Researchers at the Massachusetts Institute of Technology, US, have devised a new technique for magnetically separating oil and water by mixing water-repellent ferrous nanoparticles with the oil before extraction.

While previous research has focussed on separating water and these so-called ferrofluids, these typically involve pumping a water and ferrofluid mixture through a channel. Magnets outside the channel then direct the flow of the ferrofluid either through a side channel or perforated wall.

This approach can work if the concentration of the ferrofluid is known in advance and remains constant, but in water contaminated by an oil spill the concentration can vary widely.

The MIT researchers have overcome this by immersing the magnets in the stream and orientating them perpendicularly to its flow.

This technique provides excellent separation, they claim, and has the potential to be manufactured on a large scale and deployed at sea for days or weeks, where electrical power is scarce and maintenance facilities limited.

On a commercial scale, they add, it could make sense for an oil-recovery vessel to perform an initial separation of oil and water and then haul the oil ashore for further refinement.

Maxine Perella

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