Modified LTA membranes supported on macroporous carbon discs have been synthesized for the separation of H(2) and CO. These membranes have been prepared by hydrothermal synthesis following the secondary growth method and subsequently ion-exchanged with different alkaline cations in order to modify the zeolite pore size. Their permeation properties have been studied for the purification of a hydrogen stream (50 vol.%) containing carbon monoxide (1.25 vol.%). For this purpose, a Wicke-Kallenbach cell has been used to perform the separation experiments. Single gas permeation properties and bicomponent mixtures were carried out at three different temperatures (298K, 398 K and 423 K). Our results indicate that even the K-LTA form would be suitable for the purification of H(2) at room temperature. The Rb- and Cs-forms exhibit the best performance, in which CO permeation is blocked at all temperatures studied. As a result, a high purity H(2) stream may be obtained by employing the Rb- and Cs-membranes derived from Na-LTA/carbon membranes. (C) 2010 Elsevier B.V. All rights reserved.