Dual mode model for mixed gas permeation of CO2, H2, and N2 through a dry chitosan membrane

Dry chitosan is an excellent candidate for facilitated transport membranes that can be utilized in industrial applications, such as fuel cell operations and other purification processes. This article is the first to report temperature effects on transport properties Of CO2, H-2, and N-2 in a gas mixture typical of such applications. At a feed pressure of 1.5 atm, CO2 permeabilities increased (0.381-26.1 barrers) at temperatures of 20-150 degrees C with decreasing CO2/N-2 (19.7-4.55) and CO2/H-2 (3.141.71) separation factors. The pressure effect on solubilities and permeabilities were fitted to the extended dual mode model and its corresponding mixed gas permeation model. The dual mode and transport parameters, the sorption heats and the activation energies of Henry's and Langmuir's regimes and their pre-exponential parameters were determined. The Langmuir's capacity constants were utilized to estimate chitosan's glass transition temperature (CO2: 172 degrees C, N-2: 175 degrees C, and H-2: 171 degrees C). The activation energies of diffusion in the Henry's law and Langmuir regimes were dependent on the collision diameter of the gases. (c) 2007 Wiley Periodicals, Inc.