Power sucker: Like kitchen towel on steroids, the nanowire mesh can absorb twenty times its own weight in oil. The image shows a close-up of entwined bundles of wires.
Credit: MIT
SYDNEY: Devastating oil spills may one day be mitigated by a paper-thin nanomembrane, which has an incredible affinity for oil, and can soak up 20 times its own weight.
An estimated 200,000 tonnes of oil have been spewed into marine environments in accidents since the year 2000 alone, so effective technologies for mopping it up are much sought after.
"There are many materials able to absorb oil preferentially from water, but none have the ability to be as fully discriminating as this one," said Francesco Stellacci, lead researcher behind the technology at the Massachusetts Institute of Technology, in Cambridge, USA.
Miniature mesh
In a paper published today in the U.K. journal Nature Nanotechnology Stellaci and his team describe the membrane which is made up of a mesh of tiny nanoscale wires which soak up oil and repel water.
These tiny potassium-treated, manganese oxide wires are just 20 nanometres in diameter – not much bigger than a strand of DNA. Stellaci's team have developed a process for entwining the wires in a mesh to make sheets that are around 30 centimetres wide, but just 50 micrometres thick. The surface is then coated with a substance that repels water, causing droplets to roll off.
Stellaci said the nanostructure consists mainly of air, so there's plenty of room inside it. As it draws oil in, the oil replaces the air in the structure. In this way, the nanostructure can hold up to 20 times its own weight in oil.
The membrane can also be used to mop up oil-soluble pollutants in water, and it's environmentally friendly in its own right, being easily recyclable. Heating it to 130 ºC returns it to its previous state and causes the absorbed oil to evaporate.
Environmental nanomaterials
"This material could potentially be effective in the cleaning of oil spills in the ocean and also in helping with the purification of contaminated water," said Stellaci. "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 [oil-soluble] contaminants, they will get absorbed."
In an accompanying commentary in the same issue of Nature Nanotechnology, chemical engineer Joerg Lahann, said the nanostructure's accuracy at sifting oil from water is remarkable as is the amount of oil it can hold. This "clearly provides a blueprint that can guide the design of future nanomaterials for environmental applications," he said.
However, Lahann, of the University of Michigan in Ann Arbor, U.S., also said that "owing to potential economic and toxicological arguments about the use of manganese oxide, it is difficult to predict whether this specific membrane will find commercial use."
Membrane
20 times it's own weight is nothing. To mop the crap that is being spilled onto the land these days in the active gas drilling areas of TEXAS would require thousands of times it's own weight and then how much land would be required to covered??