Functionalized polyamide/MIL-101/CNT membranes: A new platform for reverse osmosis desalination

Nowadays, reverse osmosis (RO) has proven to be the most effective membrane technology for water treatment due to continuous further development. In reverse osmosis, a semi-permeable membrane separates the water molecules from the impurities. Recent studies have shown that the surface properties of the support layer have a significant impact on improving the performance of thin film membranes. In this work, polyamide was used as a selective layer over a polysulfone support to promote interfacial polymerization and fabricate the membranes. Different loadings of metal-organic frameworks (MOFs, MIL-101) and multi-walled carbon nanotubes (MWCNTs) were incorporated into various unfunctionalized and functionalized membranes. The performance of the membranes has been enhanced by increasing both water flux and salt rejection. Among the membranes produced, the PA/MOF-CNTs-4 modified membrane showed the highest water flux, which at 33.30 L/m²-h at 15 bars, was about twice as high as that of the pure polyamide membrane (16.90 L/m²-h at 15 bars). Salt retention was also improved to over 96%. SEM analysis of the PA/MOF-CNTs-4 membrane showed increased hydrophobicity, lower surface roughness, and higher water contact angle values. Due to the hydrophobic nature of MWCNTs, these properties contributed to improved water flux while maintaining excellent salt retention. • A novel polyamide membrane was developed using MIL-101 MOFs and functionalized MWCNTs. • The PA/MOF-CNTs-4 membrane exhibited superior water flux (33.30 L/m²·h·bar). • Salt rejection exceeded 96% for NaCl and 97% for MgSO₄. • Enhanced surface hydrophilicity and uniform pore distribution were achieved. • Improved thermal stability and electrostatic surface charge contributed to high desalination performance.