The effects of carbon dioxide conditioning on the permeation behavior of hollow fiber asymmetric membranes

Abstract

Asymmetric hollow fiber membrane modules conditioned with 125 psig CO 2 are shown to have significantly enhanced air permeation rates as compared to their unconditioned values. Permeation increases as great as 100% are reported for modules conditioned for 48 hr with CO 2. The conditioning treatment has negligible effect on the O 2/N 2 selectivity. The permeation enhancement is permanent as long as air remains in contact with the module, but is slowly lost when the module is depressurized. Neither air nor helium were able to induce the conditioning response but were able to maintain the module in a state of enhanced permeability as long as they remained in contact with the module. The permeation enhancement observed for air following CO 2 conditioning treatments is much greater in asymmetric modules than in dense films composed of the same polymer. It is proposed that the difference between the dense film and hollow fiber module conditioning results are due primarily to alterations in the supermolecular morphology of the asymmetric membranes.