Growing up, we’ve all heard the same lecture from our parents that, “Money doesn’t grow on trees.” But, according to some scientists, gold might. Environmental Geochemist Chris Anderson says that under certain chemical conditions, gold solubility can be forced.
Using plants to absorb metal is not a new technique. Over the years, scientists have conducted various experiments using certain plants that have the natural ability to absorb and concentrate metals such as nickel, cadmium and zinc. Scientists have often explored the use of these plants, referred to as hyperaccumulators, to remove pollution from the air.
However gold doesn’t easily dissolve in water, so there weren’t any known gold hyperaccumulators to take up the particles through their roots. That is until 15 years ago, when Anderson first showed that it was possible for mustard plants to take in gold from chemically-treated soil containing gold particles.
The method of using plants to extract particles of gold from soil is called phytomining. It works by taking a fast-growing plant with leafy mass, such as mustard, sunflowers or tobacco, and planting the crop on soil that contains gold. Once the plants grow to their maximum height, the soil is then treated with a chemical to make the gold soluble. The plant will then absorb the gold water from the soil and store it within its biomass until it’s harvested.
As gold behaves differently in plant material, extracting the gold from the plants is not quite as easy as getting them to absorb it, Anderson told Live Science. If the plants are burned to remove the gold, some of it will remain attached to the ash, but some of it will also dissolve. And processing the ash requires large amounts of acids, which can be unsafe to transport.
For these reasons, gold phytomining is unlikely to replace traditional gold mining, Anderson explains. But it does present a valuable opportunity for chemists to use the gold nanoparticles found in these plants as a catalyst for chemical reactions.
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