ABSTRACT
Permeation is the diffusion of a substance in solution through a barrier. Permeability, on the other hand, is the capacity of a porous material for transmitting a fluid. The standard unit of permeability is the darcy, equivalent to the passage of 1 cm3 of fluid (having a viscosity of 1 cP) per second through a sample of 1 cm2 crosssectional area, under a pressure of 1.013 barA/cm of thickness. In the gas industry, the feed gas is labeled the permeator, and the selected component to be separated is known as the permeate. The membranes used are thin, dense, and continuous films formed from cellulose acetate or polymers. The separation of a component in a gas mixture is carried out in three steps: the component must dissolve in the membrane wall, diffuse through the membrane material, and be desorbed on the opposite side of the membrane wall. This procedure may be defined by Henry’s law of solubility-the solubility of a gas in a liquid is proportional to the partial pressure of the gas-and by Fick’s law of diffusivity as expressed with the following equations.
