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 ~ trimesoyl chloride” (PIP-TMC) interfacial polymerization. AMIB molecules were anchored to membrane surface through “acyl chloride ~ amine” amidation. Salt rejection and water flux of the modified membrane (PIP-TMC-AMIB) was 95 ± 1% (RNa2SO4) and 135 ± 5 L m−2 h−1 at 6 bar pressure. Thus the permeance of the modified TFCM is ~ 4 times as high as that of lab-made pristine PIP-TMC TFCM. The PIP-TMC-AMIB membrane shows high water permeance (~ 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.