Kinetic and thermodynamic approaches on thermal degradation of sepiolite crystal using XRD-analysis

Sarıkaya, Yüksel; Önal, Müşerref; Pekdemir, Abdullah Devrim

doi:10.1007/s10973-019-09053-3

Cited by 10 publications

(5 citation statements)

References 27 publications

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“…The greater value of E 3 # compared to E 1 # and E 2 # is due to the chemical nature of the dehydroxylation, whereas dehydration is a physical process. Similar results were obtained using the intensity of the most characteristic XRD reflection of sepiolite (110) as a kinetic variable (Kiyohiro & Otsuka, 1989;Perraki & Orfanoudaki, 2008;Sarıkaya et al, 2019;Tian et al, 2019).…”

Section: Kinetic Considerationssupporting

confidence: 76%

Thermal degradation kinetics of sepiolite

2020

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The kinetic parameters of the thermal degradation of sepiolite were evaluated with a new method based on thermal analysis data. Thermogravimetric/differential thermal analysis curves were recorded for the natural and preheated sepiolite samples in the temperature range 25–800°C for 4 h. The temperature-dependent height of the exothermic heat flow peak for the thermal decomposition of sepiolite located at ~850°C on the differential thermal analysis curve was taken as a kinetic variable for the thermal degradation. A thermal change coefficient was defined depending on this variable because this coefficient fit to the Arrhenius equation was assumed as a rate constant for the thermal degradation. The Arrhenius plot showed that the degradation occurs in three steps. Two of these are due to stepwise dehydration and the third originated from dehydroxylation of sepiolite. Three activation energies were obtained that increase with the increasing temperature interval of the steps.

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Section: Kinetic Considerationssupporting

confidence: 76%

Thermal degradation kinetics of sepiolite

2020

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“…For kinetic interpretations of the collected XRD spectra, the relative analysis workflow is modelled after Sarikaya et al with appropriate modifications 63 . Using Dioptas, simultaneous background optimization on all XRD patterns was performed 64 .…”

Section: Resultsmentioning

confidence: 99%

Dehydration kinetics of nanoconfined water in beryl probed by high temperature single crystal synchrotron X-ray diffraction

Nguyen,

Zhang,

et al. 2024

Sci Rep

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Understanding changes in material properties through external stimuli plays a key role in validating the expected performance of materials and engineering material properties in a controlled manner. Here, we introduce a fundamental protocol to deduce dehydration reactions kinetics of water confined in nanopore channels, with the cyclosilicate beryl as the scaffold of interest, using time-resolved synchrotron X-ray diffraction (SXRD), in the temperature interval of 298–1038 K. The temperature-dependent intensity $$(I)$$ ( I ) of the strongest reflection (112) was used as the crystallite variable. An estimation of an isobaric thermal crystallite coefficient, $$k$$ k , analogous with the isobaric thermal expansion coefficient, established the rate of relative crystallization as a function of temperature, $$\frac{\partial I}{\partial T}$$ ∂ I ∂ T . A plot of $$lnk$$ lnk and $$\frac{1}{T}$$ 1 T gives rise to two kinetic steps, indicating a slow dehydration stage up to ~ 700 K and a fast dehydration stage up to the investigated temperature 1038 K. The crystal structure of beryl determined up to 1038 K, in temperature increment as small as 10 K, indicates the presence of channel ions Na and Fe and a gradual decrease of water upon heating.

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“…Natural moisture occupies the mesoporosity of clays and the corresponding water molecules are removed by thermal treatment below 300 • C. From this temperature, structural OH groups also begin to be lost. These aspects are crucial since the treatment under higher temperature conditions can detrimentally affect the properties of the clays by causing a loss of crystallinity and a variation in morphological features due to the irreversible dehydration and dehydroxylation, thus making it impossible to recover the clays [30,31]. Then, MTGA profiles were recorded up to 260 • C, and they were used to investigate the behavior of the adsorbed water.…”

Section: The Thermal Treatment Effect On the Behavior Of The Adsorbed...mentioning

confidence: 99%

“…Mild thermal treatment can remove moisture without significantly modifying the clay structure, and it has been found to enhance the uptake of organic guest molecules [27,29]. The coordination water, which is bonded to octahedral Mg 2+ at the edges (Mg-OH 2 ), is important for preserving the crystal structure of clays, and its loss at temperatures over 300 • C leads to a reduction in crystallinity [30,31]. Thus, thermal treatment at high temperatures causes profound changes in clay morphology, significantly reducing the accessible surface area of the micro-and mesoporous structures, and as a consequence, the adsorption properties [29,32,33].…”

Section: Introductionmentioning

confidence: 99%

Thermogravimetric Analysis of Moisture in Natural and Thermally Treated Clay Materials

Lo Dico,

Lisuzzo,

Carcelén

et al. 2024

Materials

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Clays are a class of porous materials; their surfaces are naturally covered by moisture. Weak thermal treatment may be considered practical to remove the water molecules, changing the surface properties and making the micro- and/or mesoporosities accessible to interact with other molecules. Herein, a modulated thermogravimetric analysis (MTGA) study of the moisture behavior on the structures of five, both fibrous and laminar, clay minerals is reported. The effect of the thermal treatment at 150 °C, which provokes the release of weakly adsorbed water molecules, was also investigated. The activation energies for the removal of the adsorbed water (Ea) were calculated, and they were found to be higher, namely, from 160 to 190 kJ mol−1, for fibrous clay minerals compared to lamellar structures, ranging in this latter case from 80 to 100 kJ mol−1. The thermal treatment enhances the rehydration in Na-montmorillonite, stevensite, and sepiolite structures with a decrease in the energy required to remove it, while Ea increases significantly in palygorskite (from 164 to 273 kJ mol−1). As a proof of concept, the MTGA results are statistically correlated, together with a full characterization of the physico-chemical properties of the five clay minerals, with the adsorption of two molecules, i.e., aflatoxin B1 (AFB1) and β-carotene. Herein, the amount of adsorbed molecules ranges from 12 to 97% for the former and from 22 to 35% for the latter, depending on the particular clay. The Ea was correlated with AFB1 adsorption with a Spearman score of −0.9. When the adsorbed water is forcibly removed, e.g., under vacuum conditions and high temperatures, the structure becomes the most important, decreasing the Spearman score between β-carotene and Ea to −0.6.

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Kinetic and thermodynamic approaches on thermal degradation of sepiolite crystal using XRD-analysis

Cited by 10 publications

References 27 publications

Thermal degradation kinetics of sepiolite

Thermal degradation kinetics of sepiolite

Dehydration kinetics of nanoconfined water in beryl probed by high temperature single crystal synchrotron X-ray diffraction

Thermogravimetric Analysis of Moisture in Natural and Thermally Treated Clay Materials

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