Red mud is a toxic residue from bauxite processing that contains 10-30% hematite. This document proposes a method to transform the hematite in red mud into magnetite, the highest grade iron ore, using pyrite. Laboratory experiments showed that mixing pyrite and red mud in a 1:4 or 1:8 ratio, then roasting under nitrogen at 600 degrees C, results in 23% weight loss as the pyrite decomposes and sulfur is released. X-ray diffraction analysis identified the product as magnetite. On a larger scale, 1 ton of red mud mixed with 40 kg pyrite can produce 232 kg of magnetite concentrate containing 38.7% iron. The released sulfur dioxide could also be used

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Recycling of Iron from Alumina’s
tailing
Make Toxic Red Mud environment
friendly
To make the Tailing Profitable

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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

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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’

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Flow-sheet diagram of recycling of Iron from red mud

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 XRD (X-Ray diffraction): for mineralogy &
crystallography
 XRF (X-Ray Fluorescence): for elemental
analysis
 TGA (Thermogravimetric Analysis):
thermo-analytic technique,works on
increasing temprature (heating rate)
TERMINOLOGY

11.  DTA (Differential Thermal Analysis):
thermo-analytic technique,records
temprature difference between Sample &
Reference
 Anaerobic roasting: heated below melting
point in absence of air
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 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

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 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

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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

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17. a= from a Alumina plant in Shanxi,China.
b= from a Alumina plant in Henan,China.
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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

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 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

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 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

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 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.

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 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.

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