Membrane Unmixes Oil And Water

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.