Charge-cascade heterogeneous nanofiltration membrane with enhanced separation and multifunctional anti-fouling for landfill leachate treatment

Achieving precise and selective separation of ions with simultaneous settlement of the trade-off effect and membrane fouling is crucial but also challenging in membrane applications that involve the treatment of complex compositions. Motivated to tackle this problem, we developed a strategy for charge cascaded heterogeneous nanofiltration (NF) membrane utilizing MXene and glycine (Gly) intervened cetyl trimethyl ammonium bromide (CTAB). X-ray photoelectron spectroscopy (XPS) combined with Zeta potential determined that the stepwise deposition of functionalized materials produced a significant cascade effect on the charge distribution of the membrane active layer. Improved hydrophilicity and roughness, as well as dramatically reduced active layer thickness, enhanced the water permeability of the stacked heterogeneous membrane and harmonized the trade-off effect of the NF membranes. The positive–negative mixed internal channels, and the tuned pore size distribution enhanced ions rejection to 97% for Na 2 SO 4 and provided excellent selectivity for Cl − /SO 4 2− ion pairs, which was quantified at 20.3. Theoretical calculations showed that the free energy of adhesion of polar acid-base ( ΔG AB ) dominated the contribution to membrane fouling, and the functionalized membrane exhibited significant repulsion of foulants. Heterogeneous membrane demonstrate excellent efficiency in the advanced treatment of landfill leachate, achieving an 85% removal rate of chemical oxygen demand (COD) and ensuring compliance with discharge standards. Furthermore, through the synergistic effects of their antibacterial and anti-adhesion properties, the membranes significantly reduce the total biomass by 82.5%. This study adequately integrated the advantages of heterogeneous materials to achieve efficient enhancement of membrane transfer property as well as fouling mitigation in practical application.