Fabrication and incorporation of MIL-53(Fe)-zwitterionic brushes into PVDF thin film composite membranes for enhancing heavy metal/dye rejection from aqueous body

The bioaccumulation of heavy metal ions is a serious concern for researchers. The dyes and heavy metal ions also aquatic life impacting the biodiversity adversely. Synthesis of novel MIL-53(Fe)-PSBMA particles, and its incorporation into PVDF-based thin-film composite membranes is the crux of this work. Firstly, H2N-MIL-53(Fe) was synthesized by metal displacement reaction which was then modified into MIL-53(Fe)-PSBMA brushes. The brushes were synthesized by atom transfer radical polymerization method. The amine groups of the NH2-MIL-53 (Fe) help connecting the MOF to the polymeric moiety. The as-synthesized material and the fabricated TFCs were characterized by BET, FTIR, XRD, XPS, TGA, AFM, FE-SEM, zeta potential, and DLS particle sizer. The presence of sulphur groups on the XPS spectrum of modified MOF ensured the successful polymer grafting on it. Zwitterionic moieties have both positive and negative charges within a single molecule which gave a resultant zeta potential of-13.1 mV for the brushes. A pure water flux of 26.32 Lm- 2 h- 1 and 97.33%, 95.19%, 82.06%, and 78.47% rejections for Pb2+, Hg2+, As3+, Cd2+ ions and 96.23 % and 94.04 % rejection for 100 ppm reactive black-5 and sunset yellow dyes respectively were obtained for the optimized membrane having 0.035 wt% loading of zwitterionic MOF. This result was attributed to the enhanced membrane hydrophilicity which was also correlated with contact angle and water uptake studies.