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25-077
Reductive Bioleaching of Iron by Anaerobic Organisms
Palas Kamlakar Borkar
Michigan Technological University, Houghton, MI
Neha Sharma
Michigan Technological University, Houghton, MI
Daniel Amponsah-Berko
Michigan Technological University, Houghton, MI
Kwabena Boafo
Michigan Technological University, Houghton, MI
Timothy Eisele
Michigan Technological University, Houghton, MI
ABSTRACT
A series of iron-leaching experiments were conducted to test
the ability of metal-reducing anaerobic organisms to reduce
iron from Fe3+ to Fe2+ to dissolve it from iron ore tailings.
This bioleaching process involves the fermentation of bio-
mass from Typha latifolia (a common wetland plant) to gen-
erate organic compounds, which, along with metal-reducing
organisms, reduce and dissolve iron. The concentration of
dissolved iron over time was studied for one year. Iron con-
centration above 1150 mg/L was achieved at a pH range of
3.95–5.36. Tailings from multiple locations were examined.
INTRODUCTION
Iron is by far the most widely used metal globally due
to its properties and abundance [1]. 98% of the iron ore
mined globally is used to produce steel [2]. It is a crucial
component in most industries, including construction,
manufacturing, automotive, aerospace, manufacturing,
and machinery, making it a key material in both industrial
and domestic applications. While there are plentiful iron
ore resources, the very high-grade ores are largely depleted.
Technologies are therefore needed that will make it possi-
ble to extract high-grade concentrates from low-grade ores
without causing excessive environmental damage while still
being economical.
Iron occurs in nature in various mineral forms, the
most common being hematite (Fe2O3), magnetite (Fe3O4),
goethite (FeOOH), siderite (FeCO3), and pyrite (FeS2).
In addition to these primary mineral sources, iron can also
be extracted from secondary sources such as mine tailings,
slags, and industrial waste.
The conventional approach for extracting iron involves
several steps, beginning with the mining of iron ore,
followed by crushing, grinding, and beneficiation [3], typi-
cally by some combination of magnetic separation, gravity
separation, and froth flotation [4, 5]. The iron concentrate
must then be chemically reduced to metal at temperatures
up to 1400°C [6]. The conventional approach to extracting
iron from ore is both environmentally harmful and energy-
intensive due to the high temperatures and fuel consump-
tion involved in the process [7].
An alternative way to extract iron is bioleaching, where
iron-reducing organisms reduce iron from the iron ore by a
transfer of an electron, as shown in reaction 1 [8].
Fe3+ +e–→ Fe2+ (1)
As shown in the Pourbaix diagram for iron in water,
once reduced to the Fe2+ state, iron can be dissolved in
mildly acidic conditions (Figure 1) [9]. During the reduc-
tive bioleaching of iron, Anaerobic organisms act as catalysts
and utilize Fe3+ as an electron acceptor in their respiration.
Other organisms also produce organic compounds such as
citric acid, oxalic acid, gluconic acid, and humic acid [10, 11,
12] to increase the solubility of Fe2+ and Fe3+ while also act-
ing as a food source for the metal reducers [8]. Some of the
organisms known for iron reduction in bioleaching include
Penicillia and Aspergilli [13], Acidithiobacillus ferrooxidans
[14], Aspergillus niger [15], Leptospirillum ferrooxidans [16],
Geobacter metallireducens and Shewanella alga [17].
Unlike conventional iron extraction, which involves
significant excavation, high energy use, and the need to dis-
pose large volumes of tailings, bioleaching offers a cleaner
and more sustainable alternative with lower environmental
impacts. Reductive bioleaching applies to variable feed-
stock such as low-grade ores, tailings, slag, and industrial
waste. Reductive bioleaching is most effective on hydrated
25-077
Reductive Bioleaching of Iron by Anaerobic Organisms
Palas Kamlakar Borkar
Michigan Technological University, Houghton, MI
Neha Sharma
Michigan Technological University, Houghton, MI
Daniel Amponsah-Berko
Michigan Technological University, Houghton, MI
Kwabena Boafo
Michigan Technological University, Houghton, MI
Timothy Eisele
Michigan Technological University, Houghton, MI
ABSTRACT
A series of iron-leaching experiments were conducted to test
the ability of metal-reducing anaerobic organisms to reduce
iron from Fe3+ to Fe2+ to dissolve it from iron ore tailings.
This bioleaching process involves the fermentation of bio-
mass from Typha latifolia (a common wetland plant) to gen-
erate organic compounds, which, along with metal-reducing
organisms, reduce and dissolve iron. The concentration of
dissolved iron over time was studied for one year. Iron con-
centration above 1150 mg/L was achieved at a pH range of
3.95–5.36. Tailings from multiple locations were examined.
INTRODUCTION
Iron is by far the most widely used metal globally due
to its properties and abundance [1]. 98% of the iron ore
mined globally is used to produce steel [2]. It is a crucial
component in most industries, including construction,
manufacturing, automotive, aerospace, manufacturing,
and machinery, making it a key material in both industrial
and domestic applications. While there are plentiful iron
ore resources, the very high-grade ores are largely depleted.
Technologies are therefore needed that will make it possi-
ble to extract high-grade concentrates from low-grade ores
without causing excessive environmental damage while still
being economical.
Iron occurs in nature in various mineral forms, the
most common being hematite (Fe2O3), magnetite (Fe3O4),
goethite (FeOOH), siderite (FeCO3), and pyrite (FeS2).
In addition to these primary mineral sources, iron can also
be extracted from secondary sources such as mine tailings,
slags, and industrial waste.
The conventional approach for extracting iron involves
several steps, beginning with the mining of iron ore,
followed by crushing, grinding, and beneficiation [3], typi-
cally by some combination of magnetic separation, gravity
separation, and froth flotation [4, 5]. The iron concentrate
must then be chemically reduced to metal at temperatures
up to 1400°C [6]. The conventional approach to extracting
iron from ore is both environmentally harmful and energy-
intensive due to the high temperatures and fuel consump-
tion involved in the process [7].
An alternative way to extract iron is bioleaching, where
iron-reducing organisms reduce iron from the iron ore by a
transfer of an electron, as shown in reaction 1 [8].
Fe3+ +e–→ Fe2+ (1)
As shown in the Pourbaix diagram for iron in water,
once reduced to the Fe2+ state, iron can be dissolved in
mildly acidic conditions (Figure 1) [9]. During the reduc-
tive bioleaching of iron, Anaerobic organisms act as catalysts
and utilize Fe3+ as an electron acceptor in their respiration.
Other organisms also produce organic compounds such as
citric acid, oxalic acid, gluconic acid, and humic acid [10, 11,
12] to increase the solubility of Fe2+ and Fe3+ while also act-
ing as a food source for the metal reducers [8]. Some of the
organisms known for iron reduction in bioleaching include
Penicillia and Aspergilli [13], Acidithiobacillus ferrooxidans
[14], Aspergillus niger [15], Leptospirillum ferrooxidans [16],
Geobacter metallireducens and Shewanella alga [17].
Unlike conventional iron extraction, which involves
significant excavation, high energy use, and the need to dis-
pose large volumes of tailings, bioleaching offers a cleaner
and more sustainable alternative with lower environmental
impacts. Reductive bioleaching applies to variable feed-
stock such as low-grade ores, tailings, slag, and industrial
waste. Reductive bioleaching is most effective on hydrated