Smart filter strains oil out of water

Researchers at Michigan University have developed a smart filter with a shape-shifting surface that uses gravity to separate oil and water.

They hope the material can be used to provide a more efficient way to remove crude oil from waterways without using additional chemical detergents.

Most natural substances soak up oil, and the few that repel it also repel water because water has a higher surface tension.

“Our material operates in a counterintuitive way,” said Anish Tuteja, an assistant professor of materials science and engineering.

This is one of the cheapest and most energy efficient ways to separate oil and water mixtures

“Water spreads on its surface, while the oil beads up. It’s hydrophilic, so it loves water, and oleophobic, so it hates oil.”

In their experiments, the researchers dipped postage-stamp-size pieces of stainless steel window screen and polyester fabric into their solution.

Then they cured the coated snippets under ultraviolet light. Meanwhile, they made four different types of oil/water mixtures, including emulsions with various ratios of water and canola oil.

When the researchers passed the mixtures through the coated filters, they found that with 99.9 percent efficiency, they could separate free oil and water, oil-in-water emulsions, water-in-oil emulsions, and any combination of these blends.

“This is one of the cheapest and most energy efficient ways to separate oil and water mixtures,” Tuteja said. “It has never been demonstrated before.”

“We’ve shown that, even when you add surfactants and dispersants to the mixture, as was done in the Deepwater Horizon oil spill, we can efficiently separate the oil from the water.”

Tuteja says these results were at first surprising, and they’re possible because of a particularly useful property of the new coating.

When it is exposed to water, the polymer and the nanoparticle components scamper into a different configuration, one that encourages the water molecules to bond with the polymer.

“The polymer, in essence, reaches up during surface reconfiguration through the filter and wicks more water across, while the oil remains above the filter,” said Arun Kota, a postdoctoral researcher.

They were able to use their coated filters for more than 100 hours without clogging, a vast improvement over today’s technology.

In addition to oil-spill clean-up, the technology could be used in wastewater treatment, oil purification for fuel applications, and in the cosmetics industry.