Membranes for microfiltration

Various techniques can be employed to prepare microfiltration membranes from polymeric materials:

 - sintering ¨    

 - stretching ¨    

 - track-etching . ¨    

- phase inversion.

Frequently, inorganic membranes are used instead of polymeric membranes because of their outstanding chemical and thermal resistances. In addition, the pore size in these membranes can be better controlled 81\d as a consequence the pore size distribution is generally very narrow. Various techniques can be used to prepare ceramic membranes with some important ones being:

- sintering ¨    

- sol/gel process ¨    

- anodic oxidation

 MF is the membrane process which most closely resembles conventional coarse filtration. The pore sizes of MF membranes range from 10 to 0.05mm, making the process suitable for retaining suspensions and emulsions.

The volume flow through these MF membranes can be described by Darcy’s law, the flux J through the membrane being directly proportional to the applied pressure:

                                                J=A*P

 Where the permeability constant A contains structural factors, Such as the porosity and pore size (pore size distribution).

 In order to optimize MF membranes, it is essential to ensure that structural parameters are such that the (surface) porosity  is as high as possible with the pore size distribution as narrow as possible.