Week 3

• Metal ore


  A rock containing a metal (in elemental form or a compound) in a high enough concentration to make it worthwhile extracting the metal
• Metal ores


  • Galena (lead sulfide)
  • Cinnabar (mercury sulfide)
  • Pyrite (iron sulfide)
  • Sphalerite (zinc sulfide)
• Most common metal ores

  • Oxides
  • Sulfides
• Sulfides are the oldest ores, formed in the Earth's history when there was a lot of sulfur from volcanic activity
• Metal ore deposits are a finite resource (there are only a certain amount of them) and non-renewable (once used, they are gone and will not be replaced)
• Some common metals, their ores and chemical formulae

  • Aluminum - Bauxite - Al₂O
  • Chromium - Chromite - FeCr₂O
  • Copper - Chalcocite - Cu₂CO (OH)
  • Iron - Hematite - Fe₂Ox
  • Mercury - Cinnabar - Hg5
  • Titanium - Rutile - TIO
• Extracting metals


  The method used depends on the metal's reactivity
• Reactivity of metals


  • Most reactive - Extracted by electrolysis: Sodium, Potassium, Calcium, Magnesium
  • Extracted by reduction with carbon or carbon monoxide: Iron, Lead
  • Least reactive - Native metal or extracted by various chemical reactions: Gold, Platinum, Silver, Copper
• Reduction


  The process of removing oxygen
• Oxidation


  The process of gaining oxygen
• Blast Furnace


  Industrial extraction
• Raw materials for blast furnace

  • Iron ore
  • Coke
  • Limestone
  • Hot air
• Iron ore


  • Source of iron
• Coke


  • As a fuel and to produce carbon monoxide for the reduction
• Limestone


  • To remove impurities (slag formation when limestone breaks down and reacts with sand/rock)
• Hot air


  • Provides oxygen so that coke can burn
• Blast furnace process


  1. Combustion-carbon to carbon monoxide

  2. Reduction-iron (II) oxide to iron

  3. Decomposition-calcium carbonate to calcium oxide

  4. Neutralisation-calcium oxide and silicon oxide neutralisation
• Combustion stage


  Carbon burned to form carbon monoxide
• Reduction stage


  Iron (II) oxide reduced to iron by carbon monoxide
• Decomposition stage


  Calcium carbonate decomposes to form calcium oxide
• Neutralisation stage


  Calcium oxide reacts with silica impurities to produce slag
• Getting the furnace up to temperature takes a lot of time and costs a lot
• Raw materials are constantly added and products removed - the process is continuous
• At the factory in Port Talbot, iron ore, limestone and coke are imported from other countries even though they are available in Wales
• Using raw materials from Wales is not sustainable due to cost and the effect it could have on the environment (quarrying)
• Electrolysis


  The process by which ionic substances are broken down into simpler substances using electricity
• Electrolysis


  • Metals and gases may form at the electrodes
  • Ions must be free to move (dissolved in water or molten)
  • Positive electrode (anode) attracts negatively charged non-metal ions
  • Negative electrode (cathode) attracts positively charged metal ions
• Electrolysis process


  1. Non-metal ions lose electrons at anode (oxidation)

  2. Metal ions gain electrons at cathode (reduction)
• Oxidation


  Loss of electrons
• Reduction


  Gain of electrons
• Aluminium extraction


  Electrolysis method used to extract aluminium from aluminium oxide
• Aluminium is the most abundant metal on Earth, but it is expensive due to the amount of electricity used in the extraction process
• Aluminium extraction process


  1. Bauxite ore purified to yield aluminium oxide

  2. Aluminium oxide dissolved in molten cryolite to lower melting point

  3. Aluminium ions attracted to negative electrode (cathode)

  4. Oxygen ions attracted to positive electrode (anode)
• Oxygen formed reacts with carbon anodes, forming carbon dioxide and requiring anodes to be replaced frequently, increasing costs
• Factors affecting location of industrial plants

  • Primary reason is for importing raw materials, not exporting products
  • Site away from built up areas
  • Town/city within commuting distance for workforce
  • Good transport links
  • Direct electricity supply (power station)
• Electrolysis is an expensive process as it needs a lot of electrical energy constantly
• Aluminium is reactive so it needs an enormous amount of electricity to separate it from oxygen
• When Wylfa Power Station was decommissioned, Anglesey Aluminium closed as it could not guarantee electricity supply
• Factories are located near the coast as they need to import the aluminium ore from abroad
• Recycling aluminium uses only about 5% of the energy needed to extract it from bauxite and saves waste