Dehydration and Permeation of Various Aqueous-Organic and Organic-Organic Mixtures Using a Perfluorinated Polymeric Membrane in Pervaporation

Previous studies utilizing a perfluorinated membrane, known as CMS-3, in dehydration of aprotic solvents by pervaporation have demonstrated significantly large separation factors on the order of 1,000-12,000 for water over a variety of aprotic solvents [1]. Using the same membrane material, additional dehydration studies were performed on systems containing ethylene glycol-water and acetone-butanol-ethanol-water.  The perfluorinated membrane was able to achieve similar separation factors, approximately 12,800, for water over ethylene glycol at 30°C using a feed containing 30 wt% water.  For a membrane of thickness 25 µm, water flux varied as a function of water concentration between 13 to 24 g/(m²-h). Separation of acetone-butanol-ethanol-water systems containing 10 wt% water yielded results that correlate towards molecular size exclusion. Separation factors of water over organic solvents were 336, 1,075, and 5,300 for acetone, ethanol and n-butanol respectively. Water flux in these systems for the 25 µm membrane  ranged from 27 to 33 g/(m²-h) as the temperature was increased from 30 to 50°C. This agrees with previous results in which a relationship has been seen between the overall permeability coefficient and the longest molecular diameter for the permeation of a variety of pure organic solvents.

[1] Tang, J., Sirkar, K.K., “Perfluoropolymer membrane behaves like a zeolite membrane in the dehydration of aprotic solvents”, J. Membr. Sci. 421 – 422 (2012) 211 – 216.