At the University of Michigan, materials scientists have developed a smart filter that can remove 99.9 percent of oil from water using gravity. The researchers reported their findings in the August 28 edition of Nature Communications.
The recently developed global health index for ranking the world’s oceans returned a sobering conclusion: Globally, our oceans received the failing grade of sixty out of one hundred. Pollution is a major culprit for the low marks, underscoring the importance for effective ways to clean up.
The new material promises to help. Created in collaboration with the Air Force Research Laboratory, the filter is unconventional and counterintuitive, says Anish Tuteja, co-author of the recent paper and assistant professor at the University of Michigan. It’s hydrophilic and oleophobic, meaning it loves water and hates oil, which puts it at odds with most known surfaces.
To illustrate its contrasting properties, Tuteja gives the example of Teflon: “If you think of a non-stick cooking pan coated with Teflon, water beads up on that surface. But a cooking oil will always spread on it.”
The new filter does the opposite: It allows water to soak through, while oil beads up and remains on the surface.
A low-cost, low-energy solution for cleaning up oil spills.
To create the material, the researchers used a commercially available water-loving polymer blended with a new, low surface energy, oil-repelling nanoparticle. This resulted in a material that, when oil and water mixtures are placed above it, allows only water to pass through.
“The reason we wanted to use gravity to separate oil and water is because water is always at the bottom, and oil floats on top. We wanted the water to be able to easily filter through the membrane,” says Tuteja.
Because gravity is used to filter the water, no additional chemicals or high-pressure sources are needed. The filter can be used for over 100 hours without clogging, and may prove to be a low-cost, low-energy solution for cleaning up oil spills.
Tuteja sees the material being used to clean oil spills in one of two ways. Either the entire spill could be collected and then filtered, or the material could hang on the side of boats, skimming the surface and continuously filtering the oil from water.
Outside of oil spill cleanups, Tuteja believes the filter could be used in a variety of industries, including waste-water treatment, cosmetics, and any chemical industry. You can see the material in action in the video below:
Top image courtesy Laura Rudich.