Question

Explain briefly about biomining? Explain two types of biomining?(biobleaching and bio-oxidation)

Explain briefly in 300 words

Answer 1

Industries have become increasingly aware about the usefulness of microorganisms in the economic point of view and this usefullness has been extended upto the fact of using them for extraction or recovering base and precious metals from ores and other solid materials or mine wastes. This method called biomining is considered to be more environmental friendly than the conventional method though the leaching process may take days or even months to complete.

The mostly used bacteria include Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans among others, which are anaerobic, autochemotrophic and can survive in pH range of 2-3

Valuable metals of interest are usually present in bound form and these microorganisms can oxidise them, dissolving them in water. On the other hand, a different approach can also be used for metals which are not easily dissolved and in this technique, the microorganisms break down the surrounding mineral and hence making it easier to extract the desired metal or element.

The common processes involved are the

1. Heap leaching

2. Dump leaching

3. Agitated leaching

The two types of biomining are
a. Bio-oxidation - In this process, oxidation is caused by the microorganisms leaving the solid phase and the solution. The metal of interest remains in the solid phase while the solution can be discarded.

b. Bioleaching- It is also an oxidation process that utilises microorganisms in which the metal of interest is available in solubilised form.