Preparation of asymmetric polyimide membrane for water/ethanol separation in pervaporation by the phase inversion process

Abstract The preparation of polyimide pervaporation membranes for the separation of aqueous ethanol solutions was investigated. Asymmetric membranes were prepared by the phase inversion process from casting solutions composed of aromatic polyimide (PI-2080), N,N′ -dimethylformamide (DMF) and 1,4-dioxane. The membranes were annealed at 300°C in a vacuum oven and were measured at 25°C for an aqueous 95 vol% ethanol solution in pervaporation. Membranes made from a casting solution composed of 25 wt% polyimide, 37.5 wt% DMF and 37.5 wt% dioxane, showed a molecular weight cut-off of 600. The membranes which were annealed at 300°C for 3 h exhibited a separation factor α(H 2 O/EtOH)=900 with a flux of 1.0 kg/m 2 h for an aqueous 95 vol% ethanol solution at 60°C.