26
Manganese [Mn, 25]

26.1 INTRODUCTION
Manganese (Mn), a metal of the group 7 in the periodic table of elements, is one
of the most abundant trace elements in the lithosphere, and is the second, after Fe,
metal in the Earth’s crust, at mean concentration of 0.085%. Its common occurrence in rocks ranges from 350 to 2000 mg/kg, and higher concentrations are
in mafic rocks, as well as in Mn–Fe concretions, especially deposited in oceanbottom sediments. In sedimentary rocks, it may be concentrated up to 1000 mg/kg.
Contents of Mn in coal vary within the range of 50–100 mg/kg, and in fly ash may
be about 400 mg/kg.
Manganese occurs mainly at +2 oxidation stage, but may change valences up to +7.
It is a member of the Fe family, and is highly associated with Fe, in all geochemical processes. There are many Mn minerals, mainly together with other metals,
especially with Fe. The most common is pyrolusite, β-MnO 2 ; other minerals are
manganite, γ-MnOOH; hausmannite, Mn 3 O 4 ; and rodochrozite; MnCO 3 . The Mn
oxide mineral birnessite, (Na 0.3 Ca 0.1 K 0.1 )(Mn 4+ ,Mn 3+ ) 2 O 4 ·1.5 H 2 O, of an unconfirmed
composition, is formed due to precipitation in lakes, oceans, and groundwater. It is a
major component of desert varnish and deep sea Mn nodules, exhibits a large adsorption capacity to several metals (Cd, Co, Cu, Pb, and Zn), and has a high oxidizing
potential (Feng et al. 2007). Sorption capacity of MnO 2 for several metals is comparable to that of goethite and hematite.
During weathering, Mn in minerals is oxidized, and forms secondary minerals,
often as concretions and nodules. Under weathering in tropical and subtropical conditions, Mn is concentrated in residual deposits, whereas under humid climate, it
is leached by acid solutions from sediments and soils. These processes resulted in
Mn accumulation, as concretions in various sediments (e.g., deep-sea polymetallic
concretions), and in soils.
World mine Mn production (rounded) in 2010 (without the United States) was
13,000 kt, of which China produced 2,800; Australia produced 2,400; and South
Africa produced 2,200 (USGS 2011). Manganese is used as alloying element with
various metals, but especially with Fe (e.g., steel). There are great uses of Mn other
than in steelmaking. The amount of domestic Mn consumption is estimated to be in
the range of 5%–10% of its metallurgical uses. Mn is used chiefly as MnO 2 (e.g., for
dry cell batteries), and as MnO. Manganese has been used as a fuel additive methylocyclopentadienyl manganese tricarbonyl (controversial gasoline additive; MMT).
Potassium permanganate is a strong oxidizing agent used for water treatments and
several other purposes.
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