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Superoleophobic yet Superhydrophilic surfaces for Continuous Liquid-Liquid Separation
Final rept. 15 Sep 2010-14 Sep 2011
MICHIGAN UNIV ANN ARBOR DEPT OF MATERIALS SCIENCE AND ENGINEERING
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There is a critical need to develop new energy-efficient solutions for the separation of oil-water mixtures, including those stabilized by surfactants. Traditional membrane-based separation technologies for oil-water mixtures are energy-intensive and further limited, either by fouling or the inability of a single membrane to separate all types of oil-water mixtures. The ideal membrane to effect gravity-driven separation of oil-water mixtures is expected to be both hydrophilic and oleophobic, in air and when submerged under water. Such membranes would allow the higher density liquid water to flow through, while retaining the lower density liquid oil. However, as water possesses a significantly higher surface tension than various oils, most membranes that prevent the permeation of oils, also prevent the permeation of water. In this work we report the first-ever reconfigurable membranes that, counter-intuitively, are both superhydrophilic i.e., water contact angles 0 and superoleophobic i.e., oil contact angles 150 . These membranes were designed through the systematic tailoring of membrane porosity and the membrane-water interfacial energy. The developed fouling-resistant membranes are able to separate all types of oil-water mixtures, with 99 separation efficiency, using a single membrane. Further, we have engineered the first-ever apparatus for continuous, solely gravity-driven separation of surfactant-stabilized oil-water emulsions, with a separation efficiency greater or equal to 99.9.
APPROVED FOR PUBLIC RELEASE