A preliminary investigation of the permeation of some permanent gases through foam membranes

To evaluate gas permeation properties of foam membranes, a preliminary investigation of the permeation of O₂, N₂, and CO₂ through a monolayer of foam bubbles formed on an aqueous glycerol solution with saponin as surfactant was carried out in a new static foam membrane test cell. Foam stability, a prerequisite to meaningful measurement, was highest with a 70% glycerol solution. Using the notion of an average foam bubble, time-dependent measurements of gas composition above foam bubbles and foam bubble height reduction yielded values of permeation parameters from the solution of appropriate mass balance equations. The O₂ permeation parameter defined by the ratio of the O₂ permeability coefficient and the foam bubble wall thickness was found to have a value comparable to that of a 1-mil-thick silicone rubber film. The O₂N₂ separation factor, found to be around 2 for the same system, is comparable also to that of a silicone rubber film. Significant absorption of CO₂ in the surfactant liquid solution suggests limitations of this new foam permeation cell to gases with extremely limited solubility.