(66f) Novel Pervaporation Membranes for Separation of Solvent/Water Mixtures

Traditionally, the pervaporation of miscible solvent/water where the solvent is the major component is performed using hydrophilic membranes (such as PVA or zeolites). In the present paper, a new type of pervaporation membrane (primarily amorphous perfluoropolymers, hydrophobic) was studied for separation of solvent/water mixtures. This membrane has high free volume and is inert for all solvents, and has a remarkable mechanical, chemical and thermal stability. The water is transported by solution diffusion model and the separation in solvent is primarily based on molecular sieving (size exclusion) principles. The membrane shows a high stability for operation over a broad range of feed concentration without swelling; the operating temperature does not have a significant effect on membrane selectivity. Water selectivities as high as 349 and 500 for ethanol/water and IPA/water mixtures (98/2 %wt solvent/water) and fluxes of 0.15 and 0.05 kg/m²h, respectively, were obtained at 22°C. The pervaporation of more complex (ternary) mixtures of ethanol-ethyl acetate-water showed that this system could be successfully applied for solute separation based on complete size exclusion of ethyl acetate. This research has been funded by a NIH-SBIR program subcontract to the University of Kentucky.