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segunda-feira, 14 de dezembro de 2015

Nanomaterial with the potential to mop up giant oil spills

A common cosmetics ingredient is being developed into a nano-material with the potential to mop up giant oil spills. Viviane Richter explains. 
When BP’s Deepwater Horizon oil rig exploded in 2010 it dumped more than 300 Olympic swimming pools of oil into the Gulf of Mexico. Cleaning up a massive spill involves burning off the oil, or using chemicals to break up the slick and disperse it through the oceans.
A new material made from a common cosmetics ingredient could pick up the oil and remove it from the sea, much like blotting up a kitchen spill with a paper towel. The material was described by a team led by nanotechnologist Ian Chen of Deakin University in Geelong in Nature Communications in November.
Chen’s material is made from sheets of boron nitride, or “white graphite”, which is used in cosmetics to stop powders clumping and to soak up oils on skin.
Chen's oil-absorbent sheets (left) are stable at high temperatures (right).CREDIT: IAN CHEN, DEAKIN UNIVERSITY
“[The new sheets] will change the way people utilise boron nitride,” says David Officer, organic chemist at the University of Wollongong.
At the nano-level, boron nitride consists of single-atom-thick layers, stacked like pages in a newspaper. Ordinarily only the outermost layers trap oil, limiting the material's absorptive capacity.
The team has boosted that capacity by separating the boron nitride layers, scrunching them up, and then reassembling them into sheets that can be thrown over floating oil.
The boron nitride is first treated with urea to separate the layers, and the solution is  shredded through an industrial grinder. The torn and separated boron nitride layers pucker and join as they dry, forming sheets five times thinner than a piece of paper. So far Chen has produced sheets the size of a post-it note, but with a huge surface area for sopping up oil. A single gram of the sheets, spread out flat, would cover five tennis courts.
Dark and light brown crude oil from the Deepwater Horizon rig floats on the surface of the Gulf of Mexico. Chemical dispersants used to treat the oil spill are also damaging to the environment.CREDIT: KRIS KRÜG/GETTY IMAGES
What’s more, the sheets are stable to 800°C, raising the possibility that oil could be burnt off in furnaces and the material used again. This gives it an advantage over another candidate material: raw cotton. Cotton can mop up to 36 times its own weight in oil, but once used it has to be tossed. Another promising candidate, graphene – a chemical cousin of boron nitrate – absorbs up to 86 times its weight in oil but is less stable at high temperature, limiting its reuse.
And even though the Chen team is still testing the absorption power of the boron nitride sheets, the method has already mopped up interest from industry – a textile company is working with Chen to find ways to produce much larger films.
Officer is optimistic this can be done. “[The sheets] are an excellent material for fabrication,” he says.
Viviane Richter is a staff writer at COSMOS.

Fonte: Cosmos