Development of thin film nanocomposite membranes tailored using a Tb-MOF for municipal wastewater reclamation

The application of direct membrane filtration can reduce the space and energy footprint of the treatment process. The current study focuses on developing thin-film nanocomposite (TFN) membranes using a terbium-based metal–organic framework (Tb-MOF) via interfacial polymerization (IP). The salient features of the Tb-MOF include a rod-shaped morphology, a porous structure, and hydrophilic functional groups. These features of the Tb-MOF are ideal for the effective filtration performance of the membranes. The successful incorporation of the Tb-MOF into the poly(1,2-diaminopropane-terephthalamide) active layer was confirmed by physicochemical characterization of the membranes, which revealed changes in surface charge and morphology. The nuclear magnetic resonance (NMR) experiment also confirmed the integral structure of poly(1,2-diaminopropane-terephthalamide), showing characteristic peaks attributable to bifunctional 1,2-diaminopropane (1,2-DAP) and terephthaloyl chloride (TPC). The presence of Tb³⁺ in the active layer was also evidenced through different characterization techniques, including the broadening of the NMR peaks of poly(1,2-diaminopropane-terephthalamide), confirming the presence of the Tb-MOF in the membrane′s active layer. Owing to the incorporation of the Tb-MOF in the membrane active layer, the surface hydrophilicity of the membrane was increased, which was reflected by a water contact angle of ∼44°. The fabricated membranes were applied for microplastics (polyvinyl chloride, PVC) removal, including the removal of potential per- and polyfluoroalkyl substances (PFAS) such as poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP). The membranes exhibited excellent rejection of approximately 95% of the PVC- and PVDF–HFP-containing feed, with the TFN-15 membrane showing a rejection of around 98% of pollutants. In terms of permeability, increasing the Tb-MOF concentration in the membrane structure increases permeability. The TFN-10 membrane performed the best, achieving a flux recovery ratio (FRR) of nearly ∼87.0%. The filtration of municipal wastewater showed that the TFN-15 membrane possessed a permeate flux of 20 L m⁻² h⁻¹, whereas the TFC control membrane showed a permeate flux of ∼10.87 L m⁻² h⁻¹ at a transmembrane pressure (TMP) of 800 kPa. Among the different fabricated membranes, the TFN-15 achieved the best performance index (PI) of 10.27 during the treatment of municipal wastewater. Cake-layer formation was the primary fouling mechanism among those studied.