The effect of surface characteristics on RO membrane performance

Grafting of vinyl monomers containing polar pendant groups such as ---C=N of 4-VP and ---CN of methacrylonitrile can impart desirable properties to the Teflon-FEP. In the present work grafting of 4-vinyl pyridine (4-VP) and mythacrylonitrile (MAN) onto Teflon-FEP film has been carried out by preirradiation method in aqueous medium. Optimum conditions for affording maximum percentage of grafting (Pg) have been evaluated. Maximum percentage of grafting of 4-VP (16.35%) at a total dose of 51.62 KGy was obtained ata monomer concentration of 0.93 moles/L. For MAN maximum percentage of grafting (31.70%) at a total dose of 49.90 KGy was obtained at a monomer concentration of 1.19 moles/L. Several grafting experiments were carried out in water-alcohol medium to study the effect of alcohols on Pg of 4-VP and MAN. The following order of different alcohols towards grafting of these monomers is observed. For 4-VP: Isopropanol> n-pentanol> ethanol> butanol> methanol. For MAN: Isopropanol> ethanol> methanol> butanol> n-pentanol. In all binary water-alcohol systems percentage of grafting was found to decrease with increasing amount of alcohol as compared to that obtained in the aqueous medium. The grafted Teflon-FEP films have been characterized by IR Spectroscopy, scanning electron microscopy, swelling behaviour in different solvents, percentage area change following grafting and by permeability behaviour.