Question

what are the physical and chemical properties and mechanical structure of typical synthetic membrane used in mass separation processes?

Answer 1

Physical properties

1) Pore Diameter

Pore diameter is probably the most important property characterizing a microporous membrane. Although microporous membranes are usually characterized by a single pore diameter, note that most membranes actually contain a range of pore sizes (i.e. there exists a pore size distribution).

2) Porosity

Porosity is the fraction of total membrane volume that is porous. Typical microporous membranes have average porosities from 0.3 to 0.7.

3) Tortousity

Membrane tortousity (t) is the length of the average pore compared to the membrane thickness. Simple cylindrical pores at right angles to the membrane surface have a tortousity of 1.0. Since pores usually take a more meandering path through the membrane, typical tortousities are in the range of 1.5 to 2.5.

Some examples of the synthetic membrane:

Chemical properties of synthetic membrane:

1) Hydrophilicity or hydrophobicity (related to surface free energy)
2) Membrane chemical or thermal resistance
3) Binding affinity for particles in a solution
4) Biocompatibility (in case of bioseparations)

Mechanical structure of synthetic membrane:

Typical strucure with examples,

There are different modules of synthetic membrane used in mass separation,

1) Hollow fibre membrane module

2) Plate and frame membrane module

3) Spirally wound

4) Flate sheet

5) Tubular membrane module