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https://doi.org/10.1016/j.tca.2012.12.025

1

Application of TG-FTIR to study SO2 evolved during the thermal

decomposition of coal-derived pyrite

Hongfei Cheng a,b, Qinfu Liu a*, Man Huang a, Shilong Zhang a, Ray L. Frost b

a School of Geoscience and Surveying Engineering, China University of Mining & Technology, Beijing,

100083 P.R. China

b School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty,

Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001,

Australia

Abstract

The thermal decomposition of the coal-derived pyrite was studied using

thermogravimetry combining with Fourier-transform infrared spectroscopy (TG-FTIR)

techniques to gain knowledge on the SO2 gas evolution process and formation

mechanism during the thermal decomposition of the coal-derived pyrite. The results

showed that the thermal decomposition of the coal-derived pyrite which started at

about 400 °C was complete at 600 °C; the gas evolved can be established by

combining the DTG peak, the Gram-Schmidt curve and in situ FTIR spectroscopic

evolved gas analysis. It can be observed from the spectra that the pyrolysis products

for the sample mainly vary in quantity, but not in species. It was proposed that the

oxidation of the coal-derived pyrite started at about 400 °C and that pyrrhotite and

hematite were formed as primary products. The SO2 released by the thermal

decomposition of the coal-derived pyrite mainly occurred in the first pyrolysis stage

between 410 and 470 °C with the maximum rate at 444 °C. Furthermore, the SO2 gas

evolution and formation mechanism during the thermal decomposition of the

coal-derived pyrite has been proposed.

Keywords Coal-derived pyrite; thermal decomposition; gas evolution; TG-FTIR Corresponding authors. Fax:+86 10 62331825 (Q. Liu) , +61 7 3138 2407(R. L. Frost)

E-mail addresses: lqf@cumtb.edu.cn (Q. Liu), r.frost@qut.edu.au (R. L. Frost)

2

1. Introduction 1

Pyrite, with chemical formula FeS2, is a very common sulfide mineral and is found in a 2

wide range of geological sites [1]. In countries such as China, pyrite is very abundant and 3

dominant sulfide compound in coal. Although it is only composed of a relatively small 4

portion of coal, it almost influences and decides the operational, environmental and 5

economical performance of handling and utilizing processes of coal [2, 3]. Information about 6

the abundance, distribution and origin of sulfur in coals is important in coal combustion 7

because the sulfur oxides released can be a major source of acid rain [4]. This is also because 8

pyrite releases a major source of SO2 (acid rain precursor) in the combustion process and 9

many evidences also suggest that it may possibly possess a catalytic role in coal liquefaction 10

and gasification processes. Not only does pyrite present itself in many different environments, 11

it exhibits surface chemistry that can profoundly affect the very environment in which it is 12

present. It might be one of the most striking examples of how the reactivity of pyrite can 13

affect an environment is associated with anthropogenic activities. It is reported that the 14

thermal decomposition of pyrite in coal mining sites leads to the devastating environmental 15

problem [5]. Furthermore, pyritic and organic sulfur are the two major forms of sulfur in coal. 16

Their behavior is very important in coal utilization [6]. The thermal stability of coal-derived 17

pyrite (and other sulfides) plays a large role in the commercially important processes of 18

mineral benefaction and the separation of sulfides from coal the evolution process of SO2. 19

Thermogravimetric analysis is used widely in thermal analysis and kinetics parameters 20

study of pyrite under both nitrogen and air atmospheres [1, 7-10]. For decomposition, 21

different heating rates are carried out to obtain the kinetic model [11-13]. For oxidation, 22

different oxygen concentrations and heating rates are taken into account by thermogravimetry 23

(TG) analysis [12, 14]. But the composition of evolved gas in each mass loss steps cannot be 24

observed only by TG. On the other hand, Fourier transform infrared spectroscopy (FTIR) 25

results can be used to evaluate the functional groups and prove the existence of some 26

emissions [15-17]. However, TG combining with FTIR is a useful tool in dynamic analysis as 27

it monitors continuously both the time dependent evolution of the gases and the mass of the 28

non-volatile minerals/materials. It has already been used widely to investigate the thermal 29

3

behavior of minerals [18-24] and polymers thermal degradation [25-27], as well as to forecast 30

the hazardous emissions that may be produced in the case of major accidents [28, 29]. But 31

very limited studies were conducted using TG combining with FTIR on the thermal analysis 32

of coal-derived pyrite. 33

In current study, to the best of the authors’ knowledge no TG-FTIR analysis of 34

coal-derived pyrite has been undertaken; although differential thermal decomposition analysis 35

of pyrite have been published [3, 10, 12, 30]. To forward the understanding on the SO2 gas 36

evolution and formation mechanism during the thermal decomposition of coal-derived pyrite, 37

the thermal behavior of coal-derived pyrite was investigated by the TG combining with FTIR. 38

39

2. Experimental methods 40

2.1. Materials 41

The coal-derived pyrite sample used in the present investigation was extracted from the 42

Qinshui coalfield, Shanxi province of China. The initial sample of the coal-derived pyrite with 43

particle size 0.1-0.2 mm was first subjected to gravity separation to remove the inclusions of 44

coal using a laboratory mechanical pan (Micropaner). Then, the obtained concentrate was 45

cleaned by means of magnetic separation. The purity of the final product was estimated by 46

X-ray diffraction (XRD). The XRD pattern for the coal-derived pyrite is presented in Fig. 1. 47

48

2.2. Characterization 49

2.2.1. X-ray diffraction (XRD) 50

The XRD pattern of the prepared sample was performed using a Rigaku D/max 2500 PC 51

X-ray diffractometer with Cu (λ=1.54178 Å) irradiation at the scanning rate of 2 °/min in the 52

2θ range of 2.6-70 °, operating at 40 kV and 150 mA. 53

2.2.2. TG-FTIR instrumentation 54

Mettler-Toledo TG-DSC I/1600 HT simultaneous thermal analyzer, coupled with 55

Thermofisher Nicolet 6700 FTIR using a Teflon tube, was used to study the pyrolysis 56

behavior. The experiments were done on the thermo-balance at a linear heating rate of 5 °C 57

4

/min within the temperature range from the room temperature (30 °C) to 1200 °C, at a steady 58

air flow. A description of the instrumentation and principles of the experiment have been 59

published elsewhere [25, 31, 32]. The spectrum scope was located in the range of 400-4000 60

cm-1 and the resolution factor was selected to be 1 cm-1. In order to reduce the influence of 61

sample amount on the intensity of infrared absorption, the mass for the sample was set at (2562

±0.05) mg. 63

64

3. Results and discussion 65

3.1. X-ray diffraction (XRD) 66

The XRD pattern of the sample together with standard XRD patterns is shown in Fig. 1, 67

which indicates that the sample contains mainly pyrite with minor amounts of kaolinite and 68

quartz. According to the quantitative XRD analysis, the mineral composition of the sample is 69

shown in table 1. Compared with the standard JCPDS cards, the XRD pattern for the 70

coal-derived pyrite show peak intensity at 2θ=28.51, 33.08, 37.11, 40.78, 47.41, 50.49, 56.28 71

which suggest a very high degree of purity according to the JCPDS file [3]. It is also observed 72

from the XRD pattern that a typical layer structure with a basal spacing (d001) of 0.71 nm. 73

This value matches well with the standard ICDD reference pattern 14-0164 (kaolinite, 74

Al2Si2O5(OH)4). 75

Pyrite has a cubic structure with lattice constant a=5.419 Å, which is consistent with the 76

previous literature [33]. Its space group is Pa3 with crystal cell molecules Z=4. The crystalline 77

size of the sample is about 20 nm, which is calculated from the XRD peaks using the 78

Scherrer’s formula. 79

80

3.2. Thermal analysis 81

To investigate the thermal behavior of the coal-derived pyrite, the thermogravimetry and 82

derivate thermogravimetric (TG-DTG) analyses of the sample is presented in Fig. 2, which 83

shows the TG-DTG curves for the sample. The thermal decomposition of the coal-derived 84

pyrite is discussed in details as followed. There are six main mass losses in TG curve of this 85

5

sample. The first mass loss of 2.77 % is observed at below 100 °C. This mass loss is attributed 86

to be the elimination of adsorbed water molecules on the external surfaces of the sample. The 87

second mass loss is observed at 124 °C with a mass loss of 3.02 %, which is assigned to the 88

loss of interparticle water for the sample. The third mass loss of 4.0 % between 200 and 89

300 °C is assigned to the evolution of sulfur on the pyrite surface. It is reported that the 90

existence of elemental sulfur at pyrite surface have also been confirmed by other authors 91

using Raman spectroscopy and X-ray photoeletron spectroscopy analysis [3]. The three mass 92

losses for the sample, which correspond to mass losses of 8.92 % (430-460 °C), 5.21 % 93

(460-515 °C) and 8.42 % (520-590 °C), are assigned to the thermal reaction process for the 94

coal-derived pyrite. The process can be represented by the following reaction: 95

222 SOFeSOFeS (1) 96

SFeSFeS 2 (2) 97

22 SOOS (3) 98

2322 22

72 SOOFeOFeS (4) 99

According to the report by Hong and Fegley [34], no hematite (Fe2O3) but only 100

pyrrhotite was observed within the temperature range of 400-520 °C. It is reported that sulfur 101

appears in the pyrrhotite produced at a lower temperature (440-500 °C) [35]. Pulik et al. [7] 102

found that the reaction (2) should be considered in thermal decomposition process without 103

oxygen for the inner portion of pyrite particles. Therefore, it is concluded that the mass loss at 104

400-480 °C is caused by the oxidation of the sample particle surface and the decomposition of 105

the interior for the pyrite particle without oxygen, in accordance with Eq. (1) and Eq. (2). The 106

thermal process at 530-570 °C is attributed to the evolution of oxidized sulfur stemmed from 107

the last step the decomposed of the pyrite particle without oxygen, Eq. (3). The last step at 108

563 °C is assigned to the oxidation of the pyrrhotite. It is reported by Jorgensen and Moyle 109

[36] that hematite (Fe2O3) is the solid end product of the reaction in this temperature range. 110

They further concluded that small amounts of pyrrhotite formed as thin layers of intermediate 111

reaction product but in amounts which are small in comparison with the amount of hematite. 112

Thus Eq. (4) is a reasonable candidate for this process. Therefore, the thermal decomposition 113

6

of pyrite which started at 430 °C was completed at 590 °C. It is indicated that the chemical 114

substance SO2 is present in the thermal decomposition for the sample, and this will be further 115

proved by the following IR results. It is observed that the mass loss at 563 °C is higher than 116

that at 495 °C. This is due to the existence of the impurity kaolinite in the sample. The 117

dehydroxylation of kaolinite occurs at this temperature range, with the onset of the 118

transformation to metakaolin. The process can be mostly described by the reaction [37-43]: 119

OHSiOOAlOHOSiAl 22324522 22)( (5) 120

Compared with the decomposition of pure pyrite in nitrogen, the initial decomposition 121

temperature of the coal-derived pyrite is nearly lower by 100 °C [7, 44, 45]. It suggests that 122

the indigenous hydrocarbon with hydrogen donor ability in coal can promote the reduction of 123

pyrite, though the overall deficit of hydrogen makes the thermal decomposition reaction of 124

pyrite to prevail in pyrolysis [2]. Therefore, the thermal decomposition of the coal-derived 125

pyrite is a complex process due to involving several steps of heat and mass transfer. 126

127

3.3. The Gram-Schmidt curve 128

In the present work, the characteristic temperatures such as the temperature at the 129

maximum mass loss rate, the initial and the terminal temperature of each pyrolysis stage are 130

determined by the DTG curve. It is evident that the thermal decomposition for this sample 131

exhibits three main mass losses which start at 410 °C and the maximum rate decomposition 132

temperatures are located at 444, 495, 563 °C, respectively. Fig. 3 shows the evolved gas 133

profile of the coal-derived pyrite. Several representative times in each pyrolysis stage are 134

selected to study the decomposition process of the coal-derived pyrite. Measurable evolution 135

of gas is found to start at about 410 °C and to reach three maximum intensities at 444, 495 136

and 563 °C, respectively. Although pyrite can potentially decompose below 400 °C, the 137

reaction is very slow and no significant gas evolution is observed from the experiments and 138

subsequent Gram-Schmidt curve of this sample. However, as the temperature reaches 444 °C, 139

it can be observed that the appearance of gas evolution followed by appearance of gas 140

evolution at 495 °C. Upon further heating the sample, evolution of gas is observed again at 141

563 °C. Moreover, the gaseous fraction for the thermal decomposition of pyrite is consisted 142

7

chiefly of SO2. This will be further proved by the in situ FTIR spectroscopic evolved gas 143

analysis. Therefore, it is concluded that the thermal decomposition of the coal-derived pyrite 144

which started at about 400 °C was complete at 600 °C; the gas evolved during the thermal 145

decomposition of pyrite can be established by combining the DTG peak, the Gram-Schmidt 146

curve and in situ FTIR spectroscopic evolved gas analysis. As expected, the Gram-Schmidt 147

plot show the presence of three regions of evolved gases, clearly related to the peak of the 148

DTG curve. It is pointed out that the products of decomposition and reaction for pyrite vary 149

depending upon the environment [3, 30]. For instance, it is easily oxidized to different iron 150

oxides such as Fe2O3 or Fe3O4 in the oxidizing environment [12], while pyrrhotite is one of 151

the major products for the thermal decomposition of pyrite in non-oxidative environments 152

[30]. However, as previous reported vary widely, no unanimous conclusion can be drawn. 153

There are two main explanations accounting for the thermal decomposition process for the 154

pyrite. Some researchers suggest that the oxidation of pyrites proceeds primarily through the 155

formation of sulphates [FeSO4, Fe2(SO4)3] which later decompose to ferric oxide (Fe2O3) and 156

sulphur dioxide (SO2). Others hold that the primary products of oxidation are the oxides (FeO, 157

Fe2O3) which subsequently react with sulphur dioxide to produce sulphates [46, 47]. 158

According to the reported by Yan et al. [3], it would be very difficult to figure out the 159

decomposition mechanism of pyrite under real coal thermal condition. In addition, the 160

reaction is more complicated and difficult to study in the presence of coal and only sporadic 161

information can be found in the literature. It is also reported that individual pyrite does not 162

provide the interactions between pyrite and the coal carbon matrix. It is also believed that 163

oxidation of pyrites is accompanied by the thermal decomposition to pyrrhotite. 164

165

3.4. In situ FTIR spectroscopic evolved gas analysis of the coal-derived pyrite as coupled 166

online with TG 167

Fig.4 shows the spectra of gas released out in the first pyrolysis stage, at 410 °C, 444 °C 168

and 470 °C for the thermal decomposition of the coal-derived pyrite, respectively. According 169

to the widely applied Lambert-Beer law, the absorbance at a specific wavenumber is linearly 170

dependent on gas concentration [48]. Thus the variation of absorbance in the whole process 171

can reflect the tendency of product yield of the gas species. The absorption bands of volatile 172

8

for the sample appear to be at the same wavenumbers, while some diversities of the 173

absorbance exist. It can be seen from the spectra that the relative intensity of bands in 174

3964-3500 and 1800-1300 cm-1 region, corresponding to the main presence of water, remains 175

unchanged. This is due to water and a fraction of the carbon dioxide come from the 176

atmosphere. The other fraction of CO2 is released by the pyrolysis of the residual coal. It is 177

also observed that the relative intensity of CO2 increase as temperature goes up. The 178

formation of SO2 is evidenced by the strong bands at 1450-1300 cm-1 and 1150 cm-1. It is 179

found that the relative intensity of SO2 increases with the increasing of temperature, and 180

reaches a maximum at 444 °C and then decreases. When the thermal decomposition of the 181

coal-derived pyrite into the primary stage, more gaseous products are released out. After 182

analysis, a conclusion can be drawn that the mass loss in this stage is mainly caused by the 183

release of SO2, with the unique existence of characteristic bands at 1450-1300 cm-1 and 1150 184

cm-1. Therefore, it can be concluded that the SO2 released in the temperature range of 185

410-470 °C is caused by the oxidation of the surface of the coal-derived pyrite particle, in 186

accordance with Eq. (1). When the temperature increased up to 444 °C, the total amount of 187

the evolved gas SO2 begin to drop off. 188

Fig. 5 shows the spectra for the thermal decomposition of the coal-derived pyrite at 470, 189

495 and 515 °C. The absorption bands of volatile for the sample also appear to be at the same 190

wavenumbers, while the diversities of the absorbance only exist in 1450-1300 cm-1 region. 191

The release of water and CO2 (bands at 3964-3500 and 1800-1300 cm-1 region) is less violent, 192

while the relative intensity of SO2 firstly increases and then decreases. As mentioned earlier, it 193

should be considered the occurrence of reaction (1) in the presence of oxygen atmosphere 194

whereas the reaction (2) must be taken into account in an oxygen-free atmosphere. It is quite 195

conceivable that the reactions (1) and (2) occur simultaneously (410-470 °C) while the 196

reaction (3) follows the earlier ones. Therefore, the thermal process at 470-515 °C is 197

attributed to the evolution of oxidized sulfur stemmed from the last step the decomposed of 198

the pyrite particle without oxygen. 199

The spectra for the thermal decomposition of the coal-derived pyrite at 515, 563, 575, 200

590 and 630 °C are shown in Fig. 6. As the temperature of the system is raised, an amount of 201

SO2 is released in the temperature range of 515-630 °C by the thermal decomposition of the 202

9

coal-derived pyrite. It indicates the reaction occurs in wide temperature range. It is reported 203

that pyrrhotite is an intermediate phase produced during heating of pyrite [30]. The 204

researchers further proposed that hematite is the major reaction product during heating pyrite 205

in a restrictive oxidative environment. Thus Eq. (4) is a reasonable candidate for this process. 206

At the same time, the water and carbon dioxide are still detected by the in situ FTIR 207

spectroscopic evolved gas analysis. It is also observed that the intensities of the CO2 and the 208

water are nearly unchanged in these five spectra when the temperature increases from 515 to 209

630 °C. Therefore, it has once again proved that water and a fraction of the carbon dioxide 210

come from the atmosphere. 211

As proposed by Srinivasachar et al. [49, 50] and Hu et al.[12], in the case of incomplete 212

combustion, pyrite will initially decompose to form pyrrhotite (FeSx), which subsequently 213

melts to form iron oxysulfide droplets, from which magnetite (Fe3O4) crystallizes out to 214

finally form hematite (Fe2O3). It is proposed that the O2 molecule is able to accelerate the 215

decomposition by penetrating the surface layer, react with one of the sulfur atoms at the pyrite 216

core, and diffuse out of the surface layer again as SO2. From the results presented in this 217

investigation, and the available evidence pointing towards the thermal decomposition of 218

pyrite [12, 30, 46], we concluded that the possible mechanism for SO2 evolved during the 219

thermal decomposition of the pyrite is shown in Fig. 7. 220

221

4. Conclusions 222

The thermal decomposition of the coal-derived pyrite is studied using TG-FTIR 223

techniques. The thermal decomposition of the coal-derived pyrite which started at 224

approximately 400 °C is complete at 600 °C; the gas evolved during the thermal 225

decomposition of the sample can be established by combining the DTG curve, the 226

Gram-Schmidt curve and in situ FTIR spectroscopic evolved gas analysis. It can be observed 227

from the spectra that the pyrolysis products mainly vary in quantity, but not in species. It is 228

concluded that the oxidation of the coal-derived pyrite starts at about 400 °C and that 229

pyrrhotite and hematite are formed as primary products. The SO2 released by the thermal 230

decomposition of the coal-derived pyrite is preceded in the three stages: 410-470 °C, 231

10

470-515 °C and 515-630 °C. Large amounts of SO2 gas evolution mainly occurs in the first 232

pyrolysis stage between 410 and 470 °C with the maximum rate at 444 °C. 233

TG coupled with spectroscopic gas analysis is demonstrated to be a powerful tool for the 234

investigation of gas evolution from the thermal decomposition of materials. It delivers a 235

detailed insight into the thermal behavior of the materials characterized by the in situ FTIR 236

spectroscopic evolved gas analysis. The online coupling ensures not only the determination of 237

pyrolysis gases but also the release relative intensity during the decomposition. Therefore, 238

using different gas analyzing methods like MS and FTIR increases the unambiguous 239

interpretation of the results. 240

241

Acknowledgments 242

The authors gratefully acknowledge the financial support provided by the National Natural Science 243

Foundation of China (No. 51034006) and China Postdoctoral Science Foundation funded project 244

(No.2011M500034 and No.2012T50160). 245

11

References

[1] H. Hu, Q. Chen, Z. Yin, P. Zhang, Thermal behaviors of mechanically activated pyrites by

thermogravimetry (TG), Thermochim. Acta, 398 (2003) 233-240.

[2] H. Chen, B. Li, B. Zhang, Decomposition of pyrite and the interaction of pyrite with coal organic

matrix in pyrolysis and hydropyrolysis, Fuel, 79 (2000) 1627-1631.

[3] J. Yan, L. Xu, J. Yang, A study on the thermal decomposition of coal-derived pyrite, J. Anal. Appl.

Pyrol., 82 (2008) 229-234.

[4] S. Dai, D. Ren, Y. Tang, L. Shao, S. Li, Distribution, isotopic variation and origin of sulfur in coals

in the Wuda coalfield, Inner Mongolia, China, Int. J. Coal Geol., 51 (2002) 237-250.

[5] R. Murphy, D.R. Strongin, Surface reactivity of pyrite and related sulfides, Surf. Sci. Rep., 64 (2009)

1-45.

[6] G. Gryglewicz, P. Wilk, J. Yperman, D.V. Franco, I.I. Maes, J. Mullens, L.C. Van Poucke,

Interaction of the organic matrix with pyrite during pyrolysis of a high-sulfur bituminous coal,

Fuel, 75 (1996) 1499-1504.

[7] F. Paulik, J. Paulik, M. Arnold, Kinetics and mechanism of the decomposition of pyrite under

conventional and quasi-isothermal---quasi-isobaric thermoanalytical conditions, J. Therm. Anal.

Calorim., 25 (1982) 313-325.

[8] J. Paulik, F. Paulik, M. Arnold, Simultaneous TG, DTG, DTA and EGA technique for the

determination of carbonate, sulphate, pyrite and organic material in minerals, soils and rocks, J.

Therm. Anal. Calorim., 25 (1982) 327-340.

[9] A.B. Corradi, C. Leonelli, T. Manfredini, L. Pennisi, M. Romagnoli, Quantitative determination of

pyrite in, ceramic clay raw materials by DTA, Thermochim. Acta, 287 (1996) 101-109.

[10] N. Boyabat, A.K. Özer, S. Bayrakçeken, M.S. Gülaboglu, Thermal decomposition of pyrite in the

nitrogen atmosphere, Fuel Process. Technol., 85 (2004) 179-188.

[11] B. Ouertani, J. Ouerfelli, M. Saadoun, B. Bessaïs, M. Hajji, M. Kanzari, H. Ezzaouia, N.

Hamdadou, J.C. Bernède, Transformation of amorphous iron oxide films pre-deposited by spray

pyrolysis into FeS2-pyrite films, Mater. Lett., 59 (2005) 734-739.

[12] G. Hu, K. Dam-Johansen, S. Wedel, J.P. Hansen, Decomposition and oxidation of pyrite, Prog.

Energ. Combust, 32 (2006) 295-314.

[13] C.D. Barrie, A.P. Boyle, N.J. Cook, D.J. Prior, Pyrite deformation textures in the massive sulfide

ore deposits of the Norwegian Caledonides, Tectonophysics, 483 (2010) 269-286.

[14] P.R. Norris, C.S. Davis-Belmar, J.L.C. Nicolle, L.A. Calvo-Bado, V. Angelatou, Pyrite oxidation

and copper sulfide ore leaching by halotolerant, thermotolerant bacteria, Hydrometallurgy, 104

(2010) 432-436.

[15] H. Cheng, J. Yang, Q. Liu, J. Zhang, R.L. Frost, A spectroscopic comparison of selected Chinese

kaolinite, coal bearing kaolinite and halloysite--A mid-infrared and near-infrared study,

Spectrochim. Acta A: Mol. Biomol. Spectrosc., 77 (2010) 856-861.

[16] H. Cheng, R.L. Frost, J. Yang, Q. Liu, J. He, Infrared and infrared emission spectroscopic study of

typical Chinese kaolinite and halloysite, Spectrochim. Acta A: Mol. Biomol. Spectrosc., 77 (2010)

1014-1020.

[17] H. Cheng, J. Yang, R.L. Frost, Z. Wu, Infrared transmission and emission spectroscopic study of

selected Chinese palygorskites, Spectrochim. Acta A: Mol. Biomol. Spectrosc., 83 (2011)

518-524.

12

[18] J.M. Cervantes-Uc, J.I.M. Espinosa, J.V. Cauich-Rodríguez, A. Ávila-Ortega, H. Vázquez-Torres,

A. Marcos-Fernández, J. San Román, TGA/FTIR studies of segmented aliphatic polyurethanes

and their nanocomposites prepared with commercial montmorillonites, Polym. Degrad. Stabil., 94

(2009) 1666-1677.

[19] N. Huang, J. Wang, A TGA-FTIR study on the effect of CaCO3 on the thermal degradation of EBA

copolymer, J. Anal. Appl. Pyrol., 84 (2009) 124-130.

[20] M. Mehring, M. Elsener, O. Kröcher, Development of a TG-FTIR system for investigations with

condensable and corrosive gases, J. Therm. Anal. Calorim., 105 (2011) 545-552.

[21] M. Loría-Bastarrachea, W. Herrera-Kao, J. Cauich-Rodríguez, J. Cervantes-Uc, H.

Vázquez-Torres, A. Ávila-Ortega, A TG/FTIR study on the thermal degradation of poly(vinyl

pyrrolidone), J. Therm. Anal. Calorim., 104 (2011) 737-742.

[22] M. Beneš, N. Milanov, G. Matuschek, A. Kettrup, V. Plaček, V. Balek, Thermal degradation of

PVC cable insulation studied by simultaneous TG-FTIR and TG-EGA methods, J. Therm. Anal.

Calorim., 78 (2004) 621-630.

[23] C. Tănase, L. Odochian, N. Apostolescu, A. Pui, TG–FTIR analysis applied to the study of thermal

behaviour of some edible mushrooms, J. Therm. Anal. Calorim., 103 (2011) 1079-1085.

[24] J. Madarász, M. Krunks, L. Niinistö, G. Pokol, Evolved gas analysis of dichlorobis (thiourea)

zinc(II) by coupled TG-FTIR and TG/DTA-MS techniques, J. Therm. Anal. Calorim., 78 (2004)

679-686.

[25] J.P. Charland, J.A. MacPhee, L. Giroux, J.T. Price, M.A. Khan, Application of TG-FTIR to the

determination of oxygen content of coals, Fuel Process. Technol., 81 (2003) 211-221.

[26] J.A. MacPhee, L. Giroux, J.P. Charland, J.F. Gransden, J.T. Price, Detection of natural oxidation of

coking coal by TG-FTIR—mechanistic implications, Fuel, 83 (2004) 1855-1860.

[27] B. Bowley, E.J. Hutchinson, P. Gu, M. Zhang, W.-P. Pan, C. Nguyen, The determination of the

composition of polymeric composites using TG-FTIR, Thermochim. Acta, 200 (1992) 309-315.

[28] H.M. Zhu, J.H. Yan, X.G. Jiang, Y.E. Lai, K.F. Cen, Study on pyrolysis of typical medical waste

materials by using TG-FTIR analysis, J. Hazard. Mater., 153 (2008) 670-676.

[29] G. Reggers, M. Ruysen, R. Carleer, J. Mullens, TG-GC-MS, TG-MS and TG-FTIR applications on

polymers and waste products, Thermochim. Acta, 295 (1997) 107-117.

[30] S.K. Bhargava, A. Garg, N.D. Subasinghe, In situ high-temperature phase transformation studies

on pyrite, Fuel, 88 (2009) 988-993.

[31] L. Tao, G.-B. Zhao, J. Qian, Y.-k. Qin, TG–FTIR characterization of pyrolysis of waste mixtures of

paint and tar slag, J. Hazard. Mater., 175 (2010) 754-761.

[32] Q. Liu, Z. Zhong, S. Wang, Z. Luo, Interactions of biomass components during pyrolysis: A

TG-FTIR study, J. Anal. Appl. Pyrol., 90 (2011) 213-218.

[33] X.F. Qian, X.M. Zhang, C. Wang, K.B. Tang, Y. Xie, Y.T. Qian, Solvent-thermal preparation of

nanocrystalline pyrite cobalt disulfide, J. Alloy. Compd., 278 (1998) 110-112.

[34] Y. Hong, B. Fegley, The kinetics and mechanism of pyrite thermal decomposition, Ber. Buns-Ges.

Phys. Chem., 101 (1997) 1870-1881.

[35] Z.D. Zivkovic, N. Mitevska, V. Savovic, Kinetics and mechanism of the chalcopyrite-pyrite

concentrate oxidation process, Thermochim. Acta, 282-283 (1996) 121-130.

[36] F.R.A. Jorgensen, F.J. Moyle, Gas diffusion during the thermal analysis of pyrite, J. Therm. Anal.

Calorim., 31 (1986) 145-156.

[37] O. Castelein, B. Soulestin, J.P. Bonnet, P. Blanchart, The influence of heating rate on the thermal

13

behaviour and mullite formation from a kaolin raw material, Ceram. Int., 27 (2001) 517-522.

[38] Y.-F. Chen, M.-C. Wang, M.-H. Hon, Phase transformation and growth of mullite in kaolin

ceramics, J. Eur. Ceram. Soc., 24 (2004) 2389-2397.

[39] R.L. Frost, H. Erzsébet, M. Éva, K. János, R. Ákos, Slow transformation of mechanically

dehydroxylated kaolinite to kaolinite--an aged mechanochemically activated

formamide-intercalated kaolinite study, Thermochim. Acta, 408 (2003) 103-113.

[40] K. Heide, M. Foldvari, High temperature mass spectrometric gas-release studies of kaolinite

Al2[Si2O5(OH)4] decomposition, Thermochim. Acta, 446 (2006) 106-112.

[41] C.Y. Chen, G.S. Lan, W.H. Tuan, Microstructural evolution of mullite during the sintering of

kaolin powder compacts, Ceram. Int., 26 (2000) 715-720.

[42] S.J. Chipera, D.L. Bish, Thermal evolution of fluorine from smectite and kaolinite, Clays and Clay

Minerals, 50 (2002) 38-46.

[43] V. Balek, M. Murat, The emanation thermal analysis of kaolinite clay minerals, Thermochim. Acta,

282-283 (1996) 385-397.

[44] V.G. Shkodin, D.N. Abishev, A.K. Kobzhasov, V.P. Malyshev, R.F. Mangutova, The question of

thermal decomposition of pyrite, J. Therm. Anal. Calorim., 13 (1978) 49-53.

[45] P. Thomas, D. Hirschausen, R. White, J. Guerbois, A. Ray, Characterisation of the oxidation

products of pyrite by Thermogravimetric and Evolved Gas analysis, J. Therm. Anal. Calorim., 72

(2003) 769-776.

[46] J.P. Hansen, L.S. Jensen, S. Wedel, K. Dam-Johansen, Decomposition and oxidation of pyrite in a

fixed-bed reactor, Ind. Eng. Chem. Res., 42 (2003) 4290-4295.

[47] I.I. Maes, J. Yperman, H. Van den Rul, D.V. Franco, J. Mullens, L.C. Van Poucke, G. Gryglewicz,

P. Wilk, Study of Coal-Derived Pyrite and Its Conversion Products Using Atmospheric Pressure

Temperature-Programmed Reduction (AP-TPR), Energ. Fuel, 9 (1995) 950-955.

[48] Q. Liu, S. Wang, Y. Zheng, Z. Luo, K. Cen, Mechanism study of wood lignin pyrolysis by using

TG–FTIR analysis, J. Anal. Appl. Pyrol., 82 (2008) 170-177.

[49] S. Srinivasachar, J.J. Helble, A.A. Boni, N. Shah, G.P. Huffman, F.E. Huggins, Mineral behavior

during coal combustion 2. Illite transformations, Prog. Energ. Combust, 16 (1990) 293-302.

[50] S. Srinivasachar, J.J. Helble, A.A. Boni, Mineral behavior during coal combustion 1. Pyrite

transformations, Prog. Energ. Combust, 16 (1990) 281-292.

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LIST OF TABLES

Table 1 The minerals composition of coal-derived pyrite used in this experiment

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Table 1 The minerals composition of coal-derived pyrite used in this experiment

Sample Content of minerals (%)

Pyrite Quartz Kaolinite

Pyrite 85.9 3 13.8

16

LIST OF FIGURES

Fig.1 XRD pattern of the coal-derived pyrite

Fig.2 TG-DTG curves for the coal-derived pyrite Fig.3 The Gram-Schmidt curve of the coal-derived pyrite Fig.4 FT-IR spectra of gas released out at 410, 444 and 470 °C Fig.5 FT-IR spectra of gas released out at 470, 495 and 515 °C Fig.6 FT-IR spectra of gas released out at 515, 563, 575, 590 and 630 °C Fig.7 Mechanistic suggestion for the SO2 released by the thermal decomposition of pyrite

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Fig.1

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Fig.2

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Fig.3

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Fig.4

21

Fig.5

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Fig.6

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Fig.7