Saturated brine in chlor-alkali plant contains some impurities including Mg2+, Ca2+, Fe2+ and SO42- that affect the performance of the process. Membranes may be used in combination with other treatment methods to decrease the impurities to a desirable level. In this work totally seven polymeric membranes (FT30, PVD, DOW-PS, TFC-SR, BW30, 37100 and NF45) were employed to treat the saturated brine. The polyethylene terphetalate PVD membrane at 8 bars and 40 degrees C showed the best performance with moderate flux, appropriate removal of impurities and minimum NaCl rejection. The hydrophilic polysulfone 37100 membrane exhibited highest flux (300 l/m(2) h) without adequate removal of impurities. Nanofiltration polyterphetalate NF45 membrane showed high ability for removal of Fe2+ (98%) with undesirable level (21%)of rejection of NaCl. The DOW-PS membrane demonstrated maximum SO42- removal. The ion rejection depends on the size (hydration radius) and concentration of ions. Larger ions, i.e. with higher hydration radius and lower concentration exhibit the highest rejection. (C) 2007 Elsevier B.V. All rights reserved.