High performance polyamide nanofiltration membranes enabled by surface modification of imidazolium ionic liquid

An imidazolium ionic liquid (1-aminoethyl-3-methylimidazolium bromide, AMIB) was exploited to prepare thin film composite membranes (TFCMs) exhibiting high water permeability, salt rejection, antibiotics separation and antibacterial properties. Polyamide TFCMs were prepared by piperzine similar to trimesoyl chloride (PIP-TMC) interfacial polymerization. AMIB molecules were anchored to membrane surface through acyl chloride similar to amine amidation. Salt rejection and water flux of the modified membrane (PIP-TMC-AMIB) was 95 +/- 1% (R-Na2SO4) and 135 +/- 5 L m(-2) h(-1) at 6 bar pressure. Thus the permeance of the modified TFCM is similar to 4 times as high as that of lab-made pristine PIP-TMC TFCM. The PIP-TMC-AMIB membrane shows high water permeance (similar to 25 Lm(-2) h(-1) bar) and effective rejection (>90%) toward antibiotics such as 50 ppm ciprofloxacin, tetracycline, oxytetracycline, levofloxacin and erythrocin. In addition, the membrane exhibits effective separation of antibiotics/sodium chloride mixtures, and highly improved antibacterial properties by killing 99% E. coli colonies.