Highly chlorine-tolerant performance of three-channel capillary nanofiltration membrane with inner skin layer

Abstract

Good mechanical strength, high water flux and salt rejection, and highly chlorine-tolerant property are essential for nanofiltration (NF) membrane. To achieve these properties, polyethersulfone (PES) NF thin-film composite (TFC) membrane was prepared via interfacial polymerization using piperazine (PIP) and 2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-triflutoethyl)-4,4′-methylenedianiline (BHTTM) as aqueous monomers, trimesoyl chloride (TMC) as organic monomers, and PES three-channel capillary ultrafiltration (UF) membrane as substrate. The prepared NF membrane displays pure water flux of 36.1Lm−2h−1 and Na2SO4 rejection of 96.8% at 4bar. NaClO solution was used to treat NF membranes for the evaluation of NF membrane chlorine-tolerant property. The effects of NaClO concentration, contact time and operating pressure on the chlorine-tolerant property of NF membrane have been thoroughly investigated. Particularly, the durability of NF membrane versus Cl was tested though long-term test. The pure water flux and Na2SO4 rejection of NF membrane after 5000ppm-h NaClO immersion was 43.4Lm−2h−1 and 99.8% at 4bar, respectively. The fabricated NF membrane could tolerant 13000ppm-h Cl under 4bar, and the water flux and Na2SO4 rejection are maintain at 51.6Lm−2h−1 and 99.6% during NF running process, respectively. Moreover, NF membrane exhibits 3.84×105ppm-h chlorine-tolerant at 0bar. These results indicated that the fabricated PES three-channel capillary NF membrane could be applied to practical process of desalination or water softening.