Relationship of Swelling and Swelling Pressure on Silica−Water Interactions in Montmorillonite (original) (raw)
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Effect Of Clay-Water Interactions On Swelling In Montmorillonite Clay
This paper describes effect of clay-water interactions on swelling of montmorillonite using a new controlled uniaxial swelling (CUS) cell developed by the authors. Using the CUS cell, a simultaneous measurement of swelling and swelling pressure is done. Undisturbed clay samples at well defined swelling (0%-75%) were removed from the CUS cell and analyzed using scanning electron microscopy and fourier transform infrared (FTIR) spectroscopy and also orientation dependant micro-attenuated total reflectance (ATR) spectroscopic investigations. Significant changes in the silicate (Si-O) stretching region (1150 to 950 cm -1 ) have been observed with changes in swelling and orientation. Our results indicate that the reduced particle size with increased swelling is related to increased misorientation of the clay platelets. At 0% swelling the clay platelets are most oriented and have largest particle size. The rearrangement of clay platelets as seen in the orientation dependant spectra are a direct result of the breakdown of the clay particles with increased hydration resulting from increased swelling.
Journal of Rock Mechanics and Geotechnical Engineering, 2018
Swelling clays are found extensively in various parts of the world, and sodium-montmorillonite (Na-MMT) is the main constituent of an expansive clay mineral. In this work, the swelling behavior of Na-MMT clay with a wide range of organic fluids, high polar through low polar fluids, is studied using a combination of Fourier transform infrared (FTIR) technique and molecular dynamics (MD) simulations. The construction of the representative clayefluid models is carried out, and the nature of nonbonded interactions between clay and fluids is studied using MD. Our FTIR and MD simulations results suggest the significant nonbonded interactions between Na-MMT clay and polar fluids, such as formamide and water. The nonbonded interactions of Na-MMT with methanol and acetone are significantly less than those in Na-MMT with polar fluids. The interactions of the fluids with various entities of the clay such as SieO, FeeOH, MgeOH, and AleOH captured via the spectroscopy experiments and modeling provide a finer understanding of the interactions and their contributions to swelling. The MD simulations are able to capture the band shifts observed in the spectra obtained in the spectroscopy experiments. This work also captures the conformations of interlayer sodium ions with formamide, water, methanol, and acetone during swelling. These nonbonded interactions provide insight into the molecular mechanism that the polarity of fluids plays an important role in the initiation of interlayer swelling, alteration in the orientations, and evolution of microstructure of swelling clays at the molecular scale.
Applied Clay Science, 2016
A specific oedometer cell has been set up to measure the swelling pressure of compacted montmorillonites at constant volume and to concomitantly visualize the evolution, upon wetting, of how the microstructure is organised through X-ray microtomography. The swelling pressure experiments were conducted with solvents of various natures. In addition to conventionally used water and saline solutions, we used an organic solvent (methyl methacrylate-MMA). We chose this to explore the effect of its different physical and chemical properties, and to differentiate the respective roles of crystalline and osmotic pressures on macroscopic swelling behaviour. The results, which combined both swelling pressure measurements and quantification of microstructure evolution upon hydration for the two different solutes, give sound understanding on the development of osmotic and/or crystalline swelling and their relative impact both on the microstructure and on the magnitude of the macroscopic swelling pressure of compacted montmorillonites.
Free energy, energy, and entropy of swelling in Cs–, Na–, and Sr–montmorillonite clays
The Journal of Chemical Physics, 2004
A Monte Carlo method for grand canonical and grand isoshear ensemble simulations has been used to characterize the free energy, energy, and entropy of clay mineral swelling. The Monte Carlo approach was found to be more efficient at simulating water content fluctuations in the highly constrained clay environment than a previously developed molecular dynamics method. Swelling thermodynamics calculated for Cs-, Na-, and Sr-montmorillonite clays indicate a strong dependence of swelling on the interlayer ion identity, in agreement with various experimental measurements. The Sr clay swells most readily, and both the Na and Sr clays prefer expanded states ͑two-layer hydrate or greater͒ when in contact with bulk water. In contrast, swelling is inhibited in the Cs clay. Differences in swelling behavior are traced directly to the tendency of the different ions to hydrate. The swelling free energies are decomposed into their energetic and entropic components, revealing an overall energetic driving force for the swelling phenomena. Entropic effects provide a smaller, mediating role in the swelling processes. The results provide a unique molecular perspective on experimentally well-characterized swelling phenomena.
Relation Between Crystal-Lattice Configuration and Swelling of Montmorillonites*
Clays and Clay Minerals, 1970
Prompted by Foster's observation that free swelling is related to octahedral substitution, the authors determined the free swelling of six Na-montmorillonites with different amounts of octahedral and tetrahedral substitution. They found that the montmorillonites exhibited marked differences in free swelling. These differences were not related to differences in cation exchange capacity. Nor were they related to differences in ~ potential, which is a criterion of cation dissociation. Further, calculations indicated that they could not be accounted for by differences in double-layer repulsion or van der Waals attraction. Therefore, to see if dimensional changes produced by isomorphous substitution were responsible, free swelling was plotted against the b-dimension of the clay structure, which was calculated from its mineralogical composition. The result was a straight line with a negative slope. A similar result was obtained with Foster's data. In addition, free swelling was plotted against the degree of tetrahedral rotation in the clay structure, which was also calculated from its mineralogical composition. The result was a family of nearly parallel straight lines that were distinguished from each other by the amount of tetrahedral AI 3+ in the clays identified with them. These results led to the proposal that the clay surface acts as a template for the structure of the adjacent water and that, as the configuration of the surface changes, the water structure changes accordingly. This causes a change in the free energy of the water and, hence, in the swelling of the clay.
Swelling transition of a clay induced by heating
Scientific Reports, 2012
Clays are of paramount importance for soil stability, but also in applications ranging from oil recovery to composites and hydrogels. Generically, clays are divided into two subclasses: macroscopically swelling, 'active' clays that have the capacity for taking up large amounts of water to form stable gels, and 'passive' or non-swelling clays; the former stabilize soils whereas the latter are known to lead to landslides. However, it has been unclear so far what mechanisms underlie clay swelling. Here, we report the first observation of a temperature-induced transition from a passive to an active, swelling clay. We propose a simple description of the swelling transition; while net attractive interactions are dominant at low temperatures so that the clay particles remain attached to each other in stacks, at higher temperatures it is energetically favourable for the clay to swell due to the entropy that is gained by counterions which are liberated during swelling.
Journal of Colloid and Interface Science, 2013
Important structural modifications occur in swelling clays upon water adsorption. The multi-scale evolution of the swelling clay structure is usually evidenced by various experimental techniques. However, the driving force behind such phenomena is still not thoroughly understood. It appears strongly dependent on the nature of the interlayer cation. In the case of montmorillonites saturated with alkaline cations, it was inferred that the compensating cation or the layer surface could control the hydration process and thus the opening of the interlayer space, depending on the nature of the interlayer cation.
Effect of clay–water interactions on clay swelling by X-ray diffraction
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2007
Clay swelling is a very common phenomenon observed in sedimentary rocks and soils. It is one of the major causes for permeability reduction in hydrocarbon reservoirs. The aim of this work is to characterize the swelling behavior of bentonite and of two clays from Brazilian petrolific basins. X-ray diffraction (XRD) was used to quantify the swelling characteristics of these clays under contact with salt solutions, as in the reservoir. The measurement of interplanar spacing of the swollen clay was measured 24 h after the preparation of the paste. Their diffractograms displayed well-defined peaks at low angles, even for (0 0 1) d-spacing values larger than 50 Å . Two types of mechanisms for clay swelling were identified: crystalline swelling (limited d-spacing increase) and osmotic swelling (large d-spacing values). The critical salt concentration (CSC) value, i.e., the salt concentration at which clay changes from crystalline to osmotic swelling, was obtained. The method used in this work allows one to determine the compatibility between reservoir clays and foreign fluids and to avoid the osmotic swelling conditions that can cause permeability reduction in natural hydrocarbon reservoirs. r
Journal of Physical Chemistry C, 2007
The key feature of swelling clays such as montmorillonite, in contrast with the nonswelling clays, is their ability to adsorb water in the interlayer space. This interlayer water interacts with the interlayer cations or with the silicate layer surface inside the interlayer space, or with both. However, no direct experimental technique offers the possibility to determine separately these two contributions. In order to determine the hydration energy for interlayer alkali cations, we use a combination of electrostatic calculations of the surface energy and measurements of immersion heats in clays. The results show that Li + and Na + cations are characterized by a strongly exothermic hydration energy in the interlayer space, in contrast with K + , Rb + , and Cs + which have a much lower hydration energy in the interlayer space. The extreme situation is that of Cs + , for which an endothermic hydration energy value is obtained. These trends are in good agreement with results from molecular modeling calculations and consistent with the evolution observed in the water adsorption isotherms. The hydration energy of the silicate layers was also calculated, and the total driving force for hydration in swelling clays could therefore be determined. For Li +-and Na +-montmorillonite, the hydration of cations is clearly the main contribution to the overall driving force for the hydration of clay. On the contrary, hydration of the silicate layers plays the most important role in the hydration of montmorillonite exchanged with the larger cations such as K + , Rb + , and Cs +. These results provide a physical basis for the differences observed in macroscopic swelling behavior between Li +-and Na +-montmorillonite, on one hand, and K +-, Rb +-and Cs +-montmorillonite, on the other hand.
Applied Clay Science, 2014
Exceptional water retention properties make compacted clays and clayrocks attractive materials in waste management applications, e.g. as buffer materials and barrier formations for radionuclide release in geological disposal of spent nuclear fuel elements. Consisting of particles with a very high aspect ratio, clay materials exhibit significant structural anisotropy with potential implications on their performance. In this work, the micron-scale and nanometer-scale anisotropy in compacted calcium montmorillonite and MX-80 bentonite were investigated and quantified under varying humidity conditions; the utilized novel experimental method combines X-ray microtomography (XMT) and small-angle X-ray diffraction to near-simultaneously characterize both the micronscale 3D morphology and mineralogical properties such as clay platelet spacing in platelet stacks (tactoids) and tactoid orientation. Sedimentation during the purification process and lack of accessory minerals were found to induce much stronger orientation in purified Ca-montmorillonite as compared to the MX-80. In highly anisotropic samples, the orientation of microcracks visualized with XMT under low humidity conditions was found to correlate with the local orientation of clay tactoids measured with X-ray diffraction. The proposed experimental method can be applied to a wide range of similar materials, such as shales or samples from clayrock formations.