CO2-selective membranes that obtain high CO2 permeabilities accompanied with high CO2/H-2 and CO2/N-2 separation factors at industrial temperatures and pressures are applicable to fuel cell operations and flue gas purification. This paper describes the separation of carbon dioxide from a mixed gas stream of hydrogen and nitrogen by a chitosan membrane containing 40 wt% sodium arginate. Continuous membrane separations were done for a feed gas with 10% carbon dioxide, feed gas total pressures of 152 and 507 pa (1.5 and 5 atm), and temperatures ranging from 20 to 150 degrees C. The addition of arginine salts increases the number of amino groups for facilitated transport of CO2 and increases the water levels in the arginine salt-chitosan membranes compared to swollen chitosan membranes at the same humidification conditions. At 152 pa (1.5 atm) feed pressure and 110 degrees C, there are maxima in the carbon dioxide permeabilities (1500 barrers), and the separation factors for CO2/N-2 (852) and CO2/H-2 (144). At higher pressure (507 pa (5 atm)), there were no maxima in the carbon dioxide permeabilities or separation factors, and there was less bound water in the membrane. (c) 2009 Published by Elsevier B.V.