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Environment

Membrane Unmixes Oil And Water

Hydrophilic-oleophobic combo could clean up oil spills, treat wastewater, purify fuels, separate emulsions

by Stephen K. Ritter
December 24, 2012 | APPEARED IN VOLUME 90, ISSUE 52

[+]Enlarge
Credit: Nat. Commun.
Water (blue) readily wets the surface and rapeseed oil (red) beads up on two versions of a hydrophilic-oleophobic membrane: stainless steel (top) and polyester (bottom).
09052-cover2-Dropletscxd.jpg
Credit: Nat. Commun.
Water (blue) readily wets the surface and rapeseed oil (red) beads up on two versions of a hydrophilic-oleophobic membrane: stainless steel (top) and polyester (bottom).
[+]Enlarge
Credit: Nat. Commun.
These AFM images of a hydrophilic-oleophobic membrane show that the dry surface is covered with crystalline regions of polymer and fluorinated silsesquioxane (left). But when wet with water, the surface reconfigures and becomes smooth, allowing water to pass through.
09052-cover2-Imagescxd.jpg
Credit: Nat. Commun.
These AFM images of a hydrophilic-oleophobic membrane show that the dry surface is covered with crystalline regions of polymer and fluorinated silsesquioxane (left). But when wet with water, the surface reconfigures and becomes smooth, allowing water to pass through.
SUPERMEMBRANE SPLITS UP OIL AND WATER
Even though oil and water don’t mix, when they do come together, as in oil spills, they’re difficult to separate. Researchers at the University of Michigan and the Air Force Research Lab developed a membrane that separates the substances with ease, via gravity filtration. In this clip, watch the membrane in action and learn about the materials it’s made from.
Credit: University of Michigan/C&EN/YouTube

Oil and water usually don’t mix, but when the two end up together, say in an oil spill or in an emulsion, they can be nearly impossible to completely separate. However, by combining a water-loving polymer with an oil-repelling silicon-based material, researchers this year created a new breed of membrane that efficiently separates bulk amounts of any type of oil-water mixture by simple gravity filtration. A team including Arun K. Kota and Anish Tuteja of the University of Michigan and Joseph M. Mabry of the Air Force Research Laboratory devised membranes that sidestep typical membrane limitations—fouling by viscous materials and the energy cost of pumping liquids through the membrane—by dipping polyester fabric or stainless steel mesh in a mixture of cross-linked polyethylene glycol diacrylate, which is hydrophilic, and a fluorinated polyhedral oligomeric silsesquioxane, which is oleophobic (C&EN, Sept. 3, page 9; Nat. Commun., DOI: 10.1038/ncomms2027). When an oil-water mixture or emulsion is poured onto one of the membranes, microcrystalline regions reconfigure to form a smooth, noncrystalline surface that allows the polymer to hydrogen bond with water. Water then flows unimpeded through the membrane, which holds back the oil and is resistant to fouling. The researchers envision the membranes being used not only to clean up oil spills but also to treat wastewater, purify fuels, and separate emulsions used in manufacturing processes. Since the discovery was announced in August, Tuteja says the research team has been approached by three dozen companies with interest in buying membranes or licensing the technology.

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Comments
BL (November 26, 2013 11:38 AM)
The "emulsion" shown in the video was not an emulsion! It was two phase separated liquids.
Steve Ritter (March 1, 2016 9:50 AM)
Membrane Update: The Tuteja group is commercializing the coating for different membranes through a startup called HygraTek (www.hygratek.com). The cost of the coating, which can be applied on top of virtually any existing membrane, is now only about $1 per square foot of the membrane area. The total cost of the coated membrane depends on the material being coated, which can be inexpensive for filter paper or quite expensive for ceramic membranes.

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