2
iron oxides such as goethite as compared to hematite [18].
Hematite is a refractory oxide with a crystalline structure,
making it more resistant to microbial attack [19]. While
organic compounds such as acetic acid or citric acid can act
as reductants, the rate of reduction and iron dissolution is
slow. However, metal-reducing organisms can greatly accel-
erate the reduction of iron, making the process practical.
The objective of this study is to reduce iron using a
mixed culture of iron-reducing organisms under anaerobic
conditions to dissolve iron from the iron tailings. Two dif-
ferent types of iron tailings, one primarily goethite, and the
other primarily hematite, were used in bioleaching experi-
ments to study the effect of mineral type on dissolution.
Experiments were conducted in a 250 mL flask focused on
iron reduction from goethite and hematite.
MATERIAL AND METHODS
Sample Collection and Characterization
Iron ore tailings from two different sources were used in
this study. Tailings from Source A were rich in goethite
and quartz, while those from Source B primarily con-
tained quartz and hematite. The composition of the ore
tailing samples, as analyzed by X-ray diffraction, is given
in Table 1, and the particle size distribution is shown in
Figure 2.
Figure 1. Pourbaix diagram for iron in water, showing the oxidation state of the iron as a
function of redox potential and pH [9]
Table 1. Specifications of the iron ore tailing samples for
bioleaching experiments
Source Composition
A Goethite (FeOOH): 19.3%
Hematite (Fe
2 O
3 ):5.9%
Quartz (SiO
2 ):74.8%
B Hematite (Fe
2 O
3 ):15.1%
Quartz (SiO
2 ):84.9%
Figure 2. Particle size distribution of the iron ore tailing
samples
iron oxides such as goethite as compared to hematite [18].
Hematite is a refractory oxide with a crystalline structure,
making it more resistant to microbial attack [19]. While
organic compounds such as acetic acid or citric acid can act
as reductants, the rate of reduction and iron dissolution is
slow. However, metal-reducing organisms can greatly accel-
erate the reduction of iron, making the process practical.
The objective of this study is to reduce iron using a
mixed culture of iron-reducing organisms under anaerobic
conditions to dissolve iron from the iron tailings. Two dif-
ferent types of iron tailings, one primarily goethite, and the
other primarily hematite, were used in bioleaching experi-
ments to study the effect of mineral type on dissolution.
Experiments were conducted in a 250 mL flask focused on
iron reduction from goethite and hematite.
MATERIAL AND METHODS
Sample Collection and Characterization
Iron ore tailings from two different sources were used in
this study. Tailings from Source A were rich in goethite
and quartz, while those from Source B primarily con-
tained quartz and hematite. The composition of the ore
tailing samples, as analyzed by X-ray diffraction, is given
in Table 1, and the particle size distribution is shown in
Figure 2.
Figure 1. Pourbaix diagram for iron in water, showing the oxidation state of the iron as a
function of redox potential and pH [9]
Table 1. Specifications of the iron ore tailing samples for
bioleaching experiments
Source Composition
A Goethite (FeOOH): 19.3%
Hematite (Fe
2 O
3 ):5.9%
Quartz (SiO
2 ):74.8%
B Hematite (Fe
2 O
3 ):15.1%
Quartz (SiO
2 ):84.9%
Figure 2. Particle size distribution of the iron ore tailing
samples