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Article

Crystal Transformation of Sericite during Fluidized Roasting: A Study Combining Experiment and Simulation

by
Zhe Bai
1,2,
Yuexin Han
1,2,
Jianping Jin
1,2,
Yongsheng Sun
1,2,* and
Qi Zhang
1,2
1
School of Resources and Civil Engineering, Northeastern University, Shenyang 110819, China
2
National-Local Joint Engineering Research Center, High-Efficient Exploitation Technology for Refractory Iron Ore Resources, Shenyang 110819, China
*
Author to whom correspondence should be addressed.
Minerals 2022, 12(10), 1223; https://doi.org/10.3390/min12101223
Submission received: 1 September 2022 / Revised: 23 September 2022 / Accepted: 23 September 2022 / Published: 27 September 2022
(This article belongs to the Special Issue Mineral Processing Technologies of Complex Refractory Iron Ore)
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Abstract

:
Fluidized roasting is an efficient method to promote vanadium extraction from V-bearing mica in shale. In this study, the transformation behavior of V-bearing sericite during fluidized roasting was explored by combining experimental detections and density functional theory (DFT) calculations. TG-MS, XRD, FTIR, and SEM-EDS were used to investigate the characteristics of the roasted sericite samples. The crystal parameters of V-bearing sericite were calculated with Materials Studio. The results showed that dehydroxylation was the main reaction during roasting, which occurred between 650 °C and 960 °C. After being roasted at 900 °C for 2 h, hydroxyls were completely removed. The calculation results show that −OH was removed between the metal ions in the sericite O-layer, which turned the hexa-coordinate of V3+, Al3+, and Fe3+ into pentacoordinate. Through electronic rearrangement, the bond lengths between two ions connected by −OH were shortened from 0.18~0.20 nm to 0.17 nm. However, some chemical bonds were grown, which indicates that they are weaker and easier to transform. In addition, twisted six-membered rings were formed with obvious angle changes on the (0 0 1) surface. Furthermore, Mulliken’s overlap populations of some V-O, Al-O, and Fe-O were decreased. Therefore, dehydroxylation is a determining factor in the destruction of sericite crystals during fluidized roasting, which also promotes vanadium release from shale.

Graphical Abstract

1. Introduction

Vanadium is a significant rare-metal element and strategic resource [1,2]. It has been extensively applied to the steel industry, special alloy, chemical industry, superconducting materials, vanadium batteries, and more [3,4,5]. There is a huge consumption of vanadium in China, but 87% of vanadium is stored in shale, which amounts to 118 million tons (estimated by V2O5) [6,7,8]. Shale is a type of carbonaceous shale with a low calorific value [9,10]. The low grade of V2O5 (0.13%~1.2%), complex minerals composition, and various occurrence states of vanadium are characteristics of shale [11,12]. In addition, V3+ often replaces the Al3+ in mica crystal with isomorphism. However, V2O3 has little solubility in acid [13], meaning vanadium is difficult to directly leach from shale. This results in low recovery, waste medicine, difficult purification, and high cost in current processes [14,15,16].
Common vanadium extraction processes include sodium roasting-water leaching, sodium roasting-acid leaching, calcification roasting-acid/alkali leaching, and direct acid leaching [17,18,19,20]. At present, many additives have been developed, including NaCl, Na2CO3, Na2SO4, CaO, CaCO3, CaF2, etc. [18,21,22]. The vanadium leaching rate reached 86.74% under the conditions of CaF2:CaO = 2:3, an additive amount of 10 wt%, and roasting at 850 °C for 90 min. Additives could react with minerals to destroy crystal structures under lower temperatures, shorter time, or less acid solution [18]. Molten NaCl would rather react with silicate rocks, which results in crystal transformation and promotes vanadium dissociation. Studies confirmed that the key point of enhancing leaching efficiency is to destroy the crystal structure of V-bearing minerals before the leaching process [23]. However, roasting with additives will cause serious pollution and consume lots of acidic or alkaline agents.
At present, blank roasting is being considered as a better choice to replace original technologies [23,24,25] because of its advantages, such as containing no additives, a low reagent consumption, and less pollution. The vanadium leaching efficiency in a blank roasting–acid leaching process reached 85.43% under the comparative leaching condition of 15% H2SO4 (v/v), 1 mL/g, 4 h, 95 ± 1 °C, and 5% CaF2 (w/w) [19]. Previous studies have shown that the crystal structure of V-bearing muscovite was effectively destroyed by fluidized roasting, which promotes the release of vanadium [26]. However, the micro-damage mechanism of V-bearing muscovite by high-temperature fluidized roasting was lacking. Muscovite is the most widely distributed V-bearing mineral in shale, which leads to difficulty with leaching. Thus, some researchers studied the crystal parameters of V-bearing muscovite based on density functional theory (DFT) [27]. The results showed that the most plausible site of V was the octahedral structure in the O-layer of muscovite, and destroying this octahedral structure was key to enhancing the leaching rate of vanadium. Moreover, the bond parameters, bond angles, bond length, populations, and electron distribution were analyzed in substituted V-bearing muscovite [27,28,29,30]. During acid dissolution, the removal process of structural atoms in muscovite during acid leaching [31], and the removal of structural O and Al in the octahedron were also researched [32]. The structure and relative potential energy of the intermediate products were carefully calculated and described, which was valuable work.
In this study, experimental studies and density functional theory (DFT) calculations were innovatively combined to study the transformation of V-bearing sericite, which is a kind of fine V-bearing muscovite, and its crystal during fluidized roasting. TG-MS, XRD, FTIR, and SEM-EDS were used to analyze the thermolysis, chemical bonds, phase transition, and microstructure of sericite samples, respectively. Furthermore, V-bearing sericite crystals before and after dehydroxylation were constructed to intuitively demonstrate the transformation of crystal parameters, bond angle, bond length, and populations. It also explained the promoting effect of fluidized roasting from the perspective of crystal damage.

2. Materials and Methods

2.1. Materials

The sericite was obtained from Shijiazhuang Country, Hebei Province of China. In this research, pure sericite was used to substitute pure V-bearing sericite because it is difficult to obtain pure V-bearing sericite in nature. Although there are slight differences between them, their properties and structures are rather similar, which meets the requirements of this research. Figure 1 shows the results of particle size analyzed by a laser particle sizer, in which the content at −45 µm was more than 73%. The chemical compositions of sericite are presented in Table 1, which were determined by chemical analysis. As the main components of sericite, the contents of Al2O3, K2O, and SiO2 are 30.82 wt%, 10.54 wt%, and 49.25 wt%, respectively. The mineral composition of the ore sample was defined by XRD. Figure 2 shows that the characteristic peaks of sericite correspond well with that of sericite, as there are no other minerals’ peaks. It indicates that this sericite is of high purity and meets the requirement of this research.

2.2. Methods and Equipment

Figure 3 shows the schematic of the sericite fluidized roasting system. The samples were heated by vertical furnace equipment (OTF-1200X-S-VT, HF-Kejing, Hefei, China) from 25 °C to 1050 °C. A furnace tube (Φ 50 mm) with an internal breathable quartz plate was the core reactor. O2 and N2 gas (purity of 99.99%) supplied a flowing oxidation atmosphere controlled by rotary flowmeters (LZB-3WB, Shengzhiyuan, China). First, 20.00 g sericite was charged onto the quartz plate inside the reactor. Then, the connected furnace tube was put into the furnace cavity, which reached a set temperature. O2 (126 mL/min) and N2 (474 mL/min) were injected into furnace tubes. Under this condition, fluidized roasting would last for 2 h. Raw ore and roasted products were analyzed by TG-MS, XRD, FTIR, and SEM-EDS. In addition, the crystal calculation would illustrate the crystal transformation before and after roasting. Calculation parameters of the CASTAP module of Material Studio were as follows (DFT): the exchange-correlation functional selected GGA-PBE, the pseudopotential selected Ultra-soft, the cut-off energy was 400 eV, and the K-point was the Gamma point (1 × 1 × 1). This crystal structure of sericite was downloaded from the American Mineralogist Crystal Structure Database (AMCSD). Crystals of V-bearing sericite and dehydroxylated V-bearing sericite were clearly compared and analyzed in crystal parameters (bond angle, length, population, and bond strength).

2.3. Analytical Methods

The particle size of sericite powder was determined by a laser particle sizer (Malvern Panalytical Mastersizer 3000, Malvern, UK). The phase composition of roasted products was studied by X-ray diffraction analysis (XRD, Panalytical X Pertpro, Almelo, The Netherlands). Samples were scanned within a 2θ range of 5~75°; then, the patterns were analyzed by JADE software (version 6.0, Materials Data, Newtown Square, PA, USA). Thermogravimetry combined with mass spectrometry (TG-MS, NETZSCH STA 449F3, Selb, Germany) was used to analyze the thermal decomposition process of sericite [33]. Furthermore, Fourier transforms infrared spectroscopy (FTIR, Nicolet 380, Scientific, Masyland, USA) was employed to investigate the transformations in the chemical bonds. Based on the first principle, the crystal structure of sericite was calculated using Materials Studio software (version 2019). Microstructures and elements distribution of samples were observed by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS, Zeiss Ultra Plus, Germany, and OXFORD X-MAXN, Oxford, UK).

3. Results and Discussion

3.1. Thermal Decomposition Analysis

Thermogravimetry-mass spectrometry (TG-MS) was used to investigate the pyrolysis behavior of the sericite [34,35]. The heating rate of TG-MS is 15 °C/min under in air. As shown in Figure 4, the pyrolysis process can be divided into three stages. The first stage was from room temperature to 650 °C. The mass loss of this stage was 0.81%, which is due to the removal of some adsorbed water and crystal water [34]. Because the water content was low, changes to the TG curve and ion intensity of H2O were small. In the second stage, from 650 °C to 960 °C, the mass loss reached 3.20%. It was demonstrated that a violent dehydroxylation reaction began at 650 °C and completely ended at 960 °C. The ion intensity of H2O had an obvious peak in this range, revealing that the hydroxyls inside sericite crystal were removed between 650 °C and 960 °C in the form of H2O [34,36]. Furthermore, the peak values of the DTG curve and H2O curve were located at 850 °C and 855 °C, respectively, indicating that the maximum reaction rate occurred at 850 °C. Therefore, the effective roasting temperature for crystal damage should be above 850 °C. In contrast, the weight loss was only 0.18% at the third stage (i.e., from 960 °C to 1200 °C) because the decomposition reaction was very weak.

3.2. Transformation Behaviors of Sericite

3.2.1. Transformation of Chemical Bonds

Figure 5 shows the FTIR spectra of raw ore and roasted products (800 °C, 850 °C, 900 °C, 950 °C, and 1050 °C). Bands at 3623.23 cm−1 and 825.93 cm−1 were attributed to stretching vibrations and oscillating absorption of -OH, respectively [37,38]. Bands at 3623.23 cm−1 and 825.93 cm−1 disappeared completely when the roasting temperature reached 900 °C, indicating that the -OH in the crystal was completely removed. It was consistent with the analysis results of the TG-MS in Figure 4. In addition, Si(AlIV)-O and Si-O-Si(AlIV) were also changed (absorption bands at 798 cm−1, 748 cm−1, 693 cm−1, and 1027 cm−1, and shoulder absorption band at 1068 cm−1 [37]). As shown in Figure 5b, bands at 798 cm−1, 748 cm−1, and 693 cm−1 gradually weakened and disappeared at 900 °C with the increase in temperature. The bands at 1027 cm−1 and 1050 cm−1 also moved to low and high frequency, respectively. Then, the FTIR spectra basically remained unchanged when the temperature was above 900 °C. Figure 5 illustrates the main changes in this spectrum related to -OH, Si(AlIV)-O, and Si-O-Si(AlIV), indicating that dehydroxylation was accompanied by significant changes in Si(AlIV)-O and Si-O-Si(AlIV) during roasting.

3.2.2. Phase Transformation

The XRD patterns of sericite samples are shown in Figure 6. During fluidized roasting, the mineralogical phase changed from sericite to dehydroxylated sericite. With the increase in roasting temperature, the characteristic peaks of raw sericite at 36.1°, 45.5°, 69.6°, and 70.2° gradually weakened and then finally disappeared at 850 °C. Meanwhile, new peaks located at 35.6°, 45.0°, 64.7°, and 68.7° were attributed to the generation of dehydroxylated sericite. On the one hand, it was confirmed that the dehydroxylation reaction led to phase transformation during roasting. On the other hand, the roasting temperature should be higher than 850 °C to cause sericite crystal damage.
To further analyze the variation in crystal planes of roasted products, the interplanar spacings of diffraction peaks were measured, and the results are shown in Table 2. The interplanar spacings of (006), (002), (004), (008), and (025) increased continuously from raw ore to 850 °C. Among them, (006), (002), and (004) were changed at 850 °C, which were the three strongest peaks of sericite located at 26.8°, 17.8°, and 8.8° along the crystal c-axis. The interplanar spacings of (006), (002), and (004) increased from 0.3323 nm, 0.9973 nm, and 0.4984 nm to 0.3354 nm, 1.0040 nm, and 0.5029 nm, respectively, indicating that the sericite crystal was stretched and deformed along the c-axis. Because the ionic bond is the interlayer force between the layers of sericite crystal, deformation is most prone along with the c-axis. Hence, the crystal deformation of sericite along the c-axis was also accompanied by dehydroxylation.

3.2.3. Microstructure Analysis

Raw sericite and roasted products at 850 °C, 950 °C, and 1050 °C were imaged under SEM to analyze the microstructure at different temperatures. Figure 7 illustrates that sericite was composed of several thin layers with obvious flaky structures. Fine flake debris adhered to the sample surface, and the diameter of most debris was less than 2 μm. It could be observed that the edge and fracture of particles were sharp. When the temperature increased from 850 °C to 1050 °C, the scaly particles on the surface melted, and the sharp fracture gradually became smooth. Figure 7c shows the small spherical particles formed at 950 °C. Sintering phenomena occurred at 1050 °C, and the flake particles were fused to the bump structure and closely attached to the surface. Meanwhile, metal ions were wrapped inside the molten silicate formed by sintering.
Taking the raw ore and roasted product at the highest temperature, Figure 8 shows the element distribution at 1050 °C. Si, O, Al, K, and Fe were the main constituent elements of sericite (the chemical formula is K0.5–1(Al,Fe,Mg)2(SiAl)4O10(OH)2·nH2O) [39,40]. Figure 8a illustrates those elements had a good correlation with particles. Figure 8b shows that Si, O, Al, K, and Fe also had good correlations. This showed there was no element loss before and after dehydroxylation. The inclusion of V elements in the melt leads to a poor leaching effect of the sample [6,41]. Hence, too high a temperature should be avoided in the fluidized roasting process of shale.

3.3. DFT Calculation of Sericite Crystal

The DFT calculation could provide microcosmic and quantitative evidence for the analysis at an atomic scale [42]. Materials Studio software was used to estimate the microstructural transformation of V-bearing sericite during fluidized roasting [43].

3.3.1. Crystal Transformation during Dehydroxylation

Based on previous research, the best substitution position of the V3+ in the O-layer was determined [27]. Then, the crystal of V-bearing sericite was obtained as shown in Figure 9. An octahedral sheet with Al, V, Fe, and O is pinned between two tetrahedron sheets with Si and O, which formed a T-O-T layer structure. The T-layer is connected by the silica six-membered ring, and the O-layer is connected by the alumina six-membered ring [44]. Meanwhile, V3+ and Fe3+ usually replaced Al3+ by isomorphism in the O-layer [45,46]. Figure 10 shows the changes in sericite crystal before and after dehydroxylation. The calculated crystal parameters of raw ore were a = 0.8980 nm, b = 0.5177 nm, c = 2.1086 nm, α = 84.84°, β = 90.10°, and γ = 90.10°. In addition, the parameters of dehydroxylated sericite were a = 0.9116 nm, b = 0.5201 nm, c = 2.1181 nm, α = 85.78°, β = 90.49°, and γ = 89.86°. The values of a and c elongated were found to be 0.0136 nm and 0.0095 nm, respectively. The expansion along the c-axis was due to the weak force between the crystal layers [47]. Moreover, the expansion along the a-axis and the change in a, b, and c were mainly due to the crystal transformation inside the crystal cell.
The sericite O-layer could be regarded as the repeated arrangement of two types of six-membered rings. In the sericite (0 0 1) surface, the crystal change in the O-layer before and after dehydroxylation is shown in Figure 11. This reaction occurred between adjacent metal ions (V3+ and Al3+, and Fe3+ and Al3+) [38]. An H2O molecule was generated by the reaction of two −OH. Firstly, two connected O atoms were reduced to one between V3+ and Al3+, and Fe3+ and Al3+. Second, the coordination number of central ions decreased from 6 to 5, and the polyhedron pile model changed from hexa-coordinate to pentacoordinate. Finally, this reaction led to the rearrangement of electrons, the transformation of atomic sites, and the change in crystal parameters (a, b, c, α, β, and γ). These changes in microstructure correspond to the transformation of macro properties.

3.3.2. Analysis of Bond Parameters and Electron Population

Observed from the sericite (0 0 1) surface, the O-layer was composed of two kinds of six-membered rings with infinite repetition. Figure 11a illustrates the changes in bond length and bond angle, and Table 3 lists the distance between adjacent atoms. When -OH was removed between adjacent center atoms, two intermediate oxygen atoms became one. Near this position, the bond lengths of V-O, Al-O, and Fe-O (red mark) were shortened. However, other chemical bonds were increased from 0.1907~0.2037 nm to 0.1987~0.2097 nm, indicating that the strength of these chemical bonds decreased. Weakened chemical bonds make them easier to break when they react with acids. This is also one of the reasons why roasted samples are easier to leach [40,48].
The distance between central atoms increased obviously, which increased to 0.35 nm and 0.46 nm for Al-V and Al-Fe, respectively. In contrast, the distance for V-Fe decreased to 0.32 nm. Moreover, in the ring, the bond angles near -OH pointing inside (with white mark in Figure 11a) expanded from 87.07~95.89° to 109.41~128.08°. However, the bond angles near −OH pointing outside (yellow mark) reduced from 91.10~100.19° to 88.07~98.80°. The other angles changed only by a little. The results above suggest that the original hexagonal structure has been seriously distorted and that two kinds of twisted six-membered rings were formed.
Mulliken’s overlap population provides intuitive chemical information transformed from the wave function obtained by Molecular Orbital Theory. By distributing electronic charges to atoms, atomic orbitals, and chemical bonds, it is used to study the transfer of electrons in molecules, the polarity of molecules, as well as the type and strength of chemical bonds, etc. [49,50]. Additionally, it is dimensionless and has no physical meaning [51]. According to Mulliken's overlap populations of bonds and atoms, as well as atomic net charges (Figure 11b), electronic structures and bonding characters were discussed to clarify the transformation between sericite and dehydroxylated products. Mulliken’s overlap populations in the raw ore were all about 0.3, indicating that each bond presented the nature of the ionic bond and has similar strengths. The most obvious change occurred at the dehydroxylation site. When two O atoms were connected between the V and Al atoms—V-O and Al-O—Mulliken’s overlap populations were 0.26 and 0.32. After roasting, there was only one O atom between two atoms, and the populations of V-O and Al-O increased to 0.58 and 0.47, respectively. The law between Al and Fe was the same. This indicated that newly generated bonds tend to be covalent bonds with stronger strength. It should be noted that Mulliken’s overlap populations of some V-O, Al-O, and Fe-O decreased from 0.30, 0.35, and 0.27 to 0.27, 0.25, and 0.18, respectively. This indicated that their covalency was weakened and that they were easier to destroy. Furthermore, Mulliken’s overlap populations of atoms before and after dehydroxylation are presented in Table 4. V3+, Fe3+, and Al3+ in the O-layer were electron deficiency sites and the O atoms were multi-electron sites. After fluidized roasting, the electrons of the V3+ increased from 11.72 to 11.81, and Fe3+ increased from 7.04 to 7.13, while the electrons of the Al3+ decreased from 1.31~1.33 to 1.25. These results indicated electron transfer from Al3+ to O atoms rather than to V3+ and Fe3+ ions.
In summary, raw ore has a stable structure in which each parameter—bond angle, length, and population—is pretty close, and the O-layer is composed of an approximate hexagonal structure. However, after fluidized roasting, the metal ions in the sericite O-layer changed from hexa-coordinate to pentacoordinate. With the rearrangement of electrons, some bond lengths increased or decreased, and the bond strength also increased or decreased. This indicated that roasting would lead to forming more unstable chemical bonds and reducing crystal stability inside sericite crystals. This should be the reason vanadium and other metal ions are easier to leach out in the roasted product.

4. Conclusions

The transformation of sericite to dehydroxylated sericite was the main reaction during fluidized roasting. TG-MS revealed that this reaction could occur at 650~960 °C. When sericite was roasted at 900 °C for 2 h, their hydroxyls were completely removed. The calculations showed that -OHs were removed between V3+ and Al3+, and between Fe3+ and Al3+ in the sericite O-layer, which turned the hexa-coordinate structure of V3+, Al3+, and Fe3+ into pentacoordinate. It showed that their stable octahedron structure was destroyed into an unstable hexahedron structure. Meanwhile, the electrons were rearranged. Mulliken’s overlap populations were increased from 0.26~0.36 to 0.47~0.59. On the sericite (0 0 1) surface, the angles changed from 87.04~100.19° to 84.53~128.08°. In addition, Mulliken’s overlap populations of some other V-O, Al-O, and Fe-O decreased from 0.30 to 0.27, from 0.35 to 0.25, and from 0.27 to 0.18, respectively, indicating that their ionicities were weakened. Some bond lengths were increased; therefore, the strength of the chemical bonds was reduced and the bonds were fragile. The distorted hexahedron structure with fragile chemical bonds in the O-layer explained the destructive effect of fluidized roasting on the stability of V-bearing sericite.

Author Contributions

Conceptualization, Y.H. and J.J.; methodology, J.J.; software and validation, Z.B.; data curation and writing—original draft preparation, Z.B.; writing—review and editing, Y.S. and Q.Z.; visualization, Q.Z.; funding acquisition, J.J. All authors have read and agreed to the published version of the manuscript.

Funding

This research is funded by National Key Research and Development Program of China (grant No. 2020YFC1909704) and the Fundamental Research Funds for the Central Universities (No. N2201001).

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Minerals 12 01223 g001 550
Figure 1. Particle size distribution of sericite.
Figure 1. Particle size distribution of sericite.
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Minerals 12 01223 g002 550
Figure 2. The XRD pattern of raw sericite.
Figure 2. The XRD pattern of raw sericite.
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Minerals 12 01223 g003 550
Figure 3. Schematic of sericite fluidized roasting system.
Figure 3. Schematic of sericite fluidized roasting system.
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Minerals 12 01223 g004 550
Figure 4. TG-MS analysis of raw sericite.
Figure 4. TG-MS analysis of raw sericite.
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Minerals 12 01223 g005 550
Figure 5. FTIR spectra of raw ore (a) and roasted products (b).
Figure 5. FTIR spectra of raw ore (a) and roasted products (b).
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Minerals 12 01223 g006 550
Figure 6. XRD analysis of roasted products at different temperatures (raw ore (a), 700 °C (b), 850 °C (c), 900 °C (d), 950 °C (e), and 1050 °C (f)).
Figure 6. XRD analysis of roasted products at different temperatures (raw ore (a), 700 °C (b), 850 °C (c), 900 °C (d), 950 °C (e), and 1050 °C (f)).
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Minerals 12 01223 g007 550
Figure 7. SEM images of sericite samples at different temperatures (raw ore (a), 850 °C (b), 950 °C (c), and 1050 °C (d)).
Figure 7. SEM images of sericite samples at different temperatures (raw ore (a), 850 °C (b), 950 °C (c), and 1050 °C (d)).
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Minerals 12 01223 g008 550
Figure 8. Element distribution on the sample surface at different temperatures (raw sericite (a), 1050 °C (b)).
Figure 8. Element distribution on the sample surface at different temperatures (raw sericite (a), 1050 °C (b)).
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Minerals 12 01223 g009 550
Figure 9. The crystal structure of sericite before and after dehydroxylation.
Figure 9. The crystal structure of sericite before and after dehydroxylation.
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Figure 10. Structural change in sericite O-layer during dehydroxylation.
Figure 10. Structural change in sericite O-layer during dehydroxylation.
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Figure 11. Parameters of chemical bonds in the sericite (0 0 1) surface (bond angle and bond length (a), Mulliken’s overlap population (b)).
Figure 11. Parameters of chemical bonds in the sericite (0 0 1) surface (bond angle and bond length (a), Mulliken’s overlap population (b)).
Minerals 12 01223 g011
Table
Table 1. The chemical multi-elemental analysis of sericite.
Table 1. The chemical multi-elemental analysis of sericite.
CompositionAl2O3K2OSiO2Fe2O3CaOMgOTiO2
Content (wt%)30.8210.5449.255.210.141.300.70
Table
Table 2. The interplanar spacings of diffraction peaks of roasted products.
Table 2. The interplanar spacings of diffraction peaks of roasted products.
Crystal PlanesInterplanar Spacings/nm
Raw Sericite700 °C850 °C900 °C950 °C
(0 0 2)0.99500.99731.00411.00411.0063
(0 0 4)0.49820.49850.50290.50290.5035
(1 1 0)0.44710.45050.45030.44980.4501
(−1 1 4)0.34940.35000.35210.35170.3520
(0 0 6)0.33230.33240.33550.33550.3357
(1 1 4)0.32020.32050.32280.32270.3229
(0 2 5)0.29920.29950.30280.30270.3031
(1 1 5)0.28620.28650.28850.28860.2889
(−1 1 6)0.27910.27940.28140.28140.2816
(0 0 8)0.24930.24930.25160.25170.2518
(2 2 4)0.19940.19940.20130.20130.2014
(1 3 9)0.16470.16480.16660.16660.1666
Table
Table 3. Distance between adjacent center atoms before and after dehydroxylation.
Table 3. Distance between adjacent center atoms before and after dehydroxylation.
Distance/nmV1-Al1Al1-Al2Al2-Fe1Fe1-Al3Al3-Al4Al4-V1
Before3.113.002.983.063.003.13
After3.042.963.442.982.963.48
Distance/nmV1-Al1V1-Fe2Fe2-Al5Al5-Fe3Fe3-V2V2-Al1
Before3.112.682.983.062.683.13
After3.042.363.442.982.363.48
Table
Table 4. Mulliken population of atoms before and after dehydroxylation.
Table 4. Mulliken population of atoms before and after dehydroxylation.
IonsStates Orbitalp Orbitald OrbitalTotalCharge/e
V1Before2.256.173.3111.721.28
After2.206.213.4011.811.19
Al1Before0.500.81-1.311.69
After0.470.78-1.251.75
Al2Before0.510.81-1.331.67
After0.460.79-1.251.75
Fe1Before0.250.246.547.040.96
After0.260.356.527.130.87
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Bai, Z.; Han, Y.; Jin, J.; Sun, Y.; Zhang, Q. Crystal Transformation of Sericite during Fluidized Roasting: A Study Combining Experiment and Simulation. Minerals 2022, 12, 1223. https://doi.org/10.3390/min12101223

AMA Style

Bai Z, Han Y, Jin J, Sun Y, Zhang Q. Crystal Transformation of Sericite during Fluidized Roasting: A Study Combining Experiment and Simulation. Minerals. 2022; 12(10):1223. https://doi.org/10.3390/min12101223

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Bai, Zhe, Yuexin Han, Jianping Jin, Yongsheng Sun, and Qi Zhang. 2022. "Crystal Transformation of Sericite during Fluidized Roasting: A Study Combining Experiment and Simulation" Minerals 12, no. 10: 1223. https://doi.org/10.3390/min12101223

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