Environmental Engineering Reference
In-Depth Information
Section 2
Membrane separation
Before continuing this section, it is important to discuss in some detail
how membrane separation works. We have already mentioned fi ltration.
Filtration is based on sieving; molecules or particles that are too big will
not pass through the pores of a membrane. If fi ltration were the only
mechanism, we would not be able to separate two types of molecules if
both can pass through the membrane. As we will show, to separate two
gasses, a difference in permeation — the ease with which molecules
pass through a membrane — is suffi cient to achieve a separation.
Simple membrane
Let us look at the membrane shown schematically in Figure 7.2.1 . In this
fi gure, our membrane is a piece of material through which there is a fl ow.
Permeate
A
L
Figure 7.2.1 Simple membrane
A simple membrane with a thickness L and area A . The feed splits into two streams, one
going through the membrane, which is called the permeate, and the retentate.
 
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