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Colour-change polymer offers sustainable solution to mercury contamination

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South Australian scientists develop a new material to permanently remove mercury from soil and water.

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Australian scientists have developed a new material made from inexpensive industrial by-products to remove mercury from soil and water.

Mercury leaching into the environment after mining and burning fossil fuel can spell biological disaster.

It has toxic effects on bird and fish reproduction, and can retard brain development in children.

Now a team of chemists, lead by Dr Justin Chalker at Flinders University in South Australia, has developed a new material to permanently remove mercury from soil and water.

It’s called Sulfur-Limonene Polysulfide, or SLP for short.

“SLP is a polymer that looks like red rubber, and is made quite cheaply from industrial by-products,” said Dr Chalker. “We can make it into any shape we want.”

As its full name suggests, SLP is manufactured from sulfur – a by-product of the crude oil industry – and limonene, which is found in orange peel and an unused waste material from the citrus industry. Both components are readily and cheaply available, making SLP a highly sustainable product.

“To make the SLP polymer, we melt the sulfur, and add limonene to it and then can coat devices or make it into any shape we like,” said Dr Chalker.

By lining storage containers with SLP, Dr Chalker and his colleagues have successfully removed mercury from river and pond water, and soil.

The material can transform water from toxic to nearly drinkable, with concentrations of mercury reduced a thousand fold, from several parts per million down to only several parts per billion.

As well as being cheap to produce, SLP is self-indicating, turning from red to yellow when it binds mercury.

“This means we know when the SLP is saturated, and needs to be changed,” Dr Chalker explained.

After contact with SLP, mercury remains permanently bound and can be stored safely without further environmental risk.

“The mercury forms nano- and micro-particles that are embedded in the polymer, and don’t get washed off even with flowing water,” said Dr Chalker.

Dr Chalker and colleagues published their paper describing the discovery of SLP in the journal Angewandte Chemie International Edition, and have filed an international patent application describing SLP and its use in removing toxic mercury from the environment.

They are currently seeking industry partners to develop the material further.

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