A high performance silica–fluoropolyamide nanofiltration membrane prepared by interfacial polymerization

• Silica sol is used for prepartion of silica–fluoropolyamide nanofiltration membrane.
• Hexafluoroisopropanol group compound is used for prepartion of NF membrane.
• Different polymerization conditions were investigated.
• The resulting membrane showed better performance after oxidation treatment.

This paper aims to enhance the performance of thin-film composite (TFC) polyamide nanofiltration (NF) membrane prepared by interfacial polymerization of 2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-trifluoroethyl)-4,4′-methylenedianiline (BHTTM) and trimesoyl chloride (TMC) on polyethersulfone (PES) supporting membrane. The active surface of the membrane was characterized by using SEM, EDS and AFM. The performance of NF membrane was optimized by studying the preparation conditions, including silica concentration, reaction time, monomers concentration, curing time and oxidation treatment. The results showed that the NF membrane prepared under the optimum condition exhibited Na2SO4 rejection of 85.0% and the water flux of 15.2 l m−2 h−1 under 0.6 MPa. The NF membrane was treated by 5000 ppm chlorine solution for 1 h. The salt rejection and water flux of the treated membrane reached to 94.0% and 105 l m−2 h−1 under 0.6 MPa. The rejection of the two NF membranes for inorganic electrolyte solutions decreased in the order of Na2SO4, MgSO4, MgCl2 and NaCl which were typical characteristics of negatively charged membranes.