High-flux, antibacterial composite membranes via polydopamine-assisted PEI-TiO2/Ag modification for dye removal

The use of engineered nanomaterials in membrane design has proved promising to enhance the membrane separation performance and confer additional specific functionalities to a membrane. Enlightened by the robust adhesion of bioinspired coatings, super-hydrophilic titanium dioxide (TiO2) coupled with polyethylenimine (PEI) was stably anchored on the surface of a polydopamine (PDA)-coated membrane through vacuum filtration. The combination of organic-inorganic hybrid layer with PDA coating endowed the composite membrane with an excellent separation performance. Further in-situ formation of silver nanoparticles (Ag NPs) onto the composite membrane enabled the membrane with a high antibacterial activity. The effect of TiO2 concentration on membrane separation performance was studied. The results demonstrated that PEI plays a key role to achieve a superior dye rejection, although it resulted in a distinctly decrease of water permeability. As the TiO2 loading amount increases, the water permeability notably enhanced with an overall high rejection of dye solutions. The optimal composite membrane had a quite high water permeability of 40.6 L m(-2) h(-1) bar(-1), and an excellent dye rejection. Plate counting method results showed that the Ag decorated composite membrane had a high bacteriostatic rate of 99.7%. This facile fabrication procedure and outstanding separation performance suggest that the modified membranes have a high potential in treating dye wastewater.