Mass Transport in Porous Liquid Phase Membranes

The mass transfer processes involved in transporting materials from the bulk feed solution through the membrane to form a permeate stream is discussed. The complex microhydrodynamics and interfacial events occurring at the membrane surface and within the membrane itself are outlined. A description of concentration polarization at the membrane surface is described and the concept of real and observed membrane rejection is introduced. The separation of solutes by a membrane is an equilibrium controlled process and this concept is explained in relation to that of a simple sieve and the controlling factors of steric and electrostatics are described. The effect of chemical potential on the transport of solutes through the membrane pore is explained and a mathematical description of this complex phenomena based on the extended Nernst-Planck equation is provided. Finally, the operating conditions and industrial applications of liquid phase membrane processes are outlined to provide the reader with a working knowledge of these high efficiency separation processes.