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Metal Extraction

Information on extracting metals.
by

Caroline Avery

on 22 January 2012

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Transcript of Metal Extraction

Metal Extraction Metals are found in Ores. Usually as Oxides or Sulphides. Some Oxides rust e.g. FeO This is a metal Ore. Sulphide ores are usually roasted in air to convert them into Oxides before metal extraction takes place. This is used in the process of extracting gold and silver and is sometimes called Smelting.

This process create large amounts of Sulphur dioxide, which is one of the main causes of the environmental problem of acid rain.
However this Sulphur dioxide can be collected before it enters the atmosphere and used to make Sulphuric acid. Silver Ore Extracting metals can produce gases that are harmful to the environment and use energy sources that are nonrenewable.

Ways to help the environment;
Recycling – Metals can be melted down and reformed
>Recycling Iron - reduces scrap iron that the industrial world discards landfill sites.
>Scrap iron has already been extracted from its ore; it is easily separated as it is magnetic.
>Melting scrap iron does not produce a lot of CO2 in comparison to the process of extracting iron from it's Ore.
>However the energy needed to melt the scrap iron does usually involve the production of carbon dioxide at varying point. Aluminium;
>Recycling aluminium uses about 5% of the energy required to extract Aluminium from its ore.
>Thus avoiding the production of large amounts of CO2.

Unfortunatly recycling causes financial and energy costs to rise, involving the sorting and transporting the recycled material.
Extraction often involves Reduction.
Reduction of metal oxides with carbon: this is used in the extraction of iron.

Reduction of metal halides with more reactive metals: this is used in the extraction of titanium.

Reduction of the metal oxide with hydrogen: this is used in the extraction of tungsten. Carbon monoxide and Carbon can be used
as a cheap reducing agent for Iron, Manganese
and copper.
The metal in placed in a blast furnace, where
temperature is around 2000K.

Iron
Fe2O3(s) + 3CO(g) --> 2Fe(l) + 3CO2(g)
Fe2O3(s) + 3C(s) --> 2Fe(s) + 3CO(g)

Manganese
MnO2(s) + 2CO --> Mn(l) + 2CO2(g)
MnO2(s) + 2C(s) --> Mn(l) + 2CO(g)

Copper
CuO(s) + CO(g) --> Cu(l) + CO2(g)
CuO(s) + C(g) --> Cu(l) + CO(g) Carbon as a reducing agent cannot be used for aluminium - as it is higher than carbon in the reactivity series.
Carbon also can't be used with metals that react with carbon - Titanium and Tungsten, as they form carbides not pure metals. To extract Titanium (Ti), a reactive metal such as Magnesium (Mg) can be used, however it is hard to extract pure Titanium, as the Magnesium and Titanium form an alloy. So first it must be made into a Chloride;
TiO2(s) + 2C(s) + 2Cl2(g) TiCl4(g) + 2CO(g)
And then reduced by either Mg or Sodium (Na);
TiCl4(g) + 2Mg(l) --> Ti(s) + 2MgCl2(l)
TiCl4(g) + 4Na(l) --> Ti(s) + 4NaCl(l) These are exothermic reactions, they are kept very high temperatures (1300K) and are reacted in an atmosphere of Argon, as it is inert, to prevent the reaction of Mg or Na with Oxygen.
This process is known as the Kroll process. By Edward, Jonathan, Caroline and Sammi-Jo Extraction of Titanium (Ti) Extraction of Tungston (W) So how are Titanium and Tungston extracted? A blast furnace Tungsten is extracted through reduction by Hydrogen.

WO3 + 3H2 W + 3H2O

This reaction takes place in very high temperatures. There are significant health risks with this method of extraction as it is dangerous to heat Hydrogen - a highly flamable element. Bauxite is the most common form of impure Aluminium Oxide (Al2O3) Electroylsis equations;
Oxygen is liberated at the anode, which is made of graphite:
2O2 --> O2(g) + 4e

Aluminium is liberated at the cathode, which is also made of graphite:
Al3+ +3e --> Al(l)

The overall reaction is as follows:
2Al2O3 --> 4Al(l) + 3O2(g) Aluminium (Al) is an important metal, but it requires very high temperatures (Al melts at 2000oC) to be extracted. It is dissolved in to a solution (molten cryolite, Na3AlF6) which enables it to be electrolysed at 900oC.

This amount of energy needed to continuously heat the solution is the main expence when producing Aluminium. Another way the costs and impact on the environment have been reduced is by using scrap metal to extract Copper from aqueous solutions instead of using the high-temperature Carbon reduction of the Copper oxide. The advantages of this are;
>It uses very little energy (not including the energy used to make the iron)
>It works on very low grade copper ores, including copper mining waste. Copper ores are converted into solutions containing Cu2+ ions using dilute sulphuric acid.
The copper ions are reduced to copper using scrap iron:
Cu2+(aq) + Fe(s) Cu(s) + Fe2+(aq) The End The Bausxite is purified and then the Aluminium is extracted by Electrolysis.
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