Preparation of hollow fiber nanofiltration (NF) membranes by "Phase Separated and Pressurization"(PSP) method and their performance studies.
Y. S. Jeon1, J. W. Rhim*
Department of Chemical Engineering, Hannam University, Daejeon, Korea*
It is well-known the nanofiltration (NF) membrane process is a type of pressure driven membrane process between the reverse osmosis and ultrafiltration membrane process. It use has been increasing gradually world wide because of the high retention of multivalent anion salts and organic molecules with molecular weight range from 100 to 1000 as well as other advantage such as low operating pressure, low invest ment, and low operation and maintenance costs. Furthermore, NF is a promising technique for production of drinking water form surface and ground water[2,3].
A new technique is introduced for the preparation of composite membranes based on the salting-out effect. The pore blocked polyelectrolyte by forced fouling induction "phase separated and pressurization"(PSP) has the role of a membrane. In this study, water-soluble polymer as the coating materials, namely poly(styrene sulfonic acid) (PSSA), poly(4-styrene sulfonic acid-co-maleic acid) (PSSA_MA), poly(vinyl sulfonic acid) (PVSA), and polyethylenimine (PEI) were used. The polymer particles formed by the addition of Mg(NO3)2°¤6H2O were pressurized and flown to the surface of microporous polyvinyledene flouride (PVDF) membrane to prepare composite membranes under varying conditions of typically polyelectrolyte concentration, coating time, ionic strength of salt, pressure, cross-linking time and concentration, etc.
The resulting membranes were characterized in terms of the flux and rejection for 100 ppm NaCl at 4 atm to determine their suitability for application in a household water purifier. The double layer composite membrane prepared by of 148.3 LMH and 81.7% for 100 ppm NaCl. The cross-linking by isophthaloylchloride (IPC) led the flux very low to almost half-time but the rejection was not affected. The low IPC concentration up to 0.3% showed a better performance of 20 LMH and 84.5%, respectively. A combination of PVSA and PEI polyelectrolyte complex produced by the PSP method showed the best performance of flux of 43 LMH and Salt rejection rate of 83%, and this performanced was maintained without loss of flux or rejection rate in a durability test carried out for 10 days.
 X. Lu, X.Bian, L. Shi, J.Membr. Sci.,210, 3 (2002).
 A.I. Schäfer, A.G. Fane and T.D. Waite, Water Res., 36, 1509 (2001).
 A. Gorenflo, D. Velazquez-Padron and F.H.Frimmel, Desalination, 151, 253 (2002).