Two swollen polyamide thin-film composite membranes were tested for effective CO2/ CH4 separation. It was found that water wettability (Fig. 52) played a key role in the separation of a binary mixture representing raw biogas, i.e. containing CO2 and CH4. The transport properties were analysed by means of a mathematical model simulating for gas permeation. A new modification of the mass transport coefficient model provided the concentration profiles of individual\ncomponents on both sides of the membrane (inaccessible in experiments).\n\n