Biological methods of Metal Extraction

Extracting copper

• Copper is traditionally extracted by heating copper oxide
• Copper ores are running out and so we need to extract copper from ores containing much smaller amounts of copper compounds
• We will explore two such methods: Bioleaching and phytoextraction
• Both methods cause less damage to the landscape than mining, conserve supplies of higher grade ores and do not produce harmful gases such as sulfur dioxide
• 

Bioleaching

• Uses bacteria grown on a low grade ore
• Bacteria produce a soltuion containing copper ions called a leachate
• Copper is extracted from the leachate by displacement using scrap iron
• Purified using electrolysis
• This method can also be used for nickel, cobalt and zinc
• Does not require high temperatures
• Can produce toxic substances and sulfuric aid

Phytoextraction or Phytomining

• Involves growing plants that absorb metal compounds
• Plants are burnt to form ash, from which metal can be extracted
• Can extract metal from contaminated solids
• More expensive than mining some ores
• Growing plants is dependent on weather conditions