The study of the dehydration and dehydroxylation of smectites by emanation thermal analysis

Málek, Z.; Bálek, V.; Garfinkel-Shweky, D.; Yariv, S.

doi:10.1007/bf01978968

Cited by 50 publications

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“…Emanation Thermal Analysis (ETA) [8,9], based on the measurement of radon release from samples previously labeled, was used to characterize microstructure changes during "in situ" heating of the samples. The ETA has been previously used in the characterization of the thermal behavior of various minerals, such as kaolinite [10], saponite, beidelite [3], vermiculite [11][12][13], boehmite [14], pyrophyllite, talc [15], brannerite [16], haematite [17].…”

Section: +mentioning

confidence: 99%

“…In order to understand the environmental behaviour of monmorillonite clay minerals their dehydration and dehydroxylation on heating has been studied by several authors [1][2][3][4][5][6][7]. It was found that differences in the montmorillonite dehydration are due to a more or less strong ) the ion is more important that the interlayer surface, but for larger divalent cations as well as for monovalent cations the influence of the layered surface on the hydration is dominant.…”

Section: Introductionmentioning

confidence: 99%

“…

AbstractEmanation thermal analysis (ETA), thermogravimetry and high temperature XRD were used to characterize the thermal behavior during dehydration of natural Na The decrease of the radon release rate (∆E) determined by ETA that characterized microstructure changes due to collapse of interlayer space corresponded well to differences in the c-axis basal spacing (∆d 001 ) values determined from the XRD patterns before and after samples dehydration .*corresponding author: bal@ujv.cz 2 Key words: Na-montmorillonite saturated with various cations ,emanation thermal analysis, XRD, thermogravimetry , microstructure changes , dehydration

1.IntroductionIn order to understand the environmental behaviour of monmorillonite clay minerals their dehydration and dehydroxylation on heating has been studied by several authors [1][2][3][4][5][6][7]. It was found that differences in the montmorillonite dehydration are due to a more or less strong ) the ion is more important that the interlayer surface, but for larger divalent cations as well as for monovalent cations the influence of the layered surface on the hydration is dominant.

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confidence: 99%

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Thermal characterization of montmorillonite clays saturated with various cations

Bálek

Beneš

Šubrt

et al. 2008

J Therm Anal Calorim

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Emanation thermal analysis (ETA), thermogravimetry and high temperature XRD were used to characterize the thermal behavior during dehydration of natural Na The decrease of the radon release rate (∆E) determined by ETA that characterized microstructure changes due to collapse of interlayer space corresponded well to differences in the c-axis basal spacing (∆d 001 ) values determined from the XRD patterns before and after samples dehydration .*corresponding author: bal@ujv.cz 2 Key words: Na-montmorillonite saturated with various cations ,emanation thermal analysis, XRD, thermogravimetry , microstructure changes , dehydration 1.IntroductionIn order to understand the environmental behaviour of monmorillonite clay minerals their dehydration and dehydroxylation on heating has been studied by several authors [1][2][3][4][5][6][7]. It was found that differences in the montmorillonite dehydration are due to a more or less strong ) the ion is more important that the interlayer surface, but for larger divalent cations as well as for monovalent cations the influence of the layered surface on the hydration is dominant. Glasser et al. [7] showed that polyvalent ions tend to detach themselves from the silicate surface and incorporate in the water layers. They stated that the complete loss of the interlayer water is accompanied by a reduction in the c-axis dimensions (to 9.4-10 Å) with exact value depending on the size of interlamellar ions.In this study thermogravimetry , emanation thermal analysis and high temperature X-ray diffraction methods were used to characterize the thermal behavior during dehydration of natural Na montmorillonite and homoionic montmorillonite samples prepared Experimental SamplesNatural Na-montmorillonite (Upton, Wyoming, USA) was used as a starting material. ,respectively , were prepared from Na-montmorillonite sample as follows: the amount of 10 g of the Na-montmorillonite was mixed with 800 ml of water and stirred during two days.After decantation 0.2 M chloride solution (200 ml) of the respective cation was added. The suspension was stirred for two days, several times washed by distilled water until the negative reaction for chlorides (using Ag + ions). The samples prepared by this way were dried at the temperature of 40 °C in air . MethodsEmanation thermal analysis (ETA) measurements were carried out by using a modified NETZSCH Equipment Type DTA 404. The samples were heated at the rate of 6 K/min in a constant air flow of 75 ml/min. Samples for ETA measurements were labeled by a analysis as a less common method are given elsewhere [8 ,9]. TG /DTG measurements were carried out by using NETZSCH Equipment Type STA 429 on heating at 6 K/min in air.XRD equipment (PHILIPS PW 1050/25) using Cu K α Ni-filtered radiation and equipped with a high temperature chamber was applied to obtain XRD patterns and to determine c-axis basal spacings (d 001 ). Results and discussionThermogravimetry results (TG /DTG curves) of Na-montmotillonite and homoionic montmorillonite samples saturated with Mg The tem...

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confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermal characterization of montmorillonite clays saturated with various cations

Bálek

Beneš

Šubrt

et al. 2008

J Therm Anal Calorim

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“…(Dehydroxylation endothermic peaks for these particular clays are 650 and 810~ respectively [21]. Each of the clays showed variable basal spacings ( Fig.…”

Section: Slides Heated At 600~mentioning

confidence: 98%

“…(For this particular clay the endothermic peak was determined to be 530~ [21 ] and this would allow a condensation reaction to take place such that an A1-O-clay bond formed [ …”

Section: Slides Heated At 500~mentioning

confidence: 99%

XRD study of the dehydration and rehydration behaviour of Al-pillared smectites differing in source of charge

Aceman

Lahav

Yariv

1997

Journal of Thermal Analysis

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The swelling properties of Al-pillared clays, obtained from five different smectites, were studied using X-ray diffraction. These clays, the dioctahedral beidellite and montmorillonite and the trioctahedral saponite, hectorite and laponite differ in source of isomorphic substitution and represent a series of decreasing basicity along the siloxane plane. An A1 oxyhydroxy cation was inserted between the layers to form the respective pillared clays and these clays were heated incrementally to 600~ The XRD peaks at each stage of heating were recorded as weII as the same samples subsequently wetted. Basal spacings of each clay at each stage of dehydration and rehydration indicated that the swelling nftetrahedrally substituted saponite and beidellite was indeed restricted, compared with the other three clays. This was attributed to greater basicity of the oxygen plane ofbeidellite and saponite due to tetrahedral substitution of Si by A1, resulting in an increase in the strength of hydrogen bonds between either water or the interlayer polyhydroxy cation and the clay.The data from the XRD analyses helped in addition, to clarify the thermal transformations of the Keggin ion itself. According to the changes in the d-spacings of the pillared clays it was concluded that the Keggin ion lost its structural water at-200~ and dehydroxylated in a range beginning at 350~ Between 500 to 600~ this polymer cation, which is thought to form the A1203 oxide, did not rehydrate.

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Diffusion Structural Analysis in the Characterization of Inorganic Materials

Bálek

1999

Characterization Techniques of Glasses and Ceramics

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The study of the dehydration and dehydroxylation of smectites by emanation thermal analysis

Cited by 50 publications

References 10 publications

Thermal characterization of montmorillonite clays saturated with various cations

Thermal characterization of montmorillonite clays saturated with various cations

XRD study of the dehydration and rehydration behaviour of Al-pillared smectites differing in source of charge

Diffusion Structural Analysis in the Characterization of Inorganic Materials

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