Biohydro-Metallurgy
Biohydro-metallurgy is an application used in mining to extract
certain metals from their ores using specialised bacteria such as
Thiobacillus ferro-oxidans which metabolise certain substances in the
ore to gain the energy they need to live, which breaks it down and
releases the metal ions into solution from which they can be
extracted. The bacteria require very little else to perform this task,
as they require no organic nourishment, apart from a slightly acidic
environment, access to carbon dioxide and oxygen from the air and an
ambient temperature of around 30°c for optimum performance.
Thiobacillus ferro-oxidans oxidise both Fe² and S² ions allowing the
insoluble minerals of copper, zinc and lead to be broken down as they
also contain S² ions. The process can be demonstrated by the oxidation
of arsenopyrite seen in the equation below
2FeAsS + 7O + 4H + 2H O ® 2Fe + 2H AsO + 2HSO The bacterial oxidation
occurs in two stages, the first involving reactions at the boundary
between the surface of the bacterial cell and the asenopyrite, where
the bacteria catalyse the formation of soluble compounds of iron(II),
arsenic (III) and sulphur(VI)
The second stage consists of two separate reactions in whish iron(II)
and arsenic (III) are oxidised.
A prime example of biohydro-metallurgy is the extraction of copper,
often used as a recovery technique, extracting the metal from
low-grade ores that are the waste product of any conventional mining.
The ore is piled up in an area where the ground has been made
impermeable and sprayed with an acidic leaching solution containing
...
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...er different
conditions, testing the limits of the process. Finally, providing that
the process has shown to work well under all expectable conditions and
is financially viable then a full-scale plant may be built.
2) Biohydro-metallurgy is a method of extracting metals from their
ores without using the conventional techniques. It involves using a
bacterium that metabolises certain ions within the ore, breaking it
down and releasing the solution metal from within. It can be used as a
primary method of extraction for gold and a secondary method for
copper.
Bibliography
www.mines.edu/fs_home/jhoran/ch126/thiobaci.htm
http://www.pdti.kmutt.ac.th/annual/report9395/biohydrometallurgy.htm
www.mines.edu/fs_home/jhoran/ch126/thiobaci.htm
http://www.pdti.kmutt.ac.th/annual/report9395/biohydrometallurgy.htm
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