7. 7
WHAT IS RED MUD ?
Red mud is a toxic iron rich
residue of Industrial process of
Bauxite
Highly Basic pH 10-13
Effects the air,land and water
environment of surrounding
area
At present,77 Million Tones of
red mud is generated annually
worldwide
Contain Gibbsite ,Boehmite,
Goethite, Hematite (α-Fe203),
Anatase and Clay Minerals
8. 8
Red mud contain 10-30% hematite
Hematite is being recovered by ‘RED
MUD’
Hematite in red mud being
transformed into ‘MAGNETITE ’(the
highest gade iron ore) with the help of
Pyrite
Remaining 2-3% Iron used as
‘REFRACTORY’
13. 13
Red mud samples dried at 110 ◦ C for 4 h
before testing
30 g of red mud contain the mole ratio of FeS2
to Fe2 O3 was 1:4 or 1:8 roasted at 600 ◦ C for
30 min under N2 atmosphere.
The thermogravimetric analysis (TG) and
differential thermal analysis (DTA) of the
samples were performed on a thermal
analyzer
14. 14
In Fig. the (a)TG-
(b)DTA curves
showing three
weight-loss stages
in the range of 500–
750 ᵒc
23% of weight-loss
Desulfurization of
pyrite at 280ᵒC
15. 15
The XRD patterns of (a) the
anaerobic decomposed residue of
pyrite at 700 ◦ C; and (b) the co-
roasting product of the above
residue with hematite at 600 ◦ C.
a=mole ratio of 1:1
b=mole ratio of 1:5
c=mole ratio of 1:10
d=mole ratio of 1:20
17. a= from a Alumina plant in Shanxi,China.
b= from a Alumina plant in Henan,China.
17
Product
ion
process
Red
mud
sample
s
Al2O3(
%)
SiO2(%) Fe2O3(
%)
TiO2(%) CaO(%) Na2O(%
)
Sinterin
g
Process
1a
2b
5.51
12.20
4.59
20.37
9.7
8.8
3.81
3.74
42.39
38.00
0.61
5.76
Bayer’s
Process
3a
4b
23.20
22.36
22.09
19.05
13.2
19.4
6.24
5.13
18.40
13.31
5.64
8.24
18. 18
The mixture of hematite and pyrite with
different mole ratios are heated at 500ᵒC for
1h (pyrite decomposes into iron
monosulphide FeS)
When the temprature reaches from 525-
600ᵒC hematite could be transformed into
roasted Magnetite
FeS2 + 4Fe2O3 = 3Fe3O4 + 2S
2S + 12Fe2O3 = 8Fe3O4 + 2SO2
19. 19
a=mole ratio of pyrite to hematite in
red mud is 1:4
b=mole ratio of pyrite to hematite in
red mud is 1:8
Red mud
sample
no.
Pyrite
mixed
with 30g
red mud
Magnetic
part
Mass (g)
Magnetic
part
Fe (%)
Non-
magnetic
part
Mass (g)
Non-
magnetic
part
Fe(%)
1
1
2
3
4
0.55a
0.28b
0.51a
0.74a
1.10a
3.3
2.7
3.0
4.5
6.2
36.4
33.8
35.2
36.9
38.7
24.3
26.2
25.0
22.5
20.0
1.07
2.04
1.19
0.61
1.65
21. 21
1 ton red mud (Fe 15%)+40 kg pyrite is
needed to get 232 kg Fe3 O4 upon
magnetic separation.
At least 10 kg pyrite is needed to
guarantee the transformation, but 167 mol
SO2 might be released.
23. 23
Hematite can be transformed into
magnetite at 525 ◦ C
The released SO2 used for sulfuric acid
production
This method is expected to be applied in
industry only if the amount of the pyrite is
calculated based on the content of Fe2 O3
in red mud.