Extraction of metal

Page 1

Sulfide ores are converted to oxides first by roasting in air

It produces Sulfur Dioxide (gas) which causes acid rain but by converting Sulfur Dioxide to Sulfuric Acid a pollutant is avoided, and a valuable product is made

Oxides are then reduced to the metal by Carbon (coke) or Carbon Monoxide

REDUCTION OF IRON (III) OXIDE - in a blast furnace at temperatures greater than 700 degrees

Iron Oxide is reduced Carbon or Carbon Monoxide to produce Iron and Carbon Dioxide

REDUCTION OF MANGANESE (IV) OXIDE - in a blast furnace at temperatures about 1200 degrees

Manganese Oxide is reduced with Carbon or Carbon Monoxide to produce Manganese and Carbon Dioxide

REDUCTION OF COPPER CARBONATE

Copper (in its ore:malachite) is heated indirectly with Carbon to produce Copper and Carbon Dioxide - 2CuCO3 + C --> 2Cu +3CO2

Another method involves heating the carbonate until it decomposes, then reducing the oxide with Carbon - CuCO3 --> CuO + CO2

2CuO + C --> 2Cu + CO2

Carbon and Carbon Dioxide is used because it is cheap

Tungsten is extracted using hydrogen

Tungsten can be extracted from its oxides with carbon, but that can leave impurities which make the metal brittle.

This happens in a furnace at temperatures above 700 degrees

WO + 3H --> W + 3H2O

Hydrogen is expensive and highly explosive when mixed with air

Aluminium is extracted by electrolysis- current: 200,000 A

Aluminium is too reactive to extract using reduction by Carbon

Aluminium ore: BAUXITE

1. All impurities are removed

2. Bauxite is dissolved in molten cryolite (sodium aluminium fluoride)

3. ELECTROLYSIS- Aluminium is produced at the cathode- AL3+ + 3e- --> Al

Oxygen is produced at the anode- 2O2- --> O2 + 4e-

Lowers the melting point= reducing the operating costs

Process is carried out where cheap electricity is available, often near hydroelectric power stations

Titanium is extracted in a batch process

You can't extract titanium by carbon reduction because you will form titanium carbide which make the metal brittle

Titanium ore: RUTILE (TITANIUM (IV) CHLORIDE)

1. The ore is converted to titanium chloride by heating it to about 900 degrees with Carbon in a stream of Chloride gas- TiO2 + 2Cl2 + 2C --> TiCl4 + 2CO

2. The titanium chloride is purified by fractional distillation under an inert atmosphere of argon or nitrogen

3. Then the chloride gets reduced in a furnace at almost 1,000 degrees. It's heated with a more reactive metal such as sodium or magnesium. An inert atmosphere is used to prevent side reactions. TiCl4 + 4Na --> Ti + 4NaCl

TiCl4 + 2Mg --> Ti + 2MgCl2

Mg and Na are reducing agents

Titanium is strong, light and is highly resistant to corrosion BUT it is difficult and expensive to produce

ADVANTAGES:

saves raw materials

saves energy

reduces waste sent to landfill

reduces mining and damages to landscape

DISADVANTAGES:

collecting and sorting metals form other waste can be difficult and expensive

the purity of recycled metal varies

recycling metals may not produce a consistent supply to meet demand

Sulfide ores

Tungsten

Aluminium

Titanium

Recycling