Facile Cu-BTC surface modification of thin chitosan film coated polyethersulfone membranes with improved antifouling properties for sustainable removal of manganese

Loose nanofiltration membranes, which have a loose selective layer and desired surface charge, provide highwaterflux and significant retention of low molecular weight molecules. In this study, a thinfilm of copper (II)-benzene-1,3,5-tricarboxylate (Cu-BTC) clusters was anchored on the surface of a chitosan (CS)-coated poly-ethersulfone (PES) membrane to improve the surface properties as well as performance (permeability, heavymetal removal efficiency, and antifouling activity) of the membrane. Characterization techniques, such as FE-SEM, EDX, XPS and AFM, zeta potential and water contact-angle measurements, verified that Cu-BTC wassuccessfully anchored on the CS layer. The Cu-BTC/CS membrane exhibited higher surface hydrophilicity androughness compared to the pristine one. It also demonstrated a waterflux of 44 L m−2h−1and a manganeseremoval efficiency of 86%, while the membrane coated only with CS had an average waterflux of 39 L m−2h−1and a manganese removal efficiency of 78%. Compatibility and interfacial interactions between the Cu-BTCclusters and the CS layer were investigated using molecular dynamics (MD). MD simulations indicated that theCu-BTC clusters increased the affinity of the membrane for water molecules. The anchored Cu-BTC clusters alsoimproved the antibacterial activity of the membrane; the Cu-BTC/CS membrane inactivated 83% ofEscherichiacolibacteria, while the pristine CS membrane 47% of the bacteria. The Cu-BTC/CS membrane also demonstratedinteresting anti-fouling properties against both organic and biological foulants.