Porous membranes, polymeric applications

In this chapter, gas-solid systems, with an emphasize on inorganic permeable materials, to produce dense and porous membranes for chemical, sustainable energy, and pollution abatement applications, are considered. However, since the most important membranes currently in use are the polymeric porous membranes, then these are discussed at the end of the chapter. 

For separation applications using porous membranes like microfiltration and ultrafiltration, the choice of polymeric material does not influence significantly the... 

Membranes are classified by whether the thin permselective layer is porous or dense, and by the type of material (organic, polymeric, inorganic, metal, etc.) this membrane film is made from. The choice of a porous vs. a dense film, and of the type of material used for manufacturing depends on the desired separation process, operating temperature and driving force used for the separation the choice of material depends on the desired permeance and selectivity, and on thermal and mechanical stability requirements. For membrane reactor applications, where the reaction is coupled with the separation process, the thin film has also to be stable under the reaction conditions. 

The membrane of a hollow-fiter form is a convenient polymeric material in that expansion from a laboratory to a plant scale can be carried out simply by bundling the hollow fibers into a hollow-fiber membrane module [14,15]. The phenomenon of multilayer binding of the enzymes into the polymer chains grafted onto the porous hollow-fiber membrane is applicable to other enzymatic reactions at a high throughput. 

FIGURE 9.21 Magnetically triggered microchip. Cross section of a single polymeric reservoir device for reversible drug delivery. Application of a magnetic field would either raise the particles and block the porous membrane (off state) or lower the particles and open the membrane (on state). Reproduced with permission from [168], Copyright 2009 John Wiley ... 

The processes where porous membranes find their main applications are pressure-driven ones, such as microfiltration, ultrafiltration and nanofiltration. These processes are also especially interesting due to their wide range of practical applications. They can be used for the processing of fine particles, colloids and biological materials such as protein precipitates and microorganisms [3]. Membranes used are commonly polymeric materials but innovative development has been made in the fields of ceramic and inorganic membranes. 

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