Extraction of Mercury

Extraction

If the cinnabar is

especially rich, quicklime or iron can be added to promote the extraction process.

Cinnabar contains less than 1% mercury

Reaction with quicklime

4HgS (s) + CaO (s) 4Hg (l) + 3CaS (s) + CaSO (s)

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Therefore mineral-processing methods such as jugging, shaking, screening, elutriation and flotation are performed to extract it.

Reaction with iron

CINNABAR

HgS (s) + Fe (s) Hg (l) + FeS (s)

Cinnabar is the most common and main ore of mercury.

Its formula is HgS - Mercuric sulphide

Hydrometallurgy

Pyrometallurgy

cinnabar in its massive form

• It has a bright red color and can be used to make pigments.
• It is soft and friable.
• Deposits of cinnabar occur mainly in China but can be also mined in Italy, Serbia, Slovenia or Spain.
• It is found near the earth's surface and close to volcanic rocks.
• It is one of the few sulfides that can be transparent.

Mercury is leached from the cinnabar with hydrobromic acid.

The cinnabar is heated with hot air. Oxygen combines with the sulfur to form sulfur dioxide and mercury gas is released. This gas is passed through different tubes until it reaches its liquid state.

Equation for the reaction

cinnabar in its crystal form

-

Mercury can be extracted by:

+

2-

HgS (s) + 4Br (aq) + 2H (aq) HgBr (aq) + H S (g)

2

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Mercury is then recovered from the solution with bromide by electrolysis.

Equation for the reaction

HgS (s) + 0 (g) Hg (g) + SO (s)

-

2-

2+

2

HgBr (aq) Hg (l) + 4Br (s)

4

Mining and extracting mercury

Mercury deposits are small and irregular. They usually appear as veinlets but can be found as disseminated deposits.

Large-scale, highly mechanized mining methods are needed to extract the ore. The most common method is underground mining with conventional drilling and blasting.

Uses of mercury

Mercury has different characteristics and properties that make it extremely useful for different purposes:

• Romans used it in cosmetics.

• Ancient greeks used it in ointments.

• It is used to make thermometers, barometers

and other scientific instruments since it

is liquid at room temperature and has a

high coefficient of expansion.

• By 500 b.c. it was used to make

metal alloys called "amalgams". Some of these metals are gold, silver, zinc or cadmium. These new metal compounds are used in batteries or to extract gold.

• Mercury vapour is used in street lights, fluorescent lamps and advertising signs since they are more energy efficient and incandescent than other lights.

Mercury also forms compounds with other non-metallic elements. Some examples of these are:

2

• Mercuric chloride (HgCl ) - A poisonous salt previously used to disinfect wounds.

• Mercurous chloride (Hg Cl ) - Used as an antiseptic.

2

• Mercuric sulfide (HgS) - Used to make red pigment.

• Mercuric oxide (HgO) - Used to make batteries.

Pollution problems

The main environmental effects caused by the extraction of mercury come from pyrometallurgy; if the condensation of mercury gas goes wrongly, this toxic vapour goes into the atmosphere.

Waste rock and tailings that are created during the mining and ore refining process can release toxins into the environment if not stored or disposed of properly.

Health effects

What is being done

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Methylmercury (CH Hg) is the most toxic form in which mercury can be ingested.

Threat with gold mines

People are exposed to methylmercury almost entirely by eating contaminated fish and wildlife that are at the top of aquatic foodchains.

The contamination caused by mercuric vapours is terribly damaging and needs to be reduced.

It affects the immune system, alters genetic and enzyme systems and damages the nervous system, including coordination and the senses of touch, taste, and sight. It is also particularly damaging to developing embryos.

Mercury is extensively used in gold mining as an amalgam for separating gold from its ore. This amalgam is heated in order to evaporate the mercury and leave the gold pieces. If done without the proper safety equipment, this process can release mercury vapor into the air and can also discharge various amounts of liquid mercury into the nearby area.

Local governments and organizations are putting pressure on mines to decrease their emissions. This can be effective in terms of getting companies to institute new policies or set up new infrastructure, such as wastewater treatment facilities or more effective tailing storage.

Many states in the United states as well as in Mexico (the countries most affected by mercury intoxication through consumption of fish) already have fish consumption advisories.

Elemental mercury, Hg(0), comes from broken thermometers or barometers. It causes tremors, gingivitis, and excitability when vapors are inhaled over a long period of time. It is found in higher concentrations in the environment but is harmless if ingested. Ingestion of other forms of mercury, such as HgCl can damage the gastrointestinal tract and causes kidney failure.

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If these are left out in the open where they are exposed, mercury can be washed into water systems by rainfall, or can leach into the soil.

Properties of mercury

Is also known as "Quicksilver" or as Hydragyrum (liquid silver).

Mercury is a silvery-white heavy metal with a density of about 13.5 g/cm .

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It has fairly low boiling (356.73°C) and melting (-38.83ºC) points and is very brittle when solid.

It is not magnetic and although it is a poor conductor of heat it’s a good electrical conductor.

Mercury is represented with the symbol Hg and has 80 as its atomic number.

It is the only metallic element that is liquid at room

temperature.

Bibliography

• http://www.britannica.com/EBchecked/topic/375927/mercury-processing

• http://education.jlab.org/itselemental/ele080.html
• http://www.chm.bris.ac.uk/webprojects2004/hooper/extraction.htm
• http://www.usgs.gov/themes/factsheet/146-00/
• http://suriname.wedd.de/docs/Pg108-150EnvrHealth.pdf

• http://www.mineralszone.com/minerals/mercury.html

• http://www.worstpolluted.org/projects_reports/display/89

• http://minerals-n-more.com/Cinnabar_Info.html

Extraction of Mercury