Extraction of Metals

Recycling

Recycling

The purpose of recycling

Even though aluminium, iron oxide and titanium oxide are all found abundantly within the Earth’s crust there are a number of reasons why recycling is a good option:

  • the process of recycling usually requires less energy than extraction
  • quarries and mines are considered eyesores
  • polluting gases, like carbon dioxide and sulphur dioxide, are released with the extraction process
  • it is hard to dispose of scrap metal
  • recycling is considered relatively efficient as the majority of scrap contains a large amount of desired metal

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Problems with recycling

However, there are a number of problems with the recycling process:

  • Scrap metal collection: capital is required to collect the scrap metal from wherever it is.
  • Removing desired metal from the scrap: unless the metal is magnetic, capital is required to manually separate the desired metal from the other metals.
  • Purifying desired metal: capital is also required to return the metal to the purity desired.

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Recycling methods

Aluminium

The majority of recycled aluminium comes from foil and drink cans. Cans are picked up from recycling points, shredded, and the paint removed. This metal is then melted down into big ingots which are then rolled out into sheet metal from which new cans can be formed.

Iron

The majority of recycled iron comes from cars, trains and ships. Specialist metal reclaiming companies are required to collect these objects due to their large size. The objects are cut down into more manageable pieces and a large magnet is used to separate the iron. The scrap is then melted down and purified using the Basic Oxygen Process.

Due to the purity required for commercially used tungsten and titanium, recycling is not a viable option.

Using Scrap Iron to Extract Copper : a level chemistry revision

One method of extracting copper which requires a low amount of energy is to convert the copper compounds into aqueous form and then react them with scrap iron.

The process goes as follows:

  • dilute sulphuric acid and a specialised bacterium are used to convert the copper ores into solutions which contain Cu2+
  • using scrap iron the copper ions are reduced to copper

? Cu2+(aq) + Fe(s) ? Cu(s) + Fe2+(aq)

The advantages to using this process are:

  • very little energy is used (however, to make the iron more energy is required)
  • it uses copper ores of a very low grade which includes copper mining waste
  • iron is less expensive than copper