CO2, N2 gas sorption and permeation behavior of chitosan membrane

The sorption equilibria for CO2 and N2 in dry chitosan membrane at 20 and 30 ‡C were measured by a pressure decay method. The steady-state permeation rates for CO2 and N2 in dry and wet (swollen with water vapor) chitosan membranes at 20 and 30 ‡C were measured by a variable volume method. The sorption equilibrium for N2 obeyed Henry’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 permeability 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 interpreted in terms of a modified free-volume model. The mean per-meability coefficient for N2 in dry chitosan membrane only slightly increased with upstream gas pressure. The per-meabilities for CO2 and N2 in wet chitosan membrane increased by 15 to 17 times and 11 to 15 times, respectively, as compared to those in the dry membrane.