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Liu, Haibo, Chen, Tianhu, Zou, Xuehua, Qing, Chengsong, & Frost, Ray(2013)Thermal treatment of natural goethite: Thermal transformation and physi-cal properties.Thermochimica Acta, 568, pp. 115-121.
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https://doi.org/10.1016/j.tca.2013.06.027
1
Thermal treatment of natural goethite: thermal transformation and 1
physical properties 2
Haibo Liua,b, Tianhu Chena,, Xuehua Zoua, Chengsong Qinga, Ray L. Frost b 3
4
aLaboratory for Nanomineralogy and Environmental Material, School of Resources & 5
Environmental Engineering, Hefei University of Technology, China 6
7 bSchool of Chemistry, Physics and Mechanical Engineering, Science and Engineering 8
Faculty, Queensland University of Technology, Australia 9
10
Abstract: XRD （X-ray diffraction）, XRF (X-ray fluorescence), TG (Thermogravimetry), 11
FT-IES (Fourier transform infrared emission spectroscopy), FESEM (Field emission 12
scanning electron microscope), TEM (Transmission electron microscope) and nitrogen-13
adsorption-desorption analysis were used to characterize the composition and thermal 14
evolution of the structure of natural goethite. The in-situ FT-IES demonstrated the start 15
temperature (250 oC) of the transformation of natural goethite to hematite and the 16
thermodynamic stability of protohematite between 250 and 600 oC. The heated products 17
showed a topotactic relationship to the original mineral based on SEM analysis. Finally, the 18
nitrogen-adsorption-desorption isotherm provided the variation of surface area and pore size 19
distribution as a function of temperature. The surface area displayed a remarkable increase 20
up to 350 oC, and then decreased above this temperature. The significant increase in surface 21
area was attributed to the formation of regularly arranged slit-shaped micropores running 22
parallel to elongated direction of hematite microcrystal. The main pore size varied from 0.99 23
nm to 3.5 nm when heating temperature increases from 300 to 400 oC. The hematite derived 24
from heating goethite possesses high surface area and favors the possible application of 25
hematite as an adsorbent as well as catalyst carrier. 26
Keywords: Goethite, Thermogravimetry, Hematite, Specific surface area, topotactic 27
relationship 28
Corresponding author. Tel.: +86 13956099615, +86 0551 2903990. E-mail address: [email protected]; [email protected] Author to whom correspondence should be addressed ([email protected]) P +61 7 3138 2407 F: +61 7 3138 1804
2
29
1. Introduction 30
Goethite, -FeOOH, is widely distributed, occurs in rocks, soils and throughout the 31
global ecosystem, and has the diaspore structure which is based on hexagonal close packing 32
[1]. Generally, goethite is an oxidation, decomposition, weathering and hydrolyzation 33
product of pyrite, siderite, magnetite and Fe-containing silicates [1]. Although goethite 34
displays a range of shapes and sizes, the most basic morphology is acicular with the length 35
varying from tens of nanometer to several microns. Goethite is one of the most abundant and 36
thermodynamically stable Fe-containing crystalline compounds, therefore, goethite is the 37
first oxide to form or is the end member of many transformations [1-3] in which the 38
transformation of goethite to hematite generally occurs after heating between 180 and 300 oC 39
[4, 5]. 40
In past decades, many studies have been carried out to investigate the adsorption 41
capability of hematite for organic molecules including protein [6], methanol [7], C4-42
dicarboxylic (maleic, fumaric, and succinic acids) [8] and inorganic compounds contaniing 43
heavy metals [9-13], metalloids [14-16], and radionuclides [17-19]. A number of studies 44
have reported [20, 21] that ferric oxide surfaces are hydrated upon exposure to water. The 45
report of Jones et al. [22] shows that the most stable of the hydrated plane of hematite is the 46
O-terminated plane, however, the extremely unstable plane is the Fe-terminated plane in the 47
presence of excess water (>=67% coverage). As for organic compounds, more attention is 48
paid to the adsorption between natural waters and soils. Ishikawa et al. [7] investigated the 49
adsorption of CH3OH, CCl4, C6H6 and C6H5Cl on well-defined slit-shaped hematite. The 50
result indicated that the surface Fe-OH groups function as the adsorption sites. As for 51
inorganic compounds, both synthetic and natural hematite surfaces have been studied in 52
detail with respect to adsorption of contaminants [7]. It has been reported that iron-oxide-53
coated sand was utilized as a filling material for a fixed bed configuration for simultaneous 54
filtration of particular matter and adsorption of dissolved metals [9]. These space-filling 55
materials displayed great adsorption ability in removing uncomplexed and ammonia-56
complexed cationic metals (Cu, Cd, Pb, Ni, Zn), as well as some oxyanionic metalloid 57
(SeO32-, AsO3
-). Commercially prepared hematite nanoparticles have been employed for 58
adsorption of bivalent metals (Pb, Cu, Zn, Cd) and the results proved that nanohematite 59
could be applicable in water treatment technology for removing metals [23]. Besides, the 60
3
adsorption of hematite to phosphate, arsenic, sulfate and radionuclide (uranium, nickel) has 61
been researched in details [14, 18, 19, 24, 25]. The effect of relative parameters such as 62
temperature, different iron oxides, pH and materials preparation methods on adsorption of 63
contaminants also has been reported in previous reports [10-13, 15-17, 23, 26]. Furthermore, 64
as is well-known, nanomaterials possess some advantages over their bulk counterparts, such 65
as an increased specific surface area and high reactivity, which makes them more effective 66
and feasible for engineering application. Thereby, Zhang et al. [27] and Zeng et al. [28] 67
investigated the effect of nanoscale size on the adsorption ability of hematite. A natural 68
goethite was used as a catalysts carrier supporting nickel catalytic cracking of biomass tar 69
and displays a good catalytic reactivity [29]. 70
As mentioned above, goethite distributes widely and generally displays acicular 71
morphology with the length varying from tens of nanometer to several microns. It has been 72
demonstrated hematite could be used in water treatment as well being used as a catalyst 73
carrier. Nanohematite possesses more advantages in adsorption ability. Therefore, in this 74
present study, thermal treatment of natural goethite is carried out and physical properties of 75
thermally treated natural goethite (hematite) is investigated using modern analytical 76
techniques, such as FESEM, XRD, specific surface area and pore distribution analyzer, etc. 77
The objective is to characterize the natural goethite before and after thermal treatment, to 78
investigate the physical properties of hematite derived from goethite and to find a kind of 79
low cost material for possible application in water treatment and catalysis. 80
1. Experimental 81
2.1 Materials 82
Natural goethite (-FeOOH) was collected from Tongling city, Anhui province, China. 83
The natural goethite was crushed and sieved into a desired particle size. The obtained 84
goethite particles were annealed at different temperature for 2h (100, 150, 200, 250, 300, 350, 85
400, 500, 600, 700, 800 oC) and retained for further characterization. The goethite labeled as 86
G25 and the heated goethite labeled as G100, where G denotes goethite and the number 87
denotes the thermal treatment temperature. 88
2.2 Characterizations 89
X-ray diffraction (XRD) patterns were recorded using Cu Kα radiation (λ = 1.5406 Å) 90
on a Philips PANalytical XPert Pro muti purpose diffractometer. The tube voltage was 40kV 91
4
and the current, 40mA. All XRD diffraction patterns were taken in the range of 15-75o at a 92
scan speed of 2o min−1 with 0.5o divergence slit size. Phase identification was carried out by 93
comparison with those included in the Inorganic Crystal Structure Database (ICSD). 94
Chemical composition was measured on an X-ray fluorescence (XRF) spectrometer 95
(Shimadzu XRF-1800) with Rh radiation. 96
Thermogravimetry (TG) was measured on TA instruments thermogravimetric analyser 97
(TGA, Q500). High-purity nitrogen was used as purging gas with a flowing rate for balance 98
(40 mL/min) and a flowing rate for sample (60 mL/min). The natural goethite was loaded 99
onto platinum sample pan and heated to 1000 oC at a high resolution heating rate of 6 oC/min, 100
where the heating rate was dynamically and continuously modified in response to the 101
changes in the rate of sample’s mass loss, termed as controlled rate thermal analysis (CRTA). 102
Fourier transform infrared emission spectroscopy (FT-IES) was carried out on a Nicolet 103
spectrometer equipped with a TGS detector, which was modified by replacing the IR source 104
with an emission cell. A thin layer (approximately 0.2 microns) on a platinum surface with 6 105
mm diameter and held in an inert atmosphere within a nitrogen-purged cell during heating. 106
The spectra was acquired by co-addition of 1024 scans at the temperature of 150, 200, 512 107
scans at 250, 256 scans at 300, 350, and 128 scans at temperature from 400 to 800 oC. 108
109
Transmission electron microscope (TEM) measurements were performed on JEM-1010. 110
The samples were mixed with alcohol and deposited on a Cu grid. Images of the 111
microstructure were acquired using an analytical electron microscope. 112
113
Field emission scanning electron microscope (FESEM) measurements were performed 114
on JEOL JSM-7001F with an energy dispersive x-ray detector. All samples were coated gold 115
by spraying before analysis. 116
13-point BET-nitrogen isotherms were used to quantify changes in the specific surface 117
area. All samples were degassed at 110 oC for 12 h before analysis were conducted. The 118
multi-point BET surface area of each sample was measured at atmospheric pressure using 119
TriStar Ⅱ 3020 Surface Area and Pore Size Analyzer. The adsorption isotherms achieved a 120
p/po range of 0.009-0.25. Pore size distribution was evaluated by BJH desorption pore 121
distribution report between 1.7 nm and 20 nm. 122
5
123
2. Results and discussion 124
3.1 XRD and XRF 125
Fig. 1 displays the XRD patterns of goethite and thermally treated goethite at different 126
temperatures. These peaks are observed in the XRD pattern of G25 and identified as goethite 127
when compared with the standard pattern (ICSD (96-900-2159)). All the peak intensity 128
shows a small decrease with the increasing temperatures, and then disappears as the 129
temperature reaches 300 oC and the peaks were replaced by several new reflections. The new 130
reflections with low intensity appear after heating at 250 oC and indentified as hematite after 131
comparison with the pattern of ICSD (96-900-0140). It indicates the transformation of 132
goethite to hematite basically occurs below 250 oC with a slow transformation rate. The 133
result is consistent with that reported previously [30, 31]. The characteristic reflection 134
intensity of hematite has a dramatic increase with the increased temperature because of the 135
increase of crystal size and the improvement of crystallinity of newly formed hematite. In 136
addition, the result of XRF analysis show the natural goethite contains Fe2O3 84.8% 137
(FeOOH 94.3 %), SiO2 1.9%, MnO2 0.8%, Al2O3 0.6%, ZnO 0.4%, and ignition loss 12.1 %. 138
It indicates the goethite still includes some impurities, such as quartz and clay which is for 139
natural mineral, or is a kind of (Mn, Al, Zn)-substituted goethite which has been reported for 140
a long time [1, 32]. 141
20 30 40 50 60 70
H HHHHHH
HHH---HematiteG---Goethite
G
G G GGGGG
GG
GG 25oC
200oC
250oC
300oC
350oC
400oC
500oC
600oC
Rel
ativ
e in
ten
sity
/C.p
.s
2 theta/degree
800oC
G
142
6
143
144
3.2 TG and DTG 145
Thermogravimetry (TG) and derivative thermogravimetry (DTG) curves of natural 146
goethite are displayed in Fig. 2. The total mass loss is 12.08% from ambient to 1000 oC 147
temperature, which is different from that of goethite in theory. Four mass loss steps are 148
observed according to the TG curves. Combining with the DTG curve, these mass loss steps 149
should be ascribed to different hydroxyl/water. 150
(1) A mass loss (0.34%) of adsorbed water is observed at ambient temperature, as is 151
indicated by the TG curve. This loss is caused by the purging gas and contributed to the 152
physically adsorbed water just held by van der Waals forces. Liu et al. [2] reported 153
similar results for synthetic goethite. 154
(2) The second mass loss (0.88%) attributed to a second kind of adsorbed water is observed 155
over ambient to 172 oC. This loss results from desorption of adsorbed water bound by 156
hydrogen bonding. The proposed interface stoichiometry ((H2O)-(H2O)-OH2-OH-Fe-O-157
O-Fe-R) for goethite was reported by Ghose et al. [33]. It indicates at least two layers of 158
adsorbed water exists on the surface of goethite. In the present study, the mass loss 159
between ambient to 172 oC temperatures agrees well with the report. 160
(3) The third mass loss (9.37%) occurs between 172 and 310 oC as is readily observed in the 161
DTG curve. The loss is assigned to the dehydroxylation resulting in the transformation of 162
goethite to hematite. This dehydroxylation is attributed to structural hydroxyl units in 163
goethite. This result is in agreement with previously reported results [34, 35]. In addition, 164
two peaks are observed in the DTG curve between 172 and 310 oC which arise from the 165
high crystallinity of natural goethite according to the report of Schwertmann [36]. This 166
report illustrated that low crystallinity leads to a complete transformation to hematite 167
before the change of unit cell size. However, high crystallinity results in the change in 168
7
unit cell size and occurs at a higher temperature. Therefore, the dehydroxylation peak 169
splits into two peaks. 170
(4) The fourth mass loss (1.49%) occurs between 310 and 1000 oC. This loss belongs to the 171
decomposition of remnant structural hydroxyl and partly to nonstoichiometric hydroxyl 172
units. An evidence for the assignment is total mass loss of the third and the fourth steps. 173
The theoretic mass loss of goethite to hematite should be precisely 10.1%. The mass loss 174
of the third step is 9.37%, however, the combined mass loss of the third and the forth 175
step is 10.86%.Thereby, it is speculated that the fourth mass loss step is attributed to the 176
remnant hydroxyl and non-stoichiometric hydroxyl units. Previous studies also gave a 177
further demonstration about the existence of non-stoichiometric hydroxyl units in heated 178
goethite over 300 oC and were explained as the formation of hydrohematite [37-39]. 179
180
0 200 400 600 800
85
90
95
100
12.08%
1.49%
9.37%
0.88%
Temperature/oC
Mas
s L
oss/
%
0.34%
0.0
0.2
0.4
0.6
0.8
310oC172oC
Der
ivat
ive
Mas
s/%
/o C
255oC
279oC
181
Fig. 2. TG and DTG curves of natural goethite 182
183
3.3 FT-IES 184
In order to assess to the structural changes of goethite as a function of treatment 185
temperature, the complimentary technique of infrared emission spectra is utilized. This 186
8
technique takes the infrared spectra of goethite in situ at an elevated temperature. Two 187
changes can reflect the transformation of goethite to hematite. One is the hydroxyl groups 188
deformation in this low wavenumber centered upon 891 and 790 cm-1 and labelled as (OH) 189
and (OH) which are really important diagnostic bands about crystallinity of goethite [40, 190
41]. The other is the high wavenumber belonging to a combination of hydroxyl groups and 191
water molecular stretching vibration. A remarkable decrease occurs in the low wavenumber 192
and high wavenumber when the temperature increases to 250 oC as is displayed in Fig. 3. 193
The decrease is contributed to the occurrence of dehydroxylation of goethite and the start of 194
the transformation of goethite to hematite. In addition, the band at 1014 cm-1 is retained till 195
the temperature of 600 oC, and then shifts to the low wavenumber of 966 cm-1 as the 196
temperature reaches 600 oC, meantime, the intensity of the high wavenumber bands almost 197
approaches zero. All that happens at the 600 oC is attributed to the complete dehydroxylation 198
and the restructure of Fe and O resulting to the formation of well crystallized hematite. It has 199
been reported that the transformation of goethite to hematite goes through a hydrohematite 200
stage [37, 42]. Therefore, the beginning of the transformation of goethite to hematite takes 201
place at 250 oC and the intermediate product (hydrohematite) retains till to 600 oC for this 202
experimental natural goethite. 203
4000 3500 3000 2500 2000 1500 1000
0.02
0.04
0.06
0.08
0.10
0.12
0.14
966891
790
Em
itta
nce
/a.u
.
Wavenumber/cm-1
150 oC
200 oC
250 oC
300 oC
350 oC
400 oC
500 oC
600 oC
700 oC
800 oC
1014
204
Fig. 3. In situ infrared emission spectra of thermally treated goethite 205
206
3.4 Electron spectroscope analysis 207
9
The morphology of natural goethite and thermally treated goethite at 300, 400, 500, 800 208 oC can be observed by TEM images shown in Fig. 4. Some acicular and virgulate substances 209
as well as aggregation are displayed in Fig. 4 (a, b). As mentioned in the results of XRD and 210
XRF, the natural goethite used in this work still probably contains a handful of clays which 211
is conventional phenomenon for natural mineral Therefore, the acicular and virgulate 212
substances are believed to be goethite and the aggregation is speculated as clay like. All the 213
samples after heating over 250 oC are indentified as hematite according to the results of 214
XRD patterns. It can be clearly observed in Fig. 4 (c) a large number of slit-shaped 215
micropores running parallel to the elongated direction of hematite microcrystal and the size 216
of slit-shaped micropores is practically uniform (below 1 nm). In addition, the surface also 217
becomes smooth corresponding to that reported previously [30, 43]. The two reports showed 218
slit-shaped micropores with a width 0.6 and 0.8 nm were obtained after heating at 250 and 219
300 oC, respectively. Without a doubt, the formation of slit-shaped micropores is ascribed to 220
the dehydroxylation in goethite crystal structure due to transformation of goethite to hematite. 221
In case of the pores size, it is difficult to determine precisely the width of micropores 222
because the pores size formed by dehydroxylation would be broadened further by the effect 223
of electron beams of electron microscopy, which has been demonstrated in the study [44]. 224
However, it does not affect the analysis of pore textures. Fig. 4 (d) and (e) present the TEM 225
image of G400 and its amplification, respectively. It seems the slit-shape shows a little 226
broadening after heating at 400 oC. A mass of spherical mesoporous appear instead of the 227
silt-shaped micropores when the sample is heated at 500 oC as displayed in Fig. 4 (f, g). 228
When the temperature reaches 800 oC, mesoporous are destroyed and replaced by 229
cumularspharolith due to sintering between interparticles. Meanwhile, spherical mesoporous 230
still retain in crystal with larger size in spite of the temperature reaching 800 oC. The reports 231
give the confirmation that some hydroxyl groups cannot be removed in hematite structure 232
untill the thermal treatment temperature exceeds 900 oC and substituted goethite also hinders 233
the dehydroxylation [2, 45-47], which should be taken into consideration to explain the 234
existence of mesoporous at 800 oC. In conclusion, the external appearances of the 235
decomposed samples from G300 to G800 are similar to those of natural goethite. That is to 236
say, this decomposition reaction occurs basically within the microcrystal without 237
considerable changes in crystal size and shape except the variation of pore size. 238
Fig. 5 shows the FESEM images of natural goethite and thermally treated goethite as 239
well as the EDS of natural goethite. A bulk mainly composed of acicular substance is 240
10
observed from the Fig. 5 (a, c). Moreover, these acicular substances also congregate into a 241
stalactitic bulk as seen in Fig. 5(d) corresponding to the morphology reported previously[32, 242
48]. In addition, the EDS displayed in Fig. 5(b) indicates this bulk in Fig. 5(a) mainly 243
contains Fe, O, Si, Zn, Mn, Al consistent with the results of XRF. Thereby, the natural 244
mineral used in this work is goethite and its shape primarily presents acicular appearance. 245
The following images as displayed in Fig. 5(e-p) present the effect of thermal treatment 246
temperature on the appearance of goethite. The images in Fig. 5(e, g, i, f) show no obvious 247
changes take place for the appearance of samples after heating at 200 and 300 oC. In the 248
contrary, slit-shaped micropores are formed in the TEM images due to the high resolution in 249
this technique. Meanwhile, the Fig. 5(f, h) suggest that acicular goethite with nanoscale 250
length occurs in the natural goethite except the several microns length conforming the report 251
[1]. Besides, radial bulk displays another type of appearance of goethite aggregation, 252
however, which is not composed of acicular goethite replaced by grains as is observed in Fig. 253
5(k) and its amplification in Fig. 5(l). It is speculated this grain-shaped goethite is formed by 254
transformation of other Fe-containing oxides [49]. Until thermal temperature up to 600 oC, 255
many pores are observed on the well crystallized goethite as is shown in Fig. 5(m) and its 256
amplification in Fig. 5(n). The pores still retain and meanwhile a quantity of crystallinity is 257
divided into several pieces occurring for the poorly crystallized goethite when the 258
temperature increases to 700 oC as is seen in Fig. 5(o, p). While the natural goethite is heated 259
over 500 oC, the change tendency is consistent with the results of TEM images. Therefore, 260
the used natural goethite bulk presents different shape, such as stalactitic and radial, mainly 261
composed of acicular and granular crystal according to the electron microscope observations. 262
The external appearances of the thermally treated samples resemble those of untreated 263
sample despite experiencing high temperature treatment. The kind of thermal treatment 264
provides so many pores and large surface area which would improve the properties of 265
hematite and favor the adsorption of hematite to contaminants and the utilization as catalyst 266
carrier. 267
11
268
Fig. 4. TEM images of natural goethite (a, b) and thermally treated natural goethite 300 oC 269 (c), 400 oC (d, e), 500 oC (f, g), 800 oC (h, i) 270
271
12
272
Fig. 5. FESEM images of natural goethite (a, b (EDS), c, d) and thermally treated goethite 273 200 oC (e, f), 300 oC (g, h), 400 oC (i, j), 500 oC (k, l), 600 oC (m, n), 700 oC (o, p) 274
275
13
3.5 Surface area and pore size distribution 276
To investigate the specific surface area and confirm the pore size distribution of natural 277
goethite and thermally treated goethite, nitrogen-adsorption-desorption (BET) is carried out 278
for each sample. As shown in Fig. 6, it is clearly observed that the surface area has a 279
dramatic increase from 12.7 to the maximum of 111.6 m2/g when the temperature increases 280
to 350 oC, which is ascribed to the formation of slit-shaped micropores due to the 281
dehydroxylation of goethite, and then substantially decrease to 13.7 m2/g after heating at 800 282
oC, where internal and interparticles sintering occurs. The presence and change of slit-shaped 283
micropores is consistent with the results of TEM images and gives a confirmation for the 284
results of XRD and TG. Furthermore, the results correspond to the pore size distribution of 285
experimental samples as displayed in Fig. 6. These curves (Fig. 6) show the changes of pore 286
size distribution between 1.7-20 nm. The peak at 3.9 nm for the untreated natural goethite 287
should be ascribed to the micropores arising from the interparticles clearance. A peak is 288
apparently exists before 1.7 nm with respect to the change tendency of curves for the four 289
samples after heating at 200, 250, 300 and 350 oC. Thereby, a possible simulated curve is 290
given for these samples. The simulated pore size The evaluated pore size peak should be at 291
0.99 nm after heating at 300 oC, which is not very consistent with the previous report that 0.6 292
and 0.8 nm for thermally treated goethite at 250 and 300 oC [30, 43]. The peak shifts to 3.5 293
nm as the goethite is heated over 400 oC and experiences a gradual decrease with the 294
increasing temperature. These results indicate that slit-shaped micropores resulting from the 295
dehydroxylation of goethite cause the dramatic increase of surface area. These newly formed 296
micropores are coalesced to mesoporous and further to macropores resulting to the increase 297
of pore size and decrease of surface area with an increase of temperature. It is proposed that 298
the surface area would attain the maximum as the temperature up to between 300 and 350 oC 299
in case of the relationship between thermal treatment temperature and surface area. 300
14
0 4 8 12 16 200.00
0.02
0.04
0.06
0.99
G25 G200
G250G300G350
G400
G500
G600
G700
G800
3.9
3.5
Incr
emen
tal p
ore
volu
me/
cm3 /g
Pore size/nmG25 G200 G250 G300 G350 G400 G500 G600 G700 G800
0
30
60
90
120
Sp
ecif
ic s
urf
ace
area
/m2 /g
Samples 301
Fig. 6. Pore size distribution and surface area of natural goethite and thermally treated 302 natural goethite 303
3. Conclusions 304
Composition analysis and SEM images indicate the natural goethite is mainly 305
composed of goethite (over 94%) and the goethite displays different appearances varying 306
from nanoscale to several microns in length. On the whole, this goethite is well crystallized 307
according to the double peak in the curve of DTG. Meantime, the TEM images also provide 308
the information of existence of poorly crystallized goethite due to the sintering of 309
microcrystal in contrast to the appearance of mesoporous and macropores on well 310
crystallized goethite after heating at 800 oC. The TG and BET results shows the 311
dehydroxylation occurs at below 200 oC, however, the phase transformation takes place at 312
250 oC. The intermediate product is proved to be hydrohematite based on the results of FT-313
IES and TG. What is more important, the surface area has a dramatic increase till to 350 oC 314
due to the formation of slit-shaped micropores, which would favor the behavior of 315
adsorption of hematite as well as catalyst carrier. The potential application of the hematite 316
derived from goethite is devised. The thermal treatment temperature between 300 and 350 oC 317
produces the hematite with large surface area and so many micropores which is significant 318
properties for adsorption and catalyst carrier. This kind of thermally treated goethite at least 319
could be utilized as filling material for fixing heavy metal. 320
321
4. Acknowledgement 322
This study was financially supported by the Natural Science Foundation of China (No. 323
41130206, 41072036) and Ph.D. Programs Foundation of Ministry of Education of China 324
15
(No.20110111110003). The authors appreciate the financial and infrastructure support of the 325
School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, 326
Queensland University of Technology, for this research. 327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
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352
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16
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