Thermodynamic and mechanistic characterization of water sorption in homogeneous and asymmetric cellulose acetate membranes

The water sorption isotherms for homogeneous and asymmetric cellulose acetate membranes have been measured at different temperatures. Subtle differences between the water sorption isotherms for asymmetric and homogeneous membranes have been interpreted by suggesting that capillary condensation contributes significantly to sorption in asymmetric membranes at high activities and also to an intriguing excess sorption observed in homogeneous membranes at intermediate activities. This model has been supported by the experimentally determined values of the enthalpy and entropy changes associated with sorption