On dehydroxylation mechanisms of a biotite in vacuo and in oxygen

The dehydroxylation mechanisms of a biotite in the temperature range 300–800° C at controlled oxygen pressures were studied by infrared (IR) and Mössbauer spectroscopies. At low pressure, the lack of O₂ delays the oxidation of Fe⁺² and simultaneous loss of hydrogen but favours the loss of OH associated with octahedral vacancies in comparison with heat treatment in air. Stoichiometrical considerations based on the facts that the octahedral cations are randomly distributed and all Fe⁺² is oxidized lead to the conclusion that all the OH groups initially coordinated to Fe⁺² must be lost during the oxidation process.     

云母分子式计算方案的选择

本文借助主成分分析证明了花岗岩类中黑云母的Fe~(3+)、Fe~(2+)和(OH+F)主要的数量关系不表现为氧羟铁云母置换,还讨论了水不足和水过剩对云母分子式计算结果的影响,进而提出了当处理一批未受明显脱羟基氧化的云母,尤其是当其中包括明显水过剩云母时,宜优先采用O=22计算分子式方案等建议。     

High temperature dehydroxylation of muscovite-2M1: a kinetic study by in situ XRPD

Muscovite-2M₁ shows a major phase transition at about 800°C, which is generally attributed in the literature to the structural dehydroxylation process, although a number of structural models have been proposed for the dehydroxylated phase, and different transformation mechanisms have also been put forward. The observed first order transformation involves an increase in the cell volume, and it is not clear to date how the cell expansion is related to the loss of hydroxyl groups. The phase change has been re-investigated here by in situ high temperature powder diffraction, both in non-isothermal and isothermal modes, to combine for the first time the structural and the kinetic interpretation of the transformation. The results unequivocally confirm that the reaction taking place in the temperature range 700–1000°C is truly a dehydroxylation process, involving the nucleation and growth of the high temperature dehydroxylated phase, having Al in 5-fold coordination. Structural simulations of the basal peaks of the powder diffraction patterns indicate that the model originally proposed by Udagawa et al. (1974) for the dehydroxylated phase correctly describes the high temperature phase. The kinetic analysis of the isothermal data using an Avrami-type model yields values for the reaction order compatible with a reaction mechanism limited by a monodimensional diffusion step. Apparent activation energy of the process in vacuum is about 251 kJ/mol. Experiments carried out at temperatures much higher than the onset temperature of the reaction show that the dehydroxylation reaction overlaps with the reaction of formation of mullite, the final product in the reaction pathway. Received: 24 April 1998 / Revised, accepted: 12 October 1998     

FTIR spectra of hydroxyls and dehydroxylation kinetics mechanism in montmorillonite

The application of Fourier transform infrared (FTIR) spectroscopy to the analysis of the hydroxyl groups bands' intensities of montmorillonite from Texas shows four regions of intensity loss rate for thermally shocked samples at 290<T<1100 K for 24 h. The first three regions are associated with the dehydroxylation process; while the fourth region suggests the loss of the remaining (～10%) hydroxyls via thermal dissociation into hydrogen atoms and oxygen centers. The dehydroxylation process appears to be homogeneous with adjacent trans OH ions interacting to form H₂O molecules below the hexagonal hole or cavity. The vibrational analysis of the stretching and bending modes of water and hydroxyl groups at 290<T<553 K indicates not only that water is desorbed in this range, resulting in the perturbation of the octahedral hydroxyl structure due to the close approach of exchangeable cations to the hexagonal holes, but also that surface hydroxyls and AlFe³⁺-OH groups are dehydroxylated. AT 553<T< 773 K, the intensity loss of AlAl-OH and AlMg-OH groups almost varies linearly as a function of thermal shock temperature with the AlMg-OH vibration disappearing at T> 673 K. However, what is surprising is the persistence of very weak water stretching (～3470 cm^?1) and bending (～1628 cm^?1) vibrations at 553<T<773 K. It is speculated that this water, formed because of dehydroxylation, is trapped in the hexagonal cavities of the dehydrated montmorillonite lattice. However, conclusive evidence will require surface-sensitive spectroscopic measurements as this water could also be adsorbed on the external surfaces of processed samples. In the range 773<T<823 K, the main dehydroxylation of the AlAl-OH group results, and this reaction induces structural transformations in the montmorillonite lattice. FTIR measurements at 803 K for 0<t< 25 h were used to determine the kinetics mechanism of dehydroxylation in montmorillonite from Texas. The experimental data was tested, using diffusion controlled as well as six decomposition models to ascertain the kinetics mechanism of the AlAl-OH group's dehydroxylation. It appears that the dehydroxylation process can be described by the contracting spherical movement model rather than by a diffusion controlled model, suggesting surface nucleation, growth over the surface, and then advancement of the dehydroxylated/hydroxylated interface toward the center of the montmorillonite particles.     

酸化对蒙脱石成分和结构影响的研究

通过对高州蒙脱石及其酸化产物的X射线衍射、化学全分析、魔角旋转核磁共振谱（MASNMR）的研究发现,酸化导致蒙脱石成分和结构都发生一定程度的变化,特别是魔角旋转核磁共振谱研究发现,高州蒙脱石分别在八面体片和四面体片中存在六配位铝和四配位铝;其酸化产物由于八面体片内脱羟基,新出现了一类四配位铝。蒙脱石酸化后物化性能的改善至少与酸化引起的层间域中离子交换、八面体片内阳离子溶出及八面体片内脱羟基等因素有关。     

Hydrogen bonding and vibrational properties of hydroxy groups in the crystal lattice of dioctahedral clay minerals by means of first principles calculations

The hydroxy groups of the crystal lattice of dioctahedral 2:1 phyllosilicates were investigated by means of quantum-mechanical calculation. The standard Kohn-Sham self-consistent density functional theory (DFT) method was applied using the generalized gradient approximation (GGA) with numerical atomic orbitals and double-zeta polarized functions as basis set. Isomorphous cation substitution of different cations in the octahedral and tetrahedral sheet was included along with several interlayer cations reproducing experimental crystal lattice parameters. The effect of these substitutions and the interlayer charge on the hydroxyl group properties was also studied. These structures represent different cation pairs among Al³⁺, Fe³⁺ and Mg²⁺ in the octahedral sheet of clays joined to OH groups. The geometrical disposition of the OH bond in the crystal lattice and the hydrogen bonds and other electrostatic interactions of this group were analyzed. The frequencies of different vibrational modes of the OH group [(OH), (OH) and (OH)] were calculated and compared with experimental data, finding a good agreement. These frequencies depend significantly on the nature of cations which are joined with, and the electrostatic interactions with, the interlayer cations. Besides, hydrogen-bonding interactions with tetrahedral oxygens are important for the vibrational properties of the OH groups; however, also the electrostatic interactions of these OH groups with the rest of tetrahedral oxygens within the tetrahedral cavity should be taken into account. The cation substitution effect on the vibration modes of the OH groups was analyzed reproducing the experimental behaviour.Dr. V. Botella passed away last February     

Dehydroxylation induced structural transformations in montmorillonite: an isothermal FTIR study

Fourier transform infrared (FTIR) measurements on thermally shocked (290T<1100 k,="">t=1 and 24 h) and thermally soaked (T=803 K, 0t<25 h)="" ca-montmorillonite="" from="" texas="" show="" that="" the="" dehydroxylation="" temperature="" for="" this="" mineral="" is="" much="" lower="" than="" previously="" reported="" in="" the="" literature="" and="" depends="" upon="" the="" thermal="" soak="" time="" used.="" the="" effect="" of="" thermal="" shock="" temperature="" on="" vibrational="" frequencies,="" originating="" from="" the="" silicate="" sheet,="" and="" the="" intensity="" of="" al-oh-al="" stretching="" mode="" suggest="" that="" camontmorillonite="" dehydroxylates="" at="" 903="">T<923 k="" and="">T<823 k="" for="" 1="" h="" and="" 24="" h="" thermally="" shocked="" samples,="" respectively.="" our="" similar="" measurements="" on="" the="" mn="" and="" fe="" exchanged-montmorillomte="" from="" texas="" demonstrate="" that="" the="" dehydroxylation="" temperature="" range="" is="" also="" affected="" by="" the="" type="" of="" cations="" present="" in="" the="" interlayer.="" the="" thermal="" soak="">T=803 K, 0t<25 h)="" measurement="" on="" ca-montmorillonite="" indicates="" that="" the="" dehydroxylation="" of="" this="" montmorillonite="" proceeds="" via="" the="" development="" of="" intermediate="" structural="" phases.="" as="" noted="" by="" previous="" authors,="" the="" dehydroxylation="" of="">²⁺ and Fe³⁺ octahedral sites does not affect the overall structure. However, if 75 percent of the hydroxyls attached to Al³⁺ are lost, then the lattice manifests an intermediate structural phase. In this intermediate phase, the structure of both octahedral and silicate layers is affected. On a further loss of hydroxyls (90% of Al³⁺ hydroxyls), the final montmorillonite dehydroxylate phase develops. The vibrational analysis of an isothermally treated sample suggests that the final phase is induced due to the rearrangement of the silicate oxygens, which leave the coordination around Al to be 5. The dehydroxylation results of montmorillonite (Texas) have been discussed in terms of known mechanisms, and it appears that the dehydroxylation starts at the surface and proceeds via proton delocalization at trans hydroxyl positions, followed by the protons' migration across the vacant cation sites with the formation of H₂O molecules below the hexagonal holes.     

Infrared and electron microprobe analysis of tourmalines

Infrared and electron microprobe analysis of natural tourmalines from the dravite-schorl and elbaite-schorl series were carried out. The infrared study differentiates between OH groups located at the centre of hexagonal rings and those which are placed between hexagonal pillars and are coordinated to two Al ions. The correlation of infrared spectra with chemical composition of tourmalines made possible the assignment of different OH stretching bands to the more frequent octahedral cation associations. The study of the thermal dehydroxylation of tourmalines in air indentified the IR bands corresponding to OH bonded to Fe⁺² ions in AlAlFe, AlFeLi or FeFeFe environments. The change in intensity of the OH absorption lines with the sample orientation has permitted the identification of several orientations of the OH bond axes. Electron microprobe analysis of zoned coloured samples has shown that the Fe, Mn distribution is partially ordered in some samples of the elbaite-schorl series.     

DFT study of the cation arrangements in the octahedral and tetrahedral sheets of dioctahedral 2:1 phyllosilicates

Quantum mechanical calculations based on the density functional theory (DFT) are used to study the crystal structures of dioctahedral 2:1 phyllosilicates. The isomorphous cation substitution is investigated by exploring different substitutions of octahedral Al³⁺ by Mg²⁺ or Fe³⁺, tetrahedral substitution of Si⁴⁺ by Al³⁺, and different interlayer cations (IC) (Na⁺, K⁺, Ca²⁺, and Mg²⁺). Samples with different kinds of layer charges are studied: only tetrahedrally charged, only octahedrally charged, or mixed octahedral/tetrahedral charged. The effect of the relative arrangements of these substitutions on the lattice parameters and total energy is studied. The experimental observation of segregation tendency of Fe³⁺ and dispersion tendency of Mg²⁺ in the octahedral sheet is reproduced and explained with reference to the relative energies of the octahedral cation arrangements. These energies are higher than those due to the IC/tetrahedral and IC/octahedral relative arrangements. The tetrahedral and octahedral substitutions that generate charged layers also tend to be dispersed. The octahedral cation exchange potentials change with the IC-charge/ionic radius value.     

Kinetics of illite dehydroxylation

Illite is a dioctahedral K-deficient mica with an interlayer cation content of 0.6–0.85 atoms per formula unit. 1M and 2M₁ are the illite polytypes more abundant in nature. Because illite is one of the major component of clays used for the production of traditional ceramics, the understanding of its high temperature transformations is of paramount importance for the knowledge of the structural and microstructural properties of fired ceramic products. To our knowledge, the study of the illite dehydroxylation kinetics has not been attempted to date. Hence, this work presents the investigation of the reaction mechanism of dehydroxylation of illite for the first time. The natural sample investigated in this study is a 1M-polytype from Hungary. Several classical methods of kinetic analysis were used (isoconversional method, Avrami method, direct fit with kinetic expressions, and others) to achieve a complete picture of the dehydroxylation mechanism. The proposed model for the dehydroxylation of illite is a multi-step reaction sequence with (1) condensation of the water molecule in the octahedral layer; (2) one-dimensional diffusion of the water molecules through the tetrahedral ring (rate limiting step of the reaction); (3) two-dimensional diffusion of the water molecules through the interlayer region (rate limiting step of the reaction).     

On the mechanisms for H and Al incorporation in stishovite

The solubility and incorporation mechanisms of hydrogen in synthetic stishovite as a function of Al₂O₃ content have been investigated. Mechanisms for H incorporation in stishovite are more complex than previously thought. Most H in stishovite is incorporated via the Smyth et al. (Am Mineral 80:454–456, 1995) model, where H docks close to one of the shared O–O edges, giving rise to an OH stretching band in infrared (IR) spectra at 3,111–3,117 cm⁻¹. However, careful examination of IR spectra from Al-stishovite reveals the presence of an additional OH band at 3,157–3,170 cm⁻¹. All H is present on one site, with interstitial H both coupled to Al³⁺ substitutional defects on adjacent octahedral (Si⁴⁺) sites, and decoupled from other defects, giving rise to two distinct absorption bands. Trends in IR data as a function of composition are consistent with a change in Al incorporation mechanism in stishovite, with Al³⁺ substitution for Si⁴⁺ charge-balanced by oxygen vacancies at low bulk Al₂O₃ contents, and coupled substitution of Al³⁺ onto octahedral (Si⁴⁺) and interstitial sites at high bulk Al₂O₃ contents. Trends in OH stretching frequencies as a function of Al₂O₃ content suggest that any such change in Al incorporation mechanism could alter the effect that Al incorporation has on the compressibility of stishovite, as noted by Ono et al. (Am Mineral 87:1486–1489, 2002).     

Kinetics of the (Fe2++OH−)mica→(Fe3++O2−)mica+H oxidation reaction in bulk single-crystal biotite studied by Mössbauer spectroscopy

We report the first kinetic study of iron oxidation in a mica. Large singly-crystal biotite wafers were heated in air to various temperatures and for various times. Room temperature ⁵⁷Fe Mössbauer spectroscopy was used to quantify the resulting Fe²⁺ and Fe³⁺ amounts. A simple activation model is consistent with the measurements and gives an activation energy of e _b = 2.36 eV and an attempt frequency of f ₀ = 2.9×10⁷ Hz. We are lead to propose that, iron oxidation and ordinary dehydroxylation have the same rate limiting step: local dissociation of an OH group as OH^?→O^2-+H⁺. In oxidation this is followed by Fe²⁺ +H⁺→Fe³+H whereas in dehydroxylation it is followed by OH^? +H⁺→H₂O.     

Prediction of Gibbs free energies of formation of minerals of the alunite supergroup

A method for the prediction of Gibbs free energies of formation for minerals belonging to the alunite family is proposed, based on an empirical parameter Δ_GO⁼ M^z+(c) characterizing the oxygen affinity of the cation M^z+. 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 difference of oxygen affinity Δ_GO⁼ M^z+(c) between any two consecutive cations. The Δ_GO⁼ M^z+(c) value, using a weighing scheme involving the electronegativity of a cation in a specific site (12-fold coordination site, octahedral and tetrahedral) is assumed to be constant. It can be calculated by minimizing 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 gives values within 0.5% of the experimentally measured values. The relationships between Δ_GO⁼ M^z+(alunite) corresponding to the electronegativity of a cation in either dodecahedral sites, octahedral sites or tetrahedral sites and known as Δ_GO⁼ M^z+(aq) were determined, thereby allowing the prediction of the electronegativity of rare earth metal ions and trivalent ions in dodecahedral sites and highly charged ions in tetrahedral sites. This allows the prediction of Gibbs free energies of formation of any minerals of the alunite supergroup (bearing various ions located in the dodecahedral and tetrahedral sites). Examples are given for hydronium jarosite and hindsalite, and the results appear excellent when compared to experimental values.     

Thermally induced cation migration in Na and Li montmorillonite

In order to determine whether Li⁺ cations penetrate into the octahedral layers of montmorillonites upon mild heating (Hofmann-Klemen effect) ⁵⁷Fe Mössbauer spectra of Na⁺ and Li⁺ exchanged montmorillonite were obtained before and after treatment at 220 ° C. The ⁵⁷Fe nucleus was used as a remote probe to detect electronic perturbations which would occur if a Li cation was to move into the octahedral layer from the interlayer after heating. The ambient Mössbauer spectra showed that a high charge density interlayer cation such as Li⁺ is effective in reducing the phonon energy of ^VIFe²⁺. In addition the EFG at octahedral sites can be significantly modified by interlayer cations as evidenced by the larger quadrupole splitting value measured for the Li⁺-exchanged sample with respect to the Na⁺-sample. Interlayer collapse and migration of exchange cations into the montmorillonite lattice after heating to 220 ° C resulted in the oxidation of the ^VIFe²⁺ and a decrease in site distortion for ^IVFe³⁺. Similar spectral parameters for the Fe³⁺ resonances of both Na⁺ — and Li⁺-heated samples suggested the interlayer cations do not penetrate as far as the octahedral layers. In order to utilize the enhanced sensitivity of ^VIFe²⁺ Δ values to changes in EFG the Fe³⁺ in the heated montmorillonites was reduced to Fe²⁺ with hydrazine. Similar spectral parameters for both the Na⁺ — and Li⁺-exchanged montmorillonite were observed giving further evidence that Li cations do not migrate into vacant octahedral sites.     

Structural changes and oxidation of ferroan phlogopite with increasing temperature: in situ neutron powder diffraction and Fourier transform infrared spectroscopy

The thermal response of the natural ferroan phlogopite-1M, K₂(Mg_4.46Fe_0.83Al_{0. 34}Ti_0.22)(Si_5.51Al_{2. 49})O₂₀[OH_3.59F_0.41] from Quebec, Canada, was studied with an in situ neutron powder diffraction. The in situ temperature conditions were set up at ?263, 25, 100°C and thereafter at a 100°C intervals up to 900°C. The crystal structure was refined by the Rietveld method (R _p=2.35–2.78%, R _wp=3.01–3.52%). The orientation of the O–H vector of the sample was determined by the refinement of the diffraction pattern. With increasing temperature, the angle of the OH bond to the (001) plane decreased from 87.3 to 72.5°. At room temperature, a = 5.13 Å, b = 9.20 Å, c = 10.21 Å, β = 100.06° and V(volume) = 491.69 ų. The expansion rate of the unit cell dimensions varied discontinuously with a break at 500°C. The shape of the M-octahedron underwent some significant changes such as flattening at 500°C. At temperatures above 500°C, the octahedral thickness and mean distance was decreased, while the octahedral flattening angle increased. Those results were attributed to the Fe oxidation and dehydroxylation processes. The dehydroxylation mechanism of the ferroan phlogopite was studied by the Fourier transform infrared spectroscopy (FTIR) after heated at temperatures ranging from 25 to 800°C with an electric furnace in a vacuum. In the OH stretching region, the intensity of the OH band associated with Fe²⁺(N _B-band) begun to decrease outstandingly at 500°C. The changes of the IR spectra confirmed that dehydroxylation was closely related to the oxidation in the vacuum of the ferrous iron in the M-octahedron. The decrease in the angle of the OH bond to the (001) plane, with increasing temperature, might be related to the imbalance of charge in the M-octahedra due to Fe oxidation.     

基于等转化法及多元非线性拟合的高岭石非等温脱羟基动力学分析

采用Netzsch STA409PC同步热分析仪研究了苏州高岭石(KW125)在30℃~1 200℃间的热分解过程。采用"Netzsch Thermokinetics software"软件对其脱羟基机理进行了非等温动力学研究。基于等转化法评价了反应活化能及反应进程的依存关系。基于多元非线性拟合确定了最可能反应机理及动力学参数。研究结果表明:苏州高岭石在30℃~1200℃温度范围的热分解为脱羟基与相转变等两个阶段。其脱羟基(30℃~800℃)过程中活化能呈现三个变化:197.68 kJ/mol±12.95 kJ/mol→181.04kJ/mol±18.98kJ/mol→269.7kJ/mol±14.64kJ/mol。脱羟基反应遵循三步连续反应模型t:f,f;(D3-Fn-Fn),一个三维扩散(D3)反应,然后是两个n序列(Fn)反应。第一步,f(α)=3(1-α)^2/3/(2(1-(1-α)^1/3),E1=185.27 kJ/mol,logA=10.83s^-1;第二步,f(α)=(1-α)^n,n=1.75,E2=187.81 kJ/mol,logA=10.32s^-1;第三步,f(α)=(1-α)^n,n=4.4,E3=262.70 kJ/mol,logA=13.26s^-1。     

A regular solution site-mixing model for illites

The dependence on the composition of the thermodynamic stability of an illite can be treated in terms of a regular solution site-mixing model. Four end-member micas (muscovite, pyrophyllite, phlogopite, and annite) were mixed to simulate an illite in this study. In the model, random mixing of cations was assumed over each given class of cation sites. Mixing over cation sites between different classes of cation sites was not allowed. The resulting free energy and chemical potential equations contain four site interaction parameters: three for octahedral site interactions and one for interlayer and tetrahedral site interactions. These parameters cannot presently be evaluated because of a lack of experimental data on Fe³⁺-free illites. The model does imply that the octahedral site interaction parameters must be significantly more positive than the interlayer and tetrahedral site interaction parameter to account for the dominant dioctahedral nature of most natural illites. This constraint is necessary to balance out the increase in stability due to the configurational entropy of an illite having a major trioctahedral component.The model can be extended to cover a wider range of illite compositions by the inclusion of an end-member mica containing Fe³⁺ ions in the octahedral sites. At present the thermodynamic properties of such an end-member are unknown.     

Neutron irradiation and post-irradiation annealing of rutile (TiO2−x ): effect on hydrogen incorporation and optical absorption

Neutron irradiation and post-irradiation annealing under oxidising and reducing conditions have been used to investigate H incorporation in, and the optical properties of, reduced (TiO_2−x ) rutile. Optical absorption in rutile is mainly due to a Ti³⁺ Ti⁴⁺ intervalence charge transfer effect. The main mechanism for H incorporation in rutile involves interstitial H not coupled to other defects, which has important implications for the rate of H diffusion, and possibly also on the electrical properties of rutile. Additional minor OH absorption bands in IR spectra indicate that a small amount of interstitial H is coupled to defects such as Ti³⁺ on the main octahedral site, and indicates that more than one H incorporation mechanism may operate. Concentration of oxygen vacancies has a controlling influence on the H affinity of rutile.     

Cation distribution and structure modelling of spinel solid solutions

 This paper presents an improved generalisation of cation distribution determination based on an accurate fit of all crystal-chemical parameters. Cations are assigned to the tetrahedral and octahedral sites of the structure according to their scattering power and a set of bond distances optimised for spinel structure. A database of 295 spinels was prepared from the literature and unpublished data. Selected compositions include the following cations: Mg²⁺, Al³⁺, Si⁴⁺, Ti⁴⁺, V³⁺, Cr³⁺, Mn²⁺, Mn³⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺ and vacancies. Bond distance optimisation reveals a definite lengthening in tetrahedral distance when large amounts of Fe³⁺ or Ni²⁺ are present in the octahedral site. This means that these cations modify the octahedral angle and hence the shared octahedral edge, causing an increase in the tetrahedral distance with respect to the size of the cations entering it. Some applications to published data are discussed, showing the capacity and limitations of the method for calculating cation distribution, and for identifying inconsistencies and inaccuracies in experimental data. Received: 19 February 2001 / Accepted: 1 June 2001     

Thermal decomposition of NH4-analcime

The thermal decomposition of ammonium-exchanged natural analcime is characterized by gas chromatography, IR spectroscopy and X-ray diffraction. The de-ammoniation and dehydroxylation proceed in parallel throughout the decomposition, which evidences the instability of the protonated analcime framework. The mechanism of degassing of NH₄-analcime changes throughout its decomposition. At the initial step, the mechanism of de-ammoniation consists in thermal dissociation of NH₄⁺ molecule onto NH₃ and proton (framework OH group) and diffusion of NH₃ out of the structure. Subsequent decomposition and removal of the OH groups lead to a progressive loss of crystallinity. At this step, an apparent activation energy for NH₃ desorption is estimated to be 145(±13) kJ mol^–1. This value is within the upper limit of the activation energy characteristic for the NH₃ desorption from proton centres in large-pore zeolites. At the final step, the adsorption of NH₃ and protons onto the defect centres in the amorphosed aluminosilicate framework results in a significant increase of an apparent activation energy for the de-ammoniation and dehydroxylation up to 270(±20) kJ mol^–1.