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Background
: manganese mine
Manganese is
gray-white metal with a pinkish tinge, and a very brittle but hard
metallic element. Its atomic number 25. In 1774, while heating the mineral
pyrolusite (MnO2,
manganese
dioxide) in a charcoal fire, the Swedish scientist Johann Gahn discovered
manganese.
The heat and carbon in the charcoal separated oxygen from the pyrolusite,
leaving a metallic
manganese residue. This chemical reaction is called a reduction
reaction.
Manganese is a
reactive element that easily combines with ions in water and air. In the
Earth,
manganese
is found in a number of minerals of different chemical and physical
properties, but is never found as a free metal in nature. The most
important mineral is pyrolusite, because it is the main
ore mineral for
manganese.
Trace amounts of
manganese are
very important to good health. It makes bones strong yet flexible, and it
aids the body in absorbing Vitamin B1. It also is an important activator
for the body to use enzymes. As little as 0.00002% Mn in the human body is
essential. Studies have shown that a lack of
manganese leads
to infertility in animals.
Name
The word
manganese
comes from the Latin word magnes which means magnet, because
when
manganese
is alloyed with other metals like aluminum, copper and antimony, the end
product is magnetic.
Sources
Over 80% of the known world
manganese
resources are found in South Africa and
Ukraine. Other important
manganese
deposits are in China, Australia, Brazil, Gabon, India, and Mexico. The
United States imports
manganese
ore because the
manganese
resources in the U.S. are relatively low in
manganese
content per ton of
ore.
Importing these ores is presently more economic than mining them locally.
Most
manganese
ore imported to
the United States
is used to manufacture intermediate
manganese
ferroalloy products and electrolytic
manganese for
use in dry-cell batteries. Only a small amount of the
ore is directly
used in the steel making process.
Some
manganese is
recovered through the reprocessing of scrap metals and steel slag, or the
materials left over from the steel-making process. Though considered waste
in terms of its steel content, slag often contains significant amounts of
other elements that can be recovered.
Deep-sea nodules of
manganese and
other metals are scattered on the ocean floor. They form when the hot
waters from hot springs (called black smokers) on the ocean bottom meet
the cold, deep ocean water. The elements in the hot volcanic waters
precipitate as nodules. Though rich in
manganese
(nearly 25%
manganese)
they are very deep in the ocean and it would cost too much to make them
worth retrieving. This may prove to be an important source of
manganese in
the future should reserves in the Earth’s crust be depleted and
cost-effective deep-sea mining methods are discovered.
Uses
Steel becomes harder when
it is alloyed with
manganese. It has similar applications when alloyed with
aluminum and copper. Hardened steel is important in the manufacture of
construction materials like I-beams (24% of
manganese
consumption), machinery (14% of
manganese
consumption), and transportation (13% of
manganese
consumption).
Manganese
dioxide is used to: manufacture ferroalloys; manufacture dry cell
batteries (it's a depolarizer); to "decolorize" glass; to prepare some
chemicals, like oxygen and chlorine; and to dry black paints.
Manganese
sulfate (MnSO4) is used as a chemical intermediate and as a
micronutrient in animal feeds and plant fertilizers.
Manganese metal
is used as a brick and ceramic colorant, in copper and aluminum alloys,
and as a chemical oxidizer and catalyst. Potassium permanganate (KMnO4)
is used as a bactericide and algicide in water and wastewater treatment,
and as an oxidant in organic chemical synthesis.
Substitutes and
Alternative Sources
There are presently no
adequate substitutes for
manganese in
its varied applications.
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