Bioleaching bacteria may become useful in iron ore extraction

Scientists have discovered bacteria that are tolerant of
salt and acid, which have potential to assist mineral leaching in ore
processing.

A CSIRO bio-prospecting survey found the potential ‘bioleaching’
bacteria in the WA Wheatbelt, near Merredin.

Bioleaching is the term given to using microorganisms to
extract metals from ore.

CSIRO environmental microbiologist Dr Suzy Rea headed the
survey, which was conducted under the Water Reuse and Environmental Process
Engineering research program.

“Bioleaching is already commercially up and running, about
15−18 per cent of the world’s copper supply is actually done via bioleaching,”
Rea told Science
Network WA
.

Rea said a key problem for bioleaching in heavy mining
countries such as Australia is the lack of fresh water, with groundwater
becoming increasingly saline.

However, the newly discovered bacteria were found by
searching Wheatbelt farmland drains for salty, acidic water, and are more salt
tolerant than any bacteria previously discovered.

“Usually
microorganisms can handle one extreme condition but not another and our bugs
are already managing acid because all leaching is done, at least for copper
sulphide ores, in an acidic environment,” Rea said..

Rea said that although biological processes are already used
for low-grade sulphide ores and gold extraction, researchers like her are now
looking for ways to use bacteria for oxide ores like iron, which will become
more important as high grade ores begin to run out in the period from 2030 to
2050.

Rea’s research project activities include looking at biofloatation
of iron ores using bacterial microbes and their products to replace the
hazardous chemicals currently used for separating iron ores from gangue ores (valueless
mineral deposits).

Rea’s paper, released last month in Minerals Engineering
journal is entitled ‘Salt-tolerant
organisms potentially useful for bioleaching operations where fresh water is
scarce’
.

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