Emulsion Pathways to Composite Polymeric Membranes for Separation Processes
Eli Ruckenstein Principal Investigator
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In this project the investigator proposes a systematic evaluation of a new-type of membrane to be used in separations processes. The principal novel aspect of the proposed work is formation of the membrane by polymerization of two monomers, mutually insoluble, one dispersed inside the other, after the dispersion has been pressed between glass plates. When very high volume fractions of the dispersed phase monomer are used the emulsion consists of polyhedra of the dispersed phase monomer separated by thin lamella of the continuous phase monomer. The principal application which is to be made of this new type membrane is to separate one solvent from its solution in another solvent, though other applications are certainly possible. The dispersed polymer is chosen so that it is readily soluble in the solvent one wishes to remove from a mixture of solvents, but is insoluble in the solvent one wishes to retain. The continuous phase polymer, however, is insoluble in both solvents. The very thin lamella of the continuous phase offer a very low mass transfer resistance. The dispersed phase polymer, once saturated in the solvent to be removed, gives both high selectivity and liquid-like diffusion coefficients, so that very high fluxes should be obtainable. Two examples have been presented. In one, toluene is separated from cyclohexane using a membrane with polystyrene as the polymerized dispersed phase and polyacrylamide as the polymerized continuous phase. In the second, water is separated from ethanol using a composite membrane in which polyacrylamide is the polymerized dispersed phase and polystyrene is the polymerized continuous phase. In both examples the new membranes give fluxes and separation factors comparable to the best that has been achieved with any other type of membrane. This is highly novel and innovative work with great potential for introducing a whole new generation of membranes.