Metal Extraction

• Energy requirements
• Cost of reductant
• Metal purity required

Rocks containing a high enough percentage of metal to be extracted commercially

Oxides and Sulphides

• Roasting in air

Scarce in Eath's crust but occur in high grade ores in a few locations

• Most abundant metals in Earth's crust
• Widely distributed

• Carbon is cheap and plentiful
• Used in the form of coke (made by heating coal in the absence of air)
• For some metals, the temperature required is excessively high (so uneconomic) and metal carbides are formed rather than the metal itself (e.g. aluminium, tungsten, titanium)

• Used for extraction of IRON, MANGANESE and COPPER

• Haematite is the main ore of iron and contains 
• Coke is burned in hot air producing CO and lots of heat

• High temperatures in furnace mean more coke is reacted with CO to produce CO

• Reduced by carbon monoxide (most common):

• Or, carbon (in hottest parts of furnace):

• Limestone removes sandy impurities (forming **** -used in road making)

• Formed from reduction of manganese (IV) oxide with carbon:

• Malachite contains        which on heating forms copper (II) oxide.

• Copper can be formed by reduction with carbon:

• Not much copper is made this way as newer, alternative methods from aqueous solutions have been developed which have environmental advantages.

• Tungsten cannot be heated with carbon because tungsten carbide is formed
• Tugsten (VI) oxide (WO  ) is heated with hydrogen at 900C

• Raw materials for the extraction of aluminium are purified aluminium oxide and cryolite (       )
• Aluminium oxide must be molten or dissolved to conducts electricity, and so is dissolved in molten cryolite ( this requires a lower temp. than using molten aluminium oxide so has lower energy costs)
• Electrodes are made from graphite (carbon)
• Continuous process

• Positive electrode burns due to O produced there ( forming CO ) so must be replaced frequently
• Main cost is electricity so often built near hydroelectric power stations.

• If reacted with C, titanium carbide is formed which is very brittle.
• Titanium is useful because it is abundant, has a low density and is corrosion resistant - used for making strong, low density alloys for use in aircraft, hip joints and nuclear reactors.
• Must be very pure so electrolysis not suitable.
• Must be reacted with a more reactive metal (Mg or Na)
• TiO  (solid) is converted to TiCl (liquid) at 900C

• TiCl  is purified by fractional distillation in an Ar atmosphere.

• Ti is extracted by Mg or Na in an ARGON ATMOSPHERE at 1000C

• Expensive due to heat, Na/Mg (made by electrolysis), Ar, and it is a batch process.

• Saves resources (metal ores)
• Creates less waste (mining waste)
• Saves energy resources
• Reduces air pollution

• However, there are costs both financial and energy costs) associated with sorting and transporting metals to be recycled.

• RECYCLING COPPER - react scrap copper with sulphuric acid or a specific enzyme to form solutions containing Cu  (aq)
• Copper can be extracted by reaction with scrap iron (this method can also be used to extract copper from low grade ores)