C14 - Resources Flashcards
Two methods of extracting copper
• Bioleaching
• Phytomining
What is 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 or burned in a furnace. The ash contains soluble copper compounds from which copper can be extracted by electrolysis or displacement using scrap iron.
What is bioleaching?
• bacteria are used to convert copper compounds in the ore into soluble copper compounds, separating out the copper from the ore in the process. The leachate (the solution produced by the process) contains copper ions, which can be extracted by electrolysis or displacement with a more reactive metal.
What is displacement?
• a redox reaction
• involves one metal kicking another one out of a compound
• if you put a reactive metal into the solution of a dissolved metal compound , reactive metal will replace the less reactive metal in the compound
Iron and copper sulfate displacement
• if you put iron in a solution of copper sulfate, the more reactive iron will displace the less reactive compound from the solution. You end up with iron sulfate solution and copper metal.
• in this reaction, iron loses two electrons to become a 2+ iron - oxidised
What is electrolysis?
• uses electrical current to cause a reaction
• an electric current is passed through an electrolyte (molten or dissolved ionic compound) ions move towards electrodes, where they react, and the compound decomposes.
• positive ions in the electrolyte will move towards the cathode and gain electrons (they are reduced)
• negative ions in the electrolyte will move towards the anode and lose electrons (they are oxidised).
• creates a flow of charge through the electrolyte as ions travel to the electrodes.
• as ions gain or lose electrons, they form the uncharged element and are discharged from the electrolyte
Describe how bioleaching is used to obtain copper.
• uses bacteria to produce solutions containing copper compounds / leachate solutions
• from which copper is obtained by electrolysis/displacement
