Boosting the performance of reverse osmosis membrane by macrocyclic molecule through interfacial coordination-driven strategy

Developing polyamide reverse osmosis (RO) membrane with superior permeability and salt rejection is highly desired for desalination. In this study, we propose an interfacial coordination-driven strategy to promote the incorporation of macrocyclic molecule into the polyamide layer and further improve the performance of RO membrane. To this end, the macrocyclic molecule Noria and transition metal salt Fe(acac)3 are added into the aqueous phase and organic phase respectively. During the interfacial polymerization (IP) reaction of m-phenylenediamine (MPD) with trimesoyl chloride (TMC), Fe3+ as electron acceptor would coordinate with the electron donor Noria to form Noria-Fe3+ complex at the aqueous-organic interface. This effectively promotes the diffusion of Noria and its further incorporation into the resulting polyamide layer. As a result, the RO membrane with Noria-Fe3+ exhibits closely packed band-like surface morphology, obviously different from the traditional leaf-like structure formed by MPD-TMC. Benefitting from the inner cavity of Noria, the permeance of RO membrane is significantly improved from 1.37 Lm−2h−1bar−1 to 3.87 Lm−2h−1 bar−1 at the optimal Noria and Fe(acac)3 concentrations of 0.1 wt%, while the NaCl rejection experiences little change from 98.8 % to 98.2 %. Besides, the flux decline ratio and flux recovery ratio of obtained RO membrane are 21 % and 85 % respectively in the bovine serum albumin fouling test. It exhibits more excellent anti-fouling ability than the nascent membrane due to the better hydrophilicity and smoother membrane surface. This simple strategy may pave a novel way for the application of other molecules with special structures as additives to fabricate high-performance RO membranes.