Surface engineering of polymeric membranes

Chemical and physical properties of the surface play an important role in determining the separation and permeation characteristics of membranes. However, because of the hydrophobicity of the material, the polymeric membrane tends to be fouled severely during operation. Thus, the modification of the membrane surface to impart more hydrophilicity is an attractive approach to address this issue.

Surface modification: Modification of membrane surface by plasma processing has been employed as an effective technique among various surface-treatment methods to prevent membrane fouling. The following phenomena occur due to interactions of plasma with the surface of the membrane. They are,

1) Etching and cleaning of the surface 

2) Surface functionalization and cross-linking

3) Plasma polymerization

4) Plasma-initiated polymerization/grafting

Fouling mechanism: A hydrophobic membrane surface tends to adsorb foulants due to strong hydrophobic interactions. The opposite interaction of water on the surface of the hydrophobic membrane, results in lower tendency to adsorb water. Thus, fouling is more pronounced on the surface of hydrophobic membranes compared to hydrophilic ones due to strong interaction of the solute with the membrane material.