Extraction by Bacteria Leaching

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Extraction by Bacteria Leaching

Copper and Gold can be extracted from their ores by using bacteria leaching.

A long time ago, engineers investigating the possibility of reopening the Roman workings noticed a blue-green liquid running from the mountains of excavated rock. When the fluid ran across old iron implements, it left a brown film. When scraped off, the film was pure copper. In 1947, US microbiologists discovered that the transformation was in fact the work of microorganisms.

Bio leaching process is studied to leach copper and zinc from low-grade ores; and zinc silicate waste, respectively by Thiobacillus.

Bacteria such as Thiobacillus ferro-oxidans and Thiobacillus thio-oxidans obtain the energy they need to live by oxidising Fe2+ ions and S2- ions respectively. The S2- ions are present in insoluble minerals of copper, zinc and lead. The oxidation of the S2- ions by bacteria releases these valuable metal ions into solution.

Humans can achieve the same result only by smelting ores at high temperatures, a far more polluting and energy-intensive approach.

Biohydrometallurgy is an application in mining. In its natural state a metal such as copper is found combined with other elements in the mineral chalcopyrite. A bacterium is then used to form the compound copper sulphate, which in turn can be treated chemically to obtain pure copper. This microbiological mining process is used only with low-grade ores and currently accounts for 10% of copper production worldwide.

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Copper can be extracted from its ores by using bacteria.

Firstly the low-grade copper ore and also the tailings are stacked up where the ground has been made impermeable.

The ground is sprayed with the acidic leaching solution (Thiobacillus Ferro oxidans and T. Thio-oxidans). This solution is used because the bacteria used, thrive in acidic conditions and they also don't need any organic material on which to feed. The bacteria require Fe ions, or S ions, oxygen and carbon dioxide. The bacterium may also need bacterial nutrients containing nitrogen and phosphorus. The result is that the ...

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