The relative partial specific enthalpy of water in montmorillonite-water systems and its relation to the swelling of these systems

Oliphant, Joseph L.; Low, Philip F.

doi:10.1016/0021-9797(82)90189-8

Cited by 35 publications

(22 citation statements)

References 16 publications

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“…To determine this property, samples of the Na-montmorillonite were brought to different H20 contents by methods 1, 2, and 3, and then Q, the heat of immersion, i.e., the heat released by immersing the sample in water, was measured calorimetrically at 25~ as described by Oliphant and Low (1982). Because…”

Section: Methodsmentioning

confidence: 99%

Changes in the Properties of a Montmorillonite-Water System during the Adsorption and Desorption of Water: Hysteresis

Zhang

Low

1990

Clays and clay miner.

181

152

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Abstract--Samples of Na-saturated, Upton montmorillonite were prepared with different contents of water (H20 or D20) by: (1) adsorption of water from the vapor phase at a specific value of p/p*, the relative humidity, (2) adsorption of water from the vapor phase at p/p* = 1.0 followed by desorption of the water into the vapor phase at a specific p/p* < 1.0, and (3) adsorption of water from the liquid phase followed by desorption of the water into the vapor phase at a specific p/p* < 1.0. Water adsorbed initially from the vapor phase was called V-adsorbed water, and water adsorbed initially from the liquid phase was called L-adsorbed water. The water contents of these samples were determined by gravimetric analysis, the c-axis spacings by X-ray powder diffraction, the O-D stretching frequencies by IR spectroscopy, and the heats of immersion by differential microcalorimetry. No difference was found between V-adsorbed and L-adsorbed water; however, if the final water content was established by adsorption, the system was in a different state than if the final water content was established by desorption. In particular, hysteresis was observed in the following properties: the relative humidity of the adsorbed water, the O-D stretching frequency in this water, and the degree of order in the stacking of the clay layers. The only property that did not exhibit hysteresis was the heat of immersion. Apparently, hysteresis occurred because the orderliness of the system was not reversible, and, thus, any property that depended on orderliness was hysteretic.

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Section: Methodsmentioning

confidence: 99%

Changes in the Properties of a Montmorillonite-Water System during the Adsorption and Desorption of Water: Hysteresis

Zhang

Low

1990

Clays and clay miner.

181

152

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“…A similar procedure was adopted by Oliphant & Low (1982) for the calculation of . This point has been discussed in detail by Sposito & Prost (1982).…”

Section: Methodsmentioning

confidence: 99%

“…It may differ substantially from the value for pure water near room temperature (Vw ~ = 10 -3 m3/kg), in particular for low contents of water in the bentonites (Oliphant & Low, 1982). The difference in free energy is also related to pw, the partial vapour pressure of water in the system, and the vapour pressure Po of pure water at the temperature T of the experiment (Oliphant & Low, 1982) gw…”

Section: Gw = ( 6gw/bmw)tp and Hw = (6hwlbmw)rementioning

confidence: 99%

Study of the water-bentonite system by vapour adsorption, immersion calorimetry and X-ray techniques: II. Heats of immersion, swelling pressures and thermodynamic properties

Kahr

1990

Clay miner.

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A B S T R A C T:A number of thermodynamic properties were obtained from the determination of adsorption isotherms and enthatpies of immersion for systems with water and Na-and Ca-bentonites. Entropy differences were calculated by combining the enthalpies of immersion and the changes in free energy derived from the adsorption isotherms. The swelling pressures, also calculated from the water adsorption isotherms, are in satisfactory agreement with the experimental data.In the second part of this study of the water-bentonite system for well characterized natural Na-and Ca-bentonites, the changes in the adsorption entropy, the enthalpy of immersion and the swelling pressure are examined as the amount of water increases (for the first part of the study see Kraehenbuehl et al., 1987).The transport of water in unsaturated clays and in soils depends on various potentials and on transport coefficients (diffusion coefficients, permeabilities, etc.). The potentials are thermodynamic quantities which can be derived from measurements performed at equilibrium, and they are usually defined in terms of partial specific potentials, for example g,w = ( 6Gw/bmw)T,p and hw = (6Hwlbmw)r,eIn the present study, gw and hw denote the partial specific free energy and enthalpy of water, whereas G and H represent the total free energy and enthalpy of the water-bentonite system containing mw grams of water. Low & Anderson (1958) have pointed out that gw -gw ~ the difference between the free energies of water in the water-bentonite system and pure water, is related to the swelling pressure Ps through g~ -g~~ = -9w • P~.The quantity ~7 = (5V/6mw).l;e represents the partial specific volume of water in the system. It may differ substantially from the value for pure water near room temperature

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“…In addition to adsorption properties, wetting processes (Dekany et al, 1983;Szfint6 et al, 1986;, swelling properties (Low, 1987;Viani et al, 1983Viani et al, , 1985Lagaly et al, 1983;Oliphant and Low, 1982), and electrokinetic properties are also of considerable interest (Delgado et al, 1986a(Delgado et al, , 1986b. At least four different, nonspecific mechanisms of water adsorption can be distinguished; i.e., hydrogen bond formation, hydration of surface cations, permanent dipoles of the surface-water dipoles interaction, and London dispersion forces interactions are present in all systems (Low, 1961;Jackson et al, 1971;SwartzenAllen and Matijevi6, 1974).…”

Section: Introductionmentioning

confidence: 99%

Determination of Surface Free Energy of Kaolinite

Chibowski

Staszczuk

1988

Clays and clay miner.

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Abstract--The adsorption of n-octane and water vapor on natural kaolinite was measured. From adsorption isotherms film pressures were determined which were then used to calculate the dispersion and nondispersion components of the kaolinite surface free energy. In addition, thermodesorption of water from the kaolinite surface was determined. These results suggest that physically adsorbed water remained on the kaolinite surface, even at temperatures as great as 125"(2. Therefore, experimentally determined dispersion and nondispersion components appear to relate to the surface precovered with a film of water. These values are: ~gw) = 34.4 mJ/m 2 for dispersion interactions and ~gw) = 60.2 mJ/m 2 for nondispersion interactions. Assuming a kaolinite surface precovered with a film of water, which decreased the free energy by the work of spreading, the following components of the energy for the bare surface were calculated: ~s = 67.6 mJ/m 2 and 3'~ = 103.4 mJ/m 2, for dispersion and nondispersion components, respectively. Key Words--Adsorption, Film pressure, Free energy, Kaolinite, n-Octane, Surface, Water.Abstrakt --Zmierzono adsorpcje pary wodnej i n-oktanu na naturalnymkaolinicie. Z uzyskanych izoterm adsorpcji wyznaczono cignienia film6w i nastgpnie skladow~ dyspersyjn~ i niedyspersyjn~ swobodnej energii powierzchniowej kaolinitu. Pr6cz tego, zbadano tak2e termodesorpcj~ wody z powierzchni kaolinitu. Z tych do~wiadczefi wynika, ~e woda zaadsorbowana fizycznie pozostaje na powierzchni kaolinitu nawet do 125~ Dlatego, sugeruje si~, ~e wyznaczona do~wiadczalnie skladowa dyspersyjna i niedyspersyjna dotyczy powierzchni pokrytej filmem wody. Wyznaczone warto~ci wynosz~: ~gw) = 34.4 mJ/m 2 dla oddzialywafi dyspersyjnych i "Y~w) = 60.2 rnJ/m 2 dla oddziatywafi niedyspersyjnych. Przyjmuj0c model, w kt6rym film wody na powierzchni kaolinitu obni~a jego swobodm~ energi~ o pracg rozptywania, wyliczono skfadowe tej energii dla czystej powierzchni kaolinitu. Sk~adowe te wynosz~: ~ = 67.6 rnJ/m 2 i "r~ = 103.4 mJ/m 2.

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The relative partial specific enthalpy of water in montmorillonite-water systems and its relation to the swelling of these systems

Cited by 35 publications

References 16 publications

Changes in the Properties of a Montmorillonite-Water System during the Adsorption and Desorption of Water: Hysteresis

Changes in the Properties of a Montmorillonite-Water System during the Adsorption and Desorption of Water: Hysteresis

Study of the water-bentonite system by vapour adsorption, immersion calorimetry and X-ray techniques: II. Heats of immersion, swelling pressures and thermodynamic properties

Determination of Surface Free Energy of Kaolinite

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