Gas Permeation Characteristics of Dried Asymmetric Cellulose Acetate Membranes by Alcohol Exchange Treatment

Abstract

Asymmetric cellulose acetate reverse osmosis membranes were vacuum dried at ambient temperature, after being soaked in alcohols such as methanol, ethanol (EtOH) and isopropanol (i-PrOH) to replace water in the membrane.
The dried membrane was characterized by permeabilities of He, CH₄, N₂ and CO₂, and separation factor of equi-molar mixture of CH₄ and CO₂.
Shortening the evaporation time of acetone results in an increase of permeability. Dried membranes which were heat treated less than 80°C did not virtually permeate gases. Treatment by mixtures of EtOH and i-PrOH gives the best dried membranes among the tested; as for separation factor, mixing ratio of EtOH and i-PrOH as 1 : 3 gives the best; as for permeability, as 1 : 1.