Immobilized Liquid Membranes

Membranes relevant to this discussion are nonporous barriers. The fundamentals of membrane permeation through such barriers are discussed in numerous references. The separation of gases with membranes is due to differences in diffusivity and solubility. The separation factor of a membrane for a pair of gases is the ratio of permeabilities of the gases in the membrane. The basic problem is inadequate membrane performance. When high selectivity has been achieved, permeation rates were too low. A new approach to achieving high performance membranes is to use liquids as membrane materials. Robb and Reinhard observed that in general liquids have large diffusion coefficients compared to polymers; and also, for certain gases, they can have enormous solubilities. A possible disadvantage of using liquids as membrane materials is that the gas in contact with the membrane must be saturated with the liquid membrane material. An immobilized liquid membrane can be made by supporting the liquid film on a nonwetting, micro-porous membrane.