Alt methods of extracting metals (bioleaching and phytomining)

what is phytomining?

The use of plants to absorb metal compounds. The plants are harvested and then burned to produce ash that contains metal compounds.

What is bioleaching?

(the use of) bacteria to produce leachate solutions (that contain metal / copper compounds)

what is an ore

compound of a metal that is dug up out of the ground

phytomining process

• plants are grown in the soil that contains copper compounds

• plants absorb copper compounds but they can’t use or get rid of them

• Copper compounds gradually build up in the leaves of the plant

• Plant is then harvested, dried and burned in a furnace. The ash contains the copper compounds from which copper can be extracted

• Copper compounds can be dissolved in water and electrolysed to give off copper at the cathode (expensive, needs energy)

• Copper can be extracted through displacement using scrap iron. Makes process cheaper, reduces amount of scrap iron that goes into a landfill

Phytomining equation

Cu²⁺(aq) + Fe(s) = Fe²⁺ (aq) + Cu(s)

Bioleaching process

• Copper compounds in the ore are put into a large container with lots of water so they dissolve in it

• Bacteria is added to the solution and they eat the copper compounds and excrete them

• A leachate is produced (solution produced by the process)

• copper ions in leachate can be extracted by electrolysis or displacement with a more reactive metal

Advantages

• traditional methods of copper mining are very damaging to the environment. The new methods of extraction are cheap and have a much smaller environmental impact

• Require less energy, which is good for the environment because energy use often contributes to climate change and other environmental problems

• Low grade ores used for phytomining and bioleaching don’t need to be mined in the same ways as high grade ores

Disadvantages

slow. For example in phytoming, takes a long time for plants to grow and take up copper