Fabrication of polyamide membranes by interlayer-assisted interfacial polymerization method with enhanced organic solvent nanofiltration performance

In this contribution, thin-film nanocomposite membranes with an interlayer (TFNi) were fabricated on poly (m-phenylene isophthalamide) (PMIA) substrates for organic solvent nanofiltration (OSN). The selective layer was formed by interfacial polymerization between 1,3,5-benzenetricarbonyl trichloride in the ionic liquid phase and mixed amine monomers in the aqueous phase. Five types of interlayer materials were prepared via a facile mixing method. After systematical characterizations, it was found that interlayer materials could not only adjust the surface morphology, porosity, and hydrophilicity of the substrate but also promote the controlled growth of thin and defect-free polyamide (PA) layer via the subsequent interfacial polymerization process. We also analyzed the radar chart representation of the various characteristic values of the membrane physiochemical properties (thickness, crosslinking degree, roughness, and hydrophilicity) and membrane separation performance (permeance, and rejection), in order to elucidate their relationships. Among the five TFNi membranes, PMIA/Co-PIP/PA membrane showed high ethanol permeance (2.93 L m−2 h−1 bar−1), high rejection (∼95%) of organic solutes with molecular weights above 697 Da, and robust long-term stability during separating erythromycin/methanol mixtures (50 h). The designed TFNi membranes were superior to the traditional PMIA/PA membrane, and the permeance of which was only 0.7 L m−2 h−1 bar−1. In addition, compared with the traditional PMIA/PA, the introduction of Co-PIP nanomaterials as an interlayer enhanced the tensile strength at break (12 vs. 19 MPa) and elongation of the PMIA/Co-PIP/PA membrane (32.0% vs. 83.9%). Accordingly, the designed PMIA/Co-PIP/PA membrane has great potential in industrial separation applications for drug concentration and organic solvent recovery.