Shaking Nanomaterials out of Water

Shaking the Nanomaterials Out: New Method to Purify Water

Nano implies small—and that’s great for use in medical devices, beauty products and smartphones—but it’s also a problem. The tiny nanoparticles, nanowires, nanotubes and other nanomaterials that make up our technology eventually find their way into water. The Environmental Protection Agency says more 1,300 commercial products use some kind of nanomaterial. And we just don’t know the full impact on health and the environment.

“Look at plastic,” says Yoke Khin Yap, a professor of physics at Michigan Technological University. “These materials changed the world over the past decades—but can we clean up all the plastic in the ocean? We struggle to clean up meter-scale plastics, so what happens when we need to clean on the nano-scale?”

That challenge is the focus of a new study co-authored by Yap, recently published in the American Chemical Society’s journal Applied Materials and Interfaces. Yap and his team found a novel—and very simple—way to remove nearly 100 percent of nanomaterials from water.

The method sounds like a salad dressing recipe: take water, sprinkle in nanomaterials, add oil and shake.

Dongyan Zhang, a research professor of physics at Michigan Tech, led the experiments, which covered tests on carbon nanotubes, graphene, boron nitride nanotubes, boron nitride nanosheets and zinc oxide nanowires. Those are used in everything from carbon fiber golf clubs to sunscreen.

“These materials are very, very tiny, and that means if you try to remove them and clean them out of contaminated water, that it’s quite difficult,” Zhang says, adding that techniques like filter paper or meshes often don’t work.

What makes shaking work is the shape of one- and two-dimensional nanomaterials. As the oil and water separate after some rigorous shaking, the wires, tubes and sheets settle at the bottom of the oil, just above the water. The oils trap them. However, zero-dimensional nanomaterials, such as nanospheres do not get trapped.

Source: Michigan Tech News

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