Surface modification methods of organic solvent nanofiltration membranes

Organic solvent nanofiltration (OSN) is an emerging technology in which membranes are used for organic solvent separation and purifications. Its fields of applications range from pharmacy, catalyst regeneration, to oil and solvent treatments. A major challenge is to maintain a high stability of these (modified) membranes under different feed conditions. Tailoring the selective layer of OSN membranes is the main approach to develop functionalized membranes which show stable high selectivities and permeabilities. During the past decade, methods such as grafting, light-induced modification, plasma treatment, and polyelectrolyte modification have been intensively studied. This paper reviews the recent progress in this field of surface modification of different types of polymeric and also of ceramic OSN membranes. First, the most crucial surface layer properties that affect the OSN membranes properties are described in detail. Next, different surface modification methods and their effects on membrane selectivity and permeability are reviewed and compared. Finally, a perspective is given on expected future trends in this highly challenging and important field of current research.