Alkali Metal Cation Exchange on Chambers Montmorillonite

Gast, R. G.

doi:10.2136/sssaj1972.03615995003600010003x

Cited by 59 publications

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“…Laudelout et al (1968) corrected their calorimetric values to standard state conditions and found that they agreed well with values derived from the tem perature dependence of ln K. In the case of NH 4 /Ca exchange on Camp Berteau montmo rillonite, the corrected calorimetric value was 10.5 kJ mol 1 , and the one derived from tem c perature dependence was 11.3 kJ mol 1 . Heats c of exchange on soils and clay minerals generally follow the lyotropic series: Li Ͻ Na Ͻ K Ͻ Rb Ͻ Cs; Mg Ͻ Ca Ͻ Sr Ͻ Ba (Gast, 1972;Gast et al, 1969;Laudelout et al, 1968). Because the forces of attraction are predominantly electrosta tic, the preference of the clay for cations of the same charge increases as their hydrated radii de crease.…”

Section: Sensitivity and Precision Of Heat Measurementsmentioning

confidence: 99%

“…These heats of exchange c are similar to values reported for soils and clays that were obtained using conventional batch cal orimeters or derived from temperature depen dence of the exchange constant. For example, Gast (1972) Sparks and Jardine (1981) used a kinetic approach to derive K/Ca exchange constants at several temperatures for a soil whose clay fraction was dominated by vermiculite, chloritized vermicu lite, and mica. The temperature dependence of these exchange constants yielded standard en thalpies of exchange of 7.1 and 5.6 kJ mol Ϫ1 for c samples from the A and B horizons, respectively.…”

Section: Sensitivity and Precision Of Heat Measurementsmentioning

confidence: 99%

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Measuring Surface Chemical Properties of Soil Using Flow Calorimetry 1

2002

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Flow calorimetry, which is ideally suited for measuring reactions oc curring at the liquid/solid interface, has been used to study the surface chemistry of many types of solids, but little use of it has been made in the study of surface reactions of soils. The purpose of this study was to demonstrate the application of flow calorimetry to the study of two fun damental soil chemical processes, namely cation exchange and phosphate sorption. Surface horizon samples of a Typic Acrorthox and a Typic Tropohumult from Puerto Rico, a strong acid cation exchange resin (Dowex 50W-8), and an amorphous Al(OH) 3 were used. Heats for K/Ca exchange on the Dowex resin and the Oxisol, and K/Na exchange on the Ultisol, were consistent with literature values that were obtained using conventional batch calorimetry or derived from the temperature depen dence of the exchange constant. Although peak areas associated with a given pair of exchange reactions were equal, peak shapes were generally not equivalent, indicating differences in the rate at which the two reac tions occurred. For example, Ca displacing exchangeable K occurred more rapidly than the reverse reaction on the Dowex resin. The reaction of phosphate with the Ultisol and amorphous Al(OH) 3 was exothermic. Exposure of the soil to several cycles of phosphate was sufficient to sat urate the sorption sites, as evidenced by the loss of a detectable heat sig nal. However, phosphate reactive sites were regenerated by flushing the column with a salt solution at pH 10. Precipitation of Al-phosphate was shown to be endothermic, confirming that precipitation was not the pri mary mechanism for phosphate sorption in this study.

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Section: Sensitivity and Precision Of Heat Measurementsmentioning

confidence: 99%

Section: Sensitivity and Precision Of Heat Measurementsmentioning

confidence: 99%

Measuring Surface Chemical Properties of Soil Using Flow Calorimetry 1

2002

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“…As indicated previously, 2:1 layer silicates generally exhibit high selectivity for K relative to Ca in the interlayer. The observed surface heterogeneity can be explained if initially Ca and Pb replaced K adsorbed to external ex change sites (i.e., organic matter, kaolinite, edges and planar smectitic surfaces) and then proceeded to replace K from the smectite interlayers, the lat ter requiring more energy (Gast, 1972;Sparks and Jardine, 1981). Results obtained from X ray dif fraction analysis support this hypothesis since the smectite in the Ultisol was able to collapse, in part, when K saturated but re expanded on Ca saturation.…”

Section: Differential Heats Of Adsorptionmentioning

confidence: 99%

HEATS OF K/Ca AND K/Pb EXCHANGE IN TWO TROPICAL SOILS AS MEASURED BY FLOW CALORIMETRY 1

Appel

Rhue²,

Ma³

et al. 2002

Soil Science

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Flow calorimetry can provide useful information about surface chem ical reactions in soils that cannot be obtained readily by other methods. When flow calorimetry is conducted over a range of surface coverages, different sorption heats can be calculated to yield information about how binding energies vary with coverage, i.e., surface heterogeneity. The purpose of this study was to determine heats of exchange for K/Ca and K/Pb systems using flow calorimetry and to evaluate the degree of sur face heterogeneity with respect to cation exchange. Surface horizon sam ples from a Typic Acrorthox and Typic Tropohumult from Puerto Rico were used. Lead was adsorbed specifically in both soils, but no adsorp tion heat was detected for this reaction in either soil. However, heats as sociated with reversible cation exchange between K and Pb were ob served. Heats for K/Ca exchange were greater than those generated for K/Pb exchange in both soils. Heats of exchange were greater in the Ul tisol than in the Oxisol. The differential heats of exchange were inde pendent of exchange composition for both K/Pb and K/Ca exchange in the Oxisol, indicating that all cation exchange sites were similar energet ically. In the Ultisol, the differential heats of exchange increased as ex changeable K decreased, indicating that the exchange sites were not sim ilar energetically. These differences were attributed to the presence of smectite in the Ultisol, which was able, in part, to collapse when satu rated with K. (Soil Science 2002;167:773-781)

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“…For Upton Wyoming and Chambers montmorillonites, both exchange data and chemical analysis were obtained from Gast (1972). For others, the tetrahedral and octahedral charges were calculated from the total elemental analysis data from 4"---1954; (10) Foster, 1963;(11) Gast, 1972;(12) Grim and Guven, 1978;(13) Kittrick, 1973;(14) Laird, 1987;(15) Lagaly, 1982;(16) Mattigod and Sposito, 1978;(17) Merriam and Thomas, 1956;(18) Norrish, 1973;(19) Senkayi et al, 1985;(20) Shirozu and Bailey, 1966;(21) Schultz, 1969;(22) Sterte and Shabtai, 1987;(23) Van Olphen and Fripiat, 1979;(24) Weaver and Pollard, 1973;(25) Weir, 1965;(26) this study.…”

Section: Layer Chargementioning

confidence: 99%

“…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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Alkali Metal Cation Exchange on Chambers Montmorillonite

Cited by 59 publications

References 0 publications

Measuring Surface Chemical Properties of Soil Using Flow Calorimetry 1

Measuring Surface Chemical Properties of Soil Using Flow Calorimetry 1

HEATS OF K/Ca AND K/Pb EXCHANGE IN TWO TROPICAL SOILS AS MEASURED BY FLOW CALORIMETRY 1

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

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