Oil from water

US engineers at Purdue University have created a new type of membrane that separates oil from water.

The amphiphilic membrane consists of a layer of polyethylene glycol tipped with a Teflon-like functional group made with fluorine.

Water molecules are attracted to the polyethylene glycol, yet pass through the Teflon-like layer, which acts as a barrier to the oil molecules.

Researchers attached the material to a glass filter, commonly used in laboratory research, to test out its effectiveness.

Taking mixtures of oil dispersed in water and running them through the filters, they found that they could achieve 98 per cent separation.

Jeffrey Youngblood, an assistant professor of materials engineering at PurdueUniversity, said: ‘To clean up an oil spill, for example, you could run contaminated water through a bunch of these filters to remove the oil.’

Such filters also might be used in other cleanup applications, such as removing oil from a ship’s bilge water or cleaning wastewater contaminated with oil.

They might also be used in reverse osmosis water-purification systems, which require an oil coalescence filter to prevent oil from reaching a reverse osmosis membrane, which would be ruined by the oil. 

Today such filters must be replaced regularly, because as water flows through the system, oil sticks to them, eventually rendering them ineffective.

The new filters, however, would not need to be replaced as frequently because oil does not stick to the filtration material.

Instead the oil droplets could be skimmed off through a commonly used industry technique called cross-flow filtration.

Another advantage of the new approach is that it separates oil from water without using ‘nanoporous’ filters.

Such filters contain extremely small pores and require water to be pushed through them at high pressure, consuming energy.

The new material, on the other hand, contains pores between 10 and 174 microns, or millionths of a metre.

Because the pores are relatively large, oil-contaminated water would not have to be pumped through.

Future work will involve finding a substitute for the glass filters, which, the researchers say, are not practical for commercial membranes.