Metals and Extraction

Metals come from the Earth's crust, buried under the ground in rock. This rock where it is found is called an ore. Ores are only ores if they contain enough metal to make their extraction worthwhile. 

Some metals have to be extracted chemically as they are reactive and aren't found in their native form, an example is gold. they are either extracted with electrolysis or displacement with a metal more reactive than it or carbon.

Metals lower than carbon in the reactivity series are cheaper to extract because you don't have to use electrolysis. This is called a displacement reaction.

When a displacement reaction takes place the oxygen is removed from it (e.g. 2Fe2O3 +3C --->   4Fe +3CO2 )

Electrolysis is the process of breaking down ionic substances into simpler substances when an electric current is passed through them. Electrolysis is used to purify copper as well, like this: The copper is dissolved into a chloride solution and then has two sticks of metal stuck in at either end. These metal rods then have a battery attached to them and an electrical current passed through them. 

The science bit is that when the electricity is passed through the copper chlorine solution, it is relieved of the negative copper ions which go over to the cathode while the positive ions go to the anode. at the cathode the extra electrons are removed turning the copper ions back into copper atoms. This copper layer joins at the cathode and then has been successfully been extracted.

Copper can also be extracted with  a solution and displacement reaction using scrap iron and sulfuric acid. 

The iron is more reactive than the copper and so displaces it in the solution of copper sulphate.  This leaves a solution of iron sulphate and copper metal.

Copper Sulphate + Iron Metal ---> Iron Sulphate + Copper

Unfortunately, we are starting to run out of Copper rich ores. Scientists are now looking for ways to extract copper from lower grade ores. Phytomining and Bioleaching are two of these newly found methods.

Phytomining is when plants are grown in copper rich soil. They absorb the copper through their roots and store it in their leaves, (they can't use it), the plants are harvested, dried and burned. The copper is sitting in the ash. the ash is filtered and the copper removed. 

Bioleaching uses bacteria. When placed in a solution of copper sulphide, the bacteria remove the copper by eating away at the bonds between the sulfur and copper for food. the leachate (solution created) is filtered to removed the copper

These methods are less damaging to the environment and cost less to do, but they are slow.

Extracting metals have some impact on the community and the environment.

Extracting metals allow new resources to be made. Which can improve health and transport. This furthers an economy.

Mining ores can be bad as it causes noise, damage to the landscape and after mine shafts have been abandoned they can become dangerous

Recycling metals is important too.  Extracting the metal uses time, money, energy and fossil fuels.

Fossil fuels are running out, so they need to be conserved. Burning them contributes to global dimming, global warming and acid rain.

Recycling metals conserve resources, energy and money.

Recycling metals reduce the amount sent to landfill sites.

Alloying metals tend to make it stronger, an example of this is pure iron. Pure Iron is normally too soft and bendy for any uses. This is because the atoms can easily slide over each other. Alloying it upsets the normal pattern and stops the atoms moving around as easily. So the iron is harder.

Steel is an alloy of iron. When alloyed, steel is made into three types.

Low Carbon Steel: Easily shaped and used in car bodies.High Carbon Steel: Very hard, Inflexible, used in bridges and cutting tool bladesStainless Steel: Corrosion Resistant,used in cutlery

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