metal extraction

• Copper ores


  Can be dug up (mined) via traditional means (main ore known as malachite - contains copper carbonate)
• Copper extraction - smelting


  1. Copper ore (chalcocite) contains copper sulfide (Cu2S) which is roasted in air to form copper oxide

  2. This produces sulfur dioxide (SO2), as a by product, that can contribute to acid rain
• Copper extraction - smelting


  1. Copper oxides are smelted (burned in a furnace) with carbon

  2. The carbon reduces the copper oxide to copper in a similar way to the blast furnace for iron, by reacting with carbon to remove the oxygen as CO2
• Greener methods


  • Phytomining - plants grown on copper sites, they take up copper into roots, we burn them and get the copper
  • Bioleaching - bacteria naturally oxidise metal sulfides to the metal. We can farm them to do this for us
• Phytomining


  Involves using plants to extract the metal compounds present in copper rich soils
• Phytomining


  1. As the plants grow they absorb the copper from the soil

  2. Once the plants have grown they are burned to produce ash that contains the metal compounds

  3. The ash is processed so that metal can then be extracted using electrolysis
• Phytomining


  Cleaner and less polluting but slow
• Bioleaching


  Extraction of copper from its ore through the use of living organisms (bacteria)
• Bioleaching


  • Cheaper & cleaner than traditional smelting as no greenhouse gases are produced and can be used to extract copper from ores that would otherwise be considered as being commercially unviable
  • But it is much slower & does release some by-products that are toxic to the environment
  • It is also inefficient, producing much waste
• Bioleaching


  1. The bacteria oxidises compounds in the soil to form sulfuric acid

  2. The sulfuric acid produced breaks down the copper sulfide

  3. This produces a solution called a leachate that contains the copper ions from the ore

  4. Using electrolysis we can then extract the copper from the solution
• Extraction of copper using electrolysis

  1. Copper is present in the solution as Cu2+ ions

  2. These positively charged copper ions move to the negatively charged CATHODE

  3. Here they gain electrons to become Copper (Cu) which builds up on the negative electrode

  4. This purifies the copper as other impurities do not travel to the cathode to be deposited
• Extraction of copper using electrolysis


  • Copper produced this way is very pure
  • Unfortunately electrolysis is very costly as it requires electricity. Also fossil fuels are burnt to generate the electricity
• The reactivity of a metal determines the method of extraction


  • Metals above carbon must be extracted using electrolysis
  • Metals below carbon can be extracted by reduction with carbon, coke, or charcoal
  • Gold and silver do not need to be extracted. They occur native (naturally)
• Ore


  A metal compound within a rock
• Ores are mined and then purified
• The Reactivity Series

  • Potassium
  • Sodium
  • Calcium
  • Magnesium
  • Aluminium
  • Zinc
  • Iron
  • Tin
  • Lead
  • Hydrogen
  • Copper
  • Mercury
  • Silver
  • Gold
• Copper-rich Ores

  Ores containing large amounts of copper
• Smelting


  1. 80% of copper is produced this way

  2. Heat copper ore in a furnace with air

  3. Then use electrolysis to purify the copper

  4. Expensive as needs lots of heat and power
• Copper Sulphate


  1. Add sulphuric acid to a copper ore

  2. Produces copper sulphate

  3. Extract copper using electrolysis or displacement
• Low Grade Copper Ores


  Ores containing small amounts of copper
• Phytomining


  1. Plants absorb copper ions from low-grade ore

  2. Plants are burned

  3. Copper ions dissolved by adding acid

  4. Use displacement or electrolysis to extract pure copper
• Bioleaching


  1. Bacteria feed on low-grade ore

  2. Producing a waste product that contains copper ions

  3. Use displacement or electrolysis to extract pure copper
• During electrolysis

  1. Positive metal ions move towards the negative electrode

  2. Negative non metal ions move towards the positive electrode