Researchers at the Massachusetts Institute of Technology (MIT) have developed a method of magnetically separating water and oil, which could help clean up oil spills. Their new technique would also, the researchers believe, recover the oil in such a way as to leave it reusable, which could help offset cleanup costs.

This research fits into a larger body of study on magnetic fluids, as the technique hinges upon essentially magnetising oil by infusing it with ferrous nanoparticles, which can then be separated from water. These water-repellent ferrous nanoparticles would be mixed with oil, and then magnets would be used to attract the oil and separate it from the water. The researchers anticipate that the process would take place aboard oil-recovery vessels, so the nanoparticles would not contaminate the environment and could be recovered.

Relative to the tremendous complexity of cleaning up an oil spill, the design put forward by these MIT researchers is simple. Shahriar Khushrushahi, a postdoctoral student in MIT's department of Electrical Engineering and Computer Science, and the lead author on the research paper, emphasises that simplicity is a huge advantage when cleaning up an oil spill, as vessels are deployed at sea for days or weeks, electrical power is scarce and maintenance facilities are limited.

"The process may seem simple", he said, "but it is, inherently, supposed to be simple."

How it works

In experiments conducted by the MIT researchers, they embedded a cylindrical magnet into the bottom of a reservoir filled with water and magnetised oil, with the top of the magnet above water level. With this orientation, the magnetised oil collected around the magnet's ends.

To extract oil from the ends of the magnets, the MIT researchers used a configuration of magnets called a Halbach array, which has a magnetic field close to zero at one end, but a nearly doubled on at the other end, meaning all the magnetised oil was attracted to one side of the array.

What's next

The researchers at MIT will present their work at the International Conference on Magnetic Fluids in January. The team is comprised of Khushrushahi, the lead author; Markus Zahn, Thomas and Gerd Perkins Professor of Electrical Engineering; and T. Alan Hatton, the Ralph Landau Professor of Chemical Engineering. They have also filed two patents on their work.

For more information on cleaning up oil spills, see ‘Beyond Petroleum: The hidden wastes of oil spills’.