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WELLINGTON, New Zealand -- Extracting gold from plants sounds like
modern-day alchemy, but New Zealand scientist Chris Anderson has managed to
do it in the laboratory.
Now he plans to test it in the field.
"I'm feeling very confident that we can move to the next step but only time
will tell," says Anderson, 26, who graduates this week with a Ph.D. in
earth science from Massey University <http://www.massey.ac.nz>.
Hundreds of plants naturally accumulate metals from the soil in which they
grow; nickel, for instance, can accumulate in plants and can be extracted.
Anderson's academic supervisor, Professor Robert Brooks, named this process
"phytomining" back in 1977.
However, metals such as zinc, lead, and gold have been exceptions. The
challenge for scientists has been to make those very dense metals -- gold
included -- more soluble so they can extract them from the soil. Anderson
says he's been able to do it.
Anderson was inspired about four years ago, when researchers in the United
States successfully made lead soluble enough for plants to soak up. "We
thought, if you can do it for lead, why can't you do it for other metals?"
he said.
A year later, Anderson and fellow student Brett Robinson managed to make
gold soluble enough that plants did draw it out of the earth. "For about a
month there was so much gold in the measuring machine that we couldn't use
(the machine)," Anderson said.
Further laboratory and greenhouse trials ensued: "We can definitely get the
gold into the plants," he said.
Anderson plans a field trial on a couple of hectares of tailings at an
abandoned mine near Te Aroha
<http://www.thepeninsula.co.nz/tearoha/index.htm> in New Zealand
<http://www.govt.nz/aboutnz/nzmap.php3>'s North Island. "Currently, there's
nothing growing on it," he said, adding he hopes to obtain a kilogram of
gold from each hectare of tailings.
Anderson will sow quick-growing plants such as oilseed rape. When they
reach their maximum weight, he'll add the sulfur concoction to the soil.
This makes any small traces of gold soluble for about 10 days. The plant
soaks up the gold, and once the plant starts to wither, it is dried and
then burned to extract the metal.
If Anderson's research is proved in the field trials, he sees enormous
environmental applications. For example, in South America, many tailings
contain both leftover gold and the mercury used to extract the metal.
"We have people living on these quite barren soils and they try to recover
food crops from them," he said. "So we are saying to them, let's clean up
the environment. And the gold that comes out of the process pays you to do
it, so you've actually got an income coming in." |
