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Pervaporation Membranes Highly Selective for Solvents Produced by Fermentation

Atsawin Thongsukmak and Kamalesh K. Sirkar. Chemical Engineering, New Jersey Institute of Technology, Membrane Seperations, 161 Warren st, Newark, NJ 07102

Pervaporation is one of the promising techniques for separation and recovery of volatile fermentation byproducts present at low concentrations. Although polymeric rubbery membranes are quite successful in removing most volatile organic compounds (VOCs) from their dilute solutions in water, their selecitivies for removing polar organic compounds are not very high. Previous studies indicated that liquid membranes can achieve much higher selectivity for some small molecules such as acetic acid, ethanol, butanol, etc. In the current work, we have focused on liquid membranes immobilized in novel porous hollow fiber-based membranes as a support for the pervaporation process to increase the VOC selectivity and membrane stability. Volatile fermentation byproducts such as acetone, butanol and ethanol present in low concentrations in synthetic aqueous solutions have been separated by novel liquid membranes. We have tested the liquid membrane with model solutions (containing acetone-butanol-ethanol (ABE)) as well as a filtered solution from a fermentation broth (from ABE fermentation) by the pervaporation process. Very high selectivity for the solvents were obtained in the permeate especially at higher feed temperatures > 50C; high stability of liquid membrane was also observed. Fluxes and selectivities of solvents were studied over a range of temperatures ; higher temperature yielded much higher selectivities.