Removal of Pb2+ and Fe3+ from water using N-TiO2 blended copolymer grafted asymmetric membranes

The aim of this study was to evaluate the photo-catalytic properties of nitrogen-doped titanium dioxide nano-particles supported on polymer membranes in the photo-reduction of Fe3+ and Pb2+ from synthetic wastewater. The morphology of the prepared N-TiO2 nanoparticles was evaluated using transmission electron microscopy. Successful grafting of methacrylic acid side chains onto poly(vinylidene difluoride) (PVDF) backbone was confirmed by Fourier-transform infrared spectroscopy. The photo-catalytic asymmetric membranes were prepared through the dry-wet phase inversion technique. The asymmetric morphology was evaluated using scanning electron microscopy. The highest Fe3+ photo-reduction efficiency (76.2%) was achieved in 6 hours using 1% N-TiO2-PMAA-g-PVDF/PAN (PMAA: poly(methacrylic acid); PAN: poly(acrylonitrile)) asymmetric membrane under solar irradiation. Increasing the photo-catalyst loading to 3% was found to negatively impact the photoreduction of Fe3+. Very high photo-reduction efficiencies were observed in the photo-reduction of Pb2+ using 1% N-TiO2-PAN, 1% N-TiO2-PMAA-g-PVDF/PAN and 1% N-TiO2-PVDF membranes (90.5%, 88.9% and 86.9%, respectively) under similar conditions. Increasing the photo-catalyst loading to 3% N-TiO2 was observed to slightly increase the photo-reduction efficiency in the removal of Pb2+ unlike in the case of Fe3+. The best support material for the N-TiO2 photo-catalyst was PMAA-g-PVDF/PAN.