Free Energy of Formation of Beidellite from Apparent Solubility Measurements

Misra, U. K.; Upchurch, W. J.

doi:10.1346/ccmn.1976.0240609

Cited by 9 publications

(2 citation statements)

References 19 publications

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“…For the muscovite-like example, the following four interaction terms: (Huang and Keller, 1973); Beidellite (Misra and Upchurch, 1976); Belle Fourche, Aberdeen (Kittrick, 1971a;Peryea and Kittrick, 1986); Colony, Castle Rock, Upton (Weaver et al, 1976)]; 9 saponite and vermiculite (Tardy and Fritz, 1981); O nontronite (Tardy and Fritz, 1981); • beidellite and glauconite (Tardy and Fritz, 1981); 9 exchanged montmorillonites (Mattigod and Sposito, 1978); + idealized clay (Wolery and Daveler, 1992); 9 smectites (Wolery and Daveler, 1992); i idealized montmorillonites (Chermak and Rimstidt, 1989); [] natural illites; & idealized illites. go to zero in the general expression of AG~, (Table 3).…”

Section: Short-range Interactionsmentioning

confidence: 99%

A New Method for the Prediction of Gibbs Free Energies of Formation of Hydrated Clay Minerals Based on the Electronegativity Scale

Vieillard

2000

Clays and clay miner.

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Abstract--A new method for the prediction of Gibbs free energies of formation for hydrated clay minerals is proposed based on the parameter AGO-Mz+(clay) characterizing the oxygen affinity of the cation M ~ § The Gibbs free energy of formation from constituent oxides is considered as the sum of the products of the molar fraction of an oxygen atom bound to any two cations multiplied by the electronegativity difference defined by the A60 = MZ+(clay) between any two consecutive cations. The A60 = Mz+(clay) value, using a weighting scheme involving the electronegativity of a cation in a specific site (interlayer, octahedral, or tetrahedral) is assumed to be constant and can be calculated by minimization of the difference between experimental Gibbs free energies (determined from solubility measurements) and calculated Gibbs free energies of formation from constituent oxides. Results indicate that this prediction method compared to other determinations, gives values within 0.5% of the experimentally estimated values. The relationships between Act-Mz+(clay) corresponding to the electronegativity of a cation in either interlayer or octahedral sites and known Act-Mz+(aq) were determined, thereby allowing the prediction of the electronegativity of transition metal ions and trivalent ions in hydrated interlayer sites and octahedral sites. Prediction of Gibbs free energies of formation of any clay mineral with various ions located in the interlayer and with different cations in octahedral sites is possible. Examples are given for Al-rich montmorillonite from Aberdeen, transition element-exchanged montmorillonite, and Ni-rich stevensite, and the results appear excellent when compared to experimental values.

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Section: Short-range Interactionsmentioning

confidence: 99%

A New Method for the Prediction of Gibbs Free Energies of Formation of Hydrated Clay Minerals Based on the Electronegativity Scale

Vieillard

2000

Clays and clay miner.

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“…(2) Mattigod & Sposito (1978) for solubility of smectites measured by Kittrick (1971a,b,c), Weaver et al (1971), Weaver et al (1976), Huang & Keller (1973, Misra & Upchurch (1976), Reesman & Keller (1968).…”

Section: (X8-i-xi2-]-x16-~-x20-~-x24-~-x28-l-x32-}-x36 )mentioning

confidence: 99%

An ideal solid solution model for calculating solubility of clay minerals

Tardy¹,

Fritz

1981

Clay miner.

102

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A method for estimating Gibbs free energies and stabilities of clay minerals is proposed for use with computer programs aimed at calculating the chemical evolution of natural water-rock systems. This is based on (i) a model for ideal solid solutions of a large number of end-member compositions and (ii) a data set of estimated solubility products from 36 end-members. The application of the method to the production of experimental or natural clay stabilities is discussed.In the evolution of natural water-rock systems, clay minerals appear as omnipresent reactants or products of chemical reactions. In an attempt to model such reactions by the use of computer programs, clay mineral compositions have to be considered essentially as variable. It is possible to take into account such chemical composition variations by considering clays (i) as a set of separate mineral phases and including in the models a large number of minerals of discrete compositions and their solubilities, or (ii) as solid solutions whose compositions change continuously during the chemical processes.The first method was followed by Fritz & Tardy (1974 and Fritz (1975). The results obtained were roughly in agreement with natural observations. Nevertheless, this method is limited in practice as it requires too large a data set to cover the whole range of chemical composition of natural clays. The second approach was used by Helgeson & Mackenzie (1970) for illite-montmorillonite solid solutions. This appears the most suitable for modelling and understanding the chemical evolution of natural systems, although the type of solid solution model has to be chosen, as well as the different end-members and their relative solubility products.

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Chemical Models of Weathering in Soils

Sposito

1985

The Chemistry of Weathering

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Free Energy of Formation of Beidellite from Apparent Solubility Measurements

Cited by 9 publications

References 19 publications

A New Method for the Prediction of Gibbs Free Energies of Formation of Hydrated Clay Minerals Based on the Electronegativity Scale

A New Method for the Prediction of Gibbs Free Energies of Formation of Hydrated Clay Minerals Based on the Electronegativity Scale

An ideal solid solution model for calculating solubility of clay minerals

Chemical Models of Weathering in Soils

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