Parametric Study of CO2 Fixed Carrier Facilitated Transport through Swollen Chitosan Membranes

Swollen and dry chitosan membranes were used to separate carbon dioxide from a feed gas composed of 10% CO 2, 10% H 2, and 80% N 2 in a temperature range of 20−150 °C for a feed pressure of 1.5 atm. Swelling increased CO 2 permeabilities (barrers) of chitosan membranes from 0.381 to 213 at 20 °C, 9.50 to 482 at 110 °C, and 26.1 to 399 at 150 °C, accompanied with similar trends for the separation factors: CO 2 /H 2 and CO 2 /N 2 . The total water levels of the membranes were controlled to be the same at all temperature conditions by manipulating the relative humidities of the feed and sweep gases. This permitted direct comparison of the levels of bound and free water to carbon dioxide permeability and selectivity factors. CO 2 transport in swollen chitosan membranes is mainly dominated by water-facilitated reactions of CO 2 with primary amine groups of chitosan. Cussler’s model was modified to incorporate facilitated reactions caused by both free and bound water. The values of the model’s kinetic and transport parameters were consistent with the reaction chemistry of the facilitated process and the physical chemistry of the polymer.