Hybrid Adsorption–Nanofiltration Using Modified PEI-Based Mixed Matrix Membranes for Efficient Dye Rejection from Wastewater

This study presents a novel hybrid system combining adsorption and nanofiltration (NF) using modified polyetherimide (PEI)-based mixed matrix membranes. The membranes were fabricated with varying epoxy (EP) concentrations (10%, 15%, 20%) and fixed loadings of graphene oxide (GO) and kaolinite (K). Membrane performance was evaluated in terms of morphology, hydrophilicity, permeability, dye rejection, and antifouling behavior. Pre-adsorption of methylene blue (MB) using activated carbon, followed by NF, significantly enhanced dye rejection rate. The rejection rates of MB by PEI-15% EP and PEI-20% EP membranes reached 85% and 80%, respectively, while the rejection rates without adsorption were only 60.1% and 59.85%. Notably, the PEI-20% EP membrane exhibited the highest flux recovery ratio (FRR) of 88.6%, lowest total fouling ratio (13.4%), and irreversible fouling ratio (15.4%). These results demonstrate that integrating adsorption with nanofiltration, supported by a modified PEI/EP/GO/K membrane, offers a synergistic approach for enhanced dye rejection and fouling resistance presenting a promising solution for industrial wastewater treatment.