In the wake of the Gulf of Mexico oil spill we explored several innovative methods to separate oil from water. Now a team from MIT has developed a new technique for magnetically separating oil and water that could be used to clean up oil spills in the future. The method is said to be so efficient that the recovered oil can even be reused to offset the cost of the clean-up.
The MIT team consists of Shahriar Khushrushahi (a postdoc in MIT’s Department of Electrical Engineering and Computer Science), Markus Zahn (the Thomas and Gerd Perkins Professor of Electrical Engineering) and T. Alan Hatton (the Ralph Landau Professor of Chemical Engineering). During their research, they used water-repellent ferrous nanoparticles mixed in with the oil, in order to separate it later with magnets. The amazing part is that once the nanoparticles are magnetically removed from the oil, they can then be reused.
“There’s a good deal of previous research on separating water and so-called ferrofluids — fluids with magnetic nanoparticles suspended in them,” said Zahn. “Typically, these involve pumping a water-and-ferrofluid mixture through a channel, while magnets outside the channel direct the flow of the ferrofluid, perhaps diverting it down a side channel or pulling it through a 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. Suppose that the separation system consists of a branching channel with magnets along one side. If the oil concentration were zero, the water would naturally flow down both branches. By the same token, if the oil concentration is low, a lot of the water will end up flowing down the branch intended for the oil; if the oil concentration is high, a lot of the oil will end up flowing down the branch intended for the water.”
While it may sound simple, the method is highly effective at separating oil from water. The team also believe that it can be implemented on a larger 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.”