Bioleaching and phytoextraction

What is bioleaching

• uses bacteria grown on a low grade ore

• these bacteria produce an acidic solution containing copper ions, called leachate.

• copper is extracted from this leachate produced by a displacement reaction using scrap ion

• then purified by electrolysis

equations for the reaction in bioleaching

iron + copper sulphate → iron (II) sulphate + copper

Fe + CuSO4 → FeSO4 + Cu

what is phytoextraction

• involved growing plants that absorb metal compounds

• the plants grow in soil containing low percentage of (copper) metal ore

• the plants absorb metal ions through their roots, and then are burnt to form ash, from which the metal is extracted.

what are the advantages of both?

• allows metal to be extracted even from low grade ores, good as metal rich high grade ores are limited, so conserves limited supply of high grade ores

• reduces waste, as waste is used to extract metal (scrap ion, low grade ore)

advantages of bioleaching:

• faster process

• purer metal produced

• energy efficient

disadvantages of bioleaching

• sulfuric acid is produced as a by-product, harmful to the environment

advantages of phytoextraction

• allows extraction of metals from existing contaminated soil, so reduces need to mine to obtain ore.

• this reduces environmental damage, as mining involves quarries, large holes in the ground, which disrupt natural habitats

disadvantages of phytoextraction

• impure metal is produced so requires further extraction, need to use electrolysis to purify

• slow process

• only extracts metal from the ground surface

• toxic/harmful gas given off when burning plants

• high temperatures requires, lots of energy