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 photo-reduction 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.