Extraction

• Ores contain enough metal to make extraction worthwhile.
• A metal can be extracted chemically (by reduction or by electrolysis) or by using biological methods or by using displacement reactions.
• Metal extracted by reduction

  • Uses carbon
  • When an ore is reduced, oxygen is removed from it;
  • 2CuO + C -> 2Cu + CO2
  • copper oxide + Carbon -> Copper + Carbon dioxide
• The position of the metal in the reactivity series determines whether it can be extracted by reduction with carbon.

  
• The Reactivity series

  Please - Potassium (K)

  Stop - Sodium (Na)

  Calling - Calcium (Ca)

  Me - Magnesium (Mg)

  A - Aluminum (Al)

  Careless - CARBON (C)

  Zebra - Zinc (Zn)

  Instead - Iron (Fe)

  Try - Tin (Sn)

  Learning - Lead (Pb)

  How - Hydrogen (H)

  Copper - Copper (Cu)

  Saves - Silver (Ag)
• What ores can be extracted through reduction by carbon?

  Elements below Carbon (C) in the reactivity series.

  • Zinc (Zn)
  • Iron (Fe)
  • Tin (Sn)
  • Lead (Pb)
  • Hydrogen (H)
  • Copper (Cu)
  • Silver (Ag)
• Elements that are more reactive than Carbon are extracted through electrolysis.

  However, this process is far more expensive than reduction.
• Step by step: electrolysis extraction

  1. Melt the metal into a molten compound
  2. Pass an electric current through the molten compound
  3. The metal is discharged at the cathode, and the non-metal is discharged at the anode
• Electrolysis also makes metals pure

  For example, when reduced with Carbon, the copper produced is very impure, and doesn't conduct electricity very well.

  At the cathode (negative electrode), the metal is pure.

  At the anode (positive electrode), the metal is impure.
• Biological methods of extraction:

  Bioleaching

  • Uses bacteria to separate metals from their ores

  Phytoextraction

  • Involved growing plants in soil that contains metal compounds
  • The plants can't use or get rid of the metal, so they gradually build up in the leaves
  • The plants are then harvested, dried and burnt in a furnace