The chemistry of copper - how it is extracted and purified.

At the top, the ore is crushed even further into grain-like pieces.

The ore is mixed with water and other special chemicals to remove the waste rock and float the copper ore so it can be skimmed off the water.

It then is heated to purify the copper and separate it from any other metals (alloys).

The ore is treated with dilute sulphuric acid.

This trickles slowly through the ore and dissolves copper to form copper sulphate.

Then a method called ‘Froth Flotation’ is enforced to concentrate the ground ores. The process involves chemical treatment of an ore to create conditions where the particles of the mineral will form air bubbles. The air bubbles carry the selected minerals to the surface of the pulp, there forming a froth which is skimmed off and other minerals remain submerged in the pulp.  

This entire process is called ‘Leaching’.

What ores are mined?

Some of the ores that are mined are cuprite, Bornite, Malachite, Azurite, Tennantite,

How much is left?  

Copper ore deposits will become scarce in a relatively short time, but the copper which has been extracted can be recycled fully. Copper is regarded as one of the few metals that are ‘fully sustainable’.

Which countries control the supply of copper?  

Highest copper outputs in the world:

1. Chile      2. USA        3. Peru      4. Indonesia

What is meant by low-grade ores and why are they becoming more important?

A low grade ore is an ore that doesn't contain a very high proportion of valuable minerals. Low-grade ores are less valuable than higher-grade ones but are more abundant. They are becoming more important because they are cheap and high-grade ores are running out and becoming more ‘exhausted’ so it is important to obtain copper from sources like low grade ores as well as high grade ores. Low grade ores are required for cement and steel making.

 Where in the world are they found?

Copper can be found in alluvial deposits (gravel carried by rushing streams and deposited where the stream slows down), granitic and basaltic rock. Copper is mined throughout the world and the open pit mines. The top copper mining countries are Chile, U.S.A., Peru, China, Australia, Indonesia, Russia, Canada and Zambia. Copper is found in many other countries as well.

Copper is a good conductor of electricity, and is used extensively to make electrical wiring and components.

After the Froth Flotation of copper is complete the copper produced is 99% pure. However it is for today's market, this is not pure enough. So it is purified even more for use as a conductor using electrolysis.

In this process, the positive electrode (the anode) is made of the impure copper which is to be purified. The negative electrode (the cathode) is a thin bar of pure copper. The two electrodes are placed in a solution of copper sulphate.

Copper ions leave the anode and are attracted to the cathode, where they are deposited as copper atoms. The pure copper cathode increases greatly in size, while the anode becomes smaller because the particles move towards the cathode made of pure copper. The impurities left behind are gold, silver, platinum and tin which are insoluble in this solution so they form a valuable 'sludge' or layer that collects under the anodes.

This entire process is known as electrolytic refining. Even the best chemical method it is not possible to remove all the impurities from the copper, but with electrolytic refining it is possible to produce 99.99% pure copper.

Why is it important to recycle copper?

There are only 25-60 years of copper supply left, so if we recycle copper we can continue to use it otherwise there will be no copper available for in the future which will be a difficult material to live without. It is cheaper to recycle copper than extract new copper. Landfill sites are beginning to fill up and it’s expensive to get rid of it so recycling copper is better.