Synergistic antifouling PBI nanofiltration membrane via Ag@UiO-66-NH₂ immobilization and hydrophilic polymer brush grafting for dye/salt separation

Membrane fouling significantly limits the application of membrane separation technology in the treatment of textile dyeing wastewater. In this study, a loose nanofiltration membrane made of polybenzimidazole (PBI) with enhanced antifouling and high-efficiency dye/salt separation capabilities was developed through Ag@UiO-66-NH₂ immobilization and hydrophilic polymer brush grafting. Initially, Ag@UiO-66-NH₂ nanoparticles, possessing antibacterial properties, were incorporated into the PBI base membrane. Subsequently, a brush-like antifouling layer was constructed on the membrane surface by grafting linear polypropylene glycol (PPG) and polyethylene glycol (PEG). Experimental results revealed that the grafting modification substantially improved the membrane's performance: the rejection of the small-molecule dye Methyl Red increased from 16.8 % to 59.6 %, and the membrane surface hydrophilicity was enhanced, leading to a slight improvement in pure water flux. Additionally, the grafted layer effectively suppressed the adsorption of bovine serum albumin, with a flux recovery rate remaining above 90 % after four fouling cycles. Furthermore, the membrane exhibited rejection of <10 % for inorganic salts (Na 2 SO 4 , NaCl, MgSO 4 and MgCl₂), achieving efficient separation of dyes and salts. In tests with simulated textile dyeing wastewater, the membrane's rejection for industrial dyes remained stable at over 90 %, and the addition of surfactants and auxiliaries had no significant impact on its performance. This study shows that the combination of immobilizing MOF nanoparticles with controlled release properties of biocides and grafting hydrophilic polymer brush can effectively improve the separation efficiency and antifouling performance of the membrane, which provides a new method for the treatment of complex textile printing and dyeing wastewater.