L.O: To know the ways in which copper can be extracted from its ore. Extracting Copper L.O: To know the ways in which copper can be extracted from its ore. Thursday, 15 November 2018

Starter Using the reactivity series diagram, answer the questions: What process would you use to extract potassium from its ore? What would you use for tin? What would you use for silver? What would you use for magnesium? What would you use for copper?

Copper extraction using carbon Copper can be easily extracted by reduction with carbon. The ore is heated in a furnace — this is called smelting. However, the copper produced this way is impure so electrolysis is used to purify it.

Copper purification by electrolysis Electrolysis is the breaking down of a substance using electricity. It requires a liquid to conduct the electricity, called the electrolyte. Electrolytes are often metal salt solutions made from the ore (e.g. copper sulfate) or molten metal oxides. The electrolyte has free ions — these conduct the electricity and allow the whole thing to work. In electrolysis there are two electrodes — one is positive and the other is negative. Electrons are lost or gained at the two electrodes — this allows ions to be formed at the positive electrode and atoms to bond at the negative electrode.

Here's how electrolysis is used to get copper… The positive electrode is made of impure copper. Electrons are pulled off copper atoms at the positive electrode, causing them to go into solution as Cu2+ ions. Cu2+ ions move towards the negative electrode, gain electrons and turn back into copper atoms. The impurities are dropped at the positive electrode as a sludge, whilst pure copper atoms bond to the negative electrode.

Extracting Copper from low-grade ores The supply of copper-rich ores is limited and the demand for copper is growing — this could lead to shortages in the future. To help with this, scientists are looking into new ways of extracting copper from low-grade ores (ores that only contain small amounts of copper) or from the waste that is currently produced when copper is extracted. Using traditional methods to extract copper from these low-grade ores is very expensive. Examples of new methods to extract copper from low-grade ores are bioleaching and phytomining.

Bioleaching Bioleaching uses bacteria to separate copper from copper sulfide. The bacteria get energy from the bond between copper and sulfur, separating out the copper from the ore in the process. The leachate (the solution produced by the process) contains copper, which can be extracted, e.g. by filtering.

Phytomining Phytomining involves growing plants in soil that contains copper. The plants can't use or get rid of the copper so it gradually builds up in the leaves. The plants can be harvested, dried and burned in a furnace. The copper can be collected from the ash left in the furnace.

Pros and Cons of bioleaching and phytomining Traditional methods of copper mining are pretty damaging to the environment. These new methods of extraction are cheap and have a much smaller environmental impact. For example, they require less energy which is good for the environment because energy use often contributes to climate change and other environmental problems. Phytomining is also more carbon neutral than traditional methods — even though carbon dioxide is released when the plants are burned, they only release the same amount of carbon dioxide as they absorbed when they were growing. The disadvantage of these new extraction methods is that they're slow. For example, in phytomining it takes a long time for plants to grow and take up copper. MAKE A TABLE SHOWING THE PROS AND CONS OF THESE METHODS!

Pros Cons Smaller environmental impact than traditional methods Slow – e.g. in phytomining it takes a long time for plants to grow and take up copper Cheap Requires less energy Phytomining is more carbon neutral than traditional methods Which do you think is better? Traditional or modern methods? Use the pros and cons in your table and explain your opinion.

Copper extraction by displacement More reactive metals react more vigorously than less reactive metals. If you put a reactive metal into a solution of a dissolved metal compound, the reactive metal will replace the less reactive metal in the compound — this is a displacement reaction. This happens because the more reactive metal bonds more strongly to the non-metal bit of the compound and pushes out the less reactive metal. Copper can be extracted from a solution using a displacement reaction.

Copper extraction by displacement One way this can be done is by using scrap iron. This is really useful because iron is cheap but copper is expensive. If some iron is put in a solution of copper sulfate, the more reactive iron will “kick out” the less reactive copper from the solution. You end up with iron sulfate solution and copper metal. The equation for this reaction is: Haha! Oh… S Fe Cu Fe Cu S