Extraction of Metals

Extraction of Metals

1. Aluminium

   • Ore is Bauxite
   • Cryolite lowers melting point (950°C)
     • Has to be molten so the ions can move for electrolysis
     • Makes it more economical
   • Electrolysis
     • Anode
       • 2O2- ---->
         O2 and 4e-
         • oxygen formed reacts with the graphite (carbon) anode to form CO2 and degrades anode so need to be replaced
     • Cathode
       • Al3+ and 3e-
         ----> Al
     • Conditions
       • Temp 950°C
         • 200,000 amps
   • Is more reactive than carbon so carbon cant reduce it

2. Tungsten

   • Ore is heated to 650°C and decomposes to WO3
   • Hydrogen is used as Reducing agent
     • Carbon isn't used due to formation of tungsten carbide which is brittle
     • risks of explosions and problems with storage with using hydrogen
     • Tungsten (VI) Oxide - WO3 is heated with hydrogen at 900°c
       • WO3 + 3 H2 → W + 3 H2O
     • Readily available creates no pollutants Higher Purity

3. Titanium

   • Ore is Rutile-TiO2
   • electroylsis wont work as it needs to be very pure
     • carbon recuction froms carbides so isnt used
   • TiO2 + 2 Cl2 + 2 C → TiCl4 + 2 CO at 900°C
     • TiCl4 is purified by fractional distillation in an argon atmosphere
     • TiCl4 + 4 Na → Ti + 4 NaCl
       • Reduction with either Sodium or magnesium under an inert argon atmosphere at 500°C
       • TiCl4 + 2Mg → Ti + 2 MgCl2
   • Expensive due to: cost of the Na or Mg,batch process (start/stop),high temperatures, argon atmosphere.

4. Iron, Manganese and copper

   • Reduction by Carbon/Carbon Monoxide
     • Cheap and readily available
       • Produce pollution
   • Copper can also be extracted by using the displacement reaction of scrap iron with an aqueous solution of copper. Solution is made by reacting Copper ores with Sulphuric Acid. The more reactive iron displaces the copper by reducing the copper ions.
     • Source of the copper for the solution is the low grade ores/scrap
       • uses lower temperatures and lower grade ores

5. Sulphides

   • Metal ores are often found as Sulphide ores
     • They are roasted in air (oxygen) to form oxides and then reduced with carbon
       • Cu2S + 2O2→
         2CuO + SO2
   • Production of SO2 causes acid rain
     • However can form sulphuric acid to increase atom economy and reduce environmental impact

6. Recycling Metals

   • Advantages:Reduces waste, requires less energy, saves raw materials, less expensive.
   • Disadvantages: Collecting/Sorting material is difficult, Purity of recycled metals is lower (has other metals mixed in)