To improve liquid membrane selectivity and stability for removal of vapor and gases from a gas stream, a thin immobilized liquid membrane (ILM) has been studied. Low vapor pressure liquid solvent/solutions were immobilized in part of the micropores of a hydrophilic, hydrophobic or ceramic hollow fiber substrate. To prepare such thin ILMs, three approaches were used: evaporation of the a volatile solvent; acrylic acid-grafted hollow fibers providing a thin hydrophilic layer; pressurization technique.

For removal of volatile organic compound (VOC), a thin ILM of silicone oil incorporated in the micropores of a hydrophobic hollow fiber with a silicone rubber coating yielded a highly VOC-enriched permeate and increased separation factor. The same ILM was stable over an extended period (6 months - 2 years) demonstrating the potential utility of such an ILM-based hollow fiber device for VOC-N₂/air separation. A mathematical model was successfully developed to describe the VOC-N₂ permeation-separation in a hollow fiber permeator having this special type of membrane containing a thin ILM.

Grafting method used for the preparation of a thinner ILM resulted in various hollow fibers having different hydrophilic layer thickness. These fibers were used to study the effect of various glycerol-based and aqueous liquid membranes immobilized in the thin hydrophilized part of the fiber. Glycerol-based ILMs resulted in low CO₂ permeances in the range of 1*10^-6 cm³/cm²*s*cmHg for enclosed atmosphere application; aqueous based ILMs has much better performance.

A pressurization technique was used to prepare a thin ILM in porous hydrophilic and ceramic substrates. It was shown that when appropriate asymmetric hollow fibers substrates were used, increase in CO₂ permeance was achieved.