Preparation and characterization of a novel nanofiltration membrane with chlorine-tolerant property and good separation performance

High water flux, good separation property and excellent chlorine resistance are crucial factors affecting the development of nanofiltration (NF) membranes. To obtain these properties, NF membranes were fabricated via interfacial polymerization using m-xylylenediamine (m-XDA) and polyethyleneimine (PEI) as aqueous monomers. By controlling the concentration ratio of m-XDA and PEI in the aqueous solution, it was found that the addition of PEI to the aqueous solution can increase the rejection of the NF membrane to magnesium chloride (MgCl2) and magnesium sulfate (MgSO4) from 18.3%, 54.5% to 84.4%, 94.1%, respectively. Meanwhile, the rejection to sodium sulphate (Na2SO4) and sodium chloride (NaCl) remain essentially unchanged. On the other hand, the addition of m-XDA to the aqueous solution can improve the chlorine resistance of the NF membrane, but it decreased the water flux of NF membrane. Sodium hypochlorite (NaClO) solution was used to evaluate chlorine resistance of NF membranes. After 10 000 ppm h NaClO immersion, the rejections to Na2SO4 of NF membranes prepared from the pure m-XDA and the blend of m-XDA and PEI were basically unchanged and the water flux increased. In conclusion, the obtained membranes not only exhibited good separation performance but also had good chlorine resistance.