeability to humid helium while decreasing the water saturation. Relative-permeability curves obtained from results of these procedures were used to estimate the effect of the swelling of trace amounts of montmorillonite on the permeability of the samples. Most of the damage to the permeability when reservoir sands containing trace amounts of montmorillonite are exposed to fresh water is due to dispersion and movement of clays. Blockage of pores by the increased volume of expanded montmorillonite is believed to result in permeability damage that is small in comparison to the observed damage to the samples tested. Introduction Studies have shown that permeability is severely damaged when sands containing only small amounts of montmorillonite are contacted by fresh water. When samples of sands containing large amounts of montmorillonite are placed in fresh water in the laboratory, these samples may completely disintegrate, forming an unconsolidated mass of larger volume than that occupied by the dry sample. In this case, it is apparent that the swelling of montmorillonite has destroyed the pore structure of the sand. If only a trace of montmorillonite is present in a sand, samples may remain intact when saturated with water, although the permeability to water is a small fraction of the gas permeability of the dry sample. Many workers in the field of water sensitivity have attributed this reduction in permeability to the blocking of pores and reduction of pore size by the increased volume occupied by expanded montmorillonite, if the sand contains a detectable amount of montmorillonite or mixed-layer clay containing montmorillonite. Logically, the smaller amount of montmorillonite present in a sand, the smaller should be the effect of montmorillonite swelling on permeability; however, the quantity of montmorillonite sufficient to cause severe damage by swelling is not known. Although hundreds of samples have been tested in our laboratory, no correlation has been established between the amount of montmorillonite in samples and the permeability reduction caused by fresh water. To many petroleum engineers, the phrase "clay swelling" is synonymous with "water sensitivity", or "permeability reduction" implying that any formation damage due to the hydration of clays is caused by swelling. Although all clays adsorb water on their surfaces, montmorillonite is the only clay mineral commonly found in reservoir rocks which adsorbs water between intercrystalline layers, resulting in expansion of the clay particle. As montmorillonite swells, the first few layers of water adsorbed between platelets are strongly held and well oriented, and the montmorillonite retains its crystalline structure, although expanded. As swelling of sodium montmorillonite continues, the platelets become farther apart and the forces orienting the platelets in the crystalline structure become weaker, resulting in a less orderly orientation of platelets. In an abundance of water, small groups of platelets may become detached from the original montmorillonite particle and may be dispersed throughout the water phase. Because of its swelling properties, sodium montmorillonite is very easily dispersed in water. Particles of other clay minerals, such as illite and kaolinite may also be dispersed in water, causing water sensitivity of sands not containing montmorillonite. The presence of an immobile layer of water adsorbed on the surface of clays has been considered a possible cause of the low permeability to water of dirty sands. Grim states that the thickness of the layer of immobile water held by sodium montmorillonite is three molecular layers or 7.5 A (angstroms), with some orientation of water extending to 100 A. Assuming a very thick, immobile water layer adsorbed on the surface of a pore represented by a capillary tube, the maximum effect of the water layer on permeability can be calculated. Using a pore radius of 10(-4) cm and an immobile water layer of 50 A, the calculation shows the permeability to be reduced only 2 per cent. Similar calculations can be used to show that the effect of electro-osmotic counterflow is of the same order of magnitude as that of bound water. JPT P. 1213ˆ

Low-Angle X-Ray Diffraction Studies of the Swelling of Montmorillonite and Vermiculite

AbstractVarious workers have studied the mechanism of swelling of Na-montmorillonite and have demonstrated that its ability to swell is due to water penetrating between the individual silicate sheets. In the present study intraerystalline swelling was followed by diffraction techniques which enabled the movement of the silicate sheets with respect to one another to be measured as a function of electrolyte concentration, with or without an externally applied load. The observations have been made on oriented flakes of Na-montmorillonite and single crystals of Li-vermiculite.Qualitatively the minerals behave similarly when swollen in salt solutions. They both show an initial stage of crystalline swelling, after which there is an explosive increase to the gel state, and then the distance apart of the silicate sheets increases linearly with C-½, where C is electrolyte concentration. Quantitatively, however, their swelling is very different, particularly after the “explosion”, where vermiculite generally gives higher spacings than montmorillonite. There are two other important differences in the swelling of montmorillonite and vermiculite. Firstly, while the swelling of vermiculite appears to be reversible both with respect to electrolyte concentration and applied pressure, the swelling of montmorillonite shows a marked hysteresis. Secondly, in montmorillonite, swelling depends very strongly on pH or chemical treatment.There is little doubt that the development of diffuse “double layers” gives rise to repulsive forces, which cause the silicate sheets to move apart. Van der Waals’ forces have been regarded as providing attraction, but it is found that, at the observed interlayer separations, the magnitude of these attractive forces is inadequate to balance repulsion, both in montmorillonite and vermiculite.The present results demonstrate that in vermiculite swelling proceeds until the interlayer separation causes the repulsion between sheets to drop to a value of ~ 2.5 × 104 dyn/cm2. This attractive force, which limits swelling, appears to be independent of sheet separation and electrolyte concentration. In montmorillonite swelling is opposed by edge-to-face bonds between sheets, whose number and strength can be controlled by chemical treatment. These bonds act to resist any displacement of the sheets, either swelling or contraction. This mechanism is compatible with the observed swelling behavior of montmorillonite, and explains the differences between the swelling of this mineral and that of vermiculite where, because the sheets are considerably larger, the force arising from edge-to-face bonds is small or absent.

Swelling of Calcium Montmorillonite

WARKENTIN et al. 1, following up earlier work of Schofield2, Bolt and Miller3, and others, showed that swelling pressures developed by suspensions of sodium montmorillonite on an ultra filter could be predicted satisfactorily from a diffuse ion layer model based on classical Gouy–Chapman theory. Warkentin et al. also reported results of preliminary experiments with calcium montmorillonite for which the same model appeared to be inappropriate. A significant result was the decrease in magnitude of reswelling observed as the peak pressure applied to the sample increased. They concluded that forces not taken into account in the calculation must be present. Recently, Aylmore and Quirk4, Greacen5 and others have published discussions of these results which may now require reconsideration in view of further studies of calcium montmorillonite swelling.