Preparation and characterization of loose antifouling nanofiltration membrane using branched aniline oligomers grafted onto polyether sulfone and application for real algal dye removal

[Display omitted] •An impressive diazonium-induced grafting is suggested to modify NF PES membrane.•Branched aniline oligomers were covalently grafted in the membrane surface.•Diazonium-induced grafting provided good permeability in the modified membranes.•The BAO-modified membranes exhibited excellent antifouling property. This research presents a simple and versatile procedure (diazonium-induced grafting) for in situ surface functionalization of Polyethersulfone (PES) membrane through covalent attachment of aniline oligomers. The process involves gradual reduction of oligomer diazonium salts which yields a superhydrophilic layer of branched aniline oligomers (BAO) grafted on the membrane surface. With this procedure, the PES nanofiltration membrane, alter facilely from hydrophobicity to superhydrophilicity. The structural characteristic, nanofiltration performance, antifouling behavior and chemical, mechanical and long-term permeation stability of prepared membranes were evaluated. The modified membrane showed great performance with high water flux (93.6 L/m2 h bar), high flux recovery ratio 99% and after fouling with powdered milk protein for 90 min. The novel BAO-PES modified membrane had long-term structural stability in an acidic and basic environment that it’s a critical property for real operation in industry. Its application in algal dye removal was also assessed using a real algal wastewater from a working stabilization pond in a cross-flow filtration system for a 62-h period. The modified membrane showed a smooth behavior in flux with only 11.45% reduction after 62 h, indicating outstanding stable permeability and anti-fouling function provided by the applied modification. This modification demonstrates great potential for convenient practical application.