Thermodynamique de l’échange des cations alcalins dans les argiles

Martin, Henri; Laudelout, H.

doi:10.1051/jcp/1963601086

Cited by 42 publications

(23 citation statements)

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“…Observed heats of exchange for uptake of the preferred cation on montmorillonite are generally exothermic Laudelout et al, 1968;Martin and Laudelout, 1963), resulting in a decrease in selectivity with increasing temperature. This is consistent with general adsorption theory (Brunauer, 1945).…”

Section: B Heats Of Exchangementioning

confidence: 99%

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Sodium-Lithium Exchange Equilibria on Vermiculite at 25° and 50°C

Gast¹

1971

Clays and clay miner.

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Abstract-Sodium-lithium exchange equilibria between dilute aqueous chloride solutions and 0.2-62/z Transvaal, South African vermiculite were studied at 25 ~ and 50~ using a dialysis technique. The K content of the vermiculite was reduced to < 1% of the exchange capacity of 2.14 me/g by exhaustive extraction using Na-tetraphenylboron. The thermodynamic equilibrium constants and in turn the standard free energies and heats of exchange were evaluated from the equilibrium selectivity coefficients at the two temperatures. The standard entropy of exchange, AS ~ was calculated according to the relationship AG ~ = AH ~ --TAS ~ Similar results were obtained for Na ~ Li and Li ~ Na exchange at 25~ thus confirming the reversibility of the reaction.Sodium preference increased with Na saturation of the vermiculite and equilibrium selectivity coefficients ranged from 6-0 to 22.0 at 25~ In comparison, selectivity coefficients for Na-Li exchange on montmorillonite ranged from 1.0 to 2.0 and became smaller with increasing Na saturation. The standard free energy and heat of exchange on vermiculite at 25~ were-1444 and-5525 cal mole -1, respectively, resulting in a AS ~ value of-13.7 e.u. This relatively large entropy change is probably due to differences in ion hydration in the solution and surface phases.

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Section: B Heats Of Exchangementioning

confidence: 99%

“…Spontaneous ion exchange reactions on montmorillonite are nearly always accompanied by a relatively small negative entropy change in the order of-1 to-2e.u. Martin and Laudelout, 1963) with some values as great as -4 to -5 e.u. (Laudelout et al, 1968).…”

Section: Entropies Of Exchangementioning

confidence: 99%

Sodium-Lithium Exchange Equilibria on Vermiculite at 25° and 50°C

Gast¹

1971

Clays and clay miner.

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“…In the past, the electrodialysis and filtration techniques of Marshall and Bergman (1941) and of Faucher et al (1952) were commonly used. More recently normal centrifugation (van Olphen, 1977;Jackson, 1956) or dialysis have been used almost exclusively (e.g., see Banin and Lahav, 1968;Levy and Shainberg, 1972;Allen, 1972), and it has become common to use centrifugation followed by dialysis (e.g., see Cremers and Thomas, 1966;Martin and Laudelout, 1963). Certain objections may be raised to each of these procedures.…”

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confidence: 99%

Application of Ultrafiltration/Dialysis to the Preparation of Clay Suspensions

Schramm

1980

Clays and clay miner.

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“…The K ~ for SWy-1, SAz-1, and Llano vermiculite (VTx-1) were obtained from a previous paper by the same authors (Xu and Harsh, 1990b) and those for Upton Wyoming montmorillonite, Chambers montmorillonite from Gast (1972), and Camp Berteau montmorillonite from Martin and Laudelout (1963) were obtained from the exchange isotherms determined at the same ionic strength (0.01 M), temperature (298 K), and pressure (1 arm) as described above. The K ~ for Utah bentonite from Krishnamoorthy and Overstreet (1949) was determined at the same temperature and pressure as above but at a slightly smaller ionic strength (0.007 M).…”

Section: Cation Selectivitymentioning

confidence: 99%

Alkali Cation Selectivity and Surface Charge of 2:1 Clay Minerals

Harsh

1992

Clays and clay miner.

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Abstract--A critical demand in environmental modeling and a desirable but elusive goal of research on the ion exchange properties of the charged solid surface has been to determine the selectivity coefficient from fundamental properties of the ions and surface. We developed a Hard and Soft Acid and Base (HSAB) Model to describe exchangeable cation selectivity on solid surfaces. Our previous work has shown that the model quantitatively describes alkali cation exchange on clay minerals in terms of the absolute etectronegativity and softness of the exchangeable cations and two fitting parameters: a and/3. This study was conducted to determine the relationship between a and/3 and surface charge characteristics of 2:1 clays. The layer charge and cation selectivity of seven smectites and one vermiculite were used. The regression of log K ~ against four combinations of charge properties was performed and the appropriate relationship between a,/3, and surface charge was selected based on both statistical criteria (R 2) and their consistency with the assumptions of the HSAB model. The selected model was then cross-validated using separate cation exchange data from the literature. It was found that a and/3 are linearly related to the amount of charge arising from mineral tetrahedral and octahedral sites, respectively. These results make it possible to predict the alkali cation selectivity of 2:1 clay minerals from their chemical composition data and the alkali cation properties.

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Thermodynamique de l’échange des cations alcalins dans les argiles

Cited by 42 publications

References 0 publications

Sodium-Lithium Exchange Equilibria on Vermiculite at 25° and 50°C

Sodium-Lithium Exchange Equilibria on Vermiculite at 25° and 50°C

Application of Ultrafiltration/Dialysis to the Preparation of Clay Suspensions

Alkali Cation Selectivity and Surface Charge of 2:1 Clay Minerals

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