Preparation and characterization of asymmetric polysulfone membrane for separation of oxygen and nitrogen gases

Defect‐free skinned asymmetric gas separation membranes were prepared by a dual bath coagulation method using a wet phase inversion technique. The membranes were cast from polysulfone solution in different solvents such as: dimethyl‐formamid, 1‐methyl‐2‐pyrrolidone, N‐N‐dimethyl‐acetamide (DMAC), and tetrahydrofuran. The mixtures of water/iso‐propanol (IPA), water/propanol, water/ethanol (EtOH), and water/methanol (MeOH) with volume ratio of 80/20 were used as the first coagulation bath. This led to the formation of a dense skin top layer. Distillated water was used as the second coagulation bath. The influences of several experimental variables, such as thickness of the membrane, polymer concentration, type of solvent and nonsolvent, immersion time in IPA 20%, and second coagulation bath temperature on skin layer and sublayer were elucidated. For preparing membrane with higher permeance, the influence of internal nonsolvents and addition of polyvinylpyrrolidone (PVP) as additive were investigated. The membrane performance was tested in terms of gas permeance and selectivity for O₂/N₂ separation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011