Amine-containing CO2 facilitated transport membranes have great potential to be applied for hydrogen purification from synthesis gas. In some applications, the humidity of the retentate stream is required as well as the purity of hydrogen. The membranes are highly hydrophilic, and they exhibit not only high CO2 permeance but also high water vapor permeance. In this work, the transport of water vapor and CO2 through the membranes composed of an amine-containing selective layer and a microporous polysulfone substrate was investigated. From the experiments conducted, water vapor permeance appeared to be independent of the selective layer thickness, indicating that the substrate is the controlling factor of the mass transfer resistance to water vapor transport. Moreover, water vapor permeance appeared to reduce linearly with increasing the number of the substrate layers. But, CO2 permeance and CO2/H-2 selectivity did not change significantly as the number of the substrate layers increased. These results indicated that the CO2 separation performance is governed by the selective layer as expected. In addition, the membranes synthesized from Lupamin (R) containing 34% polyvinylamine and 66% salt (sodium formate) demonstrated better CO2 separation performance than those from pure polyvinylamine, presumably due to better water retention capability of the salt than polyvinylamine. (C) 2014 Elsevier B.V. All rights reserved.