GAS PERMEATION IN POLYCARBONATE MEMBRANES PREPARED BY THE WET-PHASE INVERSION METHOD

Polycarbonate (PC) membranes prepared by the wet-phase inversion process was investigated in the present study. Varying amounts of a non-solvent (methanol) were added to the casting solution during membrane preparation and was found to increase significantly membrane porosity. The gas permeability of the PC membranes was increased from 1.68 and 0.26 barrers, respectively, for oxygen and nitrogen without the non-solvent, to 35.1 and 3.86 barrers with 3 ml of the nonsolvent added. The drastic increase in gas permeability was accompanied by only a slight decrease in selectivity. Hence, the PC membranes prepared with addition of methanol have a great potential for industrial oxygen enrichment applications. A simple gas diffusion model with an effective gas diffusion coefficient was found to describe reasonably well the gas permeation process. The estimated effective gas diffusion coefficient can closely reflect the increase in gas permeability of the membranes due to the addition of methanol.