Zusammenfassung der Ressource
The extraction of metals
- found in ores containing oxygen and sulfur
- iron oxide, Fe2O3
- Fe3+ to Fe
- reduction from a 3+ to 0
- copper sulphide CuS, to copper
- +2 to O
- need a cheap, readily available reducing agent
- impurities (gangue) clay and rock have to be removed
- non-polluting and easy to dispose of by-products
- converting sulphides to oxides
- heating in air, called roasting
- zinc sulphide converted to zinc oxide
- ZnS(s) + 1.5O2(g) ---> ZnO(s) + SO2(g)
- however SO2 is an acidic gas and produces (sulphuric acid)
when mixed with water, a contributor to acid rain
- however SO2 can be coverted to sulkphuric acid in
controlled conditions and sold for a variety of purposes
- SO2(g)+H2O(g)+0.5O2(g)-->H2SO4(l)
- choosing a reducing agent
- Coke
- impure form of carbon
- cheaply obtained by heating coal in the absence of air
- however so metals require very high temperatures (ends up uneconomic)
- at high temps metal react with carbon to form carbides
- Hydrogen
- made from methane and water
- used to extract tungsten
- metals high up on the reactivity series
- can use electrolysis
- such as sodium and aluminium
- use a more reactive metals
- recycling and the environment
- iron
- can be melted down and reformed
- easily separated from other
materials because it is magnetic
- does not produce CO2 when melted down
- whereas extraction does
- however energy needs to melt involves the production of CO2
- aluminium
- also recycled by melting
- only uses 5% of energy needs for extraction
- recycling avoids large amount of CO2 formed
- however big rising costs in sorting and
transporting of recycled material