Limiting thickness of polyamide–polysulfone thin-film-composite nanofiltration membrane

Abstract

A systematic study was carried out to explore limiting thickness of the state-of-the-art nanofiltration membrane. The interfacial polymerization between aqueous solution of piperazine and organic solution of trimesoyl chloride over polysulfone ultrafiltration supports of average pore size 20, 100 and 200nm, respectively had been performed to vary the membrane thickness and properties. The prepared membranes were designated as TFC-12, TFC-15 and TFC-24, respectively. Influence of the supports on membrane thickness, surface roughness and potential was observed by SEM, AFM, ATR-IR and zeta-potential measurements. The membrane thickness and surface roughness were found in increasing order of TFC-12<TFC-15<TFC-24. When tested for desalination of brackish water of 2000ppm NaCl or 1000ppm MgSO4 at 150psig, TFC-24 exhibited the highest salt rejection efficiency but the least flux of 26l·m−2·h−1 while the flux was enhanced to about 94l·m−2·h−1 but with lesser salt rejection for TFC-12 which was in agreement with the differences in membrane thickness and roughness. The results indicated a trade-off performance relationship for the nanofiltration membranes that the membranes of high-flux with moderate selectivity or high-selectivity with moderate flux could be prepared by varying supports from a same preparation condition.