Filtering May Have Environmental, Industrial Applications

Materials engineers have created a new type of membrane that separates oil from water and, if perfected, might be used for environmental cleanup, water purification, and industrial applications.

The new technology would last longer than conventional filters for separating oil from water and works by attracting water while beading oil, traits that are usually mutually exclusive. Researchers attached the material to a glass filter commonly used in laboratory research.

“We take mixtures of oil dispersed in water and run them through these filters, and we are getting 98 percent separation,” says Jeffrey Youngblood, an assistant professor of materials engineering. “This is pretty good, because if you don’t modify the glass filters with our material, essentially all the oil goes through. If you modify them with our material, then almost none of the oil goes through.”

Polyethylene being tested

The membrane consists of a layer of material called polyethylene glycol, and each molecule is 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. The researchers have tested the material with solutions containing oil suspended in water, similar to concentrations existing in oil spills and other environmental cleanup circumstances.

A key advantage of the new approach over some conventional methods is that it separates oil from water without using “nanoporous” filters. Filters containing extremely small pores require the water to be pushed through at high pressure, which consumes energy.

Such filters also might be used in cleanup applications, such as removing oil from a ship’s bilge water or cleaning wastewater contaminated with oil. They could also be applied to water-purification technology called reverse osmosis, which now requires a “prefilter” to remove oil.