Membrane processes are characterized by the fact that a feed stream is divided into two streams, which are called the retentate stream and the permeate stream. Either of these streams can be the ‘product’ of the process. The membrane itself is the central part of every process and can be seen as a filter between two phases. The actual separation is achieved because transport of one component through the membrane is faster than the other component(s).

The actual performance of a membrane is determined by two different factors, namely its permeability and selectivity. The permeability is defined as the volume of gas flowing through the membrane per unit of area and time. The selectivity, also known as the separation factor, is determined by the difference in permeability of the components of interest. If, for instance, the permeability of component A is three times higher than component B, the permeate stream contains three times more of component A and the selectivity from A over B is 3.

The permeability of gases and therefore selectivity between different gasses depends strongly on the gas and type of material used for the membrane. Membranes can be constructed from different starting materials. The two main classes in membrane science are organic membranes (e.g. plastics, carbon) and inorganic membranes (ceramics). Both classes of material are subject of investigation in NanoGLOWA.

Designed by Jorrit Thijssen