A New Kind of Membrane for Separation Processes: The Hydrophobic-Hydrophilic Membranes (Expedited Award for Novel Research)
Eli Ruckenstein Principal Investigator
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The proposed process would allow design of a membrane for a specific liquid separation. Monomers of two immiscible polymers are dispersed in one another with a surfactant (probably a block copolymer). A very high dispersed-phase mole fraction is used, so that a gel-like consistence is obtained. The gel is then pressed between glass plates and polymerized. The result is a thin membrane with separate, ordered domains, some hydrophobic and some hydrophilic. The monomers are also selected so that the component to be separated from the liquid mixture is highly soluble in the polymer phase which was dispersed in the membrane. The polymer in which the target compound is not soluble gives the liquid membrane structural integrity, while the polymer produced from the dispersed phase monomer has a very high permeability for that compound. The membrane is kept from disintegrating, as it becomes saturated with the solute to be removed from the solution, by the polymer making up the continuous phase of the original dispersion. An example of a potential application is ground water cleanup, such as the removal of benzene from a contaminated aquifer. One would use styrene as the dispersed phase to produce polystyrene, which is highly soluble in benzene. The continuous phase monomer would be very hydrophilic, such as n-vinyl pyrrolidone. The poly-n-vinyl-pyrrolidone would prevent the polystyrene domains from losing structural integrity as they became saturated with benzene, but the flux of benzene through the polystyrene domains should be very high. Many other potentially important separations can be imagined, such as the separation of ethanol from water. If this process is successful, it will constitute a major advance in an important emerging engineering technology.