The Ba form of a silicoaluminophosphate-34 (SAPO-34) zeolite membrane was synthesized and investigated for carbon dioxide (CO2)/nitrogen (N-2) separation with low CO2 concentration (as low as 5%) in the feed. The effects of the separation temperature, CO2 concentration in the feed, and pressure difference on the separation performance of the Ba form of a SAPO-34 zeolite membrane were investigated. A CO, gas permeance of 17.5 x 10(-7) mol/m(2).s.Pa and a CO2/N-2 separation selectivity of 78 were attained for the Ba form of a SAPO-34 zeolite membrane at 100 kPa pressure difference, 303 K, and 5% CO2 concentration in the feed. With low CO, concentration (5%) in the CO2/N-2 mixture, the Ba form of a SAPO-34 zeolite membrane was efficient in CO2/N-2 separation and displayed good stability for the separation performance of CO2/N-2 gas mixtures, in a gas separation durability test up to a total durability test time of 58 h.