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.
The technology might be used in a water-purification technology called reverse osmosis, which now requires a "pre-filter" to remove oil. This "oil coalescence filter" is needed to prevent oil from reaching the reverse osmosis membrane, which is ruined by oil. These conventional oil coalescence filters, however, must be replaced regularly. As water flows through the system, oil sticks to the filters, eventually rendering them ineffective.
The new technology, 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.
"When the oil-in-water dispersion contacts the filter surface, the oil coalesces to form big droplets. If the mixture is poured onto the filter, the oil forms on top of the material like a layer of cream," Youngblood said.
When a fluid lands on the surface of the material, it forms beads having a distinctive curvature determined by the "contact angle" of the substance. The higher the contact angle, the more a material is likely to form beads. Lowering the contact angle enough prevents substances from beading.
"This material maximizes oil's contact angle while minimizing water's contact angle, allowing water to flow through a filter while holding back the beaded oil," Youngblood said.
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.
"One big problem is that if you are forcing stuff through very small pores it takes a lot of pressure," Y
|Contact: Emil Venere|