Bioleaching, or microbial ore leaching, is a process used to extract metals from their ores using bacterial micro-organisms. The bacteria feed on nutrients in the minerals, causing the metal to separate from its ore. The metals commonly extracted using this process include gold, silver, zinc, copper, lead, arsenic, antimony, nickel, molybdenum cobalt, and uranium.
Bioleaching is performed mostly by iron and sulfide oxidizing bacteria, or acid producing fungus. Some of the types of bacteria used in this process include Leptospirillum ferrooxidans, Thiobacillus ferrooxidans, and some species of sulfolobus, acidianus, and sulfobacillus.
Using micro-organisms helps to reduce production costs, minimize environmental pollution, compared to conventional leaching processes that use cyanide, and to efficiently extract metals, even when their concentration in the ore is low. This process is growing in popularity, as the bacteria can grow naturally in mining environments, and can also be easily cultivated and recycled.
Bioleaching provide the following advantages to the extraction of metals:
- Cheaper than chemical extraction
- Simpler than other conventional processes
- Fewer specialists are required
- Environmentally friendly, with no sulfur dioxide emissions as in smelters
- Lower capex and opex than in conventional smelting and refining processes
- High pressure or temperature is not required
- Leaching residues are less active than in physico-chemical processes
- Can partly replace extensive crushing and grinding processes used in a conventional process, which then helps to cut costs and energy consumption
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