Flashcards in Biological Metal Extraction Deck (10):
What is Acid Mine Drainage?
Mines often flood when abandoned
Metal Sulfides oxidise underwater, producing sulfuric acid which reacts with other metal ores leaving soluble metal compounds (basis of bioleaching)
What is Bioleaching?
Biological method of Metal extraction in which bacteria speed up reactions that release soluble metal compounds from metal sulfides
What happens in the process of Bioleaching?
Bacteria oxidise iron(II) and sulfide ions and use energy transferred
Sulfuric acid forms in the presence of water and oxygen
It breaks down copper sulfides ores and other minerals releasing copper (II) ions and other metal ions
What are the advantages of Bioleaching?
Metals can be extracted from low grade ores (contain too little metal for other methods to be profitable)
Bacteria occur naturally - don't need special treatment
Doesn't release harmful sulfur dioxide
What are the disadvantages of Bioleaching?
Toxic substances sometimes produced
What is Phytoextraction?
Biological method of metal extraction where plants absorb metals through their roots and concentrate them in their cells
How is phytoextraction possible?
Plants absorb dissolved ions through their roots
Some plants are good at absorbing metal ions which accumulate in roots, shoots, leaves
What happens in the process of phytoextraction?
A crop is planted in soil containing low grade ore or mine waste
'Complexing Agent' may be added so plants absorb metal ions more easily
Plants are harvested
Plants are burnt to produce ash with high concentration of metal
Metal can be extracted as if ash was high grade ore
What are the advantages of phytoextraction?
Produces less waste
Involves smaller energy transfers
Closer to being carbon neutral activity that can contribute to sustainable development