CO2, N-2 GAS SORPTION AND PERMEATION BEHAVIOR OF CHITOSAN MEMBRANE

The sorption equilibria for CO2 and N-2 in dry chitosan membrane at 20 and 30 degrees C were measured by a pressure decay method. The steady -state permeation rates for CO2 and N-2 in dry and wet (swollen with w ater vapor) chitosan membranes at 20 and 30 degrees C were measured by a variable volume method. The sorption equilibrium for N-2 obeyed Hen ry's law, whereas that for CO2 was described apparently by a dual-mode sorption model. This non-linear sorption equilibrium for CO2 could be interpreted by the interaction of sorbed CO2 with the chitosan matrix expressed as a reversible reaction. The logarithm of the mean permeab ility coefficient for CO2 in dry chitosan membrane increased linearly with upstream gas pressure. A linear increase of the logarithmic mean permeability coefficient for CO2 with the pressure could be interprete d in terms of a modified free-volume model. The mean permeability coef ficient for N-2 in dry chitosan membrane only slightly increased with upstream gas pressure. The permeabilities for CO2 and N-2 in wet chito san membrane increased by 15 to 17 times and 11 to 15 times, respectiv ely, as compared to those in the dry membrane.