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Learn about phytomining and bioleaching as alternative ways to extract copper from low-grade ores. Understand the process and environmental issues associated with these methods. Includes a lesson on copper extraction through electrolysis.
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Learning Objective To be able to: Describe alternative ways to get copper Key Words: Phytomining, bioleaching, copper ore
Tuesday, 28 June 2016 Alternative methods of extracting metals Date and title in books. You need a pen, pencil & ruler. Starter Activity – 5 minutes Exam question
Smelting • Smelting is the name given to heating ores in a furnace. • We strongly heat the copper with air to produce crude copper. • This is generally the process used to extract copper from copper-rich ores. • For example, copper can be found in chalcocite, which contains copper and sulphur. Copper sulphide + oxygen copper + sulphur dioxide
Sulphur Dioxide • Sulphur dioxide causes acid rain – this means extracting copper has environment issues. • What can sulphur dioxide cause? • Smelting creates impure copper – we have to do another process to get purer copper.
Low-Grade Copper Ores • Some plants absorb copper compoundsthrough their roots. They concentrate these compounds as a result of this. • The plants can be burned to produce an ash that contains the copper compounds. • This method of extraction is called phytomining.
Low-Grade Copper Ores • Some bacteria absorb copper compounds. • They then produce solutions called leachates, which contain copper compounds. This method of extraction is called bioleaching. • Copper compounds in leachates can be used to obtain pure copper by displacement using iron or by electrolysis. • Bioleaching is a slow process. It can take years to get just 50% of the metal from the low-grade ore.
How do we extract copper by electrolysis? • Malachite is an ore containing copper compounds. When it is put into acid, the ions in the compounds are free to move. Electrolysis can then be used to extract copper.
Step A – Making a salt Copper carbonate + sulphuric acid > copper sulphate + carbon dioxide + water CuCO3 + HS2O4> CuSO4 + CO2 + H2O Extension: is the equation balanced?
Step B electrolysis Copper carbonate + sulphuric acid > copper sulphate + carbon dioxide + water CuCO3 + HS2O4 > CuSO4 + CO2 + H2O Copper sulphate + water > copper + Sulphuric acid + oxygen CuSO4+ H2O > Cu + HS2O4 + O2 Extension: is the equation balanced? 2 2 2 2
Half Equations • Cathode Cu2+ + 2e- > Cu • Anode 4OH- - 4e- → O2 + 2H2O