ABSTRACT
Processes based on synthetic or modified natural polymeric membranes are widespread and impact many commercial technologies. This chapter deals with pressure-driven liquid and gas separation applications in more detail, since these are the areas most commonly associated with the terms “synthetic membranes.” Most membrane processes appear to be similar and rather simple when considered on a macroscopic level. Processing of streams with porous membranes enables one to concentrate thermally sensitive macromolecules and to sterilize solutions and air streams by elimination of microbes and viral agents. Reverse osmosis technology is also suitable for dealing with organic as well as aqueous systems, but difficulties with membrane stability under actual operating conditions have retarded such applications. The pervaporation process is a limiting case of reverse osmosis in which a vacuum is applied to the downstream membrane surface to reduce the thermodynamic activity of the penetrant to zero in order to maximize the driving force for permeation.
