Fundamentals of Pressure-Driven Membrane Separation Processes
Cui ZF., Jiang Y., Field RW.
This chapter presents some basic concepts related to membranes and membrane processes. Porous membranes are divided into two types according to their structures: microporous membranes and asymmetric membranes. Microporous membranes are characterized by the membrane pores throughout the membrane bodies. The pores are of uniform size (isotropic) or nonuniform size (anisotropic). Microporous membranes are designed to reject all the species above their ratings. In terms of materials, membranes can be classified into polymeric or organic membranes and ceramic or inorganic membranes. Organic membranes are usually made up of various polymers, among which the typical ones are cellulose acetate (CA), polyamide (PA), polysulfone (PS), polyethersulfone (PES), polyvinylidene fluoride (PVDF), and polypropylene (PP). Polymeric membranes are relatively cheap, easy to manufacture, available in a wide range of pore sizes, and they have been widely used in various industries. Inorganic membranes with the high mechanical strength and chemical and thermal stability over the conventional polymeric membranes have extended the application of membrane technology into many new areas. Membrane module is the way the membrane is arranged into devices and hardware to separate the feed stream into permeate and retentate streams. There are four kinds of membrane modules widely used in industry: tubular modules, hollow fiber modules, flat sheet modules, and spiral-wound modules.