Researchers in the United States have announced they had created a paper-like membrane made of nano-scale materials that could clean up oil pollution and other chemical spills.
The substance can absorb up to 20 times its own weight in oil and be recycled again and again for future use, while the oil itself can also be recovered and used, they reported in the specialist journal Nature Nanotechnology.
The novel material comprises wires made of potassium manganese oxide at the scale of 20 nanometres, or 20 billionths of a metre, in diameter.
Together, the wires form a "spaghetti-like mat" whose strands have tiny pores that are good at absorbing liquids.
The membrane is covered with a hydrophobic, or water-repelling, coating. As a result, water cannot penetrate the membrane - but oil can.
"What we have found is that we can make 'paper' from an interwoven mesh of nanowires that is able to selectively absorb hydrophobic liquids from water," said lead researcher Francesco Stellacci, an associate professor of materials science at the Massachusetts Institute of Technology (MIT).
The membrane appears to be completely impervious to water, he said.
"Our material can be left in water a month or two, and when you take it out, it's still dry. But at the same time, if that water contains some hydrophobic contaminants, they will get absorbed."
This also opens the way for using the membrane as a water filter, the team said.
Oil that is snared by the membrane can be removed by heating above the boiling point of oil. The oil evaporates and can be condensed back into a liquid.
In a press release, MIT said the membrane can be fabricated more cheaply than other nano materials. In the same way that cellulose is used for making conventional paper, a suspension is dried on a non-sticking plate.
In a commentary, published in the same journal, University of Michigan chemical engineer Joerg Lahann questioned whether the membrane would be used commercially, given the cost - and possible toxicity - of manganese oxide.
"Even so, it clearly provides a blueprint that can guide the design of future nanomaterials for environmental applications," Lahann said. "Many other examples are expected to follow and will confirm the potential of nanomaterials for protecting the environment."
On May 5, French-led technologists said they had beefed up the performance of a nano-powder that stores carbon dioxide (CO2), in a step towards creating a filter to catch greenhouse gases from vehicle exhausts.
A cubic metre of the new substance, called MIL-101, is able to capture 400 cubic metres of CO2, thanks to pores 3.5 nanometres (billionths of a metre) across, according to the National Centre for Scientific Research (CNRS).
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