Surprisingly Simple and Effective Method for Separating Oil and Water

Researchers at the Massachusetts Institute of Technology (USA) have developed a new way of magnetically separating oil and water. They believe that this technique could be used to clean up oil spills and even be so effective that the oil can be recovered and still used.

The work will be presented at the International Conference on Magnetic Fluids in January. Shahriar Khushrushahi, a postdoc in MIT’s Department of Electrical Engineering and Computer Science, is lead author on the paper, joined by Markus Zahn, the Thomas and Gerd Perkins Professor of Electrical Engineering, and T. Alan Hatton, the Ralph Landau Professor of Chemical Engineering. The team has also filed two patents on its work.

The idea of this technique is that water-repellent ferrous nanoparticles would be mixed in with the oil. This would then help to separate the oil from the water using magnets. The nanoparticles would be mixed in aboard an oil-recovery vessel in order to protect the environment. Afterwards, the nanoparticles could then be magnetically removed from the oil and reused.

The design is simple, but it provides excellent separation between oil and water. Moreover, Khushrushahi says, simplicity is an advantage in a system that needs to be manufactured on a large scale and deployed at sea for days or weeks, where electrical power is scarce and maintenance facilities limited. “The process may seem simple,” he says, “but it is, inherently, supposed to be simple.”

In their experiments, the MIT researchers used a special configuration of magnets, called a Halbach array, to extract the oil from the tops of the cylindrical magnets. When attached to the cylinders, the Halbach array looks kind of like a model-train boxcar mounted on pilings. The magnets in a Halbach array are arranged so that on one side of the array, the magnetic field is close to zero, but on the other side, it’s roughly doubled. In the researchers’ experiments, the oil in the reservoir wasn’t attracted to the bottom of the array, but the top of the array pulled the oil off of the cylindrical magnets.