Extraction of Metals

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  • Created by: emma
  • Created on: 06-03-14 21:41
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  • Extraction of Metals
    • Blast furnace
      • Step 1 coke burned in hot air to produce CO2 (endothermic)
        • C + O2= CO2
      • Step 2 more coke reacts with the CO2
        • C + CO2= 2CO
      • Step 3 Iron oxide reduced by CO
        • Fe2O3 + 3CO = 2Fe + 3CO2
        • Fe2O3 + 3C= 2Fe + 3CO
      • C cant be used for Al, Ti or W as it produces impurities (more reactive than C)
      • Continuous process
      • Advantages
        • Cheap raw materials
        • Continuous process means it can be made effciently
        • Endothermic reaction keeps vessel hot  (less energy needed)
      • Disadvantages
        • CO2 is released
        • metals which react with carbon to form carbides cannot be extracted
        • Metals are not that pure
    • Low grade copper ores
      • convert copper compounds into aqueous form
        • using dilute H2S04 and a specialized bacterium
          • Then react with scrap iron
      • Cu(2+) + Fe(s)= Cu(s) +Fe(2+aq)
      • Advantages
        • little energy
        • Works on low grade copper ores including mining waste
        • Iron is much cheaper than copper
    • Electrolysis
      • Al must be molten to conduct electricity
        • Dissolved in molten cryolite requires a lower temperature 900
      • Extraction of Al is a continuous process
      • Electrodes are made of graphite
        • 2AlO3=4Al + 3O2
        • Negative electrode Al(3+) + 3e- = Al
        • Positive electrode 2O(2-)= O2 + 4e-
          • Burns due to O2 produced C(s) + O2(g) = CO2(g)
      • Advantages
        • Continuous process so efficient
        • Makes pure A;
      • Disadvantages
        • high energy cost of electric and melting Al
        • Only works for ionic oxides
    • Extraction of Ti using more reactive metal
      • Batch process
      • Step 1 TiO2 + 2Cl2 + 2C = TiCl4 + 2CO at 900 to convert to liquid
      • Step 2
        • Ar atmosphere to prevent O2 reacting
        • Endothermic (1000)
      • Advantages
        • Produces very pure Ti
      • Disasdvantages
        • batch proces which adds to cost
        • Na/Mg are expensive
        • Ar is expensive
        • High energy costsrequired
    • Roasting
      • Metal oxides easier to extract than sulphides
      • sulphides converted to oxides by roasting in the air
        • 2ZnS(s) + 3O2(g) = 2ZnO(s) + 2SO2(g)
      • Produces SO2 which could lead to acid rain
        • Or used to make sulphuric acid
          • SO2 + H2O +1/2O2 = H2SO4
    • Extraction of W using H
      • WO3 is heated with hydrogen at 900
      • Hydrogen is the reducing agent
      • WO3 + 3H2 =W +3H2O
      • Advantages
        • Produces very pure W
        • Hydrogen is quite cheap
      • Disadvantage
        • High energy costs
        • Hydrogen is flammable
  • Burns due to O2 produced C(s) + O2(g) = CO2(g)

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