Incorporations of 2,2′-benzidinedisulfonic acid and forward osmotic extraction-favored nanoparticles in polyethersulfone nanofiltration membrane for the simultaneous enhancements in nitrate rejection and water permeation

The nanofiltration (NF) membrane has not been extensively competent for rejection of monovalent ions (such as Cl⁻ and NO₃⁻), and the strategy for enhancing monovalent ion rejection and permeation flux still faces a significant challenge. Herein, based on our previous polyethersulfone (PES)-type NF membrane (NF-0), two novel NF membranes were fabricated with additional incorporations of 2,2′-benzidinedisulfonic acid (BDSA) and forward osmotic extraction solution-functioned nanoparticles (MNPs) to remove nitrate from the aqueous solution. The fabricated NF-BDSA membrane with introduction of BDSA in ultrathin layer displays a significant nitrate rejection of 92.2% and an acceptable permeation flux of 21 L m⁻¹ h⁻¹ at 0.6 MPa. As anticipated, the obtained NF-MNPs1.0 membrane with additional incorporation of MNPs (1.0 wt% addition) in the substrate layer of NF-BDSA membrane achieves further improvements in nitrate rejection (95%) and water permeability (32.3 L m⁻¹ h⁻¹); encouragingly, this membrane exhibits comparable monovalent ion rejection and permeation flux to reverse osmosis membrane under relatively low pressure. Compared with those of NF-0 membrane, the permeation flux and nitrate rejection of NF-MNPs1.0 membrane increase by 111.1% and 6.1%, respectively. Moreover, the superior performances of endurance, antifouling and chlorine resistance of NF-MNPs1.0 membrane demonstrate its expectable perspective of potential engineering applications.