Dehydration Of Montmorillonite Research Articles

Self-assembly Processes in Hydrated Montmorillonite by FTIR Investigations.

Experimental findings obtained by FTIR and Raman spectroscopies on montmorillonite-water mixtures at three concentration values are presented. To get some insight into the hydrogen bond network of water within the montmorillonite network, FTIR and Raman spectra have been collected as a function of time and then analyzed following two complementary approaches: An analysis of the intramolecular OH stretching mode in the spectral range of 2700–3900 cm−1 in terms of two Gaussian components, and an analysis of the same OH stretching mode by wavelet cross-correlation. The FTIR and Raman investigations have been carried as a function of time for a montmorillonite-water weight composition (wt%) of 20–80%, 25–75%, and 35–65%, until the dehydrated state where the samples appear as a homogeneous rigid layer of clay. In particular, for both the FTIR and Raman spectra, the decomposition of the OH stretching band into a “closed” and an “open” contribution and the spectral wavelet analysis allow us to extract quantitative information on the time behavior of the system water content. It emerges that, the total water contribution inside the montmorillonite structure decreases as a function of time. However, the relative weight of the ordered water contribution diminishes more rapidly while the relative weight of the disordered water contribution increases, indicating that a residual water content, characterized by a highly structural disorder, rests entrapped in the montmorillonite layer structure for a longer time. From the present study, it can be inferred that the montmorillonite dehydration process promotes the layer self-assembly.

Determining the cation exchange capacity of montmorillonite by simultaneous thermal analysis method

A way of determining the cation exchange capacity of montmorillonite by simultaneous thermal analysis is developed using as an example the bentonites of the 10th Khutor deposit (Republic of Khakassia) and the Vodopadnyi area (Sakhalin Island). A correlation is established between the cation exchange capacity of smectite and its weight loss upon heating in the range of dehydration; the enthalpy of dehydration of montmorillonite; and the weight loss and the enthalpy of thermal dissociation of ethylene glycol contained in the interlayer space of the mineral’s crystal structure. These data open up new possibilities for determining the cation exchange capacity of montmorillonite, the most important technological indicator of the natural clay nanomineral.

Combined Salt and Temperature Impact on Montmorillonite Hydration

AbstractBentonite is to be used as a sealing material for long-term storage of radioactive waste. During permafrost periods the buffer may freeze, causing the following: montmorillonite dehydration, ice formation, and pressure build-up that may fracture the surrounding rock. No previous study has been done on freezing of bentonite in saline water. Using small and wide angle X-ray scattering, the present study aimed to increase understanding of the combined impact of salt and temperature on the hydration (swelling) of Wyoming montmorillonite. The basal spacing of the Na-montmorillonite was very dependent on the water content, while this was not the case for the Ca-montmorillonite (after reaching 19 Å). The basal spacing of the free-swelling Na-montmorillonite (34–280 Å) was estimated successfully using simple calculations. During freezing of Na-montmorillonite in NaCl solution, both ice and hydrohalite formed (at -50 and -100ºC). At starting concentrations ≥ 1.5 M the basal spacing was not affected by freezing. During freezing of Ca-montmorillonite in CaCl2 solution, ice formed; antarcticite formed only sporadically. The basal spacing of the Ca-montmorillonite at high NaCl concentrations (>1 M) was greater at -50 and -100ºC (18 Å) than at 20ºC (16 Å). The opposite was observed at low concentrations. This change was attributed to small amounts of salts introduced into the montmorillonite interlayer, hence changing the interlayer water properties. The montmorillonite hydration was also temperature dependent; decreasing temperature increased the hydration (as long as no ice was formed) and increasing the temperature decreased the hydration. This was attributed to the temperature impact on the entropy of the hydration reaction. This observation was also reproduced in an experiment up to 90ºC. A small amount of salt in the groundwater was noted to reduce significantly the potential problem of ice formation in bentonite sealings.

Hydration-phase diagrams and friction of montmorillonite under laboratory and geologic conditions, with implications for shale compaction, slope stability, and strength of fault gouge

Absorption of water into the crystal structure of smectite clays causes a reversible volume increase exceeding 80% and a friction decrease by a factor of three. This behavior can be predicted if clay swelling is approximated as the formation of successive hydration phases and the generalized Clapeyron law is applied. In this study, new data on two standard montmorillonites saturated with sodium and calcium (Na-MM and Ca-MM) are combined with published results to define relative humidity boundaries of proposed phases at 20°C and 1 bar. From molar volumes, the effect of confining pressure is predicted; only phases with an integral number of full interlaminar water layers are stable at high pressures. In contact with liquid water, the number of interlaminar layers is governed by the “effective normal stress” on crystals. Next, vapour pressure measurements at 20°–60°C are used to calculate dehydration enthalpies, from which the effect of geologic temperatures is predicted. Under typical crustal conditions, Na-MM does not fully dehydrate until 7 km depth, and Ca-MM retains one water layer to 11 km. Since the zones of hydrocarbon maturation and montmorillonite dehydration overlap, this effect may play a part in petroleum geology, controlling migration and/or reservoir pressurization. For the first time, the friction of individual hydration phases of montmorillonite has been measured without excess water and within their stability fields. Stable-sliding deformation with negligible rate-dependence and definite work-hardening is observed, but the pressure-dependence is less than in classical friction. Na-MM phases are always weaker than their Ca-MM analogues. In both clays, the addition of the first water layer causes the greatest strength decrease, but two- and three-layer phases are successively weaker. The friction coefficient of three-layer Na-MM at low pressure is near 0.27, consistent with most observed bedding plane rockslides in shales. If Ca-MM is abundant in fault gouge, average friction in the top 10 km of strike-slip and normal faults may be as low as 0.34. Such weak faults would permit major deformation of continental crust by regional shear stresses as low as 27 MPa. This model would also explain the frequent reactivation of ancient faults by later stresses of diverse orientations.

Dehydration of montmorillonite and changes in the ionic composition of ground water in petroliferous basins

Dehydration of montmorillonite and changes in the ionic composition of ground water in petroliferous basins

Gegenüberstellung verschiedener lösungsverfahren zur ermittlung kinetischer parameter anhand von experimentalwerten

The kinetic parameters have been calculated by the differential method according to Freeman and Caroll, the modified differential method, and the integral method according to Coats and Redfern. The calculations have been performed on the base of thermogravimetric data obtained on the recording vacuum thermoanalyzer TA 1 (Mettler). The automatic processing of measured values for off-line operation was carried out by means of data transfer (Mettler) using the small computer KRS 4200. Information on the system and the accuracy of data transfer is given. The methods have been compared for the dehydration of calcium oxalate, the formation of metakaolinite, the oxidation of petroleum coke, and the dehydration of montmorillonite. Using the differential method, in part, kinetic parameters have been obtained which cannot be interpreted in a physical sense. In order to determine the causes of different results, the effects of various mathematical procedures have been studied. This study and the comparison with literature data indicate that the programme for the determination of kinetic parameters by the integral method as described gives the most reliable results.

Reevaluation of Montmorillonite Dehydration as Cause of Abnormal Pressure and Hydrocarbon Migration

Powers proposed (montmorillonite-illite conversion) as a cause of abnormal pressures in the deep subsurface of the Gulf Coast area. This paper compares his hypothesis with compaction disequilibrium and concludes that, whereas the latter mechanism by itself can account for abnormal pressures, montmorillonite dehydration by itself cannot, though it may act in a secondary capacity to increase abnormal pressures. As to Burst's hypothesis that montmorillonite (second stage) dehydration is an important factor related to hydrocarbon migration from shales into reservoirs, the conclusion here is that second-stage dehydration may be important in moving hydrocarbons out of source rocks when it is followed by the proper fluid expulsion from shales (similar to Burst's first-stage dehydration), but that montmorillonite dehydration alone without good drainage may not be significant. The low frequency of producing zones below dehydration level in the Gulf Coast is probably the result simply of the poor drainage and reservoirs in this section. Montmorillonite dehydration probably is effective in releasing hydrocarbon sources from clay-interlayer to interparticle locations (shale pore space), but may not n itself suffice to move large amounts of hydrocarbons out of shales into nearby permeable beds; for hydrocarbons to be pooled, the shale pore water subsequently must be squeezed out by overburden pressure.

Late-Stage Dehydration in Deeply Buried Pelitic Sediments

Late-stage dehydration of shales containing montmorillonite or highly expandable illite-montmorillonite consists of the conversion of montmorillonite to illite layers, thus removing interlayer water. This conversion involves interlayer potassium fixation and probably is a result of ionic substitution within the montmorillonite alumino-silicate layer. Therefore, the rate at which dehydration takes place--and, indeed, whether it takes place at all--should be dependent on the chemical conditions of diagenesis, particularly pore-water composition. Detailed X-ray diffraction studies of cuttings from several Gulf Coast wells have resulted in a quantitative interpretation of late-stage dehydration of shales, caused by loss of interlayer water in montmorillonite. In the wells studied late-stage dehydration begins in the depth range of 6,000-8,000 ft and continues over a stratigraphic interval of 4,000-10,000 ft or more. Higher geothermal gradients result in shorter dehydration intervals. Montmorillonite dehydration rates reach maxima at the very inception of the diagenetic reaction and very near its close, when new illite layers are introduced into the illite-montmorillonite in an ordered fashion. At the close of the diagenetic reaction the illite-montmorillonite still contains about 20 percent hydrated layers which persist to tota depth in all wells studied. The temperature of inception of late-stage dehydration, as well as of its close, appears to be dependent on pressure, but other parameters such as pore-water chemistry may be equally important.

Rates of low‐temperature dehydration of montmorillonite and illite

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

Geothermal resources of the northern gulf of Mexico basin

Published geothermal gradient maps for the northern Gulf of Mexico basin indicate little or no potential for the development of geothermal resources. Results of deep drilling, from 4000 to 7000 meters or more, during the past decade however, define very sharp increases in geothermal gradient which are associated with the occurrence of abnormally high interstitial fluid pressure (geopressure). Bounded by regional growth faults along the landward margin of the Gulf Basin, the geopressured zone extends some 1300 km from the Rio Grande (at the boundary between the United States and Mexico) to the mouth of the Mississippi river. Gulfward, it extends to an unknown distance across the Continental Shelf. Within geopressured deposits, geothermal gradients range upwards to 100 °C/km, being greatest within and immediately below the depth interval in which the maximum pressure gradient change occurs. The 120 °C isogeotherm ranges from about 2500 to 5000 m below sea level, and conforms in a general way with depth of occurrence of the top of the geopressured zone. Measured geostatic ratios range upward to 0.97; the maximum observed temperature is 273 °C, at a depth of 5859 m. Dehydration of montmorillonite, which comprises 60 to 80 percent of clay deposited in the northern Gulf Basin during the Neogene, occurs at depths where temperature exceeds about 80 °C, and is generally complete at depths where temperature exceeds 120 °C. This process converts intracrystalline and bound water to free pore water, the volume produced being roughly equivalent to half the volume of montmorillonite so altered. Produced water is fresh, and has low viscosity and density. Sand-bed aquifers of deltaic, longshore, or marine origin form excellent avenues for drainage of geopressured deposits by wells, each of which may yield 10,000 m 3 or more of superheated water per day from reservoirs having pressures up to 1000 bars at depths greater than 5000 m.

On the Maintenance of Anomalous Fluid Pressures: II. Source Layer at Depth

Physico-chemical mechanisms have been suggested to account for anomalous fluid pressures in the geologic environment which require a fluid source at depth. The persistence of anomalous pressure is a problem that involves nonsteady fluid flow. The hydrodynamics and particular boundary conditions control the time rate of pressure change and its maintenance. A series of mathematical solutions germane to the maintenance of anomalous pressure caused by the injection of fluids into the system from a source layer are presented. The phase change, gypsum to anhydrite plus water, is used as an example of a fluid source at depth. The thermodynamics of the gypsum-dehydration reaction indicates that conversion will probably occur at shallow depths and produce fluid at a constant rate. The dehydration of montmorillonite will also produce fluids at a constant rate under geologic conditions where the reaction can occur. If horizons of material of low permeability are missing or scarce, it is doubtful that anomalous pore pressures can be maintained for more than a geologic instant. The creation and continuation of anomalous pressure depend largely upon the hydraulic conductivity and, to a lesser extent, upon the specific storage of clay layers within the system.

STUDY OF DEHYDRATION OF MONTMORILLONITE AND VERMICULITE BY INFRARED SPECTROSCOPY

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSTUDY OF DEHYDRATION OF MONTMORILLONITE AND VERMICULITE BY INFRARED SPECTROSCOPYJ. J. Fripiat, J. Chaussidon, and R. TouillauxCite this: J. Phys. Chem. 1960, 64, 9, 1234–1241Publication Date (Print):September 1, 1960Publication History Published online1 May 2002Published inissue 1 September 1960https://doi.org/10.1021/j100838a028RIGHTS & PERMISSIONSArticle Views253Altmetric-Citations42LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (880 KB) Get e-Alerts