Thermochemical study of natural montmorillonite

Ogorodova, L. P.; Киселева, И. А.; Melchakova, L. V.; Вигасина, М. Ф.; Krupskaya, V. V.

doi:10.1134/s0016702913040058

Cited by 9 publications

(5 citation statements)

References 13 publications

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“…The obtained value is close to the determined previously values of the enthalpy of dehydroxylation for the montmorillonite [166 ± 10 kJ/(mol H 2 O)] (Ogorodova et al 2013) and for the sepiolite [145 ± 14 kJ/(mol H 2 O)] (Ogorodova et al 2014). The crystal structures of all these minerals have a similar structural element (three-layer packages of 2:1 type), which is composed of two tetrahedral layers with the octahedral layer between them; each cation of this octahedral layer is surrounded by four apical O atoms and by two hydroxyl groups.…”

Section: Calorimetric Measurementssupporting

confidence: 83%

Natural Mg-Fe clinochlores: Enthalpies of formation and dehydroxylation derived from calorimetric study

Ogorodova

Вигасина

Melchakova

et al. 2016

American Mineralogist

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This paper presents the results of the first experimental thermochemical investigation of two natural trioctahedral chlorites (clinochlores). The study was performed with the help of a high-temperature heat-flux Tian-Calvet microcalorimeter. The samples were characterized by X-ray spectroscopy analysis, X-ray powder diffraction, thermal analysis, and FTIR spectroscopy. The enthalpies of formation of clinochlores were found using the melt solution calorimetry method to be: -8806 ± 16 kJ/mol for composition (Mg 4.9 Fe 2+ 0.3 Al 0.8 )[Si 3.2 Al 0.8 O 10 ](OH) 8 and -8748 ± 24 kJ/mol for composition (Mg 4.2 Fe 2+ 0.6 Al 1.2 ) [Si 2.8 Al 1.2 O 10 ](OH) 8 . The experimental data for natural samples allowed calculating the enthalpies of formation for end-members and intermediate members of the clinochlore (Mg 5 Al)[Si 3 AlO 10 ](OH) 8 and chamosite (Fe 5 Al)[Si 3 AlO 10 ](OH) 8 series. An important feature of the clinochlore structure is the presence of two distinct hydroxyl-containing octahedral layers: the interlayer octahedral sheet and octahedral 2:1 layer; the enthalpies of water removal from these positions in clinochlore structure were determined as: 53 ± 20 kJ/(mol·H 2 O) and 131 ± 10 kJ/(mol·H 2 O), respectively. These obtained first thermodynamic characteristics of Mg-Fe clinochlores can be used for quantitative thermodynamic modeling of geological and industrial processes including clinochlores of different composition.

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Section: Calorimetric Measurementssupporting

confidence: 83%

Natural Mg-Fe clinochlores: Enthalpies of formation and dehydroxylation derived from calorimetric study

Ogorodova

Вигасина

Melchakova

et al. 2016

American Mineralogist

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“…This fact indicates higher bond energies of the hydroxyl groups in the structure of sepiolite. The obtained data are close to the previously determined value of dehydroxylation enthalpy for montmorillonite [166 ± 10 kJ/(mol H 2 O)] (Ogorodova et al 2013).…”

Section: The Enthalpy Of Dehydroxylationsupporting

confidence: 81%

“…Removal of the water from sepiolite related to chain-structure clays was accompanied by the endothermic effects of about 15 kJ/mol of the adsorbed water (the value given in Table 2 was recalculated using the enthalpy of the removal of the zeolitic water); about 28 kJ/mol of the zeolitic water and about 39 kJ/mol of the bound water associated with the magnesium cations in the octahedral sheet. Previously, we have studied the dehydration process of a typical phyllosilicate-montmorillonite (containing only the adsorbed and the interlayer water) and have obtained the following values of the enthalpy of dehydration: about 6 and about 11 kJ/(mol H 2 O), respectively (Ogorodova et al 2013). Thus, obtained results show that in sepiolite with the chain structure water molecules are stronger connected with the structure of the mineral than in the ordinary layered clays.…”

Section: The Enthalpies Of Dehydrationmentioning

confidence: 87%

Natural sepiolite: Enthalpies of dehydration, dehydroxylation, and formation derived from thermochemical studies

Ogorodova

Киселева

Вигасина

et al. 2014

American Mineralogist

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Sepiolite is widely used in various fields due to its unique colloidal-rheological and physicochemical properties. The first experimental thermochemical study of natural sepiolite Mg 8 Si 12 O 30 (OH) 4 (H 2 O) 4 ·nH 2 O from Akkermanovskoe field (Southern Ural, Russia) was performed utilizing the high-temperature heat-flux Tian-Calvet microcalorimeter. X-ray powder diffraction, thermal analysis, and FTIR spectroscopy methods were used to characterize sepiolite. Processes of dehydration, dehydroxylation, and various water types' removal enthalpies were studied using thermochemical methods. The values of D dehydr. H 0 (298.15 K) of adsorbed, zeolitic, and bound water calculated per 1 mol of released H 2 O, were as follows: 15 ± 4, 28 ± 8, and 39 ± 15 kJ/mol, respectively. The enthalpy of dehydroxylation of sepiolite was found as 145 ± 14 kJ/(mol H 2 O). Obtained data point at different binding strengths of water in the structure of sepiolite. The enthalpies of formation from the elements ΔH 0 f (298.15 K) were derived by melt solution calorimetry for sepiolite with various content of different water types: -18 773 ± 28 kJ/mol for Mg 8 Si 12 O 30 (OH) 4 (H 2 O) 4 ·4H 2 O and -16 426 ± 21 kJ/mol for Mg 8 Si 12 O 30 (OH) 4 (H 2 O) 4 .

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“…The values of the enthalpy of formation for hydrous and dehydrated palygorskites were used to calculate the contribution of molecular water to the enthalpy of formation of this mineral: -(294.2 ± 5.2) kJ per mole of H 2 O. These data are in a good agreement with results of analogous calculation from calorimetric data for natural smectite -montmorillonite (-(298.5 ± 5.1) kJ per mole of H 2 O[25]). Obtained in present work value of the molecular water contribution to the enthalpy of formation of palygorskite can be utilized to calculate the enthalpies of formation of water-containing clay minerals.…”

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confidence: 52%